1675 has now made 3 different versions of WCD with Versablocks and Side Bearing Blocks. I’ll share my thoughts with you all but I am also looking for some advice.
3CIM WCP Shifter with versablock on the outside of the 2x1 with fasteners through VB, through the tube, and into the outer gearbox plate
6wd 4" wheels with center drop
Versablocks on outer wheels
Gearbox was very rigid for the drive (not so much for our alternative use of the third motor slot to run our arm, but that’s a different story https://www.chiefdelphi.com/media/photos/39499). 9mm belts were a problem (snapped 8 or more during the course of the season, I believe, and with them being internal to the gearbox, replacement was a big pain). Versablocks were a good solution for us but we observed some “twisting” due to the eccentricity between the cam and the belt which caused the belts to walk a little bit and actually pop the flanges off several pulleys (which lead to some of the belt failures).
3CIM Ballshifter with WCP Bearing Block attachment to 2x1
4WD with 3.25"
WCP Side bearing blocks on non gearbox wheels
15mm belts outside the frame
Gearbox was very rigid. No broken belts. Never had to adjust the tension all year. Had some issues doing the machining for the blocks but it was worth it.
3CIM Ballshifter with outside plate fastened to half of a versablock and then clamped to the 2x1 with the other half of the versablock.
4WD 6" wheels traction + omni
Versablocks on the non gearbox wheels (the omnis)
#25 chain integral to the gearbox.
Gearbox was not as rigid as past iterations but not to the point to cause any problems. No broken chains. Did have to adjust tension throughout the season. 2014 issue of twisting did appear again, in both versablock wheels and gearbox wheels. This led to sprockets walking, shafts walking, and one wheel dangerous close to coming off a shaft during a match.
I really like the idea of the Versablocks but I can’t help but wonder if we are doing something wrong because I have not seen anyone else refer to these twisting issues that we have experienced. Is it possible we are overtensioning? I can’t recall what our metric in 2014 was for measuring tension (something like deflecting the belt 10% the span length when pushing in the middle with a given pressure) but it was comparable to other C-C belts we’ve done before.This year the typical chain tension was enough to keep it from flapping on the bellypan but not overly tight. We saw noticeable camber on both the gearbox shaft and the shaft on the other end; we removed the gearboxes and tightened everything and reinstalled but saw the problem persist afterwards.
I’ll be doing some deeper analysis into the problem this weekend but it makes sense to me - even with a small eccentricity between the pull of the chain/belt and the point of contact with the cam, there will be a moment created in the shaft. Because the cam and the inner bearing of the versablock pair are essentially collinear, the moment really is only transferred to the bearing on the outer half of the versablock and is then resisted by the campling force of the two bolts holding the block halves together onto the 2x1 tube. We only use 2 bolts two hold the blocks together, not four, so perhaps that is our problem, but that is what is recommended in the versaframe documentation. It seems like the real solution would be to add a counter cam on the outside block but that just feels wrong.