Modified D-valve dimensions from print

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Mike Walsh
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Modified D-valve dimensions from print

Post by Mike Walsh » Mon Sep 23, 2019 1:46 pm

Hello,

I'm working on a set of Allen Mogul cylinders.

The dilemma I have right now is that the ports have been cored strangely. As it stands now, the port dimensions that I'm coming up with are oversize, not because of the actual core, but there was a core fin remaining, resulting in the edge of the steam port being cut to clean up this core fin.

The print calls for 1-1/4" outside edge of the two ports, with 1/8" lap. I take this to mean that my D-valve should be 1.5" long. The inside edge of the ports should be 3/4" (1/4" wide port).

Since my ports will be oversize, how will this affect my setup? I understand I will need to modify the D-valve. As it stands the port dimensions will be larger than print. I think I might be able to clean it up to 0.300". As a result, I will need a D-valve that has outside dimensions of 1.600", since I will be maintaining the 1/8" lap dimension. If I match the inside port of the D-valve to the inside edge of the ports, will this mechanism still work?

I am trying to understand the changes I need to make. Thanks!

Mike Walsh

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NP317
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Re: Modified D-valve dimensions from print

Post by NP317 » Mon Sep 23, 2019 9:04 pm

Mike:
Consider making a bronze port plate to the specified port dimensions that will become the port face for the D-valve.
Then you need to consider how the plate thickness changes the height of the valve assembly.
That should minimize re-engineering of the system.
RN

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cbrew
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Re: Modified D-valve dimensions from print

Post by cbrew » Mon Sep 23, 2019 10:21 pm

the prints should have notes on this topic. did you see the notes?
If it is not live steam. its not worth it.

Mike Walsh
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Re: Modified D-valve dimensions from print

Post by Mike Walsh » Tue Sep 24, 2019 5:46 am

Yes - but I wanted to make sure I understand correctly. The notes say to modify 'C' to suit, while maintaining 1/8" Lap. With the amount of core fins that is present, I think I will be over the 0.250" port dimension when I clean up. Also, the notes call for a 3/8" distance between the cavity inside the D valve and the outside edges of the D valve (0.250 port dimension plus 1/8" lap).

That being said, I've attached the following image. In this case, P should be 0.250. Is 'P' variable (clean up to fit), as well as C being variable? If so, this will affect the OAL, since the one constant is L (lap).

But with P, C being variable, is what matters most, L (1/8" lap)?

Trying to put it in a formula that I can understand and apply... So if C and P are variable (modify to suit), that is clear enough to me.

The cores on my ports are such that I think I need an additional 0.015" or 0.020" on each side of each port to obtain sufficient cleanup. As a result, I need to modify my D valve... I am ready for the porting process, so I am turning to Chaski (and a few other places) for more information.
Attachments
IMG_6999.jpg

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cbrew
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Re: Modified D-valve dimensions from print

Post by cbrew » Tue Sep 24, 2019 8:02 am

Morning Mike,
sounds like you have the understanding.
the lap is constant (this number is set elsewhere), C (block) needs to match C (valve) and P (block) needs to match P (valve) plus Lap.
If it is not live steam. its not worth it.

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PeterCraymer
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Re: Modified D-valve dimensions from print

Post by PeterCraymer » Tue Sep 24, 2019 12:17 pm

Mine were slightly off as well. Just follow the instructions as you have said and all will be fine.

blff cty lcmtv wrks
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Re: Modified D-valve dimensions from print

Post by blff cty lcmtv wrks » Wed Sep 25, 2019 4:52 pm

when I made my last two allen engines, I made a valve plate out of eighth inch thick stainless steel. I duplicated the valve dimensions according to the print. made the d valve to print specs. I milled out the ports on the cylinder block a bit in order for them to align up a bit better. sandwiched it all together, and off I went. works like a champ. the valve being of a softer material, will wear instead of the plate. it's a lot simpler to cleanup the valve rather than to dissemble the cylinder block and all the associated guts. (sorry for taking so long, but it has just started storming here and I went outside to watch the lightning and the wind).

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Builder01
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Re: Modified D-valve dimensions from print

Post by Builder01 » Wed Sep 25, 2019 6:39 pm

blff cty lcmtv wrks wrote:
Wed Sep 25, 2019 4:52 pm
when I made my last two allen engines, I made a valve plate out of eighth inch thick stainless steel. I duplicated the valve dimensions according to the print. made the d valve to print specs. I milled out the ports on the cylinder block a bit in order for them to align up a bit better. sandwiched it all together, and off I went.
How did you attach the stainless plate to the cylinder block? Gasket, screws, JB Weld? - David

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NP317
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Re: Modified D-valve dimensions from print

Post by NP317 » Wed Sep 25, 2019 9:35 pm

Usually the thin port plate is simply sandwiched between the top of the cylinder surface and the valve chest.
RN

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Builder01
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Re: Modified D-valve dimensions from print

Post by Builder01 » Thu Sep 26, 2019 5:12 am

NP317 wrote:
Wed Sep 25, 2019 9:35 pm
Usually the thin port plate is simply sandwiched between the top of the cylinder surface and the valve chest.
RN
I understand it is "sandwiched". This tells me where it is attached, but, not how. The valve chest cannot be the only thing holding the plate to the cylinder block, that would only hold the plate at the very edge. The area between the exhaust and steam ports is usually quite narrow. Steam would easily leak between these ports right under the plate.

David

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Rich_Carlstedt
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Re: Modified D-valve dimensions from print

Post by Rich_Carlstedt » Thu Sep 26, 2019 10:25 am

David
" Steam would easily leak between these ports right under the plate."

I think you want to use some Permatex there to solve that problem
Rich

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NP317
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Re: Modified D-valve dimensions from print

Post by NP317 » Thu Sep 26, 2019 4:37 pm

Considering that the steam is above the plate pressing down on the slide valve and the plate,
and that the exhaust passage is open to atmosphere, leakage under the plate is not likely.
And as stated by Rich, some Permatex sealant would assist.
RN

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