Author Topic: Trevithick  (Read 11908 times)

Offline Brian Rupnow

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Re: Trevithick
« Reply #60 on: September 01, 2020, 06:13:24 PM »
I spent some time designing this morning, and decided to make the piston rod 3/16" diameter with all the attendant changes to parts which mate with the piston rod. (It was 1/8" diameter before). I am happy with things as they are now, and the success of this design depends on the drawing of the cylinder I received from Julius. You have to admit---it looks pretty wild!!
 

Offline Brian Rupnow

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Re: Trevithick
« Reply #61 on: September 01, 2020, 09:00:12 PM »
Yow!!!--That's a lot of holes. Hope they're all in the right place---

Offline Art K

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Re: Trevithick
« Reply #62 on: September 02, 2020, 03:02:44 AM »
Brian,
That's quite a project you've got going there. Sorta looks like a Christmas tree, mind with the branches lopped off on one side. I've watched some of the videos of how the valve mechanism works and I'm glad they came up with the sliding valve.
Art
"The beautiful thing about learning is that no one can take it away from you" B.B. King

Offline crueby

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Re: Trevithick
« Reply #63 on: September 02, 2020, 03:29:31 AM »
Fascinating to see this come together, early steam technology while they were learning at light speed.

Offline derekwarner

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Re: Trevithick
« Reply #64 on: September 02, 2020, 04:11:52 AM »
Brian.......

I cannot see any nomination for the material of the piston seal elements

With the piston seals being pressure energised, o-rings will tend to shear a slice as they become displaced into the sharpely cut port area when traversing the outer body

The Company Paul Wurth from Luxemburg designed specialist Blast Furnace rotating hydraulic cylinders [very similar internal construction to your  proposed build].......to overcome this sealing issue, cast iron piston ring sets are requuired and operating at 350 Bar - cross port leakage over the cast iron ring sets is amazingly low

http://www.paulwurth.com/The-Group/Company-Profile

Derek
« Last Edit: September 02, 2020, 04:20:31 AM by derekwarner »
Derek Warner - Honorary Secretary [Retired]
Illawarra Live Steamers Co-op - Australia
www.ils.org.au

Offline crueby

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Re: Trevithick
« Reply #65 on: September 02, 2020, 04:19:21 AM »
I think the piston as drawn is set up so it never crosses a port, so it could use o rings. For the valve, which does cross ports, are rings really needed? I made the spool valves on several engines, including the Stanley, without rings on the spool valves, with no issues.

Offline Jasonb

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Re: Trevithick
« Reply #66 on: September 02, 2020, 07:10:17 AM »
Does not look like the piston slides over any ports to me and if a single ring were in the middle of the piston it certrainly would not even partly overlap.so OK with an O ring. If it did over[lap a port then you would be in trouble as the valve would want to move in teh opposite direction and you would have a direct route from inlet to exhaust >:(

The divider between cylinder and valve chamber does not move so that can use o rings as a static seal.

Brian's shuttle is not shown with any o rings

Offline Brian Rupnow

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Re: Trevithick
« Reply #67 on: September 02, 2020, 01:13:39 PM »
Yes gentlemen, that is the plan. No rings on the spool---a lapped fit. Two rings on the cylinder divider that is stationary, and one ring on the pistons which doesn't pass any ports. And--The hose barbs which screw into the sides of the cylinder will intentionally be made too long on the threaded ends, so they can be machined flush with the inside of the cylinder bore.

Offline derekwarner

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Re: Trevithick
« Reply #68 on: September 02, 2020, 02:23:35 PM »
Apologies....being on the opposite upside down side of the World........must have misinterpreted the design images  :headscratch: ....... Derek
Derek Warner - Honorary Secretary [Retired]
Illawarra Live Steamers Co-op - Australia
www.ils.org.au

Offline Brian Rupnow

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Re: Trevithick
« Reply #69 on: September 03, 2020, 01:18:47 AM »
I'm slowly going ahead with the valve as designed by Julius. We have visiting grandchildren this week, and next week after they all go back to school it will be too dangerous for good wife and I to see them until a Covid vaccine is found.  As for the valve which Julius designed, I can see the theory behind it, but I simply can't tell if it works until I have built one to see if it works or not. I think the cylinder is going to have a large "dead spot" at each end of the stroke, but with a large enough flywheel (which the Trevithick engine does) it may not matter. I have almost melted the internet searching for information about the original Trevithick 4-way valve, and the good news is that I think I have sussed it out. Now, whether the Julius design works or not, I simply have to build a rotary valve engine. If I do, I will publish the drawings on all my forums because this stuff is so neat that everyone should have free access to it.

Offline Brian Rupnow

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Re: Trevithick
« Reply #70 on: September 03, 2020, 11:47:34 PM »
Today we have both cylinder end caps finished. That little bit of shaft you see sticking out the end isn't really the piston rod.---I'ts just a "fooler".  I still have to make the packing gland, and then I will start on the hose barbs that screw into the sides of the cylinder. I miscounted earlier when I said there were seven ports.---Actually there are eight.

Offline crueby

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Re: Trevithick
« Reply #71 on: September 04, 2020, 12:00:40 AM »
Great progress, if the valving doesn't work out, should be a good flute.

Offline Craig DeShong

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Re: Trevithick
« Reply #72 on: September 04, 2020, 10:27:02 PM »
Some very interesting projects you're working on Brian.  I'm loving following along.  You seem to be caught in an "early stem locomotive" paradigm.

I'm always looking for the interesting "next project"  maybe a "Tom Thumb" might be in order?

 
Craig

Offline Brian Rupnow

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Re: Trevithick
« Reply #73 on: September 05, 2020, 12:22:01 AM »
Eight little hose barbs, all in a row. This cylinder is going to look like a porcupine. If I can just get a 1/4"-20 thread on the end of each one without destroying it, I'll be very happy!!!

Offline Brian Rupnow

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Re: Trevithick
« Reply #74 on: September 05, 2020, 01:29:46 AM »
Craig--after building engines for 12 years (currently have about 35 of them), my biggest challenge is finding something new and different to build. I don't have a great enthusiasm for early railroad engines, but you have to admit, the sheer "mechinicalness" of the Trevithick and the Stephenson's Rocket are awesome.