Author Topic: Stephenson's Rocket  (Read 14487 times)

Offline Brian Rupnow

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Stephenson's Rocket
« on: May 06, 2020, 08:14:23 PM »
I am interested in Stephensons Rocket. I have watched a few Youtube videos of it and read a few articles on it. I am curious about the valving on the steam cylinders. The cylinder and steam-chest seem to be conventional, but there doesn't appear to be an eccentric driven from the "axle" driving the valve slider back and forth. There does appear to be a shaft setting parallel to the cylinder rod, and some action of the cylinder rod moving a slider back and forth on that parallel rod, and a swinging lever connected to the valve slider rod. Can anybody shed some light on this please.---Brian

Offline Brian Rupnow

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Re: Stephenson's Rocket
« Reply #1 on: May 06, 2020, 08:45:37 PM »
A little more study shows that the parallel rods were the cross head guides. A separate connecting rod ran from the cross head down to the "crank" on the large front wheels. Still haven't seen how the steam valve is operated.

Offline Firebird

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Re: Stephenson's Rocket
« Reply #2 on: May 06, 2020, 09:02:50 PM »
Hi Brian

I have this that might help



Cheers

Rich

Offline crueby

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Re: Stephenson's Rocket
« Reply #3 on: May 06, 2020, 09:11:16 PM »
In Rich's drawing, note the handles on the levers going from the eccentric linkage up to the steam chest. On other engines of that period it was common to have manual overides on the valving for use in starting up.

Offline Brian Rupnow

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Re: Stephenson's Rocket
« Reply #4 on: May 06, 2020, 09:18:16 PM »
Based on the bottom drawing, it appears that this engine did have eccentrics mounted to the axle to operate the valve slider in the steam chest. I haven't been able to see them in any other videos except one by Keith Appleton, and even then it's not terribly clear. So, it appears that the engine and valve system is very similar to my Cretors Popcorn engine, other than a different style of cross-head guide and the fact that the rod from the eccentric is routed thru a hand control. Does that sound right?

Offline crueby

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Re: Stephenson's Rocket
« Reply #5 on: May 06, 2020, 09:25:59 PM »
Sounds right. Looks like they put a pivot on each of the levers connected to the diagonal rod. Seems like there would be plans out there somewhere, if not castings as well, for such a famous engine. I recall there was a reconstruction of the Rocket at the railroad museum in Pennsylvania, saw it when I first was down there for Cabin Fever. Will see if I have any photos... The museum may have plans.


EDIT: Nope - that engine was the John Bull, not the Rocket.  It was at the Henry Ford museum. You can zoom in on the photo here, it shows the valve rods in the lower right:

https://www.thehenryford.org/collections-and-research/digital-collections/artifact/33379
« Last Edit: May 06, 2020, 09:34:59 PM by crueby »

Offline Firebird

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Re: Stephenson's Rocket
« Reply #6 on: May 06, 2020, 09:31:32 PM »
Hi Brian

Sent you a PM

Cheers

Rich

Offline Brian Rupnow

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Re: Stephenson's Rocket
« Reply #7 on: May 06, 2020, 09:38:49 PM »
Having had great success with the Cretors Popcorn engine (thank you Stu Hart) It would be fairly simple to make working engines for Stephenson's Rocket. The only thing that thru me was the lack of information about the eccentrics. I'm all "engined out" right now, but I'm thinking ahead to when I may get bored from doing nothing again.


Offline Brian Rupnow

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Re: Stephenson's Rocket
« Reply #9 on: May 06, 2020, 09:54:49 PM »
I was fortunate enough to actually find a solid model of the "Rocket".  Unfortunately, whoever made this didn't model the valve gear. I see from a drawing that was sent to me that the rod from the eccentric connects to a reversing lever which has a second rod extending from it to the valve slider.
« Last Edit: May 07, 2020, 12:08:49 AM by Brian Rupnow »

Offline Admiral_dk

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Re: Stephenson's Rocket
« Reply #10 on: May 06, 2020, 10:01:53 PM »
Chris beat me to it .... and I only took one picture of the Rocket on display in Yorkshire last year  :-[
On my picture (too big) it's obvious that there is no excentrik on the wheels and the engine is different in appearance - picture from front right - where I can see a steam chest behind the cylinder and it's connected to the crosshead guide ....
The picture from the Henry Ford Museum shows two excentrics in the middle under the engine .... and that bit is in complete darkness on my picture.

Offline Brian Rupnow

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Re: Stephenson's Rocket
« Reply #11 on: May 06, 2020, 10:02:47 PM »
I actually did see the excellent drawings by Julius, but if there is information in there about the eccentric and valve rods, I couldn't find it.

Offline Brian Rupnow

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Re: Stephenson's Rocket
« Reply #12 on: May 07, 2020, 12:06:11 AM »
Interesting stuff. The 3D model I show in post #9 was made in some other 3D software than Solidworks. What that means is that I can import it into Solidworks, and I can measure it, but I can not change the scale nor manipulate any of the part files. Currently, the piston diameter measures 1.3" diameter and the front wheels measure 9 3/8" diameter. That is too large for my tastes, although some quick calculations show that if I scale it to 0.481% of it's current size, the pistons will be 5/8" diameter and the large front wheels will be 4 1/2" diameter. That gets closer to a size I could actually work with. I could make a decent, but more simplified model with working engines. I guess the best place to start would be making two model engines of the correct size. This of course means I would have to design the engines first, which wouldn't be a giant hurdle.

Offline Elam Works

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Re: Stephenson's Rocket
« Reply #13 on: May 07, 2020, 01:21:14 AM »
I seem to recall reading somewhere (likely Model Engineer in the eighties or nineties) a study of the Rocket where it mentioned the remains showed several different iterations of valve gear, or valve gear actuation. Like many things it have been altered back in the day, and during subsequent restorations. So you might have a choice!

-Doug

Offline Brian Rupnow

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Re: Stephenson's Rocket
« Reply #14 on: May 07, 2020, 01:40:18 AM »
Hi Doug--I've done a lot of "in depth" Googling the last couple of days, and your right. I have seen 4 or 5 different valve gear arrangements on this engine. I'm going to stick with something very close to the valve gear used on the Cretors Popcorn engine, because I have built three of them, they all work good, and the valve gear is simple.---Brian.