Re: Arcane question of the week

Nelson Moyer <ku0a@...>

The car standards for the La Mesa Model Railroad Club are by far the most
stringent standards that I'm aware of, and I pasted in the center of gravity
standard in answer to your question.

I. Center of Gravity

1. Cars should be constructed to obtain the lowest center of gravity. The
minimum CG for any car is CG30.

2. ANY weight added to a car to make its' required weight should be kept
as low as possible (NMRA RP20.1).

3. The center of gravity of each piece of rolling stock (locomotives
excepted) shall be determined on a Protractor or Tilt Table and noted as its
Center of Gravity Index, (or CG)expressed in degrees, i.e., CG35. This shall
be the farthest deflection from the normal upright (0 degree) or vertical
position to which the car can be tilted, from a flat, level, horizontal
surface (90 degrees) on which it stands without tipping over. This will be
determined by using a vertical protractor arm moving against the flat
vertical side of the car, as the car is tipped sideways. The protractor
pivot center must be coincident with said horizontal flat surface. Adapter
blocks shall be used to establish a flat plane for the measurement of
equipment not having flat sides. A high CG index number indicates a low
center or gravity, i.e: CG90.

4. Rolling stock will be tilt (protractor) tested on both sides of car to
establish the CG Index. The poorest of the two readings (the lowest reading)
will become the CG Index for that car. Side to side differences exceeding 5
degrees should be corrected with counterweights or by relocating/removing
added weights.

5. Equipment may be required to be modified as necessary to achieve the
optimum weight/center of gravity.

6. The MINIMUM center of gravity index for any NEW registration car shall be
30 degrees (CG30), brass models MAY be exempted from modification that would
ruin their value- provided they cause no operating problems.

7. Existing equipment registered before the establishment of the CG index
WILL NOT be exempted, except on a "proof only' basis, and will need to be
upgraded to the current standard when repaired or inspected.

Nelson Moyer

From: STMFC@... [mailto:STMFC@...]
Sent: Friday, March 18, 2016 11:02 PM
Subject: [STMFC] Arcane question of the week

How far above the railhead would you say is the center of gravity for your
average empty STMFC?


Our software team has added curve resistance to the rolling resistance
values and while doing so tossed in something else for tipping over at some
relationship of curve radius, super-elevation, and speed. I think it's far
too sensitive but I need a decent center of gravity estimate to make the

Dave Nelson

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