From the November 1936 issue of Motorcyclist Magazine
The double loop trussed frame, as introduced in the 61 o.h.v. during 1936 is being extende
The prelude to any discussion of Harley-Davidson design for 1937 must necessarily start with some mention and explanation of the o.h.v. 61 which was experimentally introduced in 1936.
After long engineering development, 70,000 hours of testing, and studied showings to old experienced riders the 61 was placed upon the market without the usual advertising and sales effort accompanying the introduction of a new model. It was a definite program intended to get owner-reaction and owner-experience. In the total there were approximately 2,000 machines of that model gradually put into service to test new departures in design.
With the results of that campaign as a gauge there are many major changes in all models of Harley-Davidson for 1937, and the items of new design constitute a very favorable testimonial for the fundamental success of the new features in the 61.
There is no doubt that the double loop trussed frame provided handling qualities which met with instant approval. Technically it not only gave strength but established a low saddle position, and dropped the center of gravity of the whole machine. In the new models the frame will be used on the 61, 74 and 80 models. To adapt the frame to the 74 and 80 models larger front frame members have been used-larger in diameter and of thicker gauge steel, each carries a six-inch reinforcement and ties into a drop forging at the bottom providing for sidecar or package truck attachment. The top frame member incorporates an eleven-inch reinforcement between seat post and seat bar connection. Rear stays are made of heavier gauge steel. The transmission mounting bracket is stronger and a hardened steel stabilizer bushing has been put on the seat post mast.
The circulating pressure oiling system as used on the 61 has been extended to all models. A main feed pump mounted on the gear case cover in the 45, 74 and 80 models, and mounted on the crankcase in the 61 o.h.v. model, introduces oil from the supply tank. A vane type pump is used in the 45, 74 and 80 models, driven by the rear exhaust cam gear shaft. The pump in the 61 is gear type, driven from pinion shaft. Oil under pressure is delivered through pinion shaft, flywheel, crankpin to lower connecting rod bearings and all motor surfaces. In the 61 a by-pass from the main feed line carries oil to rocker arms and valves and a positively timed rotary breather valve driven from the cam gear, carries oil and mist in the motor to the gear case basin. A screen is incorporated in the breather valve. A scavenger gear pump on the crankcase returns oil to the tank.
A welded steel saddle-type tank such as will be standard on all models. This teardrop desi
In the 45, 74 and 80 models, oil and mist in the motor are blown through a vertical breather valve, operated from pinion shaft, into the gear compartment. Oil condenses, passes through a cone sieve into the gear pump underneath the gear compartment and is returned to the tank. A vent pipe on all models leads from the tank to the gear compartment.
A one-gallon steel oil tank, around the battery, holds the oil on 61,74 and 80 models, while on the 45 the tank lies parallel to the gas tank and has a capacity of one and one-eighth gallons.
The front chain on all models is lubricated from the motor.
An instrument panel which includes speedometer, ammeter, oil pressure gauge, ignition and light switch, and lock, is used-the same as appeared on the 61. This will appear on all models.
Ignition and light switch are master key locked and when “off” eliminate tampering, it being impossible to even blow the horn.
Welded steel saddle-type tanks of teardrop design are featured on all ‘37 models. These new rigid tanks are three-point mounted to the frame.