[Help] 250 Watt Electric Kart

[gokartgunner]

Hello forum,

This is my first time on the forum and I am in need of some advice/recommendations. Firstly let me begin by saying that I am planning on building a two seated electric go kart. I plan to make it street legal.

This may sound very odd, but actually the country which I am situated in, is Malta, and I plan to make my build fit into the category of "Pedal assisted bicycle", this is in fact possible, however the regulations state that the engine must not output more than 250 watts, very weak.

Regulations: http://www.transport.gov.mt/news/pr...cycles-also-referred-to-as-motorized-bicycles

My plan for this is to use a very high gear ratio which will give me enough torque to make it up a hill, then to freely roll down. I do live in a very hilly area.

Motor Link: http://www.ebay.co.uk/itm/ZY-MY-101...porting_Goods_Scooters_LE&hash=item27f5fbddc8

It is rated to 8.9 amperes and a voltage of 36.

Is there anything you notice about my plan that maybe will not work? What are your opinions on a 250 Watt motor? Additionally are there any recommendations?

 

[landuse]

Welcome to the forum. You will want to gear LOW for torque. Your gear ratio if geared low would be a HIGHnumber like 11:1.

I have a feeling that you would never be able to gear low enough with that motor to get up any hills. If you do, it would be so slow that you could crawl faster.

Have a look at this thread for some more insight:

http://www.diygokarts.com/vb/showthread.php?t=9700

 

[gokartgunner]

Thank you for the quick reply, I've read the thread you posted.

It is obvious that I need a far more powerful motor for quick hill ascends. However I would not mind a walking speed, as long as it is able to make it up the hill i'm happy.

What do you mean by "crawling" speeds? Would you be able to supply a speed reference or someway of calculating the speed?

Best regards,

Alex

 

[itsid]

it's the weight that'll make this task more or less pointless.

since you will not even achieve walking speeds with a two seater and just 250Watts
instead you'll likely end up stalling the motor (overheating and draining the batteries without moving)

read the the other thread,

A two seater.. let's assume one adult one kid and a lightweight kart... 225kg.

with a weight like that you need
236 N to move up a hill (force, not power..)
let's just ignore the acceleration and say you are already at the speed you want
(walking speed ~7km/h or 2m/s)
236 * 2 = 472 Watt needed.

(you need twice that much to accelerate going up a hill..)

with the best possible scenario (no bumps, no obstacles.. nothing that could make you slow down)

you could achieve 3km/h maybe 4 if you're really lucky,
that's a old grandma's walking speed or mommy's window shopping

put all together and assume the weight you will need to build this thing, do not forget the batteries..

then you can see what power would be needed, or since you want to keep it in the 250W limit, what max speed is achievable.

'sid

 

[gokartgunner]

Thank you.

That thread is excellent for my needs, this forum is so helpful and amazing!

I will start calculating

 

[CoroTheCat]

Motor Link: http://www.ebay.co.uk/itm/ZY-MY-101...porting_Goods_Scooters_LE&hash=item27f5fbddc8

It is rated to 8.9 amperes and a voltage of 36.

I don't know if I am missing something here, but if the engine uses 8.9 amps and its 36 Volts, shouldn't it be a 320 Watt engine?

Amps X Volts = Watts
EDIT:
Found the problem, an engine isn't 100% efficient, so that is why it doesn't use 320 watts. My bad...

 

[itsid]

I don't know if I am missing something here, but if the engine uses 8.9 amps and its 36 Volts, shouldn't it be a 320 Watt engine?

Amps X Volts = Watts
EDIT:
Found the problem, an engine isn't 100% efficient, so that is why it doesn't use 320 watts. My bad...

very true.. motors are never 100% efficient.

And motors for electric vehicles are generally labelled with
the mechanical power they're able to provide.
(luckily for us)

unline other types of motors, that can be labelled with max electrical power or anything in between.

'sid

 

[landuse]

....you..... is so helpful and amazing!

Thank you. So many people tell me that.