Southern Pacific Steam 2020

[bob turner]

Better add that small steam before this thread drops off the bottom:

This one is a T-32; a 69" drivered Harriman ten-wheeler. It carries a T-31 number - the 2355 actually survived, albeit covered with stucco and handrails. It is my only ten wheeler that is not powered by a tender motor. It has a powerful but tiny heart-pump motor in its firebox.

Sharp-eyed SP freaks will note that the firebox taper is incorrect. Hey, it was my first attempt. I got better after studying 2353's boiler sitting bare at Frasier's boiler works. I hope someday to see that boiler again under the care of Frasier.

Anyway:

[bob turner]

And this is my smallest SP steam. Measured off an HO Roundhouse switcher, converted to 17/64, and running in four days flat.



My only scratch 2-rail switcher with motor in firebox.

[R.K. Maroon]

Bob, I don't recall seeing that ten-wheeler before. It's sharp, Very few of us (I would bet) would have the prototype knowledge required to call out that boiler, and certainly I don't. Nicely proportioned locomotive -- I can see why you would want to model it.

Here is a Scale-Craft P13 from the estate of Allan Wehrle. Allan wanted his models to go to friends and kindred doorstop spirits, so this one went to Bob after it passed through my shop. I would have pined for it but for the outside third rail setup:




John Fisher once mentioned to me that he thought the drivers on these were a bit oversized. I am not sure I see that, but of course I am going on aesthetics and not prototype accuracy (which I have not researched).




A few years ago I passed on a nice 2-rail version of this model sold by Arthur Hayes on eBay. The winning bid was $330, which I think in retrospect was a good price for that particular model. I don't "need" one but I would put it to use if I did.

Jim

[bob turner]

$300 is a tad high for a Scale Craft - but then, doorstops are starting to sell for real money! SP P-10 drivers were 73”, and these are 80”. Too tired to do the math, but in 17/64, 80” is probably close to 75”. Am I confusing the issue?

I will straighten it out after coffee.

The locomotive is 17/64. The tender is usually that lead casting off the Mountain, which was 1/4” Scale.

[R.K. Maroon]

I wondered why Bob was quoting the driver diameters of the SP P-10 when the model in question was a Scale-Craft P-13, at least as claimed by Scale-Craft themselves:



I nosed around a bit on the internet (because I can) and discovered that there were only three class P-13 Pacifics, and they were all owned by the T&NO. The road numbers were 631-633, so at least Allan's model is correct in that regard. Interesting though that the model in the Scale-Craft catalog was not even close. The encyclopedic site steamlocomotive.com indicates that there were no SP Pacifics with the Scale-Craft number. However, and more to the point, it does say that the P-13s were near duplicates of the P-10, of which there were 14. It also states that the driver diameter of both was 73.5". So, yes, John Fisher was apparently correct -- the Scale-Craft drivers are too big.

Here is the link to the steamlocomotive.com page on SP Pacifics:

https://www.steamlocomotive.com/locobase.php?country=USA&wheel=4-6-2&railroad=sp

Jim

[ScaleCraft]

I've had my hands on 3 or 4 of those P-13's. Never had any desire to own on. The drivers are in fact visually too big. The engine was almost an afterthought by SC, a mix of Hudson, K-4 and Mountain parts. Fun to pull the boiler off and compare parts. The boiler just seems too high and ungainly. Prototype probably was, but nothing I wanted to own.

Someday I might get a SC K-4s, but likely.

[bob turner]

All of the Scale Craft Pacifics were nominally 80” drivered. If you scale up a 73 1/2” O scale driver to 17/64, it would require an O Scale driver of just over 78” in diameter. A 78” driver is roughly 1 3/4” in real inches.

Tomorrow I shall measure the SC drivers. Any bets? I could measure some here, but better to do it on Allan’s model, which is on display at the airport.

[ScaleCraft]

All of the Scale Craft Pacifics were nominally 80” drivered. If you scale up a 73 1/2” O scale driver to 17/64, it would require an O Scale driver of just over 78” in diameter. A 78” driver is roughly 1 3/4” in real inches.

Tomorrow I shall measure the SC drivers. Any bets? I could measure some here, but better to do it on Allan’s model, which is on display at the airport.

We're not discussing if all the SC Pacific drivers were nominally 80" . Maroon says data shows 73.5" diameter on prototype. If they're a scale 80, then they are 6-1/2" (or 1/8" roughly) too big.

And the P-13 is just ungainly.
Opinion.

[bob turner]

My first driver diameter post was incomprehensible. I thought my second discussion would be coherent, but I guess not.

Here is a homework assignment:

What is 1 3/4” when measured with a 17/64 Scale, in inches?

[Rufus T. Firefly]

.

[bob turner]

Chemists don't study mathematics?

oops - Martin is correct. Let me take another look.

[R.K. Maroon]

Though I don't normally pay any attention to anything HO, I do find that the abundance of photographs of HO models available on the internet to be a great source of information regarding prototype models. Yes, I know that the HO models may not be all that great in regards to prototype accuracy, but I would bet a dollar to a donut that they are usually pretty close. So here were have the Allan Wehrle's Scale-Craft P13 along side an HO model of the same locomotive (it even has the same road number):





It took a while to get them sized to a "best fit" match. The scaling here matches the height to the top of the boiler and the distance between driver centers. This makes everything match up pretty well. So what jumps out? The cab on the Scale-Craft is too far forward and the trailing truck too far back. The size and shape of the cab is a mess, and the lettering is not even close (except the number is correct, which counts). The domes are not quite correctly placed, and there is a lot of small piping missing (as is often the case on early kit-built steamers). You could nit-pick it to death, but overall I think it's a pretty good model for the era. The one thing that does not jump out at me is the idea that the drivers are too big. Maybe they are, but I don't see a night and day difference.

Jim

[bob turner]

What jumps out at me is the "hunchback" boiler on the heavier SP Pacifics. The HO model is closer, but neither completely captures it. Cabs are easily replaced, but I am refraining.

Come on, Jim - do the math for Dave and Martin. What diameter in actual inches is a 73 1/2" driver in 17/64 scale?

[bob turner]

Okay. I need to measure 631's drivers.
Will do that this afternoon for sure.

Here is the math for determining diameter in actual inches of a 73 1/2" driver in 17/64:

73.5 in x 17/64 " /foot x foot/12 in + 1.626, or roughly 1 5/8" diameter.

Scale Craft drivers around here are 1.620, or slightly too small.

Not sure where the 1 3/4 query came from - but Martin is correct. A Lobaugh 84" driver is 1 3/4" dia, and it scales out to around 79" in 17/64. My Harriman Pacific uses Lobaugh 84" castings, so it is slightly oversize for a 77" driver.

[ScaleCraft]

Too many decades of model manufacturers dummying driver diameters to meet axle spacing with non-exact-scale flanges. All scales, it seems.