Electric Kids Kart Project

[Benmitchell423]

Hi all,

Sorry total newb here. Trying to get my head round building a couple of little buggys for my two kids. They are only small under 8 and just want a fun buggy for them to whizz round the garden in. I have thoughts about the fabrication and physical build but am a bit green when it comes to powering the thing.

I have read through this part of the forum and think i get the basics but have some key questions.
1.as they are only small and light, and performance is not the be all and end all, would the following motor be sufficient to power the thing?
http://www.ebay.co.uk/itm/162175409684?_trksid=p2060353.m1438.l2649&ssPageName=STRK:MEBIDX:IT

2. One thing that i am strucggling with is the whole speed controller and throttle stuff. would this controller suit? i know its 36v an dthe motor 24v but thats not an issue as far as i can see?
http://www.ebay.co.uk/itm/191955036527?_trksid=p2060353.m1438.l2649&ssPageName=STRK:MEBIDX:IT

3.The big question is how i make the throttle work, ideally would like a foot pedal style throttle to match the disc brake operation planned. How do i go about this?

I sincerely apologise if this is simple stuff and has been covered before, however from looking aroumd the forum i can't see it immediately.

Any quidance or assistance would be gratefully received.

Oh I'm in the UK btw.

Thanks all in hope.

Ben

 

[itsid]

Hi Ben,



So first of all.. yes 350W should be enough
if that's one 'light' kart per kid.
depending on the kart you build of course (weight and such)
so check this thread to see what power is needed

the controller will not work, although I don't know the jengching controlelrs, I'd make a bet that they (as most others) have an undervoltage protection (i.e. cut off voltage)
that is well above 24V (likely in the realms of 28.5Volts) so you can't power it with just 24 volts to run that motor.

Motor controllers are a pain at times, as some non ev motors they're labelled with some nasty values.
As far as I know yiyun is a subsidiary of UNITE motors (the ones that make the my1020 - zy1020 motors)
so I'd take one of their controllers.
that one for example:
http://www.ebay.co.uk/itm/24V-500W-motor-brush-controller-for-Electric-bicycle-scooter/111073648966

don't worry about the 500W label.. (it's even better to have a controller rating higher than the motor rating)

And well pedal throttle can be bought..

simple hall effect foot pedal (0-5V) can be had here for example:
https://www.motiondynamics.com.au/hall-effect-foot-throttle-metal.html

personally
I like these:
https://www.motiondynamics.com.au/pull-throttle.html
(here's one in the netherlands.. )
since you can attach it to any pedal you like, just as a gas engine throttle cable would.

you could also convert a thumb throttle like this one:
http://www.ebay.co.uk/itm/Universal...ctric-Bike-Scooter-KITS-3-Wires-/391180615230
(fix the armature somewhere, attach a throttle cable to one side of the thumb lever and add a return spring on the other side)


'sid

 

[Benmitchell423]

Thats Brilliant, thanks for you help.

I was working my way through the thread you linked to this morning.

I think i have calculated the following values working on the basis of
mass being 60kg (kids are only about 20-25kg at present)

Fi = 51.3N
Fr = 11.772N
Fa = 120N (based on a 10 inch wheel thats planned)
Fw 22.68N (using 9m/s velocity as 20mph will be more than enough for them, a CW of 0.8 and a A of 0.7)
Pm(Fi) = 461.70W
Pm(Fr) = 105.94W
Pm(Fa) = 1080.00W
Pm(Fw) = 204.12W

Given that the buggy/kart will mainly be used round the level garden on a mixture of grass, gravel and concrete, no gradients involved and that 20mph will never be reached or needed to be reached, i am assuming that the calculations show 350W motor will be ample. Fingers crossed.

I really appreciate the help and thanks for the welcome. i will carry on planning but then try and document the build on here in case anyone is interested. The plan is to try and get them done for a Christmas present!

Appreciate the links sid, food for thought on the throttles. my mind is buzzing and i think that my wallet will soon be emptying. Having to make two is the expensive part.

I was thinking that i would simply limit the speed acheivable by using a simple adjustable stop on the pedal, this can then be altered as their experience and capabilities grow.

Once again thanks for your help, i am sure i will be back at some point. Need to do some research on batteries.

thanks all

B

 

[itsid]

watch ebay closely.. sometimes a 350W motor is more expensive than the next bigger one (500W) depending on how many are in stock and so on..
So keep your eyes open for that.

having a bit of additional grunt wont harm , there will be no additional speed because of that,
just gives you some 'margin' to play with.

First a 35kg kart is almost impossible; true the motor doesn't weigh anything, but the batteries do a semi sized (45Ah) car battery is ~12kg and you need two .. so 24kg out the door for nothing but the batteries.
assume 4kg per wheel and we're at 40kg already without even having a chassis, an axle, a seat, steering mechanism or anything.

So, before you make any final judgements.. rethink your plans
put some parts on a scale just to know their weight if you have them, or check the internet for weights (most shops incl shipping weights to parts.. that's no more than a hint, but a good one mostly)

Frankly... I think you'll end up with ~35kg plus batteries plus driver on a decently rigid steel chassis.
And since kids grow at insane rates.. it'd be better to assume a 12yo kid as a driver.
(35-45kg roughly)
just for you to not have to start over next year and for them to not cramp themselves into a too small kart until you made the next one
(and yes, that means adjustable seat rails )

just saying.

As I said, I like the pull throttle best, since the stamped steel pedals are not exactly nice (nice ones quickly go towards of 100 bucks) and the price is very well reasonable.
the thumbthrottle can be converted as I said, but... if you have to buy one anyways.. why not buy the nicer one

And yes, making two is going to be expensive I'm afraid.. making one isn't cheap.
you need about 80 for the batteries per kart, and at least another 160 for wheels if you don't buy used ones.
(DO NOT buy cart wheels from the hardware store! ride on mower or go kart... maybe ATV... nothing else)
So yeah.. find used parts if you can..

'sid

 

[Benmitchell423]

Ok, so despite what some say, i am a quick learner. I am getting the fact that i have grossly underestimated the weight of the kart itself once all the items are collated.

Great thoughts on the motor, i will have a scout round and see what i can find.

I am usually quite good with sourcing used stuff so as my list grows i will be able to start searching for bits. Would like to try and get as much "in stock" and to hand so that i can crack on and build.

I like the ideas of the pull throttles, should be able to sort out fine for what i need them to do.

Thanks for the help as always!

Ben

 

[Benmitchell423]

Hi All,

Thanks for the great help so far. I have been away for a bit but changed plans slightly.

The karts are not going to be fast for the kids, just something to pootle round a rather cluttered garden and wood (flat firm surface), the sort of thing that they will be happy to mess around in while i am out there working. Certainly not racing machines. For that reason and for ease, i am now thinking of this route.

I have the option to buy two karts like these for not much money. I figure that converting these to accept the motor and batteries etc will be a good starting point until i get my workshop fully up and running and build some from scratch, perhaps when they are bigger and want a speedy number!

I think that this motor and controller should suffice and be compatible. Sid, hopefully i have followed your thoughts above, 500w better than 350w and yiyun controller to go with the zy motor?

http://www.petrolscooter.co.uk/elec...-watt-11-tooth-6mm-chain-sprocket-zy1020.html

http://www.ebay.co.uk/itm/24V-500W-...663443?hash=item2a6f1af293:g:9p8AAOSw6n5Xws--

Battery wise, i was looking at two high a/h rated car batteries, 40ish a/h rating. is this the way to go?

Mind is whirring with the plans and starting to itch to press the button on some parts. Looking at picking the karts up on Saturday so will be able to strip back and start planning properly then!

thanks

Ben

 

[Functional Artist]

Yup, beginning with rolling chassis is a good start.

That way you can concentrate on the drive train.

...while gettin' some OJT (on the job training) during the build, to figure out what does what & what goes where.

There's a lot to building a frame from scratch.

...design, choosing materials, measuring, cutting, welding, grinding etc.

& if your like me, you'll get so many ideas from this build that when (& if) you build your own frame it'll probably be nothing like what you have in mind right now. (A little education changes everything)

As far as batteries.

...keep in mind that most car batteries have different charge/discharge characteristics than the rechargable batteries used in electric vehicles.

...are kinda big & very HEAVY to strap to a go kart .

...& it takes (4) 12V batteries just to power a 48V system.

...so that's a bunch of weight & space just in battery's.

If it helps, I have been using 12V 35 AH AGM (absorbent glass mat) solar battery's from Harbor Freight. (~$60.00 ea. w/coupon)

Their a little smaller & lighter than car batteries & they have the recharge/discharge characteristics more suitable for EV's.

Here is a kart I built with (2) of the motors like on your kart & running on HF solar batteries.

I have this kart is set up to run @ 24V on (2) separate systems.

(1 motor, 1 controller, 1 throttle, 1 on/off switch & 2 12V batteries)

https://www.youtube.com/watch?v=TRIKLdvGlTA

 

[dcastillo]

you are not going to fit those size batteries on that cart, this is from experience...
here is my build
http://www.diygokarts.com/vb/showthread.php?t=32914
same thing you want to do...
I still have some work to do on it, like finalize the jackshaft for better gearing and that minor part of adding brakes
My 3yr old loves it.. another 6 months or so, maybe for BDay #4, Ill double it to 500W and widen the rear axle for stability
-Danny

 

[Benmitchell423]

Thanks Guys,

most helpful.

Can i ask what battery you use on your kart at present. really need to get my head round what i need to get it all ordered and ready to start getting on with stuff.

Also, how are you finding the gearing? Was looking at getting a 70 tooth sprocket for the rear with the 11 tooth that comes on the motor. Was hoping that with the 500w this would suffice, now a bit concerned that i may need a rethink?

Thanks agaain for the help.

B

 

[dcastillo]

I use two 9AHr batteries from chromebattery

11x70 is what I started with and worked fine driving on the road, but struggled with grass, especially when turning. Keep in mind, I have a 250W motor, you should have almost double the power at similar RPM, so you may be just fine. I am also running 11" tires or so.
I had to add a jackshaft which has been a huge pain and still not working right.

Please let me know how your 11x70, 500W setup works, as I plan to get a 500W motor and would like to remove the jack shaft is possible.

thanx
Danny

 

[Benmitchell423]

Hi Danny,

Of course I will keep progress updated. I will try to remember to start a build thread. Problem is I take some pictures at the start then crack on, keep coming back to it and at the end think “Ahh rubbish, I didn’t take any pictures through the process!”.

I will give the 11x70 a try with the 500w motor and see how it goes. One thing I was thinking about was putting a reverse facility into the mix. Did you do this? I fear that there will be questions coming from me to you lot left, right and centre when I get to wiring the whole thing up.

In terms of batteries, I calculate that 9ah batteries would only give me 26 ish minutes of run time

500w / 24v = 20.83A draw
9AH / 20.83A = 0.43 hours
60 minutes / 0.43 = 25.80 minutes

I think the plan will be to look round and try to find as high a/h rated sealed lead batteries. Trouble is I need to balance cost with durability. I am building, well converting two karts at the same time and will need 2No. batteries a kart to get the 24 volts. That’s without throwing the size and mounting issues into the mix like you have previously pointed out.

I have one project to finish at home then I can start stripping the karts down and playing around with ideas and what I will do to convert them.

Thanks again

B

 

[dcastillo]

your run time estimate is very approximate and is affected by lots of variables... but I agree, go a little bigger then I did...

with my sons smaller cart, I was able to easily add reverse with this $15 switch
http://www.northerntool.com/shop/to...0521?cm_mmc=Housefile-_-RECEIVED-_-707-_-CONF
but its only good for 30Amps, so be careful (though I think worst case the contacts weld and it stays in gear??)

as for wiring, I have been meaning to try and draw up a schematic for my kids, Ill see if I can get moving a bit faster on that
-Danny

 

[Benmitchell423]

So I managed to have a little shopping spree this afternoon and now have a couple of 800w motors on the way with some speed controllers to match. These motors are 36v so was looking at getting three of these batteries for each. Should work shouldn't they?

http://www.componentshop.co.uk/12v-22ah-sla-golf-trolley-battery-replacement.html?___SID=U

B

 

[itsid]

sure thing.. 22Ah is a bit small I think but hey.. the kids are not going to commute in the karts anyways, and since space is limited...

22AH.. quick math:
800W motor (assuming power out not in...) -> ~1000W electrical powerdraw...
@36V that means about 28 Amps to be drawn...
so going full throttle you'll have roughly a 45min ride per charge.. that's good enough for the backyard I'd say.
the less aggresive the kids are on the pedals the longer of course
so it's nothing but a quick estimation of running time.

'sid

 

[Benmitchell423]

Thanks Sid.

No way they will be full throttle round here. Should give plenty of run time for them.

B

 

[Benmitchell423]

So, parts are dripping through the post. I now have motors, speed controllers and rear sprockets.

I have been casting my eye to switches now but feel a bit lost. I am not really fussed by having a key ignition but maybe have a "on/off" switch and then fancy wiring in a reverse switch. Point I become lost is most of the rocker type switches,in fact most of the switches of any type are 12, 24 or 240 volt and varying ampage.
I noted that if it's listed as a 12/24v switch then generally the A halve. If I got a 250v rated at 10A would that still work with 36v and be plenty of A rating?

I think I am all good with the reverse switch. Just need to figure out the wiring on the controller. Only the charging port and brake light (not needed) are labelled. Battery and motor are clear though ��

Nearly finished the wife's studio refurbishment so can crack on in a week or so ��������

B

 

[dcastillo]

If I got a 250v rated at 10A would that still work with 36v and be plenty of A rating?

Incorrect.
The voltage rating is based on the insulation of the switch
The current rating is based on the conductor size.

 

[Benmitchell423]

so i need to focus on finding a switch with the correct Amp rating then. Thanks b

 

[dcastillo]

what amp rating you looking for?

 

[Benmitchell423]

Do you know what, i was literally just trying to work it out. I just want an ignition type switch, happy with key or simple rocker, i had figured that a rocker switch will be easier as i dont have to worry about lost keys then.

I have the 36V 800 watt motors, speed controller to suit. I was just about to google for the answer as the "reply notification" mail pinged through. I was online buying the reverse switch, should be here next week.

Last few bits i need now are batteries (6 in total - 2 x 3 12volt 20ah SLA), the ignition switches and then wire and connectors etc. Throttles have just arrived as i type

I plan to dry run the electrics and whole system before stripping the karts down, that way if i have got something wrong or ballsed up, i can still give the kids the pedal carts for Christmas and work on the electrics to convert for them in the new year.