Hi, I have just received an HO Bachmann Spectrum 2-8-0 with Stephenson valve gear. Apart from the usual couple of hours worth of tweeking to get it to run to my satisfaction, I am sure the valve gear has something missing.
I know that the Stephenson gear was inboard of the wheels but there should be something connecting to the valve area of the steam box I would think. The model is quite well detailed and does show a couple of rods each side above the second driver. There is a power reverse connection shown on the Engineer’s side connecting to this, but there is nothing connecting to the actual piston valve area on the steam box. It just has a hole where the valve rod should be on each side which to me looks a bit odd. Any clues as to how this should look? It shouldn’t be too hard to add something here to look the part. It doesn’t need to move (although that would be cool if indeed it was possible).
There’s a good diagram of the Stephenson valve gear on page 24 of MR Cyclopedia Volume 1 - Steam Locomotives. The missing parts appear to be the valve stem and rocker arm. Check between the first and second drivers for another hole. That should be where the rocker shaft would be on a locomotive with the main driver in the third position.
The rocker arm is a simple crank arm. There is a clevis at the end of the valve stem that fits around the top end of the rocker arm and is pinned to it, with threads for adjustment and a lock nut to keep the adjustment from changing in operation.
Whether you can get it to move depends on whether the loco has a solid or open frame. Movement would require cams on an ungeared axle and spring-loaded arms on the inboard ends of the rocker shafts.
The entire gear is rather more complex than Walschaerts valve gear, so modeling it accurately is a job for only the most severely-afflicted rivet counter.
In 1956, in Copenhagen, Denmark, I saw an 0-6-0T with outside Stephenson gear! Unfortunately, my photos from that period are only memories.
Chuck
Thanks Chuck.
The model has a high boiler and there is quite a gap between it and the chassis where some detail could be constructed. However, I think it would be too much trouble and could cause problems when the time comes to re-lubricate the drive worm gear etc. There is what looks like a rocker arm between the first and second drivers where a thin wire could be attached and run to the steam box. This would complete the look of proper valve gear even if it doesn’t move.
By the way, MRs latest information station ‘pdf’ download - “Steam Locomotive details and weathering” is full of very interesting information on a lot of steam engine detail, including various types of valve gear, however it didn’t show the Stephenson gear on an actual locomotive.
Well, it wouldn’t be normally visible on a US loco, since the valve motion is mounted entirely between the frames.
As Chuck notes, the only component you need worry about is the rocker arm and valve rod. I must say, I’d be very surprised to see a US loco with power reverse and Stephenson valve gear…are you sure this model isn’t the normal Spectrum loco with some bits missing? All of mine have Baker valve motion.
Cheers,
Mark.
Are you sure it’s a Bachmann Spectrum 2-8-0 (HO) with Stephenson valve gear?? They don’t show anything like that on their website. Their 2-8-0’s have Walschaert (or Baker??) valve gear. If it has Stephenson, it would have only a mainrod and siderod, no “monkey motion” third rod.
The only model I ever saw up close that had working Stephenson was the ‘semi-scale’ Lionel 0-6-0 c.1940. It looked neat on an O scale model, but I doubt you could really see it in HO or smaller.
Stephenson valve gear on a 2-8-0 would look something like this:
http://www.bcarchives.gov.bc.ca/cgi-bin/www2i/.visual/img_med/dir_100/a_08654.gif
…and not like this:
Mark, you are right. The model obviously had Baker valve gear, as do all the other models in this range and some of the links have been removed in a cheap and nasty way to try to depict Stephenson gear.
Once again a steam engine has not come up to my expectations! I have had very little trouble with my diesels, but steam is a whole different can of worms.
Stix, it is a Bachmann Spectrum 2-8-0 Union Pacific with Vanderbilt tender. If you look carefully at the very small image on Bachmann’s on line catalogue you will see what they have done.
As a youngster I remember seeing “Harriman” style 2-8-0s at work on the SP. They were unique in that they combined Stephenson gear with spool type valves. Probably this was the last large scale application of Stephenson gear in American railroading. Unlike other types of outside gear, there was not much to see. Just a small rocker arm and a rod going back and forth. Gave the engine a sort of naked look and there was a lot of air space between the frame and the boiler as well. At speed the connecting rods flapped around with nothing to block your view of them, kind of like immature chicken wings. If your Spectrum engine duplicates this aspect that’s about all you could ask for!
Jimvalle, thanks for the interesting anecdote.
The model is, in most respects, very good. Separate molded pipework, injectors etc. It can pull a reasonably long train as well.
I am going to remove the wrong links on both sides and add a couple of pieces of fine wire from the valve box back to the rocker shown in back of the large casting that protects the driving rods (I don’t know what this is called, but I notice most steam engines have them) and then it should be pretty close to what it should look like I think. I have an IHC 2-6-0 Mogul which obviously has Stephenson gear as well. If I can make the Consolidations valve gear look like that, it will be near enough won’t it?
Cheers
Bill
(MRs latest pdf download “Steam locomotive details and weathering” has taught me a hell of a lot more than I ever knew before about steam engine bits and pieces, I recommend it).
As a live steamer. I have seen working stevension valve gear on engines. I owned at one time a 3/4" 4-4-0 that had inside Walschaert valve gear. So there is no hard rule that a inside valve gear has to be type x. The difference is that stevension valve gear used 4 eccentrics. Two for each side, one was a froward and one was reverse. What made my 3/4 engine different is there were only 2 eccentrics on the main axle.
Also that structure that protects tha gear is the crosshead guide support. It supported and streighted the outer ends of the main crosshead guides when there were 2.
Randy
Unique to the SP, perhaps, but I can think of numerous locomotives in the US and elsewhere that had piston valves and Stephenson or other inside valve gear.
All the best,
Mark.
(Rivet Counter & Pot-stirrer)
No, there isn’t. But in the context of this thread, can you think of any prototype US steam loco with Allan or Joy gear?[:)]
All the best,
Mark.
(Rivet Counter & Pot-stirrer)
The Spectrum 2-8-0, Union Pacific 618 is suposed to have Stephenson Valve Gear. This unit currently is in steam on the Heber Valley Railroad in Heber, Utah.
If you can get a hold of the May 1998 issue of Railfan & Railroad, they have the 618 on the cover and some good photos of it inside (pg 35-40.).
When I detailed mine, I cut every thing off the the large hanger that holds the guide for the piston in the large steam cylinder, then you add a brass rod from the top of the hanger (i can’t think of the right word.) to a hole you drill in the center of top smaller steam cylinder.
It depends on haw detailed you want to go with it.
I removed the steps leading to the pilot, and replaced them with brass rod using the holes in the smoke box and drilled new ones in the top of the pilot.
There are some other details too.
send me an email. I can send a couple of photos.
lizzard_45@yahoo.com
Paul H. Liddiard
Spool type valves were required if the engine was superheated, regardless of the valve gear type.
Jack Johnson