Independent Suspension on an Airstream - Timbren Axle-Less Suspension

[BoldAdventure]

I've been thinking about independent Suspension on the Airstream for long time. And today, I learned that Timbren makes an Axle-Less system.

http://timbren.com/axle-less/

They produce a system to support axle weights up to 7000lbs. They also offer them in both lift and drop configurations, allowing for more or less height.

Anyone have any experience with this yet?

They're designed to be direct bolt-ons, sold as a pair, and the pricing is incredibly attractive.

[DKB_SATX]

Within their range of motion, Airstream's torsion axles are independent. The motion of the wheel on one side doesn't affect the wheel on the other side of the axle.

The ability to raise/lower with the Timbren system seems useful, though I guess you can't lower it much more without hitting the wheel wells. I'd want to be sure that the axle flange is strong enough to take all the force of the suspension without the cross-member of the torsion axle to potentially resist twisting forces from tire impacts, etc.

[lewster]

Kind a reminds me of the old Mor-Ryde system that the older Avion trailers used.

[Action]

Pricing didn't look that attractive for a 5200# after one got some brakes on it. At least for the dealer tha I saw on line.

>>>>>>>Action

[USAtraveler]

Thanks for the tip, Bold. I bookmarked the page. What is your read on "incredibly attractive pricing"?

[Scorge-ION]

Bold Adventurer,
I’ve never owned one or used one. However, I looked into them a few years back to replace the axles on my car carrier – utility trailer.
1. I’m unaware of any trailer suspension system anywhere in the world that’s as good as the one that your Airstream came with. And the Timbren is good – much better than leaf springs and a drop axle – but not as good as your current one.
2. The Timbren uses a rubber spring. Expect to replace them every three to five years like a tire.
3. The Timbren doesn’t use shock absorbers; it gets the little damping it has via the rubber’s viscoelasticity. It doesn’t even come close to a hydraulic shock aborber’s damping. Think of bouncing down the road on four rubber balls. Sure, the rubber has its viscoelastic properties enhanced so it’s not exactly four superballs but still… Sure, you could add shock absorbers but you would need to engineer them in.
4. I don’t believe it has as much wheel travel; I’d have to go back and check the specifications to be sure. It compresses a chunk of rubber whereas the Henschen uses a spring steel torsion bar with four rubber pieces surrounding it to augment the shock absorber. This spreads the stresses over a steel bar about three feet long, vs. six inches of rubber.
5. Your Airstream and suspension were designed around each other and it’s a well-proven system. Replacing it would be a job for a structural engineer and a chassis engineer with computer time to run a few finite-element calculations. Otherwise, you’re risking structural failure and liability issues.


Henschen axles are wonderful creations that really make the Airstream. Fully trailing arms like both the Henschen and the Timbren are difficult to engineer. Take the bearing that supports the arm and calculate the stress of a three-ton trailer sliding on black ice. The sideways force on the wheel could easily be six tons when it hits a curb. I’ll assume the arm is about two feet long and it rides on a four inch (urethane bushing?) bearing. 24”/4” = 6. So it’s about a six to one lever arm, making the force on the bearing about 36 tons. I would much rather trust something that has decades of proven dependability than to try to re-engineer something that just might be a little less expensive after the sunk costs of engineering.
When I think of Airstream, I think of Hot Rod Magazine’s Brakes and Suspension book wherein the leading illustration of trailer brakes was a car with brakes and tires smoking as it stops with an Airstream in tow. Why? Because Airstream has had the best braking performance for decades. Why? Light weight and fully independent suspension. The rear axle is decoupled from the front so the torques don’t try to lift the front axle, depriving it of braking effect. Why do we have brakes? So we can go fast. Better brakes mean you can go faster safely.
Happy adventures, Dave the Scourge of the ION

[TouringDan]

Scorge

Thanks for the explanation of why it is best to stick with the original Airstream suspension. New solutions always have new problems.

Dan

[tjdonahoe]

You would need a better frame to fasten them to, or build a frame to hold it..I just finished installing a dexter lift kit on our classic 31', 3" higher, not much under there to bolt to..

[Pickle62]

I just emailed etrailer today to get some technical info on the Timben axels, Silver streak used some strange I beam axels in the 60's which I can't find brakes for. I would be happy to forward what they send me. The reviews I have read are mostly positive.

[Can of beans]

I think those axles have a specific use in mind, when you want to run a drop deck in between them without the tube in the way, or run a over width Trailer. Either way you would have to reinforce the frame to transfer
the Moment (Torque) created by that type of mount across to the other side. It would be pretty large without the axle tube to take it.
Torsion Flex axles are independent, they do have limited travel, but they are a good design compromise for low height good ground clearance wheel travel.

[truckasaurus]

I don't have much feedback really but I've installed them on my vintage rebuild with new frame and there's at least one other user who has them. There's a lot of features I liked about them including the ease of replacing the rubber blocks and the slick mounting choices along with simplicity of ride height adjustment. The HD model I chose has great travel and seems well built. Still when my rebuild is complete I'll know more. There's some pics in my super sized sixties sovereign thread

[xrvr]

Is any of this related to the adjusta ride suspensions on the eighties Avions. Four independent axles on a four wheel trailer.

[Argosy2]

From what I've seen on my argosy frame off you would have to rebuild your frame. Existing axels are tied across and are structural in my opinion.

[cabinetmaker]

Bolt on? I see alignment issues...It's hard enough to align full length axles let alone 4 independent levers like these.

I'm sure there are applications where they work ok but towing a lot of weight over a lot of miles I would stick to the dexter.

[Rocinante]

Here's another thread where "TheMarco" put on an independent suspension for his Airstream. For as far as this thread went, he seemed to like it quite a bit.

http://www.airforums.com/forums/f7/i...ml#post1523453

[slowmover]

Originally Posted by Pickle62

I just emailed etrailer today to get some technical info on the Timben axels, Silver streak used some strange I beam axels in the 60's which I can't find brakes for. I would be happy to forward what they send me. The reviews I have read are mostly positive.

Airstream used to use the same supplier, HADCO. Far superior to the Dexter of today.

Brakes can be adapted. My current and previous ones had already been done. A big truck trailer service shop can handle this.

You should also disassemble the leafs and the rest. Replace or repair worn parts. New shocks.

One could convert, but torsion axle would be the way to go. Same as above, but also a Dexter dealer.

[slowmover]

[QUsOTE=avionstream;1918833]Is any of this related to the adjusta ride suspensions on the eighties Avions. Four independent axles on a four wheel trailer.[/QUOTE]

Theyre not independent. Leaf spring linked. Marginally better then regular leaf type but not as good as torsion.

[rostam]

Avion was using Adjust-a-Ride suspension until 1988. Starting in 1989, they switched to torsion axles as a cost cutting measure.

Adjust-a-Ride was developed by Bill Stroppe, a veteran of the Indianaplois 500 and a noted race car suspension engineer. Compared to torsion axles, Adjust-a-Ride dampens rough road forces measured in "G" force much better. AFAIK, Adjust-a-Ride is the only fully independent suspension on any travel trailer ever made. My RV shop said they have never seen such a suspension on any trailer.

[slowmover]

Originally Posted by rostam

Avion was using Adjust-a-Ride suspension until 1988. Starting in 1989, they switched to torsion axles as a cost cutting measure.

Adjust-a-Ride was developed by Bill Stroppe, a veteran of the Indianaplois 500 and a noted race car suspension engineer. Compared to torsion axles, Adjust-a-Ride dampens rough road forces measured in "G" force much better. AFAIK, Adjust-a-Ride is the only fully independent suspension on any travel trailer ever made. My RV shop said they have never seen such a suspension on any trailer.

It's just stub axle. Cut the full length in half. But otherwise no different than conventional leaf. Semi independent in a minor way. Still same lousy roll center. Still limited wheel travel. No large advantage. An Airstream is much more stable.

And the reason they've never seen it otherwise at the RV shop is that it isn't particularly good enough for anyone else to want to use. Thus you might want to order those stub axles to have a pair just in case as Dexter does not stock them. Custom order only.

Converting to torsion would be better. Less to go wrong, not just improved handling and braking. Far, far fewer parts. Maybe six versus fifty. Old as your trailer is, you should be on about the third complete tear-down by now as leaf types have shorter maintenance and repair intervals than torsion. Every leaf separated. Every small item replaced and/or upgraded.

Good luck.

[rostam]

Adjust-a-Ride is a fully independent suspension system. Each wheel can travel independently of other wheels -- The closest thing you get on a modern car. Being better than torsion axles in dampening road forces or in handling characteristics is not my opinion. It is the result of a study by Avion. Its measurable and objective (unlike subjective opinions you can find online). These axles, unlike torsion axles, do not go bad after 15-20 years.