Hi Folks
I'm sorry there hasn't been an update recently, I've been rather unwell although thankfully not with this wretched pestilence, but it has kept me away from the bench. I'm better now.
Picking up from 6 weeks ago crankpin bushes were bought and then modified. Firstly mount the bush in a collet in the lathe and then with a 10BA tap in the tailstock rotate at 50rpm and thread them. This sounds scary but in fact worked well, I wouldn't do it in steel but I suspect the major issue is alignment rather than power, anyway no broken tap.
The collet is then transferred to a collet block held in a vice on the mill, this allows easy 180 deg rotation to cut two flats. A 10BA steel screw is used as a mandrel, it seemed to resist sideways pressure.
Then it's all transferred to the lathe to skim the length
This is done using a bit of brass rod threaded 10BA as a sacrificial mandrel and a 1.5mm drill shank to estimate the finished length that I wanted to be around 1.6mm. Out of 8 tries I got 6 usable ones. Bushes and other bits in hand it was re-assembled and surprisingly for me worked first time. It still runs better in reverse than forward, a slight growlyness that I can't actually be bothered with, it's sweet enough.
There is a slightly philosophical question though,
A rebuilt one, pro, probably looks more prototypical, con, a lot of effort
12BA standard, a lot less work and is it that noticeable. I don't know the answer and had I found the dry joint before I pulled it all apart I wouldn't have changed it, some food for thought.
Anyway she's working again and here awaits a green flag for the afternoon service. I really must paint the d*** thing.
To this, which you'll have seen before
When I built it I filled the tanks with lead shot which since they are open internally hasn't shown any sign of problems. The boiler, forward of the motor compartment is also filled with shot, although in this case just inserted and the hole in the boiler former sealed with plasticard so I can extract it. All up it weighs 2lbs or 900grams if you wish and after prolonged running the firebox is as warm as the full size one. Do the collective think this is due to excess weight or lack of ventilation?
My best wishes to you all
Martin