Calculating Toe-in (REPOST)
Calculating Toe-in (REPOST)
(OP)
I posted about calculating a toe-in angle for an electrical pivoting system for a theatrical set. The set is on casters for general pushing-around. To make the set revolve in the view of the audience, we are installing a pivot point that will lower in the center of the set and lock the set in place. Then the electric 12" diameter drive wheel (solid rubber tire) will also be lowered to the floor at around a 8' radius from the center.
All the info I can dig up on this relates to 4-wheel vehicles. Two of you guys replied recommending 0 deg toe-in.
I did more reading about "scrub" in vehicles. This is distortion of the tire tread resulting from the turning forces on the wheel. I did a calculation for the scrub angle from the footprint of my tire (which was a guess), and got 0.4 degrees. I figure I should split that in half for a neutral load and go with 0.2 degrees.
Joe Dunfee
All the info I can dig up on this relates to 4-wheel vehicles. Two of you guys replied recommending 0 deg toe-in.
I did more reading about "scrub" in vehicles. This is distortion of the tire tread resulting from the turning forces on the wheel. I did a calculation for the scrub angle from the footprint of my tire (which was a guess), and got 0.4 degrees. I figure I should split that in half for a neutral load and go with 0.2 degrees.
Joe Dunfee





RE: Calculating Toe-in (REPOST)
1 Make certain that the axle of the drive wheel is in line with the radius through the centre pivot.
2 Make certain that the castors have some 'Lead' on them so that the wheels follow their pivots.
3 Make certain that drive wheel is not too heavily loaded
4 get the drive wheel as far as possable from the central pivot
if the radius is large enough I do not think scrub is of any real worry
Hope this helps
RE: Calculating Toe-in (REPOST)
Re #1; We may do just a "tad" of toe-in because we feel that will help the pivot point stay put.
Re #2; In our case, because the set must revolve in both directions, caster lead is not possible. But we are using tri-casters (3 casters on one plate fastened to the set with a ball joint) so we are not particularly concerned with this issue.
Joe Dunfee
RE: Calculating Toe-in (REPOST)
RE: Calculating Toe-in (REPOST)
Joe Dunfee