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UnaClocker
Apprentice Modder

Port Orchard
WA
USA

94 Posts

Posted - 08/31/2007 :  22:26:46  Show Profile  Send UnaClocker a Yahoo! Message
You know what I can't seem to find on the net? A good electric Go-Kart forum. So my new project is just that. An electric Go-Kart. I scored a beat up old Go-Kart frame on Craigslist for $25. It was really just a frame with the steering setup, steering wheel and a seat. Well the seat was too big for my kids, so I bolted in an old kid's car-seat. Nice 5 point racing harness and great lateral support now. haha.. :) I picked up 4 tires at Harbor Freight for $4 a piece. I ordered a 350watt motor from TNC Scooters, as well as a speed controller, throttle, and sprocket. I picked up a pair of 12v batteries, the motor is a 24v motor. I'm really not sure how fast the thing is going to be yet, hope to have it mobile by the end of this 3 day weekend. It's really helping me to improve my welding skills. :) I need to build some kind of box for the batteries, I have a great spot for them behind the seat, and I want to mount them low in the frame, like an inch or so off the pavement to keep the center of gravity nice and low. Maybe we should have an electric go-kart section on this forum? That'd sure be nice, the people here are great, very level headed unlike many of the forums I frequent. Anyways, hope I'm not too off topic posting about this, I had to tell someone. :)

Batteries Included
Senior Modder

Deltona
Florida
USA



1474 Posts

Posted - 09/02/2007 :  07:37:25  Show Profile
That is very cool. I am with you, brother. I have a similar project that I am working on, but I will be lucky if I get it done by Christmas. It is for my son.

It's my Little Deuce Coupe...You don't know what I got.
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UnaClocker
Apprentice Modder

Port Orchard
WA
USA

94 Posts

Posted - 09/02/2007 :  09:39:45  Show Profile  Send UnaClocker a Yahoo! Message
hehe, I move quickly on my projects, or they never ever get done. I "finished" it yesterday. I say that because for one, it has no brakes right now. Not even motor based braking yet. I'm going to work on that today. But that didn't stop me from placing my son into it and zipping around the block a couple times last night. It's very quiet. Clocked it at 9mph on the Hotwheels radar gun, but that was on level ground, going downhill, I think it hits 15 easily. Then there is the battery tray, I got it all welded together, but just barely, ran out of welding rod, so I couldn't attach it to the kart the way I would have preferred. But then, I don't really want to attach it just yet. I bought a live axle for the back end of the cart, it had a solid rear axle when I got it, and the tires I picked up at harbor freight can't be adapted to a live axle very easily (seriously don't know how I'd do it). So the kart is 1 wheel drive right now. It's fine on the pavement, you'd really never know it was 1 wheel drive, but leaving my gravel driveway.. It won't do it on it's own.
#25 chain is TINY! It's smaller than bicycle chain. The motor was only offered with a #25 chain sprocket, so I went ahead and got the #25 drive sprocket and some #25 chain. If I can find a #35 chain sprocket for the electric motor, that opens up the ability to use standard go-kart sprockets, which gives me more gear ratio choices.
I also plan to setup a reverse switch today. The motor controller doesn't have reverse, so simply using a pair of relays, I should be able to reverse the motor polarity pretty easily. I can just take 2 12v relays, run their coils in series with each other, and they'll be able to be energized right off the 24v. What would be nice is a momentary push button that enables reverse. So you only go backwards while holding the button, which will keep the relays from being left on.
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swhenrik
Moderator

Pengilly
MN
USA



4067 Posts

Posted - 09/04/2007 :  06:54:24  Show Profile  Visit swhenrik's Homepage
Sounds like a pretty good start! You gotta get some pics up for us to see!
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gameboy
Moderator

just north of austin
tx
USA



4796 Posts

Posted - 09/04/2007 :  08:37:15  Show Profile
hey, if you find a 35 sprocket for the motor and a bigger one for the back can you list your source, i am having trouble finding what i need for my tractor project.

thanks




free is always better


beatle
Fisher-Price Lil Kawasaki
small motor cycle
old ninja super shock
old jeep wrangler 18v
old ninja quad 18v
2extreme machines 18v
gator
yellow goucho
brand new jeepster 800 watts
razor e-300
pukka

and yes this is becoming a problem. wife has threatened divorce.-- she'll come around.
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swhenrik
Moderator

Pengilly
MN
USA



4067 Posts

Posted - 09/04/2007 :  09:12:04  Show Profile  Visit swhenrik's Homepage
I was just thinking... if you go with the larger size chain (#35 instead of #25), a sprocket with the same number of teeth is going to be bigger. Is that going to be an issue for clearance on the rear axle, or limit your gearing options?

I read somewhere that the #25 chain isn't a roller chain, is that true? And the #35 does have rollers, right?
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UnaClocker
Apprentice Modder

Port Orchard
WA
USA

94 Posts

Posted - 09/04/2007 :  20:58:39  Show Profile  Send UnaClocker a Yahoo! Message
Not sure about #35 chain being better than this #25 I have. This stuff seems to be identical to normal bicycle chain (which I'm guessing is #35), just smaller. I will definitely keep everyone posted on what I find for gears. Yeah, #35 would be bigger, I guess you could keep the final sprocket size down by making the primary a different size.
I have found one minor problem with this thing.. It won't fit into the trunk of my car anymore. Very hard to take it anywhere to ride it. There's a school parking lot a couple blocks away, we were just forced to drive it there and back over the weekend. I took some great action shots, which I'll post here. I'll snap some close-ups to show how I did things (like the gas pedal) in the next day or two. I even wired in reverse using a pair of relays. The speed controller I bought didn't have reverse, but as I said in my last post, a pair of 12v relays in series solves that problem.
I want to power up the headlights on the thing, but I want to put some much lower wattage bulbs in there first, maybe some like 5 or 10watt side marker bulbs, so they don't drain the battery down for no reason. And they'll have to be wired up in series as well.

This was the frame when I brought it home.
Here are some shots of it in action over the weekend.



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gameboy
Moderator

just north of austin
tx
USA



4796 Posts

Posted - 09/04/2007 :  21:31:00  Show Profile
OMG! too funny, using the car seat is classic. that had to be stroke of pure genius.

most of the older carts like that used a paddle that pressed against the tire to cause friction as a brake, that might be the easiest way to do it. or you could go all out and get dual calipers for the rear and do it that way.

nice job.

oh, i just remembered, on my jeepster i have noticed that if the power is fully cut to the motor and controller that the motor acts like its shorted out and brings the whole thing to a stop rather quickly, not as good as the power wheels but pretty quick with out the use of brakes in that respect. just food for thought. good luck.







free is always better


beatle
Fisher-Price Lil Kawasaki
small motor cycle
old ninja super shock
old jeep wrangler 18v
old ninja quad 18v
2extreme machines 18v
gator
yellow goucho
brand new jeepster 800 watts
razor e-300
pukka

and yes this is becoming a problem. wife has threatened divorce.-- she'll come around.

Edited by - gameboy on 09/04/2007 21:33:50
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Kirky_Turky
Journeyman Modder




148 Posts

Posted - 09/05/2007 :  07:47:09  Show Profile  Click to see Kirky_Turky's MSN Messenger address
might not work, cuz the motor isnt really geared down, but why not try using a power wheels set up in it? for the brake, thats what i did with my big foot



WOOT! fun xD
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UnaClocker
Apprentice Modder

Port Orchard
WA
USA

94 Posts

Posted - 09/05/2007 :  09:29:07  Show Profile  Send UnaClocker a Yahoo! Message
Yeah, I think I probably will just try shorting the motor to slow the thing down, just gotta setup a brake pedal and some relays to do that.
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swhenrik
Moderator

Pengilly
MN
USA



4067 Posts

Posted - 09/05/2007 :  10:52:10  Show Profile  Visit swhenrik's Homepage
This would have been a good project to use the Curtis 1505 with regenerative braking, although it's a bit spendy.

I'd try to find some good power resistors for the braking, as the speeds will probably cause quite a bit of heat. One idea I had was to get the heater control resistors from a junk car, they are large and open for good cooling.
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UnaClocker
Apprentice Modder

Port Orchard
WA
USA

94 Posts

Posted - 09/05/2007 :  15:56:52  Show Profile  Send UnaClocker a Yahoo! Message
I have 4 8ohm 20watt resistors I had picked up to use with the injectors on my car. Ended up not using them, but I imagine they might do the job nicely, wire them all in parallel so I get 2ohms, 80watts. Not exactly the 350watts the motor is rated at, but they'll be used for such short periods of time, I imagine they'll take it just fine.
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Grant
Senior Modder

Brisbane
Queensland
Australia



1820 Posts

Posted - 09/05/2007 :  18:09:17  Show Profile  Visit Grant's Homepage
That is pretty awesome, great work, I have always liked Go Karts. I purchased myself one a while ago so I would ride with my son. My son is constantly wanting to drive it, which he has done a number of times, however he can not reach the pedals so can not go full speed or use the brakes. The drum brakes are actually from a scooter although I think I would prefer disk brakes.


I am now looking at upgrading it again with a 750-1200Watt motor as the 350Watt really limits the performance with my weight.

The 350Watt motor was more than enough power for my son though and should have been able to propel him to 24kph/15mph if you extrapolate the performance stats that were recorded.

I also wrote a review on the Go Kart that can be viewed here.

http://www.modifiedpowerwheels.com/forum/topic.asp?TOPIC_ID=555



http://www.youtube.com/GauchoDrift
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UnaClocker
Apprentice Modder

Port Orchard
WA
USA

94 Posts

Posted - 09/05/2007 :  20:27:00  Show Profile  Send UnaClocker a Yahoo! Message
Well I didn't get around to doing brakes today like I had planned. Instead I started thinking about how I could get it to go faster. Semi conductors aren't perfect conductors. They have a bit of a voltage drop when power passes through them. So I started wondering how much power was being lost through the speed controller. Checked the battery, 25.3v, ran the motor at full throttle in the air, battery voltage didn't change much. Checked the voltage going to the motor at full throttle, was about 22-23volts. Just like I suspected. Well the motor is rated 19.2amps, that'll work fine with a Bosch relay. This time I only wanted to run 1 relay, so I did a test, and go figure.. Those darn Bosch relays are built like tanks. I already know they'll trigger just fine at 6volts or so, from my past power wheels experiments. And go figure, it works just fine at 25.3volts too! Even for long periods of time (did a 5 minute test). So I installed a push button momentary switch on my throttle stop (couple zip ties and some JB Weld), so now when the throttle is all the way down, the motor gets FULL voltage and current. Works great, my son accelerates much faster now. He wasn't in the mood to go very fast today though, so I didn't get a chance to clock it and see how much faster it is now.
http://www.youtube.com/watch?v=nZwUS8dEhl0 Here's a video demonstrating the throttle improvement.
http://www.youtube.com/watch?v=887EUTbPXsg Here's a video from this weekend, the first trip to the local parking lot, my son and nephew riding it.
http://www.turbododge.info/gokart/ And here are some closeup pictures of the finer details, like how I setup the throttle.
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swhenrik
Moderator

Pengilly
MN
USA



4067 Posts

Posted - 09/06/2007 :  07:44:07  Show Profile  Visit swhenrik's Homepage
Those resistors you are talking about sound like they should work. Maybe set up the pedal so it uses the resistors pushing part way, but pushing further will give a direct short of the motors in case the resistors fail.

That's a VERY noticeable difference when bypassing the controller. Maybe everyone running one of these controllers could follow your lead for major performance gains! I was wondering if some are better then others, which controller are you using?

I was wondering, does the twist throttle turn OK with the hose clamps around it? On our Bigfoot, with a string pulling it, seems to sideload it enough to turn hard.

Is it comfortable to push the pedal that far? Maybe a linkage could be set up to reduce the pedal travel (angle)?

The steering stem support hoop, is that how the go-cart came? I was just imagining a crash (I'm always worried about stuff like that with my kids), the driver's legs are pinned under that hoop, essentially stuck in it if it rolls.
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UnaClocker
Apprentice Modder

Port Orchard
WA
USA

94 Posts

Posted - 09/06/2007 :  12:10:14  Show Profile  Send UnaClocker a Yahoo! Message
I think the only way a controller could get around that problem is if it had an internal relay. The controller I'm using came from TNC Scooters, if you scroll through their selection, I got the one that supports motors from 350watt to 750watt. The kids don't seem to have any problem pressing the pedal all the way down. I've had about 7 different kids ride it now, the biggest one was 10yrs old, and he drives like me, with his legs on the outside of the steering loop. It fits him perfectly when he drives it like that. Don't see a need for a linkage, I prefer to keep things simple, and this is definitely simple. I set up the pedal stop so that the pedal couldn't be pressed far enough to damage the rotary controls. And yeah, it twists very smoothly, at first I overtightened the hose clamps, and it wouldn't return after pressing it down, loosened them just a hair and it's butter now. Comes right back up like there's nothing on it. Definitely no sideload problems AT ALL, it really is a feather touch to move the thing. The pedal itself is just an old aluminum heatsink I had laying around, drilled a couple holes for the hose clamp to pass through, and mounted the whole setup on a socket that it fit snugly on with a bolt welded into the socket. Welded a nut to the frame and screwed that socket/bolt into the frame.
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swhenrik
Moderator

Pengilly
MN
USA



4067 Posts

Posted - 09/06/2007 :  13:06:07  Show Profile  Visit swhenrik's Homepage
In some of the reading I've done about PWM's, they talked about some controllers not being able to run the pulse width over something like 90% because of the timer they used for the trigger. According to this source (I forget where), other designs are able to get to 100% pulse width. I'm not saying zero losses, but the difference in your video was HUGE, seemed more like it was running at 90%. And if they all had that much loss, you'd think they'd come with a bypass relay as part of the circuit like you mentioned.

350 to 750 watts sounds like the LBD14.

If the angle of travel of your pedal works for you, then no, don't change anything. I try to keep the pedal setup so your heal can stay on the pedal when fully released, and push all the way, being comfortable the whole way, and I couldn't tell if yours was like that or not. The issue of the pedal looking like it lays down so far at full throttle probably isn't a problem cuz your knees are also higher in that sitting position.

I wish our Bigfoot pedal was smoother. The amount of drag is quite noticeable, where it's hard to push and just barely returns on it's own. Maybe I have my hose clamp holding the pull string too tight?

Having the driver's legs on the outside of the hoop sounds much safer.

Edited by - swhenrik on 09/06/2007 13:07:22
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UnaClocker
Apprentice Modder

Port Orchard
WA
USA

94 Posts

Posted - 09/06/2007 :  16:12:28  Show Profile  Send UnaClocker a Yahoo! Message
Yeah, my pedal is definitely not ergonomic, it's straight up at rest, and yeah, it goes quite a ways back. But it is useable, so that was my goal. :) Interesting info about the speed controller, I figured there were some kind of shortcuts in there for it to be so cheap. If you (or anyone else reading this thread) decides to do this, the speed controller gives the motor full positive at all times, it does the PWM on the negative side of the circuit, so if you supply the motor with ground at any time, it's going to go full speed. Found that out by accident after I hooked the battery ground to the frame, and went to install new bulbs in the headlights.. Bumped the frame with the headlight housing, and instantly burned out the bulb (as well as spinning up the wheel for a split second)..
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swhenrik
Moderator

Pengilly
MN
USA



4067 Posts

Posted - 09/07/2007 :  07:50:33  Show Profile  Visit swhenrik's Homepage
Thanks for the heads up on the polarity of the controller. The R/C ESC's work the same way, controlling the negative wire. Maybe it's a necessity of the design, and the MOSFET gates only work that way?
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UnaClocker
Apprentice Modder

Port Orchard
WA
USA

94 Posts

Posted - 09/07/2007 :  09:27:50  Show Profile  Send UnaClocker a Yahoo! Message
Could be, automotive fuel injection works that way too.
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UnaClocker
Apprentice Modder

Port Orchard
WA
USA

94 Posts

Posted - 09/09/2007 :  10:54:59  Show Profile  Send UnaClocker a Yahoo! Message
So I was driving the Go-Kart today, taking a nice leisurely stroll around the block with my 2 sons. The 5yr old was driving his powerwheels truck, and I was following with the Go-Kart.. Well that thing really doesn't like hills, but to get around my neighborhood, you pretty much have no choice, there will be downhill slopes, then uphill ones. Well on the second hill the thing virtually came to a stop. At the top of the hill, the motor was billowing smoke. Not a good sign. It was also super hot, probably near 160f. It still worked, so we continued our trip home, but I imagine I did some pretty good damage to the motor in the process.
In hindsight, I probably should have just gone for the 1200watt motor and undervolted it or better yet, geared it way down to keep the speed in check. Overbuilding is a good thing.
Anyways, it still works for the time being. I'll stop driving it, I don't think it'll take another trip.
Good news is I was able to drill a new hole on the steering shaft output, giving the steering more leverage, so the new steering wheel works great now. (It was quite a bit smaller in diameter than the original, the kids had a lot of trouble turning it at a stop, and steering accurately at higher speeds)
Earlier today, before I smoked the motor, we had the Kart up at the local school parking lot again, with the new throttle mod, I clocked it doing 11 on level ground, and 13 on a good downhill run.
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