Coachgeo
Explorer
pretty sure the Van Truck (M1079) used the above/below spring set up (but don't quote me on that)..... tis why chose similar picture as example.
Captured spring cabin mounting help needed
- Thread starter Coachgeo
- Start date
javajoe79
Fabricator
My plan is to make mounts with 1 spring below. The upper half would be a bracket similar to the pictures above but I want to incorporate the locator into the spring mount as well. I think a solid bar with threads tapped into the end would be welded to the upper bracket and serve as the locator for side to side and fore and aft. Then the spring would go on around the bar and a heavy washer and bolt would capture the spring between the lower bracket and the end of the bar.
Coachgeo
Explorer
Look forward to seeing a drawing of this. Textual description leaves me baffled. The chassis will move downward in an arc from the mount when that sides wheel drops.... how much that arc has to be accounted for I do not know.
Ozrockrat
Expedition Leader
I am going to go against the flow here and suggest you may not need the flexibility in the mounts that you think you do. I have had my rig crossed up numerous times (no rock crawling though) and it has zero articulation. What I have noticed is that while there may of been enough flex in the module to open some of the cupboard doors (this was a lot worse on the ford based rig) it has not caused any problems. For our use which is any road rather than off road the way your module was mounted on the Freightliner chassis is acceptable. With the construction of the fully welded and skinned aluminum module you will be adding a lot more rigidity to the chassis anyway.
With changing to a more flexible system you may also affect where your loading goes on the chassis. Which in turn can lead to other major problems such as stress cracks either in the chassis or at the attachment points on the module.
My suggestion is to leave it as it is and then see if you have a problem. It will cost you nothing (time or $$) to try it. Remember the more flexible you make the mounts the more body roll you have to endure under normal use conditions (i.e. not off road).
Now for some 2nd hand (a friend told me) experience. I helped a German guy in a Man camper who had to rework his mounting points for his spring mounting system (basically the same as the photos you posted) to take the load a lot further out from the chassis (edge of the module). He nearly lost the module while going across a side slope and the module got to rocking sideways and popped some of the bolts. It was the kinetic energy from the sideways rocking movement that proved to be straw that broke the camels back. This was on a camper that has done a lot of off road work over a number of years (Africa, Russia, Mongolia etc).
Now after saying all that if it comes down to it I think you should listen to Joaquin with his background and experience before listening to an untrained web expert like me.
With changing to a more flexible system you may also affect where your loading goes on the chassis. Which in turn can lead to other major problems such as stress cracks either in the chassis or at the attachment points on the module.
My suggestion is to leave it as it is and then see if you have a problem. It will cost you nothing (time or $$) to try it. Remember the more flexible you make the mounts the more body roll you have to endure under normal use conditions (i.e. not off road).
Now for some 2nd hand (a friend told me) experience. I helped a German guy in a Man camper who had to rework his mounting points for his spring mounting system (basically the same as the photos you posted) to take the load a lot further out from the chassis (edge of the module). He nearly lost the module while going across a side slope and the module got to rocking sideways and popped some of the bolts. It was the kinetic energy from the sideways rocking movement that proved to be straw that broke the camels back. This was on a camper that has done a lot of off road work over a number of years (Africa, Russia, Mongolia etc).
Now after saying all that if it comes down to it I think you should listen to Joaquin with his background and experience before listening to an untrained web expert like me.
javajoe79
Fabricator
I'm thinking that most mounts I have seen can't offer more than a couple inches of separation so the sideways movement of the arc can't be much. I would make the hole in the lower just slightly larger than the solid bar to allow for that and prevent any binding. I am also mounting my camper box onto the flat bed with 8 polyurethane body mounts for additional isolation of the camper.
Coachgeo
Explorer
thanks. considered similar but on one or both the outside edges of Camper and chassis bracket. Captured Spring remaining normal. Thought was using telescoping square tube. Outer being say.. reciever stock and either stock reciver bar or home brewed inner if perfectly square inner would bind due to arc.... aka- inner stock might need one side angled from top to bottom a tad bit ... to accomidate arc path. See earlier pic where fellow had flat plate setup that slid along chassis for a view of angle he built into it so on his set up. Appears on his design plan is that as chassis moved down away from camper box this allowed for top of chassis rail to glide along the arc path it needed to travel with out binding that would result if plate was direct verticle.
Coachgeo
Explorer
looks like for this situation there is nothing on the camper box to attach the plate too. The Ambo Box's chassis mounts fall well outboard of the truck's chassis on brackets. Deeper inward under Ambo box in areas that coinside with spots directly above trucks chassis.... appears there is no place to mount a plate too. Thus, don't think Plate idea will work in this situation thus the idea of sliders on outside edge of each chassis bracket. Will look at it closer for final decision. Could concievebly build brackets from points on box edge of box running deeper inward back toward truck chassis to hold a plate slider.
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Coachgeo
Explorer
Got the manufacture's contact info on the rubber mounts used by the Ambo Box body builder. Will check with them on specs. For all I know they are designed to work like a captured spring and they fit within the parameters that I need for this build..... or might manufacture something else that does that will plop right into the OEM mounts that came with the Ambo that am presently thinking I'll have to modify. Maybe I'll get lucky and they got what I need.
Coachgeo
Explorer
Yep into offroad adventures. My last rig was a ruff Unimog diesel 404. between then and now have been down the hill thru, death of finace', death of both parents, bankruptcy, followed by homeless and back up the other side of hill to fianally again owning a home and truck with Expo rig potential. Working 6.5 days a week these days to get caught back up and make this all happen . Granted all that was a long journey while have only had truck for a short year in my posession. Ambo box only 3 months. Rain every week and winter made it a bit hard to just... "mount the F'n box"
It will get done at a turtles pace. Cant afford to do things more than once in order to "get it" reasoably right.
It will get done at a turtles pace. Cant afford to do things more than once in order to "get it" reasoably right.
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Ozrockrat
Expedition Leader
I am with Jack on this although I may of used different wording 
. From my 20000' internet viewpoint I get the feeling that your Unimog experience may be biasing your judgement towards allowing for a level of frame flexibility you have experience with. So here are a couple of suggestions.
Would it be possible to use a threaded coupler in the existing ambo module mounting bolts. Then you could mount it as they did for the ambo and add springs if needed in the future. Looking at my ambo module mounting I am not sure where you would fit the locating plates. You only have aluminum box to bolt through so I would imaging you would need to weld in stiffener plates and use crush tubes. Or just use aluminum locating plates and weld them to the ambo base.
With the height and location of your chassis you should be able to get access to the mounts easily when it is on for modifications if needed.
Way back in the old days I used to do reliability engineering. We spent a lot of time engineering out failure points. One thing I did learn was to keeps things as simple as possible and only add complexity where absolutely necessary.
. From my 20000' internet viewpoint I get the feeling that your Unimog experience may be biasing your judgement towards allowing for a level of frame flexibility you have experience with. So here are a couple of suggestions. Would it be possible to use a threaded coupler in the existing ambo module mounting bolts. Then you could mount it as they did for the ambo and add springs if needed in the future. Looking at my ambo module mounting I am not sure where you would fit the locating plates. You only have aluminum box to bolt through so I would imaging you would need to weld in stiffener plates and use crush tubes. Or just use aluminum locating plates and weld them to the ambo base.
With the height and location of your chassis you should be able to get access to the mounts easily when it is on for modifications if needed.
Way back in the old days I used to do reliability engineering. We spent a lot of time engineering out failure points. One thing I did learn was to keeps things as simple as possible and only add complexity where absolutely necessary.
Coachgeo
Explorer
Unimog frame twist comparision with the LMTV.... nah...... This aint no unimog lol. If it was would be looking at completely different mount system. captive spring is just fine for this...... and as mentioned is exactly what the Military used on these trucks as well (m1079 w/van body)I am with Jack on this although I may of used different wording
Would it be possible to use a threaded coupler in the existing ambo module mounting bolts. Then you could mount it as they did for the ambo and add springs if needed in the future. Looking at my ambo module mounting I am not sure where you would fit the locating plates. You only have aluminum box to bolt through so I would imaging you would need to weld in stiffener plates and use crush tubes. Or just use aluminum locating plates and weld them to the ambo base.
With the height and location of your chassis you should be able to get access to the mounts easily when it is on for modifications if needed.
Way back in the old days I used to do reliability engineering. We spent a lot of time engineering out failure points. One thing I did learn was to keeps things as simple as possible and only add complexity where absolutely necessary.
Like your idea of threaded coupler. Have condidered this and most certainly not discounted it. Awaiting word from Ambo Body Builder if the studs at bottom of box are threaded in to the base of box..... orrr?? Hope so..... then longer stud will be easier to do. Also Awaiting word from manufacture about specs of rubber vibration isolator that OEM used to mount these as mentioned in http://forum.expeditionportal.com/t...in-mounting-help-needed?p=2282883#post2282883. LIke said there for all I know that mount is speced out to act like a captive spring or the manufacture may have something else that will work.
you did just spark a new idea though so MUCHO THANX for that. On this truck the transmission protrudes above the chassis just a bit and might require spacing the box up 4"-6" to not hit it. Soo.. since spacer required anyway.... then cut the studs below the box shorter and rethread them. Use that to bolt on a spacer that contains bolt at needed length below and maybe also a top captive spring. With new bolt at proper length it will then be long enough to go thru OEM bracket to a captive spring below. After that just got to figure out locating guides/slides. hmmmm
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Ozrockrat
Expedition Leader
Just as another thought. My ambo module on the Landcruiser in Australia is mounted with urethane isolator son both sides of the chassis mount. You could take this to another level and make it a 3 layer isolator. Bolt, big arsed washer, urethane,ambo mount, urethane,chassis mount, urethane, big arsed washer, nylon nut. There would need to be a crush tube setting the tension between it all. If you don't have access above the ambo mount then a 2 layer one would work as well.
