Monday 29 October 2012

Coffeepot - the solution

Having been stumped in my previous post, I asked the question on the Scalefour Society Forum.  Almost immediately I received a couple of very helpful replies:

Will L wrote:
It just worked for me. I have this feeling that despite what you said, you haven't followed the instructions... yet. The bit about filing down the back of the cross head in the filing guide provided. Could be that the pin will be a lot thinner when you've filed the cross head down to the correct thickness.

davknigh wrote:
What Will said. My Neilson had no problems either. Have you had a look at the crosshead from the end to see if the pin is a bit mushroomed? Filing down could be the cure, failing that I'm sure Chris could furnish another casting if you asked nicely ;)

Well, no matter what Will (or my manager at work) may think about my ability to follow instructions, I had indeed been following the instructions... Not that it is a chore, with instructions of the quality of Chris's.

I had put both of the crossheads into the filing jig to reduce the depth of them. This is yet another bit of clever High Level design, and you file the thickness of the casting down until it is that same as the slidebars...
crosshead jig 002.jpg

However it does indeed appear that I have not quite filed down far enough. When I looked end-on to the casting, as suggested, this is what I saw:
Mushroom 001.jpg
That is literally 0.1mm of metal remaining as a "cap" that made the pin look much thicker than it actually is.

So the instructions are correct, I can carry on, and the Scalefour Society Forum once again proves its value! Thank you gentlemen...


Friday 26 October 2012

Stumped by a Coffeepot...

For the first time since starting the build of the Coffeepot, I've hit a genuine, can't-see-how-this-works, problem that re-reading the instructions won't solve...

The crossheads are two very nice lost-wax brass castings. After cleaning them up, and straightening the piston rods, they are united with the connecting rods by passing a pin in the back of the crosshead through a hole in the end of the connecting rod, and then soldering a backing plate, well, on the back.

However, this is a picture showing the pin and the hole:

Crosshead 004.jpgC

You will see that the hole in the connecting rod is far too small for the pin. Indeed the pin is almost as wide as the rod-end itself... By way of scale, the total length of the crosshead is 14mm, so I don't have a great deal of metal and room to play about with.

My initial thought is to grind out (as I can't get a file on it) the pin at the back of the crosshead. Then I will drill a (say) 0.4mm hole through it, and use a brass lacemaker's pin to make a new pivot point.

Before I get out the heavy engineering tackle, is there anyone here that has either:

(a) built one of these Coffeepots or a similar Neilson and got this arrangement to work as designed, or
(b) can tell me that I've missed something blindingly obvious, or
(c) can suggest an alternative solution?

This isn't a deal-breaker by any means. The parts are all still beautifully formed, and this is the first difficulty I think that I have had and it's nearly at the end of my second tiny High Level locomotive. Knowing how good Chris Gibbon's instructions are, I do still wonder if I've missed something somewhere. Anyway, as he's now a Scalefour Society member, perhaps he can chip in on the Society's Web Forum and tell me where I've gone wrong...

Oh, and when I have it all sorted out, I've already made the clothes peg clamp to hold it all together to be soldered...
Crosshead 005.jpg


Thursday 25 October 2012

Return from Missenden Abbey

It's been a couple of weeks of being back at home and work after a wonderful weekend away modelling in the beautiful surroundings of Missenden Abbey. And the food wasn't half bad this year as well...

I didn't feel that I did as much modelling over the course of this Autumn weekend as I did in my last couple of visits on the Spring weekends. This was mostly due to a large amount of socialising with the other course participants! However the enthusiasm for modelling remains. I have had a good sort out (tidy up!) of my workbench on my return, and tonight I settled down for some heavy duty metal bashing.

I had taken a number of projects along to Missenden, but mostly worked on my Coffeepot. I had stopped working on it at home, in the evenings, as I knew that the next task to be done was to make up the two sets of brake rigging, and I didn't the three or four hours of time to sit down solidly and knock this off in one session. However Missenden is perfect for this sort of task and I soon had it cracked out. That was followed by miscellaneous fittings, and the slide-bars and cylinders.

This was the point at which work at Missenden ground to a halt, as I knew that I would need my little vice and an assortment of bars to roll the forms of the cylinder covers. These are both small and a tricky reverse curve. However I cracked on, and this is the result:
Missenden Oct 12 004.jpg

Missenden Oct 12 005.jpg 
There has already been some tidying up of the soldering (I was in a splodge-it-on strategy, to get them firmly in the correct places without moving) , and tomorrow night will bring the cylinder end covers into place...