Topic: 7/8" Scale Class A Shay Construction Series

[locodan]

Russ,
I will freely admit that I know little to nothing about front end design. I know that there was some talk on Steam_tech about that exhaust system and it was proposed on one of the Shays at Georgetown CO. One of the guys who posts on Steam_tech I think wrote a book on this subject that is available from Camden Press.

It is a bit premature to think about front end design as the engine parameters have not been established on this thread much less the boiler, so it is a bit like the cart before the horse. The boiler shell will only be 2" in diameter so that might be somewhat small to have anything fancy in the smokebox. I am planing a boiler similar to Kozo's second Shay design only this one is not a wagon top it is a straight top so the shell will extend to the backhead.

One of the things to keep in  mind is that any cad system is much more accurate than a drafting board. This shows up in valve gear design when either drawing along with a text book or attempting to replicate old designs.

I drew Bilgram diagrams for all the 1924 data using the angle of advance found on the DCI's. I used the lap dimensions to solve for cutoff. NONE of the full gear leads worked out to exactly 1/32". They were close to sort of close but not 1/32" It is stuff like this that makes me wonder if I am getting it right.

This is a vertical engine so I always draw the diagrams vertical. Top dead center or TDC & BDC is much  simpler that crank end and head end.

The attached drawings show the general layout of Bilgram. They does not cover inside lap and a few Shays had inside lap but for now this is just the data presented so far.

The layout procedure is simple and with cad I use full dimensions for the stroke which is much larger than the valve travel. It was common to use 2 different scales so the drawing could be as large as the paper at hand.

The lap circle with a radius equal to the lap is drawn with the center point at the intersection of the angle of advance and the eccentric circle or point F. It can be seen that the lap circle does not touch the line AB. The distance between the lap circle and line AB is the lead in full gear.

To calculate the cutoff draw a tangent from point O to the lap circle extend this line to the crank circle or crank pin path to point G. Construct a line at right angles to the stroke line AB that goes through the point G the cutoff point. The ratio of this distance measured from point A and the full stroke expressed as a percent is the cutoff. As I said the diagram is a graphical calculator.

Now if the lap is reduced and the same lead is used it can be seen that the angle of advance also gets smaller. I suggested this in my article in SitG and later I found data in the prints that the LLW engineers used this in practice. Some of the early Shays had either an angle of advance of 30 degrees or 22 degrees. I found a note on the valve that as drawn it was for 30 degrees. To make the 22 degree version of the valve the amount to machine off the ends of the valve to reduce the lap was given.

Bilgram's diagram is in the ICS books and Audel's but the best book for this method is "Slide Valve Gears" by Frederic Halsey.

I think this diagram is simpler than Zeuner. I have a line drawing of the machine built at the University of PA that was built to the Zeuner specs. It was a very clever device with a rotating drafting board and a pen was attached to the slide valve. I will post it if anyone has gotten through this far enough to read this.
Cheers Dan

[russ]

Here is a wild idea.  We might want to consider designing and installing a Lempor exhaust system in this beast.  A close friend of mine is very expert in Lempors and has worked with experts who are applying Lempors to 1:1 scale locos around the world.  He installed one in my 3.5" to the foot model of a 2 foot gauge English quarry engine (when he owned it) with great success. For more information on what he did, visit http://tinyurl.com/g9bsq.

Now, he also built one for my British Railways 1" to the foot 9F 2-10-0 and made a significant difference to the steaming of the engine.  7/8" to the foot is not far off 1" to the foot. So it should work here as well.

Now these engines of mine are coal fired engines.  There is some debate as to whether one achieves the same benefits with gas-fired boilers.  We need to consider that .

If everyone is game, I could probably at the right time convince him to help us work through the calculations which should work for a Shay as well as a traditional steam engine.

I will be disassembling the 9F to make some further changes to it this winter and will take pictures of the bits and pieces of the Lempor and post them here.

Hope this is good food for thought!!

Russ

[locodan]

Although the specs. so far only give the angle of advance and valve travel and the lap and lead, this is way more than we need to draw a valve diagram. All the DCI'S have the angle of advance and valve travel, if I add one more fact that is all we need to get started. The fact is ALL the Shay engines in production in 1924 had 1/32" lead in full gear. This with the angle of advance and travel is all we need to draw a Bilgram diagram. It is most likely enough to draw a Zeuner or Reuleaux diagram, but although I know how to construct both of them, IMHO Bilgram's diagram is simpler to visualize.

The valve gear diagrams were used for two purposes; they are graphical calculators to solve valve gear problems, and they are also used to compare steam engine designs. All the diagrams work well for the first purpose and which one that is used depends on what information is known. I believe that Bilgram's diagram is much superior for not only comparing engine designs but also for asking the question of what if?

The problem I was having with Docksteader's valve gear program was what is my standard? If I make changes how do I know I have improved things or simply made changes? The answer occurred to me as I was reviewing this design. The valve gear design is the standard. There are 3 types of error in Stevo (Stephenson's link motion) as applied to Shays. These are the angularity of the con rod and the eccentric rods and the offsets of the eccentric rod connections to the radius link. There are methods of timing and compensating the linkage for the desired result. All the valve gear books are slanted to one method or another. It is tough reading and the authors bias does not always apply to marine style engines, the books tend to describe rod engines more than other types.

My next post will show how to construct the Bilgram diagram for this engine. We can then use the sine diagram produced to see how close the valve operates like the standard or Bilgram's diagram. The same process used on the model design should give similar results.

This stuff I am writting here is way to much for my articles in SitG. I attempted Bilgram there and no one I have asked really understood what I was going on about. The cool part of this type of forum is not only can I go back and correct typos, the reader can ASK QUESTIONS of the author. If I can not explain this stuff to this group with words and a few drawings then I do not really understand what I am talking about.
Cheers Dan

[bambuko]

...Is everone having fun now?
Cheers Dan

yeap 
keep going - you have an admiring audience
Chris

[locodan]

A LLW engineering sheet with no date lists the basic specs. for several classes of Shays. The plans listed suggest that this document is from the mid 1920's.
The line we are interested in is:
Class: 13-2
Plan: 1553
Rigid WB: 48"
Total WB: 18' 10"
Light weight
Front: 12700
Rear: 11300
Loaded Weight
Front: 14100
Rear: 16500

Engineering specs. listed on the drawing card index (ACHS collection) include:
Boiler
27.75" straight, Press. 160#, Coal fuel
Firebox (copper)
L=25.5",W=22.375",H=39.5"
Tubes
Number=32,Size=1.75",Length=72",Gauge 120 Brass. Note the gauge is usually 12 for the tubes so the record must be an error.

Total Empty Weight 24,748 taken from packing list
Water Capacity 400 gal.
Driver dia.=22.5"

Frame 7"-15# I beam
Frame channels 7"-12.5#

From the 1925 Shay catalog
Class 13-2
Extreme Height= 9' 5"
Extreme Width= 8' 3"
Min Gauge= 24"
Sharpest curve= 50' Rad.
Lightest Rail= 12#
Coal Capacity= 3/4 ton

A set of engine specs are needed for Docksteader's valve gear program.
The only thing listed on the DCI is angular advance =24 deg. and valve travel = 1.5". The Valve Motion engineering sheet at ACHS lists the same info plus outside lap=17/64" and lead in full gear=1/32"
The rest of the engine specs. that I used are from the LLW drawing cards. I will point them out when I post the file and screen shots of the program.

Wow that is an impressive set of specs. I wish I could do that for every Shay built but some of the info has been lost to time. Is everone having fun now?
Cheers Dan

[locodan]

Hi All,
I forgot to mention a key document for any Shay build with a shop number less than 3000. This is the drawing card index. These are about 18"x24" and list most of the drawings used to build a Shay locomotive. I have about 2500 of these sheets in my collection all of them in known existance. There were two sets of these and one is in Lima OH at the Allen County Historical Society. The other set is not as complete and is at the Califorinia RR Muesum at Sacramento. The drawing card index DCI for shop number 2800 is only in the ACHS collection.

The standard engineering specs for this class of 13-2 Shay is:
Gear Ratio: 3.08
Tractive Power: 6050
Max. piston speed: 469
Speed Limit: 6 mph
Engine Hp: 77
Boiler Hp: 92
Grate Size: 5.71 sq.ft.

Note: Engine H.P. is based on Maximun piston speed for standard gear ratio.
         Boiler H.P. is based on steam consumption at maximum piston speed.

These specs. are from the Standard Shay Locomotives engineering sheet dated 5-7-24
from the ACHS collection.
Cheers Dan

[locodan]

Hi All
I have been writing a series on Shay engineering in Steam in the Garden for about 3 years now. The drawings in the series are all based on LLW drawings with the only exception of the vertical boiler. That used a textbook submerged tube vertical boiler drawing and modified it for the printed specs. of the Lima version. If you are looking for Shay engineering carefully prepared from Lima prints then you need some back issues.

I have been missing my shop so I plan to build a 7/8" Class A Shay and write up the process in SitG. The LLW plan I will be using is Plan 1553 which is LLW card 16205 and available from the Allen County Historical Society. The detail index for this plan is index 73 and that LLW document is available from the California State RR Museum.

There are several 2' Shays that were built to Plan 1553 and I will copy the list if anyone needs it. The one I picked is S/N 2800 which was used at the Mapleton Tramway in Queensland Australia.

I have drawn the whole locomotive and scaled the steam engine for 7/8" scale. I spent a bunch of time attempting to understand the LLW system of design especially valve gear design because I found some of the Stephenson valve gear designs do not follow the standard book rules as to the length of the eccentric rods and the radius of the link. This caused me to question my understanding of the design rules and look harder for the answer.

I checked my Docksteader file for Plan 1553 which is the crankcase style of 2-6x10 Shay engine, and my scale plan and the graphs need to be scaled properly so a engineering comparison can be made. I will get to this soon and post them for review. I was a Marine Engineer and this is model engineering do not spare my feelings I want to know if I am barking up the wrong tree again.

If the prototype engine is a success I will make extra castings for folks who want them. I use Kozo's methods to make wax masters so the series will have drawings of the parts plus photos of the wax before and after it was assembled. That way the whole affair could be made using metal and Kozo's methods with no castings required.

Cheers Dan Rowe