pivoting frames and mounting campers

[Sitec]

also thinking the front pivoting mount may be designed with a spring override in case the frame comes in solid contact with the cabin......

You just got me thinking along a totally different line... Thanks! (I'm now picturing two center mounts, on either side of my chassis connecting to the body, and two single leaf springs mounted across the front and rear of the body, resting on a grease-able roller mounted in the chassis... The springs would be set up to carry a percentage of the body load at the front and rear, so the body does not move but the bulk of the body weight is carried by the two fixed grease-able mid mounts... This way, the chassis could do what it pleases under the body, yet the body is still carried on 4 points...)

 

[javajoe79]

You just got me thinking along a totally different line... Thanks! (I'm now picturing two center mounts, on either side of my chassis connecting to the body, and two single leaf springs mounted across the front and rear of the body, resting on a grease-able roller mounted in the chassis... The springs would be set up to carry a percentage of the body load at the front and rear, so the body does not move but the bulk of the body weight is carried by the two fixed grease-able mid mounts... This way, the chassis could do what it pleases under the body, yet the body is still carried on 4 points...)

Sounds pretty workable to me. I guess you would want shocks on the sprung corners. Also normal shackles and rubber bushings seems less complicated and would require less maintenance and you may need a locator on either end to prevent side to side forces from levering on the center mounts.

 

[Amertek Rob]

follow the sheep and go 3point

OK I have given in to the three point system in general, but I will try to figure out a spring override or something to that effect due to my only 2" of sub-frame to camper box clearance,

I found these great urethane pivot bushings, they fit semi trailer suspension spring equalizers (anything that fits semi truck suspension is usually affordable) my price about $30 each, very heavy duty

4" wide and 1 1/8" bolt hole. This is what I have cut so far, more to come

 

[corrupt]

My plan is to stiffen the frame and mount the box on spring mounts with only a single pivot in the rear. At rest, the box will sit on the frame, not the pivot mount. The centerline of the pivot will be on the same plane as the box to frame surface. I am using a heim type mount that will allow it to pivot and twist but no front to rear or side to side movement. The suspension will handle bumps in the road. The spring mounts will allow the frame to twist only when going slow and when the suspension drops into deeper holes. I saw a video on this site of a large, truck based camper that had hydraulic struts that controlled the amount of movement between the box and frame. On the road they limit the movement. Off-road they allow the box to move freely. I like that concept and may use it too.

Do you have a link to that video, sounds interesting. Any updates on your system?
Cheers

 

[pappawheely]

Do you have a link to that video, sounds interesting. Any updates on your system?
Cheers

I have not had much progress on my subframe. Trying to complete my fuel system and I've been on the road working. The video is here: https://www.youtube.com/watch?v=UOrFNuXdews&feature=youtu.be&hd=1

 

[Amertek Rob]

Front pivot in no sub-frame, I'm attaching directly to the frame being it has 10" tall 5/16" rails, rear mounts on the outside of rails.

 

[leunam]

Hello, I'm new here and only speak a little bit in your language, so sorry about that.

I've recently purchased a minibus built over a 4x4 iveco eurocargo chasis. It is welded without pivoting system.

You can see pictures in:

http://www.foro-overland.es/foro/viewtopic.php?f=35&t=2573

Here you can see one of the cross member in the rear, just above the chasis:

One more cross members (left):

There are 5 o 6 trhougout the chasis.

Does anyone have experience in such a vehicle in off road drive? (without pivoting system)

thank you in advance.

Manu

 

[leunam]

Thank you, the cabin manufacturer is Unvi.

They make 4x4 vehicles for national parks, mining companies (like mine) and so on.


http://www.unvibus.com/pdct/autobuses-4x4-all-road/

You can see even the flexibles unimogs with the same body type, google "doñana unimog"

To take the cabin away and insert a pivoting system is out of my budget...

Doesn't this type of build go against the idea of the mandatory pivot system?

Best regards
Manu

 

[Woofythewolf]

"Cheap and easy" copy of the old military design

I'm wanting to put a camper on my soon to be flatbed Isuzu NPR (currently has a box, I'm just going to lop off the top with a sawzall and give the wood deck a more durable finish), and need to isolate it.

Of course, I won't being doing any serious offroading or flexy situations in my 2wd, so I figure the old spring mount front the military trucks would do fine, in addition to stiffening the frame of the flatbed some more (what the horizontal 2.5" x 1/8" tubes are for).






I used the GM/Isuzu Truck body builder manual a LOT, and is why all the bolt on spring mounts have the angled sides (apparently vertical sides create stress points, and so they recommend doing this) and am using a staggered bolt pattern wherever possible, as well as keeping it as close to the center of the web as possible (the closer you get to the flange, the more stress there is)

In the rear is a hinge with a large poly bushing https://www.amazon.com/SLEEVE-BUSHI...8-1&keywords=DOM+sleeve+and+POLY+BUSHING&th=1
secured by a 5/8" grade 8 bolt (single side shear strength of 27,000 lbs). Even if the bushing fails and cracks or something, the box should still be held in place by the hinge bolts and side keepers, as well as all the spring mounts which will be 5/8" threaded rod in the highest grade I can get at Home Depot (probably grade 5).

The wood will remain as is, or replace it with thinner wood and lay strips of old tire tread (2" wide strips the circumference of the tire, glued to the wood for a continuous piece) to give it more cushioning (not sure if this is necessary, but it should reduce the vibration to the camper).

Other notes: the frame is 8.5" tall with 2.8" flanges, all of 6.1 mm (.24 inch) mild steel. Rear is stepped (although not suddenly like in my model, it's a slant over about 10") down to a 7" tall frame, still with 2.8" flanges (which continues to the end).
-Side keeper design isn't done, It'll have some kind of centering system (I saw something earlier in this thread but haven't been able to find it, where it was almost cone shaped so the bed would center itself as it came down).
-The dark grey blocks represent where the leaf springs are, and the end of the frame (where it is big) is the "DO NOT MOUNT BODY PAST THIS POINT" sticker.

 

[Woofythewolf]

@leunam ,

While I could be totally overestimating your truck, since they were used as a PUBLIC bus in tourist areas, I suspect the body may also be a roll cage (albeit a flimsy one) that would be strong enough to hold the entire vehicle relatively rigid (and prevent it from totally collapsing in a roll over).
an easy way to test this would be to drive one wheel on a ramp moderately high (enough to get fairly close to the limits of the suspension), and see if there is any flex in the frame. I suspect there won't be for the above reason (the body being a large integrated roll cage).

-Woofythewolf

EDIT: obviously this is worth what you paid for it and I am not responsible for any damages

 

[leunam]

@leunam ,

While I could be totally overestimating your truck, since they were used as a PUBLIC bus in tourist areas, I suspect the body may also be a roll cage (albeit a flimsy one) that would be strong enough to hold the entire vehicle relatively rigid (and prevent it from totally collapsing in a roll over).
an easy way to test this would be to drive one wheel on a ramp moderately high (enough to get fairly close to the limits of the suspension), and see if there is any flex in the frame. I suspect there won't be for the above reason (the body being a large integrated roll cage).

-Woofythewolf

EDIT: obviously this is worth what you paid for it and I am not responsible for any damages

Maybe. I'll make you know as soon as I figure it out.

Anyway, I'm not thinking about extreme off road with it, just travel, but I'm curious (worried) about its lack of flexibility.

Best regards
Manu

 

[Ramdough]

OK I have given in to the three point system in general, but I will try to figure out a spring override or something to that effect due to my only 2" of sub-frame to camper box clearance,

I found these great urethane pivot bushings, they fit semi trailer suspension spring equalizers (anything that fits semi truck suspension is usually affordable) my price about $30 each, very heavy duty

4" wide and 1 1/8" bolt hole. This is what I have cut so far, more to comeView attachment 369890View attachment 369891

Do you have a link to those bushings?

Thanks

 

[Ramdough]

To the 4 point pivot experienced people (people that build them on a regular basis),

I understand that the front and rear pivots need to be as low as possible and there should probably be a compliant member like a bushing and possibly rubber mounts. The center mounts are often put in the same plane as the front and rear pivots. Is that necessary? Can the center pivots be higher?

I am having trouble visualizing why the height of the center mounts matter, especially if the front and rear ones are on bushings. The center mounts also do not pivot as much as the front and rear.

Thoughts?

Thanks in advance.

 

[Victorian]

The center mounting points are dictated by the truck frame. Also, the center mounts do not move at all, they are fixed. For the pivot mounts I would use bearings and not bushings that could wear out. A big benefit of a 4 point pivot mount is the quiet operation. Spring loaded subframes make grinding and squeeking sounds from metal rubbing at each other... further down the road you may even have exposed metal that rusts and therefore could make things look ugly.

 

[Ramdough]

The center mounting points are dictated by the truck frame. Also, the center mounts do not move at all, they are fixed. For the pivot mounts I would use bearings and not bushings that could wear out. A big benefit of a 4 point pivot mount is the quiet operation. Spring loaded subframes make grinding and squeeking sounds from metal rubbing at each other... further down the road you may even have exposed metal that rusts and therefore could make things look ugly.

Thanks for the reply. You were actually one of the people I was hoping would respond.

Almost all of the center ones I have seen have a pipe or peg with a (sometimes greased) sheet of rubber wrapped around them. I am guessing that rubber is just for taking a load in all directions possible and adding compliance.

Can you elaborate on:

The center mounting points are dictated by the truck frame.

I realize that every frame and truck is different and often there is a lot of machinery (drive shaft, mufflers, other parts) in the way placing the pivots on the frames’ neutral axis, but what drives the location of the center mounts? If the center mounts don’t move at all, can I not mount them higher?

Interesting suggestion on the bearings. I would assume then that you might want bushings or some type of compliant mount to the body or frame to allow some out of axis movement.

Thanks again.