Author Topic: Stephenson's Rocket  (Read 14811 times)

Offline crueby

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Re: Stephenson's Rocket
« Reply #45 on: May 11, 2020, 10:13:22 PM »
Will there be an intermediate cross shaft per side? One per eccentric?

Offline zeeprogrammer

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Re: Stephenson's Rocket
« Reply #46 on: May 11, 2020, 10:33:02 PM »
Looking forward to this. I haven't said much but I enjoyed Thumper.

I'm back down in the bat cave now

Is that where all this business started?  ;D
Carl (aka Zee) Will sometimes respond to 'hey' but never 'hey you'.
"To work. To work."
Zee-Another Thread Trasher.

Offline Brian Rupnow

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Re: Stephenson's Rocket
« Reply #47 on: May 11, 2020, 10:43:30 PM »
Chris--The single shaft will go all the way across. The two cylinders will be 90 degrees out of phase to make the engine self starting. I think I will be able to put the right side and left side levers 90 degrees out of phase on the single shaft and have it work. i'm not 100% sure on that yet.

Offline Brian Rupnow

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Re: Stephenson's Rocket
« Reply #48 on: May 11, 2020, 10:48:47 PM »
Hello Zee--most of my ideas start down in the "bat cave". I have a perfect set-up here. My engineering office , washroom, machine shop and "main garage" are all on on one floor. I have a door from my office that opens directly to outside. I never really stop thinking about machinery and mechanisms.----Been that way all my life.---Brian

Offline crueby

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Re: Stephenson's Rocket
« Reply #49 on: May 11, 2020, 11:37:43 PM »
Chris--The single shaft will go all the way across. The two cylinders will be 90 degrees out of phase to make the engine self starting. I think I will be able to put the right side and left side levers 90 degrees out of phase on the single shaft and have it work. i'm not 100% sure on that yet.
I am doubtful, at some points one will be moving forward while the other is moving back.

Offline Brian Rupnow

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Re: Stephenson's Rocket
« Reply #50 on: May 12, 2020, 12:10:48 AM »
Chris--It is quite possible that I may make the single shaft fixed to the engine and attach the two levers on each side together with a sleeve that rotates freely on the fixed shaft. That will give me basically two completely independent engines. It then becomes a simple task of "timing" the eccentrics relative to each other.

Offline crueby

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Re: Stephenson's Rocket
« Reply #51 on: May 12, 2020, 10:24:15 PM »
My copy of the book The Engineering And History of the Rocket by Bailey and Glithero arrived in the mail today. Looks like a great source, off to start reading that in the comfy chair...

Offline Brian Rupnow

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Re: Stephenson's Rocket
« Reply #52 on: May 13, 2020, 01:31:33 AM »
Other than the engine assemblies, this model is relatively simple. Mostly straightforward milling and turning---but---The wheels are going to be monsters. Since I won't be running my engine on a track, the wheels can be mostly made from aluminum---I think. Very much of the "character" of this model is the wheels with square spokes.  There is no easy way to make these wheels. They are going to have to be "built up" from components---an inner hub, an outer rim, and individual spokes. For the scale I am working with, 3/16" square spokes look about right. I've thought about this a fair bit, and this is my plan--so far. I know that I can buy 3/16" square steel keystock. (Not sure if I can get 3/16" square aluminum or not). If I cut all of the spokes to an exact length, and make a proper jig to hold them, I can turn one end of the spokes to be round. I can lathe turn the inner hub and using my rotary table on the mill, I can drill 12 blind 5/32" diameter holes equally spaced in the hub. I can turn the hub as shown, so that when the spokes are installed they have to all fit into the groove, which will keep them all parallel with the face of the wheel. I'm thinking that would be a Loctite job. It would be a wonderful thing if, when assembled, the outer ends of the spoke array would be perfectly concentric with the center of the hub, but in the real world that doesn't happen. Thus, the design of the outer rim which is most visible will have a "lip" that extends down over the end of the spokes to hide them. That way, I can design the outer end of the spokes to be about 0.010" short of contacting the inner rim surface, but they will rest against the lip. At his point I see a simple jig to maintain concentricity between the outer rim and the inner hub. IF I use steel keystock for the spokes, and a steel outer rim, then I can use my tig welder to attach the spokes to the outer rim and it won't show. I don't have the proper gas bottle to weld aluminum, and I have no experience with welding aluminum, but with steel spokes and rim, I could manage.

Offline doubletop

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Re: Stephenson's Rocket
« Reply #53 on: May 13, 2020, 04:32:42 AM »
Brian

Are you planning slip eccentrics so the engine can do forward and reverse? Here bits from my Northumbrian build from some years ago, another Stephensons loco.

https://www.homemodelenginemachinist.com/threads/small-locomotive-boiler-me-northumbrian.14718/



Valve rockers



Slip eccentric valve gear operating


Pete

?To achieve anything in this game, you must be prepared to dabble on the boundary of disaster.? - Stirling Moss

Online Jasonb

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Re: Stephenson's Rocket
« Reply #54 on: May 13, 2020, 07:34:23 AM »
Brian you could mill the spokes out of a disc of 3/16" plate, add a hub and rim much like you do with flywheels, it's just rotary table work.

Offline doubletop

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Re: Stephenson's Rocket
« Reply #55 on: May 13, 2020, 08:08:17 AM »
Brian you could mill the spokes out of a disc of 3/16" plate, add a hub and rim much like you do with flywheels, it's just rotary table work.

John 'Bogstandard' had posted a 'howto' on Madmodder but the images are now missing. However, some years ago I had downloaded it and put it into a .pdf. As the resource is now effectively unavailable I doubt if anybody will complain if I post it here.

The files are too big for adding as attachments here so links are to my Google Drive, so be quick as I may remove them at some point in the future

https://drive.google.com/open?id=19Et4LAY95csaxEPOO0XNT4OOAJ_vmucA

https://drive.google.com/open?id=1odIQxWjm8yn-m_lS9z5KQ1a1a7sFHKZU

https://drive.google.com/open?id=1KJuG52I485W14kn4UuKfjvrFJBZekK_P

Pete
?To achieve anything in this game, you must be prepared to dabble on the boundary of disaster.? - Stirling Moss

Offline Brian Rupnow

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Re: Stephenson's Rocket
« Reply #56 on: May 13, 2020, 03:33:56 PM »
Thank you for the information fellows. I do not plan on having a reverse capability. Otherwise, the Northumbrian has exactly the same valve gear layout as I plan on using. I thought of carving the spokes out on a disc, but the Rocket has 12 spokes and I think that would just be too much to carve from one disc.

Offline cnr6400

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Re: Stephenson's Rocket
« Reply #57 on: May 13, 2020, 04:44:21 PM »
I recall reading somewhere that the original Rocket had wooden front wheels and a ball and socket joint from one spoke to the connecting rod each side. Making wood wheels might be less difficult than metal ones.

Another thought if making metal ones - have a waterjet or laser cutting firm cut all the spokes and the hub and rim/felloes in one part, and add "washer" shaped parts to each side of it for rims and flanges and crank plate protrusions. Just food for thought. A few rivets through the stack and some Loctite could hold the laminations together.

Offline Brian Rupnow

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Re: Stephenson's Rocket
« Reply #58 on: May 13, 2020, 05:07:20 PM »
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.
« Last Edit: June 02, 2020, 12:12:58 AM by Brian Rupnow »

Offline Brian Rupnow

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Re: Stephenson's Rocket
« Reply #59 on: May 13, 2020, 05:12:54 PM »
cnr6400--I had the flywheels for the rockerblock engine water jet cut, and although the finished product was very nice, it cost me $100.  I can do a lot machining/fiddling around for $100.