Max size hole that can be cut into end of airspring (firestone 2m2a)?

[loquax]

Hi,
I'm trying to design a spring/damping system using a modified firestone 2m2a (little fella) airspring, hooked up to air reservoirs. I need to fill the airspring with liquid and let the liquid act as a piston between the airspring and the actual air reservoirs, so the air-springiness is still there, it just isn't in the spring itself. To get the liquid flowing freely I need a bigger hole in the end of the spring than that provided (its about 2mmdia, I want 10-15mm dia.) I want to drill out this hole but the guy at Firestone reckons that might reduce the rigidity of the plastic endcap so much it would crumple under the force of the clamping ring and ruin the seal. Unfortunately, he doesn't know how big a hole it needs to be before the seal is useless. Has anyone done this and found out already?

Thanks

 

[loquax]

just so you know - we've cut out a hole somewhere between 10mm and 15mm. it hasn't crumpled yet, and so far as we can tell the seal has not gone bung. more testing to do yet tho. L

 

[BillyShope]

Glad to hear someone's playing with the air springs. As you probably are aware, a British manufacturer has done something similar to that which you've described.

I have a question, though: Why didn't you simply partially fill each bag with liquid (antifreeze?)? I think I've just answered my own question. I'm not familiar with the models, but it sounds like the bags you're using are not large enough to suspend the car without the external air reservoir. But, if you started with the larger bag, it would seem much simpler to partially fill with liquid. I've often thought such a trick would work quite well with a circle track car. With, perhaps, an interconnection between right front and left rear bags and a positive displacement pump in the middle. Or, this same plumbing arrangement could be used at the front of a drag car. (By using a higher rate spring at the right front than at the left, dynamic cancellation of the driveshaft torque can be realized.)

Let us know how your project comes out.

 

[loquax]

yeah the 2m2a is pretty tiny, the bag bit is about 50mm high. i don't think they're suitable for running actual automotive suspension, probably a bit small. we're just trialling the idea at the moment, running at way below operating pressure so we don't bust the spring or the pipes we've stuck on there, but we think we'd be able to scale up the idea to fit larger stuff like cars if it works in small. we'll be running it up to higher pressure later this week or next, so we'll see if the drilling out has had any effect!

What is the british company modifying air springs you mention? i can find a lot about range rover suspension but i'm not sure that's what you mean...

 

[BillyShope]

This car is no longer in production. It was original equipment, not a modification. Didn't save the email from a friend with whom I was discussing the subject. Sorry. A "Google" search might turn it up. It was a Hydro-Something (Hydro-Static?) suspension.

 

[patprimmer]

Was it the Hydroelastic system on later mini's, Morris 1100's and Austin 1800's

Regards
pat

 

[EricFahlgren]

Pat,

I don't know how you define later, but back in the '70s I had '65 and '67 Mini Cooper S 1275s that both had the "wet" suspension. It was really easy to change the right height by just pumping in or releasing antifreeze from the two Schrader valves below the rear pan.

These cars had no separate dampers, just the rubber springs and hydro system. They were wired in two circuits, LF to RR and RF to LR, I believe to reduce roll and pitch on bumps.

Eric

 

[patprimmer]

By late, I meant 2nd series, first series having rubber cones (more like rocks than rubber if you ever drove one)

They were connected front to back but not side to side. This gave very low pitch resistance, but good roll resistance.

I recently built a boggie trailer for my veteran car useing the 1800 rears, but due to their age they burst under the load, and I am considering my options for stronger bags or springs that might fit the space.

Regards
pat