17 replies to this topic

[doubleclutchinweasel]

Another of many projects...

I'm looking at the spring brakes on the rear of my '70 R600. They are an old-type spring brake, with no provision for a "caging" tool.

They are also a bit rough, and are on my list of goodies to replace...very soon.

But, the old air system uses 3 lines to the brake chamber; 1 for service brakes, 1 to release the spring brakes, and (apparently) 1 to override the spring brake in the event of main system air loss (via dash-mounted valve).

None of the current brake chambers I can find have 3 ports, instead having only 2. I am assuming these new chambers either did away with the emergency override, or the valving/relays are set up to deliver this emergency override through the normal spring-release port.

Anybody been there/done that?

I see that Bendix has some different service relay valves, and at least one of them has some type of provision to modulate the spring brakes through the foot valve in the event of main system air loss (R14, I believe it was). But, they don't go into great detail about it. I have emailed them, and asked for clarification, but I'm not going to hold my breath waiting on a response.

Thanks,
kent

[leversole]

Might have to post some pictures for us to see...never seen three brake lines to a brake chamber! Plus, you cannot "override" the spring brakes with no air!
Where does the "third line" go in, the service chamber (front) or the emergency chamber (rear).
This is a new one on me...

[doubleclutchinweasel]

Might have to post some pictures for us to see...never seen three brake lines to a brake chamber! Plus, you cannot "override" the spring brakes with no air!
Where does the "third line" go in, the service chamber (front) or the emergency chamber (rear).
This is a new one on me...

I'll get you some pics soon. It's weird! The service and parking brake hoses go into what appears to be the "wrong" end of the chamber. And. the 3rd hose goes into the top of it. Makes no sense.

I'll get pics...

[doubleclutchinweasel]

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Here's what they looked like...

I'm thinking this whole rear mess needs to be upgraded!

The small reserve air tank in these pictures, I assume, is an isolated air supply specifically to release the parking brakes to allow you to move the truck off the railroad tracks before the train comes!

[BC Mack]

the only three line brake chamber I've seen are Bendix DD3...
http://www.bendixvrc...documentID=2393
however, all I've ever seen them on are buses..
the third line is for a locking pin inside the actuator, to release you have to have full air and make a brake application as you move the park brake lever to 'release'...
if the truck was upgraded in the 60's or 70's then this is "possibly" what they are. They are more compact than regular "maxi's" and used in limited space applications.
not an expert but it's all I've got..!!!

BC Mack

[doubleclutchinweasel]

Looks like I can change this over to a "regular" spring brake cannister, and remove the emergency release mechanism. I am currently looking around to see what is available.

These cannisters are fairly small, and there isn't much room to go up to a larger size. As near as I can tell, the rears are only size 20 or 24s. I see that bendix makes a 20/24 and a 24/24, one of which might physically fit. To counteract the relatively small cans, they use a fairly long slack adjuster (7"). So, I probably need to stay with the same cylinder area.

It would help if I could find some numbers on the old parts! I'll keep looking.

More to come...

[j hancock]

I realize you want the numbers off the existing parts but here are some numbers that may help.

Maybe they could help in crossing to get what you need in new parts.

Slack 25QD21DP38

Chamber 19QE221P29

Type 20 maxi 5396-MA15772

Jim

[leversole]

I learned sum new stuff today! Yay!!

[doubleclutchinweasel]

Okay...
I figured out that these are Bendix "DD3" chambers, or an equivalent. They were most commonly used on buses. Lots of folks on bus and motor home forums talk about them and how to change tham out. So, I'm not in new territory here.
And, apparently, you do just remove the override circuit, and upgrade to a more modern chamber.
As near as I can tell, these (and the service chambers on the other axle) are size 24 chambers. But, I am not 100% sure, as old chambers and equivalent new chambers vary in appearance and outside dimensions.
If this tendonitis would ease up in my shoulder and elbow, maybe I could crawl around under there and see what the heck's going on!
More to come...
Kent

[BC Mack]

If you plan to remove the DD3's keep in mind that, if working, they still have good value, even as cores, so don't dumpster them.... latest rebuilt exchange prices are around $450 to $600 depending if your core was rebuildable. Rebuild kits are available, I get mine from Motor Coach Industries (MCI) but there are others.

However, when you look at "maxi's" going for $45 there is an incentive to convert... providing you have the physical room!!!!!

If you review the link in my last post you will see they are not complicated to overhaul, just fiddley..

however, for ease of maintenance and parts availability modify it to a standard spring brake air system, parts are off the shelf.

BC Mack

[Rob]

I learned sum new stuff today! Yay!!

Survey Saysssssssssssssss;

IMPOSSIBLE.

JK.

Rob

[doubleclutchinweasel]

If you plan to remove the DD3's keep in mind that, if working, they still have good value, even as cores, so don't dumpster them.... latest rebuilt exchange prices are around $450 to $600 depending if your core was rebuildable. Rebuild kits are available, I get mine from Motor Coach Industries (MCI) but there are others.

However, when you look at "maxi's" going for $45 there is an incentive to convert... providing you have the physical room!!!!!

If you review the link in my last post you will see they are not complicated to overhaul, just fiddley..

however, for ease of maintenance and parts availability modify it to a standard spring brake air system, parts are off the shelf.

BC Mack

No, I won't trash 'em!

[doubleclutchinweasel]

Still waiting on the new slack adjusters. Should be here in another week or so.

Trying to identify the size of the brake chambers on here. Can't find numbers on anything. In the Bendix literature, they mention only size 24 and size 30 DD3s. It's definitely not a 30. So, if they only made those 2 sizes, it must be a 24. And, I think it is safe to assume the service brake chambers would be the same.

The service chambers on the other axle MIGHT be 24s, but it's hard to tell. They are definitely 20s or 24s, based on the physical size.

A new 24 (or even a new 20, for that matter) looks like it will be a pretty tight fit in there, between the clamp band and the axle housing.

Has anybody put late-model chambers on one of this vintage ('70)? Did you have any clearance issues? What sizes did you end up with?

If nobody has, I may end up being the Guinea Pig!

Kent

[Rob]

Type 24/24 chambers should fit if you do not have backing plates for the brakes and they are open. Otherwise you will need to either install type 20, or go salvage yard searching for a later set of chamber mounting brackets to move the chambers inboard and longer "S" cams to tie everything together. You could also make a spacer to offset the chamber mount closer to the centerline of the truck and install longer "S" cams to make up the difference. You have offset slack adjusters now due to someone probably retrofitting the chambers currently mounted.

Rob

[doubleclutchinweasel]

Type 24/24 chambers should fit if you do not have backing plates for the brakes and they are open. Otherwise you will need to either install type 20, or go salvage yard searching for a later set of chamber mounting brackets to move the chambers inboard and longer "S" cams to tie everything together. You could also make a spacer to offset the chamber mount closer to the centerline of the truck and install longer "S" cams to make up the difference. You have offset slack adjusters now due to someone probably retrofitting the chambers currently mounted.

Rob

Yes, there are no backing plates, and the brakes are open, like you said.

I think I'll bring home a new size 24, and just try it. If my measurements are correct, it looks like everything should clear by about 3/16 of an inch.

And, I believe this is an all-original setup, as the build sheet called for DD3 chambers, and the chambers are mounted directly to the brackets, with no adapters anywhere.

Thanks,
Kent

[doubleclutchinweasel]

Type 24/24 chambers should fit if you do not have backing plates for the brakes and they are open. Otherwise you will need to either install type 20, or go salvage yard searching for a later set of chamber mounting brackets to move the chambers inboard and longer "S" cams to tie everything together. You could also make a spacer to offset the chamber mount closer to the centerline of the truck and install longer "S" cams to make up the difference. You have offset slack adjusters now due to someone probably retrofitting the chambers currently mounted.

Rob

More on the brakes...

One of the DD3s failed to release this weekend. Turns out, at some previous service, somebody swapped the service and parking lines. So, there was no way for the smaller (17 sq in) chamber to advance the rod far enough to allow the roller locks to disengage. Even when I swapped them back, I had to loosen the bracket slightly to get them to release. Works better now. And, it stops a lot better on the larger (24 sq in) diaphragm.

Have some 2424s located locally, and am waiting on a few more air brake tubing fittings from same source. Should have everything here this week. Going to remove DD3s and replace with the 2424s (after verifying clearance...but it looks okay). Will remove "inversion valve", and other DD3-related plumbing. probably put in a QR valve on the parking brake line. DD3 setup didn't have one. Probably couldn't use one, what with the inversion valve and such. Good time to put on a new pair of slack adjusters (they finally arrived).

Found a schematic using standard spring brakes that allows me to keep the remote reservoir and emergency release circuit intact, so I'm going to do that. I like having the isolated emergency release reservoir. Beats the heck out of caging the parking brake spring to move a dead truck off the railroad tracks!

So, hopefully I'll have the rear drive axle converted to current brakes and new brake line tubing soon. Then, I can move to the front drive axle and replace the cans and lines there, as well. The tees and junctions along the frame allow for a fairly small section of air line to be replaced at a time, starting from the rear. So, I can do that in stages and not get over-stressed by taking everything off at once.

More to come...
Kent

[doubleclutchinweasel]

Okay, got the DD3s replaced on the rear-most axle this week. Put in 2424s and new slack adjusters. 2424s fit well. Of course, I thought they would, once I determined that the front drive axle actually DID have 24s on it! Sometimes it's hard to determine exactly what you have when the parts are this old! Have to find old product information to be able to accurately identify this stuff.

The finished axle looks very neat. I was able to use another QR valve in the new spring brake release circuit as both a release valve and a convenient tee location. I mounted it back-to-back on the existing QR valve, so it looks really clean. I'll get a picture or three on here in a day or two. Might give somebody else some ideas.

The Gates air brake tubing sure looks better than 43-year-old hose. I went with G32 (compression) fittings instead of push-to-lock fittings. I like the PtL, but the compression fittings just make me feel better.

Managed to keep the isolated air tank at the rear, originally connected to the DD3 system, as an emergency brake release reservoir.

Still got a lot to do. But, I can now start moving forward, replacing a little air system at a time. Plan to do the front drive axle, and a few feet of air line, this weekend...wife permitting! Who knows; some day I might actually get through the whole air system!

Brakes...brakes are cool...m'kay?

Much more to come...
Kent

[doubleclutchinweasel]

A few shots of the new spring brake chambers, new tubing, and new slack adjusters.

Gonna do a little more "detailing" on it this weekend, and maybe do the next axle.  100_5699.JPG   372.51K   2 downloads  100_5696.JPG   410.82K   4 downloads  100_5697.JPG   378.83K   4 downloads  100_5698.JPG   403.27K   2 downloads