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Discussion Starter · #1 ·
I was wondering what would an alternative to steel 2" DOM .120 wall, round tube. Can anything be had in aluminum that would be the same OD and of relativly the same strength? And any idea how much more expensive it would be over regular DOM?
 

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Pure aluminum will never be as strong as steel, in the same shape. You'd have to use solid bar to even approach the same strength level, and then you'd lose the weight savings. Aluminum is also a lot more expensive, pound for pound.

You'd be a lot better off to use simple HREW steel tubing. You know, the kind with the visible seam. It's pretty much the same strength as DOM, but the finish and "roundness" aren't quite as good. HREW tubing is a lot cheaper than DOM as well, and you can bend it etc no problem. Lots of guys use it for roll cages, tube frames, and whatever else.

Chris
 

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Discussion Starter · #3 ·
I was under the impression that HREW was not as strong as DOM in the same dimenssions. And I just noticed that I mentioned Aluminum, and I should have said Al/Alloy... but I don't know if that would make any difference either. This is what I had found...
  • 6061-6511 extruded seamless AL tubing, OD 2" wall 1/8 or 1/4.
  • Also found 6063-T6 drawn seamless OD 2" 14 gauge (0.083 wall), this last one is obviously not what I'm looking for.
I was hoping that the 6061-6511 in a 1/4 wall would have offered the same relative strenght in a short lenght application of no more then 60".
 

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As far as pricing goes I have found that with my CNC shop you pay about $2/lb for steel and for aluminum its $5-7/lb, granted it is lighter. To build a cage or stuctural component from aluminum tubing yu would have to get aerospace grade X-rayed tubing to ensure there are no inclusions $$$$. If you want a nice light weight cage you could use .093" 4130 tubing and tig weld it; but then again you won't be saving any $.

JP
 

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I thought mechanical tubing was the same as DOM. Apparently, it's not, but I don't know the differences.

Machine shop tells me Mech Tubing is almost as strong but doesn't cost nearly as much as DOM.

Anyone know differences between mech. tubing and DOM?
 

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My understanding is that DOM and HREW are the same material (namely steel). DOM is HREW that has been drawn over a mandrel - if you look closely you can still see the seam. Drawing the tube over the mandrel will give it more precise dimensions and a better finish, but I don't think it will provide much additional strength. Maybe a little, from work hardening or the like, but not much.

That's how I understand it, anyway. Personally, I'd go HREW.

Chris
 

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there is a reason why no one uses Aluminum for roll cages. It dents really easy. They use it on mtn bike frames but if you watch it is alot bigger in dia. then an equivalent chromo frame.

Also bending the al tubing would be impossible without stress cracks.

Why not use HREW? DOM is just overkill for anything but a circle track, drag racer or desert truck. Slow speed roll overs will be fine with HREW. I would pay more attention to the design of the cage then the material used.

If you are talking about suspension components... Aluminum would probably work for some stuff like control arms etc. but you would have to make it out of plate and weld it into sections.

Aluminum is for airplanes!:*******
 

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Discussion Starter · #9 ·
The reason I'm asking is not for a rollcage, I want to build a tubular rail bed for my truck. I want to find a relativly strong AL or AL/Alloy that I can weld AL plate too. I would like the design to include lockable storage and maybe extra fuel storage also. And `cuz steel to aluminum welding is way beyond anything that can be done in our shops I'm sniffing around an all AL idea. I know that it could be done by just mounting the AL stroage and tank to a DOM or HREW tube bed via tabs but I want a one peice unit.
 

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Well for a bed then ya AL will work fine :rolleyes:

I would suggest against making it all one though. At some point you will want to remove the extra fuel tank and taking the complete bed off with it would be a complete PITA.
 

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does the weight savings really make up for the cost differance? for that application i think i would just use the HREW
 

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Discussion Starter · #12 ·
cambo said:
does the weight savings really make up for the cost differance? for that application i think i would just use the HREW
Well with the rough figures I've got so far and using this dandy little tool I'd guess about 30% to 40% over steel. But it's not just weight that I'm concidering here either I want a solid one peice rail bed. I'm just wondering if the first time I go flop if its gonna look like a pretzel.
 

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If aluminum is so weak, than why does Lang Fab and other trailer manufacturers for highway trucks use it for trailers carrying 50,000 lbs worth of lumber @ 120 km/h. I do not see the reasoning...I agree with the fact if you bent a heat treated AL tube it would crack, but what about non-heat treated tubing, it can be H/T after bending. I also believe that 70% of the air frames in boeing and similar Jets are made from AL. It was just a thought...

I would go with AL for a flat deck, but it will be twice the price and 2/3's the weight of a similar steel deck! You can always bolt steel and aluminum components together if you wanted to as well.
 

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Let me see if I can help here. I am a purchasing agent for a
highway trailer manufacturer in Abbotsford. I purchase steel & aluminum every day (tons).
There is hugh difference between pipe & tube.
Roll bars should always be fabricated using mechanical tubing,
NOT PIPE!!!

ERW comes in pipe & tubing, the difference is in the material grades & compositions, thus affecting the mechanical properties.
(Yield & Tensile strengths)

A general rule to remember is pipe should never be used in
any structural applications.

We manufacture trailers with aluminum outer rail cap (6061-T6)
or T-1 steel (100 ksi yeild)
In order for us to acheive the same strength in the alum. as the steel, the alum.section is so large that the steel cap trailer
weighs less.
(aluminum is for making a trailer look pretty,any structural application requires much more material,thus eliminating any weight savings.)

Round mechanical tubing is available in few different types

1) Cold drawn seamless
2) Hot finished seamless
3) D.O.M.
4) ERW
 

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I have numerous Super "b" trailers pulling out of terminal and mainland sawmills in Vancouver that are made entirely from Aluminum...umm huh...aluminum. This allowed them to carry an extra package of lumber without exceeding the GVW for their trucks.

There is nothing weak about Sch. 40 or 80 Pipe!

IMHO:soso
 

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ERW is simply a method of manufacturing and can be used to produce pipe or tubing.
so... yes, sch 40 pipe can be manufactured using electric resistance welding.
(the schedule of a pipe is generally used to describe wall thickness or id)
 
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