How many types of DD-3 are there?

Fredward · June 07, 2009, 07:02:31 PM

I'm replacing a boot on the right rear DD-3 on my MC-5. The "DD-3" on my bus does not look like what is pictured in the MC-5 manual. For one thing, the clevis does not have two locking nuts below it nor does it appear to be threaded on at all. The boot I purchased which is an OEM part does not appear to even fit on this brake canister. Could someone have upgraded the canister to a newer version of DD-3? It still has three hoses going to it and it basically looks like the picture in the manual except for that operating rod and clevis and the boot must be different also.

When Bench testing with shop air being applied to the service port, shouldn't the piston retract when the air is removed? This one stays extended.

Fred

JackConrad · June 08, 2009, 02:41:41 AM

Quote from: Fredward on June 07, 2009, 07:02:31 PM
When Bench testing with shop air being applied to the service port, shouldn't the piston retract when the air is removed? This one stays extended.
Fred

Were you also applying air to the port that keeps the rollers from holding the rod in the applied position? Jack

buswarrior · June 08, 2009, 12:14:01 PM

There are lots of rubber boots out there for lots of different kinds of brake chambers, so perhaps a mix up?

Are you able to post a picture of what you have?
Or e-mail it to a moderator, they'll get it on here!

happy coaching!
buswarrior

Fredward · June 08, 2009, 09:53:36 PM

We figured it out. I took the actuator down to C&J Bus this afternoon and they showed me what I have to do. It has a short shaft with the clevis in it so they gave me a standard length one which means I'll just have to adjust my slack adjuster I suppose. Also, it was installed upside down so water and crap would accumulate so I'm changing that. Hopefully I can just reorient the air fittings so I don't have to take the canister apart.

Jack, no I didn't realize I have to have air on the locking port in order to get it to retract. I also took it apart and am cleaning up the rollers. THey were rusty and sticky. Lucky the dang thing ever released.

I'll post a couple of pictures Tuesday. Going to bed now.

Len Silva · June 09, 2009, 07:28:28 AM

Remember that when you are done, the slack adjuster should be perpendicular to the shaft.

johns4104s · June 09, 2009, 07:42:41 AM

Fred,

Your pictures will help all of us with DD 3,s

Thank You

John

Fredward · June 09, 2009, 10:08:11 AM

Here are pictures of it before removal. And sitting on the bench fully activated (oops).
As you can see in the installed photo, the shaft and slack adjuster are not even close to 90 Degrees. I have a new, longer actuator shaft which I believe to be oem which once I install it should make it easier to get close to 90.

The unit works OK and does not leak so i'm hesitant to take it any further apart but I have removed the rollers for cleaning and lubricating. I wonder what i should lube those rollers with?

The other thing i noticed when i removed it was it was installed upside down. The area that should allow water, etc. to drain out was installed facing upward and there was some moisture in there when i removed it. So i will try to turn it 180 degrees when i reinstall it. Hopefully the lines all reach that way.

Fredward · June 09, 2009, 10:09:37 AM

And here's the picture of the DD-3 as installed before removal.

buswarrior · June 09, 2009, 05:06:36 PM

The centre and end portions may be rotated to position the air connections. You're stuck with the location of the base one being spun 180 degrees.

Loosen off the clamps and 'round you go.

If you are going this far, a set of fresh diaphragms finishes the job for many years to come.

My 1975 MCI manual refers to this lubricant for the piston and collar bores, shaft, piston grommet, piston and roller cavity: B-W240176, a barium base Spec 204M lubricant....

Heretic that I am, I have been known to give the DD3 a squirt of the name brand lube that happens to be in the gun and going into everything else around the place...

Whatever you use, use the same to top it off at chassis lube time.

The manual also recommends an annual disassembly and cleaning for DD3 chambers... Once a busnut has done them, I think you'll be good for a fair bit longer than that...

Rusty rollers? If they are pitted, that would be reason to replace all 8 of them.

Remember the anti-seize for all your threads for the next time it needs to be taken apart!

happy coaching!
buswarrior

johns4104s · June 09, 2009, 06:56:56 PM

Fred,

My DD3,s are installed the same way, I didn't take mine off i changed the boots out in place. The new boots were very tight, had I known I would of used a little grease and as it was I used a hammer tapping lightly. Tighten a Little, hammer a little and so on. This was the only way I could get them snug.( thank you bus nuts for the advice)

May we have more photos as you proceed, Thanks

John.

Fredward · June 10, 2009, 06:45:25 AM

Thanks BW. Some of the rollers are real bad so I'll probably replace them today. It looks like I'll be able to reinstall 180 degrees from the way it was before and still attach the lines without issue. I'd rather not take it apart and spin it if I don't have to. I'm not too interested in replacing diaphrams. I don't understand enough about when the springs are released and when they are not released so I'm afraid to take it apart and it works just fine (right now).
Fred

gmbusguy1 · June 10, 2009, 07:22:29 AM

Fred, there is no spring pressure to worry about when you replace the diaphragms the parts are cheap and readily available. also in the photos you posted I did not see or maybe missed it but there is (I think) supposed to be a metal plate that covers the white plastic end where the shaft comes out and would go between the dd3 and the coaches mounting flange.

DD3 chambers are not spring loaded like more modern spring brake chambers

Please do a search on this board for DD3 and I know you will find a Bendix service manual in PDF format I think Buswarrior posted it a few months ago

these dd3 chambers are made left and right for MCI and GM coaches and are NOT interchangeable

Please find the information that will help you brakes are very important and need to be repaired correctly

HTH

Chris

Fredward · June 11, 2009, 10:43:28 AM

Chris,
there is a plate missing that i removed to get at the rollers. There's also a gasket missing that i will replace with RTV when I reinstall. I have not done anything more as I've had no time to work the past couple nights.
Fred

johns4104s · June 11, 2009, 03:19:49 PM

Fred,

I trust you had time to take more photos?

Thanks

John

Tony LEE · June 11, 2009, 03:42:38 PM

"the shaft and slack adjuster are not even close to 90 Degrees."

As I understand it the 90º applies when the brake is applied and the shoes are contacting the drums. This gives the maximum lever length and so maximum braking force.