Fordson Major Diesel Crankshafts

I am restoring a 1956 FMD. Unfortunately, the crankshaft for it, shown on the left is worn beyond repair. It is numbered 6306-B. I got another crankshaft from a 1954 FMD, shown on the right, which is numbered 6306-A. The journals and throw as well as the overall size of both cranks look identical. The counter weights for the rod journals on the 6306-A crank are noticeably longer and heavier than the old crank. Also, the journals are cored out hollow. This is not the case with the old crank.
I am wondering if the new crank will function properly given the difference in counterweights. According to one source, the 1954 & 56 FMD’S both had the Mark I engine. This seems to indicate that the cranks should interchange. Can anyone shed some light on this matter?
Many Thanks!

The one with the hollow journals was the early MK1 crankshaft and was fine in petrol or petrol/kerosene engines. The one in my petrol/kerosene Major is 68 years old and still going strong. It was a problem in diesel engines and was prone to breakage so was superseded by the other one you have with solid journals. The original crank was easily damaged by quite small shocks when being transported, a local engineer that reground cranks in the 1950' and 60's for dealerships said that if anyone brought a load of cranks for regrinding, he would guarantee there would be one broken in transit.

Cranks are interchangeable from 1952 through to the end of production in 1964 and are still readily available new.

Forgot to say, check the timing gear, they look two different widths in the pictures. You may have a later timing gear train fitted and these will not match well with the narrower gears of an earlier engine.

Greetings Majorman: Thanks for the reply! Your information is very helpful.

Best
Tom R

This is kind of puzzling to me. I am informally interested in "Industrial Archeology" and always wonder to myself, "Why did they do this?"

Companies hate to have extra part numbers in inventory, so they try to make them backwards compatible. This engine was used in trucks beginning in about 1948 and should have had a lot of field testing by 1956. An underlying motivation is to minimize material, material cost, and weight, especially if we have the mind-set of Post WWII engineers with war-time experience. Think aircraft. This can be carried to excess, and found later to have been designed with a "too small safety factor".

Ordinarily, the counterweights should be big enough to offset the weight of the crankpins and about 1/2 of the reciprocating weight of the connecting rod and piston. Fine tuning works from this basis. So my question is how can it still be balanced in both cases? Did the newer model use aluminum pistons? Was it optimized for a different critical RPM?

Another factor that would warrant a new part number is the material. To make it more resistant to damage, more nickel could have been added in the
iron pouring stage. It costs more, but it is an easy way to improve the product's reputation. An even more drastic improvement would be a forged steel crankshaft, instead of cast iron.

My 1956 Fordson engine (gas, or petrol)came to me with a broken camshaft gear hub. It seemed to me a simple case of under-design. However there could be an underlying vibration and fatigue problem that didn't show up for a few years. The fix was, as stated below, wider gears, with wider front plate and new type of aluminum front cover. I don't understand the connection, but they must have used the opportunity to correct several deficiencies at the same time, thus causing less disturbance in the mind of the owner. Perhaps covered by warranty, but I doubt it. [A bit later, they completely revised the Cam gear and Camshaft interface.] The Fordson Major was lucky to gain a good reputation in spite of these various shortcomings. [Competitors also had a lot of teething problems with their early diesels.]

In my case, I obtained a used gear from an early diesel, and machined the flanks to the same width as the original. Hopefully it will work.

I also have a spare crankshaft, and we have a later Industrial model under repair. I will attempt to take pictures and examine the counterweight designs.

Yes, I have one of each, too. The above mentioned tractor (actually 1953) has the larger
counterweights.

Thanks for the info. Is your tractor with the larger counter weights gas or diesel? Does it run satisfactorially? Thanks.

Tom R