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Post by ThinkinOnIt on Jul 22, 2004 13:39:51 GMT -5
I have asked and heard tell of magical swapping cylinders (even a variation which mention that the noise came from big piston hammering there way into little cylinders, and all such boloney)
how does the jake work, i am sure that this is a dumb question, but i can't get a straight answer from anyone knowledgeable about this.
please feel sympathy for me for i do not know.
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Post by Fozzy on Jul 23, 2004 5:04:26 GMT -5
I have asked and heard tell of magical swapping cylinders (even a variation which mention that the noise came from big piston hammering there way into little cylinders, and all such boloney) how does the jake wor k, i am sure that this is a dumb question, but i can't get a straight answer from anyone knowledgeable about this. please feel sympathy for me for i do not know. The principle behind the engine brake is simple. It's a hydraulically operated device that converts a power-producing engine into a power-absorbing retarding mechanism. As you probably know, most truck and car engines have four "stokes" intake, compression, power, exhaust. An engine brake simply removes the power stroke of the engine. 1.The intake valve opens and air is pulled into the cylinders 2. Air is then compressed by the engine's pistons. The drive wheels rotate the engine to compress this air. Near top dead center of the piston?s stroke, the Jake Brake opens the exhaust valves, venting the all of the air and fuel out through the exhaust system (instead of it being allowed to ignite and burn) this removes the ?power stroke? of the engine. 3. On the downward stroke, no power is returned to the engine (and to the driving wheels). The engine is basically turned into a big air compressor. Diesel engines have high compression ratios so they work well to slow trucks down. Remember that the engine brakes are AIDS to slowing the truck..NOT a primary brake.
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Post by ThinkinOnIt on Jul 23, 2004 12:43:21 GMT -5
Thanks, finally a honest engine brake answer. i have heard that some trucks don't even have engine brakes so it would probably be advised to learn driving without them, then its like and added bonus when you do get one in the truck.
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Post by Fozzy on Jul 23, 2004 15:49:56 GMT -5
Thanks, finally a honest engine brake answer. i have heard that some trucks don't even have engine brakes so it would probably be advised to learn driving without them, then its like and added bonus when you do get one in the truck. If you do go through a training program with any of the popular carriers, you may have a bit of trouble learning this skill. Drivers are FAR too reliant on the jakes! A GOOD trainer should work you down a few grades without and WITH a engine brake. This may be near impossible because there are far too many trainers with little to no experience in this. Driving down steep grades without a jake means that you MUST get into and STAY in a VERY low gear and keep the truck slower than you can with a jake! We're talking 20-25 mph MAXIMUM!! If you try and come down the grade at 35-40, you WILL "smoke" your foundation brakes and possibly explode the tires and or set the truck on fire! Slow and steady wins this race! Fozzy
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Post by ThinkinOnIt on Jul 23, 2004 20:02:42 GMT -5
fozzy, It seems to me as though you are not a spring chicken to this industry, so here is another ? for you, my father died because of two thing, a missed gear, and over use of air supply, so here is my ? for you, when he missed the gear, he followed gut instinct and got into his brakes (my mom was watching, she has told me). how did the truck lose the air? all the air lines were intact, did the air compress in the lines, so that there wasn't enough, or could it have leaked out? an investigator who was also a former driver looked the truck over with a fine tooth comb, and found no mechanical damage. the trans was out of gear, and the air was all gone. Even a halfway answer would make me less curious about what killed my dad.
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Post by Fozzy on Jul 23, 2004 22:25:44 GMT -5
fozzy, It seems to me as though you are not a spring chicken to this industry, so here is another ? for you, my father died because of two thing, a missed gear, and over use of air supply, so here is my ? for you, when he missed the gear, he followed gut instinct and got into his brakes (my mom was watching, she has told me). how did the truck lose the air? all the air lines were intact, did the air compress in the lines, so that there wasn't enough, or could it have leaked out? an investigator who was also a former driver looked the truck over with a fine tooth comb, and found no mechanical damage. the trans was out of gear, and the air was all gone. Even a halfway answer would make me less curious about what killed my dad. I really am a bit cautious about even answering this one on the site here...look for a PM....
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Post by Pcuthbert on Sept 7, 2004 11:19:20 GMT -5
Remember that the engine brakes are AIDS to slowing the truck..NOT a primary brake. I must concur here. Engine brakes are the secondary braking system, however they should be the first brake used (when permitted by law). The engine brake does not fade as quickly as do the foundation brakes. Yes it will fade if the engine oil gets hot enough and the oil pressure drops. I do a lot of mountain driving. Up one hill and down the other side. I greatly appreciate the engine brake. Some of the hills I travel are 20 miles in each direction with grades from -1% to 9%. When travelling these hills, speed at the bottom and top are the prime considerations. My loads are 140,000 lbs (63,500 Kg) on 8 axles. There is no real point in running these hills as the speed bleeds off quite quickly when climbing. Find the right gear and climb the hill. Watch the transmission temperature. It will climb quickly. Going down is another matter. At the top of the hill, come to a complete stop. Get out and check your brakes. Do a thorough job. Make sure of adjustment, check for air leaks and the operation of your compressor. Read any signs to be sure of the conditions of the hill. This can help you with gear selection. If you have an 8% grade indicated, take 8 away from your top gear (eg if you have an 18 speed transmission, you will be left with 10. This is the highest gear you should even consider using. It will require full engine brake and full foundation brakes to come to a stop). Release the brakes, and start down the hill. Allow your engine to reach about 1400 RPM in a gear 1 or 2 lower than the one you expect to descend the hill. Engage the engine brake and allow the engine to increase to about 2000 RPM. If the engine brake holds your truck at this speed, then you have made a good choice. If the truck wants to go faster, apply the brakes and downshift. If it is possible, you should descend hills using only the engine brake. This will save your foundation brakes for stopping if needed. Then comes winter and ice. That is a completely different time. Slow down is the best solution here. Keep your engine revs below 1400 to reduce the chances of lockup and use a lower cylender count on the switch. Hope I did not get too long winded; Pat
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Post by truckertom on Sept 12, 2004 13:46:22 GMT -5
What will break drivers from depending on the Jake too much is having a U-joint come flying apart on a %10 downgrade and it is 15 miles to the bottom and they weigh 78,000 lbs.
They don't make that mistake again.....if they survive.
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Post by Pcuthbert on Sept 14, 2004 11:59:40 GMT -5
And that is why you should depend upon the engine brake to keep your speed down on the hills. Hot brakes will not stop you.
At least that way you have enough foundation brake left to come to a stop so that repairs can be made to get you safely on the way again.
But then again, you should have noticed the vibration from the failing U-joint befoe you get into that situation.
When the truck starts shaking, then you have a problem that needs attention immediately.
Pat
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Post by openroad88 on Sept 14, 2004 21:14:54 GMT -5
Pat,
What freight do you typically haul up and down these grades? And what truck do you use?
Any modifications to your rig to help with power and braking?
Joe
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Post by truckertom on Sept 14, 2004 22:01:43 GMT -5
Turning your engine up causes heat, heat causes wear in the engine. Just like heat causes break fade.
What helps you understand the drive train is spending some time working on one. There is nothing like having to change a driveline in a truckstop somwhere up north in the middle of winter. It makes you check your equipment out before you leave.
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Post by Pcuthbert on Sept 14, 2004 22:08:18 GMT -5
Joe;
I drive a 2004 Mack CH 613. 212 inch wheel base. 460 HP Mack engine (2200 lbs/ft max torque) 18 speed Eaton Fuller double over drive. 413 rear end ratio 44,000 lb rating.
I pull a Super-B Fuel train. Fully loaded at 63,500Kg (140,000 lbs).
A full load of Diesel Fuel is about 13,000 gallons or gasoline is 14,500 gallons. Jet Fuel is 13,500 gallons while Av Gas is 15,000 gallons.
My average speed over some of these roads is about 35 MPH.
My company has a speed limit of 56 MPH, which I think is quite adequate for hauling Haz Mats of any type.
My employer is one of the largest bulk carriers in Western Canada runnning liquid, dry, pneumatic and pressure trailers.
Please feel free to ask me any other questions that you may have. I think that forums of this sort are a great place to exchange knowledge and ideas.
I can tell you that it is a rare day that I do not have the opportunity to learn something new, but there are days when I fail to accept that opportunity.
Tom;
I agree with you 100%. Increasing the engine output over the engineered specs is asking for trouble. Maybe not today nor tomorrow, but someday it will catch up with you.
I have spent a goodly number of hours working on trucks in the arctic when something has gone wrong. It can be as simple as going down the road with winter fuel in the tanks when you should have arctic fuel. No problem when you are driving, but when you park the truck for a meal at 50 below, the fuel tanks cool off. Next thing that happens is that the fuel jells on you and you cannot get the truck to run again until you start applying heat to the tanks, fuel lines and fuel pump.
Extremes of temperatures are hard pon equipment, whether it be weather related or from misuse/abuse of the equipment.
Pat
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Post by truckertom on Sept 15, 2004 21:56:24 GMT -5
"Extremes of temperatures are hard on equipment"
We used to plug our trucks in every night to keep them warm. And there were times that was not enough. I have had people dispute this, but there are weather conditions that a diesel just won't run in. Fuel heaters, water heaters......there is a point when it just gets too bad to opperate.
That is why the coffee pot ALWAYS HAS TO WORK! But I admit, I have used the exhaust manifold the heat up my kipper snacks along with my beanie weenies.
If you ever want to scare a new driver, try an air starter! Or better yet don't.
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Post by Pcuthbert on Sept 16, 2004 10:49:31 GMT -5
"there is a point when it just gets too bad to opperate"
You are right here Tom, but then comes that time of "humanity" when the small northern community is almost out of heating fuel, They expect to be clown in by a blizzard and "Someone" just has to get them enough to survive the next week or so.
Every winter, there is a big push in the North West Territories to get fuel and supplies into the diamond and gold mines. The temperatures can be 70 below. The trucks are bundled up like kids in snowsuits to keep them warm. The air tanks each have a quart of alcohol in them to keep the air system from freezing.
The roads are made of ice over the lakes, the speed limit on the ice is 15 MPH to keep from cracking it and letting someone fall through.
The springs are so brittle that you can break them by hitting a bump in the road, the tires are like steel wheels. The fuel starts to cloud at 50 below and will turn to jello at 75 below.
It takes 20 hours driving to make the round trip from Yellowknife to the mine and the paycheck for the trip is about $600. You make 3 trips a week (If the weather holds and you don't get blown in), and the season to do this is 8 weeks long before the roads start to break up.
I have driven over the ice bridge on the Makenzie river with water half way up the fuel tanks because the boss needed one more trip to get the last of the fuel in before the bridge went out, and then come back out later that day and found the route markers (trees stuck in the ice) washed away.
I have video of water flowing over the top of the bumper of a truck crossing behind me. Kind of reminds me of some of those "exciting" commercials produced for recruiting by the US army.
I guess you could really say for trucking "There is no life like it" and really mean it. You could punctuate that quote any way you want, and still be accurate.
My point here is that truck driving is full of challenge. If challenge is what you want, then trucking may be for you.
Pat
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Post by truckertom on Sept 16, 2004 20:55:32 GMT -5
There are some of my students that take off from Texas in Sept. with nothing but summer clothes in their duffle bag.......oh man!
Yes, there is a matter of survival. But it sure helps to plan months ahead. There are drivers going through school right now that have never been north of Kansas before. It is going to be a learning experience for them...
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