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Question About Converting to Electric

Old 05-25-2010, 01:13 PM
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Cambo
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Default Question About Converting to Electric

Hi everyone, im more of a heli/plane guy but have a duratrax raze that doesn't have a power. I ended up, quite literally, blowing the conrod out the bottom of the crank. . Anyway, it is just sitting in the box and now Im thinking that i want to convert it to electric. Here is what i got on hand, 4 7s A123 packs (run these through my protos 500) and a 50amp 25v esc. The esc is a perfect match for the batteries and usually is driving a motor in the range of 800-1200 watts. Now, i would like to move my car with this much power but am just no sure how to do this. I want to be careful with gearing here and I guess i am asking how to gear for a certain speed. For helis, you match the gear ratio to your head speed so your motor is turning almost its full RPM for the max head speed to maximize efficiency and lower the amp draw. Not sure how to do this with cars, would like to shoot for 25-40mph depending on what is actually doable.

Thanks
Cameron
Old 05-25-2010, 01:15 PM
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qoisdhc oqina
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Default RE: Question About Converting to Electric

Just throw the stuff on there and run it, check temps often.Too high, ya gear down.Not much to it. Do you have a motor or no?
Old 05-25-2010, 01:23 PM
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Default RE: Question About Converting to Electric

Just need a motor and a few pinions. Was thinking the same thing with gearing, but not sure what motor to start on here.
Old 05-25-2010, 01:37 PM
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Default RE: Question About Converting to Electric

Typically if your model's total weight will be less than 7-10lbs total with everything ready to run, then go for something like an inexpensive 540 sized but long can motor (Feigao L or XL motors, Medusa 3650 or 3660, or more efficient NEU but those are pricey), 2000-2600 Kv, geared for something like 10:1 total driveline ratio. That may be your starting point and then you can go up or down on the pinion or Spur gear size to adjust it.
Old 05-25-2010, 02:29 PM
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Default RE: Question About Converting to Electric

generally for 1/8th you want a 100-120A esc minimun

http://rc-monster.com/proddetail.php?prod=rcmdtxrazemm if you need the mount for the motor, I got their Jammin CRT .5 and find it made pretty good quality wise, also their shipping's pretty fast.
Old 05-26-2010, 01:20 PM
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Default RE: Question About Converting to Electric

100-120A minimum? Is this because people setup 1/8 scale on 3-4cell packs? A 7s 2P A123 at 120AMP would be 2770 watts. Thats over 3.5HP. The glow engine on this thing, in the best case scenario of 30,000rpm was close to 3hp.
Old 05-26-2010, 01:47 PM
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Default RE: Question About Converting to Electric


ORIGINAL: Cambo
A 7s 2P A123 at 120AMP would be 2770 watts. Thats over 3.5HP. The glow engine on this thing, in the best case scenario of 30,000rpm was close to 3hp.

Welcome to brushless 1/8th scale You need that many amps, 100 or so, to move these big trucks.
Old 05-26-2010, 03:20 PM
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Default RE: Question About Converting to Electric

These two links should help you figure out what gearing, batteries, motor etc. to use:
http://scriptasylum.com/rc_speed/_top_speed.html
http://www.rc-monster.com/brushless/advanced.html
Old 05-26-2010, 04:00 PM
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Default RE: Question About Converting to Electric

actually, the glow motor is rated up to 2.5, but probably doesn't rev much higher than 20,000, putting it right around 1hp from what i have read. Im worried that 100-120A plus 7s123 is going to move this thing WAY faster than i am intending . Again, if you guys are running 4s packs that makes a TON more sense as the wattage output is around 1700 watts, just a hair over 2hp.
Old 05-26-2010, 04:08 PM
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Default RE: Question About Converting to Electric

Links where very helpful btw
Old 05-26-2010, 05:34 PM
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Default RE: Question About Converting to Electric

ORIGINAL: Cambo

actually, the glow motor is rated up to 2.5, but probably doesn't rev much higher than 20,000, putting it right around 1hp from what i have read. Im worried that 100-120A plus 7s123 is going to move this thing WAY faster than i am intending . Again, if you guys are running 4s packs that makes a TON more sense as the wattage output is around 1700 watts, just a hair over 2hp.
should be looking at RPM's not wattage or HP.
a smaller motor and ESC will fry but hey its your cash. If your the expert you shouldn't have asked.

All I know is I'm planning on getting another Jammin x1 cr eventually and gonna pop a 120-150A esc in it when I convert it. remember going higher in ESC ampage is better than going too low and frying it.
Old 05-27-2010, 09:33 AM
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Default RE: Question About Converting to Electric

Hi guys, thanks for all the help. I decided to buy a cheap nitro engine. Got an ofna force .26 of tower for $109 shipped to my door. This is just going to be easier than dealing with converting. Would love to do it, but just don't see it as worth it if i have to buy a $100+ esc plus motor to get a decently fast car
Old 05-27-2010, 10:42 AM
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Default RE: Question About Converting to Electric


ORIGINAL: Cambo

Hi guys, thanks for all the help. I decided to buy a cheap nitro engine. Got an ofna force .26 of tower for $109 shipped to my door. This is just going to be easier than dealing with converting. Would love to do it, but just don't see it as worth it if i have to buy a $100+ esc plus motor to get a decently fast car
Force motors are good got a .28 in my jammin thing pulls really strong

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