[Land-speed] Multiple Engines

[Neil Albaugh]

John;

Crankshaft designs vary depending on what the engine is designed to drive. 
An aircraft engine drives a propeller, which is considered a "flexible 
load". Their crankshafts are light and so they lack the torsional stiffness 
of an automotive crankshaft. They also run at a relatively low RPM; even so, 
some engines have a section of the tach with a yellow segment and a warning 
not to operate for a long time within this RPM region. This is because it is 
a high harmonic vibration RPM and would cause eventual fatigue failure.

The old Mercedes GP car had a straight 8 cylinder engine but took the power 
off the middle of the crank to get around the long straight- 8 crank 
flexibility problem. They essentially converted the straight- 8 to two 
coupled inline 4s.

Regards, Neil  Tucson, AZ

--------------------------------------------------
From: "John Burk" <joyseydevil at comcast.net>
Sent: Tuesday, March 23, 2010 5:41 PM
To: "LandSpeed List" <Land-speed at autox.team.net>
Subject: Re: [Land-speed] Multiple Engines

> I think crankshafts are stout to raise the harmonic frequency and resist 
> bending . For torque capacity think how small the transmission input shaft 
> is .
> John
>
>
>
>> List,
>>
>> When connecting two engines together at the crankshafts, what is the best 
>> offset to use? My thought is that harmonics should be arranged such that 
>> the rear crankshaft gets as little abuse as possible. Ideas?
>>
>> Thanks,
>> Skip