securing the electrical harness

[cancsco]

Hi,

What would be the best way to secure an electrical harness on high vibration components. I have tried using tie-straps and P-clips and everything seems to fail as the braid on the harness gets cut into and is cutting the insulation on the wires after some time.
Thanks
Nick

 

[MikeHalloran]

Plastic cable ties should be tightened with care, or better, with a controlled tension cutoff tool.







Mike Halloran
Pembroke Pines, FL, USA

 

[pauljohn]

Clamps or P-clips with the rubber strip around the inside, available in any marine store. Or make them yourself out of hose and regular clips.

 

[IceStationZebra]

First - I don't like braided harnesses. They are a pain to service and in my off-road applications we didn't save enough over split loom to make it worth it.

Second - Were the P-clips plastic coated or metal only? I have a lot of good experience with plastic coated P-clips holding slit-loom covered harnesses on forklifts. Non-suspended & solid rubber tires = lots of vibration. My theory is that the slip-loom still allows the harness to move around so you generally don't put a lot of wear or stress on any single conductor.

Third - Other possibilities: closer P-clip spacing, harness "tray", some type of clip braided into the harness (support from within instead of trying to carry. Also good for assy.)

BTW - We banned tie-straps where ever possible due to the manufacturing variabilites (routing, harness tension, tie-strap tension, etc.).

IceStationZebra

 

[patprimmer]

Plastic "P" clips at close interval.

Some form of conduit, like spiral of nylon or PVC hose or split tube as already suggested.

Regards

eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[evelrod]

I do a bit of wireing in 'high vibration' settings. I have used the plastic 'P' clips, but they die after exposure to sunlight or heat...as do many of the cheaper 'tie wraps'.
Typically I use Adel clamps that I get from aircraft surplus (their pretty pricey retail)...usually about two bucks a pound in various sizes.
The tie wrap situation is also curable with aircraft suitable quality (you won't find them at Wal*Mart, sorry) and the proper installation tool. If you don't have the tool, be sure not to make the cable tie too tight.
One trick I use on trailers is to use fuel or vacuum hose as a conduit held in place with properly sized Adel clamps...not suitable for engine compartments, though. I still tape my harnesses, even though it's very difficult.

Rod

 

[patprimmer]

With plastic cable ties or "P" clamps, you need nylon, not polypropylene.

If the potential products are not labelled, there are 2 simple tests.

Firstly, throw them in water, nylon always sinks, polypropylene mostly floats unless it has some fillers, which is unlikely to be the case with cable ties.

Another test is to burn a small piece and smell the smoke. Nylon has a distinctive strong smell like burnt feathers or a bit like celery. Polypropylene is fairly bland smelling like candle wax. If you do it once with known samples, you will never forget.

Polypropylene will fail at a little over 100 deg C while nylon will withstand over 200 deg C. Natural nylon will outlast polypropylene about 4 or 5 times in sunlight. Black colour will help both re UV light.

Regards

eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[cancsco]

Thanks a lot guys,
That was a valuable information.
Coming to my situation I am using straps (Nylon) at some location and I had seen that the harness basically moves and the strap is cutting into the harness.
I have also use P-clips, but because of different sizes of bundles I have to size them correctly and use almost 60 to 70 different clips. Does anyone face the same problem, and if so how did you resolve it.

Thanks
Nick

 

[evelrod]

Thanks, Pat. You do remember that I really sucked at Chem, don't you?

Nick, I still prefer the Adel clamps as they do not cut into the wire bundle or harness like the P clamps often do.
As to 60+ clamps---try a conduit of some sort. The many different sizes??? Sorry, that's just part of the game.

Rod

 

[pauljohn]

Nick

We use nylon cable ties on boats all the time and they are subject to movement and vibration 24/7 sometimes for weeks at a time and I haven't seen this problem unless the harness isn't secured properly.

There has to be movement before there can be abrasion so is it possible you are not tightening them enough or are not using enough of them. We usually secure every 12 inches.

I pad out the smaller diameter bundles with hose so I don't have to carry small clips. It's easy to slice off an inch of hose and tuck it under the cable-tie, protects and looks good too.

 

[pauljohn]

Forgot to mention an important point. The reason I prefer cable-ties is that I can go back later and re-tighten after the bundle settles out a bit. (this is easier if you don't cut the tail off.) A cable tie has a lot more adjustment than the other clamps that I have seen.

 

[patprimmer]

I use nylon cable ties on looms on circuit race flat bottom boats.

They really bounce around with gut wrenching force. Also engines are solid mounted so there is high frequency low amplitude vibrations from the motor and low frequency high amplitude vibration from wave impact.

I always wrap with loom tape and tie tightly to frame members.

Do you wrap with loom tape.

If so, is it possible to reinforce the loom with steel wire also taped into it.

Regards

eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[thruthefence]

MS21919DG-XX adel clamps. "X" being the diameter of the harness or tubing you are securing, measured in 1/16 inch increments. That is, a " -8 " clamp fits a 1/2 inch diameter harness; a " -16 " a 1 inch diameter, etc. There is an FAA advisory circular, AC43-13 2B , that has some excellent data on wiring installations & inspection. As a government doc, it should be available on one of the .gov web sites.

regards, Steve

 

[BrianR]

Have a look at Digikey and search for "Non-Fraying Expandable Braid Sleeving". This is very similar to a product used successfully on military aircraft harness design. The harnesses are then clamped using rubber or PTFE lined P-Clamps as frequently as needed to keep them from chaffing, but at least once every 2 feet.