Ultralight Design?

[mikeschn]

Andrew,

Check your email for a wrl file...

Mike...

[Miriam C.]

Roly. !!!!!!!!!!!!!!!!!!!!!
I see where you guys are going with the trailer and my first question is "Where are the springs?" Do you still need them?

Second (oops third) If you use hollow core for the floor how do you seal the open structure if you cut.

I bought core doors for $6 for the walls and open ends for the cut aren't an issue. (these are 30" and 36")/

Just a thought
Miriam

[Mitheral]

Notice the pink colored square tubing that slips onto the side pieces of spruce! That gives you something solid to drill your holes into and bolt your axle to. The top and bottom skins of the torsion box can be notched out to clear the tubing.

I'd avoid this configuration, you are just asking for the spruce to rot out and the steel to rust away. Better would be bolting the tubing to the side or under the spruce pieces to reduce the direct steel to wood contact surface. This also allows you to inspect for rot and more importantly repair it when it happens. Might also be a good idea to use pressure treated material to delay the inevitable.

An A-frame under the torsion box frame connecting the hitch to the axles might be better. Use angle rather than square tubing to reduce mass and the torsion box floor can be bolted to the A-Frame all along it. An additional piece under the front edge of the floor (sort of like the horisontal bar in the A) would allow you to pick up the heavy load of the front wall in a distributed way. A person wouldn't have to go overboard on the angle, even some 1 1/5 sould be sufficient.

The A frame method is also much more convential, something that could make it easier to pass an inspection or protect yourself if you are ever involved in a accident.

[Mitheral]

Roly. !!!!!!!!!!!!!!!!!!!!!
I see where you guys are going with the trailer and my first question is "Where are the springs?" Do you still need them?

A trailer this light I'd go with the rubber torsion suspension.

[Guy]

Dear Andrew, \\

Following up an earlier point you made on that wooden frame thread and carrying it forward to this, as you ready the wooden tongue.
On the all wood frame thread you properly noted the need for the angular members going back up to the tear.

As the discussion here transforms from torsion floor to monoque then to a partial monoque I would like to suggest the following.

When you consider your tongue take a look at the possibility of including a tongue box as part of the structure.




The curved pieces would be the cutoff from creating the side profile, would hang from the monoque sides and top, and provide the lift and support of the tongue, and using the same material as the whole for weather integrity.


Also, remember, this is a design for Mike and not those of us privileged to drive without major potholes in California and England. I do not know the last time you drove here but by spring, in Michigan and thirty other states, we have potholes the size of UK caverns on many of our roads. Therefore the twisting moments will be greater than normal.


As an additional thought, could you please give us a lesson on the real and imagined difference between half torsion axles and full ones. You often write that in Europe half torsion are the norm but we on this side seem to have the same aversion to them as we do for all wood construction rather than steel.


Whilst I am at it, I wish to add that besides shifting the paradigm from House building we might also consider changing the notion that woody details are merely decoration appliedto the exterior. They should be thought of as more integral to the structural design, sort of , the framing on the outside. For ultralights the interior can be insulated with flexible foil foam or bubble and covered in upolstery, such as in padded fabric French walls.

The woody stucture is the perfect one to suspend everything from and attach to.

[mikeschn]

Well, I haven't heard from our resident engineer yet... hmmmm... he might have decided to take a ride on his bike along the entire length of Hadrians Wall, to work out the details of his plan...

But Mitheral, I took your points under consideration, and removed the steel tube around the spruce. I guess, sometimes, if things look too good to be true, they are.

I'm going to take another look at using angle underneath like you suggested. That may not be till tomorrow morning though.

In the meantime, I've just cleaned up what I have so far, and I'll bet it's do-able... We just have to look for the weak points...

So here's where we are at...


I think tomorrow I work on a couple options for the sides... and present the ideas here for you guys to chew on...

Mike...

P.S. Guy... a wooden tongue scares me. Can we consider steel pipe instead?

[Mitheral]

But Mitheral, I took your points under consideration, and removed the steel tube around the spruce. I guess, sometimes, if things look too good to be true, they are.

I'm going to take another look at using angle underneath like you suggested. That may not be till tomorrow morning though.

Looking good already.

[Jiminsav]

Guy, i'll jump in there for Andrew..this is a torsion half shaft
this is a whole torsion axle
hope this helps.

[mikeschn]

Hey, whatdayaknow... I got the first wall up...





Mike...

[Jiminsav]

those bronze tires look good, but they don't have any tread left..

[Guy]

Dear Mike,

Does a full torsion axle have a camber? When Dean checked his for me, he said his does. If so, then your drawing suggests that you will be connecting the end of your tongue to a piece of metal that will be constantly bending.

If it has a camber, which naturally bends, and you have a steel tube connecting it to a dissimilar material, ie plywood, you are going to be placing a tremendous amount of pressure on the bolts and their connection to the plywood. Eventually one side will have to yield to those forces.

[mikeschn]

those bronze tires look good, but they don't have any tread left..

Sounds like the bronzed baby shoes to me...

Mike...

[mikeschn]

Dear Mike,

Does a full torsion axle have a camber? When Dean checked his for me, he said his does. If so, then your drawing suggests that you will be connecting the end of your tongue to a piece of metal that will be constantly bending.

If it has a camber, which naturally bends, and you have a steel tube connecting it to a dissimilar material, ie plywood, you are going to be placing a tremendous amount of pressure on the bolts and their connection to the plywood. Eventually one side will have to yield to those forces.

That's definitely something to consider. If that rear axle cross beam flexes, then I can't attach to it, or it'll rip the tongue member out of the floor... ouch...

Mike...

[JunkMan]

I didn't think the axel flexed, it was just arched to give the tires some camber so they would track properly.

[angib]

I didn't think the axel flexed, it was just arched to give the tires some camber so they would track properly.

Seconded. The camber in a torsion axle tube will make no difference to whether it flexes - a straight one would flex the same.

I'm not making promises about amounts less than 0.001" - any difference between straight and cambered might amount to that, but I call that 'the same'!

What I'm waiting to see is how Mike is going to connect the tongue to the axle - I think this is exactly the place where the 'no welding' rule actually does apply.

Andrew