Topic: 3' NG Shay design thoughts

[karen9dion]

Thanks for the update.

[locodan]

Hi all, This project is on the back burner because all the folks involved are busy with other things including the 7/8 scale Shay project. The 7/8 scale metal cylinder mold for wax was very sucessfull. The key is holding pressure while the wax cools. My wax pot has a drain valve, so I simply have to switch it to a ball valve and it can be piped to a larger mold for a 1/5 scale cylinder. It will be much simpler to build a larger mold because the steam ports are larger and it is not watch makers work.
Cheers Dan

[locodan]

Hi Ferd,
Thanks for the support of this project and a new space most of the thread is for the 1/5 scale stuff and just the last bit is 7/8" scale. I will post the Docksteader file for the real and 7/8" scale 2-6x10 Shay engine soon. If anyone has opinions on the curves I want to hear them. I used what I believe is the set out rules for Stevenson valve gear on Shays as done by the LLW engineers, but there might be room for improvement. The best book I have found to date on this subject is "Steam Engine Theory" by William Ripper. He covers how to draw an aproximate steam diagram for an engine design. The mean effective pressure a very elusive number can be aproximated with the method. I have not worked an example yet.
I am much more at home on an engineering forum where logic rules.
Ferd I can make screen shots of the Docksteader curves for the Mac users so they can see the curves.
Cheers Dan

[locodan]

Hi all,
I just got a new load of prints for S/N 797 from the California RR Museum. The drafting work is progressing and my drafting help is getting up to speed. It takes a bit of time to draw all the prints and discover which set of holes is the one used for the Shay desired. Then the model engineer has to wave his magic wand and one brand new shiny Shay appears only somewhat smaller than the actual machine.

I have announced a Shay construction series on the 7/8" scale groups and as my approach is model engineering not plastic models (no digs meant I just do not care to build in plastic) there should be a space here for 1.75" track.

The Shays for the construction series are S/N 2091 and S/N 2800 the Mapelton Tramway.
There is a book on the Mapleton Tramway by John Knowles. Check for the Australian Narrow Gauge Railway Museum Society they are the distributors.

Several of the 2' Shays were built to this plan the list is S/N 1623, S/N 1654, S/N 1777, S/N 2084, S/N 2091, S/N 2102, S/N 2282, S/N 2487, S/N 2585, S/N 2678, S/N 2693, S/N 2800 and S/N 2806. For the 18" guys S/N 2550 was 19.6875" gauge which was the smallest gauge Shay built.

The Mapleton Shays had builders photos which are online at:
http://www.shaylocomotives.com/data/dataframe.htm
Just click on the shop numbers 2091 and 2800. Some of the other numbers should also have photos with the owners.

The series will run in Steam in the Garden starting in the spring or the summer. I hope to have castings ready when the copies get to the builders.

Cheers Dan Rowe

[locodan]

Hi all,
I sometimes get a little lost in the techinical details. The real advantage of print 108 and 138 being the same drawing is the cylinders were interchangable. This is good because the cylinders I am planing will work for any early 8x8 or 9x8 Shay with either 2 or 3 cylinders. The Gilpin numbers 3, 4, & 5 and a whole bunch of other Shays will be possible in this scale. Cheers Dan

[locodan]

Hi All,
The engine drawings arrived. The cylinder drawing LLW card 138 is a tracing of LLW card 108. (The one posted in this thread) The only difference is about 3 dimensions have changed, but the drawing is a tracing so these dimensions are not what a scale ruler reads. If I did not have both prints in my collection I would be very confused.

The crank bearings for S/N 797 is on LLW drawing card 5080 and it is the same design as the wedge adjusters used with the one piece crankshaft brackets. The center bearing is 3/4" shorter then the three bearings on the cylinders. I now see that most of the cranks were changed when the crankshaft brackets were introduced so all of the new crank bearings would be the same size.

A nearly a complete set of drawings for S/N 797 are on hand, with a few still on order.
The drafting team will be busy for a while.  Cheers Dan

[locodan]

Hi all,
The engine drawings will be on my desk in a week or two, so I have started on the truck drawing. It is not easy to grasp the meaning of all the hidden lines in the truck boxes with out a lot of study. They were designed with oil cellars and oil reservoirs. I am thinking the best way to to make these parts is a bronze casting. Why not just scale the original drawings and divide by 5? The journal is 3.375" OD X 6" long so we can calculate the load on the actual bearings and make sure we do not exceed the scale load. Cheers Dan

[locodan]

Hi Ferd,
If the mold design works I will make castings for other builders in either scale. The small scale uses a lot less metal for an experiment.

The other advantage of a metal mold is the parts are only held by alignment pins. This leaves a little gap for the air to escape when wax is injected into the mold. With a rubber mold small cuts are added in problem areas for the same purpose.
Cheers Dan

[Ferd]

Hi Dan
Sounds very intriguing - are you planning on selling the castings - or are they  just for personal use. Since I model all my  large stuff in 1/5 I am somewhat ok very ok extremely interested. cheers Ferd cc

[locodan]

I am designing a metal mold for the 8x8 cylinder. The advantage of a all metal mold is it will not flex like a rubber mold. I started this design for 7/8 inch scale and plan to finish the small scale cylinder to work out any bugs before I make a 1/5 scale mold. I have most of the drawing done in 3D cad. The fun bit with 3D cad is a test piece can be made in cyberspace with the mold drawing.

The 1/5 scale 9x8 engine will have to be cast in 3 sections at least because the flask has to fit under my bell jar when I vacuum the investment. This will make it easier to machine the cylinder. The separate parts can be joined with silver solder.
Cheers Dan

[locodan]

It will be a while before the 9x8 Shay cylinder drawings arrive so here is the 8x8 cylinder. The Gilpin engines used a stub version that was 47" from the center of the cylinder to the crank. This is part of a drawing that was in my first article on Shays in Steam in the Garden. The scale is 1/5, but legal paper 8.5"x14" is required. Cheers Dan

[locodan]

Hi Ferd,
All the Stuart cylinders I mentioned are cast iron, and this would require extra care to dry and oil the cylinders to prevent rust.

Gun metal is less maintenance and chrome plating had not occurred to me. the only cylinder size in this scale/gauge with a separate cylinder barrel bolted to the crosshead frame is the 11x12 which is available from Ulin.

For any other cylinder size to reduce the complexity of machining the cylinder bore, a joint similar to what Kozo designed will work. Hopefully the lower section of the special 9x8 cylinder can be cast as one piece.

As for the bearing boxes for the trucks. I have successfully lost wax cast all these parts for 7/8" in gun metal, with separate split bearings. I am sure I can do the same in a larger scale and using larger taps will be a relief. The one thing that I have learned with casting Shay parts is the closer to the actual part the better the result. I simplified a few of my early parts and extra metal can lead to problems when the metal cools.
Cheers Dan

[Ferd]

"Has anyone heard of using a cast iron liner and casting bronze around it with the lost wax process?
Cheers Dan" Hi Dan - I am usually timid in using cast iron as it has high rust tendencies. Gun Metal is my metal
of choice - the other approach: one of the highly experience modelers at our club  has used, is bronze cylinders that were very finely honed then taken and the inside of the cylinders chromium plated. Produced a hard mirror like surface that will not interact with the pistons. I have heard too many rebuild stories with cast iron cylinders. Just a thought.
cheers Ferd

[locodan]

Chuck,
I have been thinking 7/8" scale for too long. I have a lost wax setup that is large enough to handle this scale. I chose vacuum casting just so I could handle larger parts.

If anyone wants a list of all the 3" Shays with a 3-11x12 cylinders to use some or all of the Ulin castings just ask. I was one of the mechinical data checkers for Shaylocomotive.com so all that mechinacal data and much more is on my computer.

I just checked the 8x8 cylinder drawing which is I am reasonably sure very similar to the 9x8 cylinder. The steam passages are .125" by 1.4" in this scale. That is large enough to make an investment core with a metal core box. I thought of this with 7/8" scale but the core is tiny and when the investment is vacuumed I thought that it would not hold up to the force.

Has anyone heard of using a cast iron liner and casting bronze around it with the lost wax process?
Cheers Dan

[chucka]

Dan,

Yes Ulin's castings are still available and they are produced by the lost wax process and although I have never seen any personally, I have heard they are very nice.  Ulin Locomotive Works does not have a website, nor do they have email.  Either snail mail or telephone for communication.  I also know that it takes quite a while to receive casting orders when placed.  The wheels (cast steel and the longest to get) can take up to 6 months.

Chuck