So I went ahead and threw that tensioner into Ansys...
Put quite simply: a bending moment on a 5/16” bolt, 1” away from the base of bending, of almost 1 ton is not small. In fact, UTS of the McMaster-Carr high strength bolts is surpassed. (120,000 psi)
There are inherently huge loadings. Single shear on the tensioner arm doesn’t seem like such a great idea now… perhaps upping bolt size would do it? Although, just looking at the shear force seen by the bolt isn’t wonderful for fatigue life...
Well. It's been a while, and I've done a lot on designing the drivetrain for RGP006, RoseGPE's 2016-17 Formula SAE car! I wrote it all down as I went, just neglected to post it here. As such, enjoy this enormous post.
6/1/2016: Diff Mount Skeleton
I began work by making dummy reference geometry (planes, axes) representing key interfacing points: chassis tubes, axle centerplanes, and the desired diff mount axis (which will be decided later) and using that to make a skeleton.
The leftmost 1” circles represent chassis tubes, and the tangent 1” circles, mounting points. The 7.16” diameter circle is the pitch diameter of a 36 tooth sprocket; worst-case scenario for fitment. The 7.5” diameter circle represents the brake disc. The rightmost 1” circle is the jacking bar. The 2.19” circle on the left is the pitch diameter of an 11-tooth engine sprocket.
The two 1.25” circles lying on the ends of a slot represent the two extreme positions of a roller on the slot-style tensioning system. Path length dimensions for both max adjustment and minimum adjustment are made, and one is driven by the other as an offset of 2*?”; allowing for any adjustment neccessary to fit a full-link chain without half-links. I explored using a tensioner-arm style system like last year, but in the skeleton, packaging this while still allowing full adjustment was proving difficult.
Brushed DC motors have curves. Their force varies with their output speed. So, DE!
This is a bit of a practice sheet that you can actually use to compute the optimal gear ratio for a sprint for a vehicle powered by brushed DC motors.
