Gallery, Projects and General > The Design Shop
Reverse Link
PatJ:
The link appears to be drawn non-symmetrical.
If you draw it symmetrical in CAD, starting with a vertical centerline, and then using the dimensions above, you get 30.61 deg from the vertical centerline to the rod hole, and 20.84 deg from the vertical centerline to the edge of the slot.
To the link lift hole, measured from the vertical centerline is 30.21 deg.
It seems like the slot and rod holes would have to be laid out symmetrical to a vertical centerline, but maybe I am missing something.
Pat J
Edit: That 1/4" (typ.) dimension can't be correct, since you can see in the drawing that the sides are not equal.
If you hold the 3.25" dimension, then the angle from the vertical centerline to the lift link hole is 33.2 deg.
John Stevenson:
--- Quote from: Bogstandard on May 01, 2011, 11:06:49 PM ---
I have also noticed that the third hole has no size or outer rad shown, if those two are missing as well, then difficulties will arise working out where that one should be.
Bogs
--- End quote ---
?? Drawing says three 3/16" holes ?
Missing dimension between the holes is 1 1/4"
Bernd:
I just got done with doing a bit of research on this valve gear. For those members that are new to steam engines, the valve gears shown above are called “Stevenson Valve”. They were basically invented to reverse a steam engine. That is what has been written up in two books that I have from Lindsay. One is called “Steam Propelled Vehicles” by James E. Homans and the other is “Valve Gears” , International Correspondence Schools.
Apparently the distance between the two bottom holes, the holes that are marked .281” , on Rudy’s engine, are not critical, as is their horizontal spacing. As long as the rod that is connected to the eccentric imparts the travel necessary to open and close the valve opening inside the steam chest.
That’s about the best I can explain it. So based on that I can sort of “guesstimate” the dimensions on the Bertha engine.
If you are further interested in how a Stevenson valve works may I suggest a an internet search on steam valves.
Bernd
lordedmond:
Be careful with stevensons valve gear there are there types
launch, loco and marine
you have a launch link the loco link has the eccentric strap holes on the ends the marine link has all the holes on the centre line
with holes as in your the link amplifies the eccentric strap motion the lot link reduces it
this link may give some info to sort out the hole positions its not the stroke that matters
[url] http://www.donashton.co.uk/html/stephenson_s_gear.html/
Bernd:
--- Quote from: lordedmond on May 03, 2011, 05:47:41 AM ---launch, loco and marine
--- End quote ---
Thanks for the link.
Won't the launch and marine be the same? I know the one on the loco's is different than on a launch.
Bernd
Note: The link you gave doesn't work. Hopefuly this one will. http://www.donashton.co.uk/html/stephenson_s_gear.html
Saved that page for further study. Very interesting information there.
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