Check slack adjusters

bevans6 · August 10, 2011, 05:04:33 AM

"What do you mean that auto slack adjusters should not be adjusted? "

I don't recall hashing it over but we probably did. The point there is that automatic slack adjusters adjust automatically, usually with full brake applications. So if you measure your stroke and it's out of specified range, then do some full brake applications after making sure the auto slack is greased up and has every chance to do it's thing and it won't auto-adjust back to specification, then it's broken and needs to be serviced or replaced. You should never have to manually adjust automatic slack adjusters. You do need to regularly measure their stroke to make sure they are working properly.

Brian

lostagain · August 10, 2011, 06:55:47 AM

Someone mentionned a tool you can buy at truck stops to apply the brakes and check slack adjusters stroke for a one man operation.

What is it? What does it look like? How do you use it?

JC

buswarrior · August 10, 2011, 07:04:47 AM

Don't waste your money on gimmicks.

Get a regular carpenter's bar clamp with reversing ends, set it to push out instead of clamp in.

Or, cut a discarded hockey stick shaft to length to use as a prop.

Each coach is different, but the idea is to set the prop against something solid, the under dash, the seat pedestal, in order to hold the brake pedal down. If you must use the steering wheel, try to tuck the bar as close to the centre in order to not promote bending of your wheel.

Easiest is to hold the pedal with your foot and slip the prop into place, and same when releasing, in order to minimize scratching or otherwise damaging your bracing point. That brake pedal has a lot of strength to it that we don't realize until after the prop slips out...

happy coaching!
buswarrior

lostagain · August 10, 2011, 07:08:51 AM

Thanks BW.

That is simple enough. Easier than finding one of my sons or my wife to ask them to step on the pedal.

JC

bevans6 · August 10, 2011, 07:11:46 AM

I mentioned it (it's becoming clearly obvious that I am a brake nerd and a bore at cocktail parties...).

It looks like a stick with a U shape on one end that hooks under the steering wheel, the other end has a rubber foot that is placed on the brake pedal and it adjusts in length so that you can push down the pedal and fit it so that it holds the pressure for you while you run around and measure stuff. I use my hammer, it happens to fit perfecting using the dash frame under the instrument panel. You could cut a stick to length and label it "NOT FIREWOOD"...

Edit: BW beat me to the stick... Actually I had a nice bat that worked perfectly that I got at a truck stop to thump tires with and threaten intruders at my door, until I left it on a picnic table in Nova Scotia...

Brian

buswarrior · August 10, 2011, 07:16:50 AM

" NOT FIREWOOD"

roflmao!

Best advice on the board!

happy coaching!
buswarrior

bevans6 · August 10, 2011, 07:49:41 AM

BTW, I personally find it acceptable to measure the stroke on DD3 actuators by measuring the static extension and then applying the parking brake. It applies and holds 85 psi against a slightly smaller diaphragm than the 30 inch service brake diaphragm, but it still develops well over 2000 pounds of force. That's a little easier than finding my hammer.

Brian

niles500 · August 10, 2011, 10:38:18 AM

Brian - I stand corrected - check the time of my post

- should have said 'inspected' -

bevans6 · August 10, 2011, 10:44:21 AM

My own rule, which I probably break from time to time, is don't post after midnight or more that three drinks...

buswarrior · August 10, 2011, 06:17:25 PM

Best posts are written late and smoothed out...

happy coaching!
buswarrior

Mex-Busnut · August 10, 2011, 07:46:41 PM

I am surely enjoying this post. I have so much to learn!

Maybe somebody can tell me where in the pictures are my slack ajusters. I am *supposing* it has something to do with the vertical springs holding the left sides of the brake shoes together?

Also, because our bus is three decades old, I had the diesel mechanic take the four corners apart, checking brakes, washing and re-packig bearings, checking all air hoses, etc. He said the front brakes are recently changed and in very good shape. The rear ones (in the pictures) looked to have plenty of pads left, but he said they were cristalized, and should be changed. He said the best would be Merritor (spelling?) brand, so that is what he installed. He also sent the drums to the machine shop to have them "rectified", as they say here.

Señor Rolando, the diesel mechanic, will also be servicing the air compressor. He says it is taking far too long to get air pressure up.Several air hoses are not in good shape. He will also replace all water hoses and belts, as well as service the radiator fan bearings.

I also took the alternator over to a shop I normally use. That guy will replace bearings and brushes and give it a good checkout. (It was making a wierd noise.)

lostagain · August 10, 2011, 07:57:17 PM

The slack adjusters in these photos are behind the brake drums.

Ask Senor Rolando to show them to you.

JC

buswarrior · August 10, 2011, 08:05:04 PM

If he asks Senor Rolando about what is behind the brake drums in those photos...

The slack adjuster is the lever that is connected to the end of the brake chamber pushrods.

The slack adjuster lever rotates that somewhat "S" shaped cam that is between the rollers on the two brake shoes.

The centre connection between the slack adjuster and that cam has a worm gear inside it in order that the the relationship between the cam and the lever may be rotated, or adjusted, in order to compensate for lining wear.

happy coaching!
buswarrior