Cygnet Royal engine.

[CedricParticipant @cedricblaver37709]

Hello all,

Ive just taken on building the above engine. Going through the plans seemed all OK till I was looking at the “Balance weight” and “Return crank” to the Orbital valve.

The plans and notes don’t appear to show the fixing of the weight to the crankshaft.

In addition there is no side view of the weight. How dose it fit/fix to the crankshaft.

The other thing is the “Return crank” shaft fixing to the “Orbital valve”, is this a loose fitting or a press fit

Am I missing something?

Please can someone help / advise

Many thanks.

[JasonBModerator @jasonb]

The balance weight is integral to the crankshaft, it is shown on the side view of the crankshaft being the dimension at the bottom of 5/16″ think.

I think the valve is just a reamed hole onto the offset 1/8″ spigot and free to move.

[CedricParticipant @cedricblaver37709]

Ok I understand, I did see it but was not sure as there are no indications of the fixing. I assume we make our own decision on the fixing points.

Thank you for the help.

[JasonBModerator @jasonb]

 I assume we make our own decision on the fixing points

No, as I said it is integral eg cut from one bit of metal. Start with some 1.25″ round bar and turn the crankshaft on one end. Offset and turn the crankpin on the other. Lastly cut the shape out of the remaining disc.

Just found Stew’s build, have a look at that

[Jim NicParticipant @jimnic]

Hi Cedric

As Jason says, the crankshaft is designed as one piece.  That struck me as being wasteful of material so I made mine in 3 pieces and Loctited them together.  It has stood up OK so far but after I’ve completed my engines I don’t run them often.

The return crank is a running fit in the valve and the port flange.  As the crank turns it turns the return crank in the port flange so a good running fit to reduce air (or steam) leakage from the valve chest to the crankcase is desired.

Bear in mind that Stu Hart’s drawings are his own amalgamation of a couple of similar designs and not a pure Cygnet Royal so stick to one set of drawings to avoid confusion.  If you haven’t already done so I would echo Jason’s advice to look at Stu’s build log.

Hope this helps

Jim

 

 

 

[CedricParticipant @cedricblaver37709]

Hi Jim Nic, thank you for the help.

Yes I had decided to cut a one piece crank, not as per the notes.

I have machined a couple of one piece steel cranks for the Stuarts multi cylinder engines.

 

In Addition oil goes in where dose it collect, run out past the 2 lower pistons ?

 

[CedricParticipant @cedricblaver37709]

Good day Jim.

The plane you mentioned (Stu Harts) is there a possibility of obtaining a copy of these plans ?

 

The other thing is the crankshaft in your photo how thick is the web between the big end and main ?

Do you have a photo of the big end side ?

Thank for the help have a great day.

Cedric.

[Jim NicParticipant @jimnic]

Hi Cedric

To answer your first question first, Stu is a very helpful and obliging gentleman.  If you contact him on sbwhart@yahoo.co.uk I’m sure he would be happy to send you a copy of his drawings.

Here is a picture of the crank big end, the only one I have apart from the exploded version of the assembly in my earlier post.

I have made the crank web 5mm thick.

Jim

 

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