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Author Topic: More Jake Brake Questions  (Read 2635 times)
kbunnystarr
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« on: November 07, 2006, 10:34:24 AM »

I have been doign some looking into and also talking to a few people around here.............from the looks of it, there seem to be 2 types of Jake brake systems.....one that is working with engine and one that is workign with exhaust system......how do you decide which is best for what you have bus wise.and one person asked me is it a problem to use a jake with an automatic transmission?  Thoughts please?
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Buffalo SpaceShip
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« Reply #1 on: November 07, 2006, 11:07:16 AM »

If you follow my Jake thread, I now know a lot more about them than I did just an hour ago. Anyways, the only kind of Jake that works on a 2-stroke diesel like yours (ours) attaches to the heads and holds down the exhaust valves via solenoids. So, technically, it works with both the engine and the exhaust system.  Wink

My coach has an automatic and the Jakes work great on any kind of incline, or even around town on the flats... when the tranny is in lockup, anyways. In your case, I seem to recall that you have a VS2-8 Allison... so, a Jake on yours will hold back your bus as long as you are in direct mode. Probably above 15mph or so. In fact, GMC built a few NewLooks with OEM Jakes and the VS2-8 (eh, Paul)... so they must work!

Living out west, and especially with an automatic coach, Jakes are a required safety item, IMHO. Coming down Vail Pass (or Cabbage or The Grapevine or...), it's like night and day. And it's the reason I'm presently covered in grease, grime, and sweat from stem to stern!  Grin

HTH,
Brian B.
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Brian Brown
4108-216 w/ V730
Longmont, CO
kbunnystarr
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« Reply #2 on: November 07, 2006, 11:10:57 AM »

I have a v730 alison trnsmission.........so did you install your self?  ( thanx for your post)  i am trying to figure a rough for HAVING them installed as well.........
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Eagle
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« Reply #3 on: November 07, 2006, 11:13:43 AM »

You can not use an exhaust brake on a DD 2 stroke engine it has to be a Jake brake system.  I wouldn't be without a Jake brake system.
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DrivingMissLazy
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« Reply #4 on: November 07, 2006, 11:16:34 AM »

It is generally considered a major mechanical task to install Jakes. I do not recall but one or two persons on the boards over the years that have attempted it. Not that you can not possibly do it, but based on your apparent overall mechanical experience, I do not think I would recommend you try it. I know i would not and I have been working around mechanical equipment all my life.
Richard
BTW, there are several types of retarders, all work differently, including Jakes, exhaust, Thelma and transmission.
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kbunnystarr
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« Reply #5 on: November 07, 2006, 11:22:07 AM »

i wouldnt even consider doing it myslef  Shocked  so no worries!  i am trying to get  opinions on what is the best system for my bus set up and a price to expect to pay....so i knwo if im getting robbed or not  Grin
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« Reply #6 on: November 07, 2006, 11:26:26 AM »

Oops, V730, it is! Then we have the same tranny. Cool!

No, I wouldn't install Jakes myself. I'm just trying to fix mine... a broken solenoid or something minor (hopefully). There's a lot of mechanical work to the install... valve clearances and offsets, then a rack re-run when you're finished. Taller valve covers, wiring, etc. It's best to find an experienced 2-stoke shop... and those are getting rarer.

I seem to remember HB Industries out of El Cajon, CA, near S.D. carrying used Jakes. There's also an outfit in Williams, CA. You're mid-coast CA, right? Or am I getting folks mixed up again??  Tongue

HTH,
Brian B.
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Brian Brown
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kbunnystarr
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« Reply #7 on: November 07, 2006, 11:41:36 AM »

im currently in Lake Havasu City AZ but will be in Santa Cruz within a few months, maybe sooner
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DrivingMissLazy
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« Reply #8 on: November 07, 2006, 11:53:02 AM »

I suspect you are going to pay a minimum of $2,000 and possibly quite a bit more. Depending on whether you can find a set of used ones and whether you can find an old time DD 2 stroke mechanic who will moonlight and do it.
Richard

i wouldnt even consider doing it myslef  Shocked  so no worries!  i am trying to get  opinions on what is the best system for my bus set up and a price to expect to pay....so i knwo if im getting robbed or not  Grin
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« Reply #9 on: November 07, 2006, 12:16:20 PM »

In response to the OP question, while Jake brakes sometimes get referred to as exhaust brakes, I think what the OP was asking is what is the difference between something like a PAC brake and a Jake.  The exhaust brakes such as PAC or Banks that are typically put on pickup trucks do not alter the valve train, they are really not much more sophisticated than stuffing a potatoe in the end of the exhaust pipe.  A Jake on the other hand alters the valve action such that the compression stroke pressure is relieved before it has a chance to expand in the cylinder on the downstroke.  Thus the engine uses energy to compress the air in the cylinder and then uses energy to pull a vacuum in the cylinder on the downstroke.  The combination of efforts creates the braking effort that Jakes provide.

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« Reply #10 on: November 07, 2006, 12:19:53 PM »

In response to the OP question, while Jake brakes sometimes get referred to as exhaust brakes, I think what the OP was asking is what is the difference between something like a PAC brake and a Jake.  The exhaust brakes such as PAC or Banks that are typically put on pickup trucks do not alter the valve train, they are really not much more sophisticated than stuffing a potatoe in the end of the exhaust pipe.  A Jake on the other hand alters the valve action such that the compression stroke pressure is relieved before it has a chance to expand in the cylinder on the downstroke.  Thus the engine uses energy to compress the air in the cylinder and then uses energy to pull a vacuum in the cylinder on the downstroke.  The combination of efforts creates the braking effort that Jakes provide.



To further muddle thing up, Jacobs also makes an exhaust brake.

Len
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« Reply #11 on: November 07, 2006, 01:11:39 PM »

A little bit of history. Clessie Cummins, founder of Cummins engine, invented the Jake brake as we know it today.  He worked with the Jacobs drill chuck company to machine and manufacture his compression brake.  Cummins sold his interest in the brakes to Jacobs.  Hence, the Jake brake.  Later, Cummins decided to make their own brake system and called it the PacBrake.  PacBrake and Jacobs both make almost identical compression type engine brakes.  What is referred to as an exhaust brake is a butterfly valve that is after the turbo that stuffs up the exhaust to create back pressure, hence more braking power.  You cannot use this on any of the 2 stroke Detroits since the extra back pressure would be absorbed by the roots blower and cause blower failure.  Any 4 stroke engine can use either of the types of exhaust or compression brakes.  Also is the driveline Telma electric retarder.  It looks like a big disc brake with electromagnets on either side.  It is basically an electric motor in reverse.  The Telma can produce up to 800 hp of braking power.  Also is the Allison hydraulic retarder.  This works especially well with buses in stop and go traffic in conjunction with the service brakes.  It isn't so good on a long down hill because of heating up the transmission fluid.  On Caterpillars you can get the BrakeSaver which is a hydraulic retarder mounted on the end of the engine before the clutch.  Same problems as the other hydraulic retarders.

If you're putting on any of them the Jake or Pac brake will work well.  Every truck we sell here in Calif for over the road use has a Jake type brake installed.  Have seen some mid west trucks without them.  But as said before, if you stay east of interstate 25, you don't really need one.  If, on the other hand, if you go west of interstate 25, go to Canada, Mexico, or Alaska, it is strongly recommended, no matter what the cost.  You need only once to loose your brakes without mishap to convince you of the importance of the Jake Brake.  It is those that don't survive that can't talk about it.  Good Luck, TomC 
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Tom & Donna Christman. '77 AMGeneral 10240B; 8V-71TATAIC V730.
kbunnystarr
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« Reply #12 on: November 07, 2006, 02:44:39 PM »

thank you for all the replys!  Grin
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Jerry Liebler
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« Reply #13 on: November 07, 2006, 03:12:09 PM »

Several posts above have argued that Jake brakes are necessary to safely drive the mountains of the western US.  If this were true Greyhound and all other bus companies would have so equipped their busses, they did not.  Similarly if it were true the USDOT would have required them, they did not.  Yes they are nice but they are not needed to SAFELY descend any mountain in a reasonably loaded bus.  Slow down at the top, select the proper gear, maintain the correct (safe) speed by constant (light) brake pressure and the engine will do most of the braking even without a Jake.  Yes constant light braking is the correct technique as it does produce the lowest temperature rise of the brakes.  I'd like to have Jakes, but am no worse off than thousands of Greyhound drivers without them.  And yes I've descended 'cabbage' , vail pass, the grapevine and many other significant western grades without overheating the brakes of my bus.

Regards
Jerry 4107 1120     
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RJ
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« Reply #14 on: November 07, 2006, 03:20:56 PM »

Jerry -

Good point.  Let's rephrase the recommendation to say that:


"Jake brakes are a very nice OPTIONAL braking device to have on your coach, which enhance the safety factor for you and your family while operating in mountainous areas.  This statement also applies to other types of engine brakes, as well as hydraulic transmission and electrical driveline retarders."


 Wink
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RJ Long
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