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Old Sep 03, 2013, 06:43 PM
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United States, IN, Vincennes
Joined Sep 2013
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Help!
Power system for cart help!

I'm new here and I'm hoping I can get some help. I'm in an engineering club in college and our project for this year is to design a go cart of sorts that will do 60 mph or better. I was hoping to adapt some RC components on the market to create a power system to power my cart. Does anyone have any idea how much power it will take to do this? I was looking specifically at the larger turnigy out runners from Hobby King. Such as the 80, 100cc out runners. Any ideas or help out there?
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Old Sep 03, 2013, 08:29 PM
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Joined Nov 2007
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For 60 MPH you will need something larger then 100cc. Here are some larger motors:

http://www.electricscooterparts.com/

They have a page for school projects and with a 500 watt motor one team got 12 MPH. I own a cart with a 5HP Briggs and it will do maybe 15 MPH. I used to own 250 Motorcycle with maybe 20 HP and it had a top speed of about 70MPH.

http://www.electricscooterparts.com/...hourparts.html

I would estimate you will need 15,000 watts. I would look in the junk yards for motor from a Honda hybrid such as the Insight.

http://www.rcgroups.com/forums/showt...ighlight=honda

Here is a high performance motor that will do the job:

http://www.evparts.com/products/golf...ors/mt2112.htm

Here is another type of car that has a top speed of 125MPH. It uses a 20 HP motor but with a bit of over volting they get over 100 PH

http://www.plasmaboyracing.com/bluemeanie.php
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Last edited by mjsas; Sep 03, 2013 at 08:51 PM.
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Old Sep 03, 2013, 10:48 PM
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USA, MO, Florissant
Joined Nov 2010
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My '65 Honda S90 (~8hp) would top 60mph, with no wind; I had to lie down on the tank, to minimize drag, but it would do it. So 100cc, or equivalent, could get him there, given time and a slick drag coefficient. Since 8hp is about 6kW, you may want to look for about 10kW.
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Old Sep 04, 2013, 09:42 AM
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Joined Nov 2007
858 Posts
The Tesla electric car uses a three phase induction motor with a standard squirrel cage rotor. (Someplace on the web are photos of the motor's guts, I can't find it now.) Also it has no transmission, only one gear ratio. Three phase induction motors have full torque at stall and the torque curve is fairly flat so they have good performance. The motor control is simple as they do not need sensors, they run at one frequency. The speed is controlled by just the PWM.

Another factor with a three phase induction motor is that the torque is proportional to current squared so they can have full HP at very low speeds. With any PM motor the torque is only proportional to the current and may need a multiple speed transmission.

You might look into using a 5 HP three phase motor which should be only a few dollars at a scrap yard. It weights more but on a cart it should not be a problem.

Below is a graphic showing power loss in a Tesla car. This picture is from a Tesla web site. Air drag is the big factor at high speed.
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Old Sep 06, 2013, 06:32 PM
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United States, IN, Vincennes
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Well. Thanks for the help and ideas. I ended up ordering two outrunners today. They are capable of 7000w each on 15s. They are rated up to 18s so hopefully that should be enough.
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