EDIT - 05.02.2018:
I added versions of the mounts with holes for inserting steel nuts. this gives extra strength and does not strip easily.
A shifter mount for mounting the Thrustmaster TH8 onto the Playseat Challenge racing rig. This is extremely sturdy and will not budge.
TH8-playseat01 is for mounting on the right side
TH8-playseat01-nuts has holes for inserting M4 nuts
TH8-playseat02 is for mounting on the left side (for people who drive on the wrong side of the road ;) ).
TH8-playseat02-nuts has holes for inserting M4 nuts
It clamps onto the tube on the right or left side of the seat using M4x20 mm or up to 30 mm length screws and and the TH8 is secured to the mount with four M6x16 mm or similar length screws. Do not overtighten the M4 screws or the plastic will strip.
Also check out my other sim racing stuff:
Screw assortment for this and other projects. It helps me out a lot if you using one of my affiliate links like this:
Print in the orientation it opens, without support. PLA is good for this.
Two perimeters and 20% infill is enough.