What are the differences between Railroad Supply Corps.' CP173 and Disney's? Looking at pictures, it seems to me that the Disney engine has larger diameter cylinders, but if this is true, how much bigger are they?

My understanding of this company is they were the original makers of the commercially available CP 173 modeled after Walt Disney's. I suppose there was a lot of interest in Walt's engine so this company was asked to make replicas available to other live steam modelers. In 1970 or so the original company was either aquired or bought or changed names to Railroad Supply Corps and continued to offer the CP 173 and eventually expanded to other models of live steam and rolling stock.

I once saw a catalouge from this company and there was a short back history, which is why my memory is sketchy. I know it was not at the Barn. It was in someone's private collection or even possibly a book I read conerning the real CP 173 and her history.

I am not sure, but if you are building your own CP 173, the carolwood site was offering blueprints and parts from when R Broggie Jr was making the Lilly Belle II. I don't know if the parts are still available but you could contact them on the web site. Also contact RRSC and ask them the ?? directly and get their history. I think it costs somewhere in the neighborhood of $20k to home build a 1/8 live steam and more to have someone do it for you.

Hope this helps just a bit.

Keep in mind that the outside dimension of the cylinder means nothing, it's the inside dimension that counts. Maybe the difference is the strength required from iron casting versus a steel casting. There has been metalurgic progress in the last 50+ years.



happy rails

One of our Carolwood members did a pretty complete comparison. The major differences are in the lead truck wheels and cylinder diameter. While the outside dimentions of the cylinder are the same, the bore on the Railroad Supply model are smaller, 1 1/2 if I remember right. The Disney 173 is 2 1/8 I think. As for the lead truck, I think Railroad Supply made theirs smaller to they could go around a tighter curve and not have the wheels hit the sides of the cylinder. That is my opinion, not based on ay facts I can find.
From what we have been able to find, Railroad Supply produced their 173 for a more commercial market. It is easier to build in some areas and will still produce a great looking loco.
Yes, both Castings and prints are available from the Carolwood Pacific Historical Society. Just go to the web site and e-mail Michael Broggie.
If you have any questions, let me know.
Thanks
Bill B
Crew Chief, Disney Barn, CPHS Board of Gov.

Thanks. Would you also happen to know the piston stroke, or where I could find that sort of information? M. Broggie's Railroad Story says the Disney 173 "had a tractive effort of over 2000 pounds" and could handle "up to 12 adult passengers"(pg167). So how much more power did it have in comparison to RS'? The reason I ask is some people at RLS complained about the lack of power the RS version has, and I hope to eventually build a CP173.

If you know the distance from the driver axle center to the center of the crank pin, that's half the stroke. The stroke on full-scale 4-4-0's of that period was commonly 24".

If I may ask, what is the RLS? And are drawings of Central Pacific 173(NOT the Lilly Belle) available?

Riverside Live Steamers, sorry. And Railroad Supply claims theirs is "the popular Central Pacific #173." http://www.railroadsupply.com I'm still pretty new to the live steam hobby, so I don't know everything behind why what happens works and how to do the proper calculations to project data.
Anyhoo, so what you're saying is a common stroke was 24", so scaled down to 1/8 that would be 3", so a reasonable estimate would be 3" for the stroke, which leaves just the difference in actual cylinder diameter to account for the [supposed] pulling power, right?

Power of a steam locomotive is not constant, that's why they're hard to design. Tractive effort is the measure of how much draw bar pull can be exerted, horse power is how much work is done, and a steam Loco has zero horse power until the train is moving. There is a little program that will let you design a steam Loco and calculate the results:

http://www.steamlocomotive.com/misc/TractiveEffort.shtml


Have fun speculating.

Bill B. Happy barnday.

Note: The Railroad supply page lists the Cylinder liner as 2.25 Dia. X 4

So it is probably the same as Lilly Belle.

http://www.railroadsupply.com/4.4.0.g4.html

Theoretically, all other factors being equal, you're right.