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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
 

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Hi Paul,

I live in Vermont and have enough snow on the ground that I can do little more than guess where my tracks are when I look out the back window.  It probably will be sometime in April before I can finally take my K28 outside and give it a good run.  I might take it to ECLSTS in York and try to exercise it on the steam track there - not sure.  I will get back to this thread with my observations when I've had a chance to give my loco a good run.

I did run it back-and-forth on a relatively straight section of Larry Green's basement layout (before I modified the suspension) and found that it seemed inclined to climb the outside rail on a left turn.  When I set about doing the suspension modification, I found a large, nasty machining burr on the flange of the right (engineer's side) front driver.  I think that almost certainly caused the climbing and I carefully filed it clean.  So far, that's the only manufacturing error I've found and it was easily fixed.

Llyn
 

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Yeah, me too, Llyn - I've given up trying to keep the GCHRR clear. Way too much snow this year, and whats there now has a lot of ice in it. Trying to clear it only damages roadbed. Ok, let me know when you get to try it. It'll be April or May for me too before anything runs at my place by the look of it.
 

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On my Mogul I'm having issues with the pony truck derailing on any thing less than perfect trackwork, so I'm all ears when it comes to suspenion tuning. Please don't let this thread die.
 

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I'll be the first to suggest that you fix the trackwork.

Actually I've never experienced and problems with my Mogul..
 

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Posted By Shay Gear Head on 03/05/2008 1:23 PM
I'll be the first to suggest that you fix the trackwork.

Actually I've never experienced and problems with my Mogul..


No, that would be MY Mogul.:D
The strange thing is it doesn't derail on the iffy section (where the neighbors tree fell during a hurricane and I straightened with my knee/DesktopModules/NTForums/themes/mls/emoticons/whistling.gif).
 

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Discussion Starter #7
Posted By Shay Gear Head on 03/05/2008 1:23 PM
I'll be the first to suggest that you fix the trackwork.

Actually I've never experienced and problems with my Mogul..



Actually, Bruce, you won't be the first, as we talked about that in a previous thread.  :) Agreed, there may be some tweaking needed on track, and I certainly will (have to) after the winter, but the Mogul is the only one of 12 locos I have that won't stay on.  The suspension on mine does not  work as designed, and the derailing is consistent with the suspension problem.   After I sort out the suspension, if I still have the problem, then I will look more closely at the track, but if the suspension works like its supposed to, I predict the problem will go away.
 

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Skip, It's actually a kind of inside joke. Bruce and I are talking about the same exact model. I bought it from him last spring. And my track work is suffering.

But I must agree that the Mogul is much more picky about track issues than my other engines. Ruby (Forney), Frank S, C-16, Shay, Wangerooger, Willi will all run on my track with any issues. So, in the spring.....
 

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Discussion Starter #9
Hi Dave, yeah I got that  :)  Before I mess with the track, I want to sort out the suspension. Wouldn't surprise me that (in addition to the long wheelbase), suspension travel issues are behind a lot of the finickiness. I have one rear driver that has NO vertical travel at all, while its pair moves about 1/16. The others move variously 1/16 or less. The suspension itself will allow about 3/32 if the retainers didn't hold up axles so high. If I can them all to be consistent to be about 5/64 then I think it will run like a champ. The way it derails is consistent with a bump on the rigid driver bouncing the driver off rather than absorbing the bump. We'll see - like Llyn, it may be a couple of months before I see my track again... /DesktopModules/NTForums/themes/mls/emoticons/sad.gif

Re the front pilot wheels, check the spacing (and the spring tension), I'll bet its not in gauge.
 

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Posted By Skip on 03/07/2008 3:23 PM

Re the front pilot wheels, check the spacing (and the spring tension), I'll bet its not in gauge.


I was double heading a couple weeks back with a friend who has the NCNG #2 Mogul and my pilot would seem to jump up higher than his over a couple of gaps in the rail. I was leaning toward more tension by adding spacers or streching the spring but I will definitely check the gauge in the AM. Thanks for that tip!

While I have it on the bench, I'll have a look at the driver suspension travel and report back my findings.
 

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Discussion Starter #11
I had that problem with my B'mann Connie until I regauged the pilot and stretched out the spring - now it behaves quite nicely.
 
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