FORK and BLADE connecting rods for a V8

Did anyone besides Lincoln use fork and blade connecting rods in their V8? I've got a set and would like to ID them. Bob

I think all V8s used that type connecting rod up to about 1930. Some for longer. It was standard practice on V type engines including V twin motorcycles.

Pictures, crankpin and wrist pin diameter, and length center to center will help.

Center to center on the crank and rod pins is 12 1/2 inches, not a high reving engine for sure. Bob

Cadillac were most prolific makers of fork & blade conrod V8s from 1915 to 1927, Bob. I will measure to get dimensions, but the 314 A, B, & C of 1926 & 7 had shorter rods than earlier models. The earliest ones may or may not have had slightly smaller crankpin diameter. My 1916 had been run as a V6, so I need one fork and blade pair for it. You can guess why Henry and Wilfred Leland apparently quarantined, the design of the V8 from previous engineering work. I have some familiarity with the copper-pot fours, and I have a 1913 project. But in a lot of detail they carried early stationary engine design concepts, and, like a certain expensive English automobile, they could have been described as a triumph of workmanship over design. When Ken Moss from Sydney drove with his family drove his 1912 from California to Detroit , to see the Indianapolis 500, to the top of Pike's Peak, then back to California for the voyage home, Cadillac did not know he was running alloy pistons on International Black Diamond Truck conrods instead of Cadillac single bolt hinged big-ends. And when they stretched the stroke to 6 inch in 1913, the engines could not run as high RPM as the shorter stroke 1912 because of the restricted left-and-right hand threaded sleeve that held each head to its barrel.

OK Bob. Twelve and a half inch conrod length between centres is from the first Cadillac V8 about 1915 build date , right through until the last V63 of 1924 or 1925. My 1916 has inch and seven eights crankpin diameter. V63 has two and three eighths inch diameter crankpins. Those were the first model with the split plane counterbalanced crankshaft. This was worked out by GM mathematician Hutchinson, and propelled by Charles Kettering and Alfred Sloan, according to what Ernest Seaholm told Maurice Hendry when he authored that book on Cadillac published by Automobile Quarterly, the change was made and in production during the time Seaholm was absent on a visit to Europe. Now though I have one of the last flat-plane crankshaft cars, a 1922 model 61, the engine appears to be good and it is all together in the car, so I do not know whether they increased the crankpin size before the change to the counterbalanced shaft. I would be very interested if your conrods would suit my 1916 Caddy.

Just for completeness, the 314 of 1926-7 has 10 7/8"centre to centre conrods, and with 2 3/8"diameter crankpins.

Description of a forked connecting rod.

The usual solution for high-performance aero-engines is a "forked" connecting rod. One rod is split in two at the big end and the other is thinned to fit into this fork. The journal is still shared between cylinders. The Rolls-Royce Merlin used this "fork-and-blade" style. A common arrangement for forked rods is for the fork rod to have a single wide bearing sleeve that spans the whole width of the rod, including the central gap. The blade rod then runs, not directly on the crankpin, but on the outside of this sleeve. The two rods do not rotate relative to each other, merely oscillate back and forth, so this bearing is relatively lightly loaded and runs as a much lower surface speed. However the bearing movement also becomes reciprocating rather than continuously rotating, which is a more difficult problem for lubrication.

Source, Wikipedia, the free encyclopedia

I wish loading photos was an easy thing on this site, if it was I would have posted photos in the OP. All surfaces on the rods are fully machined, maybe they are aircraft items. Bob

How bout this?

I found a reliable reference that the Cadillacs before the start of the V63 in late 1923 all had the same inch and seven eighths diameter crankpins of the flat-plane crankshafts. So the definitive identification is that with that bib-end bearing diameter and the length between centres that you stated they fit every model from 51 to 61, which is V8 Caddy from 1915 to early 1923. That length between centres with two and three eighths diameter bearing is V63 model only, from late 1923 to late 1925.

I would be interested if you want to dispose of some, Bob; because there is one pair missing from my 1916.