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Query on Ajax locomotive and steaming ability

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Greg H04/02/2017 23:56:54
47 forum posts


I was thinking of building an Ajax as my next locomotive, just thinking at this point in time, but I have got a set of plans to peruse over. I had picked it because I was after a small 5' loco that was quite simple in design and build.>>

I had heard they run well, but only from on the internet. I don't know anyone with one. I wondered about its steaming ability because of comments I’ve seen about the Simplex not being great at keeping steam up and how the two compared in specs.>>

For Ajax the bores are 1.375" with a 2.5" stroke.. The swept volume is 1.86 inch3. >>

For the Simplex the bores are 1.5”" with a 2.125" stroke. So larger bore, shorter stroke. The swept volume is greater at 1.99 inch3, but only by 7%. and it has a bigger boiler.>>

Wheels are the same diameter for each at 4.375” .>>

As far as the running load goes it would only be pulling one person most of the time, and maybe two sometimes .>>

I also wondered about the longer stroke and the benefits of it >>

What are peoples thoughts on the Ajax does it run ok? I had seen some suggestions on another post about it being a simple loco to build, but not much more.>>


julian atkins05/02/2017 22:07:33
1240 forum posts
353 photos

Hi Greg,

I think I can speak with some authority having driven and maintained the IWMES club's enlarged AJAX for some 15 years.

The only enlargement was the addition of a bogie under an enlarged bunker for water and coal.

The boiler is good. It is an old Reeves design so isnt quite up to modern spec. The Achilles more recent version is better and worth considering.

There are issues with the valve gear as the return crank provides too much movement leading to overrun on the valves in fullgear.

I think you really ought to opt for a much more up to date design as AJAX dates back to the 1950s. It is very rarely built these days.



Greg H06/02/2017 11:49:58
47 forum posts

Hi Julian,

Sounds like you've spent a bit of time with one. If your club had one for 15 years then it sounds like a runner, unless it spent most of ts time in the shed.

One reason I picked it was because it had a parallel round top boiler which I thought would be nice and simple.

Thanks for the heads up on the valve motion. I might model it and see how it looks.

Sounds like you don't favour it the Ajax What's wrong with it being an older design? Is it that the valve motion is not spot on, or something else?

I was also thinking of a Railmotor, but found the Ajax and quite liked it. The wheels are larger in diameter at 4 3/8" compared to the Railmotor's 3 1/2" which I thought was a good thing as it won't need to pull a big load.


Edited By Greg H on 06/02/2017 12:05:34

EdH06/02/2017 20:44:49
45 forum posts
27 photos

Hi Greg,

I'm not sure if there is more than one loco design called Ajax but the one on the AJ Reeves site has a bore of 1.625" and a stroke of 2.250" so larger then the dimensions you provided.

Durhambuilder06/02/2017 21:27:57
69 forum posts
5 photos

I built one as a first loco, absolutely fantastic on the track with six up, everybody in the club comments on how well it goes. Boiler is more than capable of supplying the 1 5/8 cylinders, a lot of the time I have to run with the fire door open, perhaps I need to look at the blast pipe to reduce the draught a little. The only change I made was to the boiler, this was made with a single flat sheet of copper for the boiler barrel and wrapper, the barrel being joined by a cover strap on the outside underneath.. A few photos of the soldering are in my album. With hindsight I would't bother with the aluminium smokebox casting, try and fabricate one out of steel or brass. Paint won't stick to the aluminium and it appears to seep oil almost as if it were very slightly porous.

Greg H07/02/2017 06:52:03
47 forum posts

Hi Ed,

No only one Ajax, I just stuffed up on the dimensions. The drawings are smaller than 1:1 scale and that 5 in 5/8" looked like a 3. I squinted a bit and saw it was a 5. No excuse for the wrong measurement. for the stroke. The crank pin is 1 1/8" so 2.1/4" stroke.

I now know why last night when I was modelling the valve motion in the simulator the piston kept popping out the ends of the cylinder by about an 1/8 of an inch. blush

Hi Durham, you've given me some comfort. Thanks. I thought I would fabricate the smokebox, but it was only because I thought at £137 it was a lot for the casting, especially with postage to Aus added on.

Brian Baker 107/02/2017 08:05:28
167 forum posts
34 photos


I suggest that you never use an aluminium smokebox.

when wet, it starts reacting with the copper of the boiler, with which it is contact and starts electolytic corrosion with it, and possibly removing the silver from the boiler joints.

I suggest brass, copper or even steel rather than aluminium.

I have built Hercules, as a 0-6-0, which comes from the same family & it performs well.



Peter Layfield07/02/2017 08:52:04
36 forum posts

Hi Greg, everybody may have an engine design that would meet your criteria, my pennyworth

is the Y4 which is a brilliant design and many are running with remarkable success, has been updated over the years

and is currently being described in easy to follow steps in EIM. I could list 6 that are in constant use and produce

ample power and adhesion for anything you would want todo


Greg H07/02/2017 12:06:00
47 forum posts

Thanks for the info Brian. I hadn't realised Aluminium would create problems like that.

Hi Peter, yes there are many designs that would suit and often it just comes down to what you like the look of.I was aware of the Y4 and I'm sure it would be a good engine, but the looks don't grab me. It's certainly an industrial looking engine. The parts for it looked reasonable for price.

I wasn't planning on doing a scale loco just something that looked well proportioned..One of the reasons I had picked the Ajax was that the boiler was round top and parallel and so a bit simpler than some others.

Baz07/02/2017 12:42:57
575 forum posts
2 photos

I believe the Polly range of locos have aluminium smoke boxes and they seem to be alright, also all the ones I have seen don't seem to have problems with their paint adhering.

MW07/02/2017 13:12:51
2051 forum posts
51 photos
Posted by Baz on 07/02/2017 12:42:57:

I believe the Polly range of locos have aluminium smoke boxes and they seem to be alright, also all the ones I have seen don't seem to have problems with their paint adhering.

I think what they might be referring to is the same problem old landrover's normally had with their aluminium shell, the paint peels away around the steel joins due to electrolytic reaction with the metal.

Michael W

Bob Youldon07/02/2017 14:53:50
183 forum posts
20 photos

Good afternoon Greg,

i have never built one but I know of a few and they all went well, and did all what the builders expected of them. We had one for years at Beechhurst built by the late Dick Burge, it went like a rocket, Dick always had a water tank on the passenger car as it only had injectors, he'd filled the tanks with lead shot! it would always shift four cars fully loaded and keep doing it all the afternoon. Not much wrong with that design. Not a thing of beauty but very capable.



Greg H08/02/2017 06:44:45
47 forum posts

Good afternoon Bob,

Sounds good for me. It'll only be pull me and so no lead bricks required.

It's the best looking loco that met my criteria and I think not bad for a simple 040. Beauty is in the eye of the beholderwink

Ray Wood 303/03/2017 17:09:10
6 forum posts
3 photos

Hi Greg

I have an Ajax built by my uncle around 1970 it did good service back then its on its second boiler in 1993 now and extended into a 0-6-0 with a Railmotor tender. It was designed by Dick Simmonds from Erith and built and bits supplied by Fred Stone, long gone now but a popular design, simple workhorse, the Welling & District MES still have one for a club loco, the only critism of the boiler was its relatively deep fire box and can clinker up, but a good rake now and then stops that ! We still steam for the grandchildrens rides in the garden. In my view a good choice to build.

Regards Ray

julian atkins03/03/2017 22:39:17
1240 forum posts
353 photos

Hi Ray,

Upon what basis do you suggest a deep firebox is prone to 'clinkering'?

Clinkering is a simple result of a number of factors including either poor coal and too hot a firebed due to too fierce a draught on the fire.

A deep firebox per se is not the cause. A deep level firebox creates the best form of firebed.

Run the Ajax valve gear on a computer simulator and see how it compares with better more modern designs.

If I were to build one (which I wont) I would use the much better balanced Achilles 0-6-0T arrangement, re-design the valve gear, and reduce the huge cylinder bore. I would also re-design the smokebox draughting.

Achilles is very similar to a fullsize loco called Ajax on the IOWSR.



Greg H04/03/2017 20:51:10
47 forum posts

Thanks for the feedback Ray.


If I am to build one it may well get a smaller cylinder bore. The cylinder bore does appear to be quite large and not required for my purpose. If I also go with a 1/16" shorter stroke i.e. 1 1/16" then I think I can use Simplex wheels and cylinders. I can get these castings in Aus which would make it quite a bit cheaper for me.

So the valve motion would get a bit of redesign


Ray Wood 309/03/2017 12:09:27
6 forum posts
3 photos

Hi Greg

This is the Ajax my uncle built in 1970, he then extended the frames plus an extra pair of drivers to create 0-6-0 and re-named the loco Hector to keep the theme. As you can see us happily steaming in the garden couple of other shots in the album. Regards Rayhector & kids oct 16 008.jpg

Greg H10/03/2017 21:45:56
47 forum posts

Hi Ray, that is different to what I was expecting. One thing about a free lance design is you can do it however you like.

It must be nice to have a bit of track in the backyard.


Stephen Wessel 109/04/2020 18:11:15
8 forum posts
13 photos

Hi Greg

Just seen this thread 3 years later! I wonder if you ever built your Ajax. I made mine in about 1968 as a first loco and it has given wonderful service, although in recent years rather pushed aside by bigger machines and a much longer railway.

I agree with all the commentators, including the fact that the bore is too big. I don't know about the valve gear - seems fine to me, notching up evenly in both directions. Looking at it now I would say it is not a beautiful engine but a dockyard work horse. Mine has a few leaking stays now and needs restoration including a repaint. Trouble is, it keeps going to the back of the queue!

Back in the 1960s I was a student in London and used to walk past a shop called 'Steam Age'. Knowing nothing about ME and having very little money, one day I plucked up courage to go in. I must have shown some interest in building something as the proprietor took me over to this little 5" tank and said: "here is the one for you - easy to build and get your bits from Fred Stone". A life changing moment although I never knew it at the time. Eventually I got a tiny workshop, made the engine then lost all interest for about 20 years. But it finally emerged from storage and gave pleasure for many years.

I hope whatever you decided on has gone well for you.

Stephen Wessel

Dave Wootton09/04/2020 19:04:01
200 forum posts
51 photos

I used to belong to a club which had two members who had built Ajax locos. One was named Ajax the other unnamed, one day the owner of the unnamed one returned to his locomotive to find neatly made nameplates stuck on it - Vim!

Perhaps you need to be of a certain age to get this.

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