Part 2 by Werner Jeggli

Part one here.

The idea that all that was left to do was ‘cosmetic’ proved to be quite cheeky (to my sorrow). For the benefit of anybody intending to undertake a similar project, I list the main problems I encountered below (there are no problems – there are only tasks - ha! ha!).

  1. I broke two turbine rotor-end ball bearings (2x2.5x6mm, hybrid, shielded) despite carefully balancing the rotor and having good experiences with the previous locos. Rotor width, however, had increased from 3mm to 4mm, therefore also its mass. Remedy: install the next larger ball bearing (3x2.5x7mm, hybrid, not shielded - so as to retain the same thickness). The gear end bearing was left at 2x2.5x6mm shielded.

  2. Turbine rotor shaft and angle gear shaft became slightly bent. They were made of low grade stainless steel. Reason again was the much bigger mass of this American engine and, therefore, increased strain on the gear train. New shafts were provided with higher quality VA2  stainless steel.

  3. I had drawn on my stock of M0.5 spur gears, professionally hardened (carbon-nitrided to depth of 0.2mm). Now, I had to replace the turbine shaft’s 10 teeth spur gear with a new one. No problem, I thought. But the hardening shop known to me had disappeared and a new one elsewhere, who reluctantly accepted my request for a small fee, did not succeed.

I tried nickel plating the gear, then milling it out of a 6mm silver steel rod and hardening it by dipping into an oil bath - all to no avail. At 35,000rpm, the wheels were chewed up within minutes while the other gear wheels down the line showed no signs of deterioration.

I was close to despair. Relief came with the advice of Heiri  Schartner, also a G1MRA member, to try a method his father had already used. Sprinkle ‘Berconit’ hardening powder on the wheel while red hot within the heating flame, dip it in cold water, brush off the residue and repeat it 3 or 4 times. It worked excellently.

Steaming capacity is lower than it was before the body work was put on. The burners do not seem to like restricted air intake. Next time the compulsory domestic central heating boiler check is made I’ll ask the inspector to also analyse the PRR S2 exhaust with his equipment.

Two years ago, combustion and readings were OK! What I really need is expert advice on burner configuration and on how to achieve a higher heat input.

Engine internals were described in the previous article. Now let’s have a closer look at the  tender.

It holds a 0.3 litre tank of liquid gas, sufficient for a 45 minute run. A 3-way valve permits selection of gas take-off either from the top for getting the boiler up to temperature (at the expense of cooling down the gas tank and thus lowering the gas pressure) or from the bottom in liquid form during the run.

Gas evaporation then takes place in a pipe loop attached to the hot boiler. Gas tank pressure then is maintained.

Besides the fuel, what does a steam loco also need? Water, of course! The tender carries along up to 1 litre of back-up b o i l er water in three compartments. The boiler level is detected by an electronic Alan Coombe level detector (Ref. 1 ) which, when required, tells the electrically powered feed pump to get going.

Then, there is the remote control receiver, a Peter Spoerer product (Ref. 2 ), small and reliable, which operates the forward and reverse steam jets via a single knob. This means, that you can brake the engine by simply turning the knob, applying counter-steam.

All these auxiliaries require auxiliary power. Five A size 1.5V cells for the feed pump and three AA size ones for remote control.

The available tender space, therefore, is fairly much occupied –  as you can imagine.

The PRR S2 is a large engine and requires adequate track radii. It is designed for a minimum of three metres. The EIWI track at Witterswil (near Basel, Switzerland) exceeds this value by quite a bit.

the model is finished and performing quite satisfactorily. This you can see for yourself in the latest of several of my videos by searching YouTube under ‘PRR-S2, Jeggli’.


1. Coombe, A. Automatic boiler level control . G1MRA News Letter , Sumer 2003 ( http:// )

  1. 2.

These articles first appeared in the SMEE Journal.