RE: [CAD_CAM_EDM_DRO] Re: Problems in Timing Belt drive system in 6WD robot

Hi Jon,

I believe what Alan has built is very similar to what's in the link below
and I don't believe they have rocker with most of the weight on the middle
axel. By the way, they are great fun to drive around and will turn on a
dime and scuff up the dirt or pavement the same way a tank with rubber wear
pads does.

http://www.maxatvs.com/index.php?src=gendocs&ref=guided_tour_max2&category=G
uided Tour

Instead of a transmission though, he's using two motors independently
controlled so that's really the only difference. And when compared to a
tank, regardless of whether the track is driven from the back, the front
part of the track moves the same speed as the back part of the track which
is what Alan is trying to do with the toothed belts.

Alan's issue is that it's likely the toothed belts are too small for the
load they are being asked to handle or his chassis is flexing allowing the
distance between the pulleys to decrease and then skipping teeth. That's
all.

John Dammeyer

-----Original Message-----
From: CAD_CAM_EDM_DRO@yahoogroups.com
[mailto:CAD_CAM_EDM_DRO@yahoogroups.com] On Behalf Of Jon Elson
Sent: January-26-13 10:41 AM
To: CAD_CAM_EDM_DRO@yahoogroups.com
Subject: Re: [CAD_CAM_EDM_DRO] Re: Problems in Timing Belt drive system in
6WD robot

John Dammyer wrote:

> Hi John,
>
> I disagree. The principal of independent drive to both sides is used
> pretty well all tracked vehicles. Just watch a dozer or tank turn in
> place with one side turning one direction while the other side turns the

other.

> Control is often with two levers, one for each side, forward and

backwards.

>

No, a dozer or tank has a strong tread that handles the slippage when
turning. If you've ever seen a dozer turn in soft soil, it churns the
ground mightily as it turns, due to the sideways slippage of the front and
rear portions of the tread. They only drive the tread from the rear axle,
the front is an idler.

The problem with this vehicle is all left wheels, and all right wheels, are
rigidly synched by the belt. When turning tightly, the middle wheels are
closer to the center of the turn, and should not be turning as fast as the
front and rear wheels.
When turning on its center, the center wheels need to turn MUCH less than
the outer ones.
Why does this vehicle need six wheels? Try tying the suspension up with
wires to unload the center two and see how it turns.


Jon


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