Kids kart

[jorge0136]

I am interested in building my niece and nephew some sort of wheeled machine. I have several engines I could use but would very much prefer an electric drive. It will be quiet and much safer than the engines I have. I have burned myself too many times as a grown adult on engines to let some small children around one. Also I like the simplicity that they could go flip a switch on and if it were charged, take off in the thing.
I would like to design a drive that I can scale up over time to match their age. What sort of motors should I be looking out for? I have a basic grasp of electronics but am not sure what controller I should be using.
Any help would be much appreciated. Thanks.

 

[oscaryu1]

How much do they weigh? Below 100, I'd use a 60-70 tooth rear sprocket, and a 300-500 watt motor.

Plenty of torque for all those hills or driveways (a 250W couldn't cut me, even with 12V of extra power).

One seater, I'd recommend this combo:

24V 300-350W Motor, 36V controller, and 3x 7/8aH batteries.

Two seater:

24V 380W-500W Motor, 36V controller, and 3x 12aH batteries.



However, these would be powerful enough for an adult to ride.

I generally take electric go karts and electric scooters to "another step", so...

If this is for 2/3 year olds, take it down to 24V. If they're older (10-13), then I'd go with the 36V for the extra speed.

They will be doing around 20MPH with a 24V setup, and about 25-30MPH maxxed out with a 36V setup (overvolting the motor).

 

[frederic]

Any help would be much appreciated. Thanks.

You're welcomed to leach whatever ideas you like from the one I built my son, who was three at the time.

CHASSIS - BODY

And here is a youtube video of his first day testing driving. The first minute or so is just the build pictures flipping through, but after that you can watch my son drive into the shrubs without looking where he's going, and finally at the end he's doing donuts It has a 500W scooter motor with a build-in speed controller, and the speed adjustment is underneath on the chassis where he cannot get at it. The pedal simply applies and removes power, and the knob remains constant. This is how I controlled his speed early on before he got the hang of starting, stopping and steering. It's a simple 5K potentiometer mounted on teh chassis underneath the body. I also have a keyswitch there so he can't make it move without me allowing it.

Youtube Video: Homemade Electric Toy Car

While the chassis was gross overkill it made up for the wooden body and survived nine head-ons with big trees.

Here are some ideas you may wish to incorporate, if your child is as young as my son is.

1. Integrated braking. If powered by an electric motor, you can have one pedal operation. Push pedal and go, release pedal and brake. The pedal drives a relay which applies power to the motor, and when released the relay "shorts" the motor (+) and (-) power inputs and the motor acts as a brake.

2. Integrated remote kill. Using the electronics of a simple remote control (forward and reverse/turn) I have a single button remote that at a given moment I can push and the car disengages power to the motor and shorts it like above - great for when they don't listen and buzz right down the driveway towards the street.

3. Seat and safety belts. I didn't get this far on this project, but an old car seat with some trimming makes for a great safety seat. While you want your child to have fun, you want them to live another day. Especially when they make a bee-line towards large rocks, trees, and vehicles in your driveway.

4. Make a chain guard either out of metal or with the body that you build, if you're building a body.

5. Integrate a seat switch like a riding mower. If your child stands up, no power is applied. My first attempt at this was to disengage power and short the motor input like above however I found if son lifted his butt off the seat it would brake abruptly and he'd go over the front of the car, so I changed it to just disengage power so there's no abrupt movement. Of course a carseat with harness would eliminate the need for fear of standing up. But it would keep his/her fingers out of moving parts, as without sitting in it there are no moving parts.

Hope that helps. Since he outgrew this car, I'm welding together version II - bigger, badder, more aggrevating. He's currently 4-1/2 and already drooling on the 4 HP electric motor slated for this.

 

[jorge0136]

So let's consider the children first:
Niece 4 years old.
Nephew 2 years old.
Thusly
-Two seats.

-Potentiometer that I can switch depending on who is driving and adjust with age over time.

-overbuilt frame sounds safe.

-integrated brake, I will have to ask how to wire the relay when I get to that point. Would this work with a more powerful motor than what you put in your kids kart? Speaking of which what motor did you put in the kart?

-Remote kill again I will have to ask for advice later.

-Find seat belts that have a switch that disengages unless they are plugged in. Wire that to the ignition and we solve the standing up problem. If I can find the belts.

-24V 380W-500W Motor, 36V controller, and 3x 12aH batteries.

Now what sort of machines should I be looking for to pull a motor like this off of? I am a craigslist shopper and prefer to recycle something if I can help it.
If I find something like a scooter with a built in controller can I still over volt the motor or at that point do I need to get a new controller?

-Develop some sort of body for it, incorporate a chain guard.

One of the local junk yards allows me to pick mildly used but still usable car batteries for about $10. Would that be a decent way to go with? I googled the average a/h rating of a car battery is 50 a/h. Two of these should work right? Three if I want 36 volts.

I should be looking for something like this right?:
http://www.scootercatalog.com/electricmotor-15.html

Beautiful build Fredric, very well done. Thanks for the snappy response.

 

[jorge0136]

Update!

Ok I have been looking at this motor.http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&item=260456094858&ssPageName=ADME:X:RTQ:MOTORS:1123 500 watt, with the sprocket for $30, almost sounds too good to be true. I had to actually ask the guy for the wattage of the motor it never says exactly on the ebay page. Just occurred to me I was so stuck on the wattage I forgot to ask him what voltage they were.

Alternately mattlepperd is selling a couple of motors described here http://www.diygokarts.com/vb/showthread.php?t=3725

As far as the rest of the kart, I think I may have scored on that portion, at least on parts. I found this on my local craigslist. I am hoping to be able to salvage the steering, wheels, axle and part of the frame off of it. Looks to have a engine of some sort on there too. http://seattle.craigslist.org/tac/mcy/1316754986.html Being craigslist, I still need to go look at it. If it's half what I hope it should be a good deal.

 

[jorge0136]

Well I went to look at the kart and the person selling the kart wasn't at home but told me to go ahead and look at it down the alley there. He didn't warn me about his dogs. Luckily they seemed to like my smell as I still have all my limbs.

The kart itself is beat. It appears that the only part that would 100% be of use will be the tube frame. The wheels and tires are all worn as are the hubs. The back axle is only attached to one wheel. The other wheel seems to be on a hub, with it's own bearing. while in the midst of seeing that one wheel is held on by a nut welded to the axle a group of kids coming riding up on bikes looking at me expectantly. Turns out the person selling the kart couldn't have been over 12 years old.

After talking about what else had gone wrong with the kart, like bent spindle arms and a nut missing on the king pin, he says that he would take $40 just to get it out of his yard. I figure I can if nothing else have saved myself a little bit of money just on steel. Loaded it up and off I went. I am thinking I am going to chop up the steel and weld it into a different configuration. For one I need experience actually building a frame and this one isn't the right shape for kids to cruising about in.

The karts tires on the front have some significant negative camber. The tread is nearly new on the outside and almost worn through on the inside. Like this:

 

[frederic]

Buying a used kart is a great way to save money and time, even if all you do is strip it for the good parts and rework the bits to your liking.

You don't have to create a body and a chassis as I have, I did that for a particular reason - my son wanted a blue car, and a red fire truck, and a white ambulance. By having the body easily removed and installed (four bolts and two electrical connectors) this allowed me to make as many bodies as he wanted and it can be anything he wants, anytime. I thought this was less aggrevating than making two, three, and four karts.

As it turns out, he outgrew the blue car before I had a chance to make the additional bodies.

$40 is a good score on what you got. That's about what the wheels/tires are worth plus you got bearings, axles, a seat, steering wheel and steering shaft, and so on.

An open kart is okay however with my son I worried about him reaching behind him and touching a moving tire. My son's really curious about how things work and I worry about his little fingers.

 

[Kaptain Krunch]

I've nicked a tire with my elbow before, not fun...You definitely got a good deal though, the back tires dont look too bad.

Also, if you need any cheap switches or connectors, i got plenty from sleds, riding mowers, dirtbikes etc.

 

[brendonv]

You could always leave it as a 2 seater and put another steering wheel in that is fake. That way the lil 4 yr old can drive and sit next to her brother who can pretend to drive as well. I dont think i would let a 2 year old drive a go kart. It wouldnt cost much to do, just weld in 2 lil bars, a lil shaft and whack a steering wheel on it. Then he can have fun too. U could also make it so its just a bolt in so if u drive u can take it out. Seems like i nice kart, well done. All i would do to it would be, put a floor in it and pad that seat. U can pad the sides as well and put in a seatbelt so the lil kiddies dont fall out.

 

[frederic]

The fake steering wheel is a great idea Brendonv, I like it!

A good source of a "seat belt" is the 5-point harnesses that's on every baby seat. People toss the seats into the trash all the time when their kids no longer need them.

 

[jorge0136]

I think you guys convinced me to use the existing frame. I will need to relocate the steering wheel. Speaking of steering, as it is now the spindle arms are bent and it requires too much effort for a tyke to torquing around. If I make the spindle arms longer that should help some of the problem right? Also if I shorten the lever arm that connects the steering shaft and the tie rods I think that would also cause it to decrease the effort on steering. Are photos necessary to illustrate what I want to change? It gets easier to drive the faster you go but it will not move that quickly.

I love the second steering wheel idea! Thanks Brendonv.

The 5 point harness is a clever plan too, I'll have to start looking for some of those. Thanks Frederic.

The wheels, hubs and bearings on this kart all seem to be bent, worn or somehow messed up. I don't think it should matter with the speeds we are talking about here though. Perhaps the wheels, we will see how it steers.

I like the idea of a body mostly so the kids are isolated from as many moving parts as possible. Additionally they are all about the idea of a "shark car" We will see how much energy for this project I have after I finish the drive systems etc...

I was thinking that I can pick up the adjustable rails from a car seat or van seat and attach a seat to that. That way I could push the seat back if I wanted to drive. Avoid bolting and unbolting it all the time.

Kaptain I might take you up on some of those switches, let's see what I need first.

Thanks to everyone for the ideas!

 

[frederic]

You're welcome for the harness idea. I see baby seats at the curb quite often and have grabbed a few myself, leeched off the harnesses, then put the at my curb ;-)

Here are two pictures that might help you see what I did to isolate my son from the moving bits. This was originally supposed to be a pickup truck (yeah, sure, right) and the truck bed floor covers the motor, chain, and other finger-eating bits.

 

[frederic]

And this final one shows the body floor, with the motor bits sticking through, and why I covered it with the floor of the body.

Hope that helps.

 

[Krustalien]

That was a rather large bump, although quite a pretty post, so I guess it balances out. :arf:

Anyway, to anyone still looking to make an electric kart, I strongly recommend this forum: http://www.fightingrobots.co.uk/forum/index.php

It's a combat robot forum, largely English but still very useful. By combat robot I mean the things you used to see on "Robot Wars" and "Battlebots". They build from 160g (0.35 pound) antweights to huge 100kg (220 pound) heavyweight monsters. All the robots use ESCs (electronic speed controllers) and everyone on there is very helpful, and even if not for a robot they'll happily recommend heavy duty motors and ESCs.

Just thought it could help.

 

[fowler]

please dont wirte on posts over a year old.
for that matter dont wirte on posts 3 months old.

 

[redsox985]

Pedal go karts man. If you look above a person's name in the post, you see a date. That's the date they posted that comment. Please, to preserve my sanity, do not reply to a thread that's more than, like Fowler said, 3ish months old. Start your own thread and include links to other threads, if needed. Also, this is not an advertising site for your personal benefit. I understand that it may be your main, or only, form of income, but please don't. Thanks.

 

[Krustalien]

Wait what? That site isn't mine nor is it my only income, I'm 14. I posted it because everyone on there has years of experience when it comes to electric machines. I realised there was a bump, a big one at that, but I thought if I post something relevant then it's not all bad.

Or have I missunderstood something and you weren't referring to me?

 

[fowler]

it may be very relivant but u are 1 yr late.
chances are if this person hasnt solved the problem yet then he has sold the kart

 

[redsox985]

KefuiePedalGoKarts is the one who bumped it promoting his "cup of tea". Krustalien, your fine, your not the one who replied to a year old post.

 

[Blazkowiez]