Can anyone explain in simple terms how a 'saw by' or 'double-saw by' train movement is performed?. I have read how it works and read it again and I still can't get my head around it?. This 'saw by' procedure appears to have been fairly common on single tracked north American railroads.
The scenario-
Two long freight trains in the early hours of a dark night are approaching each other from opposite directions on a single line railroad in the USA and both trains are due to pass each other at a small way side passing loop (in the middle of nowhere) the problem is both freight trains are to long to fit in the passing loop so how do they pass each other?. Apparently it was done by carrying out a 'saw by' or 'double-saw by' movement being performed.
This procedure was being carried out when a following express passenger train ran into the rear of one of the long freight trains that was at a stand and not fully in clear off the single line while it was carrying out a 'saw by' movement with the other long freight train at the other end of the passing loop in the USA back in 1900.
Long freight conundrum?
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Long freight conundrum?
Original start date of 2010 on the LNER forum and previously posted 4500+ posts.
Re: Long freight conundrum?
The first part of the 'saw by' move seems simple enough if you can call it that and that's if I read it correctly?.
Take the northbound freight for example the guard gets out of his brake and 'breaks the train' (uncouples the wagons) because the rear portion of the freight won't fit into the passing loop so leaving the rear portion on the main line (a single line track) the loco draws the front portion into the loop clear of the points at the south end of the passing loop and stops with the rear end of the train 'in clear' but a part of the actual end of the train is still standing on the main line. Then the southbound freight draws forward past the loco and front portion of the northbound freight that is standing in the passing loop and attaches to the rear portion of the northbound freight standing in it's path southwards and then proceeds to propel the rear portion forwards (backwards in reality) until the rear portion of the southbound freight clears the 'north end' of the exit to the passing loop leaving the main line clear so as to allow the northbound loco and a portion of the northbound freight to leave the loop but that still leaves the rear portion of the northbound freight on the front end of the southbound freight are you still with me?. After this point it gets a bit hazy what happens next??. So the rear portion of the northbound freight maybe 5,6,7 or 8 or more freight cars and a brake longer are attached onto the front end of the southbound freight?. What happens after this??. How does the rear portion of the northbound freight become re-attached to the northbound freight??.
Apparently this 'saw by' move or 'double-saw by' movement could take up to two hours to complete.
Take the northbound freight for example the guard gets out of his brake and 'breaks the train' (uncouples the wagons) because the rear portion of the freight won't fit into the passing loop so leaving the rear portion on the main line (a single line track) the loco draws the front portion into the loop clear of the points at the south end of the passing loop and stops with the rear end of the train 'in clear' but a part of the actual end of the train is still standing on the main line. Then the southbound freight draws forward past the loco and front portion of the northbound freight that is standing in the passing loop and attaches to the rear portion of the northbound freight standing in it's path southwards and then proceeds to propel the rear portion forwards (backwards in reality) until the rear portion of the southbound freight clears the 'north end' of the exit to the passing loop leaving the main line clear so as to allow the northbound loco and a portion of the northbound freight to leave the loop but that still leaves the rear portion of the northbound freight on the front end of the southbound freight are you still with me?. After this point it gets a bit hazy what happens next??. So the rear portion of the northbound freight maybe 5,6,7 or 8 or more freight cars and a brake longer are attached onto the front end of the southbound freight?. What happens after this??. How does the rear portion of the northbound freight become re-attached to the northbound freight??.
Apparently this 'saw by' move or 'double-saw by' movement could take up to two hours to complete.
Original start date of 2010 on the LNER forum and previously posted 4500+ posts.
Re: Long freight conundrum?
Ok working on the assumption that the above is how the first part of the 'saw by' move is carried out and if I read it correctly now for the second part of the move to complete the 'saw by' movement.
The northbound freight has gone a long way 'up the track' and at some stage comes to a stand somewhere a fair distance from the passing loop. Meanwhile the southbound freight with part of the rear portion of the northbound freight still attached to it's front end propels (sets back) it's whole train all the way back to the north end of the passing loop points or switches and stops. So far so good. Next up the points or switches are set coming off the main line and into the passing loop where the southbound freight then moves forward and propels the rear portion of the northbound freight cars and brake into the passing loop and then stops where the guard uncouples the loco from the freight cars. Next up the southbound freight sets back it's whole train again out of the passing loop and stops just beyond the points or switches leading into the passing loop after which the points or switches are reset along the main line and the southbound freight finally departs southbound into the darkness no doubt giving a few whistles to let the northbound freight that it was finally heading south. The points or switches at the north end of the loop are then reversed off the main line and back into the passing loop and at some stage the northbound front portion of the northbound freight and it's loco are set back along the main line for some distance until the front portion of the freight cars enter the passing loop where the freight cars finally couple up again with it's rear portion. Finally after an hour or two the northbound freight finally departs the passing loop as a complete train and also heads off into the darkness...
Not totally sure if that is how the 'saw by' movement is or was carried out but I can't think of another way that the rear portion of the northbound freight would finally become attached to 'the other half of it's train' on just a straight line and a passing loop that is to short to accommodate both over length freight trains?.
The northbound freight has gone a long way 'up the track' and at some stage comes to a stand somewhere a fair distance from the passing loop. Meanwhile the southbound freight with part of the rear portion of the northbound freight still attached to it's front end propels (sets back) it's whole train all the way back to the north end of the passing loop points or switches and stops. So far so good. Next up the points or switches are set coming off the main line and into the passing loop where the southbound freight then moves forward and propels the rear portion of the northbound freight cars and brake into the passing loop and then stops where the guard uncouples the loco from the freight cars. Next up the southbound freight sets back it's whole train again out of the passing loop and stops just beyond the points or switches leading into the passing loop after which the points or switches are reset along the main line and the southbound freight finally departs southbound into the darkness no doubt giving a few whistles to let the northbound freight that it was finally heading south. The points or switches at the north end of the loop are then reversed off the main line and back into the passing loop and at some stage the northbound front portion of the northbound freight and it's loco are set back along the main line for some distance until the front portion of the freight cars enter the passing loop where the freight cars finally couple up again with it's rear portion. Finally after an hour or two the northbound freight finally departs the passing loop as a complete train and also heads off into the darkness...
Not totally sure if that is how the 'saw by' movement is or was carried out but I can't think of another way that the rear portion of the northbound freight would finally become attached to 'the other half of it's train' on just a straight line and a passing loop that is to short to accommodate both over length freight trains?.
Original start date of 2010 on the LNER forum and previously posted 4500+ posts.
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Hatfield Shed
- LNER A4 4-6-2 'Streak'
- Posts: 1722
- Joined: Fri Dec 23, 2011 3:34 pm
Re: Long freight conundrum?
It's perhaps easier to think of it as two 'run around' operations.
The up and down trains divide on approaching the passing loop, each into two portions which will fit in the passing loop: U1, U2, D1, D2
U1 and D1 pass each other using the loop.
U1 couples on to D2, reverses to loop, leaves D2 on loop and runs around on the other road.
D1 couples on to U2, reverses to loop, couples on to D2, moves through loop and leaves U2 in loop, then passes U2 on the other road and proceeds.
U1 reverses to U2, couples up, and then proceeds.
Very easy on paper, but rather more difficult on the ground, especially ensuring the stopped train sections are sufficiently far from the passing loop to allow the movements. In theory you can divide a train into as many sections as required for the passing loop length...
The up and down trains divide on approaching the passing loop, each into two portions which will fit in the passing loop: U1, U2, D1, D2
U1 and D1 pass each other using the loop.
U1 couples on to D2, reverses to loop, leaves D2 on loop and runs around on the other road.
D1 couples on to U2, reverses to loop, couples on to D2, moves through loop and leaves U2 in loop, then passes U2 on the other road and proceeds.
U1 reverses to U2, couples up, and then proceeds.
Very easy on paper, but rather more difficult on the ground, especially ensuring the stopped train sections are sufficiently far from the passing loop to allow the movements. In theory you can divide a train into as many sections as required for the passing loop length...
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John Palmer
- NBR D34 4-4-0 'Glen'
- Posts: 250
- Joined: Sat Sep 22, 2012 7:27 pm
- Location: Somerset
Re: Long freight conundrum?
Don't see any need to divide more than one of the two trains:
D1 detaches D2 on approach to loop.
D1 positions in loop clear of fouling points at each end.
U1, remaining as a complete train, runs through loop passing D1; attaches D2 at its front.
D1 exits loop and proceeds to a point beyond the loop sufficient to provide clear track for U1.
U1 + D2 reverse into loop. D2 is detached in loop.
U1 reverses clear of loop then proceeds on its way, passing D2 in the loop.
D1 reverses into loop, attaches D2 and proceeds on its way.
Also don't see any need for U1 to propel D2 back into loop, reverse out of loop then proceed on other track. Just needs to drop D2 in the loop, reverse clear of loop points, then be on its way again via the other track.
D1 detaches D2 on approach to loop.
D1 positions in loop clear of fouling points at each end.
U1, remaining as a complete train, runs through loop passing D1; attaches D2 at its front.
D1 exits loop and proceeds to a point beyond the loop sufficient to provide clear track for U1.
U1 + D2 reverse into loop. D2 is detached in loop.
U1 reverses clear of loop then proceeds on its way, passing D2 in the loop.
D1 reverses into loop, attaches D2 and proceeds on its way.
Also don't see any need for U1 to propel D2 back into loop, reverse out of loop then proceed on other track. Just needs to drop D2 in the loop, reverse clear of loop points, then be on its way again via the other track.
Re: Long freight conundrum?
Thanks Hatfield Shed. Personally I find the whole procedure a bit of a 'head scratcher' regarding two over length or over long freight trains travelling towards each other on a single line and both freights are to long to fit into a passing loop on the same single line?. Still the procedure was done maybe if I could actually see how it was done 'the penny would drop' and it would become more clear to me.
As I said I read the whole procedure of uncoupling trains and then shunting freight cars around and moving up and down the individual trains could take up to two hours which mite be a bit on the extreme side so it obviously wasn't a easy task to perform and it was possibly something that was tended to be avoided if possible or kept to a minimum.
As I said I read the whole procedure of uncoupling trains and then shunting freight cars around and moving up and down the individual trains could take up to two hours which mite be a bit on the extreme side so it obviously wasn't a easy task to perform and it was possibly something that was tended to be avoided if possible or kept to a minimum.
Original start date of 2010 on the LNER forum and previously posted 4500+ posts.
Re: Long freight conundrum?
Maybe it was an easier task to perform John than I understand it was?.
The first part of my understanding of how it was done that I posted is from reading something on another railway website about it but then the guy loses me after awhile?. The second part is 'my' assumption of how the 'saw by' move was completed although it may not have been done that way but I couldn't think of any other way how the rear of the northbound freight would reattach to the front portion of the northbound freight to become a complete train again?.
The first part of my understanding of how it was done that I posted is from reading something on another railway website about it but then the guy loses me after awhile?. The second part is 'my' assumption of how the 'saw by' move was completed although it may not have been done that way but I couldn't think of any other way how the rear of the northbound freight would reattach to the front portion of the northbound freight to become a complete train again?.
Original start date of 2010 on the LNER forum and previously posted 4500+ posts.
Re: Long freight conundrum?
Meanwhile back on the north American railroads...
Either way a 'saw by' movement being carried out with those two trains you can bet money on it that it will be a time consuming procedure to perform because on the railway something like that would be.
Two double-headed steam hauled freight trains both a mile long standing face to face with each other on a single railroad track with a half a mile refuge siding which is to short to accommodate either train it's going to take sometime to sort those two trains out and get them on the move again.
Either way a 'saw by' movement being carried out with those two trains you can bet money on it that it will be a time consuming procedure to perform because on the railway something like that would be.
Two double-headed steam hauled freight trains both a mile long standing face to face with each other on a single railroad track with a half a mile refuge siding which is to short to accommodate either train it's going to take sometime to sort those two trains out and get them on the move again.
Original start date of 2010 on the LNER forum and previously posted 4500+ posts.
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Hatfield Shed
- LNER A4 4-6-2 'Streak'
- Posts: 1722
- Joined: Fri Dec 23, 2011 3:34 pm
Re: Long freight conundrum?
Quite right, that's what happens when you try thinking with Burgundy assist!John Palmer wrote: ↑Sun Oct 31, 2021 3:14 pm Don't see any need to divide more than one of the two trains...