2-4-4-2 drawings

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765nkp
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Re: 2-4-4-2 drawings

Postby 765nkp » Mon Aug 28, 2017 6:24 pm

Bill,
Easy fix, use the big cylinders with sleeves. Make all four pistons the same size, run it simple and keep the looks of the compound.
Good luck,
Tim

jkimberln
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Re: 2-4-4-2 drawings

Postby jkimberln » Mon Aug 28, 2017 7:35 pm

Dick Thomas Mallet, now in the CA railroad museum in Sacramento
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DTmallet.jpg

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Doug_Edwards
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Re: 2-4-4-2 drawings

Postby Doug_Edwards » Mon Aug 28, 2017 11:09 pm

Gents,

Here is some of the info I have found in the last 40 years on these locos.

I can only verify that 4 were built domestically, and have never seen any reference to any made anywhere else. Baldwin built 3, and Alco built one in 42" gauge for use in New Zealand. The Alco and the first Baldwin exist today, and the Alco was in steam fairly recently. The Alco is the only NG one of the bunch. There were none of this wheel arrangement in Mexico, standard or narrow gauge.

Alco Mallets had an intercepting valve that switched from simple to compound, and also reduced the pressure of the steam to the operating pressure of the receiver pipe. Baldwin just used a manual valve to fill the receiver pipe, after which the engineer would open the throttle. On the Skookum, I believe it was just an angle valve on the side of the boiler with a extension to open and close it. Later Baldwin Mallets, like the Kosmos, Mud Bay, and Potlatch 2-6-6-2's, had a special valve with a lever that you pulled to fill the receiver pipe, still, it was manual.

Saturated compound Mallets were very viable. Their best use was on a long continuous pull, such as a helper on a mountain grade. Compound locos of some sort were in use for a couple of decades before superheat came in to vogue. Superheat gave a boost in boiler capacity as well as fuel economy, and was a big boost to both simple and compound engines. Keep in mind that most cross compound air compressors were run on saturated steam, and were very viable up to the end of the steam era.

Saturated steam compounds of the era, especially industrial ones, used a higher boiler pressure than simple locomotives. The McCloud River RR had some Baldwin 2-6-2 engines with a boiler pressure of 160 PSI. The #11, of the same vintage and size, was a Vauclain compound and had a 200 PSI boiler pressure. There is a point pressure wise that a saturated compound will not work well due to not enough heat in the steam, which is a direct function of the boiler pressure. Too low a pressure, and the steam will be condensing before being able to do useful work in the low pressure cylinders. This is one of the problems with trying to run a compound model on saturated steam at the pressures we are normally allowed. 100 PSI in the model is not enough. Another problem is the heat losses due to the greater ratio of surface area to steam volumes. A 15" cylinder like the HP cylinder on the Skookum, has a surface wall area of 1130 sq inches, and a volume of 4241 cu. inches, for a ratio of 3.75. A scale cylinder in 1.6" scale has a surface area of 20.1" and a volume of 10.05, for a ratio of .5. The full sized cylinder has 7.5 times more volume to surface area then the model. Add on that the higher losses due to the piping on the model, and it is no wonder that the low pressure cylinders on the model only piss out water from the low pressure cylinders due to the lower volume to the heat sucking surface area. I corresponded with the late Marshall Black about 40 years ago, and he commented on his 1" scale loco, the high pressure cylinders did all the work, and he rarely had any pressure on his receiver pipe gauge feeding the low pressure cylinders.

The only compound Mallet that I have seen that ran well is the 2-4-4-2 built by Ken Schroder. The loco runs well with a clear stack. Ken built the loco with a stainless superheater that goes back into the firebox. I think there was a write up on it in Livesteam magazine years ago that had a diagram of his superheater.

I did a calculation years ago on what the receiver pipe pressure should be on the Skookum for the engines to balance the pulling load. If I remember correctly, the receiver pipe needed to be 60 PSI for the engines to balance with the boiler pressure of 200 PSI that it was built with. You can adjust the receiver pipe pressure a bit by adjusting the valve events of the HP engine.

This is probably more than most wanted to know, but this is some of what I have found over the years.

Regards,

Doug
http://www.precisionlocomotivecastings.com/
Building a 70 ton Willamette in 1.6"
Building a 80 ton Climax in 1.6"

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NP317
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Re: 2-4-4-2 drawings

Postby NP317 » Tue Aug 29, 2017 9:02 am

Doug:
Thanks for that excellent information. Most educational.
~RN

BClemens
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Re: 2-4-4-2 drawings

Postby BClemens » Tue Aug 29, 2017 9:16 am

Yes Doug:
Thanks kindly for taking time to share that grand information.....and you write super well too!
BC

BClemens
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Re: 2-4-4-2 drawings

Postby BClemens » Tue Aug 29, 2017 4:33 pm

765nkp wrote:Bill,
Easy fix, use the big cylinders with sleeves. Make all four pistons the same size, run it simple and keep the looks of the compound.
Good luck,
Tim


Thanks Tim, Good advice!

BC

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Harlock
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Re: 2-4-4-2 drawings

Postby Harlock » Wed Aug 30, 2017 11:45 pm

Here's Ken's engine. I had taken some detail photos for a friend.
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16-05-14_ken-schroeder-run-4165.jpg
16-05-14_ken-schroeder-run-4166.jpg
16-05-14_ken-schroeder-run-4168.jpg
16-05-14_ken-schroeder-run-4170.jpg
San Lorezo Flume & Lumber Co. #2 - "Felton"
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Glenn Brooks
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Re: 2-4-4-2 drawings

Postby Glenn Brooks » Thu Aug 31, 2017 1:02 am

Both loco's are amazing! Where in the world did the builders come up with patterns to make the cylinders? More to the point, where are the patterns now??

Glenn
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Motive power : 1902 A.S.Campbell 4-4-0 American - 12 5/8" gauge, 1955 Ottaway 4-4-0 American 12" gauge

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Harlock
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Re: 2-4-4-2 drawings

Postby Harlock » Thu Aug 31, 2017 10:38 am

Glenn Brooks wrote:Both loco's are amazing! Where in the world did the builders come up with patterns to make the cylinders? More to the point, where are the patterns now??

Glenn


Ken typically makes all of his own patterns for everything.

Contact info here:
http://shaylocomotive.com/page3.html

He has built two mallets, a 2-4-4-2 and a 2-6-6-2. They sit next to each other in the patio room, the other was just off camera to the right.

-M
San Lorezo Flume & Lumber Co. #2 - "Felton"
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Contributing Editor, Live Steam Magazine
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765nkp
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Re: 2-4-4-2 drawings

Postby 765nkp » Thu Aug 31, 2017 10:06 pm

Got any pictures of the 2-6-6-2? I would like to see it too! What size are the drivers?
Thanks Tim


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