2.5" Gauge Green Arrow Build

[stevendavis]

Been working on this project for a little while now. Lost a few months due to an injury, but starting back up. The boiler showed up, made by Western Steam. Cost way more than expected due to the exchange rate and tariffs now imposed on UK products. Boiler looks great though. They did a wonderful job on it. I've also got the crank pins done, and the eccentric for the lubricator. Still have to harden the pins and paint the wheels before I do the clocking.

[Kim]

Sorry about the extra expense, but it sure is a pretty-looking boiler!   

Kim

[stevendavis]

Sorry about the extra expense, but it sure is a pretty-looking boiler!   

Kim

They did a really good job on it for sure.
I'm starting to work on the cylinders some and didn't want to make mistakes, so I poured a test cylinder and steam chest, but after doing some initial machining, it was unusable. I'll probably try again. Looks like some gasses escaped through the sandcore area and up through the port face. I did however make sure my setup was solid to start on the supplied castings.

[stevendavis]

One question I do have is with this being a 3 cylinder engine, do all three need to be 120* out from each other? The prints show the leading and trailing at 120, but no detail on the driving. Thanks

[crueby]

Had to look up that engine, I never knew they did 3 cylinder locomotives like that. Was that engine unique, or was that a fairly common thing?

[Charles Lamont]

Had to look up that engine, I never knew they did 3 cylinder locomotives like that. Was that engine unique, or was that a fairly common thing?

Like what? I am not sure what you are asking.

[crueby]

Had to look up that engine, I never knew they did 3 cylinder locomotives like that. Was that engine unique, or was that a fairly common thing?

Like what? I am not sure what you are asking.

Having a third cylinder in the center of the frame, rather than just one either side in line with the driving wheels.

[RReid]

I find the Green Arrow to be a very handsome locomotive, and yours appears to be coming along great. I keep a digital copy of Martin Evans' Model Engineer build series for a gauge 1 version, just in case...

[uuu]

Had to look up that engine, I never knew they did 3 cylinder locomotives like that. Was that engine unique, or was that a fairly common thing?

There were quite a few three cylinder designs in the UK.  And a few in other countries.  The challenge on many types was not how to connect the crank of the middle cylinder, but how to drive the valves.  There were "conjugated valve gears", using the motion of the valves of the two outside cylinders in combination to drive the middle one.  Here's an article on one such system:  https://en.wikipedia.org/wiki/Gresley_conjugated_valve_gear

Wilf

[crueby]

Had to look up that engine, I never knew they did 3 cylinder locomotives like that. Was that engine unique, or was that a fairly common thing?

There were quite a few three cylinder designs in the UK.  And a few in other countries.  The challenge on many types was not how to connect the crank of the middle cylinder, but how to drive the valves.  There were "conjugated valve gears", using the motion of the valves of the two outside cylinders in combination to drive the middle one.  Here's an article on one such system:  https://en.wikipedia.org/wiki/Gresley_conjugated_valve_gear

Wilf

Thanks Wilf!

[Charles Lamont]

Crueby - apart from the weird and wonderful configurations of the earliest locomotives, most British locomotives before 1900 had two inside cylinders. Two outside ones gradually became more normal after that.

The early three cylinder engines were mainly compounds, with either 2 outside HP cylinders feeding one large inside LP cylinder, or, much more commonly, a single inside HP feeding two outside LP cylinders.

 Simple expansion 3-cylinder and 4-cylinder locomotives started to appear about the turn of the century. Three cylinders were quite common in larger engines, while the four cylinder arrangement was mainly applied only to the largest express designs. The LNER, LMS, and Southern railways used 3-cylinder locomotives extensively, while I am not aware of any on the Great Western.

https://kesr-mic.org.uk/resources/The+Modern+3-Cylinder+Locomotive.pdf     

[stevendavis]

Thanks Charles!
That resorce is showing that I need to clock the center crank at 114*, as the center cylinder is offset 6*. I'll give that a go. The little book says to possibly wait until your ready to time the valving, but I don't see how I can properly build the conecting rods without setting the wheels first!

Yep,
The outside motion moves the inside valve by way of combination levers.

[Kim]

Wow! This certainly fits in the "Learn Something New Every Day" category!  I had never heard of 3-cylinder steam locomotives!  This is very fascinating. Thanks for the links. Interesting reading.

Kim

[crueby]

Wow! This certainly fits in the "Learn Something New Every Day" category!  I had never heard of 3-cylinder steam locomotives!  This is very fascinating. Thanks for the links. Interesting reading.

Kim

Many of the Shays were 3 cylinders, no compounding, those were easy to see since tgey were hung together on one side. Having a compound third should give a nice steam savings. Thanks for the info!

[Kim]

Wow! This certainly fits in the "Learn Something New Every Day" category!  I had never heard of 3-cylinder steam locomotives!  This is very fascinating. Thanks for the links. Interesting reading.

Kim

Many of the Shays were 3 cylinders, no compounding, those were easy to see since tgey were hung together on one side. Having a compound third should give a nice steam savings. Thanks for the info!

True, I knew about the Shays. Thanks for mentioning that Chris.  I guess it was the non-geared locomotives with 3 cylinders - two on the sides and one in the middle - that were new to me!

Kim