another new shay newbie

[cmitcham]

hi group:

i just got kozo's new shay book, and i am another wanna be scratchbuilder. there is no 89mm gage track nearby, but there is a very active live steam group with 45mm track, so i'm wanting to scale the loco down. my history is 2 rail o scale, so i'm not quite up to speed on these larger scales. i think i understand that kozo's shay is 3/4", or 1:16 scale. so if i take kozo's dimensions X 16 / 20.3, then i will have a 1:20.3 scale model where a 36 inch narrow gage trucks would ride on 45mm model track. is this correct?

i have found ed hume's blog about scaling kozo's climax by 5/6 to fit english material sizes better. i modelled the shay frame rails, end sills, and truck bolsters in cad, and when i scaled by 5/6 or 16/20.3, the standard inch sizes i come closest to don't change. for example, the frame rails are 6x18mm. scaled by 5/6 makes 5x15mm. scaled by 16/20.3 makes 4.73x14.19mm. the closest bar i see at onlinemetals.com is 3/16" x 5/8" fo either scaled dimension. i only checked these three pieces, so maybe adding the rest would show that 5/6 scale makes english sizes easier, but i don't see it yet. i can't believe in this day and age, that i can't order metric sized brass or steel bar stock here in the us.

i appreciate any advice or help regarding building the shay to run on 45mm track.

calvin.

[Ed Hume]

Hi Calvin,

The way to have even dimensions is to scale each 1mm to 1/32". This is what I did for the Climax, and it is not 5/6. Then you have the issue of truck width. Kozo's plan is for standard gauge track. To adjust for narrow gauge, you then subtract width in the axles and truck parts to arrive at the desired gauge. For the Climax, I subtracted 1.089" from the truck widths to fit the track.

Now we come to the shay. If you convert each 1mm to 1/32", you get the part sizes approximately correct. The pistons and cylinders are 1/2" diameter. As with the Climax, you then subtract width in the trucks to move the wheels in for narrow gauge. If you only do that, the motor shaft is not aligned with the truck drive shaft. You have to reduce the diameter of the boiler and tilt the motor to line up the drive shaft. Take a look at this drawing, Shay Concept B86 T5 which is in my Shay Set on flickr. The boiler has been reduced in diameter to 86mm and the motor has been tilted by 5 degrees to get the drive shaft to line up. A competing idea, raised in a recent post on this BBS is not to change the boiler and motor mount, and not to change the drive shaft position, just add spacers to move the wheels inward.

I am using 3/16 x 5/8 standard steel for the frame which is +2 units taller than Kozo's 18mm - since the plans had to be changed substantially, I adjusted for the available size rather than machine it to be 18/32" tall. You likely want to review my other photos in this set - it has been 4 years of work and I am not done. This is not a project to be undertaken without understanding the degree of effort required. There are other sets on flickr for the shay boiler, the Climax, and the Heisler.

Regards,
Ed

[cmitcham]

thanks ed. i don't think mucking around with the engine/drivetrain geometry is something i should undertake on my first project

what are the pitfalls of scaling it to 1:32 and staying standard gage on 45mm track?

[kvom]

As I've seen on the A3, rescaling is not as simple as multiplying by the scale factor. That's because the track widths are not at the same scale as the locomotive. Kozo had a few dimension errors on the 1.5 scale A3 for this reason. What it was necessary to do first was calculate the scaled width of the frame so that the loco's gauge matches the track (Kozo provided this accurately. Then any part that lies completely inside or completely outside the frame can be scaled directly. Anything that crosses the frame (e.g., bumper, footbplace) must be dimensioned as the frame width + the portion outside the frame at scale factor.

[Ed Hume]

Calvin,

If you were to go scale by 1/2 and make the corrections for the truck width, there are some pitfalls. Kozo has some small fasteners in his plan. You cannot simply choose screws that are 1/2 the diameter. Even when you can, you have to check that there is enough space to fit a wrench or nutdriver - as things get smaller, they get closer together. When you have a drilled hole near a raised edge, the raised edge may prevent a center drill from being able to start the hole. As parts get smaller it gets challenging to hold them, and the precision required is higher than it is at 3/4" scale. Kozo's choice of 3/4" scale is an excellent balance of material cost, ease of machining, and the satisfying gestalt of the finished project. The new shay at half size would be a very difficult project. In my own work, I do not use fasteners smaller than 0-80 - I make design changes to avoid needing anything smaller.

Even at full size you want to think twice about tackling the new shay as a first project. My advice is to build some simple projects and build up your skills and shop tools. You need to have tools such as tap and die holders for your lathe and mill, and get comfortable with machining skills. You might consider building just the motor of the new shay full size with a mounting stand as a project. The crankshaft is a worthy challenge by itself. I'm not sure that the crankshaft can be built at 1/2 the size of Kozo's plan using Kozo's techniques. At 4mm for the bearings, the shaft may lack the rigidity to avoid bending while it is being machined.

I built two simple engine projects and several shop tools before tackling the A3 in 3/4" size. The A3 is much less work than the new shay. I probably would no longer be in the hobby if I had tried to start with the new shay. Take a look around for projects like the minikin or Elmer's engines for a first project.

Ed

[cmitcham]

well thanks again both of you. i'm really liking that build the full size engine idea

[daveb1]

Hi Calvin

I agree with Ed's comments about not starting with the "new shay". I started building the new shay 5 years ago and still have upward of a year left. I am doing it in 3/4". Like you my initial venture into live steam was 20.3 on my own garden RR. After a few years of this I developed the itch to move up in size and joined the Waushakum Live Steamers who have a highline running 3/4 and 1"

If I were to do this over the A3 would have been my choice. There are just a lot of parts on the shay that take a lot of time for a beginner machinist. I would have been steaming with the A3 by this time. The A3 build also does away with the metric conversion. By the way there is a company in NY(?) that does metric metals. Can't think of their name but if you do a search you should be able to find. You pay big $$ for their metric.

One thing I have enjoyed building the shay and hope to have it running this year





Dave

[kvom]

Building a 1.5" scale Loco means using steel vs. brass. No need to buy metric stock, just imperial that's large enough and mill to size. Steel boiler vs. copper.