Rob Roy

[baggo]

Hi All,

I've just bought a part built Rob Roy chassis and boiler for my brother to play with which should be arriving in the next few days. I've finally converted him and he's decided he wants a loco of his own. Probably doesn't want to be outdone by his younger brother!

I am sure some of you out there will have built Rob Roy or own one and I was wondering if anyone knew of any problems or faults with the basic design? It would be nice to put anything right before we go any further with it. Any comments would be appreciated,

John

[mott]

Hi baggo, try googling Rob Roy. In amongst the Scottish context you will find a paper from the SMEE down in S Wales who list a few design problems.I have a Rob Roy and the crosshead pump is the big problem. Good piston rings are critical - PTFE are good and really getting a better superheater is essential.Water supply is of course critical and an auxiliary tank on the ride on truck is worth considering. Having said all that they are game little engines and can really be made to fly. Mott

[alanstepney]

A few possibly helpful items can be found at:

www.alanstepney.info/page43.html

[baggo]

Hi Mott and Alan,

Thanks for the replies. I've checked out both sources and noted the problems. The chassis is virtually finished so hopefully the valve gear alignment problem will already have been sorted!

The main problem will be with the boiler I think. It's finished except for soldering the stays which were probably destined to be nutted and soft soldered. I'm hoping that we can silver solder them instead but I know that silver soldering the stays inside the firebox may be difficult due to getting enough heat inside the box. I had this problem when I was building the boiler for my Allchin and have yet to sort it . May have to hire a PortaPak and be very careful!

John

[ivanj]

Hi
Thanks for your advice on the built up crank - which is now in hand and following your method.

Rob Roy - The crosshead pump is fine if you make the drive from the crosshead flexible. What I did was to put an oversize hole at the top of the drive link and then the pump shaft is held between two washers which are fitted very slightly loose - the nut is wired. That way the pump shaft takes up its own position but is still free. The problem is the pump moves differently to the crosshead sometimes, this way it can find its own position.

An extended superheater is a good idea but the main problem with this engine is the draughting. I have completely changed the blastpipe and the chimney liner and the result is I have an engine which really goes freely and steams well. If you email me I can send you an article I have written on this problem.

[e-mail]

[Donald G]

Hi, ivanj.

I am interested to know a little more about the draughting of your Rob Roy, I have one, and I have done some work on it, incuding swept inlet and exhaust pipes, which makes it breath quite well, but I am not absoloutely sure the draughting is right, I recently noticed that the blast pipe had been knocked and was not pointing directly up the chimney, which certainly affected the performance, and although I straightened it, I am not overly happy with the performance.

It is soon 'in shed' for new ptfe piston rings, and general chack after about 15 years in service. I am also considering making stainless steel radiant superheaters, as I think after there use, my old ones which is as drawing, is probably worn.

If you would be kind enough to let me have more details of what measurements you are currently usng.

Thanks, Donald

[ivanj]

If you would email me I can send you the article and then you can choose how you set up the front end.

Ivan