Air Spring Help

[Witchdoctor]

Is there a member that could help me with some info/advise on lobe style air springs?

Looking at using them on the new trailer suspension, seen a few on defenders via youtube but having trouble finding the size that will possibly work for my use.
The trailer design will have independent suspension & if it will work use air springs rather than traditional coils in combination with quality shocks.

Tips would be greatly appreciated.

Thanks
David

[Bush65]

No reason why they shouldn't work for your application. I've long thought of converting my boat trailer for offroad use with air springs, just not high on my list yet.

Firestone are one of the better and larger manufacturer of air springs. They have engineering manuals with good design information that are available as pdf's online. PDF here (http://www.firestoneindustrial.com/site-resources/fsip/literature/pdf/AirideDG.pdf)

There are also books in pdf format that list a range of their springs with sizes for aftermarket use in trucks, etc. - the North American (http://www.firestoneindustrial.com/site-resources/fsip/literature/pdf/AftermarketReplacementGuide2010.pdf) and European (http://www.firestoneindustrial.com/site-resources/fsip/literature/pdf/EuroCat_West_08.pdf) ranges are different.

All catalogues here (http://www.firestoneindustrial.com/literature.aspx) note many pages of listings.

These are far cheaper to buy from the USA online.

Edit: Try starting here (http://www.truckspring.com/suspension-parts/firestone-air-bags/heavy-duty-truck/reversible-sleeve-air-springs.aspx).

[isuzurover]

... I've long thought of converting my boat trailer for offroad use with air springs, ...

That is what I plan to do as well.

[Bush65]

That is what I plan to do as well.
Sorry for going slightly off topic.

Besides better ride from air springs on many kms of corrugations and being able to increase the ride height in rough stuff, my conversion would use larger wheels and tyres (same as tow vehicle) so the ability to lower the springs will help with launching on improvised ramps.

I was also planning to retain solid trailer axle but locate it with reversed (trailing) Land Rover radius arms.

[Witchdoctor]

I'm working on independent suspension.

Utilising a wishbone design with the air springs.

Also using design cues from Tatra's king frame.

Thanks for all the information.

David

[isuzurover]

Sorry for going slightly off topic.

Besides better ride from air springs on many kms of corrugations and being able to increase the ride height in rough stuff, my conversion would use larger wheels and tyres (same as tow vehicle) so the ability to lower the springs will help with launching on improvised ramps.

I was also planning to retain solid trailer axle but locate it with reversed (trailing) Land Rover radius arms.

That is pretty much exactly what I was planning too. I posted a thread on it a while back in the trailer or fishing sections.

[roverrescue]

david,
if you are building from scratch. Ignore independent in my opinion!
Run a good triangulated 4link or radius arm with panhard onto solid axle.
Cross axle load sharing and fixed camber and toe geometry outweigh by a long way an inde set up.
Inde are just popular and easily packaged, not necessarily the best way to do it.

Steve

[Bush65]

david,
if you are building from scratch. Ignore independent in my opinion!
Run a good triangulated 4link or radius arm with panhard onto solid axle.
Cross axle load sharing and fixed camber and toe geometry outweigh by a long way an inde set up.
Inde are just popular and easily packaged, not necessarily the best way to do it.

Steve
I agree pretty much with that. The best independent suspension I have seen for trailers is the "MC2" system on the army trailers and TVans.

Besides what Steve pointed out, most swing arm independent systems are too short, and show poor engineering in their design detail. Short arms create too much angle change at the spring seat for use with air springs.




Sorry for going slightly off topic.

Besides better ride from air springs on many kms of corrugations and being able to increase the ride height in rough stuff, my conversion would use larger wheels and tyres (same as tow vehicle) so the ability to lower the springs will help with launching on improvised ramps.

I was also planning to retain solid trailer axle but locate it with reversed (trailing) Land Rover radius arms.

That is pretty much exactly what I was planning too. I posted a thread on it a while back in the trailer or fishing sections.
Ben, I'll have to have a search for your thread.

It was a good while ago when I decided to convert my boat trailer for off road use and those were my thoughts back then - It will still be some time before I get onto it.

Thinking of it again, before dropping off to sleep last night, I now think the disadvantage of radius arms with air springs is not worth their simplicity - I had radius arms laying around back then, but got rid of them before moving.

My thoughts are that it would be better to use a parallel 4 link + panhard system with air springs. This would not be very complicated in my case because I don't have to consider braking in the geometry.

[isuzurover]

I agree pretty much with that. The best independent suspension I have seen for trailers is the "MC2" system on the army trailers and TVans.

Besides what Steve pointed out, most swing arm independent systems are too short, and show poor engineering in their design detail. Short arms create too much angle change at the spring seat for use with air springs.


Ben, I'll have to have a search for your thread.

It was a good while ago when I decided to convert my boat trailer for off road use and those were my thoughts back then - It will still be some time before I get onto it.

Thinking of it again, before dropping off to sleep last night, I now think the disadvantage of radius arms with air springs is not worth their simplicity - I had radius arms laying around back then, but got rid of them before moving.

My thoughts are that it would be better to use a parallel 4 link + panhard system with air springs. This would not be very complicated in my case because I don't have to consider braking in the geometry.

Here are the threads I was thinking of:
http://www.aulro.com/afvb/trailers-vans-campers/131001-offroad-boat-trailer.html
http://www.aulro.com/afvb/trailers-vans-campers/130707-trailer-tech-2.html
Though I also had a lot or email discussion with Steve / Roverrescue - who had plenty of great advice.

What are the disadvantages of RAs for a trailer? It is not like you need a lot of wheel travel...

[roverrescue]

Ben, i dont think RA would have any great negatives on a trailer.
If you used rover arms, unless you axe the front chassis mount from a donor chassis, i would think there would be a bit of time burn in fabricarting the large pivot mount.

For fabricating simplicity, NB32H will accept 45 series tojo spring bushes. A bunch of ebay poly urethane bushes and a stick of nb32h and some 6mm plate and voila. Make up triangulated 4 link?

S

[Bush65]

Here are the threads I was thinking of:
http://www.aulro.com/afvb/trailers-vans-campers/131001-offroad-boat-trailer.html
http://www.aulro.com/afvb/trailers-vans-campers/130707-trailer-tech-2.html
Though I also had a lot or email discussion with Steve / Roverrescue - who had plenty of great advice.

What are the disadvantages of RAs for a trailer? It is not like you need a lot of wheel travel...
Thanks Ben - they made for interesting reading.

Radius arms will be ok if you don't want a lot of travel from the air springs.

For more travel the angle change of the spring seat, reduces allowable travel - instead of measuring min/max allowable heights at the centreline of the air spring they must be measured on the shortest/tallest side of the air spring when the seat is tilted. You also have to be careful to aviod the bellows rubbing on the top edge of the piston where it tilts to one side.