The online magazine on the history and operation of vintage scale model trains in American OO gauge

Saturday, April 17, 2010

MHP Passenger Car Diaphragms

One item that was a very popular one with post-war OO gaugers was MHP diaphragms. Most anyone with a good collection of OO passenger cars today will have seen these and perhaps wondered what they are.

Monroe Hobby Products (MHP) was active in the OO market out of Rochester, NY, from 1953/54 until at least 1959, with the line available in other scales by 1952 (initial offerings were HO and O gauge; these were also produced in S gauge). In the first photo may be seen two of these folded rubber diaphragms, one mounted on a streamliner and the other loose. The strike plate is aluminum and has the patent number, and the interior divisions are cardboard.

These seem to have held up very well in spite of their age of being made around 60 years ago, and a good pair enhances the value of any OO passenger car.

The second photo shows an example of the box that these were shipped out in. The instructions inside contain these important notes:
M-H-P Diaphragms are designed to compensate for the variable distance between cars. They provide an unbroken connection between coupled cars during any and all train operations providing the cars are run on not less than the recommended NMRA minimum radius of track for their gauge.
The example in the first photo mounted on the car has the "tabs" bent in; ideally MHP wanted those to be out which was part of how they connected from car to car.

Myself, with my smaller radius curves, I find they work the best with the tabs bent in, and most of them that came to me mounted on cars were also shortened by one fold before they came to my possession.

Finally, I should note these were produced, to quote the wording in their 1953 advertising, in "all popular sizes," and there was specific advertising on the (new?) OO version in Model Railroader starting in 1954, seen here. Also, it is worth noting that the instructions give specific tips on modifying the product for use on S and O gauge toy trains.

Updated 2014

1 comment:

Steve B said...

If you can locate the patent papers for the MHP diaphragm, it will show a concept with additional mechanical parts, beyond what made it into production.
I may have downloaded the patent papers years ago but no longer have them available.
FWIW, I also cut off the tabs, in O scale