Re: metal tracks [TANKS]

[Mike Lyons <mxlyons-at-cox.net>]

Chrys,

The motors provide what is known as "tractive effort", which is needed to overcome 
the rolling resistance of the load, which comprises friction in the rolling parts 
and gravity if the ground is not level.

If a 15-year-old was being winched vertically, the tractive effort would be the 
weight of the person.  But on a horizontal surface with zero friction (say idealized 
ice skates), the tractive effort is zero.  (There is a small amount of force 
required for acceleration of the mass, but none to maintain a constant speed.)

It's not easy to make this type of calculation because there are so many factors 
involved.  For a simple test, suspend your tank so its tracks are off the ground and 
measure the current draw at full speed.  Compare the current and speed to the 
no-load speed for the motors.  This will give you a rough idea of the effort needed 
to keep the tank moving on level ground, overcoming friction in chains, belts, 
bearings, tracks, etc.

Regards, Mike



---- Chrysanthos Kanellopoulos <xchrysk-at-otenet.gr> wrote: 

=============
... When you think that a 24 V motor for a scooter carries teh weight of a 
15-year-old, and you use TWO of these motors in a 35 kg heavy tank, 8 kg on the 
tracks is not an awful lot of weight.
...