Nir's ekart

[number 37]

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[WillTheKing96]

Hey Nir, looking good!
Quick Question..how fast are you anticipating that motor to go?
I have found the same one online and im interested in using it for my kart, although i would like to know how fast it will go

Thanks,
WillTheKing96

 

[baer]

`Erm. I'm an electronics amateur... a PIC then?

No PIC, just transistors.

It "works" fine but I need more amperage out of it :\ I'm ordering higher voltage and amperage mosfets for it... but I'm worried the FET drivers can't drive them.

I am also a bit worried about how will it drive, so far tested o.k. on my desk only.

If I may ask, where did you learn about electronics? I'm trying to start with just modifying my controller but even that is too much to ask ):

I am an electronics engineer but for this stuff you need only the basics I am sure you can find plenty of guides on the web.

 

[baer]

Hey Nir, looking good!
Quick Question..how fast are you anticipating that motor to go?
I have found the same one online and im interested in using it for my kart, although i would like to know how fast it will go

Thanks,
WillTheKing96

The motor spec is for 3000 rpm max, with sprockets of 55 and 11 teeth (1:5) the rear shaft will turn max 3000/5=600 rpm or 10 revolutions per second, the rear wheel diameter is 25cm so wheel step is 25*pi = 78cm, and so the kart will forward 10*78cm per second = 7.8 m/s = 28 km/h = 17 mph.
This calculation if for the theoretical speed limit, the actual depends on the load (kart weight) and batteries.

Since this kart is for a small kid this speed limit is o.k. for me, you probably want your kart to go at least twice faster, that will call for a better ratio or bigger wheel.

 

[baer]

Steering wheel. I couldn't order from the web because of the shipping cost, locally found for only for $70...
Next are the pedals and a seat. I was thinking to use this plastic one but it does not have any side support, any ideas?

 

[baer]

What is the rpm of that motor and where did you get it and for how much?

http://tncscooters.com/product.php?sku=106110

All these motors are chinese made by www.unitemotor.com/

 

[oscaryu1]

5:1 gear ratio is a bit tall, but it should pull it. I have more experience with various scooter motors than the electronics lol (sadly ), don't bother overvolting it over 12V for one, and for a GO kart, I'd recommend a minimum of 500w. 350w is a bit low... but on lighter mopeds, those things are quite torquey.

A smart idea may be to gear it down and overvolt it. Let that thing rev freely.

 

[baer]

Which battery should I get?

If I go with 2x Yuasa 12V/7.2AH for example, the actual capacity of 7.2AH when used in 1 hour will be 4.2AH i.e. current of 1A and motor will run in 24V*1A = 24W... (out of 350W)

So a larger battery is defiantly required.
Can you tell from your experience which setup is ok and cost friendly?

 

[oscaryu1]

You have to remember SLA's suffer from the Pukert's effect, so it's not actually 7.2aH when under use.

I'd get 3x 12v 12aH batteries. A overvolted smaller motor with lower gearing = torquey, and amazing range.

The taller you gear it the faster you'll get, but the more amperage the motor will suck up. Best combination is light overvolt and low (torque) gearing.

 

[baer]

I think Pukert's effect is what I saw it the datasheet that a 7.2AH which is drained withing 1 hour gives only 4.2AH.

About overvolting to 36V, what are the disadvantages? won't this damage the controller (some electronic devices including relays are rated 24V)? besides I will need an extra battery and a 36V charger.

 

[rabies]

ha that thing is cool. if you put some kind of tight innertube rubber around the wheel it wouldnt be bad.

 

[oscaryu1]

I think Pukert's effect is what I saw it the datasheet that a 7.2AH which is drained withing 1 hour gives only 4.2AH.

About overvolting to 36V, what are the disadvantages? won't this damage the controller (some electronic devices including relays are rated 24V)? besides I will need an extra battery and a 36V charger.

I've run 24v at 36v before. All controllers I did it do did survive, for a month or so.

Disadvantages... shorter controller life (depends), more weight (battery), needs a 36v charger... upshot, much longer runtime, more revs, a tad more torque.

 

[baer]

Update-
Installed pedals, seat and pot box mechanism to transfer the pedal movement into potentiometer rotation.
The steering wheel is going to change in future since i don't like it.
Next is connecting the throttle to the controller and motor.
I am also thinking about simple break that will work tougether with dynamic electric braking
Pics later (how to attach pics from iphone to forum message?)

 

[baer]

pics...

 

[landuse]

That is looking good there baer. I like the seat. I would probably have to agree with you about the steering wheel. I think it would probably feel uncomfortable holding it.

 

[baer]

Started assembling the electric components...

 

[oscaryu1]

Work on them welds

Looks great

 

[baer]

Working on the wiring.
I am using a master relay, another one for the brake (cuts the power when the brake pedal is touched), another 2 for reversing.

 

[baer]

Kart is rolling.
before I take it outdoors, need to apply throttle mechanical limiter and rear brake (now pushing the brake pedal only cut the power).
But it goes pretty smooth.


video:

 

[Chuechco]

Good job!
I noticed the large space behind the seat. Did you want it to be so?