RC-Monster Forums - View Single Post - Q. about gearing, and some more questions

BrianG · 01.01.2011, 03:49 AM

Usually, XX in XX/YY is the larger gear, while the YY is the smaller gear. So, XX divided by YY gives you a ratio. Example, a 46T spur and 12T pinion would be 46/12, and would equal 3.833:1 ratio. Which just means that the pinion will spin 3.833 times for every revolution of the spur.

By the way, the "spur" could be an actual spur, or the ring gear in a diff.

To get a starting point for gearing, some like to use a 1:1 rollout, which is simply geared such that one revolution of the motor moves the vehicle 1". And then you go from there using motor/ESC/battery temps as a guide. This page helps you calculate the 1:1 rollout: http://scriptasylum.com/rc_speed/rollout_ratio.html

If you don't know where to start in selecting a motor for a particular usage, try this page: http://scriptasylum.com/rc_speed/car_setup.html

This page lets you convert between pitch and modulus for gears: http://scriptasylum.com/rc_speed/gear_calc.html

As far as what motors to get, Castle's Neu-derived motors are a good bet while being relatively inexpensive. There are clones of Castle's motors out there which are cheaper, but they do take shortcuts so their efficiency is not as high. Generally, look for closed endbells (keeps dirt out), finned design (helps cooling), where the wires are NOT extensions of the coils. Some motors like Feigao have wires that are just part of the coils, and don't bend as well as a noodle-wire type of wiring that Castle uses on their motors.

As far as pack wiring (4x 2s1p vs 1x 8s1p), it comes down to vehicle layout and wiring. People use multiple packs in series because the vehicle layout requires it (like the Traxxas E-Revo). Also, you may have a lot of 4s packs for different vehicles, so it makes sense to just use two of them to get 8s instead of buying an 8s pack. Also, using multiple packs adds more wiring/connectors that adds resistance and more places for something to go wrong. Generally, use a single pack where possible.

However, most packs come wired for up to 6s max. Probably because there are very few balancers that handle more than 6s per pack. To get higher cells counts above 6s, just put them in series.

	(#3)
BrianG RC-Monster Admin Offline Posts: 14,609 Join Date: Nov 2005 Location: Des Moines, IA	01.01.2011, 03:49 AM Usually, XX in XX/YY is the larger gear, while the YY is the smaller gear. So, XX divided by YY gives you a ratio. Example, a 46T spur and 12T pinion would be 46/12, and would equal 3.833:1 ratio. Which just means that the pinion will spin 3.833 times for every revolution of the spur. By the way, the "spur" could be an actual spur, or the ring gear in a diff. To get a starting point for gearing, some like to use a 1:1 rollout, which is simply geared such that one revolution of the motor moves the vehicle 1". And then you go from there using motor/ESC/battery temps as a guide. This page helps you calculate the 1:1 rollout: http://scriptasylum.com/rc_speed/rollout_ratio.html If you don't know where to start in selecting a motor for a particular usage, try this page: http://scriptasylum.com/rc_speed/car_setup.html This page lets you convert between pitch and modulus for gears: http://scriptasylum.com/rc_speed/gear_calc.html As far as what motors to get, Castle's Neu-derived motors are a good bet while being relatively inexpensive. There are clones of Castle's motors out there which are cheaper, but they do take shortcuts so their efficiency is not as high. Generally, look for closed endbells (keeps dirt out), finned design (helps cooling), where the wires are NOT extensions of the coils. Some motors like Feigao have wires that are just part of the coils, and don't bend as well as a noodle-wire type of wiring that Castle uses on their motors. As far as pack wiring (4x 2s1p vs 1x 8s1p), it comes down to vehicle layout and wiring. People use multiple packs in series because the vehicle layout requires it (like the Traxxas E-Revo). Also, you may have a lot of 4s packs for different vehicles, so it makes sense to just use two of them to get 8s instead of buying an 8s pack. Also, using multiple packs adds more wiring/connectors that adds resistance and more places for something to go wrong. Generally, use a single pack where possible. However, most packs come wired for up to 6s max. Probably because there are very few balancers that handle more than 6s per pack. To get higher cells counts above 6s, just put them in series.