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power cord strain relief solutions

4630 Views 8 Replies 7 Participants Last post by  bikerjay
again, finishing my design, and I hit a snag.

I've seen this discussed in a few places here and there, but nothing too major.

Trying to figure out the best way to allow my power cord to enter my housing, and not end up killing itself after I ride for awhile and handle the light.

few things:
1. I'm using trailtech connectors.
2. I'd like to keep it small. I don't think I'll be able to swing one of the compression cable glands
3. waterproof is always a bonus.

I've seen longer strain reliefs, and rubber grommets, and just wires with zipties on the inside. what works? what doesn't?

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I have been using rubber grommets, then a couple of layers of heatshrink on the wire, and a small zip tie in the housing and have not had any issues with cords breaking, wearing out, or coming out of the housing... and if everything fits super tight together there is no way for water to enter the housing. It is a total pain to get it all jammed together... but seems to work well and does not look too bad!
3 of my builds have just had a hole drilled just slightly (.1mm) larger than the cable size and a tie wrap installed. Then I push the cable slightly into the housing and apply silicone to the cable while rotating it a turn. then I pull the cable back. This pulls the silicone coated section of cable into the hole for sealing. Excess silicone inside the housing is smoothed out around the tie wrap and housing wall. This glues the tie wrap to the housing preventing the cable from twisting. A final small fillet of silicone, smoothed by a finger, finishes off the outside and provides additional waterproofing. 2 of these builds have been in use for about a year now with no problems.

Another strain relief method was used on my micro helmet light

This also used silicone for sealing but needed a clamp as there was no room in the inside for a tie wrap.
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Try Goop instead of silicone. Goop is a urethene, it will fix anything but a broken heart. The silicones that smell like vinegar corrode your electronic parts. You need to let silicone dry throughly before closing the housing up.
OldMTBfreak said:
Try Goop instead of silicone. Goop is a urethene, it will fix anything but a broken heart.
Goop is really good stuff, I hadn't thought about it for sealing lights. I have found that sometimes Goop out of the tube is too thick for the use I need. I have squeezed it in to a small plastic (polyethylene) container and thin it with MEK then use it. MEK thins it OK but there is probably a better solvent as it takes a lot of mixing to get it to a good consistency.
thanks guys. I'm leaning towards just a hole (like vanc said), with a simple fillet or chamfer around the edge. trying to make it low profile and clean.

The silicone was what I was originally planning on doing, but wasn't sure how well it would hold up.
like vanbiker I use a hole just bigger than the cable but I then counterbore it to about 0.5mm larger and use tinned wire wrapped round the cable. Coat it all with sealant and pull it back into the counterbore.
It seals very well and doesn't require any extra space in the light but it does need a thick back to the light - not a problem with mine as that is needed anyway for tapped holes for mounting etc.
fwiw it is stronger than a tie wrap. With a tie wrap I found I can pull the cable out if I try hard enough, with this it starts tearing the outer off the cable before it moves. Probably not a big selling point though as you have to be pretty brutal to make a tie wrap slip.

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Someone posted a link toTurck Connectors, and they make very small IP-67 rated locking connectors.

IP67, locking, and strain relief built right in.
I have a very inexpensive source for cords and strain relief. I simply harvest them from obsolete cell phone chargers. There is a nice molded rubber peace on both ends and the cable is usually just about the right gauge. I just drill a hole the housing larger than the cable and smaller than the end of the strain relief and then gently coat the inside edge and around the hole on the inside and then pull it though until it is wedged into place.
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