Re: motors/torque

[Joe Sommer <anvilus9-at-adelphia.net>]

Mike,

At 02:19 PM 10/7/2004 -0500, Mike Butts <buttsakauf-at-earthlink.net> wrote:
>Then what do you recommend?? What kind of torque is needed to turn?

All of my design work is for light tanks
less than 100 pounds.

I estimate that they require about 7400 oz-in
(34.5 ft-lb) torque per track with 4 inch DIA
sprocket to allow full-skid turns for 28.5 inch
ground contact length.  This is just an estimate.

Shorter ground contact length reduces torque
requirements.  Larger DIA sprocket increase
torque requirements.  Heavier tanks require higher
torque.  More aggressive track requires higher
torque.

>  I know torque is based on motor design and voltage adds rpms. Though 
> bumping up the voltage usually increases torque due to the extra power 
> available. However 24v requires very large batteries and you lose ALOT of 
> capacity. For example a 24v SLA and a 12v SLA can be the exact same 
> weight but the 12v will have almost double the capacity.

My 24VDC Makita motors from BDF460SHE
cordless drills produce 460 rpm for the low
speed selector with 476 in-lbf (39.6 ft-lb) torque.

My Hetzer weighs about 75 lb, has 18 inch ground
contact length and uses a 4 inch DIA sprocket.
Consequently, 24 VDC Makitas are great for me.
I list all my components and vendors at
http://www.anvilus.com/hobby.html

I have always carried two 18 Ah, 12 VDC gel cell
batteries even when I used 12 VDC motors.

I personally feel that the Hetzer's performance at the
end of battles is now better for 24 VDC than when I had
two batteries in parallel because I am not stalling
the motors as much.

>  SO I should try to find a VERY strong pair of drill motors...right? I 
> DON"T KNOW...argggg.

simple choice

Light tank (Hetzer) = 24 VDC Makita or DeWalt drill motors
Heavy tank (Steve, Will, 3 Pittellis) = 12 VDC EV Warriors
Fast heavy tank (future) = 24 VDC EV Warriors

Joe


**********************************************
Joe Sommer
2378 Nantucket Circle, State College, PA 16803
814.234.4773     anvilus9-at-adelphia.net
http://www.anvilus.com