Spring Mounts for Rail-on-Rail Subframe

#1
Hi all, anyone know of a USA source for the springs for a rail-on-rail subframe? This is for our 1120 and the subframe is 16'x8' (roughly).
 
#2
Before you get too far into the subframe build, I would contact Mercedes directly to find out what build methods they approve. They do supply build information for each of their chassis, although getting hold of the info will be a challenge.
 

Sitec

Adventurer
#3
If you're planning any rough dirt roads or mild off roading, then rail on rail sub frames put the body and chassis under quite a bit of stress... Money is well spent on a copy of Steve Wigglesworth's 'Build your own Overland Camper' book. (ISBN 978 1 78521 076 1). It's got a small section on various ways of mounting body's. We are not planning much 'serious' off roading, but I'm still going to spend a fair bit of time building a 3 point mount allowing the chassis to move under the body. :)
 

Jostt

Adventurer
#4
By my point of view this type of rail subframes are ok if you plan to do light off road, but for extreme torsión is not adecuarse, I agree 100% whit sitec , Diamond subframes are more flexible, the negative point is the price
 
#5
Hey guys, I do have the "Build Your Own Overland Camper" book and am following the design from there (page 64/65). Also the original firebox came with a rail on system much like described in the book (though lighter built than the new subframe). Our plans are more for light off road (but lots of them), not sure a 1120 would be well suited for extreme off road anyway (a Unimog would be way better I would think). I am also guessing that the 1120's frame is less flexible than a unimog, different purpose from the factory. Also the rail on subframe will allow the box to be a bit lower, we have already caught some spanish moss just on the cab of the truck and the habitat will be even higher.

I think I found a source for the springs at https://www.mcmaster.com/#springs/=1cue5m3
 
#6
I have rail on rail. I a would describe myself as a badroader and not really an off roader.

My truck and most of the trucks mentioned on this forum are not really off roaders by design. The chassis are wrong and the wheel bases too long. I guess this is why the unimog exists in the mercedes stable.

I agree totally that 3, 4 point or diamond configurations are probably the way to go for off road.

The problem is that most of us are probably looking at some sort of round the world trip and the fact is that 99% of that journey is actually on some sort of toad be it tarmac, rough gravel or grit etc.
In these circumstances the rail on rail system performes just fine. For that remaining 1 % I am simply in the wrong vehicle with the wrong set up and ot lets me down.

I am currently in South America and its doing ok. Infact I would say that the weakest link the vehicles offroad capabilities is probably me and my abilities.

The rail on rail system works great on bad roads and paved roads.

I have however seen many trucks with home made 3 or 4 point systems that have had to have endless modifications made to make the road driving acceptable. One i saw had at least 6 shock absorbers welded onto eack side to dampen the roll. The owner told me that roundabouts were the worst and it swayed and rocked all over the place.

I guess my point is that all these systems have their pros and cons but i think it is quite easy for the home engineer to make a rail on rail system that is adjustable and works well for most of the time. It is however also quite easy for the home engineer to make a 3 or 4 point system that doesnt work well for most of the time.

I think you really need to know your stuff to get it right first time.
All systems are right if it works for you and does what you need

I also agree that Steve Wigglesworths book is essential and you might even find a few piccies of our truck in there.

Neil

Www.cloud9ontour.com
Www.cloud9isborn.blogspot.com
 
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Sitec

Adventurer
#8
I like that saying... 'Bad road truck' :). I'd like to hope ours would only be a 'bad road truck' when it's done, but some of the places we want to travel to in Australia will mean it'll see more bad roads than good, especially in The Flinders Ranges, Cape York, The Simpson and up into The Kimberley's. The body I've found is over engineered being ex mine, and I've had my truck off road a few times now and the chassis flex as a flat deck truck is amazing/alarming! :) image.jpg
 
#9
I think that slow overlanding down sharp inclines or through mud and rocks etc will only be occasional for most of us as we have spent too much time and money to risk it.

What we have found the most destructive is the corrugated gravel or ripio roads.

Sometimes you start on one of these roads and the violent shaking and vibration through the truck is beyond belief and when you look at the map you realise that you have at least 500km ( 5days ) of this to go.
It shakes the truck to death. If anything is going to kill the vehicle its these.

It tests all the construction you have done to its limit. You sit in the front just hoping that all your cupboards in the back are still on the wall. ( opening them afterwards is a gamble )

When we got to Ushuaia I opened the drivers doorcand it almost fell off. 5 out of the 6 bolts holding it on had worked loose.

These bad roads are very common around the world so I would design your system to cope with these first as these are the ones that will kill your truck.

Great thread. Great thoughts and info

Neil
 
#11
So Neil, as you are probably aware I have used some of the info on your build site for our build (thanks for all the info). Also have seen your truck in the Wigglesworth's book, looks great. Our plans for this truck is much like your travels. So, with a rail on subframe what thoughts would you have about how to isolate/dampen vibration? I had considered a strip of plastic or oak between the 2 rails but stated to wonder of that would just complicate things without much benefit.

I just downloaded the body builder PDF (thanks Joe for the link), it is an old scanned German manual so hard to translate, but it describes the "tellerfedern" based mounting method. These are also known as "belleville washers" (https://en.wikipedia.org/wiki/Belleville_washer) which if stacked properly act as a spring. This is the way the original firebox was mounted. The original subframe was not super heavily built and the box didn't seem to have a damage from flexing. The chassis does not have any visual damage. Not sure how "off road" the truck ever went though. There was a rather heavy pump and central water tank that I would think would have caused some serious stress if ever taken off road. So seeing this method I am assuming a rail-on-rail system is an approved method by MB.

Thanks Micheal for the links, now just need to figure out which springs and or use the belleville springs.
 

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#12
Hi Jon

We do not have any dampening material between the rails and its been fine
What we did do was put several springs at the front of the rail . This gave us the option to either remove or change the tension and thus adjust the rolling effect. So far we havent felt the need to make adjustments.

My cabin is 2.44 meters wide and the chassis rails pretty much divide this width into thirds.

The rails at the front open about 100 mm so the opposite side at the front lowers by about the same. Thes gap when fully open (which is rare) then tapers down to nothing to the rear end of the chassis where the rails are fixed together.

You have to consider this movement and where your cabin cross members sit when designing where fuel tank filler necks will be positioned to ensure that nothing clashes when on full tilt.

Neil

Www.cloud9ontour.com
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#13
Always dangerous to offer free advice, but, after a lifetime in the third world, I would offer this:

The real killer is washboard roads. First world Jeepers obsess over twisting and torsion, but this is not a real issue for extended overland travel where you are mostly on roads, just bad ones. Most people have never really seen washboard (corrugations, tôle onduleé, etc.) as it takes a combination of dirt and a lot of heavy traffic, not a combination often found in the first world. And, as noted by a few posts here, it is that vibration that REALLY damages your truck. (Australia has washboard due to the road trains. The Sahara used to have it. Cameroon certainly did. The CAR, ironically did not - simply not enough road traffic to cause them.)

Torsion can be an issue, but the common "cure" a three point suspension can also be a truck frame killer as it will concentrate all of the weight on three small points on the frame. Dig around and you will find examples of this. For washboard you want all of the weight spread as evenly as possible over as much of the frame as possible.

One way to do this is with a "pull out" mount (used AFAIK) by Unicat and Bimobil. The camper sits on the frame but when there is extreme torsion, the mounting bolts are spring loaded and will pull out.

Observations offered with NO guarantees. Obviously, any approach well executed is better than any other poorly executed.

All the best.

Edited to fix the G@6d@zzzz spell check!
 
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#14
I use stacked belleville washers all the time at work. I usually use them when I need a very high spring rate in a small volume. They work very well, but they do yield if they are not "preset" by the manufacturer. If you get them in the non preset state, they will take a permanent set if you smash them flat. They will be fine if you only compress them about 75%. Some manufacturers sell them "preset". It just means that they smashed them flat a few times before they sell them to you, so you can go to full compression and they will spring back all the way.

I have used belleville washers that are about the size of a penny, and I have used some that were a half inch thick and the size of a dinner plate. When stacked, they do slide on each-other, so I usually lubricate them (especially if they are stainless steel). The inside and outside diameters also change size a little when compressed, so I have had them make little popping sounds then they move on each-other.

Michael
 
#15
Always dangerous to offer free advice, but, after a lifetime in the third world, I would offer this:

The real killer is washboard roads. First world Jeepers obsess over twisting and torsion, but this is not a real issue for extended overland travel where you are mostly on roads, just bad ones. Most people have never really seen washboard (corrugations, tile nodule, etc.) as it takes a combination of dirt and a lot of heavy traffic, not a combination often found in the first world. And, as noted by a few posts here, it is that vibration that REALLY damages your truck. (Australia has washboard due to the road trains. The Sahara used to have it. Cameroon certainly did. The CAR, ironically did not - simply not enough road traffic to cause them.)

Torsion can be an issue, but the common "cure" a three point suspension can also be a truck frame killer as it will concentrate all of the weight on three small points on the frame. Dig around and you will find examples of this. For washboard you want all of the weight spread as evenly as possible over as much of the frame as possible.

One way to do this is with a "pull out" mount (used AFAIK) by Unicat and Bimobil. The camper sits on the frame but when there is extreme torsion, the mounting bolts are spring loaded and will pull out.

Observations offered with NO guarantees. Obviously, any approach well executed is better than any other poorly executed.

All the best.
Diplostrat. I totally agree with your findings. The corrugated roads destroy vehicles. They are hard to imagine until you have spent 8 hours on one and have another 8 tomorrow.

Neil