Kingpin Barrel Distortion

[AndyF]

Hi!, this is my first post.

I have a six in length of 1Inch ID Mild Steel X 1/2inch wall tubing that is going to be my barrel receiver for a kingpin. It's going to be a boom swivel for a backhoe I'm making.

The HC 1inch pin fits perfectly in it right now with not too much clearance. The barrel will be boxed in a 5/16in plate retainer on each side and welded in(Lincoln Buzz box). There will be a 6inch welding seam running up each side of the barrel, as well as 2, 6inch seams seams up the front of the barrel. I will be making several passes of each seam as I only have 1/8-6011 (@ 105 amps) rod and I'm not that good a welder and this is going to be a very high stress point.

Looking at the barrel from the top, the welds will be 90 degrees from each other.

In retrospect it would have been better to have them bored 10/1000 over to compensate but some tell me even that may not help. Some say to mill out the center of the bore for about 2 inches giving only the tops and bottom of the barrel as bearing surface, but I'm trying to avoid the machine shop, and for full loads such as this I prefer every in of surface mating.

Is there a way to prevent distortion of the pin hole, or is this a serious concern? Is there a chance I need to rebore the hole after welding?

Would filling the barrel with Heat Block(TM) help prevent this.?

Thanks for the help.

AndyF

[Sully2]

Weld it all up and THEN bore it for the fit on the pin that you want.

[smyrna5]

Can't you just put the pin (or an equivalent diameter rod) in it before you weld it? That should cause it to hold its shape pretty well. Also do lots of tack welds and alternate sides so as not to do too long a weld in any one place. That's what I would try anyway.

[Spook2]

Distortion is a fact of life when welding, the best you can do is try to minimize it. I don't know what your limitations are going to be when doing this job but here are a few things you can try.

Heat up your assembly. Give it as much heat as is feasible given the conditions of your project. Don't make it red hot or anything but 700-800 deg won't hurt and try to keep it that way until your job is done. If you heat up your base the less temperature differential there will be between your assembly and the weld joint your working on, and consequently less shrinkage will occur. Less shrinkage means less distortion.

If you've got 6 inches of welding to do, don't do it all at once. As an example: I'd do an inch at the bottom then jump to the opposite side and do an inch at the top. Move over 90 deg and repeat. Keep operating in the staggered pattern until complete. This way you minimize heat input in any given area, and by always jumping to an opposite side you work the shrinkages against each other, hopefully canceling them out (to a point).

If you have a spare kingpin you can sacrifice, install it in the bushing prior to welding. This can help stiffen up your assembly and minimize the warping BUT if you end up with too must warp anyway you are liable to seize the pin inside the bushing. Now you've got potential trouble.

I"m sure some of these guys here will have other ideas as well. Good luck.

[TEK]

I'm thinkin Sully has the answer but if you are dead set on low rent then you might try coating the pin with never seize and putting it in the bore and then welding.It seems like the pin would keep it from distorting too much ,and then, after cool,you should be able to drive the pin out.I have no idea if this is a good idea or not so its just a thought, not a suggestion.All standard disclaimers apply...I would probably do like Sully said. That way, you are sure....

[Sandy]

The inside of that barrel is going to swell if you put any significant amount of heat at all to it. Maybe a little, maybe a lot. If this isn't terribly critical, honing may suffice. The bearing surface may not end up perfect, but then how many hours is this hoe going to see?

[chip hayden]

no bronze bearing inserts?

[precisionworks]

Is there a way to prevent distortion of the pin hole

NO.

Is there a chance I need to rebore the hole after welding?

Yes. In fact, using Las Vegas odds, I'd figure the chance at slightly over 100%

Weld it in, then take the assembly to any machine shop that has a reamer with the OD that you need. If you check the factory fit, you'll probably find lots of clearance between bushing & pin, probably .050 on either side of the pin, for .100 total. Most shops will have a 1.0625" and a 1.1250" reamer. Go with whichever one you like, although the smaller one may cause binding as dirt & grit get into the bore.

Reaming a hole like this shouldn't cost too much. Probably $50 to $100 in most parts of the USA.

[usmcpop]

ENCO has an adjustable reamer that goes from 15/16" to 1 1/16 inch for $21. Don't know if that will work or not.

[AndyF]

Can't you just put the pin (or an equivalent diameter rod) in it before you weld it? That should cause it to hold its shape pretty well. Also do lots of tack welds and alternate sides so as not to do too long a weld in any one place. That's what I would try anyway.

Well, looks like my idea wasn't that bad after all.

I suggested that at the machine shop when I picked up the tubing. The guy looked at me very interested and said he gets a lot of press work by folks trying it.

Still I'm tempted.

Thanks

Andy

[AndyF]

Thanks all for the tips.

Looks like I'll need to take my 1" twist drill out if I can find it.

Andy

[Sberry]

Engineering for single pass welding would help. I would think bending would be the big issue, give it a try, worst thing is you have to fix it. Put a couple grease zerks in and thrust washers.

[garth]

I would not put the pin into it to weld it up 1st because you will get warpage 2nd you will have to press the pin back out and may hurt the pin in the process even bending it. just weld your part up and if you can get a tapered reamer in that size ream it or have the machine shop do it that way it is true and will waer evenly as possible. also if you put the pin in it will work as a heat sink making you have to preheat alot more. hope this helps good luck.

[AndyF]

no bronze bearing inserts?

chip:

Actually that was the first thought that came to me, but most of the amateur mini-hoe builders didn't seem to want the option. I thought it made better sense to replace a bushing than to re-weld in a new barrel.

The other thing I was going to do was cut the kingpin assembly off of the "I" beam of a school bus I have back in the hay field, and weld that in instead of making my own. This way I'd have a ready part number for repairs, and tough as **** to boot.

AndyF

[IRON TO ART]

I wouldn't put the pin in during welding myself. When it is possible welding then reaming would be my choice. Even over drilling it out. As far a the bus Kinfpin goes that sounds like a good option if it isn't worn out.