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:
CYou 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...
Cheers
Flymo
Whin I built mine (http://philsworkbench.blogspot.co.uk/search/label/mineral%20engine) I just put the cast pin through the connecting rod. I don't recall any problems - but then it was a long time ago.
ReplyDeleteYour photo would seem to suggest something has changed. Personally, I'd find someone with a tiny pillar drill and replace that pin with a brass dressmaking one. You'll struggle to go trhough without power, hence the pillar drill.
Hi Phil,
ReplyDeleteThanks very much for the confirmation of how it should work. If you have a quick look at my very next post, you'll see both the issue and the fact that it can be easily solved.
I do have a very good pillar drill - a Proxxon 220 - which I bough a year or so ago when I saw at a Missenden Modellers' Weekend just how easy they made tasks. Thankfully, in this case it won't be needed.