Archive for October, 2018

 

All-Vans Quality of Life Rollup – Mid 2018 to Now

Oct 14, 2018 in mikuvan, vantruck

I’ve had a very unexpected life problem lately.

Namely, all of my vans work too well.

(Okay, I mean, they now do). But still, even before the Great Engine Rebuild (Oh, Shit, Again!?) adventure of 2018, there was, in practice, nothing really going on with Mikuvan besides the engine being worn out and consuming oil. Vantruck, too, always started (begrudgingly so) but really has never quit once running, and has repeatedly made its way to New Jersey and New Hampshire and other New states….as well as Pennsylvania again, but we’ll get to that. It’s probably solely responsible for around 0.00002 degrees Celsius of global warming by now.

This is, honestly, rather unprecedented. So what’s someone like me to do now that he has two vehicles which, at first order approximation, start and run without trouble?

Make problems for myself.

Well, I mean, make incremental facility improvements and try to head off future issues… but then again, I said that shortly before changing my timing belts in the dark.

This post covers the smaller potato work that I’ve done on Mikuvan and vantruck roughly between May (when the place finally unfroze) and, like, last week or something. There’s nothing very revolutionary (thankfully!) and the beginning of cold weather* now will see a decline in work again. I also moved house – on purpose close by the shop – specifically to cut my commute to just a few minutes of walking, hence relieving Mikuvan of having to be dailied. This has been unfortunately going on since I left MIT in 2015, so being able to park it for days at a time means opening up more opportunties to execute longer term work on it again.

*i define cold weather as anything under 65 degrees

mikuvan

 

Some time last fall, Mikuvan began developing a clicking sound from the driveline somewhere in the back. It was a classic sound of a degrading universal joint. I’d bought replacements a long time ago, but didn’t feel the need to replace them just yet. At that time, it hadn’t progressed into any noticeable vibration or binding, and without any long trips on the horizon, I decided to just try and see what happens! I mean, worst case, it r/JRITSses itself somewhat or I’d need to redneck tow it to the shop if it got really bad.

Fast forward to spring, and the clicking had evolved into a somewhat noticeable vibration. Finally, the tipping point came after the 2-and-some week Battlebots Season 3 filming – in that time, something finally bound up completely, maybe from corrosion, and the vibration became much more intense to the point which highway use was questionable.

Alright, alright, I get the point. Time to unbolt the driveshaft at the differential input flange and slide it out.

Huh. Well I’m no….mechanical engineer, or something?…. but I’m pretty sure a universal joint like that shouldn’t just stay rigid on its own. It turns out that vibration is straight up the whole thing flexing the suspension parts and transmission/engine mount!

I’d never replaced driveshaft parts up to this point, so I spent a while watching Youtube videos on how to do it correctly and incorrectly. I ended up deciding to do it incorrectly using the Two Sockets Method, a close relative of the Three Seashells, I am told. This just means receiving the lower U-joint cup with a large socket like an impact wrench socket, and pressing the top downwards with a smaller one, in the absence of a dedicated pressing tool.

The first step either way was releasing the years-old retaining rings which had long rusted shut. I decided to go for total war and simply rip them out however I could, since the new joint parts came with clips anyway.

The gore that presented itself I was just a little unprepared for. I’d say that’s a rather r/JRITS universal joint indeed! The rubber seals were completely fried, probably from the immense heat generated from grinding metal rods around.

Here’s where the joint seized up and bunched up the rollers.

Hold on – I said there were “no long trips on the horizon”, right? Nah, this thing went to Atlanta and back in January. Through the Smoky Mountains, even!

I reused the Two Sockets Method to install the new joints. The ends of the U-joints were ever so slightly not parallel, which made the initial press alignment difficult, but it was not enough to affect it once things got under way.

The new joints came with some semblance of grease of unknown vintage inside, but I slathered the entire assembly inside and out before putting it back together. Here I am about to do the second stage install on the differential flange end.

And all finished!

I had a replacement ready for the transmission-side joint too, but it didn’t exhibit any binding or backlash and the seals looked healthy. So I just gave it an external grease slathering and cleaning for now – no need to replace it for the time being, since even though the Two Sockets Method worked fine, it was still a little painful.

It’s late May coming into June now, so the weather’s been warming up (finally) and I haven’t blown the engine up yet. I decided to address something that has always been lurking since I bought the thing, but never presented a problem, nor is it of guaranteed benefit if I messed with it.

I meanwhat else is new, right!?

 

I’m talking about Mikuvan’s secondary A/C condenser. It’s a little radiator that’s part of the dual air conditioning system – only equipped on the dual A/C models. It lives right in front of the passenger front tire, protected from all the spray and road grime and debris by….. like a 3″ tall mini-mudflap. This is to say it’s utterly useless and the whole thing is filled with rocks. The fan motor is long dead and bound up. I was in fact amazed it hadn’t rusted all away by now.

 

As long as I’ve had Mikuvan, the mini condenser fan has been loose and just jiggling under the motor. After cracking the assembly open, it fell right out. The hub was pretty mangled, but it was just a press-in steel insert and not bolted or splined or something.

I surmised that the first good rock that got flung into this thing probably jammed the fan and caused it to be broken off its hub, and from there, this condenser was basically useless. It’s positioned horizontally, so it really doesn’t even get any kind of directed airflow. Not without some kind of assisting duct or control surface, anyway.

The fan motor itself is a little cute 60W nameplate rated axial pancake motor, which seemed to have long ran out of life energy and could be barely turned by hand. Nevertheless, I kind of got the idea of what it has to be replaced by, so I went and did some shopping.

This is its replacement, a 10″ diameter miniature radiator fan from Amazon. I have to take a moment here to stop and praise the sheer ballsiness of Bezos’ magical elf workshop for making formerly very niche car products commoditized and straight up passing the Chinesium into the hands of consumers. This object is $40 and by my judgement quite well made with sharp mold lines (very sharp… ouch) and rigid feeling plastic with visible fiber-fill texture.

I was just going to pull the motor and fan rotor out and bolt it to the existing steel frame of the A/C condenser.

I was pleasantly surprised pulling the fan rotor off because I discovered that this motor was basically identical to the stock one, as in down to the mounting flange and everything. I take it this size-class of fan has just been a form factor staple for decades.

The mounting holes just lined up, but the new one is actually mirrored from the old one. The motor did need spacing off from its mounting bracket due to a different, more protruding rear bearing boss, so I used some spare Overhaul rubber shock mounts to give it that distance. It also gives the fan a little bit of flex so it isolates (what little it had) vibration.

Before mounting everything, I hit the fan mounting plate with a few coats of rust converter and then leftover clear-coat. This should keep it from dissolving away for a few years yet!

I spliced the connector from the old motor on and dropped everything in place. Really from the space available I could have well gone for a full 12″ fan, but this actually shouldn’t be drawing that much power anyway. It’s on a circuit that supported 4-5 amp draw to start with, so to try and stuff a 10+ amp full size blower motor on it might have other consequences in the electrical system.

When the A/C is turned on now, this fan runs with the system. It provided a noticeable improvement in the A/C system’s cooling ability at low speeds (in traffic/stopped) and in general on hotter days.

After Dragon Con this year, with the summer (a.k.a “the three or four weeks you can work on stuff outside”) coming to close and with no more long roadtrips on the horizon for real this time, I decided to address the ever-degrading paint work on the front. I now was in my new place nearby the shop, so I could leave stuff unfinished for multiple days without making one or the other white-collar millennial yuppie upset (I speak as if I’m not one at heart…)

The paint on the front of Mikuvan was ratty and rock-chipped when I bought it – and it sure hasn’t gotten better. It doesn’t help that the front is also nearly vertical, so it will take every piece of gravel (and every bug) head on.  I elected to go for just a repaint instead of also filling dents – it was more worth it to me to just protect the metal more than anything. That’s my general approach now with bodywork – make it not get shittier, and some day when (I’m sure) I sell the company for Bezos-class ca$h-out money, I’ll have everything done over correctly.

 

….right? Right?

I thought the front trim piece was double-sided taped on, but turns out it’s just held in by little snap rivets. I removed it and all of the headlight trim in order to inspect how much I’d have to do here. The plan is to mask off the black window highlights, give a fine sand over everything, use some high-build filler primer on select areas, and then blast the whole thing.

I didn’t invest in any color-matched paint or a spray gun or anything. This whole operation will be a rattlecan bomb with Dupli-Color Chrysler Bright White, the closest shade to what I assume it looked like new (and which has been on all my other questionable auto body endeavors).

Here we go! Masking was a job that took a while on its own, especially since I had to be very careful trimming the black highlights with a craft knife. I masked far enough around that I could go Banksy Overdrive.

I used some 180 grit sanding sponges and 220 grit sandpaper to roughen up the existing paint. Honestly, it’s so degraded that even 220 grit was very easily removing it to the OEM primer layer (as seen in a few spots). I cleaned everything during and afterwards with denatured alcohol.

It didn’t occur to me unti I was more than halfway through the filler primer job that….. it’s black colored. Oh boy, this will take quite a few coats of white to cover up now…. I mostly focused on blasting the extra-sanded areas and the deeper rock chips.

As can be seen, I also had a little too much fun with exhausting the initial few old/stale paint shots. If there’s one thing I’ve learned about spraypaints, it’s never use the first couple of seconds of paint, especially not after it’s been sitting a long time.

 

After the primer had dried, I went back over it with sandpaper in parts where I let it hang out a little too long and it produced some noticeable runs and areas of unevenness.

Then I went ahead and applied the first couple of color coats. I continued this process even as the sun started setting – and had to clean out another Autozone of the color I needed before continuing. I think about 9 or 10 passes of paint total went into it. You can’t spray regular spraypaint too thick at once, since it will run down a vertical surface, so I had to take multiple very light passes.

I let the color coat dry overnight and bake some in the morning sun, then made a few passes of gloss clear coat. I actually used a clearcoat advertised as an engine paint which had ceramic particles (allegedly!) in it; this I got some time ago for another project and had used on other smaller van sections. This stuff, whatever it contains, actually isn’t entirely clear in thick coats – the magic unicorn dust gives it a very, very faint bronze tint. This actually had the effect of color-matching the Bright White with the more weathered white factory paint, so it was a happy coincidence – but just watch out if you actually use it for real things.

In the afternoon, I began peeling off all the masking.

A few tiny runs and undermining of the masking tape here or there, but I consider it all good.

I gave the paint about a week to dry and cure fully before installing the badges again. The “Mitsubishi” logo came off some time in 2016, and I hung onto it. I got a new diamond badge off eBay about the same time, so I finally dug them back out and cleaned everything up.

To align the diamond badge, I looked up some photos of where they were originally.  It seems to either have the centroid horizontally aligned with the top edge of the headlight trim, or the bottom edge of the badge aligned with the same. I’m sure it depended on the year and how drunk the assembly workers were.

I decided to go for the “center aligned” version, so I made a guide with a horizontal solid strip of masking tape. From the center of that tape strip, I tore off a section and applied it again, lowered by the height of the bottom two diamonds. Then I marked off with a pen the middle of the distance between the headlight trims at that height. This gave me local geometric alignment to smash it on with some VHB.

The Mitsubishi text badge was applied much more haphazardly in a location that I thought looked like that it belonged.

At this point, Mikuvan is in a very stable plateau, which I hope I can maintain for a while. I no longer need to daily, and the powertrain is in excellent shape post-rebuild. I do need to get around to re-brushing the front A/C blower motor (…again), but that’s a very minor kibble.

The only additional bodywork I’d like to do (besides everything) is revisit the rear hatch glass, which was the very first rust repair I ever did 5 years ago. It’s been slowly coming apart the past few months and is now bubbled up some in spots. However, without a heated garage, and with further detrioration less likely to advance since it’s mostly parked indoors, I’ll put this off until next spring or later.

Everything else that is/was rusty has been paved over in thick dosings of what I call “Eastwood Goo” – you’re supposed to fill body panels with that stuff, not use it externally. Believe me, I’ve considered making look intentional and doing both sides with a clear masking line.

And now, back to the only-partially white elephant  of….

vantruck

Sorry, did I say it was running well and had no problems and had never left me stranded?

I dunno what BattleBots did this year, but my vans weren’t much fans of me when I got back. Maybe it’s because they got jealous, or maybe all of my equipment actually talk to each other and know I failed at winning miserably, so they’re just all piling on now while I’m down. Either way, one day soon after my return, I went to pick up a few shipments.

All was great going in! Then, when I tried to leave…. nothing. I could hear the starter clicking, but it wasn’t doing much starting. After a classic “hammer on the starter” attempt, it gave maybe one half-assed crank, but it wasn’t enough.

Okay, okay, I get it. You guys really like riding on tow trucks and U-hauls. Vantruck got this habit from Mikuvan, who I’ve had to trailer home more times than I’d like to admit to my friends in order to avoid their judgemental Facebook comments. Something about older siblings being bad influences….

 

I figure the starter is original, since it looks like THAT.

After dealing with a snowflakey, rare Japanese van for ages, it was actually a relief to handle something American. Parts for domestic brands are SO. CHEAP. I’m guessing this is how old muscle car people survive – the lineage of parts for American makes is just so extensive. What do you mean Autozone had something just on the shelf? Such luxury! I had this job done the SAME DAY.

The starter is retained by only 2 bolts, so this job was very quick and painless. Quite possibly the ONLY part which is quick and painless to do on a 3rd-generation Econoline, as far as I can tell.

I took the old starter apart afterwards because curiousity got the better of me. Those are some very stumpy and worn brushes indeed. What didn’t make sense to me still was just how fast the cliff came – typically you can nurse a worn-out brushed motor for quite a while by hammering at it, which has the effect of making the brushes temporarily contact the commutator again. I got maybe another few rotations out of it, not enough to turn the engine over even once. Oh well…

And yes, I absolutely did return it to Autozone as a core in this condition. They took it.

Hey, it saves your rebuild house some labor time!

The interesting thing is, I used to have two of this kind of Ford truck starter. In early high school, when I went to a junkyard the first time to the utter horror of my parents who were desperately trying to keep me on the path of being a doctor or something, there were just two of them lying on the ground next to a bunch of other pre-pulled parts. I got them both for something stupid like $20. I didn’t know what they were at the time (only that they ended up not being good for robots), and eventually they were lost to the cruft seas of time and moving house, given away or left behind. The last positive memory I have of them was in 2006 or so when I finally had to reorganize my every-growing cruft stash.

This just confirms my belief that you shouldn’t ever throw anything away, ever. Because I could have REALLY used them just now.

Whatever, it starts again. Here’s a picture of the bottom pan of a Gear Vendors overdrive unit – I wanted to stop it from dribbling gear oil slowly since the gasket was damaged. I scraped off the existing one (the green junk) and put on a new one I ordered from GV directly. The only trick to this I encountered was the oil pickup tube didn’t want to stay in the upper half of the unit, not even with a new o-ring. So you kinda have to place it just right in the tray and wiggle it in as a pilot alignment feature before putting the oil pan bolts in. There’s no other retention for it I can see.

By now, it was late May, and Vantruck’s true calling of being an internet meme was well under way.

Yes, that is indeed Alex and myself at the first Regular Car Reviews double-review. If you haven’t seen it by now…

….don’t click on it unless you have headphones, have very understanding bosses, or own the damn company.

This was a cool experience. I’d been following RCR for a while now, and so to be on the show was an exciting opportunity. We presented the idea of Double Vantruck Party to him some time in April, after BattleBots was all done. The whole filming was a one-day affair – meet in the morning, take some sweet video, and then roll home in the evening. I’ll say that Mr. Regular really opens up personality-wise after a few beers. He’s otherwise a very unassuming person, someone you wouldn’t associate with the #1 source of brown on the Internet.

 

Some time in June, I was trying to change the alternator belt when I realized that there’s just way, way too much going on in the engine bay. A lot of the mess is the 1980s California smog package. It has two air injection pumps that run off the alternator belt, about 2 miles of random hoses and vacuum lines connected to a few check valves and delay valves and thermally-triggered valves and blah blah blah GET THE FUCK OUT OF MY HOUSE

All of it. Out and away.

I wasn’t merely doing this for the purpose of easier belt changing, but also I wanted to get to the root of the Weird Idle issue that has plagued Vantruck since forever, at least since the installation of the EFI rig.

Basically what would happen is, upon reaching warm idle, the exhaust AFR becomes very rich on the order of 12.5 to 13, and the EFI unit tries to trim down as much as it can, but it’s not enough. Some times it feels like it’s missing a cylinder. It clears up if you rev at all, and it’s never misfired or exhibited bad behavior on the highway. It also doesn’t happen when it’s cold started or just warming up.

This led me to believe that there was a remnant temperature-triggered emissions device which, no longer needed or with its connected system removed, was now simply causing problems. I removed and plugged every single vacuum fitting I could find, and also plugged/capped the air injection manifolds.

Jokes about global warming aside, when it’s operating outside of the “Weird Idle”, the AFR is maintained very tightly. I strongly think the EFI retrofit makes the emissions more controlled than any analog vacuum cleaner contraption ever could.  They did the best with what they had, now it’s time for it to disappear.

I kept all of this gadgetry in a box – if you want it some some reason, let me know!

 

It’s actually reasonable in there now!  I always thought this engine bay was never designed to fit the big-block series engines and they just smashed them in there because marketing said they had to.

In the same session, I also retimed the distributor slightly. I figured that one of my Weird Idle causes could be too low initial timing – the FITech dashboard screen shows me the manifold vacuum, and it was always suspiciously low in the Weird Idle state, often on the cusp of around -15 to -16 inHg, whereas The Internet suggests that a higher (-18 to -20) value is more common.  So either way, I decided to double check.

By the way, if you’ve know me recently, you might have heard me say that “X or Y is the Distributor Wrench of Z”. This is because it took me THREE. HOURS. of dismantling things to get to a point where I can wrestle some abomination of a crows-foot wrench, a universal joint, some kind of socket extension, and a wobble-drive to get to the stupid bolt that locks the rotation of this thing.

Then I found out they make a single-purpose U-shaped bent wrench, JUST for this purpose. It has no reason to exist besides compensating for shitty engineering and cost-cutting. It is, truly, the Distributor Wrench of distributor wrenches.

This is not okay. It’s the literal opposite of okay.

This was the first time I got to play with my own timing light and know what it meant. There was a timing light someone busted out when the initial exorcism of Mikuvan was happening, but my only conception of timing at that point was about stator flux and that motor sure didnt look very electric.

I verified that the base timing of the distributor was only 4 degrees – even lower than the 8 degrees indicated in the manual, and far lower than the 12-16 degrees The Internet™ claimed that Ford big-blocks liked. Feeling edgy, I set it to 16 degrees. Unfortunately, it had little to no apparent effect on the Weird Idle.

Whatever the root cause of the Weird Idle might be, it wasn’t causing any problems really besides making people judge me while in traffic – but I’m used to that anyway.

Among other adventures, I went on a van assist mission to work on Cassandra’s van in New York. We had a number of things to go over during the day, and I figured I’d bring Vantruck for its towing capacity juuuuuuuuuuuust in case.

This trip taught me that all American full-size vans are abominations of packaging and manufacturing, not just mine. They were never made to be serviced – you were supposed to buy them for your contractor business, drive them for like 40 or 50,000 miles, then get a new one. Problems wouldn’t really come up in that time interval, and when they do, you just junk it and start anew. This is how American van design hasn’t really changed since the 1970s. Even a modern final-generation E350 shares underpinnings with this generation, and GM has been making the same van now since what, 1994?

So what’s on the horizon for Vantruck now?

I’ve been doing some research on how you remedy Ford rain gutter rust, and the answer is “You Don’t”. Not without custom metal fab, and definitely not cutting these off because that apparently makes the whole roof just pop off, because the rain gutters double as the pinch-weld which attaches the roof to the sides. Gee, thanks Ford.

I have a few bright ideas about cutting them off just enough to weld on some strip patches, and have talked to two or three auto body places regarding it (and to have them on standby for when I inevitably fuck up).

This work is kind of indeterminately scheduled right now – I’d like to remedy this entirely before trying to paint it or make any additional restoration fixes.  For now, the rust is arrested with converter compound and clear-coated over, so this (along with 2 or 3 other patches on the roof) at least won’t get much worse. Realistically, the fleet is in good running condition day-to-day so I will likely back off on Van Stuff for the next few months.

However, I’ve decided that Vantruck will be my target for more extensive buildout in the future in terms of restoration and “enhancements”. It goes back to what I said earlier about Mikuvan being just too much of a snowflake; parts beyond powertrain are difficult to find if I mess something up, or expensive if I do find them since they often need to come from overseas where the platform is still being supported. Vantruck – while “special” in its own way, is still an older American truck built like a Lego set. 3rd-generation Econolines show up on Craigslist all the time for cheap. Parts are everywhere. I feel way less bad diving into it and modifying it for this reason.

As for what plans exactly, I’m not sure yet. I definitely want to repaint this thing fully white with black accents much like Mikuvan still; as much as the three-tone brown-on-Brown-on-b r o w n is endearing, I’d prefer a more consistent look – most people pay good money to have three-tone paint, but I get it for free! It’s brown, less brown, and white!

Recall the original Vantruck repaint concept I posted way back when:

I’d like to make some very mild changes to this based on inspiration I’ve seen from other trucks, but it will resemble this at a high level. It replicates the window blackout highlights that Mikuvan has, which I do like.

I’ve also been playing around in Solidworks with other “additions”:

That is a very idealistic mockup of what I call the “Bovine Interdiction System”, or a cowcatcher/bullbar setup. The inspiration was largely from semi-tractors with the broad chromed front bumpers, which I learned were called “Texas Square” bumpers. It also turns out that the elaborate marker light arrangements on some trucks and trailers are called “Chicken Lights“.

It would then seem, at first approximation, that truckers have as many meme-names for thing as I do. Because I sure as hell didn’t get any useful search results for “those lights that truckers put all over their running boards and trailer sides”.

Anyways, I’m highly unlikely to build that monstrosity, but its design will probably evolve. I would like front and rear upgrades to this thing eventually, and paying $1000+ for a commercial brodozer bumper is just unfathomable in my mind (Plus literally nobody makes them for 3rd-generation E-series vans, because why would you.)

In general, it gives an idea of the direction I want to pull this thing, which is “mildly brodozer” in aesthetic without sacrificing usability; I’m not inclined to lift it beyond the point of usefulness in towing the company’s equipment trailer, but a bed-mounted toolbox would be nice, for instance.

Roll Cake 3: The Build!

Oct 09, 2018 in Bots, Roll Cake

It’s time to put a robot together! This post covers the entire fabrication of Roll Cake 3 in the week or so before Dragon Con. The goal of the bot was primarily to try and drive better with an indirect drive brushless setup and also further refine the packaging and action of the flipper linkage. Will it do anything?! Hell if I know, that’s the fun part to discover!

Even as I was finishing up the design the weeks prior, I was pregaming getting parts. Basically as soon as I determined the C2028 motor would fit in the triangle behind the wheels, I went ahead and ordered 3 more since I only had 1 to start with.

I also ordered these OMG THE MOST ADORABLE LITTLE 0.8 MODULE PINIONS EVER THAT COST WAY TOO MUCH MONEY from SDP-SI. I had to go solely by what they sold for 2mm bores in these gears. I wanted an 8-tooth gear to achieve the 8:1 reduction I wanted to get with the wheel gears, but they only sold the 8-tooth with a 3mm bore. So my drivetrain reduction is going to end up more like 10.6:1, which is fine by me – the bot will be too fast no matter what.

The problem with these tiny gears? The 2mm bores were slip-fit, not press-fit! Certainly irritating, but not the end of the world. Already noted for a revision in the future is maybe transitioning to R/C model pinions, such as R/C car transmissions. Those typically come in 3mm or 1/8″ bores.

I used Loctite 609 to stuff the pinions onto the motors in the end – I tried to silver solder one of them to little success – while I’ve managed to solder or braze pinions before, it seems that the steel they used in this motor shaft is an unusually high chromium grade which didn’t want to take with any flux I had on hand.

That was before I melted the pinion completely. Ah well.

Completed drive motors refitted with their shafts, which was a minor press fit job. I also replaced the stock stainless steel prop-saver screws with drilled-out and re-tapped #4-40 set screws. Another minor point of trouble with these motors is that due to their length and the small shaft diameter, it was hard to get these things to spin entirely true again after resintalling the shaft. A shorter motor (more pancakey) will resolve this.

I put the gearbox parts on print in Onyx as soon as I finished the bot design. The two ring gears and main cam linkage (sticking off to the left) have hoops of carbon fiber; everything else just derives strength from a bunch of perimeters. On the very left are the two connecting links between the cam link and the arm. I also made two first-pass prints of the drive wheels, seen here with O-rings.

Frame parts freshly done and needing cleaning. I’d say this is the only irritating part of doing unibody bots for me – picking the support out of difficult crevices. There’s certainly orientations that I can print in for minimal support, but they sacrifice immense strength in the part itself.  Both of these frame halves were printed in the orientation shown to give continuous loops in the XY (flat) plane.

In Roll Cakes past, I’ve actually taken to making fiber laps around the frame in this orientation, but with the more recent-ish changes to Eiger, you can change the perimeter and fill with more flexibility such that I just stack on the perimeters.

Otherwise, pull out some injection-molded part design – relatively constant wall thickness and smooth transitions if you can manage it, using ribs and cavities versus just solid massive areas, etc. However, my habit with 3D printed frames is leaving a few bulky areas up front such that they remain somewhat hollow – this acts as a very effective energy absorbing medium. For instance, basically the front inch or so if this bot is solid in the model, which means it’s perimeter plus non-solid infill in real life.

 

Drive motor installed with some test fitting done on the wheels here. Most of the hardware on Roll Cake 3 is specified as plastic or metal threadforming screws. If you get really fancy, people like using heat-set or tanged flanged inserts in MarkForged prints. However, I like my expediency, so some fat #10 tri-lobe threads will do to hold the wheels on.

Here’s the final drive fitup. The 0.8 Mod (32-ish DP) gears printed perfectly fine. In my experience, this is about as small as you can print reliably because the nozzle diameter still is small enough to go in and out of tooth tips profiles.

 

Both sides now fitted with drives. The front binding screw is shown sticking out here.

…and now joined together. Already, this thing is way more rigid than last time side to side. Hell, I might as well just ditch the flipper and make it a pure drum :v

The screw length needed to do this assembly were compromises with what I had on hand, so the bot dimensions shifted a little to accommodate them. Roll Cake is in fact not a perfect circle, but slightly squished inwards to yield the rough double-D-flat shape.

I slid in the trigger piece (which has a cutout for the servo arm) first, then I slid the servo into the DMs.

Alrighty, all the easy 3D printed stuff is assembled now. I still have to make a drum and motor, so off to Taki-chan we go!

(Also, check out the waterjet-cut feeder wedges made from leftover Hardox 450 from Overhaul!)

First order of business: separate the motor magnet ring so I can stuff it inside the drum. This can’t always happen cleanly, depending on the motor’s construction. The Donkeys have a single-piece stamped steel rotor, so I simply chucked the shaft in and very carefully parted at the outside corner where the magnet ring area joins the endcap.

With a motor that has an aluminum endcap, it’s often scarier since the parts can separate and self-destruct.  Luckily, this operation went very smoothly with higher speed and gentler feed to keep the forces on the rotor low.

Next up is to rough the drum shape. Most of this was easy, but I had to make the dual-disk shape, so I had to cut a valley in the middle. I just went with multiple staggered parting tool cuts to nearly the right shape, then very very carefully and gently made really shallow passes side to side to clean the profile up. Very gentle. These insert tools really should not be taking any side forces. To do this without wallhacking, I’d have gotten a single wider custom-ground HSS tool or something.

 

Then I bored the drum interior. There’s three stepped diameters – one for the ring bearing, then the magnet ring of the motor, then the “doesn’t matter” internal diameter. For the output side “bearing-stem-gear” I just did a straight drill to 12.0mm since it did not have to be that precise.

Next up: stator holder.

With the aluminum parts roughed out, I decided to make the one odd piece, which is the gear-on-a-stick that will carry the drum energy into the gearbox. This was a pretty easy turning job, but remember, it’s also the other bearing of the whole drum. The center bore, then, had to be 1. a clearance, but not by much, and 2. very clean and precise.

I actually went out and bought a 8mm-plus-0.001″ …. yes, this exists in America…. reamer to make this bore. You read that correctly – it’s a 0.3159″ reamer.

The gear gets a cylindrical boss on both ends eventually. After I finished both sides, I actually had to take a wire brush on an angle grinder to it in order to deburr the gear tooth edges – there were many little burrs and swarf hanging on which would have prevented the gear mate from working.

Parts in the midst of preparation! The stator bore has been drilled and the stem gear keyed on the top surface seen.

Throwing it together for a quick test fit! Here’s where it’s clearly visible that the stem gear skewers the cam ring gear and the cam linkage.

The next task was to drill the tooth holes in the aluminum drum body. I no longer have my old indexing head that made guest appearances in many of my undergrad builds, since I donated it to MITERS years ago. So to make sure I’m able to place the teeth 180 degrees apart, I milled a very shallow flat, then rotated it to sit on that flat, then milled another one.

This ensured I can drill and tap both sides with relatively equal precision. The teeth are just 3/8″-16 alloy cap screws, so they thread right in.

After the drum body was fully fnished, I broached it for a 3mm key – the stem gear is shown here mated to it. The magnet ring pressed into position without much trouble.

Unfortunately, I didn’t have time to make a new set of cluster gears, so I had to take them out of Roll Cake 2. Sad, since I wanted to keep that bot fully operational if I could!

The thought has crossed my mind of hiring out a whole basket of little cluster gears to be made if I’m going to keep evolving this bot.

The catch with these compound planetary cluster-fuck gears is that they have to be assembled at specific angle, or phasing, since there’s a hard relationship between the number of gears and the relative tooth counts. I scratched alignment marks into them when I first put them together for Roll Cake 1, and still use them for reference.

The gray goop I have dripped all over the assembly is liquid bike chain wax. I’ve been avoiding using petroleum-based lubricants like common greases because I don’t want to risk damaging the nylon-based Onyx material from the solvent action. Grease would also add immensely to the no-load drag of the gearbox, which is already a lot happening for a weapon drive.

The planet carrier installs easily after the gears are properly phased in place. It looks from here that there’s a ton of stuff going on, but I guarantee you this is not the case :v

As I mentioned in the design post, this carrier now has its own bearing to support itself. This is a pretty odd (but still apparently some kind of standard) 8mm bore, 14mm OD bearing – very low profile.

The drum drops into place from the front. The service order of this thing is a little suboptimal – to service the drum, I have to disconnect it from the folding linkage, but the central pivot bolt doesn’t rise up out of the body’s central cavity…. so really I have to undo the bottom linkage anchor (those three screws in a row from the CAD model) first, then remove the arm hinge. At least I made sure to make it all serviceable with at most 2 tools this time!

After the drum and arm are mounted, it was time for electrical dressup.

Along with the feeder claws, I cut another insectweight top plate set out of this piece of 1/32″ blue spring steel shim. I bought like 10 feet of this shim some time during undergrad, and have slowly been generating robots out of it since. This thing made its first appearance all the way back in 2009 with Pop Quiz’s rebuild! I’m now on the very last 8-10″ of it after Roll Cake’s parts are accounted for!

For better or worse, picking the parts out of the mother material was one of the last things I did before absconding on  3-day long slow meander down to Atlanta for Dragon Con. On the way, I hit up the Blue Ridge Parkway, like I promised myself I’d do. I only brought Roll Cake and its suite of service tools and a box of parts I think I’d need (mostly electronics), and Overhaul for display. This Dragon Con was going to be a pretty clean show instead of scrambling to take care of a few robots – the reason for this is I was pretty much solo this time, as there was a lot of bad timing involved for the various startups and schemes my friends and I are all involved in.

So what’s better than finishing your bot in the airBnB room when you got into town? Not all that much. I pre-gamed some of the electronics wiring (like battery leads and the like) before I left, so installing the two drive ESCs (AfroESC 12A) and weapon ESC (Spider ZTW 40A with SimonK) was a quick affair. I was able to drive Roll Cake around on the floor to get a gauge for its handling – which is much, MUCH improved over the hub motor drive version.

It’s very quick, but much more maneuverably so than Roll Cake 2, which tended to twitch everywhere. I swear the twitching is better than it was! At least now I could predictably send the bot places, which is an improvement over before!

The flipper geartrain was very tight, though, because I hadn’t had the chance to run it fully in up until that point. It would take several minutes of just running the drum at maximum speed and also a while of keeping the linkage engaged to wear everything in.

Here’s Roll Cake 3 fully buttoned up!

And shown with the flipper linkage at full height. In the next episode, hopefully you’ll get to hear about what it did, if anything!

The Roll Cake that Won’t Die: Roll Cake 3.0

Oct 03, 2018 in Bots, Roll Cake

I still like to pretend that I build robots here on this website! So in preparation for the fall round of events I like to go to (Dragon Con, Franklin, and any MassDestructions we try to hold) I decided in August to try and keep making progress on my recent persistent itch – Roll Cake.

Roll Cake had never “done well” – really done much of anything – at a competition since my main focus each and every time is kind of getting the vision of the bot finally in physical form. Remember its origin story and how I’ve been meaning to build a kinetic flipper for years, but never quite gotten around to it. It’s a robot built around a vision of a exterior shape and layout I came up with more than a decade ago, so it’s almost suboptimal on purpose.

Roll Cake 1 was sort of the grand puking of the idea in which nothing really worked. Roll Cake 2 made the mechanism shine, but still had a deficient drive due to sacrificing drivability for space conservation. My goal with Roll Cake 3 was to improve its driveability while making the weapon much more aggressive; Roll Cake 2 had a rather light drum/flywheel being belt-driven by an undersized motor that frequently overheated or shed belts.

The story of Roll Cake 3 actually dates back to not long after the previous Franklin Institute event, to which I brought it in order to talk about Alternative Flippers with a few other builders – it didn’t compete.

After mulling life on the return trip, I began the design by throwing some parts at the version 2 frame CAD and seeing what stuck. The principal design goals for V3 were:

  1. Moving to indirect drive on the wheels – the direct drive, while workable, was obviously still not very controllable. I figured a very small motor could tuck in the wasted volume (there’s a lot of wasted volume on Roll Cake) behind the wheels and could get me a considerable reduction just with open spur gears alone.
  2. Moving, on the contrary, to DIRECT drive on the weapon. The little 22mm outrunner just wasn’t enough to drive the whole geartrain continuously while also spinning a weapon. I could, with the increased drum interior volume, actually have a beetle-class weapon (so, you know, if the flipper plan just falls off a quarry cliff and explodes, it will at least be just a spinner)
  3. And lastly, moving to a dead shaft instead of V2′s live weapon shaft. This was more or less driven by going to a hub motor weapon. I’ll talk more about the Implications of this design change a little further down.

I had a Turnigy  C2028 motor model already, so I used it as a modeling guide for the positioning of the motor. I placed a Stance Stance Revolution motor, a Multistar pancake outrunner, in as a placeholder for the drum motor, though I wasn’t keen on using it. A motor that was a little more primitive seemed a better fit for the weapon.

To explore the space, I ordered some of the cheapest, shittiest motors you could buy on Hobbyking in the 35 to 45mm size range:

I love Hobbyking for having the sheer gall to sell you a motor that doesn’t have bearings. The Donkey line has bronze bushings and is seemingly made precisely to be the parts-recycling minimum viable products they are. A lot of builders have used them as foundations for their own weapon drives, and so will I!

I miss making motors, so this will be a fun distraction too.

I ended up selecting the Donkey 3511 motor for its stator size, but more importantly, the 12mm stator bore. The blue and silver “DT700″ motor had a thicker stator that I liked, but sadly only had an 8mm bore.

Why the bigger bore? I said earlier I was intending to move to a dead shaft for this iteration. Roll Cake historically has been rather tenuously held together side to side, with relatively small cross sections of material in the center due to the need to fit the flipper linkage. Moving to a dead shaft design allows me to use the shaft as an additional structural member of sorts up front.

The downside is I’d have to make a stator hub that the shaft presses into, and to do that, the stator needs to have a larger hole in the middle. I was intending on keeping the 8mm steel shaft that Roll Cakes have used for time immemorial (as in, literally the same one from v1 and v2), so that meant the stator needed at minimum, say, a 10mm center hole.

I pulled my usual motor designing tricks of making a hub for the stator to mount on, upon which a tpye 68xx ring bearing fits over. I sized this for a 6806 bearing, which has a 30mm bore. It’s a design balance between clearing shaft and wires versus simply being overly large and heavier.

I next generated a rough drum weapon shape that’s hollowed out in the middle. All of the dimensions and spacings were adjustable at this point – the final weapon would be a different width entierly. This just gets me something to start throwing into the CAD model so I can do the fitment of the gearset.

The teeth are, in typical beetle fashion, some big countersunk alloy steel cap screws.

With an eye for weight, I made some parametric adjustable cuts into the drum to turn it into more of a ‘dual disc’ configuration not unlike Witch Doctor and Hypershock. The final drum weight is tuned by just making the cuts smaller or larger.

Next up was the magical Roll Cake gearbox. I made some design changes to make it up to 1/4″ narrower to make the weapon itself occupy more of the front width. The clutch ring now has a single tooth and no longer its own outer support bearing – instead, it simply has a smooth shoulder inside to gently ride on the planet carrier. The carrier itself will have a 8mm thin-section bearing bored into it instead. There will be some extra friction from the technically bearing-less clutch ring, but the much more OP drum should more than make up for it.  I also got rid of an equivalent support bearing on the offset cam ring and it now only has a single bearing also in the center.

To pass power from the drum into the gearbox via the now dead shaft, I had to do something rather unconventional. There is now a lot of stuff going on here, so bear with me….

The distal endcap of the drum (opposite the motor end) is bored out to 12mm and has a key broached in it. A stem gear with a 8mm clearance bore has a keyway milled in one end and is inserted into the drum endcap with a key. The gear’s stem is 12mm OD and passes through the 12mm support bearing of the offset cam ring, and both transmits rotational torque and supports impact loads from the drum.

There is no “bearing” inside the stem gear in the conventional sense – there is only reamed steel on polished hardened steel with some oil in between.  Hey, if there’s one thing I learned from begrudgingly rebuilding an engine, it’s that steel on steel with a bit of oil in between is how every car works. What could go wrong!?

I knew going in I was betting a lot on this… technically a fluid bearing, but whatever…. working out. The friction would be higher than a ball bearing by far, but I was going to bank on the length of engagement making up for it with a light pressure resulting from the contact area.

Anyways, the gear end of the stem gear interfaces with the existing split-planetary gearbox and makes the thing go up and down.

One of the biggest challenges of Roll Cake has always been where to put the battery. When you scale robots down, you inevitably hit a “component Planck Length” of sorts – essentially, at some scale of robotting, the parts stop getting usably smaller. For me, the prismatic battery has always been troublesome for packaging inside a wedge-shaped robot. I played around with several methods, such as this one placing the battery forward and vertical…

…and including the unpalatable approach of splitting the battery up into two smaller ones. I really didn’t want to deal with the extra wiring and now squeezing on space for other components.

But one night I had a moment of come-to-Plastic-Jesus clarity – perhaps it is a reasonable compromise (it is – there ain’t no Perhaps, I’m just stubborn) to ditch the notion that the flipper has to span the whole width of the bot. At this point in the bot’s evolution, I should be thinking in terms of what makes the design work and what it actually needs, versus still trying to stick to my vision of “robot go flap-flap”.

In mulling over the compromise for the arm design, I also included a mockup of the new wheels, which will have a spur gear included on them to mate with a pinion on the motor.  I ended up just rolling with the C2028 motor and ordered a few from Hobbyking. Optimal? Maybe not. Fits back there and in stock? Hell yeah!

I decided to keep the battery arrangement shown – where the battery is placed widthwise in the bot, leaving the left half or so open to be used for the flipper linkage. This suddenly freed up a WHOLE LOT of volume inside the bot, and it was honestly a relief.

Before I went further with that design, I actually backed up and basically started over on another thought in my head about the design. There’s technically nothing stating Roll Cake had to be round. In fact, V1 was not round. Having the corners back could result in the difference between fitting in the battery vertically versus not, so I tried generating a square (chamfered octagon, I suppose) version of the frame to see if that was profitable.

Admittedly I did get pretty far along here – I found a vertical cavity for the battery and even was able to make space for mounting the drum motor. There wasn’t really anything preventing me from going with this design.

What swung me back the other direction was actually the sheer amount of usable space opened by repositioning the battery in the round design. I did want a Roll Cake in which trying to injection-mold ESCs and hyraulic press wires inside wasn’t even going to be an issue. From there, with an ideally working bot, I would make space optimizations as needed.

Well that does it for me. I returned to the round design and began cutting out cavities for everything. There’s gratuitous volume now to put things, and almost makes me wonder if Roll Cake could be a little smaller. However, for now, the final diameter was driven by giving the most space to the drive wheels and batteries while retaining an acceptable arm width that didn’t reduce it to just a stick.

Adding internal boss features to support the drum hub and drive motors now. I also made a crossing retainer for the battery – it sits in a neat little cavity and is prevented from bouncing around by the low wall and the eventual top plate. The geometry for the trigger pin is also taking shape.

Inside the left half of the bot, I made more space-filling features to mount the trigger servo. The dimensions did require cutting a hole of sorts in the underside to clear the servo cable. I moved the servo up as far as I thought was reasonable while still keeping the trigger pin on a radial path into the clutch ring gear.

Smaller but important features are now rolled up including the integrated wheel pegs and the arm pivot. The wheel pegs were going to be a machined piece, but gradually became so short there was no point in machining a part and using a mechanical attachment method. Instead, just printing the peg would do!

Notice how the bottom of the peg has a flat on it – to counteract the messy nature of homogenous-material support lattices in 3D printing which never really prints bottom-sides cleanly, I just made the peg a D-flat to give a single flat surface for the support to finish and the part to build. The eccentricity potential of the wheel from the bearing being on an incomplete circle is going to be negligible; worst case I’ll stuff a shim into the gap.

I put the arm pivot at the very front tip of the bot to make the arm as long as possible in order to get free height at the flipping end. This constraint would drive the arm shape and the placement of the linkages.

I made a first approximation of the arm after that. It had to start out higher than the bot’s upper slope surface in order to clear the cam and ring gears, which is why there’s a mild kink in it. You can see the cam ring passing through the arm here – I used this as a guide to make a cut that was just barely enough to clear it.

From there, it was relatively easy to make the linkage by fixing the cam linkage centered in the bot and fixing the arm in the lowered position. The lower anchor is a simple pin joint I modeled on the backside of the center crossing span of the bot, so all I really needed to do is adjust lengths and the position of the pin joint on the arm itself.

I tuned the linkage lengths to give me in the end around 4″ of rise. The end driving constraint was not hitting the crossing span in the middle when extended, but also when folded, not closing more than about 60 included degrees (or 30 per side measured from the centered cam link as a baseline).

At that point, which is my mental cutoff for “sensible linkage”, the orthogonal loading force from pulling the linkage open is twice the actual opening force, and just gets worse as you collapse the linkage more.

(This, kids, is why your elaborate scissor lifts never work in 2.007…. wait until you take 2.12 and understand the Jacobian matrix)

 

Here is that “JUST BARELY” cut I talked about – when the cam’s coming up, there’s only a few thousands of an inch of clearance as the arm goes up.

In real life, as I found out, the slop in the system actually made it such that the cam lifting shoved the arm upwards, helping the linkage get started out of the folded position. Sci………ence?

As a matter of habit when designing the smaller bots, I began adding hardware to make things more realistic for weight. On a bot that’s tight in space selectively like Roll Cake, I also wanted a sense of where fastener heads were going to go. So it turns out McMaster actually has intricately-cut models of their shitty sheet metal screws for download. I didn’t even know shitty sheet metal screws were 3D modeled, really. Either way, it was handy to see how much fastener head you actually need to clear.

The arm and linkages also get their dose of “Real-ification” by the addition of shoulder screws and properly sized counterbores, thru-holes, and tapped holes.

The linkage length allowed me to finally add one feature that Roll Cakes Past have never ever had: a rear structural link. There was enough leftover space to put a crossing span in the back with a bolt to tie it together! This might be the most structurally sound Roll Cake yet.

Space was tight enough that I needed to put the bolt model in and make sure I could still tighten a nut. The length of the righthand cavity was adjusted a little bit to be just barely longer than the bolt, so I can, you know, actually install it.

The three holes in a row above the rear crossing span? It’s a removable piece, serviced from the rear of the bot, so I can install and uninstall the arm linkage.

It’s a little hard to see what’s going on here. This is a counterbored, hidden cross screw which holds the front half of the bot together. It’s installable from the outside by squishing it past the O-rings in the wheels. You’d otherwise barely know it’s there!

This might be a better view of where it goes. It is sunk about an inch into the right hand (here, left side) half of the bot before the thread diameter begins, in order to put that much plastic in compression first.

I moved onto making some kibbles and bits for the bot – here are two little feeder fangs to try and get under someone and make sure the drum gets first punch. They’ll be waterjet-cut from some kind of leftover steel.

We’re getting awfully close with the CAD now. I took care of some more last details, such as the tiny half-round ears for if the bot gets flipped over to prevent the drum from hitting the ground. While Roll Cake can obviously drive upside down, the double-sided flipper was deprecated post v1, so it still has an “up” side. Maybe one day I will try bringing the double-sided flipper back.

I then made wire passthroughs and filleted corners and broke edges. This is the now-complete “unibody” frame.

I took snapshots of the side cavities and traced them in order to generate conforming top plates. The hole locations were patterned where I could and kind of freelanced where I couldn’t, at a fixed distance from the nearest profile curve.

To actually make the bot, the monolithic model had to split into three pieces – the two halves, plus a drum axle retainer for the non-motor side. I generated cutting surfaces for this operation. The split is not linear, but has a jog in the middle to accommodate convenient locations to begin and end the frame profile.

The cover plates are modeled from the sketch drawings individually. I suppressed the monolithic body and  imported all of the cut pieces and properly constrained them in order to yield the multi-piece modeled frame.

So that does it for Roll Cake 3′s design. In the next episode, I have to actually build the damn thing!