1. #1
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    Default Jumping out of pump gear

    http://cms.firehouse.com/content/art...Id=45&id=45884

    This truck can most likely be saved, rebuild the engine and change some fluids.
    this rig is an International / U.S.Tanker.

    we have a neighboring dept/city which had a brand new Ferrara / HME do this in front of the station. It went across the steet, thru the ditch and high centered on the railroad tracks.

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    Default "Jumping" out of pump gear???

    The issue of a pumper "jumping out of pump gear" has made no sense to me for many years. As a volunteer firefighter for 35+ years and a career firefighter for 25+ years, I have never seen this happen, nor have I heard of it actually happening anywhere near here. I am aware of situations where the operator didn't properly perform the shift, and failed to ensure the 3 NFPA required green lights were lit. Upon throttling up, the engine torque overcame the parking brakes and caused the truck to move. Fortunately, the operator hit the red botton on the throttle and controlled the situation.

    By understanding the mechanics of a pump shift, I fail to understand how a truck could "jump" out of pump into road. I would like to hear from apparatus mechanics about their experience with this issue. If this is really possible, tell me how. Otherwise, we need to ensure our operators are trained properly and that they follow prescribed steps to ensure the shift has taken place properly. Trucks on railroad tracks or in lakes don't do the public much good........

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    Our neighboring brothers had a truck they brought over on a mutual aid woods fire. Personally watched the truck lunge/buck and the operator hit the emergency throttle and jumped in the cab. The operator said that it was the second time that it had done that very thing. It was sent off the next day.
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    Talking Jumping Out of Gear

    While never having this happen to me personaly. I can guess that one of two things happened 1 This is doubtfull, the pumpshift was improperly adjusted and wasn't fully engaging. 2 The most probably and the easiest to fix. In 21 years of emergency services I have met many people that put an air operated pump shift back to the middle of the throw after engaging it. The first time I heard this I was astonished. I was always taught the shift once moved to pump should be left there, this is a "positive" lock to ensure the pump is no longer in road. I have heard of this problem with two manufacturers. I am sure there is an explanation. I am very glad no one is injured. It would also be interesting to see which size wheel chocks were used.
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    Fyrtks: could you elaborate a bit? I was always taught to put the truck in N, go from road , to the middle, then to pump, then put the truck in gear. Are you saying that you put the selector back in the middle after switching to pump??

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    I can help i think. You are correct when putting truck in nuetrual, then shifting the pump waiting for green light and then placing the truck back into drive. I too have heard of FD doing these steps but after getting the first green light shifting the pump into the center or neutral postion. Then placing the truck transmission into drive. The green lights will light up and the pump will turn. By placing the pump back into neutral, the postive pressure against the disc that holds the gear into pump mode is not being held. The only thing holding it is friction from the turning gears. If it were to slip back to road gear i would imagine the grinding noise would be deafing. I hope this clears up you question. Jeff

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    More than likely the brakes just released. With tha advent in current apparatus anyone who has been around one that someone had mistakenly taken it from pump to road before the speedometer went to zero and the sound that came from that mistake.... If you did it once, you never wanted to hear it again...

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    Exclamation It happen to .......

    Had it happen on an vehicle fire on a interstate. We where first in pulled a line off, when I increased pressure the truck pumped for about 2 mins then started to roll foward. We did not hit anything and it only went about 4 ft. My cat like reflexes to control ( OK the OH CRAP) toook control and I moved really fast to the cab. We had been having problems engaging the pump for about 2 days when this happen. It went to the shop and we have not had a problem since. But that is the only time it has happen to me. Now I have seen when the driver has not engaged the pump and throttled up and the truck has moved foward, seen that more then once.
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    Default jump

    As a mechanic for our dept and now shop foreman for almost 19 years with twenty years doing the same in the USAF, I can bet that if it isn't operator error in ensuring full pump gear engagement then it is a mechanical malfunction. I have seen misadjusted or out of adjustment indicator light switches and in the old days shift forks and gears that would not keep the pump engagement due to excessive wear. The first signs of trouble should send it immediatley to the shop for inspection. Keep it safe.

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    Content deleted by author.
    Last edited by Firefighter807; 07-08-2009 at 07:04 PM.

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    You guys are forgetting one thing: Pump and Roll trucks.

    A pump and roll truck is pumped in NEUTRAL because the pump is pulled via PTO from the transmission, before the driveline. Thus the ability to drive and pump at the same time. We have a split gearbox pump (pump in drive in pump mode) and a pump-and-roll truck (pump in neutral). I have seen this with my own eyes... guys get in this thing, put it in pump, hear the pump start spinning (its old and loud), then put the transmission in 3-6 (basically drive - I have no idea why they do this - they have already heard the pump start to spin), FEEL THE TRUCK SHUDDER AS IT PULLS AGAINST THE PARKING BRAKES, get out, and start to throttle up. I have seen this twice with the same person (no longer here :-D). In that situation its only a matter of time until the brakes don't hold any more. Its entirely possible that if drafting, he wasn't throttled all that high, so he probably had more time before it happened.

    Again I'm not saying thats the sort of setup it was, just adding another possibility into the mix.

    Jon
    Last edited by chiefeng7; 11-22-2005 at 08:05 AM.

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    We had an issue with something similar during a training session for drafting. LVWRENCH, you may remember my past post. Short & Sweet of it:
    1. Operator somehow managed to leave the pump-shift in the "neutral" position. (In between pump & road)
    2. As the truck was throttled up (slowly) it was noticed that the pump panel "pump engaged" light was not on and the truck was "straining against the wheel chock.
    3. Operator climbed back into the cab and found that the pump shift was improperly set.
    4. The attempt was made to get the truck into pump. It would not do so.
    The pump shift shaft would not come out of road and the "Automatic" tranmission selector did not register the gear that the truck was in.
    5. Several attempts to get the truck out of road and into pump, including putting the pump shift back into the "neutral" position and trying to manually engage the shaft, did not work.
    6. We dug the wheel chock out of the dirt road we were on and drove the truck back to the station. (still no indication as to what gear the truck was in. It would'nt even go into reverse)
    7. We drove the truck into the station head first just in case it had to be towed, and shut it off.
    8. Restarted it and all items returned to normal.

    Evidently, all we can figure is that something to do with the computer would not let us correct the problem. It was confused. (hence refering to a previous thread of the "benefit" of electronics on fire engines)

    So, although "Operator Error" seemed to start the problem, the "Brain" would not let us fix it. (until we found out that it would default back to normal after shutting the truck down)

    We did not cross any railroad tracks, rip a hydrant out of the ground, put the truck into a pond, or, thank God, hurt anybody. But, in 33 years of this business, I never saw any operator error or electrical snafu with the old "pull & turn" air operated pump shifts.

    So, as mentioned: Train, Train, Train!! But beware, people still make mistakes.

    P.S. Every newer model truck we have bought since 1986 has enough engine power to override the Maxi's. The "good ol trucks" would stall!

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    chiefeng7, you beat me to the punch, there is no way a hale split shaft could "jump" into road gear once properly engaged into pump. The noise would be defening and something big and metal would drop onto the ground. Pump and roll trucks, however... that's definitely possible, especially with automatic tranny's, although something would have to push the shifter into gear. I am not familiar enough with Waterous pumps to say difinitely, but if you understand how a split shaft transfer case works, there is no way to be in pump and to then shift into road. It has to be operator error.
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    Where were your chock blocks. If it did shift out of pump and into road gear your chock blocks would have stoped it

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    The chock that will stop a throttled up 15ton plus pumper does NOT exist. Lightly throttled trucks in road gear will easily overrun a standard issue chock.Outside of mechanical malfunction,I'd rate operator error as the primary cause of this issue. T.C.

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    A 30 ton tanker with a 400hp engine will overpower the parking brakes with the throttle cranked up. Point of caution, if you forget to put the truck in neutral and the load manager decides it's time to idle up to increase alternator output, the truck will drive away on it's own regardless of the parking brake being set.

    A wheel chock is to stop the truck from rolling. They don't stop the truck from driving away. In fact, the wheel chock will tend to become a projectile after it is launched out from under the wheel.

    I'm not familiar with the workings of the air operated pump shift. I'm assuming it applies pressure to go from road to pump. Is it therefore possible that a loss of pressure would make it go back to road? If that is the case, then I suppose a failure of an air line could result in it going back to road? Drawing at straws here.
    Even the burger-flippers at McDonald's probably have some McWackers.

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    From nmfire:
    Point of caution, if you forget to put the truck in neutral and the load manager decides it's time to idle up to increase alternator output, the truck will drive away on it's own regardless of the parking brake being set.


    All load managers should be interlocked with the neutral saftey switch and the parking brake. This is done to keep the truck from going out of control.

    If your truck does not have these interlocks please see a dealer or service center to have these safety items added.

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    Well I know ours doesn't have that feature. When I was told this happened, the first thing i said was "Doesn't the load manager only work in Neutral?"
    Even the burger-flippers at McDonald's probably have some McWackers.

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    Quote Originally Posted by nmfire
    I'm not familiar with the workings of the air operated pump shift. I'm assuming it applies pressure to go from road to pump. Is it therefore possible that a loss of pressure would make it go back to road? If that is the case, then I suppose a failure of an air line could result in it going back to road? Drawing at straws here.
    Think of a manual transmission. When you put it in 3rd it stays in 3rd. When you put it in 4th it stays in 4th. A pump transmission is the same thing only instead of 3rd and 4th we have pump and road. The acutator is a double acting air cylinder that continues to apply pressure whichever direction is selected as well. (Or in the case of electric Waterous, a motor winds a spring to hold it that way.) A loss of air pressure should not result in any change in shifter position. There is no spring to push the shift rod one way or another and there are detents to hold it in whatever position it is in.

    Birken

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    OK, best way to explain this is with a picture, since I don't have my Hale manual at home with me I drew a simple example of a transfer case.

    You are looking through the transfer case from the driver's side.

    Input shaft from tranny is red. Output shaft to differential is green. Both have splines on them which match up. The shift collar is blue, and in this drawing is in "road" where it links both shafts. The collar is cut to match the splines of the input and output shaft, all the power of the engine goes through this collar while its in road. When you shift to "pump" the air shifter pulls the collar forward (to the left) to the point where the two shafts are not linked any more and the teeth on the outside of the collar now mesh with the orange pump drive gear above it. Now all the power of the truck goes to the pump. Everything is machined to very tight tollerances as any slop would damage the entire assembly.

    Once power is applied to the collar it is more or less locked into place by the friction of the gears. If you were to try and move the collar to the opposite position you'd have to overcome the locking friction and then mesh a spinning gear to a stationary one, very difficult (I'd say just about impossible while there is power on the system) and makes a huge grinding noise when you try.

    If you've ever made the mistake of shifting the shifter while the tranny is still in gear or before the speedo drops to zero you will hear a noise that will make you cringe with fear of what the chief is going to do to you, as he will hear it even if he's in the next town over.

    If you loose air pressure while in pump or road it does not matter, you'd still have to overcome the friction and then slide spinning things together.

    Short of some humongous wear issues, about the only way I can see the pump shifting while running would be if you lost air pressure and then Godzilla or King Kong picked up your truck and began slamming the rear bumper on the pavement trying to get the shift collar backwards. Of course at that point chocks would be useless as the tires would not be on the ground, and you wouldn't care anyway as you'd be running home as fast as possible shouting "think of a happy place" while wondering how much crap your underwear could hold.

    Hope this helps
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    So it needs pressure to go either way. Ok, scrap that.

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    I find it interesting that the story always goes something like "I was throttling up and suddenly the truck took off..." You never hear "I was throttling up and suddenly there was a massive crashing and grinding coming from the pump, so I called Earl over to look at it while it continued to crash and grind, he called Bobby John, and as we were sharing a pinch of Skoal the truck just got quiet and took off."

    Now PTO pumps are a different story. Anything with pump and roll capabilities has a much easier time of jumping into gear, but even those should have some reasonable safeties, and as of yet I have not heard anyone say any of these trucks were pump and roll.
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    haha, great posts 304.
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    We have a new unit with a PTO pump. I can't see ANY reason why it would take-off, there is no interaction whatsoever with the tranny to make the pump "live." The tranny stays in N, you flip a switch on the console and the pump is engaged. In fact, I've been preaching to all who are learning to pump it that this ISN'T like the other trucks, you don't shift the transmission to engage the pump on this one.

    I'd see the liklihood for catastrophe being much greater in a pump driven off the road tranny since that's the same part that makes the truck roll down the road, just switched from driving the shaft that drives the rear wheels to the shaft that drives the pump. Regardless of whether its a mechanical failure, or an operator error - to me the liklihood is much greater there...
    Last edited by npfd801; 12-04-2005 at 02:48 PM.

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    Quote Originally Posted by npfd801
    We have a new unit with a PTO pump. I can't see ANY reason why it would take-off, there is no interaction whatsoever with the tranny to make the pump "live." The tranny stays in N, you flip a switch on the console and the pump is engaged. In fact, I've been preaching to all who are learning to pump it that this ISN'T like the other trucks, you don't shift the transmission to engage the pump on this one.

    I'd see the liklihood for catastrophe being much greater in a pump driven off the road tranny since that's the same part that makes the truck roll down the road, just switched from driving the shaft that drives the rear wheels to the shaft that drives the pump. Regardless of whether its a mechanical failure, or an operator error - to me the liklihood is much greater there...
    Believe me, you have that reversed. If you read Fire304's very good description of transfer case operated pumps, you would see that there is little to no chance of the truck being able to drive away. The driveline is physically disconnected from the wheels and it can't go back while it's moving without self destructing. With a PTO driven pump, the only thing between standing still and driving away is the gearshift lever. That is hardly a margin of safety and the driveline is completely connected.
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