Re: Hydraulic Drive

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

Frank,

At 09:33 PM 8/17/2004 -0400, you wrote:
>If anyone out there knows something about hydraulics, ...

I have never built a hydraulic vehicle, but I have
built several industrial hydraulic machines.

I fully concur with Steve's response.

Hydraulics are the right choice for larger vehicles
propelled by internal combustion engines such as
zero-turn radius mowers, skid steer loaders (Bobcats)
and David Shultz's 1/3 or 1/2 scale tanks.

However, hydraulics would effectively double the
weight, complexity and maintenance of our 1/8 to
1/6 scale vehicles, plus it would be very inefficient
in terms of battery power.

>PS. Joe Sommer, do you have an estimate for the minimal amount of torque 
>needed to drive our tracks competitively?  I know we need about 250 rpms 
>at the drive shaft ...

250 rpm with a 4 inch DIA sprocket produces 2.97 mph.

Hetzer T010 with 12V Makita drill motors, 1/1 drive
ratio and 4 inch DIA sprockets was slightly underpowered
and had trouble doing full skid turns in tall grass.

12V Makita motors provide 400 rpm with no load
and maximum torque of 320 in-lbf.  As you know,
max torque is not produced at max speed.

Hetzer T010 with 24V Makita drill motors has plenty
of torque.

24V Makita motors provide 460 rpm with no load
and maximum torque of 476 in-lbf.

Using 12V, EV Warriors are rated for 2210 rpm with
no load and maximum torque of 43.2 in-lbf (691 in-oz).
http://www.robotcombat.com/marketplace_ev.html

With a 9/1 reduction ratio that most tanks use,
12V EV Warriors will provide 246 rpm and maximum
torque of 389 in-lbf.

I recommend about 350 to 400 in-lbf torque for a
4 inch DIA sprocket.  For 5 inch DIA sprockets,
you will need to provide proportionately more
shaft torque to get the same track propulsive
force.

Hope this helps,
Joe


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