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Walschaerts Valve Gear and Piston Valves


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Posted: Sun 10th Apr 2011, 6:21pm
Walschaerts Valve Gear and Piston Valves

Need Simple advice and how to set the valve gear to measure the distance between centres on the ecentric rods and expansion link.Also need technique for setting up the timing on the piston valves. I do not have any port holes in the cylinder blocks to see the position of the steam valve. Alan Nethercott

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Joined: 1-01-70

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Posted: Sat 23rd Apr 2011, 7:53pm

test it with a simulator


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Replies: 2

Posted: Sun 24th Apr 2011, 9:15pm

Hi Alan
Valve Gear isn't usually simple unfortunately. But to get the correct length of the eccentric rod, first determine the exact wheel position at each dead centre, and mark wheel rim against frame. Wheels and axleboxes should be packed up to correct running position. Position and clamp the expansion link so that the valve spindle doesn't move when moving the radius rod up and down. ie into forward or reverse gear. Measure distance from return crank spindle to hole at bottom of expansion link. Rotate wheels to other dead centre and measure again. It should be the same. To try out make up a dummy eccentric rod (flat strip) and rotate wheels. Assuming a well designed valve gear all that's needed now is to centralise the piston valve. Without setting holes try using a piece of tubing on each drain cock and blowing when the valve is about to open for admission. This should occur just before dead centre. Try to get it even for both ends. Treat each side of the loco totally seperately. Hope this helps but I have simplified quite a bit.
Good Luck
Andrew Robelou
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