Post by Deleted on Feb 22, 2011 20:44:20 GMT
Well, here is the first post: it doesn't make good copy!
I had to first make a build stand that is a bit sturdier than the one for the Brit. It was easiest to screw it directly to the workbench.
A quick look round showed that the reverser action has over 1/8" of backlash in it, which limits its travel somewhat.
What really worried me was the fact that the reverser seems to be out of position, or the operating lever is 1/8" too long. The radius rod went from the bottom of the link to mid gear, and then stopped! I disconnected it and carried on regardless.
I was informed that someone had worked on it previously and that they had run on air, so I decided to test that premise before I stripped it down. It didn't go at all, and air leaked everywhere! Someone is telling porkies.....
I suppose I wasn't surprised to find that there were no gaskets at all on the steam entry ways, and the inside cylinder inlet flange was loose under the smoke box. New ones were made from proper stuff and fitted.
The cylinder drain cocks didn't close properly due to oversize holes and sloppy connections in the operating levers.
I repositioned the valve gear, in strict accordance with the manual. It doesn't actually give any guidance on timing methods: it just tells you where to position the bits initially and that's it.
Return Cranks
The return cranks were well out of position from the specified offset of 18.5mm: the LH side 3mm over, and the RH 5mm. These are huge errors, and the stripped fixing bolt on each pair of bolts may have had something to do with this. There is no positive drive e.g square spigot.
Piston valve position
The piston valve faces are supposed to sit 25mm back from the front face of the valve liner: the LH side was 27.5mm, the RH side 28.5mm. The centre cylinder was spot on. The valves are fitted with PTFE rings, but the nuts on both valve spindles were loose, and did not carry locknuts to keep the valves in the correct position. I’ve now ascertained that if the o/s piston valve spindles are positioned in accordance with the instructions, the conjugation gear jams up against the front guides on both sides when the spindles return. That is probably why the piston valves were set in the way I found them, to provide clearance.
The piston stroke on the LHS is 2.25”, but on the RHS it is 0.020” greater, probably indicating a wrongly positioned crankpin.
The slack in the valve gear is unbelievable: the combination levers alone float by over half a millimetre due to an oversize hole in each one and slack in the radius rod connections (both ends). The rest of it is not very good either....
Accurate timing like this will be impossible without fixing or replacing the valve gear. Does it need a redesign???
I tried to run it again. The air flies past the piston valves and doesn’t reach the cylinders. Hopeless!
It is also obvious that the wheels need reprofiling: they need a further 1.4mm machined off to meet the 3.6mm depth specified for 5"G by Tubal Cain in his handbook.
The presentation and finish of the motion work is just about the worst I have ever seen. Rough profiled edges with no attempt to clean them up.
I am now going to strip it all down and see what I am really up against....
Interesting stuff though!
JB
I had to first make a build stand that is a bit sturdier than the one for the Brit. It was easiest to screw it directly to the workbench.
A quick look round showed that the reverser action has over 1/8" of backlash in it, which limits its travel somewhat.
What really worried me was the fact that the reverser seems to be out of position, or the operating lever is 1/8" too long. The radius rod went from the bottom of the link to mid gear, and then stopped! I disconnected it and carried on regardless.
I was informed that someone had worked on it previously and that they had run on air, so I decided to test that premise before I stripped it down. It didn't go at all, and air leaked everywhere! Someone is telling porkies.....
I suppose I wasn't surprised to find that there were no gaskets at all on the steam entry ways, and the inside cylinder inlet flange was loose under the smoke box. New ones were made from proper stuff and fitted.
The cylinder drain cocks didn't close properly due to oversize holes and sloppy connections in the operating levers.
I repositioned the valve gear, in strict accordance with the manual. It doesn't actually give any guidance on timing methods: it just tells you where to position the bits initially and that's it.
Return Cranks
The return cranks were well out of position from the specified offset of 18.5mm: the LH side 3mm over, and the RH 5mm. These are huge errors, and the stripped fixing bolt on each pair of bolts may have had something to do with this. There is no positive drive e.g square spigot.
Piston valve position
The piston valve faces are supposed to sit 25mm back from the front face of the valve liner: the LH side was 27.5mm, the RH side 28.5mm. The centre cylinder was spot on. The valves are fitted with PTFE rings, but the nuts on both valve spindles were loose, and did not carry locknuts to keep the valves in the correct position. I’ve now ascertained that if the o/s piston valve spindles are positioned in accordance with the instructions, the conjugation gear jams up against the front guides on both sides when the spindles return. That is probably why the piston valves were set in the way I found them, to provide clearance.
The piston stroke on the LHS is 2.25”, but on the RHS it is 0.020” greater, probably indicating a wrongly positioned crankpin.
The slack in the valve gear is unbelievable: the combination levers alone float by over half a millimetre due to an oversize hole in each one and slack in the radius rod connections (both ends). The rest of it is not very good either....
Accurate timing like this will be impossible without fixing or replacing the valve gear. Does it need a redesign???
I tried to run it again. The air flies past the piston valves and doesn’t reach the cylinders. Hopeless!
It is also obvious that the wheels need reprofiling: they need a further 1.4mm machined off to meet the 3.6mm depth specified for 5"G by Tubal Cain in his handbook.
The presentation and finish of the motion work is just about the worst I have ever seen. Rough profiled edges with no attempt to clean them up.
I am now going to strip it all down and see what I am really up against....
Interesting stuff though!
JB
