Bumper thoughts and questions

[StealthTJ]

Ok, I've (my brain anyway ), has been thinking (don't shoot the brains messenger ) some lately. Always looking at ways to keep the Jeeps weight down and/or get the weight lower, I weighed the Jeep again this last weekend, on a split platform truckers scale. Same on that I've always used. Anyway, after the addition more steel (skids), I'm (well, the Jeep) now 100 lbs heavy in the rear.
So, about bumpers. Just started, this morning, thinking, what about copying the bumpers that I have now (I'm happy with the design), but using some like 6061 T6 aluminum instead of the 3/16" steel ...
Any thoughts, opinions, etc.
What thinkness ?? 3/8" or less or ......




Fred

[Timzjatl]

You'd have a hard time saving enough weight with aluminum to make it worth while. As you've already pointed out, you'd have to increase the thickness in order to retain strength, or significantly change the design.
for starters, from www.matweb.com
6061-T6 aluminum = .0975lb/in^3
1018 Steel = .284 lb/in^3
so the aluminum has roughly 1/3 the density. If you were to double the thickness (which might not be entirely neccesary) you could save 1/3 of the weight of the bumper itself. Are your bumpers that heavy?

Also keep in mind that Aluminum is more trouble to weld, and costs significantly more than steel. the local scrap yard gets $.25 a pound for steel, and $3 a pound for aluminum if I remember correctly.

I'll be interested to see how it works out for you if you decide to go that route.
Good Luck
Tim

[BlueJeeper]

IMO I think 3/8" 6061 is way overkill for a bumper. If it was a belly plate and you had to worry about deflection on a big long piece of it, then maybe, but with a well designed bumper I wouldn't use anything thicker than 1/4" 6061 plate. I have also been thinking about some AL bumpers as well but haven't settled on what I want. I don't weld, but have not found welding 6061 at the shops in my area to be cost prohibitive. I would also be interested in seeing what you come up with.

[StealthTJ]

Yup, I was thinking that 3/8" would be way overkill, 3/16", maybe 1/4"... It's not like it's a belly up or something.

Tim, I know that the aluminum is a fair amount more than steel, but it is lighter. A pound here and a pound there, they all add up


I would be doing the welding myself.




Fred

[Timzjatl]

awesome fred... if you have the skills and access to the materials its a different ballgame. I have always thought I should learn to TIG aluminum, but never took the time... steel with MIG is just so convenient...
I wouldn't go over 1/4" wall on a bumper, possibly even 3/16" if the spans are short and its some sort of tube....

[StealthTJ]

Auminum with MIG also
Spool gun and 100% argon ...




Fred

[mrblaine]

The problems so far encountered in the design of aluminum bumpers are pretty bizarre.

The best would be 6061-0 which is the heat treatable version of 6061-T6.

That allows form and bending without breaking it. Then you weld it up and ship it off to the heat treater.

I've been playing around with some 5052 for ease and simplicity of fabrication, but have encountered some interesting aspects that complicate things.

I want a hoop. That means moving the tow hooks. That means a big block under as reinforcement. It's hard to weld a big block to thinner AL. The different cooling and contraction rates crack the welds. Toss the block and use a flat plate and drive the cost higher. It can be done, just takes some patience that I am low on at the moment.

[TJRON]

I tried to make a lite bumper with strong tow points. I wasn't interested in a tire carrier. My bumper is 1/8" with three strong shackle mounts. It weighs 37#. It has been scraped and hit on the ends plenty of times and doesn't have a dent iin it. Yet......

You might get some ideas from mine:
http://www.fototime.com/inv/A3A24CFE02717BE

[Timzjatl]

Ahh, fred very cool. Our spool gun at work has been busted for a while, so we do what little welding on aluminum we have on the TIG. Tig welds on aluminum by a skilled hand look sooo good. Thats why I'm not the one doing those...

[BlueJeeper]

Originally posted by mrblaine
The problems so far encountered in the design of aluminum bumpers are pretty bizarre.

The best would be 6061-0 which is the heat treatable version of 6061-T6.

That allows form and bending without breaking it. Then you weld it up and ship it off to the heat treater.

I've been playing around with some 5052 for ease and simplicity of fabrication, but have encountered some interesting aspects that complicate things.

I want a hoop. That means moving the tow hooks. That means a big block under as reinforcement. It's hard to weld a big block to thinner AL. The different cooling and contraction rates crack the welds. Toss the block and use a flat plate and drive the cost higher. It can be done, just takes some patience that I am low on at the moment.

I have been wondering about this. It is interesting to hear someone's experiences with forming and welding 5052 vs. 6061. Are you going to be heat treating the 5052 in any way after welding? Also, if you don't mind me asking, how has your gas tank skid held up? That is 5052 as well, correct?