Re: Question:Power Distribution Block
 

Bob,
There are ferrules that are available for stranded wire when used with these blocks. They come in boxes of 100 as I remember. This was a point of discussion by some lead inspectors and the issue with ferrules is the derating of the conductor size by 1 AWG, i.e. a #10 w/ferrule has the current/resistance of a #11 wire. I believe that part of the issue is that teams do not tie down the wires near the block. As the robot drives around and gets banged the wires twist side to side and eventually "flatten out" inside the terminal. I am recommending that teams tie down the wiring and check that the terminals are tight after every match. I am sure you can use the ferrules if you choose, without any difficulty other than an inspector may not know what they are. I think the greater problems will come with teams using one #12 stranded wire per terminal. I would think teams would have far less trouble if they doubled the #12 in each terminal to fill the space (as allowed by manufacturer spec sheet).
Another problem some teams may have introduced is using #12 to wire from terminal block to fuse blocks. If you are a team that mistakenly took this approach, you will need to replace the #12 with #6. You can find a detailed block diagram on power wiring on the FIRST website under the robot rules and within the Guidleines and Tips document. Inspectors will help you if you are unsure.
Hope this helps.

Re: Question:Power Distribution Block
 

Thanks Al,
We have tied down all connectors leading to the block and we don't really seem to have a problem I was just trying to find out if I could lead off a potentially difficult situation for our second regional

We are already using #6 wire.... we would do that anyway in order to minimize any power loss that we can. We always use the shortest route and the biggest wire we can use (within reason) to have the least resistance for our bigger motors to pull current through...

I have been around long enough to know that sometimes problems have a way of showing up during the second time we participate in a regional.
Things have a way of loosening up between regionals and when there was no problem the first time usually my mechanics become complacent...

I will just have to discuss this with them and make sure it is on their initial checklist for the Las Vegas Regional... Next year I would rather use ferrules if we use the same block... AND proper strain relief... this year I looked at purchase and you are correct 100 minimum and pretty pricey... 30-40 dollars with shipping...at least pricey for our minimally funded team...

A little foresight beats hindsight any day...
thanks for your always helpful input!!

Good luck to you

R

Re: Question:Power Distribution Block
 

I did a thorough inspection of our robot after UTC, and found NO loose connections, we did not use ferrules, we soldered the ends of our #6 into a solid conductor prior to installing in the Rockwell blocks. Al is right about derating the conductor if using ferrules, that's why we soldered our conductor ends solid.

I would recommend never relying on a terminal screw style connection when using multi-strand (automotive style) conductor. The strands never fully seat in the terminal and movement allows the strands to move around and loosen up even when torqued properly. Also, the larger the AWG size, the worse the problem will be. Seven or nineteen strand conductor shouldn't have the same problem, our's didn't, but you still might want to solder those, too.

Use ferrules or solder.

Re: Question:Power Distribution Block
 

I would not reccomend using solder on the wiring. As Al suggests, ganging multiple 12 or 10 gauge wires in the terminal blocks is recommended and aids retention. We have been through two regionals and have not had wires pull out. We use flexible high strand count wire everywhere, zip tying it to the board close to the terminal with some stress relief. We check the tightness of the screws on the terminal block now and then and have not had anything loosen, but you really want to tighten to specification torque in the first place and not guess on this.

The one place that we used a "ferrule" was on the 6 gauge high strand count welding wire going into the maxi fuse block for the main motor power. We used a crimp on parallel splice that the wire would just go through, hex crimped it on the wire, and then mashed it to get the right shape for good conductivity in the maxi fuse block.

Ferrules will no doubt help, but you don't need them in quantity 100 and you don't need to pay high prices for them. You can get pure copper tube of the right diameter, cut it to the right length, anneal it, clean it, and then crimp it on the wire before putting it in the terminal block and mashing it. If using ferrules on multiple 10 or 12 gauge wires, it is probably best to gang them in a larger ferrule.

For a source of hardened copper tube that would be easily cut, but then you have to anneal it before using it, see:
http://www.smallparts.com/products/descriptions/htc.cfm
and see the following for "half hard" tube that you might not have to anneal
http://www.smallparts.com/products/d...tions/ttrc.cfm

There is always the possibility of drilling parallel splices to just the right
size. You can also drill soft copper tubing from the hardware store.
Drilling copper is not for the faint of heart, but it can be done.

Eugene

Re: Question:Power Distribution Block
 

Art,
I wouldn't suggest tinning the wire before placing in these blocks, there is no chance for the wire and terminal to confrom to each other. It might help to dip the first 1/8 inch of the wire in a solder pot to hold the strands together. Of the teams that I saw with trouble this weekend, all had failed to trim enough of the insulation from the #6 wire before insertion. #6 wire insulation prevents full insertion into the terminal if it is not stripped back at least 1/2 inch.
The ferrules I referred to in a previous post are very soft and thin copper so that they will conform to the outside diameter of the wire with very little effort. I think that the terminal should be given a chance to "bite" into the wire.

Re: Question:Power Distribution Block
 

Mouser has ferrules in quantity one.

see:
http://www.mouser.com/search/refine.aspx?Ntt=ferrule

They have the crimper, too, for a paltry sum of $217.
Man, it seems like a fellow could make some money
by turning out jaw inserts to fit a cheaper crimper...

Eugene