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Nick
Experienced Roboteer
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Joined: 16 Jun 2004
Posts: 11802
Location: Sydney, NSW
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I did some measuring on the size the kart would need to be for someone my size; a 500 by 1000mm frame would be comfortable and with my legs folded up, the steering wheel would have to be around 580mm above the base plate to clear my knees.
That amount of height would allow many different motor & gearbox combinations to drive the front wheels; I have narrowed it down to three:
1) brushless outrunner with chain reduction
This sounds like the cheapest option, but it really isn't. After studying up on many EV forums, a un-sensored motor and R/C controller will not perform well in a vehicle that has sharp acceleration and deceleration.
Adding sensors and a better ESC from Kelly Controls would be a great solution, but that really increases the complexity and cost. This option will deliver the most power in the space available if a cheaper controller & sensored motor can be found.
2)Mag motor with a commercial gearbox
This is looking like a durable and cheaper option, given the plentiful supply of Mags and brushed controllers in the workshop. About half the power of the brushless option but I would only need to buy the gearbox, or possibly make a 3 stage chain reduction for even less money.
3)Dual wheelchair motors
This is the cheapest option of all . Andrew very kindly gave me some chair motors and if they are mounted vertically with a short chain drive to the front wheel, I have everything except for the smaller mechanical parts. The chair motors will be slower than the other options but the chain drive ratio can be tweaked to improve that, as can a little overvolting.
Option 3 is the current winner and the next thing is to wire up the motors, the spare Sidewinder ESC and 30V worth of Lipos to see what RPM the chair motors are capable of.
Update: I have two working chair motors but they are rather slow - the tacho is playing up, so I can't get a reliable RPM reading.
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Mon Jul 15, 2013 8:59 pm |
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