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Prop Balancing PIREP

jjhoneck

Well Known Member
We flew up to Dallas from the island today, to have the prop balanced on our new (to us) RV-8A, "Amelia".

First, let me say that flying to Dallas, chock to chock, in just two hours, was AMAZING -- but I digress. :D

My first RV-8 ride was in Jay Pratt's amazing aircraft. This plane had an almost turbine-like smoothness that impressed me. When we trained in Amelia, I noticed immediately that she was about as smooth as Atlas, our Piper Pathfinder, (which has been fine for 11 years), but nowhere near as smooth as Pratt's RV.

So, I found Walt's place, EXPAircraft (http://expaircraft.com) here on the Van's RV website. He came highly recommended as one of the best in the prop balancing business. In a previous life, he worked balancing jet engines for the airlines, and his techniques were honed by many years of practice on DC-10s.

Walt is located at Roanoke, TX (52F) a suburb of Dallas. It's an amazingly active little field, with a good on-field restaurant (the Blue Hangar Restaurant), and a full-blown pilot's shop. General Aviation is alive and thriving in the Dallas area, for sure.

The balancing procedure is deceptively simple. Decowl the engine, put a piece of reflective tape on the prop, and mount a laser on the engine.

Then mount a vibration sensor on the engine, outboard. These two different sensors connect to a handheld computer, where the magic happens.

Step One, run the engine up to 2300 RPM. This is the first run, and Walt hangs some weight on the flywheel at the stations prescribed by the magic handheld computer.

Step Two is the second run. Again, I ran it up to 2300 RPM, and it was immediately apparent that something wonderful was happening. Vibration in the stick, and through my butt, was easily halved.

Step Three, again after hanging more weights at the prescribed locations, was the third run, where the balance is fine tuned.

The third run was...amazing. I just sat there, and nothing shook. Like, at all. It was just sound, and no motion. It was truly amazing.

According to Walt the initial run showed my prop at .018. Apparently .02 is the upper limit of vibration recommended, so our prop was close to the max vibration normally seen.

By the third run, Walt had it reduced to .007, close to perfect. It was an amazing change, night and day, really, and I couldn't be happier.

The flight home was remarkable. We climbed to 11,500', in typical RV fashion (quickly), without any vibration at all. It was almost creepy, but wonderful at the same time.

Best $175 I've ever spent on an airplane. Just do it. (And we got to enjoy lunch with Mr. Pratt and Mr. Reeves, too!)
 
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Jay,
Thanks for the report, it's always nice to hear that folks enjoy my efforts to make their ride smoother :D

Just a few minor corrections to your numbers, initial vibration was 0.180 IPS with an upper limit of 0.200 IPS @ 2400 RPM.

Final vibration level came in at an amazing low (lower than most) at 0.007 IPS (Inches Per Second).

RV8%2520Balance%2520jpeg.png.jpg


PS: I'm sure we will see you again as soon as I can get the wife to take few days off to spend at your hotel!
 
Last edited:
Jay,
Thanks for the report, it's always nice to hear that folks enjoy my efforts to make their ride smoother :D

Just a few minor corrections to your numbers, initial vibration was 0.180 IPS with an upper limit of 0.200 IPS @ 2400 RPM.

Final vibration level came in at an amazing low (lower than most) at 0.007 IPS (Inches Per Second).

RV8%2520Balance%2520jpeg.png.jpg


PS: I'm sure we will see you again as soon as I can get the wife to take few days off to spend at your hotel!

Whoops, sorry for the factual errors. My prop balancing technical abilities can be summed up as "Ug. Blue lever push forward, engine no shakey."
:D

Thanks again! It's even more of a joy to fly now!
 
Prop balancing question...

I am looking at getting my plane out of Phase 1 in the next couple of weeks. A few weeks after that my plan was to go into the paint shop. Should I wait for prop balancing till after the plane and spinner have final paint?

Input would be appreciated.
 
Any benefit to do this with a 3blade prop? Also, can it be done if the flywheel is solid and doesn't have any machining holes (Vans flywheel for the IO-540 doesn't come with any machined holes in the fly wheel).
 
Jay, good to c u on VAF and great to c that u bought a RV. We have good memories of staying in your hotel in Iowa before you sold it.
 
Any benefit to do this with a 3blade prop? Also, can it be done if the flywheel is solid and doesn't have any machining holes (Vans flywheel for the IO-540 doesn't come with any machined holes in the fly wheel).

Doesn't matter how may blades it has. The flywheel makes it easy on most lycomings but if they are not available I would mount the balance weights on the spinner bulkhead the same way I do on certified aircraft.
 
I do believe it's the flywheel you add weights as stated in the OP rather than the spinner bulkhead.
 
Do you add the weight to the existing holes in the spinner bulkhead or do you drill new ones where need be?

That depends on your engine/prop combo. On a lycoming if the flywheel bolt hole locations are available that is an approved location to add weights. If those are not available like on the RV12, continental powered aircraft and many other certfied aircraft, then holes are drilled in the spinner bulkhead. If there are existing holes close to the location requiring weight I will try to use those rather than drill new holes.
 
Question for Walt

Walt,

Received my 200RV prop/spinner set from Whirl Wind last week and I noticed it says to have the prop balanced prior to flying (I think that is what is implied anyway). Do I need to have you over prior to first flight or can it wait until later in Phase 1 (I?m located at KDTO)? By the way, the prop and spinner were both painted by Whirl Wind so no additional paint or changes to the system are planned.

Or, do I need to ask Whirl Wind?

Thanks
 
As soon as possible, I will be heading up to Walt's place to get mine balanced! I still owe him some gas money for my fist ride in a RV a couple of years ago!
 
Walt,

Received my 200RV prop/spinner set from Whirl Wind last week and I noticed it says to have the prop balanced prior to flying (I think that is what is implied anyway). Do I need to have you over prior to first flight or can it wait until later in Phase 1 (I?m located at KDTO)? By the way, the prop and spinner were both painted by Whirl Wind so no additional paint or changes to the system are planned.

Or, do I need to ask Whirl Wind?

Thanks

"Assuming" you have a new engine with that new prop, I would recommend getting through the engine break in period (or about 20 hrs) before we balance the prop. We do run the engine pretty hard on the ground during the balance and we don't want to do that on fresh cylinders.
 
Doesn't matter how may blades it has. The flywheel makes it easy on most lycomings but if they are not available I would mount the balance weights on the spinner bulkhead the same way I do on certified aircraft.

Walt,

I'm going to have the -12 up to Grady's for a repaint in October. I would like a new Wt & Balance after the paint job. Also, could you do a prop balance on a Jabiru (the flywheel is on the back of the engine), although it has a wide diameter spinner backing plate behind the prop.

Regards,
 
Walt,

I'm going to have the -12 up to Grady's for a repaint in October. I would like a new Wt & Balance after the paint job. Also, could you do a prop balance on a Jabiru (the flywheel is on the back of the engine), although it has a wide diameter spinner backing plate behind the prop.

Regards,

Haven't done a Jab yet but assuming the spinner/backing plate is similar to the 12 should not be a problem. Getting the fuel out of the 12 to do the W&B is the hardest part so I would recommend bring it in with minimum fuel.
 
Walt Question

Sorry Walt I should have included that information. I do NOT have a new engine. I plan to run it several times prior to first flight.
 
Walt: Does the balance weight location change when balanced at a different rpm? Or is it just the amount of weight that would change when balanced at a different rpm?
 
Walt: Does the balance weight location change when balanced at a different rpm? Or is it just the amount of weight that would change when balanced at a different rpm?

In theory only the amount of the weight should change, but in reality, the location will generally move a little as well.
 
Sorry Walt I should have included that information. I do NOT have a new engine. I plan to run it several times prior to first flight.

If the engine is already broke-in then lets do it whenever you're comfortable bringing it in.
 
What is the preferred balance rpm for a fixed pitch prop?

Being that most fixed pitch props have a max static RPM of around 2200 average that is where I do them, if you can get higher that's great and I will do it at your max static RPM.

I've watched how the balance acts as RPM changes and generally speaking there is very little if any change once you get above 2100-2200 RPM range.
 
Being that most fixed pitch props have a max static RPM of around 2200 average that is where I do them, if you can get higher that's great and I will do it at your max static RPM.

I've watched how the balance acts as RPM changes and generally speaking there is very little if any change once you get above 2100-2200 RPM range.

Thanks Walt, that makes sense.

There seems to be no real standard. I have had a FP prop balanced at 2000 rpm, and last weekend a visiting PHX balancing guy said that wasn't needed and he does it at 1800 rpm...:rolleyes:
 
Smooooooth!

Walt balanced my 7A with the Superior roller lifters a few years ago. Several comments from high-time pilots on it being the smoothest engine they have flown behind.

Walt also made quick work of my recent IFR cert for the upgrade to a dual AHARS and is one of the few people allowed to work on the airplane I put years of my life into.


Andy
RV-7A
McKinney, TX
 
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