Problems with Japanese copy of DB601 engine.

[davebender]

The romance of engines - Takashi Suzuki - Google Books

- Induction hardening of crankshaft caused inadequate surface hardness. Excessive wear after 100 hours.
- Crankshaft shows precipitation of troostite, which indicates inadequate quenching.
There is a picture of troostite precipitated on an Ha-40 crankshaft.

I'll leave it to our engineers to explain what this stuff means.

 

[GregP]

When you form steel, it does not really matter what the Rockwell hardness is. When you want a specific ttype of steel, it does.

If you form a crankshaft and then decide to harden it, you must decide what Rockwell hardness to make it. Once it is a certain high hardness, it becomes brittle. Think of cobalt steel. Hard but brittle.

If you quecnh the steel, it will lose a several Rockwell points, but the brittleness will diminish decidely. The Japanese crankshafts were not sufficiently quenched and developed a micro-mixture of Ferrite Cementite, making them brittle.

It makes the crankshaft break under the strain. No power equals a descending aircraft.

 

[Shinpachi]

I heard the Ha-40 crankshaft did not contain nickel.

 

[davebender]

If you read further down there is a long winded discussion about bearing types. There is also a table which lists three main problem areas.

- Excessive crankshaft wear.
- Fuel injection problems. Why didn't they revert to a carburetor? IMO a good carburetor is better then a poor fuel injection system.
- Lubrication system problems. Daimler-Benz had to leap this hurdle also for the DB605A engine.