ME 4761 – Sirius Piston Valve C**k up Corner

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ME 4761 – Sirius Piston Valve C**k up Corner

This topic has 7 replies, 3 voices, and was last updated 22 January 2025 at 21:30 by noel shelley.

Viewing 8 posts - 1 through 8 (of 8 total)

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22 January 2025 at 15:16 #779060
Charles Lamont
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@charleslamont71117
I am surprised this 3-page article by Graeme Quayle has been published apparently without sanity checking the content.

This bloke has based the whole thing on an evident total misunderstanding of the Sirius’s valve design. His new valve ‘works’ on the wrong edges altogether.

I don’t have the drawings, so I can’t check the dimensions, but I think there can be little doubt that the original valve as drawn was fine. If there had really been a problem with it, it would have been known about long ago.

This needs a correction printing ASAP.
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22 January 2025 at 16:44 #779067
JasonB
Moderator
@jasonb
I don’t have the Sirus drawings but if the Sun is anything to go by then the bottom image in fig 3 has the valve in the wrong place, The widened 1/4″ section is not meant to be in the middle. This is the same way as the old Stuart drawing in Fig 1 has it.

Also Photo 4 shows the two full diameter parts of the new piston valve the same width but the drawing says the one at the end is 5/32 and the other 1/4″

Seems to have missed the point that it is inside admission and the inlet passage should nor be covered at any time

Looks like Cock up corner will be continuing into the new mag!
22 January 2025 at 18:18 #779093
Charles Lamont
Participant
@charleslamont71117
Yes, its a sirius error.
22 January 2025 at 18:29 #779097
JasonB
Moderator
@jasonb
I am 99% sure that the Sirius is the same as the Sun and that the ports between cylinder and valve are machined. these are the important ones not the rough cored ones to the exhaust at the top and within reason the central hole to inlet is not an important size and could probably be anywhere from 3/16″ to 5/16″ and still work without problem using the valve as drawn on either of the Stuart drawings.
22 January 2025 at 19:10 #779107
JasonB
Moderator
@jasonb
100% sure now having looked at Tubal cain’s build in ME, the slots are milled and as he says

“The two slots correspond to the ports found on an ordinary slide valve”

So they are the important ones and the cast passages that the Author based his comments and the article on have nothing to do with the valve operation.

3 wasted pages really.
22 January 2025 at 20:07 #779122
Charles Lamont
Participant
@charleslamont71117
Does anyone have a set of Sirius drawings we could ask for some dimensions to be checked ?
22 January 2025 at 20:21 #779127
JasonB
Moderator
@jasonb
I’ll scan the ones that were in ME in the morning as I’ve put the old mags away again but I have no reason to doubt them provided you use the machined ports through to the cylinders to base any calculations and assumptions on.

Just like on the Mystery engine over om HMEM the two upper cast passages on the sirius are just like the slots linking HP to LP and have no bearing on valve events.
22 January 2025 at 21:30 #779150
noel shelley
Participant
@noelshelley55608
Jason, which editions of ME did TC do the write up in ? Thanks. Noel.
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