Round Belting - Solid vs. Hollow, Polycord vs. McMaster

[falconmaster]

Originally Posted by dtengineering

Thanks to everyone for the helpful replies. For 1/4" belting the solid core at McMaster is $.90/ft and the hollow is $1.22/ft. It sounds like we can't go wrong by getting either of them, and it is pretty apparent that the custom welding set up won't be needed.

As for the brand-name polycord at smallparts... well... it doesn't sound like the 400% increase in price ($4.20 in 10' lengths) is worth it.

And the tips on the wide belting from econobelt are good too.

Thanks to all,

Jason

How is the polycord with the grip on the balls? Is it similar to surgical tubing?

[falconmaster]

Originally Posted by dtengineering

I was admiring some of the robots in the 2006 "Behind the Design" book, and noticed that round belting was commonly used in some of the nicer ball handling mechanisms. Team 121 specifically referred to using Polycord belting material.

Searching back through CD (yes... I do search before I post!) I found this thread as the best reference but it was a bit out of date and didn't quite answer the questions I had, so:

1) McMaster Lists both solid core (you join it by welding the ends) and hollow core (you use a barbed insert) round belting material. The hollow costs a little more, but should be easier to join. There is a welding kit for the solid stuff, but it is expensive, and it should be possible to rig something similar at home. Does anyone have sufficient experience with both the solid and hollow core belt to recommend one over the other? Is it as easy to rig up a welding set up for the solid core stuff as it looks like it should be?

2) The McMaster belt material runs about $1.00/ft (more for hollow, less for solid) in the 1/4" size. Smallparts.com lists similar sized Polycord for $4.20/ft (when buying 10 foot lengths). Has anyone experimented with this enough to compare it to McMaster's offerings?

Thanks,

Jason

Incidentally, if you're stuck for ideas on how to play this year's game, you could do worse than read the Behind the Design book. There are some great ball-handling ideas in there.

Is the grip with the polycord similar to surgical tubing?

[Billfred]

Originally Posted by falconmaster

Is the grip with the polycord similar to surgical tubing?

Having handled both lately, the polycord feels a bit grippier. I can't offer you any better insight with regard to hard figures, but there's a difference.

I've had bum experiences with hot plastics in the past, which makes me leery of using any custom heating rigs. That said, I also wouldn't want to use some bum setup with hollow-core belts. Has anyone had bad experiences with them in an FRC setting?

[Kevin Ray]

Falconmaster--
NO, Polycord or the less expensive versions are very different than surgical tubing. Round belt urethane belts are MUCH less elastic than surgucal tubing. The are also, however, less "sticky", but far more than enough to move the 2009 game balls. Surgical tubing stretches too much and is a bit more difficult to attach to itself (Although a volunteer at Hartford Ct regional [can't remeber his name] told me the perfect way. Roll the surgical tubing back on itself and put 1/2 of a one inch section of pneumatic air hose from the KoP up to the edge. Coat the edge of the tube with Crazy Glue then roll the tubing onto the hose. Repeat the process with the other end of the surgical tube and the other half of the hose and you'll have a closed loop which will NEVER break at that point.)
We prototyped the round urethane belt conveyance for this year and it moved it beautifully. The key is deciding if you are going to have one set of belts roll against a stationary wall or have two belts rolling the ball between them. Both worked for us, obviously one is twice as fast as the other.

One mistake many people may have when first trying to adhere two ends together is to heat with a simple flame and hold them together. Using a short (6" or so) length of aluminum angle to maintain allignment, heat to a liquid melt then touch together and pull apart about 1/16 to 1/8" . This is crucial. Failure to do so may give a false sense of adhesion. The separation prevents the hot urethane from being squeezed out by the non-melted belting.

Don't be intimidated by the product. We've used it in '06 and could gather the small balls going 12fps, as fast as we could drive over them.


I hope this helps you. Any questions... message me and I'll help out as best I can.

[falconmaster]

Thanks!

[GBIT]

I have to coment on the post by Tom I. He is a friend of mine and he and i have had a change of heart with the bonding of the belting... though i would still not recomend it for a belt it works great bonded to a flat piece of the same material. we used this to make the fingers for our collector this year...

just my two cents...

[Chris Fultz]

Originally Posted by Ice Berg

I also just noticed that the green stuff is $5.40 per foot as opposed to the other ones that are $.99 per foot.

some of the cord is reinforced, some is food grade, some is smooth surface, some is rough surface.

the material that is $5.40 / foot is reinforced.

[ebarker]

datasheets are here, food grade and non-food grade

http://www.habasit.com/1976.html

[Darren Collins]

I have a question about what rollers people are using with the polycord. Specifically for the drive roller and then the idlers. I had thought pvc pipe, but I presume there are other more elegant solutions available. Thanks.

[Stephen Kowski]

Originally Posted by Billfred

I've had bum experiences with hot plastics in the past, which makes me leery of using any custom heating rigs.

custom heating rigs like the one you saw me successfully using friday?

if anyone wants to try this with the solid core go ahead and save yourself some money and buy "Weller®/Portasol® Super-pro Self-igniting Butane Soldering Iron Kit"....it has a chiseled tip and work like a dream, plus its like $60 as opposed to $500

[Billfred]

Originally Posted by Stephen Kowski

custom heating rigs like the one you saw me successfully using friday?

Custom heating rigs like a fresh-cut 2007 kit wheel that burned the heck out of a couple of my fingers. I'm not saying it can't be done--safely, even--but I've just got my biases about the matter. Call me paranoid.

[Gdeaver]

I believe I have found a vendor that is cheaper than Mcmaster and trust worthy. I'll post after checking thier stocks tommorrow.

[Kevin Ray]

Dcollins
We've milled ours out of delrin rod (lucky enough to have a sponsor who gives us just about all we want). For those less fortunate, you could use schedule 40 plastic pipe with grooves cut, that's a common method. You could also use 1/2" shaft with plywood pulleys. It's simple enough to turn on a lathe or milling machine. There's lots of options.

[Woodworker88]

Originally Posted by Ice Berg

Someone mentioned that the green was more rough than the other colors, it also happens to be the one that needs a larger pulley. Is this because it is more rough?

No, it needs a larger pulley diameter because it is stiffer. The fact that it is rougher is separate and not really related.

[ChuckDickerson]

Back at the Atlanta Championships in 2006 I got a sample of some yellow polycord for a team (sorry I don't remember which team) that is very rough almost like sand paper. It is 1/4" in diameter. I am not seeing something like it at McMaster but it is hard to tell. Does anyone know the exact stuff I am talking about and where to get it? Maybe a part number? McMaster says the metric stuff is "rough" but how rough? It doesn't say about the texture of the inch stuff. What polycord products have teams used successfully in the past? We can't afford to buy a bunch of this stuff to try out so need to limit the selection.