This was fun:
So, for more info and context for those who don't have a YouTube attention span...
For a while I ran out of money and motivation to take the next steps. Buying batteries was an impossible commitment to make while I was out of work, but it was clear that the ones we had were not worth using for more than tests. Enter my fantastic new job at a legit video game company, and suddenly it's just a matter of finding the time! Some very powerful lithium modules came available on battery hookup and I jumped. The results from just changing to new modules with a bit more voltage and usable amperage was really noticeable (see the video before the last one,) and our gravel driveway paid the price again. It still wouldn't do donuts on dry pavement, though. This was a bit disappointing, but inspired a lot of imagineering. Like how to move all the weight forward, hoping to give the rear axle less traction. The project to add front brakes without spending shifter-kart money (fail! more on that later?) resumed. And of course we still want more power! A used 72V controller finally rolled around on eBay on a day I was looking, so the next iteration of this thing will probably have another 33% more power and (unloaded) maximum speed. Except...
I noticed a time or two that the throttle seemed extra responsive in reverse, but chalked it up to my imagination and the fact that I was facing "backwards". Leading up to the holiday break the kart was balanced only semi-precariously on our lil portable mid-rise lift with the front spindles yanked for some reason. Then it turned out all the king pin bearings were nice and crunchy from a previous lifetime of indoor kart track use. It also turns out to use the same bearings as a skateboard or pair of roller-blades, so they're bleepin' cheap on amazon. But it took a while to get around to all this, and in the meantime, we had some holiday drizzle and the kart, including motor, got a tiny bit wet under the car port. So while it was up there, it seemed wise to check that it was still working by hooking up just one battery module. One way or another, it got tested in forward and reverse with no load, and the response and top speed in reverse was obviously much better. Before all this, one of the brushes was pulled out of the motor to see if they were "timed" and it was running the wrong direction, but aside from some uneven wear, it looked symmetrical. They all got turned around to wear them down the other way, and it turned out that one had popped out completely and wasn't touching the commutator at all. So we were also down one brush out of four. Not sure if that means it was losing 25% power, 50% power or none...but fiddling with the brushes didn't change the forward/reverse differential.
Anybody out there who is familiar with electric golf carts would have figured this out instantly. The controller has a terminal that you feed power to when you want half speed, such as in reverse. But mine was hooked up backwards. So...remove that wire, and it's now full speed in forward and reverse. All the plans for big upgrades over the holiday break went out the window, and I threw it back together to test. And as you might have seen in that last video, it will now to dry-pavement donuts with some over-inflated race rubber on the back. They're small...probably would be front tires on a real race kart for adults.
Donuts achieved! So now the question is whether all those mods ("fix" the weight bias, add front brakes, add power) will result in smokey burnouts?
Full speed reverse FTW
Grassrooters...I am beyond excited. I'm Trabanting F30 M3 excited! In the driveway right now is a new-to-us cutie-pie bench top vertical mill and enormous metal table, plus this amazing (-ly heavy) homemade rotary phase converter! (But we'll have a modded Toyotoa Prius inverter that will give us 3-phase from whatever, even batteries. More on that later if anyone is interested?)
BUT ALSO! I got my front brake hubs made
and an extended keyway for a "dually" kart axle
Hot sex, right???
angusmf said:(But we'll have a modded Toyotoa Prius inverter that will give us 3-phase from whatever, even batteries. More on that later if anyone is interested?)
Consider me interested.
Dually go-kart FTW
In reply to obsolete :
Welp ok. First you need a 3rd gen prius inverter, which runs about 150 US, depending on the day, tides, etc. Then you need to open it up and install a "mod board" that replaces the logic section. The open source part of the mod board design can be seen here https://github.com/damienmaguire/Prius-Gen3-Inverter/tree/master/Mains_Inverter and there's probably a thread on openinverter.org that I'm going to have to read on how to use it. The design files (if you wanted to order your own instead of getting one from Damien aka evbmw.com) are not yet public, but mostly because he's busy. So I just bought an extra one he had.
The basic deal is that the Prius inverters contain a buttload of Toyota-grade power electronics. Two separate inverters for the two motor generators in the hybrid transaxles (this is all the same on every Toyota hybrid, barring differences for design improvements and different sized vehicles--check out Weber Auto Youtube for amazingly great videos on these and other automotive points of interest,) a DC/DC converter to give you 12v, and a buck/boost converter with enough "snot" to raise the voltage that the motor sees from ~200 battery volts to up to 650. The main motor makes enough power to move the car with no help from the engine at all, so that's frickin serious. Anyway, clever folks have modded these things to do all sorts of stuff like run other AC motors, charge the battery in your EV. But 3-phase is 3-phase, right? No reason you can't just set it to 60Hz and run some industrial machinery? It's happy to do that from batteries, just like it does in the car, or by using part of the un-used inverter (cause there are two) to rectify your wall power to DC. Then the converter would operate in boost mode to bump the bus up to the necessary input voltage to give you the desired output voltage from the other inverter. In theory you could have this going for less than 300 bucks. Dunno what a rotary converter costs. Guessing more.
But hopefully pics and videos later on when I have one built and powering the mill.
In reply to AngryCorvair (Forum Supporter) :
Yeah, it should be pretty cool...
But brother, how would you like to see a kart axle with a spool wrapped around it? With a Prius transaxle wrapped around that? My "I'm no scientist" calculations tell me they should put down somewhere between as much torque as a NA 944 does in 1st and 2nd , but can spin clear up to highway speeds. Would still have to find some kart tires tall enough to keep the box from scraping on the ground and a chassis that says "I wanna go fast!"
Trying hard to build this dang kart, but work and stuff keeps interfering with what's important. :/ Here's a very short video of the dually setup. It'll work, but how to change tires? Particularly the inner ones? The wheels need keyway slots like the hubs so they can slide past the keys with the hubs. Sometimes the keys are hard to take out, so it would be nice to be able to leave them in. We'll see how this works, but could wind up having the machinist make us little dually spacers to bolt the rims together instead of using two completely separate hubs like this.
The rest of the kart is like this at the moment. We have all the parts, but they don't all have the requisite notches and holes and we need more free time to assemble things. Itching for it though.
This turned up on my feed today...pretty cool! He has a LOT of batteries, and looks like maybe a 9" motor. I keep trying to get my hands on one like that, but they slip through my cheap lil fingers...
He seems to be going for speed (and maybe The Distance) vs burnouts. 
Looks fast!
It's time to re-mount the motor, and I've been debating removing the mount plate that's welded on the kart. The motor plate is bolted to it with a piece of angle, but it's pretty janky, flexy and hard to get the motor sprocket on the same plane as the axle sprocket.
To replace with something I make from this, or buy on the ebay that would be the same but aluminum and not "free".
That arrangement would clamp between two of the frame rails like a "normal" race or shifter style kart. I'm concerned because the motor weighs over 60lbs all by itself. Either way, it needs a brace to triangulate from the top of the mount to somewhere outboard--or something to directly support the dangling "body" of the motor.
Just found this so I haven't gotten to watch the Youtube videos yet, but it looks like a blast! (And I agree with you, editing SUCKS.)
Cool. Welcome back. :)
Do what now?
In reply to OHSCrifle :
Turns out the burnout go kart wanted a trailer. If life was fun and fair, everything would just work out great and I'd be back here posting about progress--but the last month is the first time we've worked on this project in almost a year. I wanted to get rid of it. So who knows.
Front brakes and the rear dually setup are still coming. 72V, not so much. At least not yet. The "trailer" will have two big PA speakers and a big battery. The battery for the kart will go in the front bumper to unload the rear tires, but with the trailer's inertia, we expect it will be easier now to do a rolling burnout. Ultimately, the kart battery might live in the trailer if we can make that flexible connection safely. Going to test some lawn mower tires for less grip, and the front brakes should help when they're online.
Happy December to everyone!
Was hoping these lawnmower tires would make good burnout tires, but only have one rim they will fit. With the wrong hub pattern. Sometimes you eat the bear, sometimes you're just stupid.
Also, Nicki is getting decent at the TIG. She welded these old bed frame rails onto the chassis as battery mounts.
More go kart trailer pics and some randos from the Vegas GP Friday practice that lasted 5 minutes.
Update! We're going to try to take the kart and sound trailer a Cleetus McFarland Burnout Rivals comp this year. Also cats.
UPDATE: We're not gonna make the first Burnout show. Surprise surprise!
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