Getting back to your coupling woes
if you come down from the MMI locos by using the overset Kadee HO couplings (#142/145/149) and come up from the Bachmann stock by using the underset coupler (#141/144/147) This will give you a coupling height somewhere between HO and On3 that will be for YOUR railway. Provided you keep your trains together as a unit you can run on others tracks. Lets see if it will work before you spend any money....
For Underset coupler looking at page HO3.6
The underset coupler raises the coupler centreline by 0.0625" to give a coupler c/line of 0.4535" above track for any bachman refitted stock
For the overset coupler -
The overset coupler lowers the coupler centreline by 3/32 or 0.09375 to give a new coupler centreline for any MMI refitted stock of 0.46925
Please check my calcs on all this.
The new MMi centerline is higher than the new Bachmann centreline by 0.01575"
Now given that the height difference on the new coupler centrelines is less than 0.02" they should couple and stay coupled. Your MAY have to bend the pins down by about 1/16" or so to get reliable uncoupling using Kadee magnets.
In short - yes it is now worthwhile looking at what type of coupler shanks will work best for your equipment - either the standard end or whisker end - My preference would be to go with the whisker couplers if they will fit the draftgear box on the rolling stock.
My head hurts now from all that figuring...but at least it looks like there may be a way to run all you On30 stuff and have it all stay hooked together.
Unanderra in oz
Thanks for that information. I assume the MMI K's coupling height is correctly set for On3 so it is useful to know that KD do an underset coupling (I didn't know that).
Rather than rush into building a subsequently unsatisfactory layout I have been temporarily spiking down various radii curves. At 30" radius the K's have noticeable 'flange squeal & unrealistic looking angle between loco & tender. At 36" radius they look & sound much better so I am altering my track design to 36" minimum, maybe a bit more though that will mean losing some track. I also was not aware of the K's problems on humps/dips so also my thanks for that.
Our 'Western' Class DH's had short operating lives & were always rather problematical.
My experience has been in HO and S scale narrow gauge. Specifically HOn30 and Sn2. The prototype two foot gauge lines in Maine used what is referred to as 3/4 MCB couplers. In HO this makes the Kadee N scale coupler about the correct size. In S scale the HOn3 coupler is the one used by most of the model community. I would suspect that one of the standard Kadee HO scale couplers would be approximately correct for O scale, but haven't verified it.
I know from experience in club layouts while I was attending university that the Kadee couplers on standard gauge HO lines perform well if the follow the mounting standards set by Kadee's various test jigs.
The trick is getting the trip pins at the proper height and the coupler centers to an accurate, repeatable height. When installed correctly in relation to one another, this line of couplers does perform well with hands off coupling and uncoupling.
If you are doing this on your own layout then these heights and interfaces can be whatever you set them to. If you want to interchange cars with another modeler or with a club, then they need to all be set the same.
I know the references for the two foot gauge lines, but would suggest looking to the NMRA standards for other gauges and scales. There are standards out there for this stuff and if they are followed by all of the parties involved, then interchangeability is possible.
____________________ Kent K
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