Hey guys, I’ve been reading a lot of posts lately about teams wanting to do a thrifty telescope but worried about sideloading. I also saw that other than the cf springs, sideloading can be caused by the friction in the end block. I’m thinking about 3d printing ones that have bearing inserts so the end block can have much less friction. Any ideas?
I would grab the stp from wcp for theirs and print it with high infill to see if it holds up. Maybe make the center hole much smaller.
But REALLY i would design the arm like an elevator and power it both up and down.
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I don’t really see a definitive way to do that with the thrifty system and I know many teams dont have the capability to make their own telescope in-house, so I’m currently looking into easy modifications to the thrifty system or someone else to publish their findings
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Doing a cascade using small diameter dyneema in place of the springs should work just fine.
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Reduce the contact patch size (circular vs square or rounded square rectangle) to help with binding/friction concerns.
Of course now you may need to worry about material properties and wear in a location that is hard to visually inspect.
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Ah so putting in the string instead of the springs like a pulley system and then rigging it up like a cascading lift?
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Bingo. Its one of the things we have discussed, though we still have a lot of other ideas on the table. The other benefit is that your controls guys will always know exactly where the arm is.
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Well, I’m definitely going to prototype this ASAP next week since it seems like the easiest solution to fix a huge problem with the thrifty telescope for an arm
That’s exactly what we’re planning. We’ll see how it turns out next week.
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Best of luck to you guys as well! My main concern with this setup is the speed but that is something that can be played around with
Using string, belt, or even a rack an pinion instead of cf springs are all viable options. Some more viable than others… personally, we testing a belt driven system and have a rack and pinion design as an option as well. As for the block, we are probably going to modify one of the delrin blocks on our mill.
I also looked into belt driven systems but couldn’t figure out the best way to make it work with the thrifty setup
You do have to modify both the end block and the climber plate a little.
For the climber plate, you have to replace the cf spring with a pulley, and (as far as i’ve tested) have to remove the bearing on that side so the belt has clearance. The end block has to, at the very least, have part of it removed to allow passage for the belt. DM me and I can explain better with pictures if you want.
Let the winch out slowly rather than using a dog or ball shifter, maybe?
We have a set of bearings that we developed last year for our climber. It has bearings in one direction and slider plates in the other. You can see the bearings in the bottom right hand corner. I took this photo to remind me to print some replacement slider plates for testing. I will get a better picture when I get to the meeting today.
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I tested our 2022 2-stage Thrifty Bot climber mounted horizontally with 6.8 pounds of hanging weight. If you keep a decent distance between the 3d printed internal slider and the outer bearings, the sag is not too bad. The total extending length in the video is 34", which is when the 3d printed internal sliders stop against the external bearing blocks. The setup in the video is slightly facing down hill, sitting fully horizontal yields the same results. If we go this route, we will be swapping the 3d printed slider out for a block that has roller bearings.
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If you are looking for lower profile you could probably get away with [ground shoulder screws](Shoulder Screws, 1/4" Shoulder Diameter, 1/2" Shoulder Length, 10-24 Thread McMaster-Carr) and [needle bearings](McMaster-Carr Page: McMaster-Carr). (And even then ground may be overkill)
I tried looking for the CAD in your OA post but can’t find it, can you send it here?
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