I started this thread in the old forum just before we returned to the new layout, and I want to keep it alive for a bit, as I'm still collecting info/experiences on this topic. The quotes below are from the previous version of the the thread, and Lynn Rice's interesting reply. Lynn, if you've had a chance to get the modified K28 on a track I'd like to hear how you made out...
As I mentioned in the "first impressions thread, I'm also looking for some input on how best to set up a throttle servo (I have tons of radio gear) in the Mogul. Presently the Goodall valve appears to be in the way, but I'm not using it anyway, so it can come out (offhand, anyone know the thread diameter of the valve so I can pick up a bolt to close the hole?).
After ranting some about teething issues with my new Mogul, and listening to various observations abut the running problems I had experienced, I took a closer look last night at the driver suspension, and discovered a problem. The right rear driver bearing will not move in its track, once the retaining plate at the bottom is screwed on. Originally I suspected paint was binding the block in the frame, but after disassembly and dressing the frame tracks, and reassembly, I discovered the retainer plate was locking up the bearing block by holding it up too high in the frame. The other side has about 1/16 (at least) free play. This is the reason the loco was bumping off the track and derailing on the rear drivers.
The retaining plate is bent at 90 degrees in the centre to form a shelf on which the bearing block sits when its fully down. I'm guessing at the moment that the retainer plate is bent too high and holding up the block.
Looking more closely at how Accucraft puts the retainer on, it conceivably could be inverted and reversed, putting the shelf at the bottom and increasing the travel of the drivers considerably, so that they actual get to work their springs properly. However, a spacer is needed to hold the retainer plate clear of the bearing block so that it doesn't bind in the lower part of its movement. Reversing the blocks appears to be a worthwhile revision for the extra suspension travel gained and the spring complement would actually work as designed without removing any.
So, after a lot of talk, what have others done to tune up the suspension the Mogul? At a minimum, I have to get some more movement in the right rear drive, or this loco will never stay on the track.
Paul
Posted - 01 Feb 2008 : 14:12:11 Show Profile
Hi Skip,
I found essentially the same thing with my K28. With the retainers in place as installed at the factory, the springs were fully compressed and the driver axels had virtually no vertical play. Based on a suggestion from Rick Richardson of the New Jersey Live Steamers, I turned my retainers over so the shelf would be at the bottom. I also had to space the retainers out from the frame to let the bronze journal blocks slide down behind them. On the K28, the retainers are secured with M2.0 x 4 flat head metric screws. I got some longer M2.0 x 6 screws and some 2mm washers. I found that putting two washers between the retainers and the loco frame gave enough clearance (except one journal where I had to use three washers). That gave plenty of flexibility, but the loco stood about 3/32" higher than before (not a big deal), but I soldered some shims to the retainer lips to limit the travel a bit and split the difference between maximum possible travel and no travel. Now, the suspension is quite flexible and the loco looks just fine. There is plenty of snow and ice on my layout just now; so, it will be a while before I can give the loco a really meaningful test run.
Llyn
As I mentioned in the "first impressions thread, I'm also looking for some input on how best to set up a throttle servo (I have tons of radio gear) in the Mogul. Presently the Goodall valve appears to be in the way, but I'm not using it anyway, so it can come out (offhand, anyone know the thread diameter of the valve so I can pick up a bolt to close the hole?).
After ranting some about teething issues with my new Mogul, and listening to various observations abut the running problems I had experienced, I took a closer look last night at the driver suspension, and discovered a problem. The right rear driver bearing will not move in its track, once the retaining plate at the bottom is screwed on. Originally I suspected paint was binding the block in the frame, but after disassembly and dressing the frame tracks, and reassembly, I discovered the retainer plate was locking up the bearing block by holding it up too high in the frame. The other side has about 1/16 (at least) free play. This is the reason the loco was bumping off the track and derailing on the rear drivers.
The retaining plate is bent at 90 degrees in the centre to form a shelf on which the bearing block sits when its fully down. I'm guessing at the moment that the retainer plate is bent too high and holding up the block.
Looking more closely at how Accucraft puts the retainer on, it conceivably could be inverted and reversed, putting the shelf at the bottom and increasing the travel of the drivers considerably, so that they actual get to work their springs properly. However, a spacer is needed to hold the retainer plate clear of the bearing block so that it doesn't bind in the lower part of its movement. Reversing the blocks appears to be a worthwhile revision for the extra suspension travel gained and the spring complement would actually work as designed without removing any.
So, after a lot of talk, what have others done to tune up the suspension the Mogul? At a minimum, I have to get some more movement in the right rear drive, or this loco will never stay on the track.
Paul
Posted - 01 Feb 2008 : 14:12:11 Show Profile
Hi Skip,
I found essentially the same thing with my K28. With the retainers in place as installed at the factory, the springs were fully compressed and the driver axels had virtually no vertical play. Based on a suggestion from Rick Richardson of the New Jersey Live Steamers, I turned my retainers over so the shelf would be at the bottom. I also had to space the retainers out from the frame to let the bronze journal blocks slide down behind them. On the K28, the retainers are secured with M2.0 x 4 flat head metric screws. I got some longer M2.0 x 6 screws and some 2mm washers. I found that putting two washers between the retainers and the loco frame gave enough clearance (except one journal where I had to use three washers). That gave plenty of flexibility, but the loco stood about 3/32" higher than before (not a big deal), but I soldered some shims to the retainer lips to limit the travel a bit and split the difference between maximum possible travel and no travel. Now, the suspension is quite flexible and the loco looks just fine. There is plenty of snow and ice on my layout just now; so, it will be a while before I can give the loco a really meaningful test run.
Llyn
