Ski Bum Truck V2.0, F450 Rough Road RV

[Alloy]

They are all the same other Than the frame itself. This was a PU originally.

Front axle rating is 6500lbs

Yes both sides are angled like that. The drivers side is actually offset a little more.

And on the King vs Fox, IMO they are very comparable. I went fox as the guy I got the best discussion with uses Fox.

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I'd have my welder out and be cutting the mounts to square things up....but that's just me who hate seeing things out out of alignment

Also going to talk to Timbren today to see if they have any suggestions for the front/back

 

[java]

I'd have my welder out and be cutting the mounts to square things up....but that's just me who hate seeing things out out of alignment

Also going to talk to Timbren today to see if they have any suggestions for the front/back

Found an old copy of the Firestone Engineering and Design guide. Lots of info..... Well over my head.

Misalignment is OK on these bags, as long as the "folded" section does not internally touch. The misalignment is pronounced in that pic as the axle is somewhat out of level compared to the truck.

If this helps anything @luthj Found the data for the bag. Looks like they are running it a little under designed height at 8" (design is 9"), but no idea what that does capacity/pressure wise as I am just over the weight rating at 80psi.

 

[luthj]

You should be able to get 80% of the travel out of those bags. Part of the issue is that being near the bags max weight, they will be more progressive. That may be why you can't use all the travel.

 

[java]

You should be able to get 80% of the travel out of those bags. Part of the issue is that being near the bags max weight, they will be more progressive. That may be why you can't use all the travel.

Thank you for all the help. Yes I am thinking I am just too close to maxing them out.... IE too much spring rate?

It should not be a frequency problem correct? It was suggested on another forum that adding anti freeze to reduce volume may help, but from my reading that will only increase the natural frequency.

 

[luthj]

Have you tried running at a lower pressure? Your ride height will be lower, but does the ride improve? Bags are kinda weird, cause they behave differently once they start to heat up. Trucks love em cause they act like shocks by damping axle motion.

Reducing bag volume with a liquid can make the spring rate lower, but I am not sure how that will affect the dynamic rate.

Some reading here.

Intro - AccuAir Suspension

Air Suspension Terminology Air Spring The rubber bladder assembly that replaces the metal coil, leaf, or torsion spring in a vehicle suspension system, often referred to as an Air Bag. D.O.T. is short for Department of Transportation. Certain fittings, tanks, and lines are D.O.T. approved and...

accuair.com

Q: Can I adjust the Spring Rate of my air springs along with the height?
A: Yes, but the Spring Rate will be directly connected with spring height. As you raise the air spring’s height, you will also be increasing the air pressure inside, thus increasing its Spring Rate. Unfortunately, this is opposite from what most of us would want for performance applications, (low and firm for handling, high and soft for mobility).

Another way to reduce the spring rate is to add an accumulator tank plumbed in parallel with the air spring (sometimes referred to as a “ping tank”).

 

[java]

Have you tried running at a lower pressure? Your ride height will be lower, but does the ride improve? Bags are kinda weird, cause they behave differently once they start to heat up. Trucks love em cause they act like shocks by damping axle motion.

Reducing bag volume with a liquid can make the spring rate lower, but I am not sure how that will affect the dynamic rate.

Some reading here.

Intro - AccuAir Suspension

Air Suspension Terminology Air Spring The rubber bladder assembly that replaces the metal coil, leaf, or torsion spring in a vehicle suspension system, often referred to as an Air Bag. D.O.T. is short for Department of Transportation. Certain fittings, tanks, and lines are D.O.T. approved and...

accuair.com

I have tried lower, (somewhat, and awhile back) and I did not notice much difference. I am worried much lower and I will begin to bottom on the bump stop. I only had another ~1.5" or so to go before hitting it. I will try dropping some pressure and see.

Thank you again. A ping tank was another suggestion. My issue is I have bags designed with a 1/4"NPT port. Even if I step up to 3/8 or 1/2" right from the fitting I am worried there is going to be a restriction that will make the tanks not so useful. Seeing as how air transfer would be slow. 1/4" would be ideal to run, but I think nearly useless.

 

[luthj]

Even with the 1/4" restriction, you would see benefit from a 3/8" line for the run. How much improvement I can't say.

 

[java]

Even with the 1/4" restriction, you would see benefit from a 3/8" line for the run. How much improvement I can't say.

Thank you again. I do appreciate you taking all the time to go thru this.

I am thinking I will put a T into the 1/4" line as close to the bag as possible. Then run 3/8" to a 1gal tank back under the box. Unfortunately it's going to be a long run, but no where else I can get the tanks I don't think.

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[Alloy]

At 80psi the bags will be like rock. Ideally the bags would hold the weight at 40psi.

Highway trucks/trailers run at 45-55psi. Fully loaded the airbags (Timbren STI) under my trailer come up to ride height at 40psi.

The 1/4" fitting will restrict allot of the flow. I'd do a few test runs with both bags connected to a 3gal-5gal ping tank and see what happens before spending the time to build something permanent.

 

[java]

At 80psi the bags will be like rock. Ideally the bags would hold the weight at 40psi.

Highway trucks/trailers run at 45-55psi. Fully loaded the airbags (Timbren STI) under my trailer come up to ride height at 40psi.

The 1/4" fitting will restrict allot of the flow. I'd do a few test runs with both bags connected to a 3gal-5gal ping tank and see what happens before spending the time to build something permanent.

Yeah much smaller bags then OTR trucks too.... But I'm just under 80psi.

Temp tank is about as hard as a permant one.... I have two 1gal tanks here.

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[Alloy]

What year model is your truck I'll see if my friend at FORD can determine what coils where made for the camper/plow options.

How much room is there around the airbags? Could you fit larger diameter bag in?

 

[java]

What year model is your truck I'll see if my friend at FORD can determine what coils where made for the camper/plow options.

How much room is there around the airbags? Could you fit larger diameter bag in?

It's a 2008, but I need lift coils.

It's the 14500 GVWR package originally. I have thr coils stashed somewhere... I can find the part number off them most likely.

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[java]

Well I think I may have found the oil leak.... Whats left of the Oring if there ever was one.... Nothing in the bore.

I didnt have one that felt quite "fat" enough.... Doubled up on one that felt ok and hope it works. I need the truck Thursday.... If I need to pop it again I know how it all goes together now.

All has to be done via feel/camera.... I can see up there!

McMaster order for ping tank fittings has been placed. I have two dead 1 gallon compressors to steal the tanks off of. Just need to figure out how and where mount them.

 

[java]

Bag data!!!

A little hard to read, But shows the curves and spring rates. spring rates @ 80psi 535, @100psi 658 (at 9")

 

[luthj]

Those curves show the carrying load at various pressures. They don't show the dynamic spring rate curve. That would be the real world cycling of the air spring after setting the volume/pressure at ride height.

Going from 9 to 7 inches the bag volume goes from from 280 to 210 cubic inches. The pressure increase would be P1*V1=P2*V2 280*80=P2*210 P2 =106psi So in 2 inches the force produced by the bag goes from 2600lbs (at 80 psi) to 3600lbs (110psi and 7"). The effective spring rate for those two inches is (3600-2600)/2 = 500lbs/in.

If you started at 11 inches, and compressed to 9 inches it would be as follwos.
3.6*80=P2*2.8, P2 = 102psi, 3400-2800bs = 600, 600/2=300lb/in

As you can see the spring rate is pretty progressive. The higher the vehicle sits at normal ride height, the more progressive/stiff it will be at max bump.