rc motor no reduction drive?

[jmygann]

but it appears that the colossus motor with a Kv of 75 may be able to be used in a "single stage drive"..... especially in 20-24" wheel

A internal hub would also give a little more reduction ... SRAM DD

Any other RC motor more capable ? 48 volts

 

[Miles]

Mathematically both calcs are correct but you are both assuming that you can achieve no-load rpms at your target speed.
That aint gonna happen ! ... motors wont achieve max NL rpm under load unless they are hugely overrated ( like X 10 !)
you need to estimate or experiment to establish you motors loaded performance.

You mean close to....... No motor will ever achieve no-load rpm when loaded!

 

[MitchJi]

Hi,

so for a Kv of 75 .... and 30 mph ...

Motor maximum off load rpm = 48 volts x 75 = 3600 rpm

Wheel rpm at 30mph = (5280 ft /60 mins) / (30 mph x 3.142 x 2 ft) = 422.5 RPM

Reduction ratio required = 3600/422.5 = 8.5

Is that correct ?

Using one of these calculators will be much easier (use mph at 100 rpm in the Gear units pulldown):
http://www.sheldonbrown.com/gears/internal.html
http://www.sheldonbrown.com/gears/index.html

Mathematically both calcs are correct but you are both assuming that you can achieve no-load rpms at your target speed.
That aint gonna happen ! ... motors wont achieve max NL rpm under load unless they are hugely overrated ( like X 10 !)
you need to estimate or experiment to establish you motors loaded performance.

Just figure on 80%-85% (Miles suggests using 85%). That will be close enough for gearing. So in the example above:
48 volts x 75 x .85 = 3,060. You might want to use actual voltage instead of 48 (do you want 30 mph with voltage drop near the end of the pack or fresh off the charger?).

The Calculator shows the following for a Nexus 3 speed, with a 26" nominal tire at 100 rpm:

10.6
7.7
5.7

7.7 is at 1:1 so about 400 rpm for 30 mph so at 3,060 rpm you would need a 7.65:1 reduction which is reasonable and makes that motor a good choice (NOTE: If you do a right side drive, to use the gears, through the crank you will probably need about 17:1).

 

[spinningmagnets]

the project I want to do with this motor, is an electric motorcycle

You will find many useful responses in the E-motorcycle section. Franks project used the motorcycles transmission, although I seem to remember he only used 2 of the gears. For street driving you may need 3 (motorcycle gears are typically closely spaced ratios).

http://endless-sphere.com/forums/viewforum.php?f=10

 

[ev_nred]

thanks! i'll have a look there one question franks rm125 motor was rewind to 75 amps (about as mucu as i will use with the rc motor) cant I just have the same gearing as him? no gear box but just the same ... um whats it called reduction fraction?

 

[ev_nred]

sorry for asking but I cant get my head aorund a few questions, first off, does anyone know where to get the motor sprokect? (12mm bore #219 :? :? :? ) and can I get a regaler #219 sprokect and just put it on a 3-speed hub and then bolt it on to the motorcycle? thanks im still just planing for the build btw! thx u!!!!! 8)

 

[Hillhater]

just google ..go kart sprockets.
try these ..http://www.gokartgalaxy.com/engine_sprockets.htm

hint.. depending on where you are ( US, Europe etc) you may find it easier to consider #35 or #40 chain sizes as they are more common in some areas.

 

[ev_nred]

thx but after some math none of this is 12mm? correct me if im wronge

 

[Hillhater]

Probably not... but you could make adaptors.. or make a motor shaft that fits the available sprockets.
I hope you dont expect to be able to find everything exactly as you need it. ! .........life ant like that ! :wink:

 

[ev_nred]

of course not I looking for something like 5-8mm so I could drill out 12mm the only ones I found were like 20mm I could I pull something like this without welding? (the entier project I mean)

 

[Miles]

You'll need to make a bush for the 3/4" bore ones.

See: http://www.endless-sphere.com/forums/viewtopic.php?p=223986#p223986

 

[TylerDurden]

No reduction:

 

[ev_nred]

thanks for the link! and can I use 8mm chain used on scooters and mopeds? does anybody know how much hp can the 8mm pitch chain handle? thx u all!

 

[spinningmagnets]

In the pulley resources stickie theres a link direct to the SDP-SI page with adapter sleeves that allow an 8mm, 10mm, and 12mm shaft to fatten up to 1/2" which provides many industrial parts options. The 12mm sleeve is quite thin, as 1/2" is only 12.7mm, I have the 10mm-to-1/2" bore-reducer sleeve and I am happy with the quality.

http://www.endless-sphere.com/forums/viewtopic.php?f=28&t=7192&start=30#p311888

It may be possible to take a generic 1/2" bore sprocket and attach a 219 sprocket onto its side.

 

[ev_nred]

thanks for the hlep you guys are amazing! just one question, if I were to install hall sensores in the wronge way, would it kill the motor? thanks for the hlep 8) :wink: 8) 8)