Design discussion: Integrating the Trailer frame

[Alan_H]

I'm still in the design process for my TD. I plan to have a basement, so this discussion will likely focus on trailers with basement (below the bed) storage.

Lately, I have thought about some items I see in designs for the floor of TD's.

Floor Design: Lots of folks do sort of a torsion box framed floor and incorporate insulation to serve dual purpose of (1) reducing flex from the trailer to the TD, and (2) adding R-value to the floor so they don't have heat or cold seep through from beneath them. As a note to these thoughts, the bulkheads in our designs do a lot to reduce the twisting, especially the rear one, but also the front one (headboard). The foam mattress that most of us use is quite a bit of insulation in itself.

Aerodynamics under the trailer: The frame itself with all the cross-members and voids between them, creates a lot of disturbance in the air flowing under the trailer. Some folks have incorporated some sort of a belly pan to help the air flow under the trailer.

What if one, as part of a basement TD design, incorporated the Trailer frame into the design?

I am using a NT 5'x8' bolt-together trailer.

1. How would this affect the trailer design? The bottom "floor" could be bolted from below to the frame rails and cross-members, just like folks currently do, and serve as load-bearing for items in the "basement" area. Bulkheads could be positioned on cross-members to add to the strength and torsional rigidity. Additional bulkheads could be mounted as dividers in the basement and to add to the strength of the TD shell.
2. Would this be an effective "belly-pan"?
3. What are the ramifications of bolting through the floor for items such as the tongue bars, rear hitch for attachments and side-tables, and the axle? (I'm using a torsion axle, not the sprung axle that came with the trailer kit.
3.a. would it be ok to go through quality plywood that is sealed to prevent water intrusion, or should hardwood be inserted for load bearing and to reduce likelihood of the plywood crushing out from the load?
3.b. --OR-- should these items be bolted to the frame and the floor be trimmed to go around these items?

Let's hear your ideas please!! I would be interested if I'm on a good track, or heading toward future failure by using this idea.

See the below image I did to give a visual representation of this idea.

[jstrubberg]

Alan;

Interesting idea. I'm not sure the additional work would be worth the dividend, but as Benjamin Franklin said "What use is a newborn child?".

Another option would be a lightweight "belly pan", just a sheet of light gauge metal (18 gauge?) screwed to the bottom of the frame after completion. It's a little extra weight, but you would have to make minimal design changes and it would let you use the space in and around the frame for wiring, too.

[Vedette]

We have basements in both of our trailers (see my build photos in my album) and LOVE them!
We also have full smooth bellies. The strength and insulating factors are incredible.
If you are trading out the axle anyway. I would sell the store bought bolt together trailer you purchased and put you money to better use by building a custom chassis.
Good Roads
Brian & Sandi

[Alan_H]

Alan;

Interesting idea. I'm not sure the additional work would be worth the dividend, but as Benjamin Franklin said "What use is a newborn child?".

Another option would be a lightweight "belly pan", just a sheet of light gauge metal (18 gauge?) screwed to the bottom of the frame after completion. It's a little extra weight, but you would have to make minimal design changes and it would let you use the space in and around the frame for wiring, too.

Thanks for the feedback! I still planned for the wiring to be in the frame area, I will be in flexible plastic conduit, but in this case would be fully weather protected as well.

As far as design changes, that's no big deal, as I have probably done over 20 different designs already trying to get the the functionality that I want within the dimensional parameters that I have imposed upon myself. Additionally, this would add almost 3" of basement space, other than getting items over the frame, without the addition of those 3" to the overall height of the trailer.

[Alan_H]

We have basements in both of our trailers (see my build photos in my album) and LOVE them!
We also have full smooth bellies. The strength and insulating factors are incredible.
If you are trading out the axle anyway. I would sell the store bought bolt together trailer you purchased and put you money to better use by building a custom chassis.
Good Roads
Brian & Sandi

Hey Brian,

Thanks for the feedback!

I have read both of your build threads, and some of your ideas are incorporated into my design specs as well.

I got the NT 5'x8' Aluminum trailer for the weight savings. I am going to weld the main frame together (have TIG welder) as additional strength, but I couldn't get anywhere near the same price in trying to build an aluminum frame trailer as the price on this NT kit. I already have the factory axle and springs listed for sale, and the torsion axle ordered.

[Alan_H]

Anyone else have any input on this idea?

[Alan_H]

Does anyone have input on question #3?

[Alan_H]

I guess no one has any reasons I shouldn't proceed with this design as far as structural integrity, so I'll proceed with the design. Thanks for looking folks.

[noseoil]

A bit late to this thread, but it seems to me you might want to consider a hybrid design where there are a couple of steel rails sandwiched inside the floor to use for your hard points for fastenings.

I'm thinking the tongue attachment & axle assemblies might want some better fastening points than just the wood itself, if I'm understanding you correctly. If you used 2 rails of 1 1/2" tubing as a part of the floor, & then built it with the steel for the mounting points, it would probably work out well enough & be a bit stronger than a wood box. Just my $0.02 worth.

[Alan_H]

A bit late to this thread, but it seems to me you might want to consider a hybrid design where there are a couple of steel rails sandwiched inside the floor to use for your hard points for fastenings.

I'm thinking the tongue attachment & axle assemblies might want some better fastening points than just the wood itself, if I'm understanding you correctly. If you used 2 rails of 1 1/2" tubing as a part of the floor, & then built it with the steel for the mounting points, it would probably work out well enough & be a bit stronger than a wood box. Just my $0.02 worth.

@noseoil, thanks for the input, and it's not too late, as I'm not building yet, just designing.

I have the NT 5'x8' Aluminum frame trailer kit. I'm going to put the 5'x8' frame section inside the "wood box" and then attach the axle and tongue through the box to the "internal frame".

My main question being, will this be OK through sealed plywood, such as with "the mix", or alternatively epoxy, for the attachment points? Or, will this lead to premature failure due to being bolted through wood?

[DrewsBrews]

If the NT trailer is anywhere close to the HF design there are plates of angle steel for the spring mounts. That should spread the load out pretty well. However the tongue attachment maybe could use a little reinforcement such as similar angle plates between the tongue bars and ply at the front where the weight loads up the tongue. Maybe overkill, but I could see that area getting lose over time.

[Alan_H]

If the NT trailer is anywhere close to the HF design there are plates of angle steel for the spring mounts. That should spread the load out pretty well. However the tongue attachment maybe could use a little reinforcement such as similar angle plates between the tongue bars and ply at the front where the weight loads up the tongue. Maybe overkill, but I could see that area getting lose over time.

Good point, I may consider that. I'm ditching the spring mounted axle and going with a torsion. I've been considering adding in additional reinforcement to spread the load of the axle across the frame similar to the spring mount for the original axle.

However, I hadn't thought of checking for loading on the tongue.

I am thinking of doing the stretched tongue modification though, so that will take some of the load off of the angle pieces for the tongue rails.