More help with Rachel Wall engine

[Steve HuckinsParticipant @stevehuckins53362]

Making progress with Rachel Wall Engine and now trying to understand the steam valve rod from the drawings. Can you help to explain the concept of the three differing measurements as shown on the drawing please ?

The rod changes from 5mm to 4mm to 3mm (for M3 of course).  On the photo sent by Jason for me, (thanks as ever) it shows the 5mm section in a black colour and is threaded M5 for a length of 5mm.  Does this imply that I need to run a piece of 5mm rod down to the other diameters ?

Also, there is a curve Radius 3mm on the end of the rod. Does this imply that it closes up against the curved stud shown in the photograph ? In which case why is it there ? I am assuming it is something to do with the eccentric strap and allowing the steam valve rod to go in and out in line.

Just a bit confusing as if there is a bit of play at that point, will it affect the timing of the valve ?

Thanks in advance

Steve

PS enjoyed the show again this year and managed to limit my spending within budge.

[JasonBModerator @jasonb]

As I read it you start with 5mm dia stainless.

Turn down a 28mm length to 3mm and thead M3

Rechuck to expose some more metal and turn down the next 38mm to 4mm dia with a good finish as that slides in the gland.

Move out a bit more and tap say 10mm long to M5 Fine.

Saw off a bit over length then hold by the 4mm dia and reduce the end to 4mm dia to leave a 5mm length of M5 thread, face to the overall 73mm is reached.

Transfer to milling machine to form the concave end with a 6mm dia cutter.

Yes it looks like the curved end mates with the convex top of the stud

 

[JasonBModerator @jasonb]

Having looked again there is another way if you don’t fancy turning the long 4mm dia.

If you start with 4mm stainless, do the M3 thread as drawing. Then for the other end turn say a 4mm long x 3mm dia spigot. You can then make the a length of M5 thread, drill the end 3mm and loctite to the other piece and then finally do the small spigot and concave.

[Steve HuckinsParticipant @stevehuckins53362]

Jason thank you.
That’s such good advice. I did think about something similar involving threads but your explanation of the alternative is excellent. It also saves trying to get three fairly small diameters spot on from one piece of 5mm. I would probably struggle with that  I will go ahead with a bit more confidence now.
Best wishes and thanks again.
Steve

[Charles LamontParticipant @charleslamont71117]

Who designed that? The valve ‘knuckle’ arrangement seems an unnecessarily difficult thing to make, especially as the original appears to have a conventional pinned clevis joint.

https://www.landesmuseum-mv.de/en/exhibit/steam-engine-from-the-lilienthal-machine-factory-in-berlin/

[JasonBModerator @jasonb]

One of Willey Schneeberger’s designs. It varies quite a bit form Lilienthal’s Wanddampfmaschine

[Steve HuckinsParticipant @stevehuckins53362]

I did find it a bit odd 71117 but wanted at least to replicate the part as per the drawings that came with it from EKP. A clevis would at least assure the steam piston shaft moved in and out parallel. If I need to, I will come back to it should it cause any problems later.  I have managed to make the part today as per Jason’s 2nd suggestion and it has worked out. Let’s see how it goes once I’ve got to the stage of machining the eccentric strap and the mating rod.

cheers for now

Steve

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