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

[Ice Berg]

So I've been searching for these on McMaster, and I've narrowed it down to 3 colors. One of these colors (green) has a larger minimum pulley diameter than the other two. Aside from obviously needing to use a larger pulley, what does this mean about the belt itself? 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?

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

[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.

[JesseK]

Originally Posted by D 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.

We have a couple of igus rods from previous years (3/4" diameter iirc), so we'll add that to this year's rod and use those for our rollers. If you can mill a keyway in the rod, it mates perfectly with the black plastic hubs that attach directly to the window motors. If not, then perhaps you may get away with drilling & bolting through the hub and rod.

This simplicity is our only reason for using these rollers.

[DeMentor]

I just wanted to say "thanks!!!" to everyone posting on this thread for all the useful ideas. You saved us a lot of time. Will try some of the polycord and see how it compares to surgical tubing for our intended design in a quick mock-up.

[Gdeaver]

Grainger has good prices on 50' roll of 1/4" round belting, If teams haven't already ordered.

[Kims Robot]

Slightly different topic, but has anyone compared V Belt to the Polycord? Has anyone USED V Belt on a robot before? We found tons of examples of teams that used polycord, and have even used it ourselves, but have been experimenting with V Belt in our initial prototypes. It seems to work well and slip out less, but one of our mechanical engineers was thinking that as its used it has more potential to come out of the pulley...

Any thoughts?

[Chris Fultz]

Originally Posted by Kims Robot

Slightly different topic, but has anyone compared V Belt to the Polycord? Has anyone USED V Belt on a robot before? We found tons of examples of teams that used polycord, and have even used it ourselves, but have been experimenting with V Belt in our initial prototypes. It seems to work well and slip out less, but one of our mechanical engineers was thinking that as its used it has more potential to come out of the pulley...

Any thoughts?

We have used synchronous belts - they work well, but you need to design around a standard size and alsignment is critical or they will walk aout of the pulleys. V belts would be more tolerant, as they are continually being 'forced' into the v-groove. However, v-belts 'seem' to stretch more, because as they wear they get seated deeper into the pulley.


Regarding poly-cord like belting - the recommendation we received is 8%, and that is working. The belts are stretched to install but are holding up well (so far).

Also, both McMaster Carr and Durabelt provide minimum pulley diameters for each belt size. For 1/4" cord, MMC recommends a minimum of 2", Durabelt recommends 1-1/2 - 2", depending on the load being carried.

[purduephotog]

Any Durabelt distributors that you can point me to? I struck out- ours in Rochester moved.

What's the cost per foot (100 ft min is what I'm told).

Now to find cheap pulleys...

[artdutra04]

Originally Posted by Gdeaver

Grainger has good prices on 50' roll of 1/4" round belting, If teams haven't already ordered.

As advice to any teams looking to save money by purchasing round belting from Grainger right now: avoid it. 228 purchased 100 feet of 3/16" orange round belting from them almost a week ago, and despite being listed as "in stock" on their website we just received an email that it won't be shipped out until the first week of February.

Since this will be too late to really help us (except for replacement/stockpile parts), last night we ordered another 150 feet of it from McMaster and it'll probably be in sometime today or tomorrow.

[Gdeaver]

I believe the problem is the 3/16 as to 1/4". They have plenty instock of the 1/4". It comes out of Chicago. I had no problem getting 1/4" . Used will call at our local Grainger to avoid shipping.

[Rosiebotboss]

For clarification purposes, the 'round belting" we are talking about as actually called what?

In the McMaster online catalog I found this, EPDM Rubber Cord and Polyurethane Cord. Is this the 'right stuff'?

[Brandon Holley]

Originally Posted by Rosiebotboss

For clarification purposes, the 'round belting" we are talking about as actually called what?

In the McMaster online catalog I found this, EPDM Rubber Cord and Polyurethane Cord. Is this the 'right stuff'?

Mcmaster P/N# : 59725K704.... this is the same kind of 'stuff' your looking for.

This particular variety is 1/4" dia., orange in color (which is slightly softer durometer and matches rosie's colors ), and a 2" min. pulley diameter.

You can pick whatever variety you actually need.

[Rosiebotboss]

Yeah, that's the stuff. I must have had a brain cramp. I couldn't find it. Thanks, Brando.