Several years ago I had my Three blade McCauley dynamically balanced and the vibrations in the ac went way down; however, a spam can mechanic took off the spinner during an annual but I don't think he marked the orientation and the vibrations returned.

The shop that did the balancing went out of business ( Vietnam vet decided to hunt and fish instead ) and I am looking for a shop to do the balancing again.

Any suggestions in the Puget Sound area? Prices??

Thanx
Tom

If all he did was remove the spinner,and possably put it back on in a different position, why don't you just take it off and put it back on in a different position, I guess you have two other choices and see which one makes it the best.

Good luck Gary

If I was to do it, I would go to Paul Nyenhuis at A.I.R. at Arlington,360-435-4411, a good guy & does a good job. NW Prop also does dynamic balancing.

Eric

You might also mark the spinner temporarily (felt tip that removes easily with alcohol. Then remove it and look for existing index marks. It's very likely you'll find either that the hub is numbered and these numbers are also on the spinner, or there may be a punch mark etc.

I have a prop balancer, though cannot provide balancing services as I'm not an A&P (more importantly, I'm trying to be retired)

I would get it re-balanced, for some reason the balance changes over time anyway, and it can't be too balanced. On new aircraft, we drill a #30 hole in the spinner and through the backing plate to index the spinner, but any kind of index mark will work of course. I re-balance mine after every time I lube it, but I have a balancer.

I switched out the mags on my 175 and it helped the vibration a lot. I was thinking of getting the prop balanced too. What should that cost? Anyone know a good shop around Salt Lake City that can do it? Thanks
Jerry

Tom- I've used NW Propeller, Thun Field, Puyallup. I was pleased with their work!

Shops that balance props generally use a washer or two in the spinner attach screws to change the balance of the assembly. So, it may be that they put the spinner on correctly but left out the washers.

I have used NW Propeller for prop overhauls, and good folks, competitive prices. I'd use them.

Last time I had a prop balanced, it cost about $150. That was shop rate. Sometimes, it takes a while to get it right.

MTV

One other thing some balancers do is put different length screws in the spinner to help or to do a really fine balance job. I put a little model paint on each screw that is not standard and a little by the hole hole where it came from. so it goes back on the same.

GT

Here's a copy/paste of what I wrote last fall about it on the C170 forum:

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I just had mine done back in June at Skinner Aviation in Ashland, OR, and paid about $180. That was the $75/hr shop rate, and it took me and the A&P a little while to dial it in. Engine cowlings must be removed. The Chadwick really helps, but there is some voodoo and luck to it as well. It is a great procedure, both from an operational and preventative standpoint, and it's still worth it even if you have to pay more than that.

Make sure you have a healthy battery. I swear we restarted the engine 20 times, between weight changes based on the Chadwick recommendation.

As for the increase in smoothness before and after, the difference was admittedly difficult to ascertain for me. It seemed a little better. According to the Chadwick, we got it from .36 IPS out at 2000 rpm (.44 at full static!), down to .12 IPS. I was happy with the smoothness before, but wanted the dynamic balance to see if it would actually get smoother. And the benefits of decreased wear on engine internals of course...

I'll mention another tidbit for anyone chasing a prop-related vibration: Double check that your prop is indexed properly to the crankshaft, as some older engines are balanced in this configuration.
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Thanks for the advice Zane. I was looking for instructions on how to index the prop and came upon this:

"Indexing a propeller blade so it leads intake valve timing by a specific amount causes an increase in engine power. The proper indexing allows the high energy propeller wake in the form of an acoustic wave to be ingested by the induction system and arrive at the intake valve just as the valve is opening. When the Wave arrives just as the valve is opening, the wave causes a momentary increase in manifold pressure which adds pumping potential to force additional airflow into the engine cylinders which results in a power increase. This technique called propeller syncro-phasing causes the propeller blade to behave as a "zero stage supercharger."

I guess there is a 33% chance the guys I bought my plane from installed it correctly if it has 6 bolts and 25% if it has 8. I guess the factory knew this and the props were put on to achieve optimum performance, thus indexed in that position. I didn't know anything about this but I wll make sure it is on right before I get it balanced.

I had a quote from a local guy and he wants $250 to do a harmonic balance. A couple of guys told me that was a lot but I want to keep this plane so I want it done right.

You index a prop at the 10 o'clock and 4 o'clock position at shutdown. That is, when you shut it down, the prop blades , viewed from the FRONT should be oriented in the 10 and 4 orientation. That is, of course, for a TWO bladed prop.

The reason for this is so that you can hand prop the engine in the event of a battery failure.

Aviat delivers Huskys with the props indexed at 12/6 from the factory. I've had every one I've flown changed to 10/4. It is VERY difficult and dangerous to hand prop an airplane with the prop oriented any other way.

THEN have it dynamic balanced.

WHen it comes to dynamic balance, by the way, it isn't necessarily the vibrations that you FEEL in the airframe that are the most destructive. In fact, third and fourth order harmonics are some of the most destructive vibration events, and THAT is what the dynamic balance does. So, even if your engine/prop FEEL pretty smooth, a dynamic balance makes a lot of sense.

IT will save a lot of cowl cracking, fastener working, etc, etc.

MTV

I emailed Hartzel and a guy called me back. He said they suggest that the prop be installed with one of the blades placed as close to the "0" Timing Mark on the Flywheel as possible.

Jerry

I have Todd @ Jackson Hole Aviation balance mine. He uses the ACES unit, is very meticules,sp and to dial it in perfectly he will split weight it. The average price usually runs around 200 or so. If you are in the SLC area, JAC is 1.3 hours away and a nice flight. No matter where you go pick a day with calm winds, any breeze at all will degrade the balancing no matter which unit you use. PM me if ya need more info.

Ben.
www.haaspowerair.com

Thanks Ben, Was your plane noticeably smoother after the Balance?

Jaerl wrote:Thanks Ben, Was your plane noticeably smoother after the Balance?

I do ALOT of testing by switching from the Ivo magnum high speed blades to the big paddle blades designed for back country flying so on every blade change I balance them. Altho I am a bit anal on getting things perfect too. Any change usually starts out in the .15IPS range and usually we can get it down to .05 or better. So the answer to your queastion is,, a resounding yes, I can feel the difference for sure. As a side note I do balance them from time to time when it starts to feel rough because I run the carbon fiber blades and for some strange reason they will change balance. The jury is still out on whether the molicules move around, the blades themselves shift just slightly in the hub, a full moon, global warming, Dems in the whitehouse, whatever etc, they will get out of balance all by themselves. I do have a hangar mate that built a RV-6 and his plane has a persistant shake to it from the beginning. I did a little research on the net and found out all he needed to do was reclock his prop 60 ` or one bolt hole. His is perfectly smooth now just by doing that.

Got the prop balanced at Northwest Propeller in Puyallup last Fall and it smoothed right out. Would recommend them.

Took about four iterations to dial it in but was worth it.

The proper weights seem to work better than a slug of washers.

TD

There is propeller balancing and then there is propeller balancing. JF Dynamics at El Monte airport CA. (Jim Fackler) I think I have it right. Literally wrote the rules for the FAA.
A good tech can tell you if there internal balance problems or help balance them out by offsetting them at the prop. If you only balance, or check for balance at the front of the engine you may over look or make a balance issue worse at the rear of the engine.

172heavy wrote:There is propeller balancing and then there is propeller balancing. JF Dynamics at El Monte airport CA. (Jim Fackler) I think I have it right. Literally wrote the rules for the FAA.
A good tech can tell you if there internal balance problems or help balance them out by offsetting them at the prop. If you only balance, or check for balance at the front of the engine you may over look or make a balance issue worse at the rear of the engine.

In most every case, assuming there is not mechanical problem with the engine, the prop is balanced by installing the accelerometer at or near the front of the engine case. I've balanced a number of propellers, and it's rare indeed that I don't see final figures of at or below .05 ips.

That said, on one occassion, I could not get a O-470 to smooth out. Turned out one of the rear jugs had a botched weld repair to the head that was substantially increasing compression. I also installed a second accelerometer on an engine while balancing a drive shaft driven Stemme S10-VT. This had nothing to do with the prop itself (it balanced reasonably well), but it did point out an imbalace in the centrifugal clutch mounted to the front of the Rotax 914.

There's nothing magical about propeller balancing. Adjustments are made by adding weight to balance first order frequency (rpm) caused by an imbalance in the rotating mass of the prop/spinner/etc.. If there are strong vibrations occuring at other harmonics (and there will always be some weaker spikes on a frequency spectral analysis), then that is indicative of other problems, engine internals, bad shock mounts, broken engine mounts etc.

I took Ben's advice and took my 175 up to Jackson Hole to have it balanced. I need to give Todd at Jackson Hole Aviation a plug here. He balanced my prop a few weeks ago and the guy is great! He said mine was the second worst plane he had ever seen (.64 IPS). Todd stuck with it for about 5.5 hrs and he just won't give up till it's right. He gave me a break on the price since it took so long and finally got it to .04 IPS.

Zane said, "As for the increase in smoothness before and after, the difference was admittedly difficult to ascertain for me." At first I wasn't able to tell how much it helped mostly because I flew home on the nose of a storm and I was beat up all the way home by turbulence. I could tell a difference on climb out but at cruise it didn't seem too much different. I took it out the other day when it was smooth air and it is noticeable better.

One thing I noticed right off is my cowling is rock steady now. The 175's have a "floating" Cowl that actually mounts to the motor mounts and not the fuselage. Before the balance job the cowl would vibrate too. Now the prop and engine are balanced together and hopefully that will reduce bearing wear over time. Just another expense you don't count on but I am glad I did it and Todd is a great guy if any of you guys are considering having it done. Plus flying over the Tetons was great too!