New Parts for an Old Locomotive

[Gra2472]

A couple of years ago I purchased an Allen Mogul that was built by Ed Adams of Golden Gate Live Steamers. I remembered this locomotive running around the track back in the 1980s when I was a kid. I was glad to have the opportunity to buy a locomotive, and delighted to buy this one.

I did not know Ed, but I had met him once or twice over the years, and I had heard many good things about his work. So far, I have been impressed with this locomotive and his machine work. This one was completed in 1973, and while it has a few miles on it but it is in pretty good shape all around. However, this locomotive did suffer from a problem that I found out plagued many early Allen locomotives, issues with the rocker arms and boxes.

That being said, I have been working on replacing the bronze rocker boxes, and arms. The originals were so badly egged out that the arms were actually loose on the shafts, and there was so much lost motion in both assemblies that the valves were hardly moving at all. As a side note, the locomotive ran, though poorly, when I bought it, so I knew I had some work to.

At first I tried making a few repairs to get me though a season or two. I tried new pins, and even cut a slot in the bottom of the rocker arms to try take up the slack with bolts to clamp everything down tight. Much in the same manner in which an eccentric crank is clamped to the main driver pin in walschaerts or similar designs. This did work for a while but the bronze rocker arms, and the badly egged out holes in the shafts still left much to be desired. It ran, but enough to limp it home if you will. During this process, I found that the outer rocker arms were actually contacting the frame spreader! Now it started to come into focus about what was going on. They were not parallel to each other, and I figured that they might have been assembled about 15 degrees off, which allowed the other rocker arms to hit the spreader and cause everything to work lose.

So, this past winter I bit the bullet and got started on the replacement project. Now, let me be out front with this. I am not by any means a machinist. I just act like one when someone is watching! I have been in and around machine shops for years, and have a little bit of training but I am 90% self taught. Over the past couple of years I have been working on converting a Grizzly G0704 to cnc, which thankfully I completed just in time. I am running Mach3 and using BobCad/Cam for the drawings and post processing. To say the least, I am learning as I go, and I have had some really great help, and the robotics, drafting, and autocad classes I took in college are really coming in handy

On with the new parts!

I designed a new rocker box based on the original drawings. All of the major dimensions are true to the plans, but I increased the size of rocker assembly to include roller bearings, and larger diameter shafts. The rocker boxes and shafts are made of out of 304 stainless, and arms are out of mild steel. Why? Well because I could I guess. The rocker arms and shafts were first machined to a .002 interference fit, but after the first attempt at assembly, I found that I could not press the tiny bearings onto the shafts as I had hoped. They kind of exploded like popcorn when I tried it. So, after some careful consideration, I just chucked the shafts in my mill, and sanded them down to fit with sand paper. Sanding them down to a close fit worked like a charm, and now they have a bright polish! Man they can get hot!

With the larger diameter to accommodate the roller bearings, the outer edge of shaft way portion has be relieved to clear the flange on the lead drivers. Since I have not yet graduated to 4th axis machining I found that grinding this relief by hand was the best solution for my needs. I could fit, grind, fit, grind, and so on to get it right with as little trouble as possible.

Anyways, I have completed this project, and installed them on my locomotive. I am currently resetting the timing, and glory be! Things are starting to line up properly! I made two sets in the hopes of buying a ten-wheeler in the future but the Mrs. is offering resistance to my plans.

Here are a few photos.
1. The parts laid out before assembly
2. Close up of the firemans side assembly
3. Both installed
4. Plans checker looking things over.

converted-Rockers installed 1.jpg (8.75 KiB) Viewed 5287 times

converted-Rocker installed 3.jpg (8 KiB) Viewed 5287 times

converted-Plans inspector.jpg (5.53 KiB) Viewed 5287 times

[Gra2472]

A couple more photos and a video.
https://youtu.be/TII-b7Hy62I

[Greg_Lewis]

Thanks for posting this. Most interesting. As to the shafts and the interference fit, what I do for things of that size is to use Loctite. While this will get condemnation from some folks on this board, when used properly it's a perfectly acceptable solution. Machining such small diameter parts to the required dimensions for press fits is often too difficult with the equipment we have to work with. Loctite has a bearing seating compound that works well when directions are followed.

Hope to see more pix as you progress.

[NP317]

How are the rocker arms secured to the shafts?
I am contemplating a square fit for each.
RussN

[Gra2472]

The arms are secured with .144 roll pins and Loctite.

I put the boiler on the frame this afternoon after timing the locomotive. Before the new parts the engine wouldn’t move. Now it moves easily on as little as 5 psi. Forgive me.. but WOO HOO!!!

[NP317]

Another job well done!

I still need to retime the valves on my Allen Ten Wheeler after rebuilding the valve gear. Excess motion all removed.
I look forward to being able to say "WOO HOO!"
RussN

[VGC]

@RussN Good luck

[Kevin S]

Good Job!!

[Dick_Morris]

How are the rocker arms secured to the shafts?

On the RRSC CP-173 mine were attached with roll pins and that was a weak link. It's be 30 years ago, but my recollection is that a friend's Allen Mogul used the same and he had problems with them shearing.

[Gra2472]

I've uploaded a couple of videos of todays test runs. Everything ran great! Yes I know that I need to lap the safeties. Surprisingly, it is a little out of square in forward, but almost perfect in reverse. Huh.......maybe it wants to be a cab forward? I made about a dozen trips around my little railroad, and even picked up a cut of empty flat cars just for fun. My little railroad is anything but flat which makes it interesting and challenging.

I still need to diagnose the cycling of the engineer side injector. I think its is a bad check valve. Next will be plumbing in the rebuilt air pump, install the main reservoir tanks, plumb up the brakes, and wire up the electrical system for the cab and headlights.

To those of you who have offered their help and advise, thank you very much for all of your help.

https://youtu.be/44CLOxcLaDM
https://youtu.be/zrl84ZtxRrU

[Marty_Knox]

I suggest you replace the roll pins with taper pins.

[Gra2472]

I’m not doubting your suggestion Marty, you clearly have more knowledge than I do on this subject but what’s the problem with roll pins? They seem to hold everything tight and in place. What is the advantage of taper pins? I used roll pins because I happened to have a few on hand from another project and they seemed at the time to be a good choice.