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

[locodan]

Hi all,
I am not trying to be a know-it-all here. I just read a line in Martin Evens book on valve gear about timing and it made my head hurt. I will have to read it a few more times.

If anyone has questions about what I am writing please ask. If I can not explain it in a bar with a napkin then I do not understand it. That was my test while I was at sea and it still is today.

For those feeling a little intimidated, take my perspective. I just announced that I was going to start a Shay construction series and I have never built a locomotive.
Cheers locodan

[locodan]

The rapid prototyping stuff made my brain go operating rocker grates, but that is not the cheep or simple solution. Plain grates were used for coal but rocker grates were fitted to both the Mapleton Tramway Shays. I think that there was also a dead plate fitted in the front but I have to check photos. It would be nice to have working air dampers and the dummy controls for the dead plate and rocker grates could be used for removable pins to drop the grates. A flange with a plug could be used for the gas line, but the location would be dependent on the gas burner configuration.

The MAIN issue is still the engine design. I have played around with the dynamic variables using Kozo's design and LLW designs. There seam to be a wide range of Stevo valve gear solutions that will work. The books of the day vary about what event to optimize a steam engine for, and it was different for types of engines and the service they were designed for.

I am still working on the presention of the Docksteader files for both the LLW engine and the model version. Cheers Dan

[Ferd]

Might be an easy enough task with a ceramic burner - just redesign a second grate/ burner holder and variation in the drafting may be necessary. I like the quite appeal and heat of coal and at the same time propane / butane is so nice and clean. Designed well the heat output can be more than sufficient. cheers Ferd

[russ]

Ah .. so you are looking to coal fire it .. might be interesting to think about cofniguring the firebox for either coal or butane/propane firing .. be able to switch grates for a burner and vice versa .....

Russ

[locodan]

The data can be used to calculate the RPM of the engine. The speed limit and the driver diameter or the piston feet per minute and stroke can be used. I used one to check the other and I got 282.4 RPM and 281.4 RPM this was slide rule days so that is a close match and checks the data. Lets round off to 280 RPM now the required model boiler heating surface can be calculated. I listed the size of the box it should fit in. Hopefully we can reach protypical design speed but if we can not this is not a racing machine so it is not an issue as long as we can get a nice run time. Which with coal as the fuel should be no problem. A hand pump in the tender or a small injector or both can be used for feed water.  Cheers Dan

[Ferd]

Hi Dan
Thanks - I thought rapid metal prototyping was full axis cnc for metals (aluminum, brass, stainless etc...) costly and restrictive on cavity shape etc..  - FDM uses ABS and is functional and I thought required after machining to be accurate. SLA - non self supportive and should be most economical as it has been around since 86. SLS - great on complex parts and good finish easy clean up.  Of course I could be missing something all together, known to do that (more often than I like to admint) 
cheers Ferd

Personally I would love a desktop inkjet rapid proto type printer.

[locodan]

Ferd,
That engine is S/N 2091 which is very similar to S/N 2800. Both Shays were built fot the Mapelton Tramway. The only difference is the boiler was a different drawing which can be seen in the builders photos because S/N 2091 has a slightly taller steam dome. The only other real difference is the right truck box and gear. S/N 2800 used a 3.08:1 gear and S/N 2091 used a 2.47:1 gear. This made the right box change slightly for the new gear. The cool thing is the truck sets still exist and one set is on the combined Shay called Shay. The other set is at the Illawarra Light Railway and will be used for the 2' rebuild of S/N 907?. I am a member of the society I have tried to help with drawings but they seam to have it under control.

The book for the Mapleton Tramway is very good with a bunch of very cool cool cars. It is available from: http://www.lrrsa.org.au/Nlr_Pubs.htm

Bevel gears are the other hassel for Shay builders. Modern gears always have a shorter face length and the proper hunting tooth ratio is never avaible as bevel gears are designed as a set and do not mix and match for the most part. I know a whole bunch about the methods to manufacture bevel gears both modern and historical.

The stuff made with rapid prototype was a ABS type plastic. At least one outfit in Houston TX can do this in steel!! The price of the stuff is comming down. I drew the 9x8 cylinder at least the bore in 3D for my mold design. So why not just finish the drawing and have it made in metal? It takes 3D drawings for rapid prototyping. I am slow with 3D but I see that I will be doing a lot more of it soon. Truck boxes in steel? Anyone have a price for 12# rail?  Both of these links are Houston TX firms.
http://www.texcast.com/
http://www.dserapid.com/
Cheers Dan

[Ferd]

Hi Dan
Most rapid prototype printers I have seen are wax based are they not? I have seen a lot of outputs and with little clean up usually a piece of nylon will clean up surface imperfections, (dimples, or lines). From what I have seen so far the cost is fairly high. I should look into sources since we are in one of the most high tech areas in Canada, thanks to R.I.M..
Wax works well with silicone mold material.
cheers Ferd

PS - how similar are the shays that ran in the Australian Sugar industry. ie. including jpg found on http://www.zelmeroz.com/albumquery/index.html

[locodan]

Ferd and all,
On another group the topic has been casting. One of the guys had a truck side frame made with rapid prototyping in plastic for a master. If this stuff gets cheep enough it  might be the way to go with a Shay cylinder. To be correct any Shay with a cylinder smaller than 11x12 had a solid bottom end and was cast with the crosshead frame.

A wax pattern made with rapid prototyping would be very accurate so the bore would only have to be honed if all went well in the casting process.

It is my goal to make an accurate Shay steam engine. I started with S/N 181 which does not have a DCI. That made research just a whole lot harder. Then I had to know why the early Shays had steam chests that extend beyond the bore on the top and bottom. I discovered that the early Shays used a double D slide valve. This design goes all the way back to Wm. Murdock and the very first slide valve which was a double valve. I know the British patent number if anyone has access to 1790 data.

I have not given up on S/N 181 but other Shays are on my drafting board now. My current project the drawing of the 3-18x20 engine is at a stage I hate. It has reverse Gooch gear and I drew all the parts which included the parts that were not used. This engine was a one of and a rare assembly drawing was made of the valve gear only some of the parts were changed. I figured this out and now I have set the reverse lever to show the most parts. The bit I hate is removing all lines to show the gear. Even at 1/2" to the foot a lot of hidden lines can mess up a drawing. I have enough paper space to show cross sections so I think I can get the idea across. Anyone game to build S/N 2570? The sad bit on this engine is I know that it used an Allen-Richardson slide valve but the drawing did not survive.
Dan

[locodan]

Ferd,
I totally agree with your last message, but finescale modeling and model engineering are not always compatable. With the larger scales like 1/5 size I am not planning to deviate from the LLW steam engine design. I have spent far to much time studying the prints to make changes in the design in that scale. Even in the larger scales not many people make a scale boiler. The physics of combustion gas flow do not scale well nor does coal ash but you already know that.

As for the 7/8" scale 2-6x10 engine...
Shays have short connecting rods and even shorter valve travel. A scale version of the engine could be made but I feel that the operating quality of the engine would suffer. The valve travel of the engine for this engine is only 1.5". This scales to about eleven, that pesky decimal before the number is a serious problem for the designer. I did what Kozo did and increased the valve travel. I could have used Kozo's design but then I would not have learned how to design a Shay engine. Kozo used the same valve gear design for both Shay designs. Did anyone else slap their head when he in the last series and book stated why he used .5mm over travel? I have been trying for years to figure that out.
The reason his valve travels .5mm past the steam ports is for future pin slop. That is about 20 thousands of over travel. Compare that to the scale valve travel of 0.11" and it is nearly 1/5 of the whole travel just for future slop. I did what Kozo did and increased the valve travel. That decision makes changes that have to be worked out before metal is cut. If anyone thinks that Stephenson valve gear design is a simple subject, I totally disagree. I have over 30 books on valve gear design and I have read every word in them on link motion several times. I have never taken on a harder engineering challenge and I was a working Marine Engineer for over 25 years.

I have not started the prototype engine yet... some one talked me into a 7/8" car swap project and I have made the drawings but need to start the shop work soon.
Cheers Dan

[Ferd]

Hi Dan
I build two kinds of 78ths models - a quickie project where the overall look is desired, and the scratch built museum quality where building a scale replica of the original is the intent. I think this projects really belongs in the latter of the two. I find building a complete replica in this scale far more rewarding, especially the Shay.
cheers Ferd

How far along are you in your production of the proto-type?

[locodan]

I just checked my drawings for a 7/8" model of the crankcase version of the 2-6x10 Shay engine. It can all be built with out castings, however a few parts I think would either look better with a casting or would save the builder time if a casting was used. The list of castings for this engine will most likely be; 1 cylinder, 2 steam chest, 3 crosshead, 4, connecting rod bottom bearing, 5 valve steam guide, 6 valve stem crosshead.

The design was started as LLW prints so I will provide the scale LLW print drawing for historical reasons and for the few who want a more realistic engine. The only engine bit that needs to be finalized is the bottom bracket. I got bored at that point. The crank bearings are ALL bushings. This was for long lasting service because oil impregnated bronze with an oil replenishment system seamed the best to me. The way I am getting away with this is the crankshaft counter weights hide straight and taper pins. The taper pins are threaded on the ends so they can be removed. The crankshaft will come apart and all the bushings will be slightly modify ed off the shelf items and easily replaced for those folks who run locomotives day and night. The counter weights will be bolted on with a strap just like the real engine, so the pins can not fall out. I am hoping that this is a good system, time will tell.

The first article is scheduled to run in Steam in the Garden issue 100 which will be late next summer. It will be a full view plan 1:1 scale actual plan drawing. This drawing will have way more information than the LLW plan drawing. I do not cut corners with drafting. I use the Carnegie steel book (1921) for the steel and my old drafting book for the pipe fittings. I have a whole collection of real part catalog so all the fittings shown in my drawings are usually from historic sources.

Ferd which crank do you want to build a real scale one or a model version?
Cheers Dan

[Ferd]

Hi Dan
It would be fun to do a trial run on the crank - can provide all the feedback you need.
cheers Ferd

[locodan]

Ferd,
I am way past the design phase for the engine. I can post the crank drawing if you want to machine one. The cool part of a 2 cylinder Shay is angle iron can be used for the crank blank. The eccentrics are keyed on and there in no center eccentric hassle to deal with. I am hoping that if I made errors in the design someone here will notice. I spent a career working on marine machinery and have used a few harsh words to describe a few machine designers now is pay back time.
Dan

[Ferd]

Hi Dan
Thanks for the posts , they are great reads and I am looking forward to the project starting. I know you are still in the engine planning stage are you looking at using Kozo's method for the crankshaft. I have been itching to machine one as per his new book for a 7.25/7.5 shay out of stainless steel. Be fun to have a crack at the same in 7/8ths scale. Cheers Ferd.