Join Date: Jan 2008
Location: Upstate NY (Mohawk Valley)
Re: Daddy's Dog House
As a past and occasionally present radio installer, I have LOTS of experience with pulling wires through vehicle roofs with a snake. I'm not the kind of installer that always puts antennas over dome lights, but the kind that drills blind holes where the antennas SHOULD be, and snakes cables from there. (Besides, the heat from a dome light can cause internal shorting in antenna cables.)
I don't know if you used the old flat steel or the newer fiberglass snakes, I always used the steel ones. Some tips:
1. For difficult pulls, don't try to work the snake with the storage reel on the end. Cut or snap off a piece to work with. I think the piece I use in vehicles is only 8 to 10 feet long.
2. If there is a narrow gap between the roof and braces that the flat snake slips through, try another route. Without the reel on the snake, it should be easier to twist and turn it to 'walk' it another direction.
3. Make a rounded hook on the end you are pushing through, and bend it closed into a loop. With good pliers and a gentle hand, you should be able to make the front of the snake about 3/8" round without snapping the steel. The rounded part can be used to make the snake follow a brace, edge or sheet for steering the snake. It will also discourage the flat snake from slipping through a seam that the wire can't follow it through. A loop is also more likely to follow the outside of insulation (not guaranteed), where the flat snake will punch a hole through insulation before you know it.
If you are working near hidden wires or insulation, close the gap with electrical tape where the straight part of the hook touches the back. You don't want it to snag the wires or the insulation when trying to retrieve the snake for another go. I think you know what I mean. If you do think you snagged something, don't pull harder. Push the snake forward a smidge, and then twist it 90° or 180° so whatever was caught is out of the hook and try again.
4. If the clearance is tight, once the snake is through don't try to pull the whole diameter of the wire through attached right at the hook. The junction at the attachment may be too fat, and have no flexibility for curves. It is depressing to spend 20 minutes or more getting the snake to come out the right holes, and then have the wire pull loose from the tape on the snake when the clearance is tight. A couple of options to make this go more smoothly on REALLY difficult pulls:
-a. strip the jacket of the cable back, so the exposed wires from inside reach from hole to hole. Make a loop in the metal part of one internal wire and solder it, or solder two wires together, and connect the loop through the hook. Tape it well (but slim and tight), starting on the snake and finishing on the cable. Wrap each step-up to a greater thickness with tape for a smoother transition and prevent getting the 'step' caught on an edge. For a multi-conductor wire, you might pull one, then two, then three internal conductors, followed by the jacket, each at a different distance back from the snake. If dealing with just one corner, the steps might be 4-6 inches apart, If the whole pull is hard (like penetrating fiberglass insulation batts) having the step-ups 3-4 feet apart might work better.
-b. connect mason twine to the snake, and use the twine to pull in some 1/4-inch braided nylon cord, and use the cord to pull the wire. Have the twine and the cord long enough so you can pull the wire through without either end of the cord disappearing into a hole, so you can set up a 'do-over' if needed without going back to using the snake. Another option would be to use telephone wire instead of twine and cord for the pull string.
-c. attach the head of the wire not at the loop, but well up along the body of the snake, and tape it to the snake in multiple places. This does not always work as well as a. or b., but is quicker if the resistance to movement is minimal and the route has no turns. And if you do it far enough up, the snake hasn't disappeared into the hole as the wire passes through its route.
-d. When taping a wire or cord to a snake, don't just go around the two of them, but start with several tight turns on the snake alone to get some gripping and pulling power, and then add the wire in afterwards.
-e. use pulling lube if you have it, or silicone grease, vaseline, etc. Sometimes even wetting the jacket of the wire a little helps with lubrication. I have been known to spit a little on smaller wires from time to time. But to be honest, most of my work has been dry pulls.
5. If possible, have a helper, or use two hands (I've been known to use a foot) in order to keep some gentle tension on the wire as it goes in, so it stays in the direction of the pull. If there is a 'catch,' try backing up 2-3 inches, giving a little twist to one or both ends, and then pulling again gently before initiating the 'last resort' brute force pull. On some routes, the helper can also 'push' the wire a little to prevent it from catching on the entry hole, or to keep the cable loose going over a rib. Sometimes the snake just guides the front of a pushed wire, but more often it pulls. A pushed wire, by the way, is much less likely to get snagged than a pulled one, but is more likely to wander away from the direct route into some unknown crevice.
You may already have your second wire run, but maybe some of these tips will save someone else's bus from getting a pummeling.
Someone said "Making good decisions comes from experience, experience comes from bad decisions." I say there are three kinds of people: those who learn from their mistakes, those who learn from the mistakes of others, and those who never learn.