Ride control of bus & RV pneumatic air bag suspension.

by Chet
(Bangor, PA USA)

I have been intrigued by the claims of this system. See:

http://hendersonslineup.com/uncategorized/supersteer-motion-control-unit/

To me, it looks like an application of the control principal you describe here:

http://searchwarp.com/swa78890.htm

especially since they say you feel the first bump and subsequent bumps are dampened. To me this says fast exhaust of the airbag and slow refill. While this action might improve the ride, the response of the ride height control must surely suffer.

Since their illustration looks like a common push to seal check valve, I'm having a little trouble figuring out what's happening. Is there some kind of two way valve that I'm not familiar with used here? I wonder if you could enlighten me.

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Bill answers...

Hi Chet...

Interesting reading, thanks.

Not being an RV'er, I've never experienced the problems that HendersonsLineup purports to resolve.

Air suspension works based on the principle that air is compressible. If you have an air bag full of compressed air at "X" pressure, and that bag is sealed, then as you apply pressure to the air bag the internal pressure increases, and as external pressure is removed, the increased air pressure inside the bag returns the air bag to it's original shape.

An air spring for a big RV or bus will have some sort of venting device I would expect, as the air needs to get out in the event that the air bag is seriously deflected by a load from the wheels moving over curbs etc.

A pressure sensor will then alert the on board compressor to re-inflate the air bag to correct pressure once the overload compressing the air bag is removed.

This is surmise on my part, as I have never worked on an air suspension for any vehicle.

What the product appears to do is throttle the egress of air from the bag is it is deflected by load. As you surmise, it's likely a device that throttles the air out of the air bag, and allows full flow inrush after the load on the air bag is gone. Similar, as you point out, to the "cylinder flow control" I wrote about in the article you site.

But I'm not sure. Vehicle suspension is an area best left to experts.

I'm also curious about their ad claim that the product is "Designed specifically to help air-suspended coaches — especially diesels." I have no idea why the motive power of an RV or bus would have an affect on suspension of the vehicle.

Nice hearing from you. Wish I could comment on the product further.

Cheers,

Bill