nnamssorxela
Adventurer
mounts directly on top of the frame using the factory mount points. Springs under, contained in the C-channel of the truck frame.
pivoting frames and mounting campers
- Thread starter lehel1
- Start date
nnamssorxela
Adventurer
The only thing I'm not sure about is the spring compression. It looks like all the springs in these setups only allow about 1-1.5" of movement. But I suppose that's 1" that I didn't have before!
rruff
Explorer
I think the Earthcruiser is more like 3". You'd need more, the further you get from the fixed point... and there I'd have the longest springs that can fit in your frame... at least.
If you do the test that Sitec mentioned, I think you'll find that the frame itself "wants" to twist a huge amount. Your springs and subframe will stiffen this a bit, but you don't want to restrict it too much. It's a balancing act to keep torsional stress in the truck frame, subframe, and camper in check.
If you do the test that Sitec mentioned, I think you'll find that the frame itself "wants" to twist a huge amount. Your springs and subframe will stiffen this a bit, but you don't want to restrict it too much. It's a balancing act to keep torsional stress in the truck frame, subframe, and camper in check.
nnamssorxela
Adventurer
I see what you're saying, but if I wanted say 8" of travel but the spring can only compress 20%, I'd need a 40" long spring! Looks like even the large vehicles are using a spring about 6" long.
nnamssorxela
Adventurer
After digging around, it does seem that the "die springs" referenced earlier in this thread are one of the better suited and readily available springs. A 6" spring travels 1.5" which is not much IMO.
rruff
Explorer
Here's an example of a 6" spring with 3" travel and 300 lb load. https://www.mcmaster.com/96485k141/
8" spring with 4.3" travel and 445 lb load. https://www.mcmaster.com/96485K205/
These are larger than what people seem to be using though... and you are right, the ones people use do not seem to offer lots of travel as a rule.
8" spring with 4.3" travel and 445 lb load. https://www.mcmaster.com/96485K205/
These are larger than what people seem to be using though... and you are right, the ones people use do not seem to offer lots of travel as a rule.
All the talk Ive seen about spring travel all refers to spring compression which is obviously limited by the free space between the coils of the spring.
My question is, why is no one using a spring in tension so that the travel is far less restricted and you can start with a compact attachment that then expands as the chassis twists and flexes?
That was my plan at least unless anyone has a logical reason why it wouldn't work?
Edit: Will be easier to fabricate as well as the spring can be attached lower on the chassis and all you need to account for is keeping the sub frame/chassis located with respect to each other (a couple of fixed points at either end will do that) and guide the sub frame back to its original position after the torsion force is removed and the sub frame and chassis come back into contact with each other
My question is, why is no one using a spring in tension so that the travel is far less restricted and you can start with a compact attachment that then expands as the chassis twists and flexes?
That was my plan at least unless anyone has a logical reason why it wouldn't work?
Edit: Will be easier to fabricate as well as the spring can be attached lower on the chassis and all you need to account for is keeping the sub frame/chassis located with respect to each other (a couple of fixed points at either end will do that) and guide the sub frame back to its original position after the torsion force is removed and the sub frame and chassis come back into contact with each other
rruff
Explorer
Do it!
One thing I can think of is that there isn't an inherent limit... the spring will keep expanding til it fails... and your subframe and camper fly away. But you could provide a limit by other means.
Usually I assume that if no one is doing it there is probably a very good reason... but this is such a niche field, that maybe that logic doesn't work...? I'm actually using PU mounts as a pivot and I haven't seen anyone try that either...
I think its one of those things where if everyone seems to do it one way and it works well enough, then there is no reason to reinvent the wheel.
Wouldn't be hard to incorporate a way of limiting the travel in the guide so when it reaches the limit it stops the spring being over stretched, but still allowing a lot more travel.
The biggest issue I see with compression springs and specifying a length is that its pretty hard to get a true level of torsion from simply trying to test an empty truck with no bed/sub frame.
A loaded truck is going to behave differently than an empty one...and one thats got a few thousand kilometres (or miles if you prefer) of rough road travelling is going to behave differently again.
I think it might be time to start drawing up a mount using a spring in tension...
rruff
Explorer
I dont think a 3 point pivot is ideal or even warranted on some of the smaller trucks. I know Hino specifically says the 300 series 817 4x4 (my truck, on order...if it ever gets here) is not to have such a pivot system fitted after SLRV tried and found it was less than ideal as it made the ESC play up with all the weight shifting.