Archive for May, 2017

 

Reassembling a Bridgeport J-head with Uncle Charles! And More About Hooking Up Your Annoyingly Chinese VFD

May 26, 2017 in Reference Posts, Shop Ninja

You know what? I’m tired of having sweet-ass machinery sitting around not hooked up. Last time in “Charles takes forever to set up his own shop because he’s sick of setting up shops”, I did some battle with a generic Chinese VFD and completed what the damn factory couldn’t be buggered to by adding the dynamic braking components.

Though Bridget ( <3 ) ran since then, there were some issues. The spindle brake was so worn it was difficult to change tools, and the head made the “Bridgeport Clack” from the high/low speed dog clutch being worn. The motor’s V-belt was also severely worn. I wanted to tear it down for a rebuild of sorts, so I spent a little while watching “How to rebuild a Bridgeport head” videos. I decided that all of these videos sucked, and that I was really only interested in repairing the brake and replacing the timing belt and V-belts.

So here is my documented take on how to take apart a Bridgeport 1J head. In it, I discover that it wasn’t as terrifying as I had thought originally, and that old-school American engineers might commit some abominations but damn they’re good abominations. I guess this is kind of a Beyond Unboxing, too.

Step 1: Dismount the motor, which is retained by two studs, one with a set of two jam-nuts to let it move a little for belt tensioning, and another that’s the ball handle (you unscrew the ball handle and then untighten what it’s attached to). Then, crank the head about the Y axis (roll) 90 degrees.

Six socket head cap screws live underneath the belt cover casting and retain it to the steel back-gear housing. You can take all these off; pins retain the belt cover afterwards, and it needs to be yanked off. Don’t worry, it’s not heavy. But there’s one catch:

The back-gear timing belt pulleys both have flanges. To remove the belt cover means taking off one of the pulleys with it, and that means removing the belt with it. You have to remove the four slotted head screws that keep the pulley flange on. Once it’s gone, the belt slides off with everything, like this:

This setup is quite the abomination. The timing belt has no tensioner – it relies on good will and good spacing. Mine was getting a little loose from the years. While I haven’t run the machine hard in back-gear range to see if the belt skips, I ordered a new belt anyway since it’s a “Might as well” item. The belts, and other rebuild components which will be seen, came from H &W Machinery Repair.

While the cover was off, I cleaned off the thick layer of congealed rubber dust and spindle oil. I didn’t break into the back gear cavity, however – if you do, remove the nut on the big pulley and use a gear puller or Three-Phase Prybar to pop it off, then undo the remaining screws. Some times the gear cavity is filled with grunge; if your machine had multiple owners, chances are it has both grease and oil in it.

I loosened the cover and a lot of remnant oil started pouring out, so I’ll likely keep it together but drown it through the front oil port later.

The second step pulley and back gear timing pulley live with the belt cover and has a large bearing carrier assembly under it. To undo this, I need to remove the shifter mechanism.

The pins that ride in the shifter groove also help retain it completely. Problem: One of them was completely stripped and wobbly. Due to the pressure exerted by loading springs underneath the pulley, I couldn’t get the pin to bite on its remaining threads and back out. So I drilled straight down the center and threaded the hole for a #4-40 screw that I could then grab with pliers and pull on:

The stock machine has slotted head pins; H&W sells a replacement with a hex wrench drive. Here’s the victim screw driven in…

And a few tugs later, the shifter ring is freed.

The pulley then flies off the other side, since there are loading springs underneath it.

And here we have the brake assembly. The brake is simply a phenolic drum brake setup that crams against the interior of the pulley. Nothing sophisticated at all!

To remove the brake, you have to remove the 3 slotted-head shoulder screws holding it down. However, to do that, beforehand you have to undo the three hex nuts on the top side (underside in these photos) – they prevent the shoulder screws from loosening.  After that, the brake can be wiggled off gently. It will snap closed, due to its own return springs, so watch your fingertips .

The small tongue on the upper right of the bearing bore is the cam that toggles the brake shoes.

Many times, when a Bridgeport spindle brake is worn, it means two things – one, that the brake shoes are worn down, but what I found is that the cam had also dug a little trench into the brake shoes where it makes contact. So this has reduced the effective travel length and caused the brake shoe to lose engagement. In fact, it seems like the harder you wail on the brake lever, the quicker you induce this 2nd failure mode.

Also, Brigeport brake shoes are expensive. Speciality exotic part, sure, but I can do all 4 brakes on Mikuvan for less money using nice ceramic pads too! So I wasn’t going to replace these, but simply make the cam bigger.

Returning to the top side, the brake cam escapes if you untighten the set screw holding its handle pin in place. The pin slides out and the whole thing falls apart.  The cam and shaft assembly are on the upper right.

The fix? Make the cam bigger by welding repeatedly over it, building up more metal, then sanding and filing it down! This was after the rough-sanding stage. I filed a gentle round onto the engaging edges so it doesn’t cause further erosion of the phenolic laminate brake shoes.

Alright, we’re now on the reassembly path. The brake cam is going in back in…

Secured up top, along with installed brake shoes and re-tightened locking nuts.

I reassembled the shifter ring after cleaning the whole area and thoroughly greasing it. In Bridgeport maintenance, you’re supposed to oil the shifter ring daily in production use. I think I’m fine with putting in a few greasewads where it needs to be instead of having to clean up even more crusty oil grunge down the line.

The belt cover is remounted now.

Before final assembly, make sure to thread the timing belt and V-belt back onto the pulleys. Then as you line the belt cover on, wiggle the timing belt onto its large pulley.

When finished, you can then replace the small screws and pulley flange.

Putting this motor on was the precarious part, since it involved holding something pretty heavy and wiggling it from an awkward angle! I threaded the two jam nuts onto one side in order to hold it in place for….

Final head tilt. Here are the newly installed parts! And there we  have it. Shifts great, runs smoothly. Still makes The Bridgeport Clack, but further research showed me that is all in the quill spline drive and there is not really a way to R&R that short of replacement. I’m fine with it.

Moving onto controls! I can’t use this thing from a potentiometer dangling by its wires forever. You may, but I have standards.

I put a little money on eBay into some more machine style switches and buttons.

I had two buttons left over from a project long ago, so they were going to be used as the Run and Stop functions. The same potentiometers got transplanted into a panel mount which I screwed into the housings. Knobs were a matching pair (rare! legendary!) found at MITERS.  The two-position switch will control forward vs. reverse.

The wiring was concocted using disembodied Ethernet cord, which is one of my favorites for pirating cables from their intended purposes. The VFD’s Use of Manual™ just showed a bunch of normal looking switch symbols connected to the forward/reverse, start/stop/reset, etc. inputs.

This is where I discovered another great undocumented feature of Use Of Manuals. The diagram was a lie, but only enough to get you in trouble.

I had problems with it accepting my switch configuration. I found that the VFD didn’t want to read my stop button at all, and it accepted any flip of the direction switch as a “run” command. That is, I can toggle the forward-reverse switch for it to change directions, but it wouldn’t take my stop button input. I’d have to hit the STOP button on the control panel of the VFD. After that, I couldn’t start it by using the start button, but just changing the state of the direction switch would let me turn the knob and increase speed again. Well, all of my settings seemed to be correct for the job, so I was a little confused and figured there must be Undocumented Behavior. This was certainly inconvenient to use the damn thing intuitively, and I certainly wouldn’t let anyone else touch it in this condition.

It took a few friends with experience in industrial controls to point out what I was doing wrong.

 

That is a diagram for a normal industrial magnetic contactor, showing how Start and Stop buttons are typically wired. In these things, the STOP switch is always closed unless something causes it to open (either by accident or on purpose). The Start switch, on the other hand, briefly powers the contactor coil which pulls in not only the main contacts, but a little auxiliary contact that keeps the coil energized and hence the contactor latched. You can see how any number of interlocks (e-stop systems, overload detection, etc.) can work its way into the STOP circuit and turn the machine off when needed.

The VFD is technically designed to replace this setup, so it’s expecting the Stop button to be normally closed. Well, all my switches are N/O type (close when pressed). So the VFD was waking up in an unexpected mode, I guess, where it seems to default to treating any forward/reverse switch inputs as “Okay, start running”. Well this seems a little scary of a failure mode.

Anyways, the Use Of Manual shows all switches as N/O, so it definitely assumes you already know industrial control practices to use it. That’s another endearing characteristic of Chinesium… you better know exactly what you’re searching for, or else you might find it.

Well that’s quick fix. I didn’t order modular contacts with my switches, but luckily they’re manufactured modularly enough to use the same set of contacts, just internally turned upside-down, to become N/C. Now my control panel works as expected – the stop button puts the VFD into slow-down-and-brake, then start will ramp the motor back up to the previous speed it was at. In run mode, I can change speeds at will, including braking down to zero speed manually.

And here’s the test video.

Now that I understand this setup (or do I….), I can build the second control box accordingly. It’s also easy now to add an anti-face-eating emergency stop mushroom button anywhere in line!

The next machine to go online will be Bridget’s cute Japanese friend, Taki-chan!

how about no

Operation ENDURING BROWN: The Battle for VANTRUCK Rages On

May 16, 2017 in vantruck

Awww yeah, it’s getting warmer! Let’s go work on some vans! Aww, it’s raining. Okay, it’s dry now! Crap, I can’t lift this myself. WTF? Why is it 30 degrees tonight!?

-me for the past 2 months

After the skirmish with the insurance company, I spent several weeks scanning Ford Truck bro forums, Facebook groups, and Craigslists all up and down the east coast for 80s and 90s era F-350 dually long beds. This was a triple threat challenge. First, the year range meant the majority of them had long dissolved. Second, short bed trucks were (and are) more popular, so a long bed is already a harder find. And last, it had to be the dual rear wheel version with the built-in fender; while buying a single rear wheel bed and adding fenders was an option, I found that the fender flares were 1. about equally hard to find, and 2. about equally expensive.

I obviously passed up a whole bunch of really crappy ones; those which if I weren’t out to have something nice looking at the end, I would snap up in a hurry, weld patches over rust holes, and ship it. Other choices were simply too far away (i.e. rust-free desert states) to be economical to get. So I bided my time and reached out also to some of the area auto yards I went to previously. I even called one of the ones I frequented in high school back in Atlanta to ask them to keep an eye out in their network. If I’m not obsessive, at least I’m resourceful.

In the mean time, Vantruck’s runability problem worsened dramatically and for reasons I couldn’t easily determine at the time; I can’t be arsed to sit outside during the middle of winter at night and fix vans that often. While previously during the failed Motorama run it made it all the way past Framingham, MA (and back) with only minor hiccups, now it was beginning to fall asleep almost at random. Basically it felt like it would lose fuel feed, stall out, and then take a while to start back up again. Its confident usability radius was decreased to Home Depot runs and moving heavy objects to and from MITERS.

Well that’s no way to own a truckensteinian monster. In mid-March, I decided to send it to live with the same mechanic who performed the exhaust and fender repairs pre-accident, with the idea that he’d pick at it while I searched for a bed. I’d bring the bed to him afterwards and we’d carry on with the anticipated restoration. This plan almost worked:

Hurrrr

I made it about 3 miles out before it had trouble staying running. Being it was still several more to the mechanic, I decided to abandon the mission, turn around, and got maybe 1000 feet. No amount of sweet-talking or coercion could elicit more than a few seconds of running. Not wanting to dump the battery trying to start too often, I called for backup.

That’s one of my friends who has a diesel F-250 which at the time had half a lift kit installed (notice the front of the truck is higher than the back). And in between that truck and Vantruck is a yellow Harbor Freight tow strap. This unique assemblage slowly confused its way through four Boston-area towns. Now, if you guys have flat-towed your friend’s beater down the highway for the 5th time this year, this might not sound like a big deal. Here’s the path we had to take:

Several miles through ill-timed red lights, one-way tight (for something 21 feet long without power steering or power brakes) turns, and the occasional displeased taxi driver. Luckily, and somehow, no police. Needless to say this was a less-than-legal, literally fly-by-night operation!

Alright, well that was exciting. A week later, I got a lead on a great condition 1997 dually bed, which was awesome since it was the newest it could get. The seller was located in Kentucky, and the bed only had some surface rust and a dented tailgate. Among the ad photos was this gem:

 

Yeah, uhh, I’ll take that one. No, that one over in the middle. No, more middle!

I need to up my van game, man. This guy has me beat in a topological sense.

It so happened that the seller had a delivery to make in eastern Maryland in 2 weeks. I offered to meet him in Harrisburg PA (roughly halfway between us) and do the handoff, and he agreed! Well crap, now I had to figure out what to transport a 8 foot dually truck bed with! Gee, if only I had some kind of truck-like vehicle with an 8 foot bed and dual rear wheels. Now, at this time, the mechanic had yet to duplicate the same failure mode consistently, and I wasn’t about to risk rushed work to go 800 miles in its first mission. I’m only marginally smarter than that!

It was time to get Mikuvan a trailer hitch. So begins Operation ENDURING BROWN…

 

Fast forward a week, after I bothered the local U-Haul guys to call several of their hitch distributors, many of which responded with “What?” when presented with the year, make, and mode. I’m used to it. One of them said their computer system says they had one in stock, but he would have to wait until the following Monday to go verify because he’d “never recalled seeing it on that shelf”.

Well, good – Mikuvan itself, despite its local uniqueness, also hides in plain sight like that, since most people’s descriptions of it stop at “white van”. Your move, Cambridge police.

Fortunately, it was indeed in stock, and I had it rush delivered. The package exploded in a cloud of warehouse dust when I opened it up. Yes, I can tell you’ve never seen it on the shelf. It actually didn’t attach where I thought it would; Mikuvan has two structures at the end of the frame near the leaf spring shackles which I thought were tow hooks, but in fact this hitch mounted to them and not the more numerous thru-frame holes. Makes sense – they’re likely to be the single strongst parts of the frame.

U-Haul wouldn’t sell me a trailer without a lighting harness, so I had to pull out one of the tail lights to install one. The system they sell is quite well-packaged. It’s a little headcrab thing that splices into the turn signal, running light, and brake light circuits, derives power from any one of them, and at the same time senses which light is activated, piping this information to the trailer lights.  It took me about 45 minutes to install.

 

It’s a bright and early April! After making sure the seller wasn’t just a friend of a friend playing an elaborate April Fools joke, I set out with a 11′ U-Haul trailer. My, how the tables have turned.

They don’t have flatbed trailers, so I made sure the bed could fit over the roughly 4′ 6″ spaced side rails of their standard utility trailer. Worst case, I’ll throw some 2x4s on top of it.

This trailer weighed 900 pounds empty. I could feel that every bump when it would tug on the hitch and Mikuvan’s short wheelbase failed at not bobbing up and down. This was going to be exciting indeed. A couple of hours later, and I end up in….

 

….Upper Manhttan!? Wait, this isn’t Harrisburg!

I needed lifting (bro) help, and all of my friends are gainfully employed and couldn’t head out on short notice on a weekday for a mission with an unknown completion date (van missions NEVER have a competion date!)

I thus enlisted the help of Cassandra, fellow van connoisseur , with the only issue being I had to take that trailer into Manhattan to pick her up. I don’t know which was more painful, threading a trailer through 133rd St., or paying that much money to New York State for the privilege. (The observant would note that maybe I could have gotten a 1-way trailer from Harrisburg; this would have cost much more than a two-day local rental. There are no miles kept on trailers, and I also wanted to make sure I got a feel for it on the way down)

 

On site in our favorite Waffle House parking lot. This Waffle House is my gateway to the South; it’s been part of every Dragon Con trip so far, usually in both directions. Leaving the Harrisburg Waffle House is like exiting the Panama Canal, or rounding the Cape of Agulhas.

The seller showed up with the same red flatbed, just with less trucks on it. The transfer went quite smoothly – the U-haul trailer’s side rails were only a few inches taller than the flatbed, so less lifting than we both anticipated was needed, more sliding.

Here’s Cassandra and I posing for the glory shot.

Next, it was off to Lowes to pick up heavier-duty ratchet straps and a rubber floor mat to cut up and insert between the bed and the trailer’s side rails to prevent damaging the bed on the bottom.  I mostly rigged the bed straight down to hooks on the bottom of the trailer floor; this had the added advantage of looking like the bed is just hanging on for dear life to everyone else on the road, so hopefully they stay further away!

Not less than eleven hours later, I emerge on the other side of hyperspace in the warehouse parking lot. A typical Motorama return run takes 6.5 to maybe 7.

This was probably the single most stressful thing I’ve done in my life so far. The trailer itself was well behaved and did not wobble. Beyond that, I had zero rear vision. Day turned into night quickly after leaving Harrisburg, with a fucking rain front chasing me the whole way. Furthermore, the bed weighed a few hundred pounds on its own, and also presented a huge cross-section to the wind. It limited my speeds to generally 55-60mph just by being unable to power past it without hammering the engine the whole time, which put me square against all the 18-wheelers who wanted to go 75-80. And when they pass, the wind load would push the trailer a few inches sideways; Mikuvan of course lovingly and devotedly followed each time.

Then it came time to drop Cassandra off in Manhattan. So here I am, blindly driving a flying truck-ass through Manhattan and up the George Washington Bridge, at night, in the rain, with weeknight post-rush-hour traffic. People there don’t take kindly to that sort of thing. Are you fucking trying to kill both of us, or are you trying to make some kind of statement by buzzing me on the right? I have a flying truck-ass. You don’t.

I also couldn’t return through the Hutchinson and Merritt Parkways, which forbid trailers, so I had to fight it out on I-95 in Southern CT. By then, the rain had turned into sporadic mist and fog, so I was also working with reduced visibility; the only way I could tell there was an incoming semi was the soft yellow halo around the bed getting more intense, then getting shoved aside a foot. Let me tell you about when this happened on both sides at the same time as I was in the middle lane near Stamford.

Around 1AM east of Bridgeport, I decided to pull into a rest stop and regroup. Leaving there around 2AM, I got back into town at 4:30. I just sort of died mentally the day after. Sorry for not answering your calls about where your trailer is, U-Haul. You have my credit card info, now fuck off.

 

A day later, I drop the bed off at the mechanic’s! Things were gonna be AWESOME!

If only it were that simple. The next thing to hit me was tax season – let me tell you, the government is not pleased with me refusing to be a wage slave. Seriously, there’s not much love for the self-employed going on here. What it put me in was a situation where it was not adult-responsible to have a $6K project car build coming up. By the way, do you need something designed or prototyped? How about some Ragebridges?!

 

Not like they were having any more luck on their end. I asked them to prioritiz getting it running before any of the planned bodywork. After a carburetor rebuild did not resolve the sporadic running problem, I decided to cut my losses for the time being and asked them to stop work, and put it mostly back together so I could have it towed back to base. I didn’t want to run up more shop charges on something which hasn’t yet done anything consistently to diagnose. If it was going to become throwing parts at it, I’d rather take the time to do it myself.

 

I went over to help with the rigging of the replacement bed in preparation for a return tow. See, this is what I’d WANTED to do to get the bed in the place! Doing this at least made me feel better in one way: All the important exterior dimensions lined up. There might be some hope, then, that it is a drop-on replacement. Even if not, it 1. won’t be fugly, and 2. might only require some flat adapter plates.

The same night, I got a call from the truck driver that he was on the way over. I actually passed him going the other way:

Ah, nothing like watching your hopes and dreams pass by on a hook.

I spent the next few days pondering my priorities. Do I want a working vantruck, a white vantruck, or a Tesla-powered vantruck? These are almost 3 different goals. What if I just replaced each cylinder with a melon and a bevel gear?

I considered going to an aftermarket EFI conversion kit (like this!) first, as an intermediary step. You can’t begin to get me to trust carburetors, no matter what, even if it’s not the cause of the problem, which it looked increasingly like it wasn’t. At least that would bring it up to something in this millenium! However, I wanted to make sure I found the root of the problem before buying anything drastic.

Hell, I even considered the nuclear option of selling it as-is with the new bed attached (where-is?!). That would put me ahead financially and subtract a potential eternal project / rental liability from my life (as I’m not in a position or area where it’s easy to keep a non-running vehicle hanging around forever. Anyone have a front yard and some cinder blocks?)

but where is the fun in that

The great battle of the U.S.S. BROWN C. STENNIS continues. Stay tuned for more!

 

Brushless Hipsterism Intensifies: Returning to Brushless Rage. Brushless Mini-Rage!? And Trying Hub Motor Drive in a Beetleweight

May 12, 2017 in Motor Controllers, Reference Posts, Roll Cake

Oh, Brushless Rage… how far you’ve fallen. It’s been standing idle since late last year when I got the first version running. Thereafter, it began having some rather obdurate power supply problems that I couldn’t resolve with a few different attempts, and with #season3 still unknown (TO. THIS. DAY. UUUUUUGGGGGGGGGGGH.) and having to pick up and move shops, I lost motivation. Now, with the spring and summer silly go-kart season coming up, me really wanting to pregame getting Overhaul back in shape ( *cries deeply* ), and my comrades over at Robot Wars screaming for assistance, it’s time to put my robes and wizard hat again.

The last time I really worked on Brushless Rage was in October. After tuning out the first one, I went ahead and made a 2nd one. I wanted to get Sadbot running on them for a few test drives.

Here’s my innovative housing for the two controller! Bolted back-to-back with drilled holes in the Ragebridge shipping box.

And that was all! It was retained by a few zip ties running through the bottom ‘breadboard’ baseplate. I didn’t take much test video of Sadbot running on them, unfortunately;really the only one that exists within easy reach is, uhh, this one. While it doesn’t show them getting whipped, they definitely don’t not work! Yay!

But not for long. I soon lost both of the units in further off-bot tuning of settings. They didn’t blow up, but simply failed to ever power on, with the LM5017 regulator simply sitting there getting hot. The only “fix” was replacing the regulator, and I say “fix” because that really didn’t fix anything, and they would die again within minutes or even seconds.

No problem… maybe it’s just an issue with the two boards. I’ll just try another one of the five total I ended up making….

Nope. Nothing. They died one by one, all to the same symptom. I tried redoing my math for the regulator for the 4th time, thinking maybe  I made a mistake somewhere. I even tried mimicking the reference design to try and get something running. I literally never do that.

At this point, I figured it must have been something incredibly dumb and simple I missed. But why would the first two have worked at all, even for a little while?! Convinced the solution might just suddenly invent itself, I stopped thinking about it.

And so here we are, a few weeks ago, when I’m slowly building up a new rev of the logic board that fixes up some trace routing problems and Little Blue Wire problems. Again, the logic regulators kept exploding, some times dramatically taking out the input trace like seen above. The little light is strapped across the 15V gate drive supply to give me a visual indication of it being on.

What is with me and being unable to use switching regulators!? I recalled the Ragebridge Diode Debacle of 2015, and decided to take one last Hail Mary run through the datasheet along with friends to carefully cross-check each other for boneheaded mistakes and…….

TI, you assholes.

So here’s what’s going on. The Vcc pin of this chip allows you to power it from its own output voltage, which is often fairly low, so it prevents a lot of heat dissipation in the chip since otherwise it would have to derive its own power from the voltage input (up to 95V). But what I missed is this only works up to 13 volts. My gate drive supplies were 15 volts by design.

Beyond that? Who knows?! It might work, it might not. I’m guessing my first two were just high enough in manufacturing overhead that they worked for a little while. Subsequent statistics were not on my side.

Okay, whatever. I cut off the 11.3kohm feedback resistor and threw on a 9.1kohm to drop the voltage from 15V to about 12.5V and let’s see what happens.

Ah, it wakes right up.

Of course it does.

So I decided to respec the gate drive for 12.5V. Why do this instead of go for the full 15+ volts? Because I’m really aiming to make this design work at high-for-robots voltages of 36-48v, possibly up to 60V nominal with a different power stage, so I’d like to save the power dissipation in the chip’s onboard logic power supply.

The change in drive voltage will slightly affect the drive characteristics and switching time. For now, I’ll keep all the power stage parts unchanged, but I’ll probably tune the gate resistor values later.

 

To get rid of the noisy ripples on the feedback network and to stabilize the switching frequency, I added some more bypass capacitance to the chip. This was not included in the design at first, since I figured my large ceramic input and output caps were nearby, but it really really wants its own little private capacitor on Vcc. Gee, I thought I was a princess at times.

So now this thing is pretty much bombproof. Here’s a video of it throwing around one of the 30-pound old MIT CityCar prototype motors (which I inherited 4 of after the project was dismantled):

In that video, it’s running from 36 volts. I tested it with a smaller motor all the way up to 50V input before getting too scared for my power supply’s life; I’ll need to try it on a larger high-for-robots voltage power system later, but nothing smelled imminently unhappy!

With the regulator death issue apparently behind me (again) I decided to push another board revision. This time, I added all the necessary bypass caps and changed the layout of the logic power supply, as well as take out some parts I decided were superfluous.

The logic power supply got a little smaller and more electrically optimal. The whole thing is just less messy now. I like it – it takes up around 1/3rd square inch of PCB space on one side. At the behest of a professional PCB engineer friend, I turned the inductor 90 degrees and joined it with the LM5017′s switching node with a small trace instead of a larger groundplane. This would prevent the switching node (a source of huge voltage swings in microsecond timescales) from broadcasting as much noise.

Besides some other minor trace chasing, what’s going on down below on the board is also something experimental:

That there is a bidirectional optoisoated I2C bus for transmitting data between two microcontrollers which should never meet directly. I had a single-direction opto input on the board revisions so far, but this prevents updating of settings via the SimonK/BLHeli type bootloaders. That means tuning the settings require busting out my chip socket every time, which is annoying. I reviewed a couple of bidirectionally isolated bus schematics and decided to try this one out first, since it involved diodes only, not transistors.

The problem is, the I2C bus is a open-drain configuration with pullup resistors and ’1′ bits transmitted by pulling the line down to 0v. I kind of wanted to try keeping the opposite polarity, so to speak (even though SimonK supports an inverted input setting) just because I’m used to thinking about things this way. So I tried flipping the circuit over…. pullup resistors became pulldowns, and common-emitter became common-collector, and so on.

It makes sense in my head, but I’m sure excited to see this work!

On the board, this is the layout. It doesn’t consume much more space than my previous 1-direction optocoupler setup, and can be bypassed for testing with 2 wires if needed. That’s the nice thing about keeping things upright signal-wise.

So before I sent this board revision out, I stopped for a moment to think who would really be wanting to use Brushless Rage. I’d designed the 12-FET board to effectively replace Overhaul’s 250A DLUX controllers (with more realistic ratings, mind you). I’d say the majority of people who would buy such a thing won’t be running motors that big.

Recently, the thought of a “Half-Rage” has been coming up in my mind as something worth pursuing. This would be a board with about half the footprint of a RageBridge 2 and supporting about 1/2 of the amperage. As some curious question-askers had innocently drilled into my mind, this would be an Actually More 30lber-Sized controller.

> mfw "When are you going to make a 30lber/12lber version of RageBridge?

 

With this in mind, I decided to make a copy of the power stage and began downsizing the hell out of it.

Step 1: Reap what I sow when it comes to the sheer number of vias I deposited under the FETs.

After bunching the FETs together, I referenced one of the earlier abandoned Brushless Rage layout ideas for the output wires. This board is now short enough that I’m comfortable pulling the phase outputs all the way to the right with the power. Keeping all my wires on one side is something I prefer.

Somewhat final routing of the fat bus traces here. I had to move a few gate drive traces, as there was no longer an opportunity to swap sides in the middle of the FET bank. Power+ runs straight from the bottom right corner, through the bus capacitors, into the high-side FET. Power- emerges from the current shunts and then has 3 paths to return to the buscaps before being slurped up by by the wire hole on the upper right.

Here’s an overlay of the signal board design on the power stage, showing roughly the size of things. The final power stage is 2″ x 2.75″. Not the tiniest thing, but I have more capacitors than you!

This board shares a lot of thermal characteristics with RageBridge, so I’m pretty comfortable calling this a 50A continuous class controller. 50 real under-partial-throttle amps, so that’s what, like 1,200 Hobbyking Amps?

In all likelihood, this controller will be able to handle an average 63mm SK3 motor in continuous duty applications like a silly go-kart. Robot-wise, it will probably be stressed handling the same in bidirectional drive mode.

Fast forward a few days and….

OhmygoditssocuteIjustwanttohugit and then make it run a 80mm outrunner on 12S violently. I’ve ordered parts to make a handful of these, and two are going on Sadbot ASAP to be driven until something blows up!

Direct Outrunner Hub Drive for Your Little Bot

Next up, something even smaller!

So I’ve long been a connoisseur of fine handcrafted hub motors. I got curious recently on using direct-drive small outrunner motors in an ant or beetle after thinking a while on the redesign of Roll Cake. Version 1 of Roll Cake was honestly just a braindump of a vision I’ve had for years for the shape of the bot, and everythng else came second to that. On the beetle scale, the multi-pulley serpentine pulley drivetrain simply had too much friction for the Fingertech motors (which were severely underpowered for the task) to overcome.

For the next version, I’m ditching the triangular cheese wedge shape for something more straightfoward. The cheese wedge will be back for a heavier weight class. Roll Cake’s design really wants to have the middle of the bot kept clear for the flipper linkage. I’m sure I could work around it with low-mounted drive motors and similar, but this was an excuse to play with brushless things!

I based my thoughts off Jamison’s mini-gimbalbot which used camera gimbal motors for drive with a small Hobbyking R/C car ESC. It drove “okay”, certainly capable of a weapon delivery platform. So naturally, I wanted to put some SimonK-capable controllers on it and see how the handling would change. I got a small selection of motors: A pair of DYS and Quanum 28mm motors as well as a pair of Multistar “HV” 460kv motors. 460 RPM/V is reeeeeally slow for that size of motor that isn’t a gimbal motor, so I was quite interested in them.

These are the gimbal motors. I like them for their pancakeyness – the Quanum motor is more 30mm and has a bigger stator.

Playing around in the CAD model a little for component placement. At this point was when I realized Roll Cake in this incarnation might end up looking a lot like The Dentist :P

I designed up a few hubs that bolt to the face of the motors and have a tapped middle hole to sandwich a wheel. The wheels are spare 1.625″ BaneBots wheels that I originally bought for Candy Paint & Gold Teeth.

Shown with those motors is a ZTW Spider 18A controller. My typical SimonK ESCs, the Afro series, were out of stock when I placed this order, so I took recommendations from people on what I should use. The Spider series are fairly popular these days among small bot folks.

The issue is, they come with BLHeli firmware, the other other open source drone racing / vaping rig development path. It’s a newer effor than SimonK and has a more polished interface. I’d read about it before, but not worked with personally. Other builders have said it doesn’t run robot drivetrains as well due to being much more optimized for propellers. So hell, why not – this was a chance to explore that side of things.

Here’s some real life CAD layout, featuring the Multistar motors.

I really wanted to use the gimbal motors, but they disappointed me in bench testing sufficiently that I didn’t even end up installing them. Basically, they can’t draw enough current to make torque at typicall little-bot voltages. With phase resistances of 10-20 ohms, they can really only draw ~ 1amp or so. I mounted one in a vise and could stop the motor with my pinky finger at full radio stick input.

These motors might be better at 6S and up, but for the time being, since all of my small-bot batteries are 3S, I decided to pursue making a test platform using the Multistar 460kv motors.

 

The platform of choice was…… one of Candy Paint’s spare weapon pulleys. I literally spilled my “preformed robot spares” bin on the ground and tried to see what was good to use as a base. Hey, it’s round and has convenient wheel holes in it already! All I needed to do was quickly whip up some motor mounts (3D printed) and I was in business.

 

Here’s everything hooked up. That nut is for a counterweight on the front to add some friction against the ground while turning. Otherwise, it had a tendency to keep spinning and spinning if you even thought about turning.

Communicating with the ZTW Spiders was a hell of an adventure in its own right, and I am putting this post under Reference Posts because I’m 99% I will need it again or someone else will randomly find it while needing the information. If there was any industry that continually pisses me off with how undocumented and tribal-knowledge focused it is, it’s the R/C anything industry.

So, here’s how everything went down. I lost my AfroESC USB communicator, so I purchased the Spider SPLinker advertised as working with the controllers. I also bought one of these stupid things:

That’s a “SimonK/BLHeli compatible” dongle called the ESCLinker. It allegedly can talk to either kind of ESC, but there was nothing remotely resembling a manual or operating guide; all of the search results for this brilliant device were people complaining that there was no manual.

So I’m writing the manual now: This thing does not want to talk to KKMulticopter Tool (my go-to for flashing SimonK ESCs). It will only talk to BLHeli Suite. As a matter of fact, I couldn’t get the Spider SPLinker to talk to ANYTHING. For all of my tuning here on, I used the ESCLinker tool.

Here is BLHeli Suite, which is hosted on the sketchiest possible website that is one tier above compiling it from the Git repository yourself.

Notice how I’m connected to the ZTW Spider now. The ESCLinker (and SPLinker) install as virtual COM ports.  The necessary baud rate is 38400 baud, not 19200 (Afro/Turnigy USB dongles, to my knowledge)

By the way, once I realized this, I tried to talk to the SPLinker and ESCLinker on KKMulticopter Tool again using 38400 baud; no dice.

Further investigation revealed that the ESCLinker needs these options to communicate to the ESC – both options 2 and 3 will work. So if you’re listening, people mystified by the ESCLinker: Talk to it on 38400 Baud and ask it to communicate to your ESCs with BLHeli/SimonK 4-way-if bootlader.

Ugh. One of my selfish reasons for wanting Brushless Rage is so it’s one known quantity and I never have to dick around with other people’s open-source bullshit again.

So with all that behind me, I decided to try out BLHeli drive on the little pulleybot. I went with intuitive settings based on my SimonK advice, which included “Damped Light” mode, a fancy euphemism for synchronous rectification/complementary PWM, medium to low timing and maximum start power. BLHeli also has a “demag compensation” feature which appears to delay commutation to compensate for current decay in the windings. Who knows!? I wasn’t given the imprssion that its users actually understood what it meant, nor does the manual really say anything useful.

I found that Demag Compensation turned all the way up gave the best performance, along with maximum start power. However’ it still couldn’t compare with my SimonK experience. It seems like even maximum start power is much weaker than what SimonK permits you to do.

Here’s the final test drive I made with the BLHeli Spider ZTWs:

I’m honestly not very impressed. I think BLheli is very much optimized towards multirotors and helicopters (hmm, maybe it’s even called BrushLessHeli for a reason!) and the settings are more high-level and mask the underlying mechanicals of the firmware. I think this makes it much more accessible to hobbyists, though. In the end, I’m not very enamored by it.

These were my final settings:

For a direct comparison, I decided to replace the ESCs with my old SimonK Afro 30 amp units. These have been on quite a few bots now, starting with the original Stance Stance Revolution, and they were completely beat up. But they still worked!

A direct replacement into the existing wiring harness later… we have SimonK!

I found myself in the awkward position of using KKMulticopter Tool to compile a customized SimonK formware, then uploading it via BLHeli Suite because my USB dongles didn’t talk to KKMulticopter Tool; I’d lost my AfroESC USB dongle a long time ago.  BLHeliSuite doesn’t seem to have a firmware editor window that I’ve found yet.

Here it is. I found the SimonK version so much more responsive that I actually needed more counterweight on the front. So, a non-fitting bolt gets zip tied to the nut! Now the bot’s a lot more controllable:

I like it a lot. It might even be worth doing 4WD to give me more yaw damping, or I’d have to design the bot to be well balanced enough on front skids, or something. I used my typical SimonK parameters: complementary PWM, maximum braking power, maximum braking ramp speed, and adjusted start PWM limits to something like 50%.

I’m aiming to get Roll Cake and maybe Colsonbot running for this year’s MomoCon in a couple of weeks, so hopefully I’ll post up some design news soon!

 

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May 08, 2017 in Bots

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