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Wiring between main and starter contactor...

Michael Burbidge

Michael Burbidge

Well Known Member
I'm using a short length of battery type cable made by B&C to connect my main contactor to the starter contactor. Both contactors are from B&C. The orientation of the terminal bolts on the contactors does not make for using copper bar easily.

I've enclosed a picture. My question is, do you the think the radius of the bend will put too much stress on this wire? If so, what would you suggest?

Thanks,
Michael-

0c6c6d21bf7c480dbb9f6b2b35486299


21db12cc242c4e8e854c9a762e4815d5
 
Cable

Looks ok to me from here. If you're worried about it, make a new one with welding cable. It is super flexible and should make that radius easily.
 
Bend it

You can shorten the wire and bend the terminal connection over 90 degrees to make a neater installation. That being said, it looks OK as it is as long as it will not rub against the battery box.
 
You probably knew this, but when you crimp the terminals on, make sure they are "clocked" so you don't have to twist the cable when you put the ends on the studs. Don't want to introduce any stress. :)
 
CJ,

Where did you get that copper bar you used to interconnect the contactors and what size/thickness is it? Also, how did you do the black on there, it looks like rubber. Thanks

Matt

Captain_John said:
...or do it like i did with a twist in the copper bar.

IMG_0129.JPG


;). CJ
Click to expand...
 
idleup said:
CJ,
Also, how did you do the black on there, it looks like rubber. Thanks
Matt
Click to expand...

Looks like heat-shrink tubing to me.

p.s. Obviously Jason types faster than I do. My recent eye surgery has slowed my keyboard!
 
Last edited:
Michael Burbidge said:
My question is, do you the think the radius of the bend will put too much stress on this wire?
Click to expand...

No. The minimum radius for a wire is roughly the same as the minimum bend radius for sheet or bar material with thickness equal to the individual wire strand diameter. Put another way, the concern is cracking of the individual strands, just like cracking an aluminum sheet part by using a bend radius that is too small.

You're not anywhere near the plastic region for those wire strands.

Concern about "preload stress" is baseless. Consider your torque-to-length Lycoming connecting rod bolts, or the stress on your landing gear right now, sitting quietly in the hangar.
 
You're probably more concerned about stress on the plastic or composite parts holding the studs. If you "over bend" the wire into the desired shape, thus yielding the wire and permanently deforming it into the shape you want, there is no risk to the attached parts.
 
Hey guys, That hunk of copper came from McMaster.

I ran some calcs on it and am satisfied with it's current carrying capacity. I am away from home and the project right now so I can't get the details for you immediately.

Yes, that IS shrink tube on the copper bus. A little insulation is better than none at all. Not sure if I will insulate it any more than what you see here.

:) CJ
 
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