CEC Composite Couplings from MSC

Technical Technical Discussion
1

I was wondering if any one had some info on these couplers

We are having some drivetrain problems with our 4-motor 2 speed transmission (technokat design used last year/this year) and am looking to use a flex coupling to solve the problems (some misalignment, and some shock loading)

We saw the CEC composite couplings in MSC page 3558 here CEC Couplings

The problem is we need a coupling to withstand around 250 inch-lbs of torque, and from what i see here they only offer a 1/2 inch bore or larger with that torque rating. We need a 3/8 inch bore.

The reason for these CEC couplings is weight. Currently we are right near the limit, and we cant really purchase a love-joy coupling (at 1.5lbs a piece) because that would take us over the limit.

Thanks for the help.

TC

2

Here’s a link to Fenner Drives CEC couplings:

http://www.fennerindustrial.com/products/cec_ind.html

From looking at their on-line spec’s, the 3/8" bore coupling is rated only to 51 inch-lb. Their 1/2" bore coupling is rated only to 228 inch-lb, which is about 10% below your requirement.

I was concerned that their composite couplings included carbon fiber (which is a forbidden exotic material for FIRST), but from their web-site it appears the composite is nylon-glass (which is allowable).

3

Travis,

You have a keen eye, my friend. These couplings are quite a find. We are using them on this year’s robot and there seems to be no problems with them so far.

One of our students found them in the MSC catolog, and they are great, with the exception that we also needed a 3/8" dia bore.

So… we bought the 1/2" dia bore models (we had the same torque requirements), and we came up with this fix to make them work:

  1. Broach the 1/2" bore of the coupling for a 1/2" hex hole

  2. fabricate a 1/2" hex aluminum piece (from 1/2" hex aluminum stock) with a 3/8" dia bore and a 1/8" keyway in it.

  3. Insert the aluminum “bushing” into both halves of the coupling

Once mounted in place, the aluminum bushings have no room to slide out. We are still using the set screws in the coupling, but if they would happen to back out, it wouldn’t really matter. The thanks goes to super-engineer Mark Koors for making this work.

As for the torque rating, we are also above the the listed torque rating for these beauties, and we are hoping that there is a designed-in safety factor. :slight_smile:

Andy B.

4

Wow, thats alot of work to make these work…

We were hoping we could just throw them on at competition since we cant manufacture anything before.

We will see what happens, might have to leave it the way it is.

Thanks again Andy!

TC

5

Try http://www.mcmaster.com/

Search under “Coupling”.

  1. Scroll down and click on “Chain Couplers”.
    If you look under Mutli-Flex couplings, these would work. The hubs connect to the shaft. The bad part is that the 3/8" hubs don’t have keyed shafts. Another bad part is they only have hubs made out of cast iron. You could try to get the smallest possible hub size, but still it’s gonna weight quite a bit…

  2. Scroll down and click on “Spider Couplings”.
    These have lightweight aluminum hubs available, however, they aren’t keyed again.

  3. Scroll down and click on “Rigid Couplings”.
    You’ll see a nice table format of all the available types of couplings. Do a search for them and see what you find.

If you have the funds, go ahead and check them out. Otherwise, if a keyed shaft is important, you might want to pass…

*I did a search through all the coupling types, and none have a 3/8" keyed hub. Either larger bore size or you’ll have to use set screws.