Aluminum and Mild Steel

[geezer]

This probably is not the right spot, but I am looking for a source of strength comparison between aluminum and mild steel? Specifically channel, purpose is to build a small trailer for my Ranger 8, thanks

[aevald]

Hello Geezer, I don't have any specifics for strength comparisons between aluminum and steel however, consider that the weight savings from using aluminum over steel is often not enough to justify the use/cost of it over steel. Unless you already have a source for the aluminum and it is much less than typical retail, steel will be much more economical.

Also consider the difference in construction, if this is going to be a welded trailer you will have a lot more in wire cost/shielding gas cost, etc. It can also be argued that the weight/sizes of the steel construction members vs. aluminum might be negated due to the steel being stronger and thus being able to size the trailer components from smaller or thinner members as compared to the comparable aluminum pieces to achieve similar strengths.

Aluminum is more difficult to repair after you have constructed something out of it and it possibly requires repair(you're out on the road and something breaks and you have to find someone with the proper equipment to make the repair). Even if you use an aluminum alloy that has considerable strength, most of these alloys are heat treated and this is where their strength comes from. When you fabricate and weld something from them and don't have the ability to heat treat them back to their original condition you can end up with welded joints that will fail simply due to the reduction in strength from welding.

Just a few things to consider when you are choosing a design and the materials to go with. Good luck and best regards, Allan

[FernTJ]

Aluminum has about 1/3 the Modulus of Elasticity that steel has (10 million psi vs 29 million psi). So for a given beam loading aluminum has about 3 times more deflection than the same cross section of steel beam.

Aluminum a higher yield stress than steel (43000 psi vs 36000 psi) so it can take more stress before yielding (permanent deformation).

Aluminum and steel have very similar ultimate tensile strengths (55000 psi vs 58000 psi) so in tension or sheer there isn't very much strength advantage in steel.

Aluminum is about 1/3 the weight of steel at .101 pounds per cubic inch vs .284 pounds for steel.

It is worth noting that aluminum is more prone to suffering from the heat affects of welding, which may lead to joint failures and it costs more per pound. If you aren't going to pull the trailer a very long distance you may be better off staying with steel.

[geezer]

Thanks Allan, practical common sense advice. I am just a semi retired guy working out of his garage with an itch to build a small aluminum trailer for my ranger 8. Actually describing it as a trailer is a huge compliment. It only needs to be big enough to house my 500lb machine with no intentions for the highway. Part of it is I enjoy working with aluminum and have fabricated several add ons to jon boats but nothing structural. Thanks for the input, well received.

[geezer]

FernTJ, many thanks. That is useful info I was looking for an will defintely archive. I have experienced the affects of heat to aluminum welds. I was working on a pontoon boat welding an enclosure that someone nearly destroyed with a spool gun. I noticed the material annealed and after doing some research found out home come. I have neither the knowledge or equipment to heat treat so I am careful on aluminum weld joints and choose my projects and approach carefully. Thanks again, great info.

[abec]

As a rule of thumb I usually increase the thickness by 25% compared to steel

[MinnesotaDave]

Aluminum has about 1/3 the Modulus of Elasticity that steel has (10 million psi vs 29 million psi). So for a given beam loading aluminum has about 3 times more deflection than the same cross section of steel beam.

Aluminum a higher yield stress than steel (43000 psi vs 36000 psi) so it can take more stress before yielding (permanent deformation).

Aluminum and steel have very similar ultimate tensile strengths (55000 psi vs 58000 psi) so in tension or sheer there isn't very much strength advantage in steel.

Aluminum is about 1/3 the weight of steel at .101 pounds per cubic inch vs .284 pounds for steel.

It is worth noting that aluminum is more prone to suffering from the heat affects of welding, which may lead to joint failures and it costs more per pound. If you aren't going to pull the trailer a very long distance you may be better off staying with steel.

I found this interesting - I will have to push some extraneous info out of my brain and add this to my limited storage area

[Broccoli1]

Take a look at Aloominum cargo carriers that mount in a receiver. You'll be fine making running gear for the Ranger 8.

[geezer]

Thanks Ed, I just googled a couple, 500lb rating. Sure will provide a good pattern to take off from. Thanks

[Willie B]

I found this interesting - I will have to push some extraneous info out of my brain and add this to my limited storage area

I always make a mental note, then commonly lose the scrap of paper it is written on.

[Willie B]

Aluminum has about 1/3 the Modulus of Elasticity that steel has (10 million psi vs 29 million psi). So for a given beam loading aluminum has about 3 times more deflection than the same cross section of steel beam.

Aluminum a higher yield stress than steel (43000 psi vs 36000 psi) so it can take more stress before yielding (permanent deformation).

Aluminum and steel have very similar ultimate tensile strengths (55000 psi vs 58000 psi) so in tension or sheer there isn't very much strength advantage in steel.

Aluminum is about 1/3 the weight of steel at .101 pounds per cubic inch vs .284 pounds for steel.

It is worth noting that aluminum is more prone to suffering from the heat affects of welding, which may lead to joint failures and it costs more per pound. If you aren't going to pull the trailer a very long distance you may be better off staying with steel.

I'm relatively new to building things from aluminum. I've long been intrigued with aluminum. My father was an aircraft mechanic in WWII and the Korean Conflict. His stories of aircraft and the way you repaired bomber damage facinated me. By 1966 he got an income tax refund and let me decide how to spend it. The Grumman 15' Standard Weight canoe looks and functions as well now as then.

When I build something of steel, prep and paint are drudgery. Rust seems to begin about ten minutes later. In a few years it may still be functional, but doesn't look very good. Even if it's just a garbage can built from aluminum I know it will be used by generations. Someday my great grandson is going to say that I built it. Aluminum is not as strong, but is more durable.