Aluminum M416 - Pros / Cons....

[ErikinSC]

So I got an Autocad app for the iPad and drew up my modified M416... Scaling the body to 48" between the wall, and 7' long... I could shorten the box to 6'6" a just figured I'd take the extra space INSIDE the box rather than all on the tongue.

My thought was to build an aluminum box and frame, to save additional weight - but was told to go with a steel frame, and aluminum box... Then talk came up about the aluminum not being sturdy enough.

I haven't found anyone else that has built an aluminum 416 either... So maybe there is a reason.

Pros vs Cons on building a custom M416 out of aluminum?

 

[Awl_TEQ]

Mine is aluminum

Build thread:

I have 24 days to build this trailer

 

[ntsqd]

Two biggest things about aluminum are fabrication technique and expense. Welded or riveted?

If you build a steel frame and you live in a wet environment you'll want to electrically isolate the two metals from each other or water in the small gaps will form a battery of sorts and start the corrosive process. I suspect that simply powder-coating one or both would be enough insulation. Some paints will also be enough (POR-15 etc.), but I wouldn't expect that of any rattle cans.

First thought on seeing the images is that the springs are too short for a decent riding trailer.

 

[ErikinSC]

Thanks for the comments.

I also reviewed Kevin's excellent 24 day build... and have been taking notes.

Actually, my spring length is right at 36" long @ntsqd - but the arch is probably misrepresented. Good observation, I will recalculate. The Dexter 3500# axles come 26" standard length, and I DO NOT want the short stiff axle. I even thought about using the stock FJ40 springs that I replaced on my rig, if I can find them in the shop.

Aluminum tub will be linexed in/out - and plan to mount on a rubber strip. will definitely ensure they are insulated to prevent electrolysis. I live in the low country and our humidity is 90% and up much of the year.

 

[Awl_TEQ]

Nothing wrong with an aluminum frame. General rule of thumb is to go 50% thicker than the equivalent steel structure calls for. Must be welded properly too. Aluminum is less forgiving of a poor penetration weld than steel.

 

[ntsqd]

Can save weight with aluminum in the design if you can do simple beam analysis (quasi-automate the calcs in Excel). Vary the tube dims and the wall thickness' to yield a tube selection that will carry the same load as a steel tube design choice, but weigh less. Adding wall thickness helps, adding geometry, mostly in the vertical since that is the dominate load direction, can result in less weight and a stronger design. I'll warn you though, when I went thru that process for the bike trailer below and building it out of aluminum would have cost 3 times as much.

 

[ErikinSC]

I am strongly leaning to a Stell box frame, maybe 2x4 thinner wall, 2x2 draw bars, 36" length springs, and staying with an aluminum tub. If I have small dimension 1/2 x 1/2 square tubing cut and welded to the sides - instead of theoriginal pressed / bead rolled strengthening points, I think I can get it there and get the vertical rigidity. For the flex (oil canning) along the length, I am reconsidering folding the top lip, and adding a 1x1 square tube, or a combo square w/ 1/2 round to improve the finished look.

I need to keep my trailer weight low because the tailgate grill* that I will carry, along with coolers, RTT etc, will add up. Yes, the grill weighs a lot.

 

[Fast Eddy]

According to the calculator here: Online Metal Store | OnlineMetals.com and using the 50% thicker rule, using Alu will save almost 50% of the tub weight. Hmm...

Do you really need a 3500 lb axle? If I was building one, I'd be shooting for 1000 lbs total or so.

Lightest RTT? - 100 lbs

20 gal water = 160lbs

2x 35" tires and rims = about 250lbs

From searching around, it seems a stock m416 is about 575 lbs with the tub about 200 lbs, so you could probably make one with an alu tub, lid and 35s that was about the same, then have 500 lbs of gear and cargo and still be under 1100 lbs.

 

[ntsqd]

The reason for a 3500 lbs. axle isn't the weight carrying capacity, it is for the wheel bearing size. The smaller bearings in lighter axles don't seem to last very long off pavement. Can also run into needing wheel adapter vs. being able to buy hubs with the right bolt pattern that fits the heavier axles.

Could take a page out of the M416's book and make the axle from scratch. Would need access to a lathe, but could make flanges that index and bolt on FJ or Mini stub spindles, and use the related wheel hubs & relatively huge bearings. Weld the flanges to a tube of your choice.....

 

[Awl_TEQ]

The reason for a 3500 lbs. axle isn't the weight carrying capacity, it is for the wheel bearing size. The smaller bearings in lighter axles don't seem to last very long off pavement. Can also run into needing wheel adapter vs. being able to buy hubs with the right bolt pattern that fits the heavier axles.

Yes, exactly. I only used a 3500# axle for the hub bolt pattern. Truck and trailer use the same wheel/tire combo. You can always take out a leaf if you find it too stiff.

Everybody likes pictures: This was a fun crossing of the Cardinal River