Air Assist on Front Forks, VL800 - Page 2 - Suzuki Volusia Forums : Intruder Volusia and Boulevard Forum
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post #11 of 54 (permalink) Old 10-03-2013, 10:29 AM Thread Starter
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Originally Posted by OzriderC50T View Post
Every air suspension system I have ever seen is based on a sealed bladder system, I have serious doubts that a seal designed to hold back fork oil that is not under any pressure would come close to supporting the forces required for an air suspension system.
Yeah, most of what I've seen for air shocks/springs involves bladders, Haven't found a good exploded diagram for air ride forks (I've seen the forks, just not how their internals are designed). An air piston though is an entirely different animal more akin to a steam engine's or a hydraulic piston.

To some extent our fork seals are designed to hold back oil under pressure as there are no vents in our forks to bleed of pressure. The evidence to support this is the fact that with no other modification (aside from adding the valves to the caps) the forks hold pressure. Just like in our engines, as the forks volume decreases during compression, the pressure inside increases. I've no doubts that the sliders and tubes can hold back at least 200PSI without failure, air assist shocks have much thinner shells and add 500 to 1000 lbs. per shock of additional support/lift at around 100PSI for similar surface area (far above our needs). The question falls to the difference in seal design between air pistons not typical air suspension design and our forks. A good example of the force that can be generated with an air piston of similar bore is the actuator piston from the 1969 Roper/White Spot welder at our shop which at 100PSI is capable of 900lbs of compression force according to the builder's plate. The seals on this unit are "O" rings, one on the piston, two on the cylinder. The piston is 1.25".

There's a lot to be researched before I'm ready to make any claims related to ditching the springs entirely, including actually removing them and testing whether it will be reliable. But that's a ways off, at the very least not until I have some spare seals on hand, and have determined that a catastrophic failure will not result in the bike being rendered unrideable (IE> with the forks completely compressed the frame hits the ground) or wrecking. Looking for an elastomeric bumper that will fit inside the fork to at least prevent damage to hard parts and make it capable of limping home if the seals were to fail...might even resort to using valve springs held in place by lengths of hydraulic tubing. I dunno, we'll see where things lead me.

Today marks more than 48 hours of the forks being pressurized (I think. I'll have to double check.). Still at 30 PSI still no leaks after two full tanks of riding on them deliberately choosing rough roads to really give the suspension a workout. Very hard on the rump, even at the lowest preload on the rear the back's ride is to stiff. The front is still awesome. I've discovered riding off a low curb the front makes the transition much more smoothly than stock, the rear still sucks. A tiny bump VS a big thump.

I have pushed the front to 80PSI but wouldn't ride it that way, even putting all of my 260lbs on the front end the forks do not move. This of course leads me to believe it might only take 45 or 50 PSI to support the front end without the springs.....Again much more homework to do before trying it.

More status updates to follow. Any issues will be reported honestly and as accurately as possible. Would be pretty ****ing stupid to claim no problems if it turns out there are, after all if someone else tries it and horrible things happen....Well it wouldn't be good for all involved.
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post #12 of 54 (permalink) Old 10-03-2013, 10:39 AM Thread Starter
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A correction to the above post, today at 2:30 will be 48 hours of having the forks pressurized to 30PSI, so it's not more than 48 yet.

The clock started Oct/01/13 @ 2:30PM.

EDIT: 11am Day 3, Still no issues to report, still holding, still rides nice, still no leaks. Yeah, I know it won't officially be 72 hours till 2:30PM (3.5 hours from now), but I have errands to run.

EDIT: 3:30pm Day 4, and all is well. Still no leaks or unusual behavior.

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post #13 of 54 (permalink) Old 10-06-2013, 03:25 PM Thread Starter
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Oct 6, 3:30pm Still no issues, still holding pressure, still no leaks, still rides well.

On my fourth tank since upgrading, and thanx to unbelievable weather for October will be on my fifth by monday.

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post #14 of 54 (permalink) Old 10-08-2013, 07:04 PM Thread Starter
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Oct. 8, 7PM- Still rides nice still no leaks of any sort at 30 P/SI. Seriously thinking of removing the springs entirely and testing how much pressure is required to run strictly on air pressure. Still wagering it only needs about 40 or 50 P/SI for the front to ride like it does with the spring in. Worst comes to worst I limp home with no front suspension or running the compressor as needed...not the happiest thought for a long road trip, but I won't be taking any any time soon, maybe a short ride into the hills for the fall colors....nothing more than 90 miles either way, maybe 250 or so round trip.
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post #15 of 54 (permalink) Old 10-08-2013, 07:32 PM
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On my Honda GL500 Silverwing the front shocks have springs with air pressure adjustment recommended pressure is 11-17 PSI.
With Rear shock adjustment range 0-70 PSI.

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post #16 of 54 (permalink) Old 10-08-2013, 08:23 PM
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Quote:
Originally Posted by dfinitlydisturbd View Post
Oct. 8, 7PM- Still rides nice still no leaks of any sort at 30 P/SI. Seriously thinking of removing the springs entirely and testing how much pressure is required to run strictly on air pressure. Still wagering it only needs about 40 or 50 P/SI for the front to ride like it does with the spring in. Worst comes to worst I limp home with no front suspension or running the compressor as needed...not the happiest thought for a long road trip, but I won't be taking any any time soon, maybe a short ride into the hills for the fall colors....nothing more than 90 miles either way, maybe 250 or so round trip.
i would think this is a bad idea. for the fact "IF" it does fail there will be nothing there for it to fall on and could be a very dangerous situation. i would assume that they would not fail at once but if they did at same time of a serious breaking situation... what then? that would probably be the time they would fail, when you needed the suspension to work at its best. i love the idea as additional support for the weak suspension we have but i find it hard to believe the old Kawasaki (i think that was the bike i had with air assisted forks) didnt have any springs in there at all. i would hate to hear anyone getting hurt trying something like this. only safe test would be on some kind of a suspension machine that put the bike under extreme conditions as it was stationary. please dont put your self in any dangerous situation that we have to send you mail hoping you heal up quickly.

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post #17 of 54 (permalink) Old 10-09-2013, 07:54 PM Thread Starter
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That is definitely a concern and a matter not to be taken lightly. I'm not at all eager to have my second major accident. But, I'm nearly convinced that if they were to fail it would be a relatively slow failure. Still haven't found a good schematic for our forks, the key to determining if they would even fail at all lies in how they are built and sealed. If it's an "O" ring or two and a dust seal like I think it is, pressures in excess of 100 P/SI (higher if the tolerance between slider and tube are tight enough) can be reasonably expected to be held back safely as long as the seals and surfaces are not allowed to get dry.

Still holding at 30 P/SI, still rides awesome.
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post #18 of 54 (permalink) Old 10-09-2013, 10:31 PM Thread Starter
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Well ladies and germs, here's the deal (and oh I'm ever so happy). Best exploded images and diagrams say.......Big f'n seal, "O" ring type, clippy thingy, and crud seal...this is great f'n news for your's truly and anyone else dreamin of air ride. I see exactly one weak spot, the clippy thingy. BUT it already holds back the forces of the rebounding fork as well as the pressure from the spring when the bike's on a lift. Simple fix, make or obtain a heavier snap ring to replace the simple wire spring type clippy thingy. By design it is practically impossible to blow out the seal in a spectacular "OH F***!!!!!" manner. With an improved retaining clip it goes to totally impossible. The fork tube and slider are heavy enough as-is to hold back 200 P/SI at least without failing. By thickness I'd estimate failure pressure to be at least 300 P/SI for the alloy slider and closer to 500 P/SI for the tube. (for about the same thickness pressure tanks, air and hydraulic pistons hold back up to 1000 P/SI before approaching failure ratings)


Edit: screw making a snap ring didn't realize just how wide a variety there is of them...easier and cheaper to buy two of them.

Last edited by dfinitlydisturbd; 10-09-2013 at 10:53 PM.
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post #19 of 54 (permalink) Old 10-09-2013, 10:50 PM
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Quote:
Originally Posted by Fatlenny View Post
i would think this is a bad idea. for the fact "IF" it does fail there will be nothing there for it to fall on and could be a very dangerous situation. i would assume that they would not fail at once but if they did at same time of a serious breaking situation... what then? that would probably be the time they would fail, when you needed the suspension to work at its best. i love the idea as additional support for the weak suspension we have but i find it hard to believe the old Kawasaki (i think that was the bike i had with air assisted forks) didnt have any springs in there at all. i would hate to hear anyone getting hurt trying something like this. only safe test would be on some kind of a suspension machine that put the bike under extreme conditions as it was stationary. please dont put your self in any dangerous situation that we have to send you mail hoping you heal up quickly.
I second that. Making suspension components do what they are not designed to do is just a bad idea.

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post #20 of 54 (permalink) Old 10-10-2013, 09:29 AM
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I'll have to disagree. I've been re-configuring components for decades. Very few one-off racing conversions use entirely "stock" parts. Reconfiguring components is fine and dandy if done with the limitations of the materials and design in mind. And a consideration of what the mod may do to lifespan and safety.

Certainly adding 20 psi air pressure is a minimal thing. 200 psi takes more consideration, of course.

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