We started assembling a custom telescoping tube design on the weekend and have ran into one issue that we would like to solve. The design is heavily based after the thrifty bot design and uses the same springs, mounting, and a machined version of the internal sliding block. We used different bearings that we could acquire easier, and plastic bearings on the sides.
The issue we have is the spring scrubs between the 8 mounting bolts and the tube. We also find the scrubbing issue is a bigger problem between the 1" and 1.5" tubes and is somewhat a problem between the 1.5" and 2" tubes. It causes a lot of scraping noises that don’t sound good and on the smaller tubes can cause it to get stuck when the springs should be extending the tubes.
I can upload photos, videos and dimensions later. Tell me if there is something specific you want me to show.
Note: We have also tried removing a little material form the middle of the 8 bolt to give the spring a little more room which helped a little.
How do the dimensions for the mounting of those bolts compare to the mounting dimensions on the TB telescoping tube? We’ve got the TB kit, and I know those bolts are practically in the walls of the tubing, if your spacing isn’t as much, that could certainly lead to issues.
Copied from thirftybot model. Plates and tube were done on CNC. Everything goes together as intended and tolerances feel fine. I can get you dimensions later today. I can tell you the holes are at the edges of the tubing on either side as I expected them to be.
We use the REV telescoping tubes (2" and 1.5")
All our bolts/nuts are tightened in such a way that you can turn them by hand. Since we use Nylocks, there is no chance that they will fall out.
Too tight and your tubes won’t extend.
If you push the tube down and it follows your hand back up, you’re good.
We had a similar problem with our telescoping arms, based on a similar design. We found that putting a little lithium grease (actually Mobil 222 Special grease) on the surfaces of the springs got rid of the problem.
possibly, I was more concerned with the bottom block absorbing some grease and swelling, but we have not seen that yet. So far its working better than without the greese
We added some lubricant this weekend in our climbers after a few sticking issues. Cleared everything right up and neither the delrin or 3D printed blocks seemed to mind much. Traversed in a bunch of matches Saturday afternoon & on Sunday at Kokomo with them.
That’s a good solution too. Essentially what the OP posted is exactly what’s happening - the space is pretty tight for the spring to fit between the #8 bolt and the tube. If that room isn’t there for whatever reason (holes not drilled in a good spot, tubing tolerances aren’t great either) then things can get sticky. Going to rivets will free up space in the center. We loosened our #8 bolts a little bit and added lubricant which worked too.
The original prototype ran in the 2021 off season was all 3D printed plates and 3D printed parts and held up great! I’ve seen a few iterations and variations off the plate design and it’s super cool to see teams making their own versions of them.
This is exactly what is happening to us except for the spacer as we used 5/8OD, 1/4ID Bearings. I noticed the spring when extended curls a bit causing the edges to contact the bolt.
Here are some photos of the two blocks. As you may be able to see the center of the bolt has been reduced in diameter which helped a bit. Going to try a bit of grease.
