polyurethane tubing

[mutantblond]

after seeing some of the designs at our regionals, we would like to redesign our ball - lifting mechanism using the polyurethane tubing. Can anyone make a recommendation on sizing and/or type? We were told to get it from McMaster-Carr.
thanks,
elaine

[Travis Hoffman]

Hope this helps:

http://www.mcmaster.com/#round-belts...-belts/=19dc3a

You most likely want round urethane solid core belting.

[Collin Fultz]

Team 234 uses McMaster P/N 59725K803. It is kind of expensive, but has lasted two comps with no problems.

In the future, searching may get you a quicker response.

[HighLife]

We're using the yellow 1/4 inch polyurethane shingle routhane tubing from McMaster. Make sure you buy the barbs that hold them together. Don't pay for the $300 welding kit or try to weld them yourself because you'll have belt failures and it's EXPENSIVE.

We have them cut about 10% shorter per foot to make up for stretch. We also have spans of no more than 1.5 feet between rollers.

We've had 0 belt breaks, so they work .

[Aren_Hill]

Originally Posted by HighLife

Don't pay for the $300 welding kit or try to weld them yourself because you'll have belt failures and it's EXPENSIVE.

The kit is not necessary to weld the belts, it can be accomplished with a lighter, soldering iron hotplate etc, and when done with some care will not break on you

http://www.chiefdelphi.com/media/img...b7b10cca_l.jpg

see also the god of polycord:
http://www.chiefdelphi.com/media/photos/33403
all welded i believe, i'll let Adam chime in on that


yeah...lol its good stuff

[HighLife]

We've had a few teams come to us and say that they've tried the lighter method and had belts break on them.

Pay a few bucks for the barbs and you'll save yourself time in the build process and stress later.

[EgROS]

Originally Posted by HighLife

We've had a few teams come to us and say that they've tried the lighter method and had belts break on them.

Pay a few bucks for the barbs and you'll save yourself time in the build process and stress later.

We used a simple fusing technique and have never had any belts break on us despite attempting very hard to do so. We created a simple mold by drilling a hole through a delrin block then cutting it into two halfves down the center of the hole. We then heated the two ends of the cord with either a lighter or soldering iron, placed it in the mold and applied presurre for about a minute.

[artdutra04]

Welding the solid core takes a little practice to perfect, but once you get it down it will not break. We've found that once you melt the ends together and wait five minutes, if you pull on the joint really hard and it doesn't break, it won't break on your robot.

[big1boom]

We welded the solid orange polychord with a standard propane torch.

Just melt both ends that you want to connect
Place them in a piece of Angle Aluminum, with the two ends in contact.
Hold for 5-10 minutes till cool.

This resulted in a weld that was strong enough that two people doing tug-of-war could not rip it.

The welds might not be the prettiest, but they work amazingly, and don't jump off of our pulley's

If I remember correctly, the polychord on our bot had a tension of somewhere more than 30%. (I think I remember it being 35%, but I might be wrong.)

[Phyrxes]

We used the orange solid core from McMaster, heated both ends up with and clamped it with an old ribbon cable crimper that had some small angle added to it. to keep things lined up.

[JesseK]

Here are some intersting tables on Rounthane. Notice that you can see the extra load the stretching will put on your motor, which guided us into our new conveyor motor setup for Atlanta. Previously, we just guestimated everything with conjectures that a motor would or would not work. This data, PINK's recommendation, and the lack of necessity to weld the belting are all of the reasons we're redoing our conveyor with it for Atlanta.

Quick question though -- is the polyurethane cord on McMaster the same as the Rounthane? Usually mcmaster mentions the brand name, if there is one, in the product details.

[AlexD744]

If you are attending nationals, you can find 744 SHark Attack. We used a lot of belting this year and Ralph, our electrical lead, is an expert belter. He does almost all the belting at him company. Feel free to stop by, we melt them simply and they have not broken for us yet.

[surferacf]

I second what HighLife said - The hollow core 1/4" McMaster-Carr Polyurethane Belting (6567K57) and the associated connectors (6567K22) are the way to go in terms of belting. Quick, easy, and relatively cheap.

(That bit about keeping the spans between rollers short is crucial to note as well - We had a 40" run and the bands flexed too much, even with cutting them shorter)

[Collin Fultz]

We have spans of about 4 feet (80 total inches of belt) running moon roks from the floor to our top "hopper". On our practice bot, we did the "welding" ourselves. This is with solid core belting. Through hours of practice, we have had no problem with belts breaking. You just have to take your time and give the weld time to set. It can be done.

[BurtGummer]

We used the 3/8 inch, clear, hollow core tubing and joined it with the barbs. We have had the barbs pop out, so we added duct tape after that incident, and haven't had any problems since. We are also using 3" diameter plastic pulleys for the 3/8" belting.

I had to manually create a key/set screw hole in 2 of our 4 pulleys on the drive shaft, but it was pretty easy to do, even with a hand drill.