Stop in for a cup of coffee

Chassis​

1928 12B was the last Franklin to have a wood chassis frame.

Downdraft and Sidedraft Systems​

The mid 20's saw the introduction of the pressure cooling, also known as the 'downdraft' system by which the fan, now moved to the front of the engine, forced air via ductwork over the TOP of the cylinders and downwards over vertical cooling fins cast into the sides of the cylinders. The cylinders were one-piece iron with non-detachable heads. The Ser. 10 had steel fins cast into the cylinders. The Ser. 11 - 13 had phosphor bronze fins. All had a pulse oil system which sent oil under full pressure to each main bearing and connecting rod in pulses. If a bearing was lost, pressure was maintained in the rest of the system, a dubious benefit since running very far with one bad rod could result in crankshaft damage or crankcase damage if the rod let go.

All engines of this type were of 3 1/4" bore until the 135 engine which was increased to 3 1/5 x 4 3/4" stroke. The first series 10's were somewhat less than 30 horsepower, the final 135 engine was 65. All engines had overhead valves. The Series 13's were the first to use an AC fuel pump in place of the Stewart Warner vacuum tanks used from 1916 to 1928.

The great advantage of the downdraft system was the increased volume of air moved by the fan which was now pushing cooler, denser air instead of expanded, hot air which was pulled by the earlier flywheel/fan.

The disadvantage was the one-piece cylinder construction. It was very hard to cool the heads much and space for larger valves was limited. The result was occasional cracks in the cylinder heads and walls. In late '29, the factory cast a few iron cooling fins into the top of the cylinders. I have found that, oddly enough, these tend to crack more frequently than the earlier design.

The side-draft engines of 1930 - 1934 were certainly a great leap forward in performance and technology. One can always look to new technology and pass judgment on the old stuff as inferior in comparison. For its time, however, the downdraft engines were superb powerplants. They have a smoothness and quietness not found in the later side-draft design. The quality of construction was probably better than Franklin ever produced prior to, or after. The downdraft cars were and are capable of running full throttle all day long without detriment. The side-drafts, while beautifully engineered and certainly well built, produce so much more power that running full throttle all day long is not such a good idea as oil temps and piston speeds get out of hand.

Franklin Part Names​

Transverse engine - Cross-engine
Round hood - Barrel-hood
Cooling air flows down the cylinders - Down-draft
Hood style - Renault hood, Slop or soft-nose - Horse-collar
Name of body stylist – DeCausse
All Franklins from 1928 12A - Airman (except Olympic)
Air flows across the cylinders - Side-draft
Twelve cylinder - V12

Aluminum​

Franklin bodies were all aluminum until 1929 in addition to other parts like crankcase, transmission, rear end housings, pistons, rods, and many other parts were also aluminum. It is not surprising that at one time Franklin Automobile Company was the largest user of aluminum the world.