Resonance.

God's gift of humility.



* Jim Bede, of course, with the BD-5 drive train.
Hard times and heartache...
That engine and drive ran flawlessly 24/7 for months without a single problem.
It looked goooood!

But bolted into the airframe, it would come apart in minutes.

Back on the test stand (concrete block!) it ran and ran and ran.
(the energizer bunny hadn't been born yet)

But in the airplane... pure bad news.

Now you tell me. Where's the logic in that???

As it turned out, all we needed to do to solve the drive problem on the -5
was to fill the belly of the airplane with a few inches of concrete.
(well, it's not a *great* solution, but it would fix the drive problem!)



* Molt Taylor and his AeroCar. 1950's chic!
Here is a really *good* long drive shaft problem.
I say good because it has a happy ending.

The patented "Flexodyne"(sp?) drive shaft damper.


* Tail rotor drive shafts on almost any rotary winged beast.
(Shudder)


As for engines on experimental aircraft?
My attitude parallels Peter's.

I used to see it as a way to get airborne for a few dollars less.
And in some (small) cases, VW, simple Subes, Geo, and the like, it may
still be a valid way to go.
A-65's don't grow on trees anymore.

But I too have come back to the olde timy 1930's tractor engines as the
solution for fast iron (or wood or plastic as the case may be).

Those engines evolved(?) to be the way they are because that's what does
the job best. Long stroke, slow turning, light weight, reliable.


My personal reason is weight.
Pure and simple.

Our (small experimental) airplanes are - for the most part - simply too small
to carry the extra weight *well*.

Lighter is better.
Hey!
It's a freekin airplane!
(chant mantra - lighterisbetteroooommmm...)


There is, also, that old saw about not mixing experimental engines with
experimental airframes. I wonder what nut came up with that one?



But then the topic is resonance, isn't it.
And?
With the exception of combinations which are known to have engine/prop/AIRFRAME
resonance issues (hint, hint, hint), certified engines avoid that trap entirely
(well, mostly?).


That's not my $.02,
It's my bunch of thousand bucks...
And?
In the end, my ass, and maybe yours?


Richard

for what it's worth