Space Kart - Project Updates

Dat seat cushion though…

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That appears to be satisfyingly rigged and dangerous!

I’m wondering if some mountain bike disc brakes might be up to the challenge of controlling the finished version - I gather that 203mm brake rotors are typically designed to handle the brute force of downhill riding, thus might handle the finished kart’s no-doubt energetic braking characteristics. Hydraulic brakes with heatsinked pads might be the way to go.

Does the new controller have regenerative braking or we could shunt the motor to power resistors to brake?

Those resistors are going to need to be huge.

Just put one electrode on one handle bar, the other electrode on the other:

The NIOSH states “Under dry conditions, the resistance offered by the human body may be as high as 100,000 Ohms. Wet or broken skin may drop the body’s resistance to 1,000 Ohms,” adding that “high-voltage electrical energy quickly breaks down human skin, reducing the human body’s resistance to 500 Ohms.”

Edit: I think we should be renaming it to the “Death Kart”

That’ll teach you not to smash the brakes. Until a genuine emergency, then you have two choices on how to check out.

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Dat seat cushion though…

That’s a prosthetic butt, Sean.

JAG “Artificial Assplants” MAN

Success! Drove the kart around the parking lot, only tested it out with 2 instead of 4 batteries, and the controller limited to 200 amps instead of 300 (max motor is rated at for short durations) or 400 (motor would probably handle it as long as you kept an eye on the motor temp, would probably blow 400 amp ann fuse). But still hit 31 mph, which is faster than you should want to go on unbalanced hand dolly tires.

Of course the big limiting factor with the kart will be that it takes 3 hours to recharge to get ~15 minutes of drive time, and you can’t trickle charge or leave the lipos charged for later, and you have to swap out each of the 4 batteries on the charger every 45 minutes.

Some things to work on:
Need to check all bolts / screws for loosening, the front left steering attachment screws may have backed out (hopefully they aren’t stripped)
Need better battery mount
Need to analyze steering geometry to see how much correct Ackermann would improve turning radius, or does solid axle = it wont turn much ever

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Also the kart weighs 124 pounds(not including 8 pounds for 16ah of batteries), most of the mass being the motor, rear axle, steering, and 20 feet of 2x4

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The bench test from last night, the speed wobble isnt as bad when considering they are $5 wheels

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Can we glue weights to the hub to balance them better?

In theory maybe, but the rim itself may not be centered perfectly, I hand milled each half of each rim separately to bolt them to the hubs. In practice I didnt notice vibration while driving, just looks vad when kart is teetering in air. To get balanced wheels would just need to spend the ~200 to get actual GoKart wheels

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Part of the problem is the rear axel is solid (no differential) and probably is not perfectly straight and is flexing. No amount of balancing is going to correct that. You’d need a very straight, strong axel plus numerous bearing supports to reduce flex, perfectly perpendicular hubs, straight and true hubs, etc. Then you can balance the wheels.

When watching the video you can see the various items flexing

Turns out that $5 hand dolly tires are not the most durable, after ~5 minutes I had a blowout by wearing through the tire and rupturing the tube, luckily we had an extra set of dolly tires to replace the destroyed ones with. The massive amount of understeer doesn’t help, was trying to find max cornering Gs and ended up destroying the front tires.

Other than that the testing at 300 amps went great, got about 10-15 minutes of drive time with different people getting to test it out. Only after testing did I realize that in the controller programming I had left the throttle rate at 12% instead of jacking it up to 100%. That causes a delay between giving it full throttle and the controller ramping up to max power, so I wasn’t able to do any burnouts today, but at 100% throttle rate for the next test I might.

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Now the question is if we should spend $80 on these tires, which would use the same crappy stamped split rims we already have

http://www.northerntool.com/shop/tools/product_200331472_200331472

Or try to find some used racing gokart wheels/tires (wheels must be american bolt pattern, 3 1/4" bolts on 2.5" diameter circle to fit our $50 aluminum hubs) like these

http://www.ebay.com/itm/Go-Kart-Wheels-Go-Kart-Tires-Radio-Flyer-Wagon-Tires-Racing-Bar-Stool-Tires-/311408027807

Well… are you going to be burning rubber or legit racing?

I don’t think anything on that go kart would pass qualifying so cheap one would seem to be the better option.

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Just for burning rubber, we only have ~1/6 the power of that kart, I found these slicks on ebay for $52 (76 shipped) instead of $80 + tax from northern tool, so I went ahead and ordered these

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Some gopro footage of the test driving today with the last of the hand dolly tires we had, ordered some 10" pvc pipe so we can test it out in drift mode next time.

(This is $5 hand dolly tires getting destroyed, not the slicks which came in but haven’t been put on kart, need to alter the spindle/steering arm by bolting a plate to it and moving the tie rod attachment inboard to add in some ackermann)

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Great video. Evidence that I did run into the rc track. The steering with a touchy throttle was quite an interesting experience. The electric acceleration is so much fun! I’ll post my video soon.

Here’s another video of the testing:

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