Camper mounting help

[bee]

I plan on using a spring system like this for my Dodge 2500. I think 1 to 2 inches of travel will be sufficient for my build. Does anyone know what strength springs I should be using? Does it go by payload? I will be around 2000lbs

These mounts will not be locating the the camper front to back or side to side, just controlling vertical motion. Anyone have some insight into this setup.

[Alastair D(Aus)]

Bee,
I am planning to use the same method to attach a sub-frame to my Isuzu NPS 300. The subframe will hold storage bozes and tanks and also provide mounting rails for a custom built slide on that will be held down by sprung turnbuckles. This way I will be distributing the weight over the chassis frame and providing 2 levels at which flex can be accomodated. I will also have 1/2" rubber (conveyor belt) between metal at both levels to even out the junction and also reduce noise.

I consider the springs are there to hold the camper & frame down against minor bumping and general road movement, not push against the flex. If in the rest position each spring mount (4 each side in my case) exerts 100kg force then that is a total of 800kg holding down what I estimate will be a 1200 to 1400 Kg camper. Simple physics suggests that if I go over a broad hump in the road than on the downside the camper will be left 'up in the air' and will then come down with a thump. So I should increase the spring load so each has 200kg and hence a total of 1600kg which should restrain the camper for 'slow' rises and falls. This level of tension should not spoil the flexibility when going over uneven ground.

Front to rear and side movement are taken care of by simple brackets and wear pads etc.

The above is my logic and I am happy if you or anyone else can point out a flaw.

cheers
alastair

[Scoutman]

I think I saw where someone used valve springs for what you're talking about. I forget what thread that was in though...

[snowcat]

Hi All, I've used V-8 valve springs for mounting several beds over the years. I've mounted several large water tanks and many flatbeds using valve springs with a grade-8 bolt up the middle. Never had a failure. I build off-road wildland fire trucks and water tenders for use in the American West- I used valve springs to help mount a twelve foot bed with 850 gallon water tank on my 2004 U500 with no problems. My 2500 gallon water tender is also mounted for flex using this method.

[SChandler]

Snowcat, any advice on how to choose a spring rate for the load or do you always use the same spring rate on all of the bodies, regardless of load?

Thanks.

[bee]

damn I thought I had notifications turned on, didn't realize anyone had responded to the post. I do not think valve springs will offer enough travel, though I have heard of people using them. Mcmaster.com sells compression die springs in various lengths and spring rates. My gut feeling is that very little clamping force is needed. Pretty sure I remember reading that fast guns or something like that use 300 in/lb springs, but they also have to help locate the camper.

[Scoutman]

I found the thread I was thinking of....
http://www.expeditionportal.com/foru...uild-Up/page60

[westyss]

damn I thought I had notifications turned on, didn't realize anyone had responded to the post. I do not think valve springs will offer enough travel, though I have heard of people using them. Mcmaster.com sells compression die springs in various lengths and spring rates. My gut feeling is that very little clamping force is needed. Pretty sure I remember reading that fast guns or something like that use 300 in/lb springs, but they also have to help locate the camper.

Lee Springs have a huge selection of springs, before selecting one you have to have an idea of the travel needed and how much resistance, it can be a bit daunting to start but some main points to look for are the length of the spring at rest and at full compress, that will give you the travel available, after that you can choose wire diameter, overall spring diameter, pounds of resistance etc etc...........if you cant find the spring you need at lee Spring it doesnt exist.

[bee]

Alastair. If I am following what you are saying then you could hang your truck upside down and the springs wouldn't allow the camper to separate from the truck frame. Isn't that excessive?

Scoutman hadn't seen that thread before thanks for the link. Gonna take awhile to sift through all those pages.

Westyss once I figure out what spring rate I need lees should be helpful, thanks.

Honestly I drive around all the time with stuff just loose in the bed of my truck. Haven't had anything fly out over a bump yet. I am guessing that it has to do with the difference in weight between the back of your truck and the camper. So If the back of your truck weighs more then the camper box, then theoretically no springs would be needed just a method of locating it to the truck.

So my theory is that if the back of my dodge weighs 2500lbs and the camper weighs 3000lbs then I would only need a total of 500 lbs in spring force to keep the camper and truck together over any size bump. Any thoughts? Its been a while since physics class.

[Scoutman]

Start around page 60.