Hisso reduction gear...

retread · 29 June 2006, 06:36 PM

Much of the blame for the early unreliability of the Hispano-Suiza 8B takes the form of "problems with the reduction gear". Anyone wish to shine a little more light on this ? Specifically, what kind of problems with the reduction gear?

StephenLawson · 30 June 2006, 03:28 AM

What I have read was, that is was the gear itself failing, broken teeth, fracturing, stress related problems. Mr. Alan Toelle would be the man to know for sure.

Troy Raines · 30 June 2006, 07:03 AM

If memory serves, the gears were improperly hardened leading to the mentioned failures.

Lufbery · 30 June 2006, 07:47 AM

Furthermore, there were four companies making Hispano-Suiza engines for the Spad 13 (and tw0? or so companies making aiframes). Generally speaking, parts were not interchangable among engines from different manufacturers.

Pilots, especially liked getting Hisso-Hisso Spad-Spads -- that is, a plane where the airframe and engine were not built by different firms under license.

I'm pretty sure that Spads of different makes were mixed together in squadrons, so the spare parts situation must have been a nightmare.

Regards,

retread · 30 June 2006, 06:23 PM

Thanks gents. There were several types of reduction gears used in aviation engines 14-18 that I am aware of. A standard reduction gear with either straight cut or herringbone gear teeth. As well as probably several types of epicyclic type reduction gears which were much more complex. A standard type with straight cut teeth apparently being the most reliable in the high tradition of K.I.S.S. (keep it simple stupid). Anyone familiar with the type of gear in the Hisso 8B?

StephenLawson · 30 June 2006, 07:01 PM

Alan Toelle. Memorial Flight members or see the replica fellows.

Dan_San_Abbott · 30 June 2006, 08:41 PM

Retread:
I had a discussion with a Friend, Lee Branch about the problems with the geared Hisso. Iwas saying it was a failure to properly heat treat the reduction gear. He said it was a design flaw that created the problem. Lee said in the design of the copper tubulor feed pipe that brought oil to the gears was the problem, the thickness of the wall was insufficient, and failed under pressure, with the result the gears failed. He said Hispano-Suiza did not want it known that it was adesign failure, not a manufacturing failure, which is what Hispano-Suiza pronouced.
Eight companies made the Geared Hisso used in the S.E.5a and the SPAD XIIIc1, they were: Hispano-Suiza, Five-Lilles, Mayen, De Launnay-Belleville,
Brasier, Peugeot, Wolseley, Wright-Martin.
Blue skies,
Dan-San

franzkait · 1 July 2006, 02:16 PM

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retread · 3 July 2006, 02:59 PM

Thats graphic enough. Looks like a kid dropped the clutch on his hot rod.

mustang · 3 July 2006, 07:27 PM

From an engineering standpoint a straight cut reduction gear is generally stronger, more reliable and more economical to produce than helical cut gears, albeit more noisy. Eamples: The Merlin, Allison and DB series. Epicyclic
gears find favour on radials in order to keep the centre line of the prop. shaft
on the centre line of the crank.

There was one low powered British radial in the 30s with straight cut gears; it looked rather odd with the prop. hub up almost in front of the top cylinder.

There have probably been others but they were fairly rare.

regards

Mustang.