Prop balancing and assorted observations - long

I've had a kind of unnerving vibration in my RV-4 since first
flight. I looked into harmonic dampers, but they're pretty
expensive, so I decided to give dynamic balancing a shot first.
$200 and 1 hour later, my engine runs *much* smoother. It
measured 0.3+ ips on the first run, so the guy weighed and
added an AN-4 bolt, nut, and a few washers to the flywheel.
Next run it was down to 0.05 ips and felt markedly different,
much smoother and quieter. I ran out of time and weather at
the same time, so I haven't flown it yet, but I don't see how
it can't help but be smoother. It remains to be seen whether
or not I'll have the pronounced shake at some power settings
and speeds, but I've also cut back the baffles where metal
rubbed on fiberglass and tightened things under the cowl a bit.
We'll see.

A little disturbing when the A&P noticed that a screw had backed
out of the left harness-to-mag mount. As I was tightening
it I noticed that another was missing altogether - a single
screw was holding the left harness to the mag. I've replaced
and tightened everything and sealed the threads, and done
a thorough check of every other fastener under the cowl.
I *hope* it was vibration-related and that we've fixed the problem,
but you can bet I'll keep a pretty close eye on it from now on.
I also had to replace the oil temp sender which failed inside
the sender, again presumably (hopefully?) due to vibration.
Sandy at Grand Rapids came through for me and got a new
one out in what must be record time. They're very pleasant to
deal with.

Also took the opportunity to do a compression test (first one)
while the cowl was off. Three strong cyls, #3 (the continuing
problem child) was a little low, but the A&P said it *should*
come up as the engine breaks in. No valve leakage that he could
tell, it seemed like it was getting past the rings. Oil shows
a little blow-by too. Chrome cylinders with 20 hr, so my
assignment is to "run the [snot] out of it" and see if it
improves in 10 or so hours.

Things I love about this airplane (in addition to the usual stuff
you hear about RVs):

Grand Rapids Engine Monitor
4-cyl temps have really helped troubleshooting, and adjustable
alarms are a comfort.

AnywhereMap GPS
Awesome. Freakin' awesome.

160 KIAS in the overhead pattern and a 4g break to downwind.
Hehe. John Ousterhout once told me "I hope you don't start
doing those 'break' entries like the rest of the RV guys."
It's the only way I can slow it down. Ob.safety note: Only
at home when it's not busy and the wind favors a direct entry
to upwind.

Taildraggers for the brain-dead.
I've only got a little taildragger time, but (like the rest
of my experience) spread thin over a bunch of different types.
The RV-4 is by far the easiest-landing taildragger I've ever flown,
and that includes other RV's. Increased confidence and proficiency
probably have a lot to do with it, but that's the way it seems,
anyway.
Of course I still nearly had it off the runway once in a stiff
crosswind.

Electric Trim and Flaps.
I work the heck out of the trim, as you might expect in an airplane
with such a wide speed range. Lateral trim (electric or manual) is
an absolute necessity in flight test as far as I'm concerned.
Electric flaps are less of a struggle than manual at a fairly
high-workload part of the flight (see 'break entry' above ,
although manual (in a -6, anyway) aren't that big of a deal to use
either.


Things I'm still working on (that I'd do differently next time):

The panel:
The engine monitor is on a sub-panel, where it's out of my
primary scan. Given that I'm trying to keep a close eye on
temps, it's in a less-than-ideal spot. I wish I had room
for it on the panel.

Single radio, no VOR:
While I love the AnywhereMap stuff, I don't trust the iPaq
it's installed on. The batteries are ^(*)&. It's wired into
the airplane electrical system, but still needs to charge
in between flights. If it dies enroute or on an overnight
I'm committed to dead reckoning. As such I plan to stick
close to highways and well-defined landmarks for trips
over unfamiliar territory. A second comm, while certainly
not required, would be nice as well. I've got a handheld,
but haven't patched it into the comm system yet.

External power:
Dead battery. No external power jack. Do the panel crawl.

^*&%%*&( Switches:
I harp and harp and harp about human factors, and then I
use identical switches throughout the switch panel (in
my defense I *did* try and space them so that the differences
would be obvious). I've turned the electrical system off
at least once thinking I was turning off the fuel pump.
Now I look. I think I'm going to rotate the FP switch
so that it's side-to-side throw or put a different bat
on the master switch. At least it wasn't the mags.

Vacuum gyros:
A dead AH and probably dying VG. What with all the
solid-state (or nearly so) attitude systems out there
I don't see any reason to mess with these again.
Interestingly enough, the Falcon (electric) turn
coordinator is holding up better than the vacuum gyros,
in spite of its reputation.


Done for now.

Dave 'brain dump' Hyde

RV-4 in flight test, EAA Tech Counselor

"Dave Hyde" wrote in message
...
I've had a kind of unnerving vibration in my RV-4 since first
flight. I looked into harmonic dampers, but they're pretty
expensive, so I decided to give dynamic balancing a shot first.
$200 and 1 hour later, my engine runs *much* smoother. It
measured 0.3+ ips on the first run, so the guy weighed and
added an AN-4 bolt, nut, and a few washers to the flywheel.
Next run it was down to 0.05 ips and felt markedly different,
much smoother and quieter. I ran out of time and weather at
the same time, so I haven't flown it yet, but I don't see how
it can't help but be smoother. It remains to be seen whether
or not I'll have the pronounced shake at some power settings
and speeds, but I've also cut back the baffles where metal
rubbed on fiberglass and tightened things under the cowl a bit.
We'll see.

I've had dynamic propeller balancing done on every airplane I've owned.
It's absolutely the best dollars I've ever spent on maintenance. It can
make 4-cylinder engines feel like 6-cylinder.

I feel strongly the money spent is quickly recovered on the things that
don't break because of vibration. Just do it, you'll never regret it.

Bill Daniels

Bill Daniels wrote:

I've had dynamic propeller balancing done on every airplane I've owned.
It's absolutely the best dollars I've ever spent on maintenance. It can
make 4-cylinder engines feel like 6-cylinder.

I have a dynamic balanance done every time my prop is R&R'ed on the plane.
Unfortunately, on my prop (a Hartzel 12v20) thats every 250 hours due to
a recurrent AD. Vibration is not your friend.

--
Frank Stutzman
Bonanza N494B "Hula Girl"
Hood River, OR

Mouser (www.mouser.com), Digi-Key (www.digikey.com) and several electronic
wholesale stores in and around St. Louis sell colored toggle bat caps.
Different colors for different functions. They are about a nickel apiece.

jim



Dave Hyde
shared these priceless pearls of wisdom:

-
-^*&%%*&( Switches:
- I harp and harp and harp about human factors, and then I
- use identical switches throughout the switch panel (in
- my defense I *did* try and space them so that the differences
- would be obvious). I've turned the electrical system off
- at least once thinking I was turning off the fuel pump.
- Now I look. I think I'm going to rotate the FP switch
- so that it's side-to-side throw or put a different bat
- on the master switch. At least it wasn't the mags.



Jim Weir (A&P/IA, CFI, & other good alphabet soup)
VP Eng RST Pres. Cyberchapter EAA Tech. Counselor
http://www.rst-engr.com

"Bill Daniels" wrote in message
news:AuZyc.22988$2i5.20527@attbi_s52...

"Dave Hyde" wrote in message
...
I've had a kind of unnerving vibration in my RV-4 since first
flight. I looked into harmonic dampers, but they're pretty
expensive, so I decided to give dynamic balancing a shot first.
$200 and 1 hour later, my engine runs *much* smoother. It
measured 0.3+ ips on the first run, so the guy weighed and
added an AN-4 bolt, nut, and a few washers to the flywheel.
Next run it was down to 0.05 ips and felt markedly different,
much smoother and quieter. I ran out of time and weather at
the same time, so I haven't flown it yet, but I don't see how
it can't help but be smoother. It remains to be seen whether
or not I'll have the pronounced shake at some power settings
and speeds, but I've also cut back the baffles where metal
rubbed on fiberglass and tightened things under the cowl a bit.
We'll see.

I've had dynamic propeller balancing done on every airplane I've owned.
It's absolutely the best dollars I've ever spent on maintenance. It can
make 4-cylinder engines feel like 6-cylinder.

I feel strongly the money spent is quickly recovered on the things that
don't break because of vibration. Just do it, you'll never regret it.

Bill Daniels


Homebuilders do this themselves with a homemade vibrator and paint. You
slide a flexible wire rod up and down a scale on the device attached to your
aircraft until it vibrates, then balance with paint on the lighter tip. You
find the lighter tip and diminish the vibration by trial and error. Not as
expensive but works. There are drawings and instructions somewhere on the
net, maybe at the Mooney Mite or Culver site.

Jim Weir wrote...

Different colors for different functions.

Color-coded switches don't cut it from a human
factors standpoint. I need something that *feels*
different to a gloved hand. Turning the fuel pump
switch 90 deg will do it, as would a bigger bat. If
I can see the color, I can see whether or not I've got
the right switch, regardless of the color.

Obviously, the interim workaround is to visually verify
any switch before throwing it. Not a big deal in the
short term.

Dave 'tactical tactile' Hyde

"nauga" wrote:


I need something that *feels*
different to a gloved hand. Turning the fuel pump
switch 90 deg will do it, as would a bigger bat.

Dave 'tactical tactile' Hyde


+++++++++++++++++++++++++++++

Max tactile is.....

Going 'gloveless' whether one is stroking
an aircraft or a significant other. g

Barnyard BOb -

Things I'm still working on (that I'd do differently next time):

While I love the AnywhereMap stuff, I don't trust the iPaq
it's installed on. The batteries are ^(*)&. It's wired into
the airplane electrical system, but still needs to charge
in between flights.

Dave 'brain dump' Hyde

RV-4 in flight test, EAA Tech Counselor
++++++++++++++++++++++++++++++++++++++++++

I use a Garmin 295. But, for real details and obstruction info
my Anywhere Map blows Garmin away. [My Ipaq does just
fine plugged into the cigar lighter spot.]

BTW....
If you want greater utility from your Ipaq, consider
'Mapopolis' software for tooling down the highway
of life in your merry Oldsmobile and/or favorite RV.

http://www.mapopolis.com/


Barnyard BOb -

" jls" wrote in message
...

Homebuilders do this themselves with a homemade vibrator and paint. You
slide a flexible wire rod up and down a scale on the device attached to
your
aircraft until it vibrates, then balance with paint on the lighter tip.
You
find the lighter tip and diminish the vibration by trial and error. Not
as
expensive but works. There are drawings and instructions somewhere on
the
net, maybe at the Mooney Mite or Culver site.

I found the article at
http://www.mooneymite.com/articles/f...ncingprops.htm

Rich S.

I've been dynamic prop balancing for 15 years.

0.3 plus a little is not a severe vibration but could be improved.
Many skeptics would call it smooth to begin with.
What was the IPS amplitude of the engine aft,.... or did the operator just
use a single sensor? A sensor on the rear will give you an idea of
crankshaft and rod balance. Lycomings usually are 0.15 to 0.18 the rear.
If it was a custom balanced engine, the rear should run just as fine as the
front.

I'vd balanced some by placing correction weight on a Lycoming ring gear but
have gotten away from that method because it statistically takes far greater
weight per unit of correction. About 30% -50% more than if the correction
weight is placed on the spinner bulkhead, or if the prop's static weights
are adjusted.
Also, the method works less well on props with extensions.

I looked at the mooneymite site. Interesting. The same principle as a
reed tach. Its just a pendulum adjusted to resonance. Insturment face
vibration frequency will be at crankspeed, 1/2 crankspeed or some other
multiple half order.
The author is painting the tips, which will change the spanwise balance but
not chordwise balance.

I don't have the data handy anymore, but as I recall a long ago experiment,
10 square inches of painted tip needed about 11 mils of paint thickness to
weigh one gram. Can't remember what paint Iused, proably Krylon.
On a 76" inch prop, this means a 36 gram-inch balance correction which
will be about a 0.20 IPS.
Actually, one would probably have just as good luck in trial & error by
adding washers under spinner screws systematically. Or if you had some way
to measure engine movement, some sort of overhanging dial indicator, one can
easily find the solution by plotting a 3 way polar chart.

Take Care
Kent Felkins
Tulsa