Rob Roy boiler advice requested

The words and music for Rob Roy suggest that the top fitting for the the water gauge should be screwed to the boiler shell and caulked with soft solder.

This method, I'm sure, does not meet current best practise. I'm more inclined to silver solder in a conventional threaded bush and then screw in an elbow to provide the mount for the water gauge - is this a sensible approach?

Cheers,

Rod

Or just a solid block of bronze much like you see on the Minnie boiler amoungst others.

Rod;

I made the bush as per plans, but silver soldered it in place when attaching the boiler backhead to the boiler shell - the boiler is heated to silver soldering temperature in the area anyway. Yes, silver solder all bushes.

You might also want to use copper rivets for firebox stays; placed from inside, but ask your local boiler inspector for his/her opinion.

(my boiler was a large-boiler for Tich, but same kind of design issue)

I built mine to the drawings but silver soldered the bush instead of screwing it. Much better!

Other tips....

Fit the hand pump in the other side tank. There's more room and you don't end up reaching across the safety valves if pumping from the driving trolley. Not so important if you are left handed though!

Feed your steam pipes into the front end of the valve chests rather than the very cramped tee arrangement through the covers. This also makes valve setting and adjusment easier as you don't have to remove the steam pipes to get the coveres off!

Hope this helps!

Also, see the Andover club website for details of their annual Rob Roy Day, May 28th this year!

Rod

The top fitting for my 5" gauge "Gemma" (GER 0-4-0 ST) has the same type of top fitting for the water gauge. What I did was make it out of a block of bronze, held lightly in place by 2 small (#4) bronze screws and silver soldered it on when the backhead was being soldered on. I think far superior than soft soldering it . And probably less work as it is done at the same time as the backhead.

John

Hi Rod,

On my last boiler (5"g Stepney) I had this problem as added 2 water gauges for scale effect. Both required 'elbows' on top of the outer boiler wrapper. Havent had to add an elbow for the top water gauge fitting since my first boiler (5"g Railmotor).

Anyway I agree the top elbow must be silver soldered to the outer wrapper/backhead. The Rob Roy is one of Martin Evans' early designs when he was still finding his feet.

If you are cunning, the top elbow can help secure the backhead to the outer wrapper. This aids the final silversoldering of the backhead, and the above albow at the same time. The same could be said for the turret/fountain.

Make the top elbow as a plain elbow. Thread the bottom of it say 1/4" x 40 tpi ( the passageways through the top of the water gauge do not have to be as big as the bottom of the gauge but not be less than the ID of the glass).

Thread the outer wrapper and perhaps part of the backhead squeezed up tight to match.

Screw in the elbow. Relieve the elbow and copper on the outer wrapper till correct orientation. Rough up the mating surfaces for silver solder penetration. The same can be applied to the bush for the fountain/turret.

Martin Evans' flanges on backhead etc are far less generous than I make mine.

Cheers,

Julian

Here we go...

Cheers,

Julian

Many, many thanks to all who responded. I'll go with the Minnie style option that Julian has kindly shown.

We may have our little disagreements from time to time but this really is a most friendly, helpful and knowledgeable forum.

Rod