RazEr REV2: Mostly there

Thursday, July 12th, 2012 @ 6:26 | Project Build Reports, RazEr REV2

Over the past few days I’ve been mostly hanging out at the Georgia Tech Invention Studio. I was nominally there as “guest lecturer”, but I don’t quite think their own 2.00EV is organized yet to the point where I can feel comfortable with that title. All the ‘students’ are actually lab instructors (similar to our MITERS keyholders), so there wasn’t that much ‘teaching’ to do. I did hold some impromptu lecture-like things and generally advised people on their builds where needed (and fixed the waterjet?). Regardless, some… interesting products are coming out of it:

It’s literally twice as long as some of the other scooters.

I’m back now, and one of the first things on the agenda is getting the half-assembled repackage of RazEr up and running. I sort of left this in the middle of construction when I zipped off to Atlanta for the weekend. I had the frame ‘box’ assembled to test fits, but I pretty much had to take it apart again to actually install stuff. My direction was essentially assemble the major subassemblies first (make the fender, reinstall the motor, attach the front end) and then lob the electroncis back in as-is, since it worked fine before.

Here’s the fender in place with its leaf spring installed.The ‘sheet metal work’ was done on a vise, then fitted in place using just tightening screw pressure. 5052 aluminum bends very easily, especially in 1/16″ thickness, so I was literally just leaning on the part to get the bends I wanted. To do the large radius sweep at the top, I bent little by little in ‘facets’ which weren’t drastic enough to be seen as disrete (though you can kind of see it).

Now that I’m a little more comfortable with making sheet metal geometries compatible with other 3d solid parts, I might incorporate it into more builds in the future.

The fender is just mounted on a chunk of 1/4″ threaded rod. Nothing fancy at all this time – no spacers, even. The pressure of the leaf spring alone is enough to keep it in place reasonably.

More progress has been made on frame assembly, with the folding joint  reattached now. I traded the former front end for a new A3 type front that was part of the leftovers from my 2.00EV. It’s substantially less beat to shit and doesn’t wobble as much, and I swear it’s a little taller than the one I had before.

I had a left over new fork from building Straight RazEr (whose wreckage has since been donated to Kramniklabs) which I dug out for this build.

I forgot to take a picture of what’s going on with the 5″ colson wheel, but there is actually a type 1614 bearing bored into each stock Delrin bushing. The Colson comes with a 5/8″ bore bushing  that has a 30mm OD (which presses in to the 30mm bore of the wheel itself). I tried to find a > 30mm bearing that wasn’t of a ridiculous axle diameter so I could bore it into the wheel directly, but gave up and went the other direction instead.

A ‘stock check’ of bearings I had turned up some R8 type and 1614 type bearings. Both were 1 1/8″ outer diameter, which I could bore into the Delrin bushing, but I settled on the 1614 bearing since I easily located a stock 3/8″ bolt to serve as the axle pin.

The job itself was done on tinylathe, which is probably one of the handiest tools I’ve ever worked with.

Moving on to the electronics deck now, I put together the ‘switch panel’ which holds the charge and controller ports as well as the annoyingly bright blue LED endowed power switch. The idea is to have BAT and PWR jumped externally with a Deans ‘patch cable’ so I could jack in a flow-through measuremen device like a Wattmeter if needed. Else, the switch is to serve as the primary turn-on mechanism.

It’s better than the yank-the-battery-connector setup RazEr Rev has used since forever, but I’m wondering how long until this switch falls victim to no-precharge arcing damage like the very first switch arrangement.

The interesting part is on the back. Instead of connecting the switch’s built-in LED to ground directly, I threw a 100 ohm resistor on it. This should prevent the light from exploding right away, as it happens when you try running 12v rated switches on 36 volts… Otherwise, there are just a few select wire jumps which bridge the two Deans ports through the power switch. Note the back-to-back soldered Deans connectors on the right…

With the switch panel done, it’s time to load all the electronics back in. The same shell-less Jasontroller appears, bolted to the aluminum frame directly for some heat sinking. There’s a bit more space for batteries this time, since they can reach all the way under the folding joint, but unfortunately it isn’t enough to actually add more cells – just maybe some padding. If I wanted more battery energy about the only good option is moving to prismatic cells.

With everything wired back to the way it was, I shoved the 3d-printed front endcap on. This was one of those pieces made on the Lab Replicator™.

And the repackaged shot. Unfortunately I gave away my only other black Colson wheel, so it’s gray for now. When I get another one (or get it back), the bearings are transferrable.

This frame rides significantly lower than RazEr Rev – too low, actually. This is likely due to a difference in head tube length between the A3 I got like 5 years ago (for the original RazEr!) and now. RazEr Rev rode slightly ‘nose up’, but this one is definitely nose down. The clearance at the front is about 3/4″, decreasing to less than 1/2″ when I’m actually riding it and the rubber block is compressed.

Not going to work. I’ll compensate by making the two wheel fork sides a little longer. In the mean time, it is rideable, and handles just like it used to except with more stopping. And less exposed wires – check out the 3d printed wire guide at the lower right.




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    3 Responses to “RazEr REV2: Mostly there”

    1. Eric Says:


      If you were to speculate the cost of this, including the hours of winding the motor, etc., how much would it be?

    2. the chuxxor Says:

      Rough guesstimates for one you build yourself:

      Waterjetting (if hired out): $400, mostly 1/8″ plate with some 1/4″ and the 1 chunk of 1/16″.
      Batteries: $320 (24 A123 cells at $13 per cell, less if you Hobbyking it)
      Motor: $700-1000 of machine work (if hired out) + $150 of non-material parts (stator, magnets, bearings; if bought new)
      Wheels: $35 ($17 per colson)
      Controller: $45 (jasontroller)
      Razor scooter: $39.95 (A3 on sale)
      Not including: wiring, misc. hardware and screws.

      Time: order of 10 hours if you have all parts ready (and did not have to do machining yourself) else 15-20 hours.

      Now, if you used a chunk of aluminum channel and built a Kitmotter…

    3. the chuxxor Says:

      $80-100/hr is not unusual for professional machine services, and I’m estimating it would take an experienced manual machinist 5-6 hours to pound it out (it took me, an unprofessional machinist who doesn’t really care, about 4 hours), + stock materials cost, so I think $700-1K is a good guess.