I have seen teams using grippy belts on intakes and some of them look like big flat rubber bands and another type a have seen looks like pneumatic tubing but smaller in diameter. What are these called and where do I buy them?
Urethane flat belting. McMaster or vexpro.
The other part of this is that you buy the urethane belting, cord or tube by the foot and you have to join it to make it a belt.
With the tubing they do sell connectors that insert into the tube to join two ends.
For the belt and solid cord you need to weld it which can be done a number of ways. There are commercially available specific tools for doing it, and you can buy them at McMaster the last time I checked, at the other end of the price scale is just using an open flame. In the middle is a hot blade decal remover like this https://www.amazon.com/AES-Industries-87600-Blade-Remover/dp/B00NEU5JL8
Where do I find the rollers for round belts that have the grooves? I searched Mc master, andymark, and vexpro and can’t seem to find anything FRC sized. I know they exist because I found one in a box of old parts but nobody on the team knows anything about this stuff.
West Coast Products sells them on their Versaroller page, I believe. Looking up “polycord pulley” on McMaster will bring up results.
If you have access to a 3d printer, they’re super easy to print in pretty much any size. All of our 2017’s robot’s polycord pullies and rollers for square o-rings were printed with a thunderhex bore and we never had a problem.
They’re also much less expensive to print if you’re using a lot of them.
What printing material are you using for your Polycord pullies?
I would recommend ABS or better. We outsourced some pulley printing to a nearby college campus printer in 2017 and the cheaper PLA they used ground down and broke within a day of use.
For flat belt welding we had good success with a heat gun and large angled aluminum to act as a guide so that the joint is straight.
Walk through video of polycord welding
I’ve used PLA pulleys. They work fine. Use good PLA.
We used PETG with TPU in a few places to allow for a bit of deflection. I would recommend against PLA as it has a tendency to shatter where PETG deflects and eventually deforms. ABS isn’t worth the print troubles unless you already have a reliable setup.
That’s just not true. PETG is actually quite a brittle material with poor elongation at break and a high crack propagation. Its also a bear to print. I’ve had to replace PETG parts with identical PLA parts after they’ve broken. The PLA parts held in the exact same application. Just use a quality PLA (preferabbly with an impact modifier)
While that’s what the material properties indicate, that’s not the experience we’ve had. PETG filament prints like a dream on our Printrbot Plus Machines and comparative tests between PLA and PETG have favored the latter for the types of parts we’ve printed. PETG out of our printers has fantastic layer adhesion (better than PLA at max temps) and deforms in a very controlled manner only after noticable more force is applied than to the PLA part. I’ve also seem improved impact resistance in PETG, but this is more difficult to compare; PLA shatters where PETG deflects. This seems to be supported by more controlled tests others have carried out. (http://www.youtube.com/watch?v=8_adY2K-YIc)
ABS with the right modifiers and print conditions could yield superior parts in some aspects, but dimensional accuracy and printing complications haven’t often been worth the advantages.
It’s possible these materials had modifiers that skewed their performance and would lead to inconsistencies from manufacturer to manufacturer (or batch to batch), but those results seem consistent across six or so different manufactures and product lines I’ve printed with.
For a small bit of anecdotal evidence, PETG pulleys that we printed for thunderhex shaft rounded out much faster than PLA versions. As best as we can measure the pulleys themselves were identical, but the “less brittle” feel of PETG seemed to allow for rounding to happen much quicker.
Haven’t tried PETG on a regular hex shaft, but I would be hesitant to try it, in anything but very low load applications.