An engineer where I work showed me this nifty solution today. It is a wire ferrule (Digikey 288-1032-ND) that accepts 10 square millimeters cross-section. That’s roughly equivalent to 7 AWG, so two strands of 10 AWG fit nicely. Then the crimped ferrule fits snugly into the distribution block so the connection won’t work loose. http://www.flickr.com/photos/19066595@N03/2235428928/?edited=1
The crimper (Digikey 288-1059-ND) is $188.46. Pricey for a FIRST team, but luckily we can borrow one from a sponsor for a few days.
Hey Richard, please bring that to the St Louis regional!
Will do. The engineer who showed me this is also the lead robot inspector at the St. Louis Regional, so I think he’ll be glad to help teams who want to try it.
Good thing our inspectors don’t have to follow NEC, because that is a code violation. You are only allowed to put two wires into a terminal if it is made for two. They actually make two wire ferrules.
The rules do follow the NEC. The Rockwell block can take two #10 or #12 wires per terminal. If the wire is stripped 5/8" and fully inserted into the block, the wires are well clamped by the block. Any less and the block will actually push the wires out over time. The ferrule mentioned above is a simple way to engage two wires that always will stay together in electrical designs and it makes insertion in mass production easier and less time consuming.
The ferrule listed is only 12mm (15/32") long where it fits into the block, not 5/8" , would that be a problem?
I have no experience using ferrules in this application. I would think that if the ferrule is able to engage both of the high spots designed into the block’s wire clamp is would be OK. It is my belief that teams that do not strip the full 5/8" end up with no wire over the back high spot in the clamp. This in turn, unbalances the mechanism of the clamp just enough that the wire is actually pushed out of the terminal over time. Motion only quickens the process.
Mouser has a nice single ferrule kit, covering 12, 10,
8 and 6 AWG, in a nice organizer containing lots of ferrules:
www.mouser.com 288-1032-ND $79.38
There are twin wire ferrules on the same catalog page.
We tried the crimper from ferrules direct:
www.ferrulesdirect.com FD1006L Long Handle crimpling tool $49
It handles 10 through 6 gauge.