Where can you buy the 1/4 round poly belt material that many teams use for conveyor/intake belts? It usually comes in orange I think.
McMaster 59725K732.
You will want to “weld” the ends with a heat gun and a pair of hinged blocks that have a hole drilled in them to clamp onto the melted cord. Pics to come.
We bought a used belt welding kit last summer, we’ve just never used it… :yikes:
Just a side note:
If you have used that particular belting material before, please disregard this post (you probably already know about what I am going to warn). We used the belting on our 2012 Rebound Rumble robot for the Ball Intake and others before it.
If you have not:
- If you create a belting loop for use on pulley’s, etc. (from the hollow core type of belt vs. the solid core type since those solid core type are very different and go on the OD instead of the hollow ID).
You will also need the barbed fittings called “Hollow Core Belting Connectors” also listed there on the same McMaster-Carr page as the belting in the same hollow core belt appropriate size to create smooth loops of the belting.
- Those are very hard to insert into the ID holes of the belting (difficult to push completely in, and always test the insertion grip by pulling after insertion also), but they very workable with proper physical strength applied.
They hold very well most often, especially if the belt is stretched properly (and not over stretched), to maintain proper belt tension. But, they do often come apart during use if not properly inserted & tensioned while used as a ball intake. The larger the ball, the more the condition may exist.
- If you need to shorten a belt later (once the connectors are inserted into both ends of the tubing), those barbed fittings are very salvageable for reuse “if you are very careful removing them.”
They do not pull easily apart once inserted properly, as they dig into the ID wall of the hollow core belting (and doing so -attempting to pull the barbed fitting out of the belting), can get a person hurt easily as that barb is sharp and the belting stretches easily). The snap back can cause cuts and welts - always wear safety glasses. Maybe even gloves if this method of removal is used.
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We usually would cut the belting a small distance away a from the connector 1/8"~1/4" let’s say with dykes, wire cutters, knife, razor knife, or needle nose cutters, and then go to a bench (or other hard surface), and carefully, slowly slice one side or 2 of the belting (cutting away from yourself), between the center of the connector toward the end barb with a razor knife, to then gently get the short pc of waste belting off, making sure not to scar the gripping and holding edge of the barb ends. If you scar the sharp barb edge up, it will no longer hold the belting properly upon reuse.
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Students who we left on their own devices, and not fully educated in this procedure, would often either cut off the barb connector end (since it cannot easily be seen through the belting, leading to no more reuse of the connector), and this required full replacement of the entire connector and over shortening of the reused belting loop.
Or, they would tend to scar up the end and still reuse it, and then the holding abilities were highly or somewhat diminished, and the belting would easily come apart again the very next time (or so), that the ball intake was used to intake a ball, leading to some extreme frustration and sometimes extreme panic of the drive team and others, if it was happening during competition.
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Both the belting and the fittings work very well for the purpose if (big IF), proper education in use and maintenance is conducted. Just a friendly warning.
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I learned that a simple hand held magnifying glass (or a really good pair of much younger & educated eyes than I personally possess), and a simple rotation and visual inspection of each of the connector(s) ends, before every reuse, was absolutely mandatory, with a standing rule of “no failure to conduct the inspection every single time a belt comes apart” if the time permits, and “no other exceptions exist” helped solve our issues in using that particular belting & connectors.
If there was a nick in the barbed end upon visual inspection (a full rotation view), a replacement was considered necessary & mandatory as they tended to no longer hold very well, even if only one side was nicked or scored w/ a single razor knife cut that was difficult to see, etc…
My testing:
After careful visual inspection of the ball intake in normal use (using video that I actually slowed down, and magnified), using multiple belts/pulley’s (both driven and idler pulley’s), and multiple balls in the intake.
I noticed that the belting material was actually not just travelling in a normal pulley driven direction. But, it was also actually rotating in a spiral direction (due to, I suspected), the round nature of the belting catching on the alum. pulley sides, combined with belt interaction with the balls it was transporting.
Basketballs (even smaller foam reproductions), have those lil’ nubs on the surface - so, not all balls may cause this spiral action to the belting - Though I suspect the spiral rotation had more to do with the Alum. pulley/urethane belting interaction (belt rides up on pulley side, then slips down, then rides up again, rinse repeat), than the actual belt/ball interaction, as it existed before introduction/interaction of the balls, but was less pronounced after ball introduction/interaction since we were using the belting on 2 sides of the ball to create a ball elevator).
The belts I surmised, were unscrewing themselves from the connector if there was a nick in the barb, as it (the nick), acted like a bolt/screw thread during the belt rotation that occurred naturally during use of the ball intake. I further surmised that without the balls, the belts rotated in that spiral direction, and after introduction of the balls into the intake, the ball(s) was actually stopping the spiral rotation of one end of the belt (where a connector existed in the belting loops), while the pulley(s) were continuing to cause the spiral rotation on the other end of the belting and the connector, that caused the unscrewing action to exist if there was a nick in the barb.
Close inspection of all the connectors I saw (that came undone repeatedly and were replaced), had a nick or other cut…Some when they were new right out of the package, and some that were human caused later.
So, the cure was to simply be very careful not to nick the barb (and careful close inspection of all of them before initial use, and before any connector reuse)…An easy solution. (The belt welding solution solves the issue I was warning about here).
I wondered why we didn’t just weld them instead of using the connectors, then I saw the price of the welding kit…$730.60 YIKES!
Good Luck.
In your testing had you ever tried melting the hollow core belting together in addition to using the barbed connector? I Feel like this would solve some of the issues of the belts coming undone. But I am unsure if the urethane can be melted together.
Slicing the poly cord that’s solid is usually done via melting. “Properly” with an expensive hot knife kit that hold everything together and allowing to smoothly and easily move the pieces together. More cheaply with a soldering iron flat tip (EDIT: as a CompE this always kind of bothers me and I’d not want this done with a tip I’d use for soldering) and some vices holding the cord in place. Likely a heat gun as pointed out above - though I haven’t done that myself and I think it would take awhile longer to heat up enough.
A quick search pulls up this out of focus video, but I’m sure there’s plenty more out there: https://youtu.be/FmrxY2l2mn0?t=92
I will be posting a few pics of how to weld the solid stuff with a heat gun to melt the ends and an aluminum clamp to hold it together while cooling.
Apologies for the delay.
Step 1: cut the belt to size.
Step 2: heat over heat gun or similar
Step 3: place the now molten ends together with some force into the clamping jig(screw a hinge to 2 pieces of aluminum block and drill a properly sized hole across)
Step 4: clamp the block down on the belt, a second person is advised for this step
Step 5: trim the tabs of squished material off the belt and you are good to go
It may take a few tries to get it right
