Author Topic: Stephenson's Rocket  (Read 28601 times)

Offline Brian Rupnow

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Re: Stephenson's Rocket
« Reply #105 on: May 29, 2020, 09:50:57 PM »
Today was cross-head day. I would rather run in circles and bite myself than make pieces this small, but these are probably the smallest parts of this build, and they turned out alright. Don't let the size of these parts fool you. To get them to slide freely on the cross head guides and not jamb up the cylinder over the full extent of it's stroke is almost a magic act. As you can see from the picture, I changed the design of the cross-head a little bit from my original plan which both made it simpler to build and let me use a store-bought shoulder bolt as the pivot. The round cross-head guides are silver soldered to the bracket closest to the cylinder. At the end farthest away from the cylinder they are just setting in reamed holes, which positions them accurately but lets me disassemble them if I need to.

Offline crueby

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Re: Stephenson's Rocket
« Reply #106 on: May 29, 2020, 10:39:45 PM »
Coming together great, thats a lot of parts to align. No carb to build at least!

Offline stevehuckss396

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Re: Stephenson's Rocket
« Reply #107 on: May 29, 2020, 11:20:05 PM »
And no valve seats to lapp
Do not be like the cat who wanted a fish but was afraid to get his paws wet.

Offline Brian Rupnow

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Re: Stephenson's Rocket
« Reply #108 on: May 30, 2020, 09:24:05 PM »
Today was mostly given over to the sliding valves for each cylinder. They are finished and look all right, but I won't really know until I get my gaskets cut and installed and some air pressure to work with. I have been wondering for the last week how I was going to get air pressure into the rectangular "steam chest" that the slide valves set in. I decided today to scrap the aluminum steamchest covers that I made and replace them with mild steel. This will let me silver solder an air inlet tube to the center of each cover. The pressure doesn't care how it gets into the steamchest, as long as it gets in.

Offline crueby

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Re: Stephenson's Rocket
« Reply #109 on: May 30, 2020, 09:26:59 PM »
Looking great!  I dont recall, do you already have the ports drilled through to the cylinder ends, and out to the exhaust?

Offline Brian Rupnow

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Re: Stephenson's Rocket
« Reply #110 on: May 30, 2020, 09:37:51 PM »
Yes, the ports and exhaust are all drilled. I can't for the life of me remember how you persuade these things to run clockwise or counter clockwise.---It's been a long time since I built this style of engine. I think it's just how you set the timing/positioning of the eccentric??

Offline crueby

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Re: Stephenson's Rocket
« Reply #111 on: May 30, 2020, 09:53:01 PM »
Yes, the ports and exhaust are all drilled. I can't for the life of me remember how you persuade these things to run clockwise or counter clockwise.---It's been a long time since I built this style of engine. I think it's just how you set the timing/positioning of the eccentric??
Exactly - if you put the eccentric 90 degrees to one side of the crank pin, it runs one direction, 90 degrees to opposite side, it runs the other way. Thats the 'nominal' 90 degrees, plus/minus whatever lead you design in. For a display runner, it doesn't matter a lot. If you have a reversing gear with two eccentrics, all it does is switch which eccentric is acting on the valve slider. Its amazing how many mechanisms were invented for reversing a steam engine, it would be a long list!

Offline Brian Rupnow

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Re: Stephenson's Rocket
« Reply #112 on: May 30, 2020, 11:06:10 PM »
Thanks Chris.

Offline Brian Rupnow

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Re: Stephenson's Rocket
« Reply #113 on: May 31, 2020, 08:57:05 PM »
Today was a minor milestone. I just finished making the gaskets for one of the two cylinders on this engine, and of course I wanted to see if /how it worked. I always get a little thrill out of reaching a point where the slide valve controls the movement of the cylinder.
<a href="https://www.youtube.com/watch?v=gMx_5MBLW9w" target="_blank">http://www.youtube.com/watch?v=gMx_5MBLW9w</a>

Offline crueby

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Re: Stephenson's Rocket
« Reply #114 on: May 31, 2020, 09:29:51 PM »
Can hear your grin in the video!   :ThumbsUp:

Offline Art K

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Re: Stephenson's Rocket
« Reply #115 on: May 31, 2020, 10:25:49 PM »
Chris,
I think it was one of those ear to ear grins! Great job Brian!
Art
"The beautiful thing about learning is that no one can take it away from you" B.B. King

Offline Brian Rupnow

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Re: Stephenson's Rocket
« Reply #116 on: June 01, 2020, 09:52:02 PM »
Some days you eat the bear---Some days the bear eats you!! I spent an absolutely insane amount of time today freeing up the cross head to slide smoothly with the extension and retraction of the cylinder. I got one unit finished. I can extend or retract the cylinder by shifting the slide valve and watching it smoothly do it's business.The other cylinder though, is being a beast and binding like crazy---and the slide valve isn't seating correctly against the side of the cylinder. If I can hear air hissing, then the slide valve isn't seating properly. I will fix the second unit tomorrow---and ---guess what?--I can't really do any more until I build the test stand to mount the cylinders and cross heads and baseplate to. After I get the test stand built, I will move on to the eccentrics and connecting rods.

Offline crueby

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Re: Stephenson's Rocket
« Reply #117 on: June 01, 2020, 10:06:30 PM »
By 'Test Stand', you mean the rest of the locomotive, right?   :Lol:
 :popcorn: :popcorn: :popcorn:

Offline Brian Rupnow

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Re: Stephenson's Rocket
« Reply #118 on: June 02, 2020, 12:13:41 AM »
Nope---Due to the fact that there will be a lot of work in the model of the Rocket, I will first build the engines and bases and mount them to a Test Stand. The test stand will mimic all of the attachment points and axle positions that will be on the finished Rocket model, but will be a lot less work. After I have ran the engines to my satisfaction in the test jig, I will go ahead with the actual model of the Rocket.

Offline crueby

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Re: Stephenson's Rocket
« Reply #119 on: June 02, 2020, 12:37:13 AM »
Slick setup!

 

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