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REPLACING FIFTH WHEEL PLATE AND PIN


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Started on this as early as I could to beat the heat. Somone had replaced it not long ago and screwed it up bad. 3/8" plate with one cross member over the pin and one at the rear. It had bowed up about 1-1/2".

I got caught up on air arcing. Won't need more of that for a while.

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I did one of those once three years ago on a flat bed trailer at work. I ended up using 4x4x1/4" I-beams for cross members above the plate. Seems to have held up well, still in use after three years.

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Mike, that looks good. I always put 1/2" plate back. On this one I am putting 6"X1/2" flat bar standing on its edge 3" in front and behind the pin then 2 pieces across the pin about half way from the center to the edge.  Then we will use 4"X1/2" flat bar on its edge around 6" on centers to the rear of the plate.

Lowboys are extremely hard on plates and pins. 

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If I recall I used 3/8" for the plate and 1/2" for the ramp at the nose of the trailer. I tied that to the channels that are welded to the plate for extra support. Drivers don't like to adjust the landing gear and just let the trailer slide up onto the fifth wheel so I built it to handle that.

You're right about low-boy trailers and abuse. I would be interested to see pictures of your repair if you have time while you're doing it.

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Years ago it would cost about 1000 for material and moderate fee for labor. People thought that was outrageous amount. I think the last one I put in on my own trailer was 550 dollars for parts. The plate 6, 8 ft  by 6 inch channel iron and 3 days of cutting and welding. I had to replace everything under there.

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We usually do 3-4 a year, some years none and the next year 7/8. The worst ones are the bull wagons of some box trailers where water/ manure will get in and stand on the plate.  Last year we did one of the soft sided trailers that we replaced every thing from the landing gear forward including frame rails. It was around 11,000 which was more than the trailer was worth. I tried to talk him out of the repair but no luck. He said he bought it new and was gonna keep it. I told him fine park it in a fence row and buy another one. Nope, no go. He has since became a good customer. 

This one will be around 5,000 as we are building a power unit for it so they can use it with trucks without a wet kit.

Hopper bottom rear frames are also a on going thing. They will not stand fully loaded off road twisting and turning, no matter what the brand. I will not touch one anymore unless the owner has someone else pull the tires and axles out and block them up. I can't and will not wrestle that stuff anymore. 

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Air arc is cool. When I worked at Stratton we had a welder come in to repair frames on the park cats. I often got assigned to help him, remove stuff, lift parts hold this grind that, his name was George, but I don’t remember his last name. Nice guy. He used to air arc stuff loose when he just needed to get material gone fast. I remember it being loud and messy. He let me try it a little, was fun but I think i made more mess than anything. 

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I've air arc'd my share on trailers and most anywhere a weld needs removed with my old Hobart engine drive machine. 1/4" carbons are a great compromise for speed and control but you better leather up and wear ear plugs or you'll be burnt and deaf like me.....

I actually favor my Hypertherm PM105 plasma machine for the process these days. It does a great job and is a lot less cost to operate in consumables. I cut the upper flat from my drop deck and installed all new along with a plate of 3/8" with an SKF/Holland king pin. 

Plates last a lot longer when the 5th wheel is kept greased, but beating that into some operators.....

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Salt is what did the one at work in. The sub-structure rotted away and there was nothing left to support the plate and it caved in.

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9 hours ago, TractormanMike.mb said:

Salt is what did the one at work in. The sub-structure rotted away and there was nothing left to support the plate and it caved in.

Typically that’s been the cause for replacement for almost all the ones I’ve done 

 

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Done with plate, will install power unit tomorrow weather permitting. We took all three trucks over to knock it out before it got too hot.

 

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