3946 used strips cut from teflon sheets for lift bearings in 2015. We put more hours on that robot than any before, and likely as many as any since, our 2018 off-season robot being the possible exception. There was no discernible wear on those sheets after an intense practice season, a fair competition season and a bunch of off-season demos.
Edit: we did not notice binding, but we did have two chains on the lift. If we’d had a single chain down the middle, this would have been a problem. There was enough friction in the system that it would stay in place with no totes, but some of that may have been due to chain misalignment.
We did delrin blocks on powder coated aluminum in 2018 and it was good enough for a DCMP win as a primary scale bot. Yet for 2019, my recommendation is that if you can do bearings, you should.
The blocks held up ok, and were low ‘enough’ CoF that we had a great elevator that could also handle a climb. The elevator was fast enough for us in 2018’s game. Yet since this year’s game needs more lightning-fast elevator action, bearings are the way to go.
We used delrin blocks on a single stage lift system in 2015, but found that even the small amount of side load on them caused varying resistance and sometimes would bind up. The varying resistance was annoying due to the lift sometimes working slower one one side than the other if there was more load on one side. Now obviously the system could have been balanced better, but with an elevator with multiple stages you will probably see a higher side load than we saw when we used it. We ended up swapping them out for roller systems. The biggest problem with blocks vs. bearings is that the blocks slide, while bearings roll. Generally a rolling motion will be smoother and have less friction. So I don’t think your main problem would be longevity, but most likely speed and binding.
If you’re looking for a team who uses delrin bearing blocks on their elevator, 25 nearly always does if they need to lift something. Their design has been iterated over the years but has remained functionally the same since 2007.
Alignment, rigidity, bearing spacing, and drive location vs load will all play a huge role in the bearing load… and therefore the performance of the system. Optimizing these parameters can allow for the use sliding vs rolling element bearings.
Sorry its been a while but I’d like to give an update on how things went through the season. We went with delrin blocks but with embedded ball bearings. They were light and easy to machine. Just required some profile work, holes, and slotting on top and then we flipped them and faced off the back side. Only thing that was slightly annoying was doing the holes in the side, which were done by taking the head off of one of our mentor’s aciera mills and running it horizontally. Making 16 of them for two robots was a snap. However, we did have some concerns about their strength. With a fully extended elevator and a robot traveling at max speed speed into a wall, they have to sustain a lot of force, so we decided to make some spares out of aluminum after build season. We made 8 (enough for one robot) and I adjusted our feeds and speed in Fusion360 to machine them. However, after several hours of practice bot time, everything seemed to go smoothly and all the original delrin blocks worked great until we unbagged and fielded the robot at San Francisco. Our first event was extremely troublesome in many different ways due to inadequate stress testing, the most dramatic result of which was this/this, which occurred when our elevator lost its zero and spontaneously went all the way up when I pressed the hatch level two set point. We then hit the edge of the level 2 at full speed and the whole thing came crashing down. Luckily, we scavenged all of the parts off the field and were able to install the aluminum replacement blocks in ~15 min. The delrin blocks are still in use on the practice robot and the carriage of the competition robot. The overall design of the bearing blocks worked out pretty well
but could have been better. I think I were to do it again, I would make them out of aluminum and I would prefer to use larger ball bearings as the small ones made assembly/disassembly troublesome and created some problems with friction between the carriage and the intermediate stage.
Our team on two different occasions implemented a combination of the “Delrin slides vs. Roller bearings” theme by successfully using shouldered Delrin rollers spinning on shoulder bolts. The rollers were similar in design to those now used in the Rev Elevator kit, but were scaled more to the size of the roller bearings commonly used.
Each shouldered delrin roller provided 2-dimensional limit and so, eliminated the need for one set of roller bearings. Rugged, light and simple.