Wednesday, December 7, 2011

Randy Willard's TRG continuing developments..

I had a chance to work with Randy's TRG car in the 180 mm format with rubber tires.  Randy asked me to look at what we could do to get the car a little better.  It was ok, but it needed some TLC so we could get it fast for carpet.

First I changed the front end links to be closer to the F104 front end i have been working with lately.  I had originally helped get the front end setup for the modern narrow style, but the 4 links all connected to the camber plate.  I find that the front end is easier to set up with the caster link extending back to the servo mount.  This makes the camber and caster links affect each other less as you adjust the front end.  Otherwise, each setting keeps changing as you adjust the other.

A side view of the link setup.  There is a fair amount of caster in the car.  Note that as you add caster and camber, it will create steering, and traction roll issues, too.

Originally, Randy had the long, green fiberglass link on the car.  This was very soft, but great for outdoor racing.  After we tried the shorter, and slightly stiffer green fiberglass link, the even stiffer black side link was settled on.  The shorter links don't allow as much articulation, as well as being stiffer.  I eliminated the o rings from the setup as well, substituting plastic washers of a similar size to remove even more compliance.  Rubber tires are heavier and seem to want a stiffer side to side suspension.  The links are cranked down for maximum stiffness.  This also limits the travel, which I think helps keep traction rolling to a minimum.

Initially,  I did have some traction rolling.  Reducing camber to under 1* and reducing caster brought the car to a very drivable state.  Caster is probably 6-7*, but I didn't happen to measure it before I gave the car back to Randy.  The camber plate is also set to the "1.0" position, so the overall link length is short, which helps to get some roll out of the front end of the car.  The shock has 45 wt Losi oil.  I'm not sure if it is the shock's smaller diameter, but it felt better with a slightly higher weight oil than I usually run (35wt).  Randy had loaded the TRG damper with a heavy lube, not sure what it was, but I just checked it and made sure the grooves iun the damper were filled and it seemed spot on.  The grease felt about the consistency of diff ball lube, and the car felt good, so I left it. 

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