Roundhouse Billy problem - too much steam?

[Paul M]

The only thing I haven't tried is replacing the regulator

As previously suggestions, it does seem like a regulator problem, have you taken it out to check there's nothing stopping it from fully closing?

 

[Charles M]

A Billy should run very nicely on 20 lbs. of pressure. I have a Roundhouse Katie converted to resemble a Hunslet " Jack ". I had obtained a conversion throttle to the needle valve type when I did the rebuild of my model. The R/C type throttle on a manual locomotive is virtually uncontrollable. My model has had R/C restored to the throttle only and I still use the needle valve throttle with good results. The throttle must not be closing completely to have a runaway all of the time.

 

[Jasper]

I've drilled a 1.6 mm hole in the centre of each of the cylinder front plates.

I'm curious: who made this suggestion?

 

[Rhos Helyg Loco Works]

Fascinated to know the final outcome of this ... will we ever know?