Newbie, with stupid questions!

[Tiley]

Hi, ive recently started a go kart project for my son who is only 4. I had originally intended to "re-arrange" his bright yellow disgusting damaged 6v power wheels, onto a simple metal chassis to resurrect it, but i quickly got carried away and now have ended up building (if not a little shoddy ) a small go kart.

Ive kind of muddled my way through it, and using a mig welder and some scrap metal have got something half handy, but im now at a point where i have to spend some cash and would be grateful for advice.

I originally planned a shopping list of- 2×24v 12ah batteries, a 350w e scooter motor, an ebay speed controller and throttle.

I was hoping this would be ok for a young boy but had a few questions..

Im a car mechanic so have access to old motors, starters, fan motors etc would any of these do a job?

If i went 36volt and put a 500 or 800 w e scooter motor on it, are there any easy ways of regulating the speed? Ie if its too quick, being able to switch between low and high power would be handy

Ive played with the idea of using a pedal from a car as alot operate on a 1-5 v output, anybody else done this? Or modified a twist throttle into a pedal?

Also mobility scooter motors, can they be operated successfully with an e scooter speed controller?

Thanks in advance for any tips given

 

[itsid]

Well first you may want to read this thread eventually
it gives you a good idea of what power you will need/want for your son.

eyeballing it, I'd say the 350W will be a good choice.. 250W may be enough, 500W can be already to powerful for a kid that age.

I'd say find a 24V motor it's much easier to find batteries for if you can use two 12V as a pack

And all the DC motor controllers made for scooters karts and such do have a hall effect throttle but it's 0-5V at 1V the motor is already powered.
but there are pedal throttles made for those controllers, so you should find one.

Starter motors can be converted
read here:
http://www.diygokarts.com/engine/car-starter-motor-conversion.html

And for your kid I think it should work well; just choose the model wisely
and check it's drawing amps to find out what controller you need.

To reduce the poweroutput you can either manipulate the throttle
(just add a resistor to the signal line reducing the out from 5V max to say 4V or even just 3V max)

you can add a switch to short the resistor for full speed.. (or add a variable resistor to set it gradually)

'sid

 

[Tiley]

Hi and cheers for the reply.

I keep looking and toying with the higher rated stuff but think im getting carried away! To be honest, a friend at work dabbles in mig welding but isnt great, the more i look on these forums the more i want to scrap it and start again.

Think ill finish this one with a 350 watt motor , it was never intended to be quick, and think i would be getting carried away putting anything more on this chassis!

Ive also been eyeing up the geared motors but dont know if i would need the reduction?

The throttle resistor is a good shout, didnt know how i would get around the speed controller, but putting in a switchable resistor should be easy enough!

Getting a bit addicted to this already

 

[itsid]

Ive also been eyeing up the geared motors but dont know if i would need the reduction?

The throttle resistor is a good shout, didnt know how i would get around the speed controller, but putting in a switchable resistor should be easy enough!

You will need gearing! but you should do it yourself, and don't buy a geared motor.. e-scooter motors nearly always have a sprocket already attached to it.
and with gearing (and DIFFERENT gearing) you can change top speed and take off a bit to adjust.

and
NOOOOOO you cannot run a motor of a variable resistor!
You can add a resistor to the signal line of the throttle that goes into the controller;
not replace the controller!

You must have a speed controller!
Everything else is not safe and potentially dangerous.
You wouldn't want your 4yo sitting next to a red hot resistor,
that maybe even touches a lead acid battery...

'sid

 

[Tiley]

Sorry meant putting in a switchable resistor on the signal wire from the throttle, not on the wiring to the motor!

Ive already got a couple of sprockets to start with and ill take it from there, it will be single wheel drive, ive got a mini moto chain, hoping its the same chain size as the sprockets on the motors, if not its not the end of the world!

In regards to the controller, will a 36v controller control a 24v system? Or do you have to work with the same voltage rating. Only asking as ive read people overvolting these motors, if i buy a controller would be good to have options open to me to upgrade it.

 

[itsid]

possible but not a good idea.. it's better to take the same voltage rating.
(as I said in the thread I previously linked )

the controller you need is maybe 20-25 USD new;
so if you want to upgrade I think you can spend that much again
Or.. get a controller that has a bigger output like 500W or 750W
and if you want to upgrade, buy a motor with the same voltage rating just a bigger wattage.

'sid

 

[Tiley]

Cheers, ive got someone on the scout for some house alarm batteries that should do for now, eyeing up a 450 watt 24v mobility scooter motor at the moment too should do the job !

 

[dcastillo]

be aware those smaller batteries may only source a few amps (check their spec sheet) even your small setup could easily pull 20-30 Amps on acceleration...
Might want to do a 2x2 batteries setup to split the current between two batteries to help

or these are actually pretty decently priced
http://www.chromebattery.com/12v-7ah-sealed-lead-acid-sla-t1-connector.html
I am using the larger 19AHr ones... they have tons of sizes

-Danny

 

[Tiley]

Cheers , problem being im in the uk. Ive said to him to grab what he can 7ah upwards, like you say if i can get 4 7ah batts and pair them up should be ok?

Got tonnes of car batteries but been advised against using, i would need to fit a trailer to pull them aswell!

The motor ive seen on ebay states 450w output on the sticker, 850 peak. Been looking for speed controllers of 24v that can handle 800 watts and cant find any ��

 

[Tiley]

Thought i would add a pic of the car so far, dont be too harsh, been doing this on tea breaks at work and when i should have been working! Ive already reversed the front steering arms as had my ackerman back to front

 

[dcastillo]

thats a sweet looking cart!!!

thanx for the idea of the control box down the middle, been trying to figure out how to mount mine

-Danny

 

[Joe-405]

Your doing a great job..........I only wish my seat was as comfortable as yours !!!

 

[Tiley]

Cheers, its not so great close up!, i wont be posting in the "show us your welds" thread

was going to make a dash panel for the switches but this way keeps them out of the way off your feet ....i mean my boys feet

 

[Tiley]

Got a little ebay fund building up so will probably purchase a motor shortly, one last thing before i do, radiator fan motors? Anybody used one for this?

 

[Tiley]

Anybody have any links to a simple schematic for putting in a reverse switch when using a speed controller without reverse on it? Can you reverse the polarity to an e scooter motor between the controller and the motor?

 

[itsid]

no switch you'll need a relais doing that for you since you must
have contacts capable of transferring enough amps and second must switch both sides..

a matching relais would be
JQX-38F 1KW 24V DC 40A

'sid

 

[Tiley]

Cheers, was thinking along the lines of putting in some switchable automotive relays and trying to do it that way but was struggling coming up with a circuit, i wont bother now anyway those relays youve listed are a good price!

 

[itsid]

Yes, it's not too expensive..
just get a relais holder with it in case you order it;
screw terminals are much more comfortable since you need to short one or two tabs.

'sid

 

[Tiley]

Cheers for the help, its coming along ok, ive driven it briefly direct to battery. Ive had a speed controller wired up and working correctly, unfortunately i jabbed my multimeter into the "battery capacity" 2 pin plug to see what it was sending out...unfortunately i was rushing and had the multimeter lead set for amps and smoked the module �� so waiting for another.

To save me smoking another, whats the best way to charge? Can i just put a 24v charger across the batteries whilst connected to the module? The controller has a 2 pin plug labelled charge port, should i use this instead? Cheers

 

[Poboy kartman]

Welcome to the forum! !!