Poor Brake Practice and Runaway Ramps

[Iceni John]

For those folk who don't know what a Detroit-powered Crown with Jakes sounds like, here is my friend Al's number 13 that he straight-piped to make it sound better:

https://www.youtube.com/watch?v=rs9_ekHZKIc

(That's me sitting by the second window.)

And here's a restored 1950s Crown at Hershey, waking up the crowd:

https://www.youtube.com/watch?v=l3NP_pqFTzE

If I ever straight-pipe my bus it will sound similar to this oldie in Mexico:

https://www.youtube.com/watch?v=Wz_VJB3y89M

Jakes work quite well on smaller-displacement Detroits like Al's and mine, but for real deceleration nothing beats a big 14-liter Cummins 855 with Jakes, such as Crown and Gillig used in their 3-axle school buses.

John

[EastCoastCB]

Yeah, but you Crown owners are less than 1% of the school buses on the road. The rest of us can only dream of 855's and Jakes.

[Ronnie]

The jake brakes sound great but many towns restrict there use if unmuffled.

My experience with transmission hydraulic retarders is is what has been said, they really do heat the trans fluid a lot if you use them any more then just a bit now and then. Use them like you would a jake brake and you will boil the radiator. Ask me how I know....

[EastCoastCB]

Originally Posted by Ronnie

The jake brakes sound great but many towns restrict there use if unmuffled.

My experience with transmission hydraulic retarders is is what has been said, they really do heat the trans fluid a lot if you use them any more then just a bit now and then. Use them like you would a jake brake and you will boil the radiator. Ask me how I know....

Electromagnetic retarders are a lot better than the transmission type retarders.

[Ronnie]

Originally Posted by EastCoastCB

Electromagnetic retarders are a lot better than the transmission type retarders.

Locomotives use the traction motors to generate electric and that goes to a electrical resistance heater for braking in addition to the regular brakes. In the railroad industry this is called "dynamic braking". In electric cars they also do it but the power goes back to the batteries instead of heat to be dissipated.

Right now at least on buses any of the ways for braking, regular brakes, "jake" brake, retarders, etc just throw away the energy. Be neat to use the electromagnetic retarders and recharge battery banks for house electric. Come on smart people lets see if we can make this work. I can see it now on a hot day providing power for a/c, when traveling of course. Have to look into how much power is or could be generated.

[Ronnie]

Just a quick google search and I had forgotten someone mentioned the electro magnetic brakes used on buses take a lot of power? That is odd, in all other uses they generate power through motors becoming generators. Have some more research to do.....

[joeblack5]

Hmmm. I have a transmission oil style retarder in Dory and it seems to work very well. The transmission , an Allison B300R is piped into the cooling system. With other words coolant is going thru the transmission.

On long down hills I can see my transmission temp go up to 212F .

The Mercedes mbe900 series would be considered a medium duty engine and can be equipped with a Jake that is incorporated in the head.

The light duty standard powerstroke 7.3 has an ebv ...exhaust brake valve that is used for preheating the engine and is at least here a much hated emission reduction devise. With some easy software upgrade it can be used also as an exhaust brake.

[joeblack5]

It is all a matter of shedding the heat.

The Jakes shed it thru the exhaust with an insane amount of noise.
The hydraulic thru a transmission cooler or thru the radiator. The last is fairly elegant because on a long downhill the engine does not need cooling and it also keeps the engine warm.

The magnetic one must be huge to be able to shed the heat by itself unless it is cooled with ...???

The only nice design like Ronnie said is the electric vehicle that puts the energy back in the battery.

There were some designs that used the released brake energy to make compressed air or compress hydraulic fluid that when released helped with acceleration.

[EastCoastCB]

https://www.youtube.com/watch?v=5FMoUEmSsdE

https://www.youtube.com/watch?v=EW5LeTV07Tk

These are the most common auxiliary braking systems on school buses.

[JDOnTheGo]

My Allison B500R has a hydraulic retarder. It works magic controlling 50,000 lbs. I've never seen more than a very slight increase in trans temp and that includes use on some very serious passes in the western USA. The engine brake in my last motorhome (Cummins) was also a wonderful thing. One of the many advantages of a quality diesel chassis and also a necessity given the weight that they are capable of moving (and stopping, obviously).

I'm always preaching SLOW and will continue to do so. It seems to me that moving quickly is what costs big money. Caught in a too-tight U-turn? Hit the gas and see what it costs. Barreling down a mountain pass? Keep the speed up and see what it costs. Someone waiting for you while you back into your camping spot? Rush the process and see what it costs.

[Sleddgracer]

Originally Posted by EastCoastCB

These are the most common auxiliary braking systems on school buses.

looks to be a practical and effective system, and quiet too

[HazMatt]

Originally Posted by Sleddgracer

looks to be a practical and effective system, and quiet too

Too bad it's so damned spendy!
Quality's gonna cost you...

[Sleddgracer]

Originally Posted by haz.matt.1960

Too bad it's so damned spendy!
Quality's gonna cost you...

I just brought up a discussion page - they are spendy and they do have their problems including a very heavy voltage draw and installation can get quite complicated - fire fighters were very favorable towards them, independent truckers not so much

[EastCoastCB]

Originally Posted by haz.matt.1960

Too bad it's so damned spendy!
Quality's gonna cost you...

Its free if you buy a REAL Colorado mountain bus.

[HazMatt]

LOL

Originally Posted by EastCoastCB

Its free if you buy a REAL Colorado mountain bus.

I'll keep that in mind for subsequent bus buys! 🤙

[EastCoastCB]

Originally Posted by haz.matt.1960

LOLI'll keep that in mind for subsequent bus buys! 🤙

A 7 or 8 window with mechanical engine, high headroom, retarder, and air ride is sorta my "dream bus".
I've seen such buses pop up on Colorado and Idaho.

[CaptSquid]

When I drove for living, my first truck (Century Class Freightliner) had no jakes. No biggie, since i drove almost exclusively in New England. The second had jakes, but if you used them at all, the truck flamed out on the way back up the other side. This company has since been bought out.

The last company I drove for didn't maintain their fleet at all. This is where I experienced brake fade coming down the Eisenhower pass. Talk about scared! I had to wait with the front end parked up against some rocks to cool the brakes. I tightened all the slack adjusters myself.

[HazMatt]

Yup, I hears ya! That would fill a number of items on the punch card.

Originally Posted by EastCoastCB

A 7 or 8 window with mechanical engine, high headroom, retarder, and air ride is sorta my "dream bus".
I've seen such buses pop up on Colorado and Idaho.

Mythical beasts may be presumed to exist...
[emoji882]

[family wagon]

Originally Posted by joeblack5

Hmmm. I have a transmission oil style retarder in Dory and it seems to work very well. The transmission , an Allison B300R is piped into the cooling system. With other words coolant is going thru the transmission.

On long down hills I can see my transmission temp go up to 212F.

I haven't had many occasions to use the retarder in my B300R, but on the couple that come to mind my experience was similar to yours. I think I recall putting the transmission down a couple gears, but when it was time for a brake stab, instead I set the retarder to max. Whoa. That was actually too much. I backed off the retarder a little and didn't touch the service brake during the rest of the descent. I kept a nervous watch on the transmission oil temp gauge but didn't notice any rise.

[Ronnie]

Those of you have found the transmission retarders to be good and not heat it up much, I wonder how they are built? Mine is (was) an old Allison from 1971, that used basically a torque converter that the outer case was stationary and part of the transmission case, so just the impeller turned. A plaque on the dash said not to go over 380 degrees. Oouch. Over 300 would boil the radiator so never did get close to 380. So guessing they must have improved them a lot on newer ones.

I still want to look into regenerative braking, just got that stuck in my mind....