building an electric gokart

[jerseyrider]

Hi,

New to the site

I am new to building gokarts and my son, who is 14, would like to build/assemble an electric gokart. Could use some help on what components we need.
We are starting with a YerfDog 3203. I picked one up for cheap that the guys was not using. So now need to convert the power to electric. Would like some suggestions on

• motor size and type
• controller
• what should I use for a pedal for acceleration or would you recommend a high medium low setting with the accelerator as the on/off
• would like a reverse switch
• I was thinking 36 or 48 volts
• son would also eventually like to put on solar panels
• chain and sprocket.

I am pretty handy electrically and mechanically. Own 2 electric bikes and 2 electric scooters. Also own a few ATV's and snowmobiles. Just never build one of these.

Any and all suggestions would be appreciated.

Thanks

 

[dcastillo]

Ill start with the obvious question before anyone else does
What are your goals as far as power, speed, run time, etc?
-Danny

 

[itsid]

A Yerfdog 3203 is fairly heavy (300lbs roughly w/o engine)

And if you plan to actually move two passengers (as it's intended to) you'll need
some serious motor power and worse a more serious amount of batteries (aka as "a lot of weight") to propell the kart for any decent amount of time.

Throttle: std foot pedal! No on/off crap; it'll make things worse!
Since you need a big motor anyways, you'll also need a controller to handle that..
most of which are indeed programmable (so the speed limiting isn't a big deal to do)

But be aware, that you will roughly spend five to ten times the money you'd spend if you opt for a gas engine (just saying)

A true go kart (that is a small buggy rather than a go kart)
single seated, no supsension.. a go kart.

Much easier, much cheaper to achieve electric conversion!

As a first guess: something in the 3000Watts range (output power!)

'sid

PS Solar panels only add weight, without any noteworthy benefit I'm afraid

 

[jerseyrider]

first fast is not the main objective but would not be bad. Maybe 25 MPH and one hour run time. This is for my 14 year old son and he is just interested in trying to build an electric goKart.

Mostly used for one passenger but if two my son weights about 125 and his friends about the same.

Throttle: so where would I get a foot Throttle?

What type of motor and what type of controller would you recommend?

We know it will cost way more than gas but it's a project he wants to do and will keep him out of trouble...that is priceless.

I let both of my kids do one project per summer. My older son, who is now 19 always did something mechanical. Rebuild a car, turboed his 2013 polaris switchback assault, etc. Now he is college studying mechanical engineering. As a freshman they elected him to be the chief tuner for his clean snowmobile (think high efficiency low pollution) club. well worth the project money I have spent over the years.

Not trying to build a true goKart but trying to start with the frame portion as we do not have welding equipment. the Yerfdog body was the easy way to start.

Yeah...I know solar panels only add weight but he thinks it's cool. Our last house in NJ we had 9.975 kW of solar panels on our roof. he thought it was cool that in the day time we did not pay for electricity. Can not do them in Minnesota where we live because we have too many trees. But he wants "free" electric so he wants to incorporate panels into his goKart. May not actually put them on the kart. may just develop a charging station. By the way this son wants to be an astrophysicist and travel through space using space time warp and solar power. So I figured might be worth it to help him start his dream.

 

[Wheelchock]

Electric Go Kart Drivetrain

I've attached some photos of a kart that I built a couple of years ago. My main focus was to pull the kids through the snow on their sleds as opposed to pulling them myself - avoiding a heart attack or something!

I find it under powered and my choice of batteries has it lasting less than an hour at any kind of fun speed.

With that said, it was still a fun build and I've used it for more than just a cart - it made a great powertrain for a parade float

In the photos you can see the layout of the controller, throttle, solenoids, batteries, etc.

 

[itsid]

That setup looks nice.. what's that a ME-09xx series?
Axe controller.. so apart from that club-car throttle pot box (which I really would'nt want to get wet...)
that looks like a nice package to me.
I'd rather use a 0-5V hall effect throttle tbh..
IDK.. like this for example:
http://kellycontroller.com/simplified-5v-throttle-pedal-p-1028.html
And as you know the AXE will take almost any input as a throttle signal.

I'm not sure the batteries there would last an hour.. certainly not if you go full throttle

Anyways..

That setup is in itself sound and looks nice, so just replicate that;
add a second contactor for reversibility and you'd be good.
(or is that AXE internally reverseable?)

And for mileage... you should have some values to work from if you made some setups like this..
so you'll know better what to expect from each pack of four batteries than me.
as a guess... 80amp constant draw for the motor.. 76Ah cells;
controller undervolt protection enabled that's ~ 45mins max

Oh just one thing: as much as I personally like single wire colors all around (keeps you alert when messing with it)..
it's not good practice, so if you make one with your son, use mixed colors for simplicity and added safety

Also it's better to add some water protection to the battery terminals and keep the controller in a splash proof case, especially if it's close to a wheel

Oh and yes.. a solar panel charging station is nice...
maybe to charge a second set of batteries when the kart's out for a ride

'sid

 

[jerseyrider]

Wheelchock -- Could you list out the exact components you used That setup looks very nice and like you mine is more for fun and working with my son than anything else.

Also looks like the axe controller would allow me to use my foot pedal?

itsid -- if I use the footpedal you recommended do I use a different controller or could I use the one that Whellchock used.

You guys are great thanks for the help. Going to try an order some part once I hear back from you.

THANKS

 

[itsid]

that AXE controller will work with the pedal I linked.

But, it's not cheap; so compare prices with kelly controllers;
they'll do just nicely and are most of the times cheaper than any competitor.

they also have motors listed like the one Wheelchock used:
http://kellycontroller.com/mars-0708etek-comparable-brush-type-pm-dc-motor-p-38.html
(and they tell you which controller is a good match as you can see )

but keep your eyes open... sometimes parts show up on ebay or so..

'sid

 

[jerseyrider]

Thanks for the link.

looks like I can get the motor, controller, and foot pedal from them.

Any specific place you recommend for gears/sprockets and chains? Can I use the one that came with the yerfdog? It has a large sprocket on the
axle

I know these may sound like basic questions but first time building anything with electrical motor

Thanks

 

[itsid]

I can't tell what the yerf dog came with tbh (sprocket wise) "large" is not enough info I'm afraid

I think roughly 9:1 will be a good ratio
(ie for every tooth on the motor sprocket you'll need nine on the axle sprocket)
that is if we talk about the 20" rears it came with originally.


I'd go for #40 chain and sprockets (NOT #41!)
or 420 if I have the choice...

'sid

 

[jerseyrider]

Sorry about saying large.

has a 60 tooth sprocket on the axle and 10 tooth on the motor side. come with a #40, 70 link chain.

 

[Wheelchock]

One thing that I found difficult was finding a sprocket that had a 7/8" bore (motor shaft) in go-kart sizes. So I went ahead and used the jack shaft arrangement that came with the kart and used chain and sprockets more suited to industrial applications on the motor end that were readily available locally as well as online. Since the sprockets were relatively inexpensive, I bought a few different sizes to experiment with. Since the chain came longer than I needed I also bought a few extra master links. So for each sprocket size, I have a chain that is already the right length.
For reversing, I just used an EZGO golf cart manual reversing switch (see photo). However, a reversing solenoid arrangement is nice too.
I bought the motor and controller as well as most of the electrical components from EV Drives http://www.evdrives.com/Default.asp
I already had the controller and everything else but the motor from a different project. I went with the Montenergy ME-708.
As I mentioned, I originally built it for snow and it hasn't snowed in Seattle since February 2014 - Maybe this winter.
I did use the cart and some cowling from some old computer consoles and built a spaceship for the local UFO festival.

 

[itsid]

Sorry about saying large.

has a 60 tooth sprocket on the axle and 10 tooth on the motor side. come with a #40, 70 link chain.

No Problem..

6:1 isn't going to cut it.. the 3203 came with a Torque converter
(means it had an overall ratio of 16.2 : 1 at take off)
And while you surely can gear lower with an electric motor (since there is no belt or clutch to burn)
I do not think 6:1 will do with the motor I linked you to.
(I could be wrong though since in the end the 0708 peaks at nearly 15kW... three times as much as the engine the yerf dog came with...)

But if I had to make a guess.. if you try to go uphill or even start uphill, thanks to the 20" wheels.. you'll quickly overheat the motor (and it'll shut down completely to selfprotect)

So yeah.. 9:1.. maybe 8:1 will suffice.. but personally I'd rather dial in on the safe side.

But let's ask Wheelchock

Wheelchock, what's that toothcounts you have there?

[EDIT]
Oh and one more question:
have you swapped your fan to the unidirectional one?
since the original only cools in CCW mode...
or is the short reverse maneuvering not severe enough to heat the motor?

'sid

 

[Wheelchock]

On the motor end, I had as few as 12 on the motor and on the jackshaft 18. That's along with the 10 and 60 on the wheel side, so - 9:1. There was plenty of torque, not much speed. Also, I found that the 12 tooth was so small that there was a lot of noise. probably because both sprockets were so small and there is more chain contact with the sprockets. With a small sprocket driving a large one, that doesn't seem to be the case such as the 10 to 60 end.
I then went with 18 and 18 on the motor end taking it up to 6:1. There was adequate torque and the speed was better - As I recall I was paced at about 22mph. I weigh 230 pounds.
Still overall, it wasn't a speed demon like I've seen in some of the you tube videos. Keeping in mind the original project was to pull kids on sleds or tubes in the snow, it should be fine if it ever snows.

Sid, as far as the rotation. I don't recall any fan issue. Reverse is only used intermittently, so heating wouldn't be an issue there. I'm curious now and will go take a look at the fan arrangement.
There were instructions for adjusting the endbell for opposite rotation. I'm pretty sure that the adjustment shifts the neutral for commutation. It's been a while since I looked at the instructions that came with the motor.

 

[jerseyrider]

So I have order
- ME 0709
- Alltrax SR-72300
-SW180 solenoid for 48 volts

This set-up lets my son go to 72volts later if he really wants to

I order a SIMPLIFIED 0-5V THROTTLE PEDAL that itsid recommended.

Wheelchock -- I saw you had interstate batteries. Which ones where they?

Guys -- any recommendation on a charger?

Thanks

 

[itsid]

ha.. see.. thanks Wheelchock;
I thought 6:1 is too demanding on 20" wheels.. wait.. just to make sure.. what's your wheelsize there?
Since that is an important part for gear ratio as well..

your 22mph top speed suggest you run wheels closer to 14"-15"
(assuming the 0709 runs 3250-3500rpms @48V)
which again affects the necessary ratio for jerseyrider's wheelsize ( and we're back at 8:1 mathematically)

'sid

 

[Wheelchock]

Yes, an important piece. 18" tires.

One thing that I did when programming the controller is set output to 75% as suggested due to the low inductance of the motor. Apparently the controller can see that as a short circuit if the inrush is too high. That may account for the top speed being a little less.

 

[jerseyrider]

where did you purchase the motor bracket or did you have to have it custom made?

What batteries did you use