Not Enough Air In My "b"

[martinf]

Herb is correct. Those are heavy rears. You can tell by the type of trunion stand, and axle caps that are tapered. The axle shafts are actually two piece units that you can't see. I'd be interested to see the spring brake chamber mounting arrangement if you could post a photo of the area(s).

On the rear rear housing looking at the rear of the truck, just to the rt. side of centerline of the housing bowl, there is a number such as SWD58XXXX stamped, (the X's will be numbers) and these will be the suspension numbers. Anyone with a book can decode these for you.

I don't remember what year you said your truck was but the trunion stand shown is the same as the ones in my 63, and 64 year model B series trucks. These also have the piston type brake cans as Herb mentioned. Rotochambers actually have the rear of the can, (nearest the air inlet fitting) "necked" down about an inch total where the piston type do not. Wagner supplied most of the piston type, with combination of both Wagner, and Bendix-Westinghouse supplying the rotochambers. I've also seen a combination of both installed on the same truck however I doubt they were original to the truck in that fashion.

Rob

Alrighty,

Well, looking in a another Mack manual, I see a picture of the roto chambers and then mine, which they call power cylinders. If I'm not able to get new rubber sealing lips for the pistons, I'll be changing over to the diaphram air brake service chambers on the front rear axle. Don't know about the fit issue, though, because the 24's need 7 1/2" dia. and my power cylinders are a bit over 6" dia. and not much more room to spare. Any ideas about how to accomodate the larger diameter chambers?

And, if anybody's got the book handy, I'd appreciate a look-up for my axle ratings. The number on the housing is 1QFA5408P1. I'd imagine that they are 44,000's, though because HK Trucking identified them as such and, looking on my title, it shows gross weight of 44,000.

By the way, Rob, this truck is a 1965.

And, since you asked, I took a picture today of the rear spring cans.

thanks for the assistance, I'm learning lots of this site.

~martin

Edited March 24, 2010 by martinf

[Rob]

Alrighty,

Well, looking in a another Mack manual, I see a picture of the roto chambers and then mine, which they call power cylinders. If I'm not able to get new rubber sealing lips for the pistons, I'll be changing over to the diaphram air brake service chambers on the front rear axle. Don't know about the fit issue, though, because the 24's need 7 1/2" dia. and my power cylinders are a bit over 6" dia. and not much more room to spare. Any ideas about how to accomodate the larger diameter chambers?

And, if anybody's got the book handy, I'd appreciate a look-up for my axle ratings. The number on the housing is 1QFA5408P1. I'd imagine that they are 44,000's, though because HK Trucking identified them as such and, looking on my title, it shows gross weight of 44,000.

By the way, Rob, this truck is a 1965.

And, since you asked, I took a picture today of the rear spring cans.

thanks for the assistance, I'm learning lots of this site.

~martin

You have the power cylinders as you mention and you will have a tough time getting the parts but they can be had, expensively. I couldn't remember the proper name for them and referred to them as rotochambers also. Having the heavier rated suspension presents a challenge to retrofit for the larger diameter chambers needed. Type 24 spring brake service chambers are a slip fit on the lighter rated suspensions. The best, easiest, and safest way to accomplish this is to find a donor R model truck and strip both trucks to bare axle housings, then install the R model hardware on the B model. Before you go to all this trouble ensure the bolt spacing is the same on both trucks for the brake adapters. You may need to have a thickness adapter fabricated for spacing but it depends on brake parts installed. R model trucks spaced the brake chambers further inboard, and lower on the mountings than the B series did. Either way, you should probably look to upgrade the system. Parts aren't getting any more available for the old systems as they age.

I've not seen spring brake power cylinders since I was a kid. I didn't even remember them until your photo.

The numbers you posted are the actual axle housing. As mentioned earlier the suspension type starts out as SWD and a series of numbers. Yours being the heavier should be something like SWD58XXX. That series of trunion stand is very sturdy but did manage to get broken/cracked from time to time. It is cast steel and my 64 B61 has 3/8ths plate welded to the front and rear vertical legs on both sides. Must have seen some rough usage in it's service life.

Good luck.

Rob

[martinf]

You have the power cylinders as you mention and you will have a tough time getting the parts but they can be had, expensively.

I've not seen spring brake power cylinders since I was a kid. I didn't even remember them until your photo.

Good luck.

Rob

Just to give anyone who's interested an update...

I put in a new governer and that solved the lack of air problem. Wow. I've never had it build up so much pressure so quickly! And it fixed my other problems with the leaky power cylinders, too (at least for a while). When there was only 30 psi, the cylinders leaked bad, but with strong pressure they don't. Well, and also I cleaned then up and got the rust out and put a shot of 5W in there like the book said. I guess I probably wouldn't have had to even take them off and apart, if it wasn't for the low air pressure making them leaky and me getting worried about them, but I guess it's a good thing I did because they really needed some maintainence. It'll be a good thing if I can get a few more years out of them as I've learned here how difficult it will be to replace them or create a work around.

Thanks again,

~martin

[JD 5020]

Any luch finding the rears number? I too looked once and found the axle housing number but not the rear. Anyone have a picture of this number, I may have just over looked it.