Geoff Weeks

I disagree with this statement, it holds the exhaust valve open just before power stroke, it allows for compression but not power.

I have successful bought from them in the past, but prices are high, and would not be my 1st "go to" place, They do seam to have some of the more "odd ball" parts.

here it is: https://www.partdeal.com/cole-hersee-dp-2-circuit-marker-lamp-switch-12vdc-dpdt-boxed-55071.html?srsltid=AfmBOoq--qdZhGYxWZBGhDjNAzT-eQJHLlTIeyEScZC1kPGRy-FOz2bH edit: Not finding any in stock, so may be hard to find and N.O.S. being the only option.

Somewhere I have a Cole Hersee book that has the switch and the wiring for that. IIRC it had 3 positions, center was off. Found it! (not in current Cole Hersee catalog) Sw number 55071 Had 3 terminals on the rear, Battery, Marker light feed, and common out to the marker lights. Flashed on for daylight, off for night time, by moveing the switch in opposite directions, spring loaded to center (normal) position. Cole Hersee's version worked with lights on or off.

I'll add mine with the caveat that I have never driven with one. The design, in theory is a sound one, use a purpose designed "lump" on a cam to open the exh valve at the right time to"dump"compression. Cummins touted this with the release of the ISX. Problems abound with execution. How much lift can you have at TDC? how much mfg tolerance can the design have and still function well? How much "extra"weight can the rocker system take and not float at high speed" How well with the oiling system meet the demands that the system requires? I can see all the potential of the design, but have no experience with the execution.

I don't know, if I'm not careful Paul may make the trip to put a lump on the side of my head!😄

That doesn't make it murder, nor does it absolve her actions. It is lucky she was the only one.

Not what you said, tho

Aslhi died because she made a stupid choice. She forced entry in to restricted area, as an ex military person she should have known that it might be met with lethal force. Same if she tried to force entry to the White House, a military installation, or even a restricted section of an airport! I sorry she died, but it was her actions. The fact that more weren't shot has much more to due with the lack of manpower and equipment than any legal restraint. I am more concerned about people shot by police in their beds during "No Knock" entry. Breyana Taylor was killed in her apt, a sleep without anything happening to those that killed her. Yes, her boyfriend opened fire on what he thought (do to no advance warning they were police) was a home invasion. Ashli was forcing entry to a restricted area, what happen can easily be anticipated. The fact that you sympathize with her political views doesn't change the fact that her actions were what cause the response.

I think he was talking cam (valve cam) timing.

Don't want you coming over and giving me a lump upside the head!

re-reading it does seam different valves were used, knob not fitting the new valve is a dead give-a-way that the valves are not the same. I think someone who knows and is close by is going to be needed to sort this out.

the 2nd "lump is at the side in your picture and only comes into play when the lash in the system is reduced. It is still the same operating principle where the exh is opened on compression near TDC. the lash adjust is similar to Cummins STC injector. The effective length of the push rod is changed and that changes the timing and/or travel of the rod.

Paul, I agree with all you say, I was just pointing out is or should be as good as a jake on a common rail fuel system and better then a jake on a injection pump/nozzle system, where the jake is operated off an adjacent cyl valve gear.

I always was sure, after all the paperwork was done, after a level 1 inspection to point out the the inspector that 30 years after the auto slack mandate, brake problems were still the #1 equipment OOS fault, and my manuals passed! I just can't resist the dig!

Being that the temp is in the minus side of 0, I spent some time reading in the Bendix manual. With one exception, my Post -121 braked stuff all use the MV-2 multi function valve and is the most common layout used in commercial trucks. Reading though the section of individual push pull valves, I think what we may have in the truck in this thread is the wrong valves being used for the function. The PP-3 and PP-7 look similar but differ in an important feature, The PP-8 should be the blue knob and can also be used on older trucks with a manual front axle limiting valve. Most of the difference comes down to the automatic trip function and if it can be over-riden. The PP-3 system would require the blue knob to allow applying the tractor brakes only. The PP-7 will trip when the yellow tractor button is pulled but can be "overriden" or pushed back in to charge the trailer with the tractor brakes applied, this is also how the MV-2 system works. My pre -121 stuff is even more varied, as the cut-off function is in the TP valve (TP-2) on the back of the cab. The tractor parking has its own low pressure trip, but that doesn't effect the TP valve at all. As the MV-2 and clones from other mfg were the most common, that is the one I am most well versed in. The few times I needed to change a PP valve I was sure to order by the tag and put the same type back in. I knew there were different types but till now never researched the differences. I did wonder why the three button system existed, when the two button can be made to do the same (with the correct PP valve), but now I know. The MV-2 is rebuild able, and very reliable, its biggest weakness is the rubber gasket getting soft and then leaking between the halves of the valve when the temp gets very cold, I think I still have one or two new rubber gaskets for the MV-2.

Compression brakes don't work effectively on throttle governed engines. You could, with a hydromatic prop change the pitch of the prop to make the most of what you do have. It reminds me of an old Loony Tunes, where Bugs is in a aircraft making a nose dive toward the ground and stops just inches above the ground (and just hangs there in the air) and Bugs gets out and says "Lucky for me this thing had Aiiir Brakes!"

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.