mbrown
Elder Statesman
Posts: 1,718
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Post by mbrown on Dec 23, 2018 12:57:43 GMT
Hi Nobby,
On screw reversers where the screw is in the cab, you can either see the position of the nut or else there will be an indicator to show the cut off. On some LMS locos, the nut was at the back of the screw in forward gear, so there was an indicator driven by a bicycle chain arrangement which moved to the opposite end of the scale to show the position of the gear. ON LNER Pacifics and V2s, the indicator was a vertical scale on the backhead operated by a rod from the reach rod bellcrank.
On BR standards, the wheel in the cab operated a rotating drum with the cut off positions on it - I think I am right that the numbers for forward gear were raised and the numbers for back gear engraved. The LBSC Britannia doesn't have this, so you have to go by feel - but to see the prototype arrangement, look on Adam (Cro)'s threads to see his stunning miniatures.
But, as others have noted on this thread, notching up is usually done by "feel" and "ear" (I am slightly deaf and one of the TR Loco Inspectors once asked if that was why I hadn't notched up the loco as much as he thought proper!) For full forward or back gear, you just turn the handle until it won't go any more.
Malcolm
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Post by Deleted on Dec 23, 2018 13:47:07 GMT
Hi Nobby, ON LNER Pacifics and V2s, the indicator was a vertical scale on the backhead operated by a rod from the reach rod bellcrank. Malcolm here you go Nobby, this is the vertical slide as fitted to 4472 today, this is for 'long Valves' and thus the same as for my chosen era in the 30's. my intention is to get this plate etched (along with any others befitting the 30's) and have the scale fully working on the backhead, it shouldn't be too difficult to calibrate it to match the reverser position, a little trial and error should do it... Pete
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Lisa
Statesman
Posts: 806
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Post by Lisa on Dec 23, 2018 14:41:59 GMT
... the reverser... not sure of the correct terminology... Like most things, the terms can no doubt change by country, region, era, company, and probably even among different sheds, and others may want to add in terms they've heard more often, but you'll generally be safe (and understood) with: Pole Reverser, for the lever type, with which you adjust the cutoff with the Reversing Lever, or simply The Reverser. In this case you may Notch Up, by moving the Reversing Lever one (or more) notch(es) in the Quadrant or Stand closer to mid-gear. Screw Reverser, for the wheel type, with which you adjust the cutoff with the Cutoff Wheel, or simply The Wheel. In this case you have infinite adjustment of cutoff, but Notching Up may still be used either as a borrowed term from a pole reverser, or in reference to moving to a marked position on the Indicator, Scale, or Dial. The Reverser, of course, also works as a catch-all for both types.
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Post by delaplume on Dec 23, 2018 15:24:57 GMT
As I've only done a tiny bit of driving so far I'm still a bit vague on certain aspects of the reverser. On a "Normal" reverser (a signal box style lever, not sure of the correct terminology) you can see when its in the central position, fully forward or back, but with a screw reverser (as I'll have on my Brit) I'm assuming the only way to tell is by feel and experience, or physically looking out at the lifting arm? Before I started looking into it I almost assumed they would have some sort of indicator like a ships telegraph but that doesn't appear to be the case? Hi Nobby.......It's a Pole or Lever reverser that you are looking for...... On a screw reverser the indication markings as to cut-off are usually found on the top plate...... Typically it might look like this}--------- Reverse...... "Drift" or Coast ........Mid Gear........."Drift" or coast ...........Forwards. with the % markings also shown........ Screw reversers are normally fitted to Passenger hauling locos ( or mainline freight and Mixed Traffic locos ) where accurate settings over long distances will greatly aid efficiency etc...........Pole ( Lever ) reversers tend to be for shunting locos where their ability to be quickly changed during many hours on duty can be a blessing !! Here is an LMS and a GWR screw reverser }-----------
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Post by delaplume on Dec 23, 2018 15:29:12 GMT
... the reverser... not sure of the correct terminology... Like most things, the terms can no doubt change by country, region, era, company, and probably even among different sheds, and others may want to add in terms they've heard more often, but you'll generally be safe (and understood) with: Pole Reverser, for the lever type, with which you adjust the cutoff with the Reversing Lever, or simply The Reverser. In this case you may Notch Up, by moving the Reversing Lever one (or more) notch(es) in the Quadrant or Stand closer to mid-gear. Screw Reverser, for the wheel type, with which you adjust the cutoff with the Cutoff Wheel, or simply The Wheel. In this case you have infinite adjustment of cutoff, but Notching Up may still be used either as a borrowed term from a pole reverser, or in reference to moving to a marked position on the Indicator, Scale, or Dial. The Reverser, of course, also works as a catch-all for both types. Hi Lisa, "Link up" is another one..
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pault
Elder Statesman
Posts: 1,496
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Post by pault on Dec 23, 2018 15:33:22 GMT
Whilst the scale on a screw reverser, regardless of its position, is nice to have, but it has little practical value when driving using the reverser. If you are running full regulator at 25% cut off and the engine starts to struggle a little, you don’t think to yourself ”I’ll advance the cut off to 31.3%” and look at the indicator. You would wind the reverser forward until the loco is running how you want it. Experience may suggest to you that 2 turns will be enough, but you can equally find that out by turning the handle. Personally when driving on the reverser I wind it backwards and forwards relatively slowly, it gives a very smooth ride and makes slipping unlikely. As with many aspects of driving/firing, read the road start altering the cut off just before you need the power.
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uuu
Elder Statesman
your message here...
Posts: 2,807
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Post by uuu on Dec 23, 2018 17:19:35 GMT
Not quite a silly as a gear indicator on a motorbike, where you have to stop and get off, to see what gear you're in.
Wilf
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JonL
Elder Statesman
WWSME (Wiltshire)
Posts: 2,906
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Post by JonL on Dec 23, 2018 20:55:22 GMT
This has been very useful, thank you.
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steam4ian
Elder Statesman
One good turn deserves another
Posts: 2,069
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Post by steam4ian on Dec 23, 2018 21:05:57 GMT
As I've only done a tiny bit of driving so far I'm still a bit vague on certain aspects of the reverser. On a "Normal" reverser (a signal box style lever, not sure of the correct terminology) you can see when its in the central position, fully forward or back, but with a screw reverser (as I'll have on my Brit) I'm assuming the only way to tell is by feel and experience, or physically looking out at the lifting arm? Before I started looking into it I almost assumed they would have some sort of indicator like a ships telegraph but that doesn't appear to be the case? Hi Nobby.......It's a Pole or Lever reverser that you are looking for...... On a screw reverser the indication markings as to cut-off are usually found on the top plate...... Typically it might look like this}--------- Reverse...... "Drift" or Coast ........Mid Gear........."Drift" or coast ...........Forwards. with the % markings also shown........ Screw reversers are normally fitted to Passenger hauling locos ( or mainline freight and Mixed Traffic locos ) where accurate settings over long distances will greatly aid efficiency etc...........Pole ( Lever ) reversers tend to be for shunting locos where their ability to be quickly changed during many hours on duty can be a blessing !! Here is an LMS and a GWR screw reverser }----------- Most screw reversers , manual, Franklin power or Hadfield power were simply labelled in percent cut off. Often there was a sign near either the reverser or drifting/cut-off gauge which required that the loco be in 40% cut off for prolonged periods of drifting, that is where the regulator/throttle is closed or just cracked. I suggest that this requirement had something to do with lubrication. There was on type of power reverser made by ALCO which was lever operated and had fine notches on the quadrant. This was used on a late variant of the SAR 700 Class 2-8-2 and needless to say thay were very popular for heavy shunting although a main line loco. The only time a friendly driver allowed me to "sit in his seat" was so he could demonstrate to a trainee how the loco could be run entirely on the reverser once underway. He set the regulator and told me to control the speed by the reverser. It was an uphill run with tight curves (train drag) severe speed restrictions at a couple of points and a straight with a higher speed limit. Fortunately I remembered the speed limits and kept the train well under control without my mate once having to touch the regulator or brake and we kept good time. I was nervous at the end of the straight because we were right on the speed and I had the reverser back at 5%; it was a tribute to the valve gear that the loco showed no lumpiness.
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