valve timing for Festiniog Linda

This topic has 7 replies, 4 voices, and was last updated 16 March 2015 at 11:59 by julian atkins.

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9 March 2015 at 09:12 #182610
Roger Davies 3
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@rogerdavies3
Can anyone verify how to set the eccentrics for accurate valve timing on this loco?

There is a 6 degree angle between cylinders and valve gear and a rocking lever.. So should the eccentrics be set at : forward gear, 84 degrees behind crank, reverse, 96 degrees ahead of crank.
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9 March 2015 at 09:12 #7512
Roger Davies 3
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@rogerdavies3
setting of eccentrics
10 March 2015 at 21:43 #182820
Neil Wyatt
Moderator
@neilwyatt
Hello Roger,

Welcome to the forum.

At a guess, no. I'm assuming its Stephenson's gear, in which case the eccentrics need to be advanced slightly to provide lead as well as making an allowance for the angle between cylinders and valves.

I'm sure an expert will be along soon, but I expect they will recommend setting the eccentrics so the valves are open just by a crack (traditionally the width of a tram ticket) at TDC,.

Neil
11 March 2015 at 11:00 #182860
Ian S C
Participant
@iansc
Tram ticket? I remember two sorts of tickets, the one you are thinking of Neil was similar to news print, the other was about 1/16" thick card, both about 2" x 1". sorry, a bit OT.

Ian S C
11 March 2015 at 21:07 #182942
julian atkins
Participant
@julianatkins58923
hi roger,

LINDA has stephensons gear indirect drive with rocker arms, and launch links and slide valves.

you are correct in assuming that the eccentric settings are shifted around by the amount of inclination of the gear to the cylinder centre line.

with launch links the angle of advance ought to be more than 6 degrees – though your reference to 6 degrees is the above inclination and not the angle of advance as commented by Neil.

my own version of LINDA is in 3.5"g and the gear was worked out by me using Don Ashton's excellent booklet many years ago.

cheers,

julian
11 March 2015 at 21:07 #182943
julian atkins
Participant
@julianatkins58923
hi roger,

LINDA has stephensons gear indirect drive with rocker arms, and launch links and slide valves.

you are correct in assuming that the eccentric settings are shifted around by the amount of inclination of the gear to the cylinder centre line.

with launch links the angle of advance ought to be more than 6 degrees – though your reference to 6 degrees is the above inclination and not the angle of advance as commented by Neil.

my own version of LINDA is in 3.5"g and the gear was worked out by me using Don Ashton's excellent booklet many years ago.

cheers,

julian
16 March 2015 at 10:55 #183411
Roger Davies 3
Participant
@rogerdavies3
Thanks. Not sure why it should be more than the 6 degrees though
16 March 2015 at 11:59 #183420
julian atkins
Participant
@julianatkins58923
hi roger

ive sent you a pm

cheers,

julian
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