Keith Parkinson's Class "A" Climax


Having built several locos with conventional boilers, cylinders and valve gear, I wanted something substantially different, so my thoughts turned to the Class “A” Climax.

              A search of the internet revealed an article by Bert Horner from Austria, of a model he had built, with several good photos and a good write up. This loco had a vertical boiler, onboard steam engine with central gear drive to 2 power bogies, via prop shaft and flexible couplings, an oil tank was used as gas tank, and a round water tank used to collect condensate.  


I decided this would be the basis for my next loco. I understand only two full size locos have survived, one in Alaska and one in New Zealand, both in very poor condition.             

I decided to start with the bodywork; this gives me encouragement to do the more tedious parts.

This went together quite easily which is more than I can say for the gear drive on the bogies, but I got there in the end.

I am hoping to start on the steam engine next, which will be a double acting twin oscillating cylinder type.

The photos show the progress on my loco at the end of January 2015.

February 2015


I decided to fit the gas tank next, which was purchased from Maccsteam Ltd.

It presented problems because I had to leave access to the bogie fixings. In the end I combined some fixings from both, meaning that the gas tank has to be removed before the bogie can be removed. Hopefully this will not happen often. The gas tank needs disguising to make it more like an oil tank, but I have not decided how as yet.

 I would like to move the gas valve lower down, but it would properly invalidate the pressure test certificate.

Moving on to the steam engine, when I looked at the drawing I had prepared I thought it would be an easy item to build with no fiddly bits, then I remembered the drawing was twice full size. It has a bore of 0.375” and a stroke of 0.472” (12mm).              

The engine under construction

The engine, gas tank & boiler mounting plate on the chassis.


The underside view with the drive train from the engine to all the axles, via universal joints and propshafts; this has a 5 to 1 reduction.

May 2015 Update


The steam engine was finished and the boiler built.

The finished boiler.

After fitting the lubricator and various boiler fittings I was ready for a test run. With the loco on blocks in the workshop I lit the burner and waited for the pressure to build up, which took a long time. When 40psi was reached I opened the regulator, the engine ran for a few seconds, splashing steam and water all over and draining all the steam pressure.

Several attempts were made to improve matters by lapping the port faces on the engine, and adjusting the gas/air settings and changing gas jets, with little effect.

As there appeared to be a lot of heat produced by the burner, but not transferred to the water it was decided to build a new boiler with cross tubes in the centre flue. This proved a disaster as when the boiler was tested it was found one of the cross tubes was leaking. As this was inaccessible the boiler was scrap!

After advice from various friends I persisted with the first boiler. I had a certain amount of success, eventually getting it to run about 80/100ft, level and downhill before running out of steam.

The loco as running on test.

I decided the current arrangement would never be satisfactory. As Class “A” Climax locos had various types of boilers, I decided to fit a conventional horizontal type, which would not have the same height restriction.

I also ordered a kit to build a marine type vertical steam engine from America which appears to be the one other builders have used.

While waiting for the kit and some boiler material, I am currently modifying the bodywork to allow the new boiler to be fitted.

July 2015


The bodywork alterations involved removing the vertical boiler mounting plate, moving the cab, repairs to cab roof and decking, and modifications to the steam engine well. The gas tank was exchanged with the one in my Meyer loco.

The new engine kit arrived, it was well engineered, but a bit fiddly to put together with screws as small as 12BA. It has so far only run on air.

The boiler material arrived; it was built and tested to 90psi. It had to be made ¾” shorter than I would have liked to allow clearance from the engine. Flexible pipes were used to prevent any movement on the boiler putting strain on the engine.(and it was easier).

The steam engine and boiler were installed together with any components needed to run the loco, but I decided to wait until the woodwork was varnished to prevent damage if water or steam got to it.

My next job is to dismantle the loco for painting and varnishing. The dome and wood burning stack will probably be left until after the first run.


September 2015 (final report)


After painting and varnishing, the loco was re-assembled ready for testing. Several short runs were required to adjust the regulator and burner gas/air setting. I had a problem with the gas tank cooling; this was rectified by diverting the exhaust steam via the gas tank.

The loco was run light engine for a while then allowed to cool before re-watering, gassing and oiling.

After a few similar runs 3 trucks were attached and a further 3 which it handled well.

Click here for video of finished loco running on the Foxhill Light Railway.

I am not planning any further work on the loco but more detail may be added later.


































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