No, this isn’t a question about what they are, but how well they work. Specifically, Jake Brakes (a brand name of engine brakes for big trucks) slow only the drive wheels. (I would think that regular brakes also connect via hydraulic lines to the trailer.) Doesn’t that cause a tendency to jackknife?
Jake brakes do not have anything to do with the wheels inasmuch as the actual braking is concerned. A Jake brake is an engine compression brake.
Now that I reread the OP, I see that you know it’s an engine brake. For lack of a better comparison, it’s akin to downshifting in a car. That doesn’t just affect the drive wheels, it affects the entire vehicle. Same with trucks: the entire vehicle decellerates. The drive wheels really don’t have much to do with it.
When downshifting a car, it’s the drive wheels that provide the stopping power, unlike braking, where all four wheels apply stopping power. I would think that Jake Brakes do the same thing, as if you could apply brakes only to the drive wheels. The trailer is stopped by pushing up against the tractor. If everything is lined up, yes the whole vehicle decelerates together, but I would think heavy engine braking in anything but a straight line could introduce some control problems.
That’s one reason you’ll never see a front-wheel-drive motorcycle. A heavy downshift would throw the ass end right up.
I think the key here is that neither engine compression braking in a gasoline engine nor exhaust or intake braking in an diesel engine provide enough force to put the drive wheels at risk of breaking static traction and skidding. Skidding is what usually causes jackknifing; some wheels maintain their path of travel and others (the rear tractor wheels, usually) do not.
So, what we’re really talking about is whether an exhaust or intake brake has the capability to skid the drive wheels. I’d say not, just as its unlikely the engine can produce enough power to spin the drive wheels under acceleration, except in low traction situations.
Sorry, brother Doors but Jake Brakes, aka Extarders, via their action on the driving axle(s) can cause handling problems on wet or slippery roads. Were one to downshift too aggressively and elicit slip as opposed to controlled deceleration, the same measure of control is lost. Personally, I flip Jakes to the off position if single level as soon as rain starts, and if Hi/Low, I’ll select low if heavily laden, otherwise off.
The brakeing power of an engine brake is transmited through the drive train to the road. The drive wheels are the last link in the drive train,thus are the only wheeles that are slowing the vehicle.
Now back to the OP. Jake brakes are good for slowing down the vehicle in heavy traffic or going down hill without overheating or depleating the air supply or your standard brakes. They are not good for stoping without also useing your air brakes witch will also slow the trailer, thus helping to avoid jack knifeing.
There are other considerations that make that impractical (center of gravity, for one), though one manufacturer managed to build a successful two-wheel-drive enduro style motorcycle, using a hydraulic motor to drive the front wheel. At any rate, most modern motorcycles have front brakes sufficient to loft the rear wheel in what’s usually called a “stoppie”. In a maximum braking event, almost all weight is transferred to the front wheel.
I wish to disagree. An engine brake has a degree of effectiveness which diminishes in direct correlation to engine RPM. Any good operator can bring a truck at full GVW to darn near stopped (assuming dry road) without ever touching the service brake via downshifting, and keeping the engine braking power high. That’s part of the beauty of a Jake brake-it doesn’t wear, requires no adjustment, and lets the operator spare the wheel brakes the heat/adjuster issues. When training drivers, I’d make it point to demonstrate use of Jake (and if an automatic) and Allison output reverser and take a truck from 65 to 15 without touching the brake pedal.
A compression brake isn’t going to have enough effect on the drivers to cause a jackknife unless you’re on ice or another very slippery surface. Most compression brakes have two positon switches. I always cut the compression braking by half when on ice or snow, then engaged the other half in sequence. As I’ve mentioned before, I had a foot switch, in series, on my compression brake, if slippage occurred, I could instantly disengage the braking effect.
Using a compression brake becomes second nature, it’s not as complicated as it may seem.
Nitpick, Jake is a manufacturer of equipment that includes engine compression brakes, but also includes other braking technology including electromagnetic braking.
But doesn’t “Jake Brake” unambiguously refer to the compression brake? If you were telling a colleague about the Jake-manufactured electromagnetic brake you just got, you wouldn’t refer to it simply as a Jake, but would specify the type of brake as well, wouldn’t you?
Sort-of-kind-of-maybe. Jake the manufacturer has made it a point to not have the word Jake Brake mean compression brakes. This is mainly because they don’t want to loose the trademarked term. Also some compression brakes are very noisy and they don’t like to be associated with that.
OTHO they have to walk a strict line here, just like xerox, kleanex, rollerblade and the like. It is good for them for the consumers to call compression brakes/photocopies/tissues/ inline skates by their brand name as brand reconition, but the can’t support this or their brand name will become generic and all competors can start selling jake brakes, xerox, kleanex, rollerblade…
So to answer your question, if you ask Jake if “Jake Brake” unambiguously refer to the compression brake?, I think it’s safe to say that Jake would say no.
Questions:
[ol]Is it out of order to say “Utter, utter nonsense” in GQ?
[*]ADUSAF, what the hell interaction do you think there is between an engine brake and the road, other than through the wheels that are coupled to the engine? The engine braking fairy? 
[/ol]
Meh. Please read the above post through snark filters. I seem to be extra ratty today. 
I wasn’t much interested in what Jake’s lawyers would say. Let me repose the question.
Another truck driver says to you, “I just installed a Jake in my truck.” Is there any chance he means anything other than a compression brake? Because I would have thought there wasn’t, that if he had installed a different Jake product he’d have specified it, indeed would have to specify it to avoid misunderstanding.
There have been front wheel drive motorcycl;es, including one where the engine was inside the wheel.
Brian
Nitpick[sup]2[/sup], the manufacturer is Jacobs Vehicle Systems. “Jake” is a nickname.