Author Topic: Trevithick  (Read 11851 times)

Offline Brian Rupnow

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Re: Trevithick
« Reply #30 on: August 28, 2020, 03:53:29 PM »
More bits and pieces designed this morning. Time to stop for a coffee now.

Offline Brian Rupnow

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Re: Trevithick
« Reply #31 on: August 28, 2020, 04:39:24 PM »
I'm getting closer and closer to decision time on the steam cylinder and valve. Charles Lamont raises a valid point---I haven't found any Trevithick engine running the type of valve that Julius has drawings for. After much googling, I have found out that the Trevithick engine used a bell-crank lever to open and close a rotary 4-way valve. This means that the cylinder is basically just a plain cylinder, and the actual valving all happens in a separate block. It undoubtedly works, because there are a few recreated Trevithick engines running round using the rotary 4 way valve operated thru a Bell crank, as well as one completed model from Germany. I like the design by Julius, because there are no Bell cranks nor pivot points involved. Of course, the immediate question is has anybody built an engine using Julius' version of the valve, and how well did it work. Since I am not a stickler for authenticity, it seems I have three choices. I can use the same valve that Trevithick used, except I would be working from "scratch" and would have to develop the design for something a lot smaller in scale---OR--I can use what appears to be a much simpler cylinder/valve designed by Julius, ---OR---I can use a cylinder and valve body almost identical to that used on the Stephenson's Rocket, although if I do it ends up being a complete departure from what Trevithick did, but I know that it works.

Offline Charles Lamont

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Re: Trevithick
« Reply #32 on: August 28, 2020, 06:11:07 PM »
Charles, do you have any information/links on how the piston valves worked on the Trevithick loco? The videos you posted dont show any detail, though you can hear the valve actuating in a way consistant with what Julius drew. You say his layout is not right, but what IS the right way?Thanks!

I haven't seen a link. I will look out and reduce to uploadable size some photos that will do the trick. I may be some time.

Offline Brian Rupnow

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Re: Trevithick
« Reply #33 on: August 28, 2020, 06:32:27 PM »
In this video you can see the actuator operating the bell crank that controls the steam valve. I did find one excellent animation of the Trevithick 4 way valve yesterday, but I've watched so many Trevithick videos on Youtube that I'm going cross-eyed and can't find it today.
« Last Edit: August 28, 2020, 06:55:50 PM by Brian Rupnow »

Offline crueby

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Offline Brian Rupnow

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Re: Trevithick
« Reply #35 on: August 28, 2020, 08:26:03 PM »
Quite possibly the worst singing I have ever heard in my life!! :Lol: :Lol:

Offline crueby

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Re: Trevithick
« Reply #36 on: August 28, 2020, 08:42:00 PM »
Quite possibly the worst singing I have ever heard in my life!! :Lol: :Lol:
Yeah, leave the speakers off but good details in a few places.

Offline JULIUS

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Re: Trevithick
« Reply #37 on: August 28, 2020, 09:39:25 PM »
Brian

After watching the videos I saw how the 4 way valve was operated (By the way the singing was lousy.)
I have made a design of Robert Trevithick London Steam Carriage and I designed a 4 way valve to make this machine work. it is very similar to the one which I saw in the video.
If you are interested I can place those drawings on this forum.
The valving is not complicated but tricky.

Julius

Offline Charles Lamont

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Re: Trevithick
« Reply #38 on: August 28, 2020, 10:29:20 PM »
The first two photos show the surviving stationary engine in the Science Museum.

1) Left of the cylinder is the regulator lever sticking out horizontally. The quadrant has holes to peg the regulator in position. Imediately left of that is the valve actuating stick. The two main bars have the top and bottom tappets sandwiched between and at the bottom of the slot, sloping down towards us, is the valve lever. Beside that is the tappet guide, running in its own narrower slot.

2) The cylinder head can be see towards the right, middle. The 4-way valve stem is sticking out to the right. The exhaust flange is on the back of the head, with the pipe through the feedwater heater to the chimney. Above the valve you can see the passage to the top of the cylinder cast into the head. The regulator cock is not visible, immediately in front of the 4-way.

3) The same arrangement on our replica, except ours is the other side of the cylinder (for a reason). The valve actuating arm is pointing downwards at the top of the left hand slot. The guide at the centre of the view is temporary and has since been replaced with something less ugly. In the slot immediately above the arm you can see how the leather facing on the oak tappet has become polished.

4) Here we have our cylinder head with the lap I made for the tapered cock bores. The small bore at the back is the regulator, and the port in it is the steam inlet from the boiler.
The connecting port from the regulator to the 4-way is clearly visible, and you can just see a bit of the port that connects to the bottom of the cylinder. The big chamfer on the left contains the port to the top of the cylinder, and the exhaust port is opposite the regulator port.

5) In this one you can see the previous operation in which the valve chambers are being bored on the 4ft vertical borer. The patterns were borrowed from The Trevithick Society, and the same head is used on their Puffing Devil. Of interest, just above the top edge of the angle plate are the trapezoidal steam inlet port to the regulator on the right, and the connecting port for the bottom end of the cylinder on the left. The exhaust passage goes 90 degrees round the outside to the exhaust port at the back.

6) The top of the cylinder into which the liner has just been shrink fitted, hence the bloom of ice. The passage on the left runs right down the outside of the cylinder to connect at the bottom. Again, the funny shaped port lets steam up from the boiler.

7) Here the head is sitting in position on the cylinder. The exhaust flange can be seen on the right of the head casting.

8 ) Dave Reynolds, on the left, is to blame for the whole idea and most of the design. I'm in the middle, and Allan MacKenzie is on the right. Not seen, in addition to the overalls and panamas is another important accessory - the driver's starting umbrella. 
« Last Edit: August 28, 2020, 10:46:43 PM by Charles Lamont »

Offline Brian Rupnow

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Re: Trevithick
« Reply #39 on: August 28, 2020, 11:25:26 PM »
Julius--Yes, if you have pictures of an alternate valve system, we would all appreciate seeing them. I couldn't get my cheap Huwlit-Packard printer to print your drawings, so I sent them out to a commercial printers this afternoon. I want to recreate the valve/cylinder you have designed in 3d Solidworks to get a better understanding of it, and to see if the scale can be reduced to work with my model of the Trevithick engine. Has anyone built a valve/cylinder to your drawings (as posted here) and had it run successfully? Thank you for your help and interest.---Brian

Offline Charles Lamont

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Re: Trevithick
« Reply #40 on: August 29, 2020, 12:01:29 AM »
Julius, could you expand on your thinking behind your shuttle valve arrangement, please? BTW, I hope you don't think I have set out to denigrate your design, I have just wanted to make sure that it was understood that it was not authentic.

Offline crueby

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Re: Trevithick
« Reply #41 on: August 29, 2020, 12:42:39 AM »
Hi Charles,


Were you guys able to open up the valve on the original engine, or at least see old drawings or photos? Great that the engine survived! Thanks for your information!

Offline Brian Rupnow

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Re: Trevithick
« Reply #42 on: August 29, 2020, 01:29:38 AM »
HAH!!! Found it. The animation of Trevithick's valve/cylinder starts about 13 minutes in.
« Last Edit: September 13, 2020, 01:30:51 AM by Brian Rupnow »

Offline crueby

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Re: Trevithick
« Reply #43 on: August 29, 2020, 02:20:46 AM »
Brilliant description. Glad you found it!

Offline Brian Rupnow

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Re: Trevithick
« Reply #44 on: August 29, 2020, 08:20:35 PM »
I have spent today making a 3D model of Julius' valve/cylinder combination. I haven't spent any time yet determining how it's going to work, but at least I have all of the components modeled and mated. As modeled, this cylinder is only 18mm bore (about 11/16") x about 3 3/8" stroke. The piston rod is 4 mm diameter, (about 0.157") diameter. There are a bunch of ports which have to be added yet to the cylinder and a number of pipes to transfer air.
« Last Edit: August 29, 2020, 09:32:35 PM by Brian Rupnow »