Rubber spring bolt camper Mount design.

[serpico760]

I came up with this design for mounting my expand-o-van habitat on my M1083 from looking at similar mounting systems including the M1087 mounting system. The lower bracket is made from an I-beam that I have that 6 in by 8 in x 3/8 in thick, and the upper bracket is made from frame rail portions left over from my friend's heavy equipment company and 3/8 plate. I plan on mounting the end closest to the cab in such a way that it doesn't have springs but just has a pivot, and mounting this system in the rear and the middle. I have some thick rubber strips to separate the frames or I may just use wood. Feel free to pick apart my design for flaws or improvements!

 

[Mullaney]

I came up with this design for mounting my expand-o-van habitat on my M1083 from looking at similar mounting systems including the M1087 mounting system. The lower bracket is made from an I-beam that I have that 6 in by 8 in x 3/8 in thick, and the upper bracket is made from frame rail portions left over from my friend's heavy equipment company and 3/8 plate. I plan on mounting the end closest to the cab in such a way that it doesn't have springs but just has a pivot, and mounting this system in the rear and the middle. I have some thick rubber strips to separate the frames or I may just use wood. Feel free to pick apart my design for flaws or improvements!
View attachment 915226View attachment 915227

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It looks to me like you have a nice heavy duty way to secure your box to the frame. The only thing I would like to suggest is more "travel" up and down. Only because of the flex in the frame...

Of course, I don't have measurements.
Your picture might be taller than it appears.

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[TechnoWeenie]

I would be concerned that if there's enough torsional flex, the side walls would actually come in contact and either prevent movement, or bend/break.

It looks like a good idea, though, and to be honest I'd love the CAD file to run to a shop to see if they could cut it.

 

[serpico760]

I would be concerned that if there's enough torsional flex, the side walls would actually come in contact and either prevent movement, or bend/break.

It looks like a good idea, though, and to be honest I'd love the CAD file to run to a shop to see if they could cut it.

I was going to see if the water jet shop could cut my I-beam into chunks for me. Otherwise it may be the plasma cutter which I've never tried yet! What could possibly go wrong...

 

[serpico760]

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It looks to me like you have a nice heavy duty way to secure your box to the frame. The only thing I would like to suggest is more "travel" up and down. Only because of the flex in the frame...

Of course, I don't have measurements.
Your picture might be taller than it appears.

.

That's the standard upper frame section for the lmtv, and the standard lower frame rail for an expando van box. I suppose I could put two springs on top of each other with a washer in between instead of two in a row like that then I would double my travel

 

[coachgeo]

what do you see as this being superior over typical captured metal springs... or captured pair of metal springs?

 

[serpico760]

what do you see as this being superior over typical captured metal springs... or captured pair of metal springs?

Well for one thing finding springs of the right spring rate, rubber will be quieter, newer designs use rubber springs. The M1087 uses rubber springs. And I'm handy with McMaster-Carr website so that's what I found! Suppose I could use die springs also. Try as I might I couldn't seem to find an off the self solution.

 

[serpico760]

I would be concerned that if there's enough torsional flex, the side walls would actually come in contact and either prevent movement, or bend/break.

It looks like a good idea, though, and to be honest I'd love the CAD file to run to a shop to see if they could cut it.

I would happily provide the cad files to anyone who should ask. PM me. CAD is SolidWorks 2022, can be exported as any standard file type.

 

[coachgeo]

Well for one thing finding springs of the right spring rate, rubber will be quieter, newer designs use rubber springs. The M1087 uses rubber springs. And I'm handy with McMaster-Carr website so that's what I found! Suppose I could use die springs also. Try as I might I couldn't seem to find an off the self solution.

for future reference- captured spring vendor(s) / Part numbers used on M1079 is in the yellow spread parts sheet linked to a top of the FMTV forum.

Rubber looked to me like it should work good while ago. My ambo box that came off of a Freighlinter uses rubber isolators. Sadly not really capable of needed stretch... yours likely are though. Nice.

Myself am thinking on putting captures spring on each side mine since they came with the box when I got it. Box will sit on them at rest..... maybe a way to lock the box to the chassis firmly on the idolators for highway driving? Then they function just like designed by ambo manufacture. (SStevens chassis same widh as Freightliner)

 

[Third From Texas]

Looks viable.

You might consider an outer horizontal capture plate on the lower part. Keep thigs lined up during any lateral shift.

ie: capture the upper part within the lower part.

 

[serpico760]

Updated design, 4" of travel, 1/2-13 limit bolt, 2" x 3/8 angles welded to the I-beam on the bottom half for side travel limit.

 

[87cr250r]

That's going to make a lot of racket when those two brackets come together. The springs need to sandwich one bracket, you have them sandwiching both.

Springs or rubber, you're going to need to calculate a weight for the box if you want to suspend it properly. Bolts or shims can be used to adjust preload if you need to fudge things a bit.

You should also include bearings where the angles and plates meet to prevent binding.

 

[serpico760]

That's going to make a lot of racket when those two brackets come together. The springs need to sandwich one bracket, you have them sandwiching both.

Springs or rubber, you're going to need to calculate a weight for the box if you want to suspend it properly. Bolts or shims can be used to adjust preload if you need to fudge things a bit.

You should also include bearings where the angles and plates meet to prevent binding.

My thought was not that the spring system suspends the box but that it captures it when the frame twists the rest of the time the habitat frame is resting on the truck frame separated by a rubber strip or a wood strip.

 

[chucky]

Updated design, 4" of travel, 1/2-13 limit bolt, 2" x 3/8 angles welded to the I-beam on the bottom half for side travel limit.
View attachment 915715

Why not put a rubber bushing on the bolt between the 2 brackets to dampen the landing and kill a little vibration between the truck and habitat ?

 

[hike]

Why not put a rubber bushing on the bolt between the 2 brackets to dampen the landing and kill a little vibration between the truck and habitat ?

If I understand the design the brackets' horizontal surfaces never meet. The 'spacer' between the habitat's bottom rails and chassis' top rails keeps them apart—

 

[chucky]

If I understand the design the brackets' horizontal surfaces never meet. The 'spacer' between the habitat's bottom rails and chassis' top rails keeps them apart—

Yea i get that i was thinking in the picture of the brackets using the washer on the bolt between the blue and the gray instead of going metal to metal when in resting pos.

 

[aw113sgte]

Updated design, 4" of travel, 1/2-13 limit bolt, 2" x 3/8 angles welded to the I-beam on the bottom half for side travel limit.
View attachment 915715

So you have a bolt to limit overtravel in the front? Personally I avoided rubber in this application because it breaks down very quickly under high deflection. It does have the advantage of nonlinear spring rate but if you exceed it, it is destroyed(your overtravel bolt can prevent that). Tradeoffs.
The lower bracket is not clear how it's manufactured, is that milled out of a chunk? A weldment?
As far an isolaters, I put uhmwpe sheet between my box and frame, never noticed any noise or wear.
I went with die springs due to their reliability (I may be a little bitter about having to replace all the rubber parts on my 2007 truck).
I'm running 19 spring sets per side now. Seems to be working quite well. I do not have shear plates at this point(good luck shearing 38 12mm 10.9 bolts) but may put some in place at some point.