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| High speed slip https://www.rypn.org/forums/viewtopic.php?f=1&t=8548 |
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| Author: | Jim Adams [ Thu Feb 19, 2004 1:08 am ] |
| Post subject: | High speed slip |
The only blemish on an otherwise outstanding record of the IC Engineering Dept.was the failure of the "One Spot", the 4-6-4 had a high speed slip problem that was never solved. I remember a discussion with Sam Hake,a Travelling Engineer at the time. I had just watched the "One Spot" walk out of Centralia with a pasenger train and was impressed at the way it picked up that train and got out of town. At my suugestion that "That is some engine", Sam grunted and said " Yeh, but she is too slippery".Not long after that #1 literally destroyed 3 or 4 miles of track near Champaign.Il. when she went into high speed slip. I am told the Pennsy T-1 had the same problem and like the IC #1 it was never solved. This makes me wonder if anyone ever studied these engines to see if at certain high speeds the vibrations caused by off center weights of the motion work would hit a harmonic of the engine springs and thus add the two impulses together with disaterous results. Anybody know ? Was this ever consideded? Jim rrfanjim@charter.net |
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| Author: | Hugh Odom [ Thu Feb 19, 2004 7:55 am ] |
| Post subject: | Re: High speed slip |
Jim, That's an interesting question. I don't think this was really suspected in the problems with the T-1s. I believe their problems basically boiled down to "two 4-coupled engines are 4 times as likely to slip as one 8-coupled engine". The harmonics theory however could explain the balancing problems that Baldwin and others ran into in the late 1930's. One of the most infamous cases of driver balancing problems occurred with the Atlantic Coast Line's 1800-series R-1 4-8-4's, built by Baldwin in 1938. These locomotives had cast bed frames, roller bearings, Baldwin disk drivers, and were pretty much state-of-the-art for 1938 U.S. steam power. Shortly after they were delivered however, a rash of bent rails showed up on the ACL's mainline between Richmond, Virginia and Jacksonville, Florida. Baldwin & ACL engineers investigated and confirmed that the engines were balanced according to the latest recommendations of the AAR. They actually installed a high speed camera under one engine and verified that at high speed (~100 MPH) the drivers were leaving the rails for a portion of each revolution and then slamming back down. After further investigation, some of the counterbalancing material was removed from each of the drivers, the problem went away, and the engines were rated for 90 MPH after that. What it boils down to is that balancing the drivers of a 2-cylinder steam locomotive HAS to be a compromise. It is impossible to completely balance the reciprocating parts of a steam locomotive (pistons, piston rods, crossheads, and a portion of the main rod) with rotating counterbalances on the drivers. You can make the rotating balance perfect or the reciprocating balance perfect but not both. There are several good articles in railroad magazines which explain this. The weird thing is that locomotive designers understood this long before 1938 and had already arrived at empirical formulas for how much of the reciprocating weight to balance that had always worked out before. It was a fairly simple calculation to show at what speed the "over-balance" in the counterweight would cause the drivers to lift off the rail- the centrifugal force simply had to exceed the axle load on the drivers. The trouble is with engines like the ACL 1800s is that they found that this occurred at a much lower speed than was calculated. Several other classes of engines built about this same time (the New Haven 4-6-4's for instance) ran into this same problem. The most logical explanation is that there was some kind of harmonic set up between the drivers, the engine's spring rigging, and the track/ballast (which is not a rigid structure). It was probably beyond the capabilities of these engineers in the 1930's to analyze this behavior so they just experimented and arrived at a different rule-of-thumb for locomotive balancing. Improvements like light weight alloy reciprocating parts also helped reduce the problem. This same phenomena may have been at work with the IC's #1. Good Steaming, Hugh Odom > The only blemish on an otherwise outstanding > record of the IC Engineering Dept.was the > failure > of the "One Spot", the 4-6-4 had a > high speed slip problem that was never > solved. > I remember a discussion with Sam Hake,a > Travelling Engineer at the time. I had just > watched the "One Spot" walk out of > Centralia > with a pasenger train and was impressed at > the way it picked up that train and got out > of town. > At my suugestion that "That is some > engine", Sam > grunted and said " Yeh, but she is too > slippery".Not long after that #1 > literally destroyed 3 or 4 miles of track > near Champaign.Il. > when she went into high speed slip. > I am told the Pennsy T-1 had the same > problem and > like the IC #1 it was never solved. > This makes me wonder if anyone ever studied > these engines to see if at certain high > speeds the vibrations caused by off center > weights of the motion work would hit a > harmonic of the engine springs and thus add > the two impulses together with disaterous > results. > Anybody know ? Was this ever consideded? > Jim The Ultimate Steam Page whodom2001@yahoo.com |
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| Author: | David M. Wilkins [ Thu Feb 19, 2004 9:07 am ] |
| Post subject: | 2 cylinders -vs- 3 or 4? |
Hugh, Does having a steam locomotive with three or four cylinders help solve the balancing problem at high speeds? I realize that you then enter into a whole new set of potential problems with one or two cylinders between the frames and the associated higher maintenence costs, etc. david.wilkins@bardstown.com |
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| Author: | Hugh Odom [ Thu Feb 19, 2004 10:12 am ] |
| Post subject: | Re: 2 cylinders -vs- 3 or 4? |
David, It definitely helps to have more cylinders. For one thing, each of the 3 or 4 sets of reciprocating parts will be smaller and lighter than those of an equivalent 2-cylinder locomotive, so that less weight is required to balance the parts. A 4-cylinder locomotive (2 outside cylinders, 2 inside cylinders) can be arranged to be almost perfectly balanced. The pistons are "timed" so that the inside cylinders are 180 degrees out of phase with the outside cylinders, allowing the recipirocating weights to mostly offset each other. This arrangement was pretty common in Europe and was tried on a good many U.S. engines around the turn of the century. I'd think that a 3-cylinder layout (2 outside, 1 inside) would see a partial benefit from this effect, but it still wouldn't be perfectly balanced. The American Coal Enterprises ACE 3000 would have used Bill Withuhn's arrangement (see the old "Trains" article "Did We Scrap Steam Too Soon?") with 4 outside cylinders which would have been perfectly balanced. See my webpage for more info. Some of the others on the ACE team (Wardale & Porta) saw other problems with this arrangement and didn't particularly like it. Wardale is presently designing a modern 4-6-0 for excursion service in the UK based on the British Rail "standard" 5MT. It will have only 2 outside cylinders. The reciprocating parts will be designed using state-of-the-art techniques like finite element analysis to minimize their weight. Other techniques such as vehicle dynamics analysis will be used to determine the optimum amount of over-balance to be used so that the engine can operate at the same speeds as commercial passenger trains without problems. Hugh > Hugh, > Does having a steam locomotive with three or > four cylinders help solve the balancing > problem at high speeds? I realize that you > then enter into a whole new set of potential > problems with one or two cylinders between > the frames and the associated higher > maintenence costs, etc. The Ultimate Steam Page whodom2001@yahoo.com |
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| Author: | buddy bob [ Thu Feb 19, 2004 7:42 pm ] |
| Post subject: | Re: High speed slip |
> The only blemish on an otherwise outstanding > record of the IC Engineering Dept.was the > failure > of the "One Spot", the 4-6-4 had a > high speed slip problem that was never > solved. > I remember a discussion with Sam Hake,a > Travelling Engineer at the time. I had just > watched the "One Spot" walk out of > Centralia > with a pasenger train and was impressed at > the way it picked up that train and got out > of town. > At my suugestion that "That is some > engine", Sam > grunted and said " Yeh, but she is too > slippery".Not long after that #1 > literally destroyed 3 or 4 miles of track > near Champaign.Il. > when she went into high speed slip. > I am told the Pennsy T-1 had the same > problem and > like the IC #1 it was never solved. > This makes me wonder if anyone ever studied > these engines to see if at certain high > speeds the vibrations caused by off center > weights of the motion work would hit a > harmonic of the engine springs and thus add > the two impulses together with disaterous > results. > Anybody know ? Was this ever consideded? > Jim don't forget the fa was about 3. thats way to low. bb |
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| Author: | Jim Adams [ Fri Feb 20, 2004 7:43 pm ] |
| Post subject: | Re: High speed slip |
> don't forget the fa was about 3. thats way > to low. bb buddy bob; It seems that the IC usually had a high TE for the weight of its engines. Even the 2500's were slippery according to some of the engineers who ran them. However, I remember one trip I made where we set out and picked up cars at several points but had about 98 cars on the average. The only time the engine slipped was on a mine lead where we were coming out with several loads of machinery from the closed mine. There was grass growing over the rail and she took a couple of quick chugs before the engineer got her settled down. Perhaps, being used to the engines, the engineers made the difference? Jim rrfanjim@mvn.net |
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