has anyone went with a aluminum trailer frame?

[shawnkfl]

i work at a boat trailer manufacturer and get materials at cost. since we buy mass quantities, i can get aluminum cheap. i was thinking about using 3" I-beam for the sides and 2" tube for the cross members. this should give me a really light frame. i costed out a 5' X 10' frame today and my cost is only $288.00 with 13" alum. mag wheels and a torsion axle. i can have it bolt together or fully welded. has anyone went that route? i think i'm going to do it as the steel version is only $50.00 cheaper for me.

[Alphacarina]

With the Torsion axle, I would weld the whole thing up with 2 inch tube - Should be lighter than using the 3 inch I beam

There's no advantage to aluminum over steel unless you're maing it significantly lighter than with steel . . . . and if you oversize things, the aluminum frame could actually be heavier

Don

[halfdome, Danny]

Trudy/Rod of this forum have an aluminum frame/chassis for their tear. Danny

[dreadcptflint]

Go for it Shawn. The WAZAT has an aluminum frame/chasis.

[emiller]

Just remember to check it often as aluminum doesn't bend like mild steel does so they tend to crack. But if you use a solid sub frame you should be OK.

[Trackstriper]

You should be fine with the aluminum frame. For the average bear this might be a problem trying to get the design right with cracking and other fatigue issues. You should be able to get specific design help from the folks you work with. If they build aluminum boat trailer frames they have the knowledge to keep you out of trouble. Without that knowledge base, though, someone could run into problems. Aluminum will look nice, won't rust and you won't have to paint it. Seems to work well for aircraft when the design is correct. Go for it, but get in-house advice.

[shawnkfl]

well, it comes in handy being the mechanical engineer here. i've designed my frame to be a bolt together frame and have a 2000 lbs capacity. of course, that's using a safety margin and it's still more than i'll need. but man, this frame is light! i'll post up a build thread soon on it with all of the specs. the only drawback with welding it are stress factors. if a weld fails, i'm stuck. with bolting, i can check and replace them as needed. i'm going with grade 5 stainless on all fasterners, so corosion is moot. all through bolts will have nylock nuts on them. bottom line is, i can have a rolling alum. frame for less than $300.00 with equal or better capacity than steel, without the rust and weight issues.

[emiller]

Again don't mix aircraft with vehicles. Airplane frames are rivited together so it can move, and being out of alum. that's why the constant inspections. As for boat trailers I don't know. I do know my tung on my trailer bends abit because it's not weighted like a standard trailer, my wheels are farther back so I have alot of tung weight. Another thing about alumiunm is it does carode and we always have aircraft in our shop having sections replaced.

[angib]

Mixing stainless fasteners with aluminium does give a corrosion problem is the trailer is exposed to corrosive environments, particularly salt-laden ones. The annoying thing is that aluminium will be anodic to the stainless, so it will be the aluminium that will corrode adjacent to the stainless fasteners, if galvanic corrosion occurs - unlikely in New Mexico, very likely should you drive onto an ocean beach. It's a shame it's not the other way around as replacing the bolts would be easy, but replacing the aluminium they're bolted to isn't.

This can be avoided by suitable anti-corrosive jointing compound. Here in the UK boatbuilders use 'Duralac' (yellow chromate). I know it's hard to get Duralac in the USA, but you will get something similar from an aircraft supply company - though of course at aircraft supply prices! However a small tube is all you need and it really works. You paint it on any bolt surfaces/thread that will come into contact with the aluminium and it stops corrosion dead.

Andrew

[shawnkfl]

we have aluminum boat trailers in the field with stainless fasteners that are still fine after 12 years. sure, there is some corrosion, but not nearly as much as our steel galvanized versions. our aluminum series trailers are for salt water use, so they are intended to be used in salt water and salt air environments. i have no doubt that an aluminum frame, with very minimum maintenence will last me far longer than i'll have the tear. i could coat the fasteners with zinc chromate for better protection, but from what we've seen come out of the field, the corrosion is not as bad as it may seem. some of our aluminum trailers are built for professional fisherman who use them 359 days every year, so they are in and out of salt water almost daily. they still look great. the aluminum gets a haze on it and then stops. sort of like the green on copper. it actually protects it.

[emiller]

Here are some articles on this,
http://www.equispirit.com/info/aluminum ... lers-2.htm
http://www.equispirit.com/info/aluminum ... lers-2.htm

[shawnkfl]

those are good articles. considering the writing is from a steel trailer manufacturer....

[Trackstriper]

shawnkfl wrote: "well, it comes in handy being the mechanical engineer here." My bad. I hadn't read your newbie introduction.

I'm sure you would have a good deal of practical information to share with us when working with an aluminum frame. Welcome aboard, there's a lot of really valuable information on this site.

I did toy with doing the aluminum - bolt together - but decided to go with 14ga 2x3 steel tubing as it's more conventional, I can weld it, and I'll be less concerned about fatigue down the road. If I can just avoid the rust issue....


J.B.

[shawnkfl]

i was going to design mine with steel and have it galvanized, then paint it black. i started thinking about weight and my truck (2.2 4 cyl sonoma) and looked ay my cost for aluminum. it wasn't that much of a difference for me. it will cost me about $70.00 more to build with alum, but will save me ~115 lbs. that's not much, but it helps. my tear design is a cross between a cubby and a grumman and as light as i can make it. the cabinets will be 1/8" ply with a corugated (sp) carboard core, kind of like a hollow core door, for weight savings. the sides will be 1/4" ply with the cardboard core as well. she should be light when i'm done.

[brian_bp]

Here are some articles on this,
http://www.equispirit.com/info/aluminum ... lers-2.htm
http://www.equispirit.com/info/aluminum ... lers-2.htm

As mentioned earlier, this is coming from a manufacturer of steel trailers. Perhaps this is why this glaring error appears:

Pound for pound, aluminum is only 1/3 the strength of steel.

No, for the same cross-sectional area a typical structural aluminum alloy is significantly weaker than common steels (about 1/3 the stiffness and yield strength), but the stuff is also only about 1/3 of the density of steel, so "pound for pound" they're quite comparable.

Since aluminum is more expensive than steel, the justification for using aluminum is typically either the difference in corrosion characteristics (they both corrode), or that the structural advantages of a lower-density material. For instance, if you make a floor of plate material in either steel or aluminum of the same weight, the aluminum would be three times as thick; since the strength of a plate being bent increases by much more than a factor of three when you make it three times as thick, the aluminum floor can be lighter - it doesn't need to be three times as thick for the same strength.

I find it hard to see much advantage to aluminum in the beam shapes used in trailer frames, unless a deeper beam section can be used; in that case, it can save weight... because the statement quoted above is completely incorrect.

Where aluminum is not often "beefed up" is in interior dividers. Since aluminum is weaker by about 1/3 from that of an "equal in size" steel divider, it will fail quicker

This is a perfectly valid statement by this trailer manufacturer. Anyone who substitutes steel with aluminum of the same dimension in an otherwise unchanged design is completely clueless about the materials they are using. In contrast, shawnkfl is specifying a larger (and perhaps thicker) section for his aluminum beams than would be used in steel.

I look forward to hearing the promised details of the design, such as the beam dimensions (not just the overall height!) and fastening details.