3M Engines

[GREEN, DOUG]

Eric,

The Hyde mount design intent was to have the center of mass of the
engine and the center of rotation at the same point.

Do we really know the center of mass of these newer engines?

Does the center of effective mass change when the header/coupler/pipe is
attached?

An experiment:

Install metal shims of various thicknesses between the Hyde mount beams
and the engine mounting lugs to shift the center of effective mass of
the engine/header/coupler/pipe

Measure aileron servo current consumption

It may be possible to optimize the performance combination of mount and
the engine/header/coupler/pipe.

Doug


> "Henderson,Eric" wrote:
> 
> There is a time when a 2-c idles so low that it "bounces" as much as a
> 4-c at idle. Basically it is missing a beat so that it is firing at
> the same frequency as a slow running 4-c. At around 2000-2500 rpm they
> both smooth out.
> 
> I have extensive time on 1.40, and now 1.60, 2-cycles that lets me
> compare them with the big YS 4-c's and how they run and shake a plane.
> I have run both engine types with and without nose rings.
> 
> My goal was to get a plane that is shaken and "punished" the least!
> (Not ignoring sound issues BTW). I have observed that the best set-up
> is a non-nose ring Hydemount. All nose-rings add to airframe
> vibration. They provide poor isolation and have to be set with no side
> pressures to be iso-effective.
> 
> All my nose ring installations cause aileron-buzz at certain - read
> most used in flight - rpm settings. This just kills the digital
> aileron servo!
> 
> The 4-c is the worst culprit by far. The DZ is a shaker and this may
> be why the fuel foams and causes dead stick's at low rpms. The L is
> smoother but the more nitro you use the more "bang" and thus the more
> energy to dissipate.
> 
> The smoothest set-up, by far, is a 2-c with no-nose ring. There
> appears to be no problem with the engine and prop torquing/twisting.
> The newer planes have room for a bigger hockey-puck-rear-plate. Planes
> with FG cowls are much easier to install without Herculean engineering
> of a nose ring support.
> 
> I have put 4 and 2-cycles in the same airframe on the same mounts and
> same range of props and I have seen a distinctly better isolation when
> the 2-c is installed. The current batch of Webra 1,45, OS 1.40 RX and
> FI users can probably tell us what they are seeing.
> 
> The "Mintor-men" will soon be reporting as well - right guys?
> 
> From a noise point of view my Hydeout with an L, is quieter that my
> Temptation with an OS 1.60, that is quieter than my Hydeout with a
> DZ.... Not by much however...
> 
> Regards,
> 
> E.
> 
>

=====================================
# To be removed from this list, send a message to 
# discussion-request at nsrca.org
# and put leave discussion on the first line of the body.
#