Use A Flat Bed Utility Trailer As A Platform For A 7 x 10

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Use A Flat Bed Utility Trailer As A Platform For A 7 x 10

Postby jwh92020 » Sun May 13, 2018 3:57 pm

I have a friend who wants me to help him build a 7 x 10 standy for use on his hunting lease. we have scoured the OK City area for an old pop up frame, but no luck. He suggested buying a 6 x 10 utility trailer (the kind with the vertical supports and a pipe rail or angle iron upper rail), cutting off the verticals and upper rail to make a flat bed. my understanding is that frame is structural to the trailer and would weaken it. I'm not sure that by bolting a 7 x 10 wood frame and sub floor would provide adequate structure back to the frame. I found a 67" x 8 ft flat bed trailer with a 3500 lb axle on it for a great price, but I'm not sure that we can take it to a 7 x 10 platform without substantial welding (which neither of us do). The tires on this trailer are 90" outside face to outside face. Do you think we can safely modify the trailer to what he wants? Thanks.
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Re: Use A Flat Bed Utility Trailer As A Platform For A 7 x 1

Postby Ottsville » Sun May 13, 2018 8:55 pm

The rails and uprights on many utility trailers are not structural. When I worked for a manufacturer, the flatbed trailers were the same underneath as the utility trailers with sides.

You can build a larger box to fit on the trailer, even without welding. Just build a box and bolt it on as long as it is under the weight for the trailer. Or find a local trailer builder and have one made.
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Re: Use A Flat Bed Utility Trailer As A Platform For A 7 x 1

Postby jwh92020 » Sun May 13, 2018 9:59 pm

I talked to a local builder who told me that they were structural I asked him for a quote on Weds last week, never heard from him. Asked another builder for a quote and still haven't received a reply. If I can just build a frame over the existing trailer, I'll do that. The axle is 350p lbs, so I'm sure we are ok.
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Re: Use A Flat Bed Utility Trailer As A Platform For A 7 x 1

Postby Dale M. » Mon May 14, 2018 7:36 am

My impression of the trailers I have seen is the rails are not structural if you look at frames they will be 3 or 4 inch steel channel iron, more strength than any HF bolt together........ My impression of rails are to keep dumb ATV drivers from driving over the edge and hurting themselves or for the landscape gardener to keep mowers and and edgers and trash cans and such on board so they don't have to spend half their working day tieing/untieing them for transport from job to job....

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Re: Use A Flat Bed Utility Trailer As A Platform For A 7 x 1

Postby jwh92020 » Mon May 14, 2018 11:42 am

I just talked to 2 builders this morning. One said they are structural, one said they aren't. I don't see how 12" pieces of angle iron weld to the outside of a frame with some type of top rail are structural. I found a 67" x 96" flat bed with no frame upper "frame". i'm going to see about building a 7 x 10 platform and bolting it to the trailer an use that as a base. It has 3500 lb axle, so it should be plenty strong.
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Re: Use A Flat Bed Utility Trailer As A Platform For A 7 x 1

Postby steve cowan » Mon May 14, 2018 12:35 pm

When I attached the vertical walls and floor to the frame it became real solid and stiff.The frame is only 2 inch angle iron.
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Re: Use A Flat Bed Utility Trailer As A Platform For A 7 x 1

Postby jwh92020 » Mon May 14, 2018 2:38 pm

I thought that if one used a typical utility trailer with the verticals and the top rail and they removed those hings, that the floor and wall framing would not only replace them, but be stronger. Then all you have to deal with is covering the spots where the vertical were removed. Believe it or not, I've contacted 5 builders here in the OKC area over the past week, and not one has gotten back to me with a price.
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Re: Use A Flat Bed Utility Trailer As A Platform For A 7 x 1

Postby greygoos » Mon May 14, 2018 2:40 pm

Post a picture if you can of the trailer you are thinking of using.Someone might be able to give you a better answer.
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Re: Use A Flat Bed Utility Trailer As A Platform For A 7 x 1

Postby jwh92020 » Tue May 15, 2018 9:05 am

This is the type of trailer we are looking at. we have been told the verticals and top rail are structural. we've also been told they're not, If we could get a local welder to respond, we'd have a trailer built, but none have as of yet.

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Re: Use A Flat Bed Utility Trailer As A Platform For A 7 x 1

Postby jwh92020 » Tue May 15, 2018 12:07 pm

I found this trailer just now. The frame is 67" wide by 10 ft 3" long to the point where the tongue connects to the curve. The tires are 73" face to face. Axle is a 3500lb Dexter.If I build a platform and bolt it to the frame, can I safely get an 84" width? We can lengthen the tongue if necessary.

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Re: Use A Flat Bed Utility Trailer As A Platform For A 7 x 1

Postby jwh92020 » Wed May 16, 2018 1:53 pm

So I decided to have a frame built. 83" x 120". 1.5 x 3" steel tube frame, 3500 lb Dexter axle w/brakes, Atwood A Frame coupler, 225/75R15 radials on 15" rims. $850.00. No deck, no wiring, no fenders. Seemed like a good deal to me.
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Re: Use A Flat Bed Utility Trailer As A Platform For A 7 x 1

Postby KCStudly » Thu Jul 26, 2018 2:45 pm

.
Seems like a good deal to me, too.

On structural vs. not structural. It depends. Generally if the main frame rails are a smaller/thinner angle section, then I would assume that the top rails are structural. If the main rails are deeper box or channel section, or thick wall, then it is more likely that the top rails play a lesser structural roll.

Either way, if you replace the uprights and top rail with something even more substantial (like a well constructed box... not necessarily heavy, but rigid and deep in section... like a standy), and competently join them to be unitized, then removing the "structural" upper frame becomes a none issue. Heck, there have been wooden campers built with no metal frame, just a tongue and axle mounts.

So, whether they are needed to meet the specified weight capacity or not, those upper rails are structural due to their geometry. They form a truss. The structural form of a truss spreads the tension and compression fibers out, while minimizing the amount of material required to resist the loads. In a bending moment it is always the outer fibers that see the highest loads, so by moving those fibers further apart the "leverage factor" (if you will allow the simplification) takes affect; the outer fibers see less stress on a longer lever. Shorter lever, more stress. (More properly it has to do with mass centroid vs. cross sectional area placement, or "moment of inertia", but the lever analogy is easier to understand.) Because the load on a flat bed trailer is essentially trying to bend the front and rear decks down over the axle, the top rail is mostly affected by tension, and is therefore less susceptible to buckling so can be a relatively light cross section; and therefore even a relatively small/light section of metal will add substantial strength (just like the tension cables or rods of a railroad truss look minuscule compared to the larger compression members).

Another way to think of it is bending a piece of paper vs. bending corrugated cardboard. One paper ply (or light frame rail) bends easily, but intact, with the outer skins spread apart by the wavy uprights, a corrugated cardboard "truss" or unitized structure, is much more rigid (like a double rail trailer). The truss allows all of the members to be smaller/lighter w/o sacrificing overall load capacity.
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Re: Use A Flat Bed Utility Trailer As A Platform For A 7 x 1

Postby tony.latham » Thu Jul 26, 2018 3:06 pm

I don't see how the rails could not be structural––they form a truss. They have to stiffen the trailer.

However, adding a well-built cabin will do the same thing. Just make sure you bolt it to the trailer in at least four places.

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