Drop Floor Canned Trailer Design - Any Suggestions?

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Drop Floor Canned Trailer Design - Any Suggestions?

Postby supra8311 » Sat Aug 22, 2015 10:23 pm

Hi,

I'm looking for feedback on this trailer design. This is my preliminary concept. The trailer is 13' long and 6.5' wide. The camper is just under 8' tall.

Since the trailer needs to be light weight and have the proper tongue weight, it needs to be a custom design. I would like to have it professionally made.

I am having trouble with the trailer design. The model below has 2x3x1/16" tube steel with 2x3x1/8 for the tongue. I think this design saves some welds by using solid bars for the cross sections and gets 3"of drop.

- Can the tongue on top of the drop section of the frame?
- Is it safe?

Thanks,
Andre

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Re: Drop Floor Canned Trailer Design - Any Suggestions?

Postby angib » Sun Aug 23, 2015 4:55 am

There's nothing wrong with having the A-frame above the main frame - welds work up and down!

But what is bad about that design is the angle/bend (I'm assuming it is a welded joint) right at the front cross member, the point of highest load. Making the A-frame discontinuous at this point (the easiest way to fabricate this) and having a welded joint right through it is bad practice. Welders will say that the welded joint is as strong as the parent tube, which can be true in static one-off load, but the welded joint is still a source of fatigue cracks that reduces the A-frame's long term strength a lot.

I can think of no easy answers to how to get a bend at that point without having a welded joint. Except maybe continuing the A-frame tubes out to the outer main rails - fillet welding continuous A-frame tubes is acceptable if not actually ideal.
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Re: Drop Floor Canned Trailer Design - Any Suggestions?

Postby ctstaas » Sun Aug 23, 2015 11:04 am

Hi Andre, On page four of this thread I started a discussion on drop floors with lots of great feedback. With that feedback I drew plans for my next 5x 5x 10 with a drop floor. I hope this will spur an idea.
Enjoy. Chris
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Re: Drop Floor Canned Trailer Design - Any Suggestions?

Postby supra8311 » Sun Aug 23, 2015 11:47 am

Thanks angib - that's exactly what I needed! I will updat the cad model and repost soon.
Andre
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Re: Drop Floor Canned Trailer Design - Any Suggestions?

Postby supra8311 » Sun Aug 23, 2015 11:49 am

Chris - I would really like to see your design. Can you post a link?
Andre
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Re: Drop Floor Canned Trailer Design - Any Suggestions?

Postby supra8311 » Sun Aug 23, 2015 12:04 pm

I would like to use these torsion axles with electric brakes(link below). Anybody have any experience with them?

http://www.southwestwheel.com/store/p-2 ... rakes.aspx

Can the trailer wheels be aligned at a place that does cars?

Also, if I put a 3500# axle in and the trailer weighs 2000# when loaded, will the corners of the tires wear on the corners because of the 1.5 degree down angle (link to outline drawing below)?
http://www.trailerpart.com/halftorsionaxles.htm

Thanks,
Andre
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Re: Drop Floor Canned Trailer Design - Any Suggestions?

Postby supra8311 » Sun Aug 23, 2015 9:46 pm

angib wrote:There's nothing wrong with having the A-frame above the main frame - welds work up and down!

But what is bad about that design is the angle/bend (I'm assuming it is a welded joint) right at the front cross member, the point of highest load. Making the A-frame discontinuous at this point (the easiest way to fabricate this) and having a welded joint right through it is bad practice. Welders will say that the welded joint is as strong as the parent tube, which can be true in static one-off load, but the welded joint is still a source of fatigue cracks that reduces the A-frame's long term strength a lot.

I can think of no easy answers to how to get a bend at that point without having a welded joint. Except maybe continuing the A-frame tubes out to the outer main rails - fillet welding continuous A-frame tubes is acceptable if not actually ideal.




Like this angib?
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Re: Drop Floor Canned Trailer Design - Any Suggestions?

Postby angib » Mon Aug 24, 2015 4:13 pm

That A-frame is now a safe design, though I'm not a fan of the three tongue pieces - the middle one won't actually be doing much, as it's attached via a (springy) cross-member.

If you can't get a 50 degree A-frame angle (to allow a standard A-frame coupler to be used), there's nothing wrong with just a very short piece of centre tongue to connect the two A-frame members to a single-tube coupler. There is almost no bending loads at that point, so strength there isn't an issue.
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Re: Drop Floor Canned Trailer Design - Any Suggestions?

Postby KCStudly » Mon Aug 24, 2015 4:20 pm

There is a lot more technical information available from the OEM here: http://www.ucfamerica.com/tech.html

I just skimmed thru it, but it would appear from the size of the mounting bolt holes and pattern, that it is the installer's obligation to set the separately available mounting plates square and true to the frame at the time of installation, thus fixing the alignment once the half axle assemblies are bolted up. In short, it does not appear that there is any provision for alignment after installation.

Why do you want to pick such an over spec'd load rating? On the 8th pg of the FAQ .pdf there is info about de-rating.

Here is the part that everyone forgets when they think that half axles are the solution for a drop floor design; the OEM specifies that a cross member be located between the mounting plates when retrofitting to half axles, "Unless already present it will be necessary to put a cross member on the frame in order to weld base plates, to which the Flexiride® Half Axles are bolted."

So if you need a cross member any way (which you appear to have shown) then why go to the extra expense and difficulty of installing half axles, when a full torsion axle is easier to align and, IIRC, less expensive?
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