Dave Holt
Western Thunderer
My BR 9F, built from a Model Loco kit with Gibson milled frames and coupling rods (correct axle spacing), was never my best runner, in terms of slow running due to excess slop in the horn guides and axleboxes, but was OK at line speed until it suffered a major mishap whilst running round Dewsbury at S4 North a few years ago. One of the return cranks unscrewed, allowing the connecting rod to come off the crank pin and jam the motion solid and knocking the quartering out and locking the compensation into a contorted, rigid misshape. Not only that, but the joint between the two parts of the extended High level gear box broke and allowed the geometry, which allowed the motor and box to fit into the firebox and ash pan, to be lost.
Subsequently, I partially stripped the chassis and fixed it as near to the original arrangement as before. However, for whatever reason, it ran worse than it did previously, so the loco was confine to the bottom of the stock cupboard and has rarely seen the light of day since - just posed as a static loco a couple of times.
In anticipation of an upcoming visit to a large layout where it would be an appropriate loco to run, I decided to have another go at improving the running, at least back to what it had been. This has been done over the past few days.
Loosening the final drive gear on the axle, to allow finger propulsion, showed no appreciable unevenness or jerkiness in the chassis and the coupling rods appeared to be straight at front and back dead centres, so it appeared that I had manage to re-set the quartering correctly, which pointed the finger at the gearbox and motor mounting. Attempting to lift the driven axle (4th) or rear axle off the rail revealed that the driven axle had no appreciable suspension movement, suggesting that either the motor was touching the top of the firebox or the underside of the gearbox was sitting on the top of the rear axle or the outer end of the motor shaft/worm was touching the rear axle - there was a witness mark of grease on the rear axle. However, with the loco upside down, it was hard to tell where the normal running position of the axles would be so it was a bit inconclusive. I decided to increase clearances anyway, to make sure nothing was touching where it shouldn't.
With the torque reaction pin removed and the DCC chip moved out of the way, it was possible to access the motor retaining screws and remove the motor without having to strip any of the chassis components - phew!
With the motor off, the underside of the gearbox was filed away above the rear axle and the end of the motor shaft and worm shortened using a slitting disc in my mini-drill. This created acceptable clearances without affecting engagement of the worm with its worm wheel. Trial reassembly with the body showed that whilst some improvement had been achieved, the driven ax;e still had little suspension movement.
At some time previously, I had rotated the square-ish moto body to a 45 degree position so that the mounting screws could be accessed and it appeared that the corners of the motor might be catching inside the firebox, where I had made a plastic card box to hold back the lead shot weight and leave room for the motor. So out with a router bit in the drill and the sides of the box and some of the lead shot were cur away to give more space. Voila! Acceptable axle movement and a reduction in the graunching sound from the drive train.
It still doesn't crawl, but at least the loco is usable again, so a positive achievement.
I didn't take any photos of the actual rectification work - not that much to see - but here are a handful of shots of the loco and the chassis separated from the body.
First, some shots of the complete loco, taken many years ago by Barry Norman, for possible publication in MRJ, although they never were. I hope he doesn't mind me showing them here.
And some shots of the chassis separated from the body ready for the attempted rectification work.
Dave.
Subsequently, I partially stripped the chassis and fixed it as near to the original arrangement as before. However, for whatever reason, it ran worse than it did previously, so the loco was confine to the bottom of the stock cupboard and has rarely seen the light of day since - just posed as a static loco a couple of times.
In anticipation of an upcoming visit to a large layout where it would be an appropriate loco to run, I decided to have another go at improving the running, at least back to what it had been. This has been done over the past few days.
Loosening the final drive gear on the axle, to allow finger propulsion, showed no appreciable unevenness or jerkiness in the chassis and the coupling rods appeared to be straight at front and back dead centres, so it appeared that I had manage to re-set the quartering correctly, which pointed the finger at the gearbox and motor mounting. Attempting to lift the driven axle (4th) or rear axle off the rail revealed that the driven axle had no appreciable suspension movement, suggesting that either the motor was touching the top of the firebox or the underside of the gearbox was sitting on the top of the rear axle or the outer end of the motor shaft/worm was touching the rear axle - there was a witness mark of grease on the rear axle. However, with the loco upside down, it was hard to tell where the normal running position of the axles would be so it was a bit inconclusive. I decided to increase clearances anyway, to make sure nothing was touching where it shouldn't.
With the torque reaction pin removed and the DCC chip moved out of the way, it was possible to access the motor retaining screws and remove the motor without having to strip any of the chassis components - phew!
With the motor off, the underside of the gearbox was filed away above the rear axle and the end of the motor shaft and worm shortened using a slitting disc in my mini-drill. This created acceptable clearances without affecting engagement of the worm with its worm wheel. Trial reassembly with the body showed that whilst some improvement had been achieved, the driven ax;e still had little suspension movement.
At some time previously, I had rotated the square-ish moto body to a 45 degree position so that the mounting screws could be accessed and it appeared that the corners of the motor might be catching inside the firebox, where I had made a plastic card box to hold back the lead shot weight and leave room for the motor. So out with a router bit in the drill and the sides of the box and some of the lead shot were cur away to give more space. Voila! Acceptable axle movement and a reduction in the graunching sound from the drive train.
It still doesn't crawl, but at least the loco is usable again, so a positive achievement.
I didn't take any photos of the actual rectification work - not that much to see - but here are a handful of shots of the loco and the chassis separated from the body.
First, some shots of the complete loco, taken many years ago by Barry Norman, for possible publication in MRJ, although they never were. I hope he doesn't mind me showing them here.
And some shots of the chassis separated from the body ready for the attempted rectification work.
Dave.
