Trailer Wiring

[clevinski]

Hello, All,

It's been a while since I've posted. The spring/summer has kept me busy with fishing and I haven't spent much time with my welding. But now I have a specific issue that combines the two...

A friend noticed damage to a cross-member on his boat trailer. One section of the piece seems to be rusted through, AND the weld holding it to the side of the trailer is broken on both side. I'd like to replace the cross-member with a new one, but I'd really like to do that without having to rewire the trailer. Does anyone have any tricks to protect the wiring during the welding? One buddy suggested pulling the wire taut, on the theory that it will then be suspended in the middle of the channel and not in contact with any metal, but that's probably a long shot.

In case it's not clear from the photos, both the side frame and the cross-member are box material, not a U-channel that would give me access to the wiring from the bottom.

Many thanks for your input!

Charlie

 

[the snooper]

only guaranteed safe way is to pull the wire out of the box and and re-thread after job is done the plugs are easy to rewire.
if you "could" pull the wire tight enough to be suspended in the centre of the box chances are it would damage it anyway not to mention radiated heat .

i suppose if you could fill the box with water it could help but not sure if the water would affect the weld penetration due to the cooling effect on the box.

 

[KTMMICK]

Why not just put a new crossmember in front of it. There is no benefit from welding it up.
Another way would be to mount the wire on the outside, then next time it rots out it'll be easy!

 

[scarecrow]

probably the best way is to take the plug off then tie some light wire to the end of the plug wire and pull it back past where you need the weld if you get stuck rewiring the plug I can give you the numbers for color coed I would be more inclined to cut the crossmember out as it sits on a stress point and I wouldn't replace it with box I would use Channel or angle iron as it would flex more than box and be less likely to crack the Welds as you can see that one is split up along the weld

 

[wyn]

Interesting problem...It looks like every time you reverse the trailer into the water to float the boat off, the trailer chassis will fill with water. The main chassis rails probably drain easily enough, but if the crossmember has no drain holes it would only be able to drain as far as the level of the holes through which the wire runs into the main chassis. So that crossmember may contain water all the time.

Maybe as the others have said.. welding angle or channel in front or behind it (or both) would be the easiest....nothing to hold water. Cutting the box out and replacing with channel might be the best option, but would need the wiring pulling out of the old box.

 

[clevinski]

Thanks to everyone for their input!

There are no wires in the cross-member, only in the main rails. The back of the main rails are open so that the water can drain. However, once there is a single hole, crack or whatever in the cross-member, the water will only be able to drain down to there, as Wyn says.

I like the idea of using channel or angle to reinforce or replace the existing member.

I'm not concerned about the electrical portion of rewiring the trailer, but I'm not sure of the best way to snake the harness. This trailer has lights on both sides where shown by the red circles in the attached photo. (This photo is from the web; the actual trailer is a bit less complicated, but the layout is the same.) Therefore I assume that the harness is snaked down both main rails, and it seems to me that the only way to remove it is to disconnect all the lights and pull it out from the front. Any thoughts on this?

Thanks again to everyone for their help!

Charlie

 

[wyn]

Maybe you could take one of those bolts out and poke a bit of wire through the hole to hold the cables out of the way while you weld it.

 

[paulduncan]

get your hands on a foam fire extinguisher and as you weld fill the area on the inside of the box section with it. because it is foam it have very little water content and will not damage the wiring ar disrupt the welding

 

[Robotstar5]

get your hands on a foam fire extinguisher and as you weld fill the area on the inside of the box section with it. because it is foam it have very little water content and will not damage the wiring ar disrupt the welding

Foam extinguishers will have over 90% water in them.

 

[scarecrow]

I still think wyn is the best just take out the all and pulled the cables to the opposite side of the box then just try and keep the welds short and allow to cool you could possibly use some compressed air to help with the cooling process

 

[clevinski]

My buddy works for a company that modifies containers and so has a number of welders on staff. They volunteered to do the trailer welding for him so I was off the hook. They ended up adding an additional cross-member and welding brackets on to the existing one. Unfortunately, the attached photos were taken after painting, but you can still see the weld job, which was done with a stick welder. I'm no expert, but I'm curious about everyone's opinion of these welds.

Regarding the wiring, they decided to try welding without removing the wires, on the theory that if the wiring was damaged it would have to be replaced anyway. Surprisingly, the wiring survived with no special precautions, other than "welding fast" as my friend was told. I think it's just dumb luck, but it happened on both sides, so maybe not. Then again, I'm not sure that "welding fast" helped the weld quality...

Thanks again to everyone for their help and comments...

 

[wyn]

I can see why you might be wondering about the welding....it doesn't look the best.... but hopefully it will all help to hold the trailer together.

 

[clevinski]

I just won't be following too closely behind him for a few months...

 

[scarecrow]

they do look rough I'd love to see what the under side looked like and im half expecting they didn't even bother with it I hope it was an apprentice
it'll be interesting see if it solve the cracking problem or just makes it worse

 

[clevinski]

I checked the bottom and it was *not* welded. The additional support seems really well fit and the welding looked to me to be adequate, if not ideal. My biggest concern is the patches. Nothing was apparently done to prevent the rust from spreading, so I imagine that the patches must rust out over time. My preference was to remove the original, rusted cross-member, weld flanges on both ends of the new cross-member, and weld the flanges to the main trailer frame (so those welds are made to virgin steel.)

All of which brings up an interesting point. When welding *anything* out of box material, how *do* you prevent rust inside after welding? You can't access the inside of the box after its welded, and you can't coat/paint it in advance because the heat will burn the coating/paint off. Since I've never even heard of someone painting the inside of this kind of box material, I wonder what the usual procedure is?

BTW, this all lends greater support to the idea of using channel rather than box stock on trailers, which someone recommended in one of the posts. Interestingly, I checked a buddy's trailer (it's a different brand) when fishing last week, and found it to be made of channel. The wires are run through conduit mounted inside the channel, and the entire channel is painted on both sides to prevent rust.

 

[wyn]

It sounds like as soon as you use it the gaps behind the patches will be full of water and rusting again.

If a box section is perfectly sealed up, maybe once the oxygen has been used up in a bit of rusting..that's all that will happen. Not that sure really.

 

[scarecrow]

virtually impossible to get an airtight seal on a box cross member like that as the air expands from the heat usually blowing out the last bit of weld.
weld true primary would-be a big help on the inside of the brackets and the face of the box
and anywhere that wasn't welded I would be inclined to seal with silicone
using angle or channel would eliminate the problem and would also eliminate the problem of cracking as they will twist and flex as the trailer rides over rough ground taking up some of the stresses on the welds. box is more rigid which puts a lot more strain on the weld joints

 

[the snooper]

virtually impossible to get an airtight seal on a box cross member like that as the air expands from the heat usually blowing out the last bit of weld.

not if you drill a small hole to let out the pressure before you start then once its cold weld up the small hole

looking at those welds and bearing in mind it was dne with an arc welder have the welds had the slag chiped of them ? if so the guy who did it needs alot more practice or if hes had plenty he should give up