Plan for Axle Location

[GeneH]

I have reached the point of drilling the siderails for mounting the supports for the half axles on my frame. Before I drill the holes however I would appreciate a reality check on my approach.

The tear will be an 11 ft. long, 5 ft. wide, 4-1/2 ft. tall (sandwich wall) modernistic. My current avatar is a photo of the full size wall pattern.
The frame is 105” long by 62.5” wide (outer dimensions) bolt together like the one Jerome built and posted photos of last year. The back cross member of the frame will be 13” from the back of the tear. I am using 2” x 2” angle 3/16” thick. The frame weight including 14” wheels and 205R70 tires is about 330 lbs.

I calculated the total weight of the tear at about 1450 lbs including about 300 lbs of gear, clothing, water food, battery, etc.

I am planning to place the wheel axles 52” from the back of the tear which is 39” from the back of the frame. The torsion half-axles will be centered 56” from the back of the tear with a 20 degree down to the wheel axles.

The 2” x 3” rectangular tube tongue will start at the axle support angles and is a total of 144” long. It will extend 6’ beyond the front of the frame with 2” x 2” angle supports attached 2’ from the frame.

The tongue weight on the tow vehicle calculates out at about 165 lbs (about 11% of the tear’s weight) on the tow vehicle, a Ford Explorer.
My 220 lbs weight causes the back bumper it drop about 1” when I stand on it so I don’t think the 165 lbs will be a problem.

So before I drill the frame to mount the axles does anyone see anything I have overlooked?

Thanks for your thoughts. Gene

[mikeschn]

I think you've got the bases covered... And 52" to 53" is exactly where I would start with the wheel centers (from the rear).

Mike...

[angib]

My first shot using your numbers gave a 180lb hitch weight (12.4%), assuming the trailer weight is evenly distributed along the body.

Then I took away 150lb from the 1450lb total and stuck that 150lb in the galley. That made the tongue weight go down to 120lb (8.8%). I think quite a few of the things you're describing would end up in the galley, so you need to take that into effect.

I then moved the wheels back 4" and the tongue weight went up to 150lb (10.4%). I think that's where I'd put them - with an Explorer, going slightly high on the tongue weight won't harm, but going low could give you a squirrelly trailer.

Andrew

[GeneH]

Thanks for the replies guys.

Since I had set up a spreadsheet to do a sectional analysis (2 inch per section) of the length of the tear I thought I had nailed it down. After reading your comments Andrew I went back to the spreadsheet and found a couple of errors that skewed the results.

After correcting these formulas the spreadsheet essentially duplicated your recommendations so I will be placing my wheels at 48” from the back of the tear which should give me a tongue weight of about 165 lbs.
I appreciate your help in keeping me from carrying the errors into my frame.

[eamarquardt]

My axle will be adjustable (though once I bolt it in place I don't think I'll probably ever move it). See pictures in album.

How bout just clamping the axle in place or something to allow you to move the tear around while building it and then once you are finished and loaded for bear you can determine exactly where it should be mounted.

Hope this helps.

Cheers,

Gus

[prohandyman]

I am building on level jack stands. And even though it appears to be attached, my axle is only tacked on lightly in the general location. My plan is to get it as close to finished as I can, load it as if it is road ready, and then weigh the tongue. Then I can weld the axle permanently. Just my way of planning!