| Author | Message | ||
| george bruton (Tazman632000)
Registered Member Username: Tazman632000 Post Number: 58 Registered: 2-2007 Posted From: 65.184.69.36 Rating: N/A |
my 4106 shudders in 1st gear as i let off the clutch also in reverse, engine mounts look ok. will a pressure plate adjustment fix this in most cases? thanks | ||
| Tom Caffrey (Pvcces)
Registered Member Username: Pvcces Post Number: 1177 Registered: 5-2001 Posted From: 65.74.66.116 Rating: N/A |
George, that depends on the cause of the shudder. Ours has some of the same symptom, but it's not very noticeable if I start the coach rolling without using ANY throttle until after the clutch is all the way out. Any side-to-side movement of the powertrain will have the effect of changing the length of the clutch pull rod. I understand that a good many of these coaches have splinesavers installed because of accumulated wear on the clutch shaft spline. I am told that the splinesaver does not have any springs like a regular clutch. We have the splinesaver, and it seems like there's nothing else to do except wait for the clutch to wear out and put in the stock replacement. If you don't have a splinesaver and if you are not using any throttle to get your coach rolling, then you probably will want to get the clutch adjusted according to the procedure in the service manual to see if it helps. For what it's worth. Tom Caffrey PD4106-2576 Suncatcher Ketchikan, Alaska | ||
| Larry D Baker (Lbaker4106)
Registered Member Username: Lbaker4106 Post Number: 75 Registered: 5-2005 Posted From: 207.69.137.7 Rating: N/A |
Mine has done that ever sense I purchased it 5 years ago. We us it all year. Larry | ||
| john w. roan (Chessie4905)
Registered Member Username: Chessie4905 Post Number: 923 Registered: 10-2003 Posted From: 71.58.48.5  Rating: N/A |
To Fix this could require: With a dial indicator, check the runout on the flywheel to crankshaft mating surface; have flywheel surfaced to remove rough surface and hard spots on surface from slipping clutch at times and causing spots to harden, just like on brake drums; check and/ or surface or replace pressure plate and replace clutch disc. | ||
| Tom Connolly (Tomconnolly)
Registered Member Username: Tomconnolly Post Number: 51 Registered: 9-2003 Posted From: 71.122.87.245 Rating: N/A |
1) Do not use throttle until after the clutch is all the way out! 2) Replace the upper and lower rear radius rod bushings. | ||
| john w. roan (Chessie4905)
Registered Member Username: Chessie4905 Post Number: 939 Registered: 10-2003 Posted From: 71.58.48.5 Rating: N/A |
Good point Tom!The trouble with the rod bushings is, they look ok and can still be bad. So many coaches have never had any replaced. And the bushings aren't expensive, just a lot of work to change if you haven't the required tools and equipment.Previous experience at changing them definitely helps. Personally. I'd do them first before I did the clutch work. Once they're done, they'll never need to be done again. | ||
| Gus Causbie (Gusc)
Registered Member Username: Gusc Post Number: 621 Registered: 11-2005 Posted From: 208.54.200.208  Rating: |
If you are getting any oil on the clutch it will shudder. Please note the above posts about letting out the clutch only at idle and ensuring your clutch system of rods is correctly adjusted. Also you may have worn out linkage rods and pins. | ||
| Tim Brandt (Timb)
Registered Member Username: Timb Post Number: 141 Registered: 10-2003 Posted From: 66.165.176.60  Rating: N/A |
THis brings up a question I have. I am assuming you can only release the clutch at idle if on a level surface correct? I have tried unsucesfully on an incline....will stall without some throttle | ||
| Tom Caffrey (Pvcces)
Registered Member Username: Pvcces Post Number: 1178 Registered: 5-2001 Posted From: 65.74.66.116 Rating: N/A |
Tim, ours will handle some incline, at least 5%. But we have another out. If we are dumb enough to get caught where the idle doesn't have enough torque, the fast idle will get us rolling at almost full torque without shuddlering. No problem at all. We do not have the switch that would shut off the fast idle on the handbrake and the fast idle is in the neighborhood of 1000 rpm. The engine is rated for more than 90% of maximum torque at that speed, which means we can get rolling even on a 15% upgrade. One other thing; before I try that, I try to figure out if I can roll backwards to get to a better spot. I try to plan my stops the same way. If I seem shy about using the fast idle, it's because the clutch slip time is very short before it gets cooked. If, for any reason, I don't make it on the first try, I wait a bit for the heat to travel into the iron in the clutch before trying again. It's really not a problem if things are adjusted and working right. Tom Caffrey PD4106-2576 Suncatcher Ketchikan, Alaska | ||
| Tim Brandt (Timb)
Registered Member Username: Timb Post Number: 142 Registered: 10-2003 Posted From: 74.244.14.221 Rating: N/A |
Thanks Tom. I don't have a fast idle switch but I do have a tach so that's good info. There are a lot of exits here in GA with an incline at the stop light so those are the places I have run up against. I may also be releasing the clutch too quick not wanting to roll back on top of someone behind me. Time for more practice  | ||
| Jim Wilke (Jim Bob) (Pd41044039)
Registered Member Username: Pd41044039 Post Number: 270 Registered: 2-2001 Posted From: 69.77.156.137 Rating: N/A |
Tim, I think you have an inline 6-71, right? When we got our 4104, the engine had very little "grunt" at low RPMs. It would stall if we didn't rev it up good on takeoff. When I got "Da Book" as Fast Fred says, and properly adjusted the governor, valves & fuel injector rack the engine would respond to letting the clutch out by increased power without touching the throttle. It would "grunt". It also will hunt for maybe 20-30 seconds when started cold. If it does not do both of these then the governor is not right. That said, we often must use some throttle when stopped on a moderate incline. Maybe a sign on your back bumper "Caution: This vehicle rolls back on takeoff!" might keep the Kias off your tail. BTW, nice work on your renovation!! | ||
| Tim Brandt (Timb)
Registered Member Username: Timb Post Number: 143 Registered: 10-2003 Posted From: 66.165.176.60 Rating: N/A |
Thanks Jim. Yes I have an inline 6-71 with a 4 valve head. Whenever the engine is at idle warm or cold it kind of rolls between 500-700. I noticed the jake buffer switch does not actuate when at idle so I think it may be out of adjustment and causing the rolling idle. I drove her to work today just to get alittle more practice and see if I can figure the technique out. | ||
| George M. Todd (George_mc6)
Registered Member Username: George_mc6 Post Number: 386 Registered: 8-2006 Posted From: 207.231.75.253 Rating: N/A |
Tim, The whole purpose of the Jake buffer switch is to prevent Jake operation when the fuel rack is ANYWHWERE out of the no fuel position. No fuel position of the rack only occurs when the engine is being turned by the driveline at a higher speed than the throttle setting, or during shutdown. If the Jake is energized on an idling engine, you will get a little noise, a cloud of black smoke, and an instant death. (The governor will try to keep the engine running by adding fuel, which will be immediately thrown out into the exhaust manifold when the Jake opens the exhaust valve at the top of the power stroke.) IMNSHO, and I have the same trans, just with a bigger engine and bus, a closed throttle start is not practical in everyday driving. Lets stop and think about something for a minute, OK? Closed throttle start, we finally get going, clutch is fully engaged, engine is now turning 600-700 RPM, and you add throttle to get going. If 700 RPM with a lot of throttle on isn't lugging an engine, I don't know what is. I'm not saying to wind heck out of it and slip the clutch 'til it smokes either, but sure don't try and lug it off from a start just because somebody published an article on it! This is really going to stir things, but I'm not going to pour a lot of throttle on my engine at 700 RPM period. George | ||
| george bruton (Tazman632000)
Registered Member Username: Tazman632000 Post Number: 59 Registered: 2-2007 Posted From: 65.184.69.36 Rating: N/A |
IM GOING TO try the radius rod bushings,ive still got a little steering wander at higher speed even after all the front end repair alignment etc. i always use the dead throttle start, bus i havent got myself caught on a incline yet. i was thinking i could use the icc valve to hold the coach on an incline then start engaging the clutch then quickly release it to get going, does anyone use that method? | ||
| Tom Caffrey (Pvcces)
Registered Member Username: Pvcces Post Number: 1179 Registered: 5-2001 Posted From: 65.74.66.116 Rating: N/A |
George Todd, maybe what you're talking about is why the coaches use such late timing and low idle RPM. If I recall correctly, the 8V71 is supposed to drop down to something like 450 RPM to engage the A/C clutch. And then, there is the governor. It's ability to deal with light loads is like none other that I have had experience with. When used at low RPM, it seems to be a variable torque governor and when used at high RPM, it seems to be a variable speed governor. It seems very well suited for the work. Before I got into being a busnut, I used to think like you do, George. I thought that the four speed stick was going to be a royal pain, and I didn't see how to keep from lugging the engine. We have had several engines of different kinds, and found that lugging would producing head leakage almost immediately, and the torque that a Cummins PT system would produce at a low idle was enough to make me very cautious about lugging. Then, I got some time on the bus engine. I don't worry about it at all, anymore, and I've been stuck on mountain grades by contruction delays, and I've even spent some time in LA rush hour traffic jams. I wouldn't have any of the other combinations that I've driven before, in a bus. They wouldn't make sense. And with truck gears, it's real easy to get stuck on a grade in first gear and not be able to shift. I don't know that the governor and timing on a 4104 engine are as suitable as the 4106 combination is, but with 70 mph gears, I wouldn't be surprised if it works pretty well. These rigs have seen an awful lot of service for them to be a bad setup. Tom Caffrey PD4106-2576 Suncatcher Ketchikan, Alaska | ||
| RJ Long (Rjlong)
Registered Member Username: Rjlong Post Number: 1366 Registered: 12-2000 Posted From: 67.181.166.160  Rating: N/A |
All - Slight incline starting tip: Air brakes have a slight delay when being released - use that to your advantage: Bring the clutch up to just under the take-up point. Make a full service brake application (right to the floor), release, begin to let out clutch and come on the throttle at the same time. With a little practice, you can walk it away from a stop on a hill almost as smoothly as from the flat and level. But it takes practice!! Lots of it!! Mr. Todd - The beast you have (MC-6) is a whole different ballgame than the light GMCs, so it requires a slightly different technique, but conceptually similar. As you well know, too much throttle will smoke the clutch. Obviously, you have to find that balance point between engine rpm and clutch take-up to provide a smooth start without stalling or smoking. And if you re-read what I've said about dead-throttle starts, I do NOT advocate giving the coach full-throttle once you get it rolling off idle. Just like I don NOT advocate "dumping the clutch" like so many truckers seem to do. You feed the powertrain fuel just like you would in any other gearchange - increasing the amount of throttle as the engine rpm climbs. (Unless, of course, you're a transit driver - they only know "flat-on-the-floor"!!) The whole concept behind dead-throttle starts is to get the operator to focus on driving SMOOTHLY, as well as prolonging the life of the equipment. FWIW & HTH. . . | ||
| George M. Todd (George_mc6)
Registered Member Username: George_mc6 Post Number: 387 Registered: 8-2006 Posted From: 207.231.75.253 Rating: N/A |
Tom, I don't see what you get out of promoting dead throttle starts, or using the fast idle instead of the throttle, then you say "If we are dumb enough to get caught where the fast idle won't give us enough torque..." then "I try to figure out if I can roll backwards to get to a better spot..." Its your bus, and you are welcome to drive it anyway you want. When I have to stop in traffic, and the light turns green, I am going to apply throttle, ease off the clutch, not roll back, not get honked at, drive off, and be gone, without worrying about the grade where I stop. You mention using fast idle, and the fact that "fast idle is about 1000 rpm, which is near maximum torque speed of 1200 rpm." Apparently what you don't understand is that maximum torque output is at full fuel rack position, which is only obtainable by having the governor throttle lever in the full speed position! The fast idle solenoid works on the end of the fuel rack, and only moves the rack a very small pre-set amount, and will only produce 1000 rpm under essentially no load, and less than 10% of total horsepower. Not to mention that fast idle isn't operable on MOST DD3 equipped buses unless the parking brake is applied, and of course it drops out when the parking brake is released. RJ, you are exactly right, this thing of mine is big and heavy. Even the "buzzin dozen" won't start it moving on level ground at idle in less than a minute, and only with a lot of very careful slipping. Its just too easy to put on some power, ease off the clutch, and away we go. Start this way, the engine is up above idle speed when you apply more power, so no lugging. Tom's throwing a Cummins into this has nothing to do with it, they don't like being lugged either. Fortunately, we can all drive our busses as we wish... George Todd MC6-7827 Auburn, California | ||
| Gus Causbie (Gusc)
Registered Member Username: Gusc Post Number: 623 Registered: 11-2005 Posted From: 208.54.200.187 Rating: N/A |
Tim, The 671 rolls at idle but you shouldn't leave it at idle except for very short times. I always move my hand throttle up to fast idle anytime it is going to be sitting more than a minute or two at a stop light. | ||
| FAST FRED (Fast_fred)
Registered Member Username: Fast_fred Post Number: 271 Registered: 10-2006 Posted From: 66.90.229.224 Rating: N/A |
MC6-7827 Stick a 12V71 back in and see the difference! FF | ||
| George M. Todd (George_mc6)
Registered Member Username: George_mc6 Post Number: 388 Registered: 8-2006 Posted From: 207.231.75.253 Rating: N/A |
FF, The 12V71 with the 8844 is exactly what I am talking about! My whole point in this is that it doesn't matter what brand of coach, whether the engine is crosswise or straight, or whether it has six, eight, or twelve cylinders, a "no throttle start" is lugging the engine. I am personally unable to understand why someone would suggest the way to drive their bus is to "find a place where I can roll back," and "if we are dumb enough to get caught where the idle doesn't have enough torque... the fast idle will get us out." Well, OK, but as I said last night, that won't work on any brand of bus with DD3s. I also said that "he could drive his bus any way he chooses," and I'm sticking with it! I also question why, with a driveshaft/handbrake bus, that he doesn't do as RJ suggested right above, and "take up on the clutch until there is some engagement, and then apply some throttle..." release the handbrake and proceed. The power to weight ratio of a 4104 with a 671 is close to an MC6 with a 12V71, while a 4106 with an 8V71 has a higher power to weight ratio. Both of the GM coaches have a higher numerical ratio differential, and smaller wheels and tires than the MC6, which makes them easier to start, and lowers their top speed. I hope my explanation of the operation of the fast idle cylinder's action on the fuel rack is clear, that the fast idle CANNOT increase fuel injection rate as load is increased. It is exactly what it says it is, FAST IDLE. FF, please note the similarities between the HP and torque of a 12V71, and an 8V92T, and rest assured that I did not remove the V12 just for kicks! Then look at the length and weight difference between the two, and you'll figure out why the change was made! Regards, George | ||
| Gus Causbie (Gusc)
Registered Member Username: Gusc Post Number: 625 Registered: 11-2005 Posted From: 208.54.200.190 Rating: N/A |
George, I'm not sure why you think an idle start is lugging. As you probably well know all trucks do this and I presumed all busses as well. Idle starts in my 4104 are gentle as anything and not anywhere near lugging. Maybe monster busses are different but I would assume that their much larger engines compensate for this. High RPMs by a diesel from a stop will burn clutches. This is probably the very first thing I was taught about driving a big truck. | ||
| George M. Todd (George_mc6)
Registered Member Username: George_mc6 Post Number: 389 Registered: 8-2006 Posted From: 207.231.75.253 Rating: N/A |
Gus, I am reasonably certain that the second thing you were taught about driving a big truck was to down shift it long before the engine reached 600 rpm. A" no throttle start" makes the engine start the bus at IDLE speed, period. If that isn't lugging an engine, I don't know what is! Four posts above, you said "I don't let my engine idle... I always move my hand throttle to fast idle...if more than a minute or two at a light." In my post of 3/20 550pm, please read where I said "I'm not saying wind heck out of it and slip the clutch 'til it smokes either.." I have owned my bus since 1986, and it has been all over the Western US and Canada, and it has the same clutch, trans, and u joints in it that were in it when I bought it, so I can't be abusing it too much. Everybody says "keep the rpms up while climbing hills," and then advocates dead throttle starts. I give up, I don't worry about stopping on grades, or stopping where I can't roll back so I can make a dead throttle start either. I haven't posted that an 8V71 drops to 450 rpm to engage the A/C compressor either!!!! I would REALLY like to see that one believably explained to MY mechanical governor! Sorry to pick on you, Gus, and for the last time, the beauty of this affliction is that we can all drive our busses any way we please. Regards, George | ||
| Buswarrior (Buswarrior)
Registered Member Username: Buswarrior Post Number: 1225 Registered: 12-2000 Posted From: 76.68.132.196  Rating: N/A |
Hello. The term "lugging" is being misused here. "Lugging" refers to operating the engine under load and grade conditions in which the engine is at full fuel, the vehicle is unable to increase speed, usually speed is dropping, and the revs are dropping through the peak torque point, and down the backside of the torque curve. The mechanical DD 2 strokes did not like being operated like this, made lots of damaging heat under these conditions, as the fuel delivery system just keeps pouring max fuel into the cylinders. And the DD didn't make a lot of power in the lower revs anyway, so the popular instruction to drivers was to grab the next gear down as soon as the speed drops far enough to do so, and rev the crap out of it climbing hills. Problem solved without a big explanation that the talker was pretending to understand, never mind the listener having a hope...! A dead throttle start is not abusive to the engine, as there is not the massive fuel delivery to create the damaging heat inside the engine, and the vehicle is not being held back from moving by load or grade. Many, many drivers of manual transmissions, both heavy and light, apply far more revolutions to the engine when attempting to start off the vehicle than they should. In a car, with its light weight, you get away with this aid to sloppy clutch pedal work far longer than with a bus or truck. It is the heat generated by slipping the clutch that is damaging, but from a conceptual standpoint, think of engaging the clutch like feeding material into a bench grinder hard enough to make it stop spinning . The faster the grinder is spinning, the more material being removed, and the more heat being generated, before you can get it to stop. You have to push material into the grinder to get it to stop, so the only avenue of efficiency you have is to keep the grinder speed as low as possible. Heat is our real enemy, being the bigger threat to abrupt clutch failure, than wear, but you get the point. In a heavy vehicle with a diesel engine, the delivery of power at idle is stronger than in a gasoline powered car, and the first gear ratio is mostly more favourable to getting it to roll, GM's being a little less so. Speeding the engine up and slipping the clutch to get it moving is not as sustainable a practice in a heavy vehicle as it is in a car, and with the power and gear ratio available, unnecessary for most starts. Part of the problem stems from Car makers make a tall first gear because they think the dumb one buying and driving it will think having to shift in a few feet to second makes the whole car bad, and harms the mythical 0 to 60 times... So, car drivers may be arriving conditioned to ad fuel to take off... And then there is the training problem... Did whoever taught them to drive manual...know themselves the damage that the heat created by slipping the clutch against raised engine revs will cause? Doubtful. The modern electronic engines are designed to be safely and fuel efficiently operated at lower revs, and the electronics modify the fuel input to match operating conditions. In short, the computer won't allow the fuel delivery system to dynamite the engine like the mechanical ones did, if the driver ignores the conditions and tries to top the mountain without another shift. happy coaching! buswarrior | ||
| Gus Causbie (Gusc)
Registered Member Username: Gusc Post Number: 626 Registered: 11-2005 Posted From: 208.54.200.30 Rating: N/A |
Again, nothing I said I do lugs the engine. A diesel develops high torque at idle unlike a gasoline engine, this is the reason for burned out diesel clutches. If you start from idle with a gas engine it will stall unless you are in a low under gear. Starting at idle from a dead stop is not lugging. If you lug a DD at idle it will usually stall. If these manual buses had lower first gears they would start easily from a stop on a hill. Idling a DD at higher rpms has nothing to do with starting out at idle. I haven't read any post that said anyone uses high throttle settings from a stop? How did this ever come up? | ||
| Tom Caffrey (Pvcces)
Registered Member Username: Pvcces Post Number: 1180 Registered: 5-2001 Posted From: 65.74.66.116 Rating: N/A |
George has just got the governor wrong! For what it's worth. Tom Caffrey PD4106-2576 Suncatcher Ketchikan, Alaska | ||
| George M. Todd (George_mc6)
Registered Member Username: George_mc6 Post Number: 390 Registered: 8-2006 Posted From: 207.231.75.253 Rating: N/A |
OK Tom, If I've got it wrong, enlighten me and everyone else! Before you start, remember that we can all go out and look at our engines, and see that the fast idle cylinder is down on the side of the vee, and has nothing to do with the throttle linkage. If the engine is equipped with fast idle and Jake brake, the shaft is concentric, with one allowing the buffer to feel the rack, the other to push on the rack. We all know that the fast idle cylinder moves the rack a small set amount, and has no knowledge of engine speed or load. So, I really want to know how the fast idle can produce almost full torque {without full fuel/with fast idle fuel} as you say. Don't go off the subject, and while you're at it, explain to us all how the "idle speed is dropped on an 8V71 to engage the A/C compressor" as you say. We're waiting. George | ||
| Don Evans (Doninwa)
Registered Member Username: Doninwa Post Number: 108 Registered: 1-2007 Posted From: 66.45.175.118  Rating: N/A |
A question or two. Is the governor trying to maintain RPM when making a dead throttle start? It seems so when I start rolling from my back yard where the tires tend to sink in a bit. On hard level ground DTS is no problem, smooth and easy. But then I don't gross 40K either. I was told by a old charter operator that on his 4106s that the AC would not engage above a certain oil pressure (idle) to prevent twisting off the compressor shaft if engaged at high RPM. True? Don 4107 | ||
| FAST FRED (Fast_fred)
Registered Member Username: Fast_fred Post Number: 272 Registered: 10-2006 Posted From: 66.90.226.182 Rating: N/A |
I was told by a old charter operator that on his 4106s that the AC would not engage above a certain oil pressure (idle) to prevent twisting off the compressor shaft if engaged at high RPM. True? Seems so, the idle on the older coaches is 400 rpm or so in Da Book. This was because the oil low pressure light was a REQUIREMENT for the air cond clutch to engage. 400rpm gives under 5psi oil, so the protection is automatic and seamless. Wasn't a few square blocks of engineers with pocket protectors GRAND at simple? FF | ||
| George M. Todd (George_mc6)
Registered Member Username: George_mc6 Post Number: 393 Registered: 8-2006 Posted From: 207.231.75.253 Rating: N/A |
Don, The answer to your first question is ABSOLUTELY. The governor alway attempts to maintain its speed setting. As information, to help clear up some of the misinformation above, that's why the governor has a drive, so it knows what speed the engine is turning. It obediently looks at the throttle setting, and the engine speed, and "decides" how far to move the fuel racks to keep that speed. Fast idle is entirely different. The fast idle air cylinder pushes the fuel rack open a couple of millimeters more than where the governor was holding it at normal idle. As this cylinder has none of the drives, weights, springs or hydraulics that the governor has, it can only move the rack a little ways, and stay there. So, when the A/C comes on, or the air compressor loads, you will see an engine in fast idle slow down, due to the added load. I'm not a GM owner, so I will let the qualified people speak on GM air conditioning. Regards George | ||
| Tom Caffrey (Pvcces)
Registered Member Username: Pvcces Post Number: 1182 Registered: 5-2001 Posted From: 65.74.66.116 Rating: N/A |
George, the governor has never behaved as you described on fast idle. If the engine is slowed, it has greatly increased the fuel AND done it smoothly, just as I described. If the rack was moved and held in a fixed position, as you described, that would be a prescription for a runaway. At this point, I would have to guess that your governor is designed differently that the one that we have. For anyone really curious, a little testing will go a long way in giving answers. For what it's worth. Tom Caffrey PD4106-2576 Suncatcher Ketchikan, Alaska | ||
| Buswarrior (Buswarrior)
Registered Member Username: Buswarrior Post Number: 1229 Registered: 12-2000 Posted From: 76.68.122.211 Rating: N/A |
Perhaps the use of words is the trouble here. My fast idle acts against the throttle linkage, in effect advancing the throttle slightly, allowing the inner workings of the governor to do their thing the same way they do if I squeeze the throttle pedal a little. The governor messes with how far or not the "rack" advances the fuel delivery to the cylinders. There are a lot of us who would benefit from seeing what really happens at the injector as we drive. You might be surprised under what conditions the fuel delivery to the cylinders has been backed off or advanced by the governor, in relation to throttle setting, and engine RPM. happy coaching! buswarrior | ||
| George M. Todd (George_mc6)
Registered Member Username: George_mc6 Post Number: 397 Registered: 8-2006 Posted From: 207.231.75.253 Rating: N/A |
BW, You are so right! But neither your bus nor mine can be started with fast idle as proposed above, because the DD3s won't allow it. AND, what is the difference between stepping on the throttle a little to start the bus, and disconnecting all of the fast idle safeties hooked to the DD3s just to start the bus moving with fast idle? The answer is just as you said, NONE. The governor is going to move the fuel rack where it needs to be to maintain the engine speed setting, period. Having worked for a railroad for over 42 years, I have seen six locomotive manufacturers make six different styles of fuel racks, which all couple a Woodward governor to a bunch of injectors. (Alco did use a GE governor for a while.) Anyhow, all of the later engines have a load regulator controlled by the governor, which is visible, as well as the fuel linkage. This makes troubleshooting easy, when the engine is not producing enough power, the rack, and the manual lever will be all the way in, and the load regulator will be toward minimum field. If the locomotive has an electrical problem, the rack will be just a little ways out of idle, the engine going 900 rpm, and the load regulator will be against the maximum peg, trying to get the generator to load, which it can't due to some electrical problem. OOh I got carried away this time, sorry! But BW is right, the rack and your foot are not connected. George | ||
| RJ Long (Rjlong)
Registered Member Username: Rjlong Post Number: 1368 Registered: 12-2000 Posted From: 67.181.166.160 Rating: N/A |
George - On my 4106, which doesn't have DD3s or spring brakes, the fast idle is tied into an under-floor switch on the "johnson bar" handbrake mechanism. If the adjustment is off, a pull small enough to activate the fast idle may be too little to engage the parking brake. This could be what allows Tom to use, in essence, a dead throttle start with the fast idle on with his 4106. I totally agree that this would not work with DD3 or spring brakes, since the fast idle is integrated into the air circuits controlling these brakes. FWIW & HTH. . . | ||
| George M. Todd (George_mc6)
Registered Member Username: George_mc6 Post Number: 398 Registered: 8-2006 Posted From: 207.231.75.253 Rating: N/A |
RJ, I hear you, and I agree with you, and of course you can see what BW posted right above. Now, please remember that what got all of this started was my post about Tom's comments "If we are dumb enough to get caught where the idle doesn't have enough torque, the fast idle will get us rolling at almost full torque...I try to figure out if I can roll backwards...I try to plan my stops the same way." There was also a later post which said "fast idle is 1000 rpm, and as full torque output is at 1200 rpm, I get almost full torque out of fast idle." I disagreed with that statement, AND I EXPLAINED WHY, which is important. With BW's help, I think it is clear to everyone who didn't understand that full torque can only be obtained at full throttle at 1200 RPM, not at fast idle. So, I will now ask this question: What is the difference in the FUEL RACK position between applying 1000 rpm of throttle and engaging the clutch gently, and 1000 rpm of fast idle setting, (with the parking brake interlock nullified) and engaging the clutch gently??? The answer is................NONE! The fuel rack position is the actual amount of power the engine is producing, regardless of how the governor is being told to produce it. Bottom line of this, is that I drive my bus to enjoy it. We have all discussed what part of the bussing experience we like best. Some of us think getting "THERE" is important, while others feel being "THERE" is of utmost importance. Then, is "THERE" a dry campground in the boonies where you want to sit for a week and be comfortable, or an RV park with a 50 AMP hookup? Personally, I like to travel, so I chose a bus that has power, and I left the OTR air in so we are comfortable OTR. I also have lots of bay space, so I have lots of water and battery capacity. Nobody in this thread has questioned why someone would "plan my stops so I can roll back, and if I'm dumb enough to get caught where fast idle won't start it" and post it as a way for someone else to drive their bus! Well, I hope he keeps a notebook, because the way I understand bus affliction, is that after about 200 documented dead throttle starts, 175 documented fast-idle starts, and 75 measured roll-backs of at least 200 feet, (with the co-pilot out back flagging traffic) the tooth fairy will come down and leave him a reward under his pillow! If I told my wife to "go back and get everybody out of the way so I can roll the bus back," (instead of putting on some throttle and getting the heck out of there) she would suggest that I go back and wave, while she drove the bus. Most everyone has figured out by now that about the time I got to the rear of the bus, she would have it in gear, and have gone off and left the box of rocks standing behind! We all know how to start a stick shift on a hill using the handbrake, and we agree, that won't work on any bus equipped with DD3s or Maxis. AS I have said several times here, it is his bus, and he can drive it as he pleases. Obviously, his proposed method won't work on the vast majority of buses out there, but he's welcome to do what he wants as long as it makes him feel good! George |
