I wouldn't put my eggs in one basket here.
Delrin over metal (the cost cutter too
), needle point axles and the smoothness of those needle point tips vs PW straight tips. Then there is wheel tread taper contact area and wheel side thrust effects now being applied into them. The rolling stability, less toe in/toe out, wobble & the loss of friction points in a press fit wheel, are all present.
In order? Id guess the roll & re-delivered side thrusts #1, delrin, and tips are the next real keys. Wheel friction at the axle, then finally, the contact patch size on the rails last.
Id give the position and angle with side forces applied better, more credit than the contact patch size. The "flat" isn't really flat anyhow when you consider all the deviations from square possible, to have much more contact friction on a rail than a FstAngle at any given moment, and I think the wedge shape gains static friction vs flat a bit by shape/gravity alone maybe enough to negate the extra contact of the flat.
IE, I think movement, and angles are left after taking "O' razor" to it.
Any physics majors?
