Miniature Trains manufactured a 1/4 sized F7 based on the EMD blueprints.
I worked on them for about two or three years at the Atlanta Zoo. We had two F7's, four (4) passenger cars, and one observation car.
Both locos were powered by a 4-cylinder Wisconsin air-cooled agricultural engine that as I understand it is still manufactured. It is of a 1947 design (as I recall). We altered the two F7's we had so there was an electric vacuum pump for the air brakes (vacuum) since the original design used the manifold vacuum for brakes.
The entire train set could be converted from 14" to 15" to 16" gauge by an ingenious way of changing spacers on the wheels and brake rigging. We had a spare truck which we did convert the brake rigging to 15" gauge to see how easy it was. It was just time consuming but not hard. The hardest part of the change would have been the wheel sets.
The Atlanta Zoo train's equipment was actually two different sets (one had a loco and two cars and one had a loco and three cars. One set built in 1952 and one in 1956). We were able to easily alter the pnuematic throttle and brake control on the one loco so that both locos could be MUed and either could lead. Only one was MU capable when originally purchased.
There are two types of couples used on the MT. one is a knuckle type coupler and one is a link and pin type coupler. The knuckle is not prototypic looking but is prototypic in operation. They were the original couplers on the train sets. After kids pulled the pin several times, the link and pin was converted to.
The link and pin style coupler was again not prototypic in looks but in functonality. The link was about a 2" diameter steel rod that fit snugly into the pockets and held in place by the pins. basically it formed a solid draw bar from kingpin to kingpin.
Alhough I was a part time employee, I helped restore the equipment to operating condition and maintained it once it was restored. I also filled in on occasional weekends to run the train. either loco could pull the entire train around the track (grades up to about 3% and curves as sharp as 50 feet) but usually we only allowed 4 cars per loco and went to double heading for 5 cars.
We were designing a signal system to allow two trains to run (same direction) when Zoo Atlanta decided they wanted to run the train consession themselves. They now have a 24" gauge trainset.
MT parts were still available as of about 3 years ago. Only car and loco bodies were not available. These bodies are in demand on the used market.
At one time MT offered switches and turntables and crossings and signal systems (mainly crossing gates) and quite a wide selection of accessories.
At the zoo, we had a passing siding at the station to allow us to put one train in while the second train was in use. They were stored in a tunnel overnight. Near one tunnel portal, a trailing point spur was installed with a small storage shed where we could put up one car or one car and one loco for repairs. The loco was about 10 feet long, a passenger car about 12 feet long and the observation about 14 feet long.
As I understand it, MT made the original F7 in 20" gauge (the only one built in that gauge). A photo of it has been on D.F.Barnhardt's site for about 6 months. I do not recall 12" gauge but I really did not follow anything outside of the 14-16" gauge stuff closely.
There was a 4-2-4 C.P.Huntington type steamer in 14-16" gauge that used the EMD diesel trucks for the front and rear trucks. A Wisconsin gas engine was the power. The driving wheels actually took power from the track and drove the piston. The cylinder (which would be the steam cylinders on the prototype) compressed air for the air brakes. If the driver slipped, you had no air for braking.
Success on this design drove MT and/or its successor to use the same designs on 24" gauge equipment. The C.P.Huntington style is currently used at Zoo Alanta in 24" gauge. Supposedly when the 4-2-4 first ran on the 24" gauge track that replace the decades old 16" gauge track, they did not check tunnel clearance and the stack was about 4" too tall. They ended up cutting down the stack.
I do not recall the name of the company that currently supplies the MT parts, but MT heritage designs are still being used today in 24" gauge.
Doug.
