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Author Topic: Wheel Wells & Air Beams  (Read 2710 times)
DavidInWilmNC
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1978 MC-8 as I bought it May 2005




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« on: November 04, 2006, 09:10:21 PM »

I removed part of the floor in my MC-8 today.  I've heard horror stories and seen pictures of rusted-out air beams and wheel wells.  Mine don't seem to be in really bad shape, fortunately.  I poked and scraped the air beams and they seem really solid; I'll likely paint them with a Por15 type of paint to prevent any future rust.

I did find a bit of wet fiberglass insulation in the front of the air beam area.  I imgaine it got wet coming home from Timmonsville in the rain.  I'm really not sure how to keep this area from leaking.  If there is some sort of sealer I could pour in the area, this would probably work well.  It could get down into the small gaps and cracks.  What have others done to waterproof this area?

Also, what's the easiest way to remove the seat tracks?  I'd like to keep from destroying them, if possible.  I've got a use for them.  Thanks for any ideas or suggestions.  Here are two pics I took of the area.

David
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DavidInWilmNC
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« Reply #1 on: November 04, 2006, 09:12:21 PM »

Here's the second pic.
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gumpy
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« Reply #2 on: November 05, 2006, 06:11:43 AM »

They don't look too bad. Would be nice if you could sandblast them prior to painting. For sealing the leaks, you can probably use polyurethane caulk. You'll want to clean up the outside seams and recaulk there, and then recoat with wheel well undercoating.

For the seat rails, there's a very brief description and photos of my removal at http://www.gumpydog.com/bus/MC9_WIP/Structural/Floor_Removal/floor_removal.htm. What it doesn't say is that if you take a think chisel and wedge in under the rail, the weld will "pop" as you cut through it and helps prevent cutting too deep. Move the chisel as you continue along the rail with each weld.

craig
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Craig Shepard
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rayshound
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« Reply #3 on: November 05, 2006, 12:11:16 PM »

I had sand blasted my beams inside where your pictures show and also in the wheel wells, I also had removed the rearend for other reasons and it was a good time to blast that side also. Cleaning with marine clean first than sanding should work well. I had also used the por-15 I followed all the directions, Marine clean, metal ready & por-15, It came out nice, hard as a rock. I just purchased this week off of E-bay some floatation foam. This is a pour type. You mix a and b stir and dump it. It is a closed cell foam used for marine floation. I'm getting ready to pour and then install new plywood. It's easy to find on E-bay just search for pour foam. This should seal everything in the air beam area that you show. I  feel this would be better than the house type insulation originally used.
 on the seat rails Gumpy has a good web site to go to on this. I did the same, wedge between the rail and the floor metal close to a weld than use a cutoff wheel to cut the tack weld and it pops, than go to the next. Ray
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DavidInWilmNC
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« Reply #4 on: November 05, 2006, 05:54:00 PM »

Thanks for the suggestions, guys.  Craig, I should have known to check your website before even asking this!  I think you've covered just about every stage I'll have to deal with on your site.  Ray, that foam sounds good.  That's kinda what I was thinking to do. 

David
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BJ
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« Reply #5 on: November 05, 2006, 09:29:56 PM »

Air beams after a certain age leak and it is best to just plate the air bags. You can weld them and seal them all kinds of ways but in the end they will leak. It was a good idea that didn't work.  Just cover the seat rails with plywood and forget them. I'm sure that there are those out there that don't agree but you don't see air beams on anything after the 9's.
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DavidInWilmNC
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« Reply #6 on: November 07, 2006, 03:09:37 AM »

Air beams after a certain age leak and it is best to just plate the air bags. You can weld them and seal them all kinds of ways but in the end they will leak. It was a good idea that didn't work.  Just cover the seat rails with plywood and forget them. I'm sure that there are those out there that don't agree but you don't see air beams on anything after the 9's.

I'm sure that, in general, air beams lieak.  Mine will now keep the bus up for over three weeks, which seems pretty good to me.  I'm pulling up the floor to also run HVAC ducts, so I'm going to pretty much want to hot have to work around the rails.  Thanks for the suggestions, though.

David
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rayshound
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« Reply #7 on: November 07, 2006, 10:22:12 AM »

Just as a test, I had unhooked my level valves and installed a needle valve a guage and a shrader valve to add air. This was just a "hydro test" to see how good the beams were. This was after the sand blasting, painting etc. I used a large scale calibration gauge. In over 30 days it did not drop anything I could read on the gauge which I had valved in with the needle valve to the airbeams. That is saying alot for the beams with the air bags being dry rot but not leaking at 65 psig.  I have purchased goodyear air bags for front,rear & tag. I also bought new level valves to install. Ray
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littlehouse
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« Reply #8 on: November 07, 2006, 11:41:51 AM »

I know this is kind of silly. But what is function and reason for the air beams.

Ray
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« Reply #9 on: November 07, 2006, 11:45:17 AM »

Air beams after a certain age leak and it is best to just plate the air bags. You can weld them and seal them all kinds of ways but in the end they will leak. It was a good idea that didn't work. Just cover the seat rails with plywood and forget them. I'm sure that there are those out there that don't agree but you don't see air beams on anything after the 9's.

FWIW, later '9s don't have airbeams either.  My 87 '9 has "rolling lobe" air bags.  Whatever they are called, they don't have airbeams.   TTBOMK, '84 was the last year for MC9 airbeams.  Believe new suspension concept started in '85 with the 102A3, MC9, and later 96A3.  
David, if it was my money (and it ain't) I'd be plating the airbeams, if it becomes necessary to work on them.   Wouldn't as long as they'll hold air for 3 weeks.  That's remarkable!
Cheers, JR


  
 

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JR Lynch , Charlotte, NC
87 MC9, 6V92TA DDEC, HT748R ATEC

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« Reply #10 on: November 07, 2006, 11:50:12 AM »

I know this is kind of silly. But what is function and reason for the air beams.
Ray

Larger air volume, smoother ride?  I've heard that air beams systems ride better than the later style air bags.   
That's my guess.
JR
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JR Lynch , Charlotte, NC
87 MC9, 6V92TA DDEC, HT748R ATEC

"Every government interference in the economy consists of giving an unearned benefit, extorted by force, to some men at the expense of others.”

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kyle4501
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« Reply #11 on: November 08, 2006, 09:50:19 AM »

The air bags are simply an air spring.
Higher air pressure = higher spring rate.
Higher spring rate = stiffer ride

As the bag compresses (when hitting a bump), the volume decreases & the pressure goes up.

By having a large volume of air in the air beams, the increase in pressure is minimized resulting in a smoother ride.

I suspect that in reality, there are only a few sensitive a$$holes  Grin that can tell the difference.

My Scenicruiser has all 12 airbags plated & she rides so smooth that it's amazing!

My guess is that when GM came out with them on the 4104, the roads weren't very good & every little bit helped. Also the airbags may last longer with lower pressure spikes from bumps.

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buswarrior
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« Reply #12 on: November 08, 2006, 06:09:41 PM »

Fascinating history:

GM used air beams in the "Old Look" Transits, and gave them up for the "New Look" transits when they came out in the late 50's. The air beams were also abandonned in the highway coaches after the 4104.

MCI stubbornly used them up to the late 80's as noted previously.

They eventually rust through in most commercial operating environments, causing air leaks and need for resources to fix or bypass.

If you have intact beams, go for it!  If yours have lost integrity, plate 'em, and if you need bags, go for the rolling lobe retrofits.

Dave, you've got one really nice undersides there! I'm afraid to uncover mine! I fear mine will be the opposite of yours in condition.

I shall stay in denial until the return from Arcadia!

happy coaching!
buswarrior



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Beatenbo
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« Reply #13 on: November 08, 2006, 06:21:32 PM »

All the talk about more air smoother ride I've heard plating makes stiffer. My experience...I had a 85 96A3 with the old style bags and beams and I plated one side rear and it never rode the same. I would say if you plate one do both sides to equalize the amount of air. I think the bag or air spring responds  different to the volume of air. I would not want another bus with air beams from the problems I had with them. I even blew out an inside rear tire and it dented and split an air beam.  I've seen some converted to the newer rolliing. lobe type. My C3 handles entiirely different from my A3.
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NCbob
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« Reply #14 on: November 09, 2006, 03:28:35 PM »

FWIW, and I'm not really knowledgeable about the topic...only what I see and feel on our bus.  Our MC5A has  Air Beams, which give us a great ride.  I see them as buffers between the front and rear bags.  While we don't think of it as such, in this application air is a solid, because it's compressed.  My bus has a single rear axle.  When either axle encounters an irregularity in the road the wheel moves in the opposite direction.

When moving in a forward direction and I hit a 'bump' or an expansion joint in the pavement...my guess is that the forces on the front axle move backwards (for every action there is an equal and opposite reaction).  At this split second the VOLUME of air is moved toward the front of the air beam to cushion the impact.  Pressure might not change...but there IS air movement.

So, my overview is that using the full air beam, as the Engineers designed it, should result in a smoother ride than in the case of blocking them off.

Opinions are not only solicited but welcome......

NCbob
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Stan
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« Reply #15 on: November 09, 2006, 06:10:09 PM »

NCBob: Your MC5A is approaching 50 years old and if the air beams are still good it shoots down the theory that all air beams rust and leak.

I don't agree with your theory on axle movement causing air movement in the bag. The axle should not rotate unless the radius rod bushings are worn. The better ride is simply a matter of having a larger volume of air in the system than if the beams are sealed off.
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kyle4501
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« Reply #16 on: November 10, 2006, 10:48:10 AM »

Hey Stan, one of my PD4501's is a 1956 & the air beams still hold air. I can find no significant rust anywhere in the structure. It was a west coast bus.

My 1954 has rust holes in the air beams large enough to stick a couple of fingers in. Yes those bags have block-off plates. this was an Eastern & north central bus.
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« Reply #17 on: November 10, 2006, 02:27:52 PM »

Kyle4501 My MC7 Combo had a 4501 rear suspension and also had zero rust in the air beams. There are two factors that save the air beams. The bus must be initially constructed in such a way that water does not get between the floor and the top of the beam. If it stays dry on top, then it is the reponsibility of the owner to keep the mud, salt and other crud of the lower part of the beam by regular washing.
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kyle4501
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« Reply #18 on: November 10, 2006, 05:25:35 PM »

I think the salted roads did mine in. The holes are on the side about middle ways up. Odd place if you ask me.

Rides smooth as glass even with blockoff plates. Grin
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