I was always keen on our team having an elevator. While I doubt our team will have one for a while, I have decided to start to learn using OnShape and try to get an elevator solution which would be cheaper than Greyt while trying to have similar functionality. The price tag for this elevator is $348.
Honestly, I’d do the same with this I’m doing with an AndyMark Elevator kit for an auger/tractor robot I’m building. That is, I’d make the interior risers a bit taller, move the cross pieces out to the ends, and invert the roller brackets so that the side facing rollers are near the ends, and the forward/reverse rollers are in a few inches from the ends so they can’t possibly hit the gussets. This would mean that the physical stops would be hard stops of tube-against-tube rather than bearing-against-gusset or bearing-against-tube. This would be a bit heavier, but more robust in terms of preventing parts damage.
You’ll want something connecting the outter uprights together. Otherwise, they’ll pull apart and everything will fall apart. We had to get a little fancy with an extra bracket (3D printed, as it was low-load) to overcome that with our elevator this year, as we were forced into an open design by other aspects of the robot design. If interested, i can try to find a picture tomorrow.
We used them on our elevator this year and were very happy with them. Much more space efficient, they avoid the issue @GeeTwo talks about completely, and they cost half of what the AndyMark brackets cost.
I 100% will connect the uprights, thank you for alerting me to that! I like those linear bearings a lot, and when I get time, I’ll definitely try to design something with them. It seems like I can cut the cost of the elevator, even more, it seems like I can even make the cost go below $200.
A word of caution: there is a good reason that the somewhat COTS solution you originally referenced prioritizes spacing out the front to back bearings farther apart than the side to side bearings. The front to back will generally be the largest load by a lot (maybe an order of magnitude?), and the force seen by the bearings and the tube wall they ride on will be inversely proportional to the distance between them.
For this reason, most elevator designs of similar style in FRC seek to space the front/back bearings out farther than the side to side bearings when possible.
See picture below for how the bottom corner L-shaped gussets were designed on our 2018 and 2019 robots to allow the bearings to slide down all the way without hitting the gusset.
It may seem trivial, but for every 1 inch you can move your front to back bearings outward, you can gain ~4 inches of travel back overall on your elevator for the same bearing-bearing distance when extended. In a game like 2018 where reaching higher than the opponent mattered, we were glad to have those extra 4-8 inches without added risk of our bearings and elevator tubing failing. Or other way to think of it: reach to the same height with less risk of failure.
My suggestion wasn’t to decrease the bearing spacing wrt rotation around a horizontal axis, but to increase bearing spacing (and more particularly create robust hard stop location) wrt vertical travel. I would much rather have travel stopped by stock meeting stock than by a bearing meeting a gusset.