About Sean

I am a committee member and an engineering beginner . My day job is a computer programmer.

Polly Progress

Progess has been slow due to other commitments but now I’m hitting the workshop in ernest.

The base, firebox and baseweight are assembled.



The engine standard has been curved to fit the firebox, axle bushes turned and soft soldered to the bottom of the standard and the portface has been drilled/milled and riveted and soft soldered to the top of the standard.

Last night I turned the crank and crank pin, I just need to tap it 5BA now (guess what the one tap I’m missing is? Grrrrrr)

Workshop Wishlist

I’ve added a post to the Members Section Forum where you can suggest items of machinery or tooling for the new workshop, If there is specific item you want to have access to there, add a reply to the post.


I’m hoping for one of these………

Polly Boiler – can it take the pressure?

Pickle saved the day! Following my misshap with the steel washer in the old pickle (see comment on previous post) a further week in fresh pickle reversed the copper deposition.

Also the silver solder finally flowed. The improvement was down to using more flux and using a bigger burner to get the temperature up quicker.

The finished job may look a little messy to the more experienced practitioners out there, but to me it looks lovely as it’s my first sucessful boiler build 🙂


Now I like to say it held pressure on its first test, but that would be a fib. Two of the bushes leaked when I tested it initially at 10 psi immersed in a bucket of water. The answer? MORE SOLDER.

It has now been tested to 30 psi and not so much as a nano bubble escaped – phew

Polly Brazing

What did I say about luck and a fair wind?

The solder around the base ran as expected. Dead easy this soldering! I don’t know what people go on about.

So on with the base of the chimney. Heat up, watch the flux melt and go clear touch the solder on……. nothing. More heat then…. nothing MORE HEAT……. still nothing HEAT HEAT HEAT HEAT and yes – still nothing. Out of luck. Dang it!

It all went into the pickle to try again the next day (well today). This time the base went on fine.

Dead easy this soldering, I dont know what people go on about.

So turn it over and lets do the top. I just about managed to get the top of the chimney done and one of the bushes. The other two bushes and the rim of the top, Nope. Nothing doing. Rien de rien.

The /^&/$@#/ thing is back in the pickle now ready to try again tomorrow.

Sean Griffiths

Tubal Cain’s Polly

I am taking part in the SMEE course for beginner Model Engineers, the course covers the building of a small boiler and oscillating engine to the design ‘Polly’ by Tubal Cain.

The boiler is designed around a tube of copper with formed endplates and a central chimney that doubles as a stay. Brass bushes are placed in the top plate to hold a safety valve, steam pipe and filling point.

Here is my progress so far.


Cutting the end plates from sheet


Discs held on an mdf base for drilling the central hole


I had heard lots of horror stories about drilling sheet but using these drills it was no problem. Not a triangular hole in sight.


Here you can see a part formed disc and the next one to be formed fitted to the former. The ball pien hammer was an old abused one that I cleaned up with emery and then polished up on a buffing wheel bought at one of our auctions.


And then it a case of beat, anneal, clean…… until formed.


All the copper parts complete. The holes for the bushes were drilled using the drills shown previously and the holes for the chimney were opened out with a boring bar on the lathe.


And here are the bushes turned from brass.

My next step is to silver braze everything together. I got a few sticks from Ron at the last meeting and the only thing holding me back now is a little trepidation but with luck and a fair wind it will be done tomorrow.

Sean Griffiths

Open Day at Ashton Court Miniature Railway

Sunday, September 2nd 2012

From 11.00am until 5.00pm

A relaxed and friendly day with no public passenger carrying.

Bring a locomotive to run – steam loco’s require a current boiler certificate please.

31/2″, 5″ and 71/4″ gauge tracks in operation.

And an added bonus! Bernard will be demonstrating Silver Soldering in the Ashton Workshop. Come along and watch an award winning engine builder at work