How did builders quarter drivers on the axle during construction? Secondly, when a locomotive was lifted off its drivers for maintenance, how were the drivers moved beneath for service. Seems it had to be a VERY precise positioning. Thanks!
Best practice for quartering was to use what was called a ‘quartering machine’. To use this, the drivers were rough-pressed on the axle ‘in quarter’ reasonably closely, then were placed in the machine. This had all the tools necessary to bore and finish the main-pin seats in the two drivers.
When the rod pins were installed in the drivers, they could then be finish-machined in alignment.
Remember that precise 90.000*-degree quartering was not important; what was essential was that the quartering be precisely identical for all drivers joined by a fixed set of rods. To an extent, even significant deviation from ‘true’ quarter could be adjusted in the valve gear; I believe David Wardale comments on this in his book on the Red Devil.
When the drivers were to be removed, either they were lowered on a drop table (and extracted sideways) or the locomotive was lifted via crane and the wheels rolled out longitudinally. I do not think the wheels were ‘rolled in’ so precisely as to allow the rods to be installed on them; much more likely that their axleboxes would be blocked up so as to load the equalizing suspension appropriately, and the wheels then gently rotated or barred around to where one side’s rods could be installed (the other side then falling into appropriate alignment). Naturally there was no alignment issue with installing the mains.
Alignment with roller bearing rods was necessarily much more precise, as the clearances in those bearings runs to no more than thousandths before significant heating takes place. I suspect one of the next questions is how controlled lateral motion was possible with skew on the bearings absolutely restricted to that level of precision. The answer is interesting and fun – let’s see if anyone who does not know can guess how it was arranged…
*I could have been pedantic and written something like 90 degrees 00’ 00.000" but the point was just semant
This may best deserve its own thread, but, since the talk is of quartering, here goes.
The PRR quartered their drivers to where the left driver led the right. Other roads had the right driver lead the left. It has been brought to my attention that somehow through dynamic augment, the driver that leads tends to pound the rail a bit harder than the driver that trails. Can someone explain, in a way easy to understand, why this would be the case?
I assume “the right driver lead the left” was true for the locomotive running forward.
- Erik
Yes
Another way of quartering is described in Locomotive Up To Date, which involved placing the axle in a lathe, scribing the centerline of one keyway at one end of the axle, turning the axle precisely 90 degrees (though as Overmod has said, it is not necessary to be accurate to the fifth or sixth place), and scribing the centerline of the keyway at the other end. The keyways are then cut to the proper width to hold the keys. Thus, when the wheels are pressed onto the axles and their keyways lined up with the axle keyways the wheels will be quartered. .
For any of you that do not have the 1920 edition of this valuable reference, here is a link to a .pdf download.
Well done. My copy (which was my father’s, who operated a locomotive crane in the Tampa Shops of the ACL) is dated 1922, and a line is drawn through the price of $5.00, with $4.00 printed in.
Apparently someone thought that there are people who do not know that “Chas.” is a common abbreviation for “Charles.”
I don’t mean to question your saying that PRR preferred the left drivers to lead; I think I’ve heard that from another source. But what would have been the advantage either way? Sounds suspiciously like “the right way, the wrong way, and the PRR way”.
The W.W.&F. museum up in Maine faced some problems quartering the drivers of their #9 during the ongoing restoration. Apparently, as the result of one of its’ rebuilds on the Sandy River, the driver sets were not from the same engine. It appears to have run several years like that, including its’ time on the Kennebec Central and its’ short career on the original WW&F. The rod bearings simply took the beating as a matter of course!
Check out the discussion section on the museum website under the “Work and events”," W.W.&F #9 official work thread" for a better explanation by people who really know stuff. There are some great photos of how they’ve dealt with the problem.
The story that I heard was that the PRR had a lot of double track territory. By trains normally running on the right hand track and having the left driver lead, what little increase in pounding was kept to the inside of the track structure where the roadbed would be stronger.
Just to be clear, he means the discussion forum – one of the great unsung resources for steam technology. Here is a direct link to the thread in question, showing their quartering machine.
Soooo like PRR thinking.
Thank you, Overmod. I got in a hurry this morning and didn’t take the time to figure out how to post the link. The quartering device they’ve built is a beautiful piece of machinery. I saw it last fall when I was up in Maine, last fall. Didn’t get to see it in use, though. They are truly a talented bunch up there! John
I have seen videos of workers simply rolling the wheels into position.
As for the alignment and spacing of the wheels, I suppose that the locomotive could be set to hover a few inches above the wheel axial and then the wheels could be fine tuned into position.
Doesn’t seems to complicated to me. Of course, things are often easier said than done.
Did you ever get a satisfactory answer to this question?
Somewhere along the line I think that I did.
Just as the left jab hits harder than the right cross that follows, the lead rods have slightly more impact on the track than the opposite set - because there is some followup loading from the following set but none from the 270 degrees of driver rotation until the lead rods come around again.
The Pennsy had a lot of double track which was signaled and run with trains on each track running in one direction. Thus the advantage of putting the heavier blow on the center of the roadbed rather than its edge. Single tracks, and multiple tracks where each track was bi-directional, wouldn’t gain any advantage from left lead over right lead.
Chuck
I am far from anything that could be called an engineer or a physicist*, but my bet would be torque, something akin to precession. The cranks and their loading are outside/above the plane of the rotating mass of the tires, but they also are placed at the boundaries of a single quadrant of a full revolution, as Chuck states.
-Crandell
*Perhaps, in view of my assumption, it’s for the best. [%-)]