Heisler S/N 1577 - Singer Mfg - Thurso & Nation Valley RR #3
Text below from http://www.railways.incanada.net/thurso/tnvrloco.htm#no.3

#3 was a three truck Heisler geared locomotive built new for the TNVR in May 1929. It weighed 70 tons in working order and was built to the older Heisler design with slide valves, although it did have an all weather cab. #3 was shipped from Erie, Pennsylvania without lettering and it may have stayed that way for its working life. The locomotive would have been hauled to Thurso on its own wheels with the gears being removed from the axles. This would make the rest of the working parts inoperative and it would roll freely in a train, just like a car. A travelling engineer would have accompanied the locomotive to Thurso to ensure proper lubrication and to put it into service upon arrival. He was required to live in the cab and living quarters were provided by building a bunk in the left hand side of the cab. A few shelves were installed for storing groceries and other items. He was supplied with bedding, a stove, cooking utensils, lantern and other articles. The bunk also served as a table and a nail keg for a stool. Locks were provided on the doors to keep out thieves when he was absent for any reason. 
The Heisler locomotive was designed specifically for logging operations with steep grades, sharp curves and light rail. The 70 ton model would negotiate a 100 foot radius curve and operated on rail as light as 45 pounds per yard. On level track it would haul 4352 tons while on 9% grades it could handle 108 tons. The capabilities of #3 had quite an influence on the construction of the TNVR branch lines. 
#3 was a powerful, but very slow, machine which took four hours to move twenty cars to Singer from Thurso. For this reason it was generally restricted to the operations north of Singer where it spent most of its time outside in the woods.  <tnvdia44.htm>At first an inspector was sent into the woods to examine the locomotive as well as the steam log loaders. This practice was changed in April 1936 <tnvdia36.htm> when it was felt that the TNVR engineers were sufficiently experienced to make the weekly inspections. 
Being kept most of the time in the woods there was some concern expressed over the care taken by the engineers. <tnvdia36.htm> By November 1941 #3 was due for heavy work. <tnvdia40.htm> 
#3 was replaced by the first TNVR diesel, #4, in 1946 and was scrapped at Thurso in 1947 by Zagerman's, a long established Ottawa firm. Some parts of the locomotive are believed to have survived. A piece of steel which looks suspiciously like a sand dome or a steam dome was left outside the Car Shop and is currently doing duty as a sump in the floor of the Car Shop. 
The principal dimensions of #3 were: 
Cylinders 16 3/4" X 14" 
Driving wheels 36" 
Boiler pressure 200 lbs/sq. in 
Tractive effort 40180 lbs 
Wheel base: 
- rigid 56" 
- total 39' 4" 
Length overall 49' 4" 
Capacity: 
- water 3430 gals 
- coal 10600 lbs