A4 Valve Timing
Moderators: 52D, Tom F, Rlangham, Atlantic 3279, Blink Bonny, Saint Johnstoun, richard
Re: A4 Valve Timing
I was very lucky to be in West Germany during the mid-70's and saw the finish of DB steam. Unlike BR, the DB kept their engines in first class condition until the end. It was very common to see the engines on shed undergoing valve and piston exams. Loco's on the wheel drops and barely any steam leaks. I just caught the end of the Emden - Rheine steam hauled 4000 tonne iron ore trains, now that was an experience worth waiting for, especialy at night on the Lathen incline. Double headed 043's.
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eastern_pheonix
- NER Y7 0-4-0T
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- Joined: Wed Dec 15, 2010 3:18 pm
Re: A4 Valve Timing
Thank you for all the answers. Having looked carefully at all the information I can find there should be no problems arrising form the conjugated gear it self providing all the linkages have just running the correct clearances. Wear out side of the limits may lead to maginal variation of both inside and outside valve gear. I think that most of the critisisms are no more that prejudicial twaddle. Undoubtedly badly worn components would cause variation. Now all gresley 3 cylinder locomotives can sound out of beat but an analysis off the sound recordings show this not to be true (put them on a scope and check the time line intervals). What there is however is a different sound at different strokes. The difference I would propose is due to the different lengths and shapes of the steam and exhaust pipes. Having done work on inlet manifolds on internal combustion engines I know how difficult it is to get balance. Also there is of course the effect of the exhaust ejector and injector to add variation. thanks again.
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eastern_pheonix
- NER Y7 0-4-0T
- Posts: 5
- Joined: Wed Dec 15, 2010 3:18 pm
Re: A4 Valve Timing
As a postscrip I was interested to see the comment about optical alignment equipment. At a recent visit to a prserved railway repair shed I was being take round by one of the 'engineers' as he was presnted. Having being involved in machine tool alignment with zeiss equipment I ask whether they had optical equipment. " Not needed you can do it all with pieces of string and eye " was the answer I made no further comment but I think it was my stare that reddened his face.
As for deflection the 2 to one lever looks quite beefy compaired to a combination lever. !
As for deflection the 2 to one lever looks quite beefy compaired to a combination lever. !
Re: A4 Valve Timing
Having done both machine tool alignments and steam loco alignments I can agree that the optical gear is not necessary, although it does make it slightly easier.
Modern machine tool alignments are done with laser interferometers and can resolve down to better than a micron over vast distances. Even optics can get much better than is required on a steam loco. This is not to denegrate the optics or indeed the laser interferometer
A steam loco frame is hardly a rigid structure andtrying to line something up with a measuring system that is too accurate is a real pain.
A piece of piano wire (I use MIG welding wire) and inside micrometers will meet all requirements for steam loco work.
What I usually do is to use tufnol bushes to insulate the wire from the frame and connect a bell and buzzer across them so that the micrometer completes the circuit. It is possible to detect a thou like this.
Don't forget that steam loco builders did not generally talk of thous, but of 64ths (I have seen one drawing that called for 128ths. Much use was made of trammels for comparison rather than actual measurements.
Ian
Modern machine tool alignments are done with laser interferometers and can resolve down to better than a micron over vast distances. Even optics can get much better than is required on a steam loco. This is not to denegrate the optics or indeed the laser interferometer
A steam loco frame is hardly a rigid structure andtrying to line something up with a measuring system that is too accurate is a real pain.
A piece of piano wire (I use MIG welding wire) and inside micrometers will meet all requirements for steam loco work.
What I usually do is to use tufnol bushes to insulate the wire from the frame and connect a bell and buzzer across them so that the micrometer completes the circuit. It is possible to detect a thou like this.
Don't forget that steam loco builders did not generally talk of thous, but of 64ths (I have seen one drawing that called for 128ths. Much use was made of trammels for comparison rather than actual measurements.
Ian