Geoff Weeks

I have had very little experience with Dynatard, only enough to know when setting the valves, you must follow the instructions to the letter or your clearances will be off. I do have a lot of experience with Jakes. Jake's were designed for common rail fuel systems where the injector was triggered by a dedicated lobe on the cam. The injection timing is ideal for opening the exh valves for compression braking. This left Cat an Mack out of the picture because they used an injection pump and no injection cam or rocker. So to make a Jake work on those engines, they use a valve rocker on an adjacent cyl valve train to open the exh on the cylinder at TDC. Unfortunately it is less than ideal timing, so jakes are less effective on Cat engines then Cummins. Mack solved that by the Dynatard system, where the cam profile for the exhaust is customized with a "two lump" profile, the normal exhaust and a 2nd small one that could open the exhaust a bit at TDC compression with the hyd lash cyl at the rocker. I have 0 driving experience with the Dynatard, but am surprised to hear people say they were less good than a jake on the same engine! In theory anyway, by grinding the cam for the purpose, Mack should be able to idealize the opening time when the Dynatard is active, making it every bit as good if not better than a Jake on a common rail (Cummins, 2 stroke Detroit) engine. May be the "Lift" on the Dynatard side can't be high enough to be as effective? IDK but am surprised to hear people say it is less effective. May be they are judging "effective" by "Noise made" and not retarding power? Opening the exh at less than ideal time make make more noise and less retarding power. Lots judge a retarder by how much noise it can make! They hate the hydraulic Cat "Brakesaver" because it doesn't make any noise!

To answer my own question on why some got anti-compounding and some did not, it seam the function, while helpful on trucks without auto slacks is required when auto slacks are used as the locking/self adjusting mechanism isn't as strong as it is on manual slacks. Funny those pushing for auto slacks never mentioned they were WEAKER! I never owned anything where they were required, my Marmon came close but before the deadline!

In its simplest form, anti compounding just supplies the higher of the two air pressure supplies to the spring brake. So when the parking brake is off, system pressure is applied to the spring brake hold off chamber, but when the parking brake is on, there is no air supplied by the parking brake valve, so hold off chamber is empty. However if the parking brake is off, and the foot brake is applied, air will be supplied from the service system via the double check to the parking can and partially remove some spring pressure. A double check does just that function, it supplies the higher of the two inputs to the output.

Here a link to the Bendix manual if you want to read through it yourself: https://www.doverbrakeinc.com/downloads/catelogs/BENDIX AIR BRAKE HANDBOOK.pdf It explains the use and names all the valves.

This is right from the Bendix manual, so not me saying it. Yes a double check is used in some systems for anti compounding, it does the job and IS correct. Later as more valves like inversion were added, they move from a simple double check to a multi function valve. Some were QR/double check some were Inversion/anti compounding, but a double check was/is used for anti compounding.

Here is one form of the "all in one"/ Here is a Qr that acts as an anti-compounding as well here is an inversion valve Lastly there are the tractor spring brake valves that are Inversion and anti-compounding into one valve

Listed right in the drawing as double check. An inversion valve is different. They do completely different functions. An inversion valve has nothing to do with anti-compounding. An inversion valve is used to modulate spring brake pressure in the event 1/2 of a duel system looses pressure. Many duel systems are plumbed so one rear brake is on one side and the other and the steer axle is on the other side. So a failure on the side carrying the steer axle would leave only 1 axle braked. If the spring brakes are placed on the side with the steer axle, the inversion valve exhausts spring brake pressure, applying the spring brake in coordination with the air pressure applied to the air pressure to the remaining axle. It provides more controlled emergency braking that slamming on the spring brakes. Neither of my 9670's had anti-compounding nor inversion, but my Marmon has both. Often the anti-compounding and inversion are plumbed into a common duel function valve, because the inputs needed are the same, but the function of each is different. An inversion becomes more important (mandatory) when a truck is used as a straight truck (like a tractor converted to a dump with the sleeper box removed). A loss of side of a loaded tractor, you'd still have trailer brakes plus one side at least of tractor brakes. It is never operated loaded without a trailer. A straight truck is loaded without a trailer and a single axle of brakes would not meet the emergency braking stopping distance call out the the reg's. I don't know why some were fitting with anti-compounding and others were not, I just know that it happened.

We don't and can't from this end of the internet. The double check may or may not be defective, but until the plumbing is sorted, anything is possible. Remember, when he bought it the spring brakes were backed off/caged. It is likely that there is more than defective parts at issue here.

None of this addresses why the parking brake is connected to the trailer air supply control?

yes it does, look at the last post on the previous page, straight from Bendix air brake manual.

Anti-compounding

Idk? This is one of those times when being there as seeing what is what will make all the difference

what is confusing me is saying the line from the dash is coming from the red (trailer supply) valve. Either he is mixed up or the plumbing is mixed up. "Red arrow feeds all the way to the cab through the firewall into the trailer emergency valve in the dash." Otherwise it matches the Bendix diagram I posted on the bottom of the last page.

What is confusing me, is nothing should go straight to the trailer red knob. The red knob outlet should go to the tractor protection valve (TP-3 or similar) on the frame. That said, I have not been around a lot of 3 button trucks, and the few that I was, never had a problem. This is what I think I am seeing in your photo, but you notice it is not connected to the trailer valve

never seen a tach drive that wasn't either 1:1 or .5;1 Either camshaft speed (most four cycle) or 1:1 for two strokes.

Draw a line diagram of how the air lines are run and to which ports and post here so we are all on the same page as to what we are talking about.

Double check passes which ever supply is higher to the outlet, without allowing the higher inlet pressure to pass to the lower (or no) pressure inlet port. The thing with 5 lines going to it is a relay. the two lines closest to the frame, parallel to the frame should be reservoir pressure, the two perpendicular to the frame are brake pressure output and the one on top is signal air pressure.

I had hubs "spray welded" and re-machined before with good results. Often the amount of metal needed make a sleeve difficult and over-boreing effects the seal area also, so sleeve would have to extend out to there.Hub is thin at that area. If you have go with machine work talk to a few machine shops to see what they recommend.

Knock the old race out, buy a new race (cheap) and see if it is snug in the hub, if it is, your good to go, if isn't you have several options.

last picture looks like a double check The other is a relay valve.

I drove a Bristol Lodekka from Columbus, OH to Chicago with a dead alternator! Long slow trip

"Ok you bearing, you have been warned, you better slip on there or I taking to the 50 ton press"😆

Phelan and LaCrosse made a bunch of those. They end up making the rounds of farmers etc as they are too short to haul much that is around today. Couldn't use to to go after a truck, too short, Might work for an antique tractor. Use is limited in today's world is all I am trying to say. That one has tubeless tires at least from what I can see, that is a good thing.

Going way back in my fuzzy memory, some trucks with the ign on and the parking brake set, would activate brake lights. With key off brake light switch is fed from another switch that is always powered. Not 100% 'cause we are talking about a 1/2 century ago. Get the air system fixed 1st then see where the electrical is at. Air systems are not all the same, and can vary widely. Some use relay valves on the spring brakes some do not, some have anti-compounding on the spring brakes, others do not. some use inversion valves on the spring brake side for emergency use of the spring brake when half of a dual air system is down. That is why it is so important to have pictures and label where each line goes. My 9670's didn't have any relay valves on the tractor, anywhere! straight piping from the treadle valve to the Q/R on the axle housing itself.

Is anywhere in that state out of danger?