A discussion of the attributes of the various narrow gauge models including HOe and HOm.
Locomotive Model Plans
Carton Built Models
Laser Cut Models
It’s actually about two different narrow gauge modeling gauges. Bemo primarily produces Swiss pattern NG models in HOm. HOm is the same as TT gauge, 12 mm, and represents meter gauge prototype as is commonly found in Switzerland.
HOe is the European designation for what we North Americans call HOn30. It’s 9 mm gauge, the same as N scale standard gauge. It’s more commonly modeled in countries other than Switzerland and represents a variety of gauges under 1 meter, primarily 750 cm, IIRC.
Modelers wanted to use HOm Bemo stuff on their HOe layouts. Bemo started divesifying its offerings to outside of Swiss prototypes. They started making convesion axle sets so that their HOm rolling stock could be converted to HOe easily. There are also some locos that can do the same thing, but these are diesel and electric ones, not steam AFAIK.
So Bemo lists both HOm and HOe on boxes for items that are compatible.
BTW, there is a Yahoo Bemo newsgroup and Bemo items usually bring pretty good prices on ebay, depdning on your plans.
Finally, the convertibility feature is something a few other manufacturers and some modelers take advanatge of. Liliput started producing a modern NG diesel a few years back, available for around $150 in the US, that comes in HOe, but converts to HOm with a conversion kit. What’s neat about the two gauges you ask about is that they barcket another popular narrowgauge, HOn3 at 10.5 mm. In most cases, a model that can be either HOe or HOm can also be HOn3 with a little work. That’s how my diesel #82 came about.