Round Tube vs Square- Boss Plow Repair

[Spencer]

The round tube crossmember that the lift cylinder mounts to recently broke on my ~15 year old Boss plow.

I haven't measured things up yet, but the broken crossmember appears to be around 2" in diameter and having a wall thickness of only an 1/8" or so.

I was first thinking of going to buy some thicker round tubing, but then I realized I already have some 1/4" wall 2" square tubing on hand.

I assume it is safe to believe 1/4" square tubing would be sturdier than 1/8" round tube. I'm wondering though if 1/4" round tubing would be better than 1/4" square tubing.

The top of the hydraulic lift cylinder mounts and pivots to the bottom of the crossmember. Given the same wall thickness, does round or square tubing have more strength?

I'll get some actual dimensions and post some photos later today.

[Spencer]

Crossmember when plow is down and at rest.

[Spencer]

Crossmember with plow lifted up.p

[toprecycler]

The square tubing should be stronger vs round in this instance. And since you are doubling the wall thickness, you would have no problem with bending issues.

As long as the original tube was not engineered to be a weak point on purpose, it would be a good substitute.

The only way the round would be stronger might be if it was holding high pressure inside.


Note, I am not an engineer, I just play one at work.


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[digger doug]

Boss plows....funny story.
About 1995 my friend started selling them here in Erie.
I was looking at a couple of them sitting on pallets, in the summer,
ready for the fall rush season.

I could easily see that one plow was welded with spray, and another (same weld area) was run short arc.

He told me, he had been to the factory, and they work about 6 months out
of the year, and then close down. So one was welded maybe 6 months
before, and apparently they let the welders set their own machines.

Oiy !

EDIT: it was "Blizzard Plows" my bad, but appear to be in the same neighborhood.

[LKeithR]

From an engineering perspective when you're talking about weight to strength ratio round tubing will be stronger. This is especially true when light weight is one of the objectives--there's a reason why race car roll cages and light aircraft frames all use round as opposed to square tubing.

In the OP's case it really doesn't matter--going to heavy wall round or square tube will provide significantly more strength. Personally, when I'm fabricating stuff I prefer to use square or rectangular tube whenever possible because, with flat edges and square corners it's easier to make joints and connections...

[JBFab]

Originally Posted by Spencer

Crossmember when plow is down and at rest.

I would bet money that there was undercut on the passenger side cylinder mount that led to that failure. Not that it matters, I just enjoy looking at those types of failures forensically. Any chance you could get a good picture of the weld on that side?

To your question, in this application the square tube you have would have significantly less bending stress than the thinner round tube from the factory. But the fact is neither come close to the elastic limit of A500 steel. Again, I'm looking for a weld defect, but I suppose it could be fatigue related after 15 years of use.

As with Brian, I'm no engineer either - but I did stay in a Holiday Inn Express one night.

[Norm W]

The tube or square could be braced diagonally to "Beef" up what ever is used. There is room on each side to to do it.

[greywynd]

If you got 15 years out of that one, you’ll get 15 out of the heavier square tube. Well, until something else breaks.

The joy of snow equipment, the stuff only breaks when you need it, and it’s cold and snowy.


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[Spencer]

Originally Posted by JBFab

I would bet money that there was undercut on the passenger side cylinder mount that led to that failure. Not that it matters, I just enjoy looking at those types of failures forensically. Any chance you could get a good picture of the weld on that side?...

Here are the pics you requested.