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1958 Mack B Model Upgrading to Spring Brake Chambers


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Evening everyone.  I bought a 1958 B Model a few years back and unfortunately it has been sitting outside waiting on a new engine.  It now has a new engine to replace the tired old one getting rebuilt at the local machine shop.  I am now moving onto a serious project and that is the installation of spring brake chambers.  Does anyone have a good how to guide on how they upgraded their B model to spring packs to get me started on this?  I have used the service manuals and done a fair amount of reading on the subject and am getting ready to purchase the pieces to tackle this project.  Any input is appreciated!  Thanks All!  Hope everyone is having a good Memorial Day.

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I asked this same question a while back and mostly heard crickets for any type of response. I'll tell you what I have found out and learned thus far on the subject. My truck is a 1960 B81 that has S cam brakes with manual slack adjusters, much like a modern truck, however, it has rotochambers of some variety (I think type 20 or type 30) to actuate the slack adjusters. The brackets attached to the axle housing the rotochambers bolt to are extremely close to the tire/wheel assembly. The center to center measurement of the bracket hole centers are the same as any modern mounting bracket and will accept any modern brake chamber, however, the diameter of the new compound brake chambers don't allow them to be installed without interference with the wheel. Modern chambers are also much too long, causing interference with the wheel at the back of the spring chamber as well. I first tried a 30/30....not even close. I then tried a 24/24 and it fit, however, it was so close to the wheel you may have been able to fit a sheet of paper between the two. I was not comfortable with this amount of clearance. The only other option I have found but not tested yet are Haldex I Series Maxibrake chambers, specifically part number MA15770. They look to be esentially a type 20 rotochamber with a small little spring brake chamber on the back that is smaller in diameter than the service chamber so clearance should not be an issue. The only downside to these (assuming they fit as planned) is the cost. I priced two of these out a few months ago and my parts place wanted somewhere North of $400.00 apiece for them, and I could not return them if they did not work. I just could not bring myself to spend the money on them at them time with the risk of not being able to return them. I will probably bite the bullet and buy one to test and then buy a second one if it works out. I figure for a show truck that only ever bobtails one axle with spring brakes should be sufficient. Below are two pictures of my current stock setup and you can see how close the service chambers are to the wheel.

brake 1.jpg

brake 2.jpg

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I know in Australia there was a bracket to take the Maxi chamber further away from the wheel as a lot of NR  Mack back ends got fitted to single drive trucks in the 60's and 70's 

Apparently I have been told on here that is wrong so I stand to be corrected 

However I clearly recall Gleemans running the adds for a NR back end and the associated brackets to do the conversion

The bracket wasn't anything special and I reckon Gleemans just made them to suit

If my memory serves me correct which it probably doesn't it was a big thick piece of flat bar with 4 holes to shift the maxi chamber a inch ir so inboard

Maybe needed to change the S cams for longer ones to shift the slack adjuster as well 

Gleemans were the Mack people out side of Mack Australia for many many years and sold everything Mack, new, second hand or rebuilt 

 

Paul

 

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Just think out loud here

U undo the backin plate bolts and rotate it a bolt hole or more

Jack up axle to hit the axle stops

then checking that the "S' cam wont  interfere with diff housing

speacilly when U try and replace slack adjusters

cya

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There are threads on this scenario from the earlier days of the site. Basically a PP valve in the dash, (PP1, or PP7) and an R12 relay valve supplying the spring brakes equipped axle(s) along with associated air line routing. Not hard to do but you will need to space those rear chambers outward from the drive tires. I used to do this with 1/2" plate mounting to the original chamber mounts via grade 8 bolts and the new spring brake chambers mounting to the plate. You will require offset slack adjusters which are readily available. I always upped the size from the type 20 rotochambers to type 24/24 spring brake chambers myself offsetting the mountings by the distance of the slack adjuster offset. This size provided adequate stopping power for a tandem end dump truck and is physically smaller than the type 30/30 chambers. 1/2" plate was stiff enough to not bend under full brake application pressure under normal conditions. Never had problems with DOT on the matter but had heard of folks doing this with 1/4" plate and having problems.

If you have someone with a steady hand a torch does a good job or these days a plasma cutter. I made a pattern and probably still have it someplace..... 

 

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Dog.jpg.487f03da076af0150d2376dbd16843ed.jpgPlodding along with no job nor practical application for my existence, but still trying to fix what's broke.

 

 

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1 hour ago, Rob said:

There are threads on this scenario from the earlier days of the site. Basically a PP valve in the dash, (PP1, or PP7) and an R12 relay valve supplying the spring brakes equipped axle(s) along with associated air line routing. Not hard to do but you will need to space those rear chambers outward from the drive tires. I used to do this with 1/2" plate mounting to the original chamber mounts via grade 8 bolts and the new spring brake chambers mounting to the plate. You will require offset slack adjusters which are readily available. I always upped the size from the type 20 rotochambers to type 24/24 spring brake chambers myself offsetting the mountings by the distance of the slack adjuster offset. This size provided adequate stopping power for a tandem end dump truck and is physically smaller than the type 30/30 chambers. 1/2" plate was stiff enough to not bend under full brake application pressure under normal conditions. Never had problems with DOT on the matter but had heard of folks doing this with 1/4" plate and having problems.

If you have someone with a steady hand a torch does a good job or these days a plasma cutter. I made a pattern and probably still have it someplace..... 

 

Rob,

I never realized there was offset slack adjusters available. Do you happen to have a picture of what the final result looks like with the fabricated 1/2" mounting plate? I would be interested to see what it all looks like. As far as I'm concerned the air plumbing portion of this job is the easy part. Thanks in advance.

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Posted (edited)
15 hours ago, 58GreenMackB said:

I was more looking for guidance on how you plumbed the air system to accept the spring brakes.

Adding the release circuit, like Rob said, isn't too difficult.  It is mostly independent of the service brake circuit.  Really just have to get air into and out of the "release" chamber of the parking brake.  The service brake side is pretty much the same.

Of course, it is a good idea to set up the parking (spring) brake release valve with an anti-compounding setup.  There are several different ways to do this.  There are a variety of valves with anti-compounding features built in.

My old R had it plumbed into the parking brake valve itself.  This was a VERY simple system.  The anti-compounding valve was not much different than a regular valve, except that the exhaust side of the parking brake valve was effectively attached to the service brake line.  This dumped the parking brake air through the treadle valve exhaust when the spring brakes were applied.

If the foot valve was applied with the parking brakes set, air pressurized the service brakes and at the same time equally pressurized the release chamber of the parking brake.  This essentially cancelled out the additional pressure being applied by the service brakes.  Kept you from applying full service brakes and full spring brakes at the same time.

Once the parking brake valve was released, and pressurized air was ported to the release side of the spring brakes, the exhaust side of the valve was blocked off, and the service brakes worked normally.  Pretty sure this was a PP-2 valve.  Might have even been a regular PP-1 with the exhaust port tied to the service brakes.  Just cannot remember.  Sorry!  But, I think it was the PP-2.

But, like I said, Bendix has a variety of valves that will allow you to do this in different ways (using modulating valves, relay valves, etc.).

The schematic is a little hard to read.  But, you can make out the "exhaust" line from the "auxiliary valve" going to the service brake line.

PP-2.pdf PP-1.pdf

Push-Pull Valves.pdf

DSCN0549.JPG

Edited by doubleclutchinweasel
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"Eagles may soar, but weasels don't get sucked into jet engines."

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Posted (edited)

I used the schematic in this Bendix brake handbook to help with plumbing the system. I'm using Bendix valves because they're very common and cheap. dcweasel is correct about the anti-compounding, especially if you have aluminum spiders like mine. I used a QR-1C quick release valve on my rear axle to achieve the anti-compounding.

For my spring brakes, I used Haldex GC2024 which have a #20 service side and a #24 spring side. They are $92.00 with free shipping from Finditparts.com. They are adequate for a bobtail hobby truck, not sure about hauling freight with them. I rotated my spiders one bolt hole to get them away from the frame rail, but they are only about 3/4" away from the 10:00-20 rims (you'd have more clearance if you went with tubeless or 10:00-22).

Chamber.jpg

1837032478_BendixAirBrakeHandbook2002.pdf

Edited by h67st
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A cupla pix of our Mack 'R' model

I worked out why Mack had the lever type parking brake control .... was use to on/off button like on most trucks

I was out in our mack TiltTray truck picking up a 12 t load on the Mack 8x4

cumin up the steep track back on to road and had to stop to let traffic pass

I had a little trouble do n a smooth take of

Then relized the mack parking brake lever was there to gradually release the brakes = no worries

cya

 

P1050790x.JPG

P1050791x.JPG

P1050792x.JPG

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On 6/3/2021 at 7:32 AM, 67RModel said:

Rob,

I never realized there was offset slack adjusters available. Do you happen to have a picture of what the final result looks like with the fabricated 1/2" mounting plate? I would be interested to see what it all looks like. As far as I'm concerned the air plumbing portion of this job is the easy part. Thanks in advance.

I probably do with stuck together Polaroid photos from all those years ago when the basement flooded. Basically a modified circular flame cut plate with one side being more of an ellipse than rounded. This elliptical side was to clear the inner wheel and dust shield yet yield adequate strength to not flex. There were then five holes drilled into the plate, (two mounting the plate to the spider, two mounting the brake chamber to the plate) with a larger center hole where the brake chamber pushrod penetrated. IIRC the plate mounting holes were 5/8", and the pushrod hole was 1.25" allowing for a rubber dust boot to be fitted. I always rounded the edges of the plate to not cut things like air lines, fingers, etc. Here is a single example of an offset slack. I believe the offset was 5/8" to allow you to retain your original "S" cams. https://www.ebay.com/itm/293728331804?hash=item446392a81c:g:sHgAAOSwitZgF7FK

Here is a photo of what they would look like:

image.jpeg.ff8ea3f986a776250ea5c00cfacdd2ca.jpeg

I have a couple of B series trucks I plan to modify so may get you an example sometime shortly.

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Dog.jpg.487f03da076af0150d2376dbd16843ed.jpgPlodding along with no job nor practical application for my existence, but still trying to fix what's broke.

 

 

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On 6/3/2021 at 12:30 PM, h67st said:

I used the schematic in this Bendix brake handbook to help with plumbing the system. I'm using Bendix valves because they're very common and cheap. dcweasel is correct about the anti-compounding, especially if you have aluminum spiders like mine. I used a QR-1C quick release valve on my rear axle to achieve the anti-compounding.

For my spring brakes, I used Haldex GC2024 which have a #20 service side and a #24 spring side. They are $92.00 with free shipping from Finditparts.com. They are adequate for a bobtail hobby truck, not sure about hauling freight with them. I rotated my spiders one bolt hole to get them away from the frame rail, but they are only about 3/4" away from the 10:00-20 rims (you'd have more clearance if you went with tubeless or 10:00-22).

Chamber.jpg

1837032478_BendixAirBrakeHandbook2002.pdf 5.17 MB · 1 download

Only trouble I've seen using that setup is the heat of the brakes makes for a shorter lifespan of the rubber parts of the brake chamber which really wouldn't be a problem on a hobby or casual use truck. I did try that setup as it was easy on a tandem end dump; but it didn't hold up the best only because of the brake drum heat soaking they took.

Dog.jpg.487f03da076af0150d2376dbd16843ed.jpgPlodding along with no job nor practical application for my existence, but still trying to fix what's broke.

 

 

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That’s right Swishy, also you can apply the brakes gently if the foot or hand piece malfunctions.  My CH has a push pull button so it’s on or off only, they have definitely gone backwards. 

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  • 2 weeks later...

Swishy, that flip lever valve you showed is made by Bendix, they call it a TC-4 (part number 282368 or 282382) and they say it's for controlling the spring brakes. I've got a question...this valve was in one of my trucks, I didn't chase the air lines to see what it does. Can someone tell me what it's for?

133.JPG

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h67st

m80

Me thinks th@ valve is the early V: of the yellow push/pull of today

we had m on the KW from the mid 60's

Swithes air off to the trailer so U can unhook

it also  a proporsion n valve  60/40

I strongly disagree with NOT FOR PARKING

if U don't have trailer brakes full on ( use trailer hand trolly lever with engine ideling 

U can have a truck run away wen loading on a hill

apb.jpg.19cfb392f61de78a1ca51c48ec8b6a99.jpg

 

3 dash valves front axle (dry road- Slippery Road) ...... Diff Lock.......... Trailer Control (Truck/Tractor protection valve)

 

cya

Edited by Swishy
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9 hours ago, h67st said:

Swishy, that flip lever valve you showed is made by Bendix, they call it a TC-4 (part number 282368 or 282382) and they say it's for controlling the spring brakes. I've got a question...this valve was in one of my trucks, I didn't chase the air lines to see what it does. Can someone tell me what it's for?

133.JPG

This is actually the old version of the red button.  If the trailer lines come loose, this valve trips automatically to protect the air supply in the tractor.  And, if you want to disconnect the trailer, you flip this valve first, and it separates the tractor and trailer air systems.  Like I said, the later stuff used a red push/pull valve to do the same thing.

"Eagles may soar, but weasels don't get sucked into jet engines."

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13 hours ago, doubleclutchinweasel said:

This is actually the old version of the red button.  If the trailer lines come loose, this valve trips automatically to protect the air supply in the tractor.  And, if you want to disconnect the trailer, you flip this valve first, and it separates the tractor and trailer air systems.  Like I said, the later stuff used a red push/pull valve to do the same thing.

So, if it sets the spring brakes, why does it say "not for parking"?

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I dont think it does put the spring brakes on as you think 

Many years ago, back in the early 80's (that actually only seems like yesterday in my head) trailers in Australia never had spring brake chambers, just brake chambers with no maxi spring brake on any axle 

So if you used this as the parking brake and walked away and the truck wasn't running as the air leaks out the brakes come off and the truck and trailer etc could easily roll away

We need to remember that way back when dinosaurs roamed the face of the earth there were no spring brake chambers at all on big trucks, there things called hand brakes and these were from a transmission brake (band or disc) to mechanical linkages 

Yeah Im been a bit silly here but youget the drift

Im gunna say the mid 50's onwards prime movers started getting spring brake chambers, totally open to correction here

If you as think back to when trailers had no maxi brakes the landing legs had wheels instead of feat, this was so that if you backed under and there was no air in the trailer and it rolled it didn't bend the landing legs 

Once maxi brakes came out we got feet on landing legs instead of wheels because if the air leaked out the brakes came on and the trailer wasn't going to move 

 

Paul

 

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I say if this joker had his trailer brakes on it may have prevented the runaway

 

Starting @ 3:25 - 4:07

There again look n back in hindsite if the crane driver hit reverse it may have brought the jalopy to a halt

WotSezU?

cya

 

 

 

 

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A lot of those had DD3 brake chambers on them.  They used reserve air to apply the parking brakes.  Then, they "wedged".

On most of those old ones, the yellow button applied whatever parking brakes they had (DD3 or spring) on both the truck and trailer.  The flipper was intended to be used when the trailer was disconnected.  If you flipped it manually, it would disconnect the air supply to the trailer.  This would set the parking brakes on the trailer.  I think they did not want you to use it in place of the yellow button, which set the parking brakes on BOTH the truck and trailer.

 

Again, it did more or less what the later red button did.  And, yes, it COULD be used for parking...but that was not its primary intended purpose.

 

Play with it and see what you get.

"Eagles may soar, but weasels don't get sucked into jet engines."

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