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Yes, another OT KB5 update

T

Tom Fleming

Well-known Member
Progress: Mission, rebuild flatbed to haul up to and including an F-30 or SM.

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4x6 undercarriage. 2x decking. 5/16" carriage bolts. 10,000 lb D-rights, with 5/16" backing plate under the deck. Should work.
 
I have not seen carriage bolts with rating for strength. I would be much happier with 7/16, 0r 1/2" bolts of grade 8. Jim
 
(quoted from post at 16:10:42 09/16/12) I have not seen carriage bolts with rating for strength. I would be much happier with 7/16, 0r 1/2" bolts of grade 8. Jim
Click to expand...

Grainger's website states 125,000 psi for a Gr 2 5/16" carriage bolt. Most are low grade. They do have Gr 8 available. They list the Gr 8 at 150,000 psi. Jim would probably be able to help us apply those numbers.
 
Jim, I tend to agree. I did some homework, and they do make a Grade 5 carriage bolt, but I had to special order them. The D-rings have stainless carriage bolts, and they are within 15% of grade 5. Grade 8 only comes in hex. The stainless bolts on the D-rights are 3/8". The decking boards are held down with the 5/16 carriage.

Bottom line, this is only going to be used locally, and top speed on the old girl is a blazing 47 MPH, downhill, with a tail wind! :lol: Although, I do not take it lightly that a snapped bolt during a quick stop would be disastrous.

Jim, I'll double check the stainless tensil numbers and failure point. I might swap them out.

PS. The D-ring brackets are for 3/8" bolts. I didn't have much choice on the size........
 
Shrinkage. I installed them TIGHT, using pipe clamps. The gaps you see are from the lumber drying out and shrinking. Since this is not going to be a grain bed, I am rather ambivalent on the small gaps. But yes, there are 3/8" gaps.


The original bed was tongue in groove, and red oak. I priced oak and went into coronary arrest. I would have loved to put white oak on it, but the 14' length really sent the price sky high. If it had been a 10' or 12' bed, that is fairly standard length. so is 16', however, that is 2' too long and LOTS of waste (which I had anyway with the treated, but at 1/8 the cost......)
 
The key is the cross sectional area.

5/16 = .076 sq inches
3/8 = .11 sq inches
7/16 = .15 sq inches
1/2 = .19 sq inches
Take each of these times the absolute tensile strength of the material, and factor in safety of 2, then imagine a 6000 pound tractor in a wreck on a trailer. (each bracket is restrained by 2 bolts, but they are in a combination of uneven stretch, and shear.) I would be with the grade 8 1/2 bolts, and my under the deck plate would be welded (outboard) to the frame), and at least 1 sq ft. Jim
 
Oh, I forgot to add in that the threads on the bolt further reduce its cross section, all info is shank only. Jim
 
(quoted from post at 17:14:27 09/16/12) The key is the cross sectional area.

5/16 = .076 sq inches
3/8 = .11 sq inches
7/16 = .15 sq inches
1/2 = .19 sq inches
Take each of these times the absolute tensile strength of the material, and factor in safety of 2, then imagine a 6000 pound tractor in a wreck on a trailer. (each bracket is restrained by 2 bolts, but they are in a combination of uneven stretch, and shear.) I would be with the grade 8 1/2 bolts, and my under the deck plate would be welded (outboard) to the frame), and at least 1 sq ft. Jim
Click to expand...

Hmm, so they are only good for 798 lbs each bolt? That would make the load for the tie down 1596 lbs? Is the saftey factor a mandatory thing or just extra cautious?

Nobody said you had to use the bolts they were designed for. Hex bolts will work just fine in them. They just don't fit nice and flush. I really don't think the bolts will be your problem. I would guess the wood will crack or the bolts will pull through where the wood is fastened to the metal. I would really like the see the tie downs through bolted through the metal.

Tom you and I usually agree, but I don't think a low top speed and local hauls only equals a safe situation in this case. It isn't you that you need to worry about...
 
I do not quote DOT law. I just believe that if a corner blow to the truck bed happened, far more than the tractor weight would be applied to the chain and Boomer on the opposite corner. Jim
 
well guys, you have conviced me. I'll upgrade to the Grade 8 bolts. The other thing you don't see, is that the 5/16" plate under the decking is 12"x8". Good news and bad news is, I considered bolting these to the steel frame, but the bad news is, the steel that is it made from is 3/16", ie. VERY thin, and just a basic skin on the deck, enough to hold the stake sides on, but not really enough meat to take alot of lateral pull/stress........which is why I went this route. Heck I even considered using L brackets to bolt into the cross members, which I may end up doing anyway.

I any case, the bolts will be upgraded.......
 
I agree with going to 1/2" G8 bolts. The load spreading plate was a good idea. Another possibility would be to run a piece of 8" channel diagonally across the corner, tie it to the bed frame and then bolt through that.

I like this project. I still say the cab looks great with its weathered patina.

I've considered a similar project with my '57 Chevy 2 ton so I'm curious; What's the plan for loading?
 
Cen Tex, loading is simple. Bank, as in back up to it and drive on. I have one and of the local shows I would use this for, they all have a bank or loading dock facility. Ramps are just not in the cards. The top of the deck is 40" off the ground, and to make effective ramps would be impractical. Not because I cannot make them, but because their weight and size would require a small back hoe to use them.

I will always have my trailer for longer hauls and need for speed. Heck, I have even considered driving this to the show, then haul the tractor on the trailer, and load at the show for display.
 
Ok, basically the old dirt ramp method. That will certainly work. I still see those now and again, occasionally see a wooden one too.
 
When I hauled tractors on truck with a grain bed I would drop the chain down through the stake pockets and eigher hook it back to the chain or tie it to truck frame. I hauled a 1066 all over ohio and indiana that way. Just a annother idea
 
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