Engine Vibration

[azevedoflyer]

Guys,
When I bought my Pacer 4 years ago, the engine (O-320 150 hp) had 460h after a major overhaul. One cylinder (maybe number 1) was substituted by a yellow-tagged part, as the head had a hairline crack to it. A brand new piston, rings and piston pin went in with jug change. All other jugs have a yellow strip but this one has a green strip. This means something, I remember, but what I do not know. The prop was statically balanced some 2 years ago but has been subsequently removed and installed a number of times. My previous flying experience was in Cessnas (172/152). All of this as a preamble to my statement that I think my engine vibrates way too much. New rubber mounts actually aggravated this perception as the old ones were sagged and mushy, perhaps less hard and actually doing a better job of dampening vibration! The engine works like a clock. Never misses a beat, consumes oil at < 2 qt/25h, burns really good. I also developed a system that measures the "health" of the PCU (power cylinder unit - piston/rings/cylinder)by sensing the blowby gases and it tells me the engine is very healthy inside.
However, I still think it should vibrate less, but lack a reference to judge by...
Any thoughts on the matter by anyone? :roll:
Thanks,
Miguel
N8714D

[Hillbilly]

I dont know how much lighter it will be but youve got 3 .020 over cylinders and one .010, that could easily be a contributing factor, plus its probably not good for the crankshaft.

Lycoming uses the following color codes:
Orange - chrome barrel
Blue - nitride hardened steel barrel
White - rebarrel
Green - Plus .010 oversize barrel
Yellow -Plus .020 oversize barrel


Hope this helps-Hillbilly

[Steve Pierce]

Hillbilly, I didn't know about the green and yellow bands.

Miguel, I have never had an engine shake because of a low cylinder and I have found some in the 20/80s. Most of the vibrations I have seen are from the prop or prop indexing. My Dad and I recently swapped props. He noticed more vibration and I lost the vibration. Had Jim Fixx overhaul my prop and it is now smooth. I flew a Clipper back from WA once and it seemed to shake more than normal. I noticed when I shut it down the prop would stop at the 3 & 9 o'clock position. I re-indexed it to 1 & 7 o'clock and it smoothed out. I have done the same on several other airplanes. I have never seen a Piper document saying where to index the prop but have found it in Cessna manuals.

[Hillbilly]

I have no idea the difference in weight between a piston and one thats .010 larger or smaller, since my post Ive thought about it and the difference has GOT to be very small, Steve is the expert here if he thinks its prop indexing it probably is...
-Hillbilly

[Steve Pierce]

I didn't think about the weight difference. That could cause a vibration. Seems I remember reading a piston weight difference speck on some engines.

[Hillbilly]

I have never seen a Piper document saying where to index the prop but have found it in Cessna manuals.

I recall somewhere a Cherokee 180 manual that says 2and 8 o'clock (1 and 7 could be the same depending on the engine and viewing perspective)

[Hillbilly]

I didn't think about the weight difference. That could cause a vibration. Seems I remember reading a piston weight difference speck on some engines.

Course its not very relevant but I used to fool with some old German built V6 engines that were balanced with varying weight pistons, not really a problem till some unsuspecting schmoo started changing pistons... that thing would run like a magic fingers vibrating bed...

[Bultaco Jim]

Steve, I did see a prop indexing blurb on Pipers somewhere recently. Found it on the internet. Now you're going to make me start searching for it. Jim

[Bultaco Jim]

Hey, that did't take long.... I found the indexing info in the SWPC useful info. Here it is.

Propeller Installation on ShortWingPipers

Remove #1 spark plug. Rotate crankshaft till pressure begins to build
(place thumb in spark plug hole to feel/hear pressure building).
You are coming up on TDC for #1 cylinder. Continue rotating crankshaft
until #1 piston is TDC (use timing mark on back of ring gear aligned
with crankcase split or use markings on front of ring gear aligned
with punched hole in starter housing).

With #1 cylinder on TDC, the prop should be installed such that it is
Horizontal, ie level to the ground.

There should be a small "no 1" stamped near the hub on one prop blade.
That blade goes "over"/"toward" the No. 1 cylinder. It is permissible
to install the prop "180° out", but only as a "fix" for a SLIGHT vibration
at cruise. Nine times out of ten, it will NOT be an issue. Torque prop
correctly (visit Sensenich's website for detailed instructions or see pdf
file on this site) and safetie prop bolts, reinstall spinner and spark plug.
Button up airplane. Your prop will now be in the PROPER position not only
for handpropping, but more importantly will also be "timed" to best act as
a "flywheel" with the crankshaft.

Don't forget that this is not Preventative Maintenance, and requires
a Logbook entry by an appropriately rated Mechanic.

[Bultaco Jim]

After reading this info again, I realized that one of my planes didn't have a "number 1" stamped on it. However, I read, (just tonight), that it is the same side as the stamped serial number on the prop. Hope this helps. Jim

[taildraggerpilot]

Before you index anything, I would track the prop to see if your crank shaft flange is bent or at least help you determine if you have a blade out of track.

[JohnW]

Wow. That indexing "tutorial" sounds VERY familiar to me! Wonder who penned that?

Jim, you found that WHERE exactly? Would it be a good guess that you got that over on Andy's website? :lol:

[Bultaco Jim]

Yes, JW that's exactly where I saw it. I probably first saw it 2 years ago. Maybe I'm missing something ?..... The main thing is to NOT put the prop in any of the other positions (besides 180 degrees out) because the crank won't like it.

[azevedoflyer]

To all that pitched-in:
First, many thanks!
Second: I was checking the cylinder color strips and found that I misled you all.
The truth: cyl.1 /2 and 4 have a green strip, meaning they are 0.010" oversize. Cyl.3 has a yellow strip, meaning it is 0.020" over. Took the time and calculated inertia loads. At 2600 rpm, unbalanced force is 131 N at 0 deg. (TDC) and -68 N at 180 deg. (BDC). Hardly noticeable or a root cause for severe vibration. Under actual firing conditions, these numbers would be smaller.
The shaking around a a vertical axis due to unbalanced moments may or may not be countered by prop position, as pointed out by many of you. Convinced by my own numbers, time to talk to someone that makes a living out of repairing planes. This highly respected guy said the same that one of you pointed out earlier: vibration due to mismatched pistons is a lesser factor compared to vibrations triggered by a unbalanced prop. Does make sense. But my prop is properly balanced/tracked. He then hit upon proper prop positioning and said that O-320s need to have the prop positioned at 2 - 8 o'clock, as viewed from the front of the plane. We went to the shop and he showed me how it should look.
Mr. Bultaco Jim (Off-road Spanish bikes, famous for their powerful 2 strokes!) posted that prop should be positioned horizontal, with cyl.1 at TDC.
Would anyone pitch-in and be the judge?
Cheers,
:P Miguel
N8714D

[Steve Pierce]

2/8 as viewed from the pilots seat.

[Hillbilly]

2/8 as viewed from the pilots seat.

I concur.

[Jim]

Hi,

My old 290 had a lot of vibration too, always cracking something every annual. I broke baffling, oil cooler mounts, exhaust, cowling, and even a tube on the rear of the engine mount. The prop checked good in balance, tracking and pitch. The spinner being on or off didn't make a difference either. Never did find out for sure, but when the engine was disassembled after a prop strike we found that one of the pistons was a totally different casting than the other three. We didn't weigh the differences, but there was no way they could have been the same throughout the engine.

Any chance you can review what's been installed in yours over the years?

If you can't nail it down you might consider having your moving parts dynamical balanced. Around here they'll nick you for about $150 for the service.


---==X={}=X==---

[azevedoflyer]

:? Jim and All,
Mine seems to be a similar case to yours.
My engine has cyls. 1/2/4 0.010" over (green), while cyl. 3 is 0.020" (yellow) over.
This results in a negligible (0.013 N.m) static unbalance, right side heavy.
After Lycoming answered my request about conrod L (6.500 in - center-to-center), I recalculated forces at 2600 rpm for unbalanced moments. At TDC (0 deg.) the unbalanced force is 129.3 N (29 lb) twisting the engine on its plane counterclockwise (to the left of pilot). At BDC (180 deg.), the unbalanced force is -70 N (-15.7 lb) trying to twist the engine clockwise (to the right of pilot). I do not know design details of the engine like cylinder and main bearing spacing to calculate moments. However, the resultant unbalanced moments will exert themselves at app. 87 Hz. The artificial horizon indicates that a beating phenomena occurs, as the back oscillates at regular intervals. Anyway, my point is that I am considering buying a yellow tagged cylinder that is also green and substituting the 0.020" over that I have for cyl3. For those experienced, any recommendations if this advisable and where to buy such thing? Barrels are plain steel, this much I know...
Thanks,
Miguel Azevedo
N8714D
PA22/20-150

[Jim]

Hi again Miguel,

My pistons were a lot more different than a boring would have accounted for. I have this old picture that sort of shows what one of them looked like compared to the other three. Notice where the wrist pin goes through the piston, that's where the other pistons didn't have semi circular reliefs cut in their sides. The others were cut out coast to coast like the red lines indicate. You can also see the different expansion slot locations between the pistons.

[JohnW]

To avoid any misunderstanding, I want to point out that the "2/8" o'clock positioning reference is exactly the same as the "No.1 blade over TDC on cyl no.1" reference. The "2/8" is in regards to where the prop stops on a normal engine shutdown (viewed from the Master's Chair). "At rest, unmolested by human hand", so to speak. As any one of the cylinders (talking four cylinder, horizontally opposed here) slows down when the engine winds to a stop, the "last cylinder" that approaches TDC (on compression stroke) is going too slowly to go past the "squeezing" of the piston moving "upwards". This causes the prop to come to it's "stop" and then it will "back up" some due to the pressure in that cylinder. Everyone has noticed that the prop goes "back and forth" (to varying degree on different engines) a couple times as the engine stops spinning. THAT results in the [two-bladed] prop always stopping in the 2/8 o'clock position.

I appreciate that this is somewhat "elementary" to a lot of people and I don't wish to be thought of as lacking the ability to "delete the obvious", but I have found that even relatively "more mechanically inclined than the Average Bear" types will somehow overlook the part about "...on NORMAL SHUTDOWN...". Trying to install a prop onto an engine with the prop at 2/8 is useless unless that engine's crankshaft is turned BACK FROM TDC the corresponding amount (sixty degrees, technically). Putting the prop No. 1 blade horizontally onto the flange over No.1 cylinder at TDC accomplishes all of that first time, every time. THEN if you have a slight vibration, you can turn the prop 180 degrees if desired, and at least you started from the same place, every time.

Surely, putting the "same bore diameter" and "type" pistons at each location is inarguably the best practice regarding "power pulse induced" vibration in ANY kind of recip. But it is universally "accepted" practice in a/c engines to use a .010" over [the others] cylinder in ONE location (but not MY practice, and definitely not in MY engine, Thank You Very Much!). There ARE other "considerations", tho'! Cold versus Hot compression checks (aka: MotoStats, Nort' of the Border) speak a lot towards total cylinder condition. 'Just cold" or "just hot" checks are less than HALF the story. A warped (or improperly adjusted) valve, or carbon flakes where a valve closes on the seat can also be a source of "nuisance" vibration. A "weak lifter" (hydraulic) can drive ya crazy in what is otherwise apparently a "healthy engine". Even intake "rubbers" (altho' these usually affect LOW SPEED operation). Man, even a plug that breaks down under load can be felt, altho' not always "identified" until replaced. ESPECIALLY if engine mount rubbers are old (hardened) or even new, if installed too tightly. The "check runout" suggestion would be the fir$t place to look and the best thing to eliminate. Oh Dear! So much to know! I'm going to kill me! (Just kidding, Folks)

And finally, "where to GET such a yellow-tagged cylinder" of a particular oversize? Jeez, all you can do is "let your fingers to the walkin'" and find who that overhauls cylinders HAS ONE. (don't overlook JILCO -dba Preffered Airparts- in Kidron, Ohio. 800-433-0814. "Nate" is their go-to cylinder guy. I'd try there first, and their Website cannot keep up with their daily stock, so CALL to get minute-to-minute information. Don't be put off by the "Jesus Is Lord" part, these guys are the real McCoy)

One last thought...I presume you are aware of the "Do not operate" requirements of a certain PA-22 engine/prop combo? (There he goes with the OBVIOUS again!)

[Hillbilly]

My understanding was the prop indexing was to position the prop so it best acts as a flywheel for the engine. I found some rather interesting info to this regard that possibly dismisses the 2/8 theory as that is, if I'm not mistaken, the best position for hand propping.

"The following is from the Sky Ranch Engineering Manual written by John
Schwaner.
Page 436, chapter 11 entitled "forces, vibration and Balance."
"With four-cylinder engines the propeller can be indexed so the blade
center lines are contained in the plane of the crank pins. This means that
the propeller blades are horizontal when any cylinder is at the top of the
compression stroke. This is the point of minimum crankshaft rotation
inertia. Historically, propellers are indexed 60 degrees ahead of
horizontal so the propeller is in a convenient position for hand propping.
However, if you do not intend to hand-prop the engine, this index
configuration will minimize transmitted vibration levels."
This book is a very good reference manual for anyone who wants to know
more"

[azevedoflyer]

:roll: Jim / John and Hillbilly,
Thanks for your consideration!
Let's confess upfront that I'm just comfortable with math, physics and engines in general, without much in terms of specifics.
Thus, John, I have no idea of what you meant by "do not operate" related to a certain PA22 engine and prop combo!Maybe a certain rpm range and prop design that excites dangerous crank frequencies? Or prop flies apart if operated at a certain rpm?
If at all possible, please educate me or point to where I should go. I'm also endowed with unsatiable curiosity...
For the record, my engine is a O-320 A2B (low compression) and coupled with a Sensenich 74DM-O-60.
Jim: was your engine a "shaky-Lyc" too?
I would be frightened to death upon opening an engine and finding what you found...However, appearances matter not if the system is "balanced" and pistons are FAA/PMA certified. I have a definite preference for forged pistons as supplied by Metal Leve, out of Brazil.
Hillbilly: thanks for your digging of information on the subject. It seems that your last piece supports John's teachings. After much travail, I'm in the enviable position of not needing to prop my engine anymore (another story to be told!). So, with John and Schwanner endorsing number 1 on TDC (compression), prop horizontal and a convincing argument (all cyls. aligned at TDC), I have my job cut for me. Will give it a try and let you know later.
Thanks to you all.
Have a nice weekend.
Miguel
PA22/20-150

[Jim]

Hi again Miguel,

........Jim: was your engine a "shaky-Lyc" too?

Yep, I mentiond that in about the middle of page two on this thread.

[JohnW]

Hello, Miguel. I have a clear recollection of "mid-year" PA-22-150 airplanes (oh, 1956 to 1958 or somewhere in that range) with inst panel placards stating "Avoid Continuous Operation between 2150 and 2350 RPM". Certain similar year PA-18s carried that placard as well, as I recall. I also have a somewhat less positively reinforced recollection of that same requirenent being found in the "Data Pertinent to All Models" (or possibly "Required Placards") section of TCDS 1A6. As sometimes happens, it appears that I may have "stepped in it", proving the age-old addage that "a little bit of knowlege is a dangerous thing". I should have done what I normally do when this sort of thing "pops into my head", as I TRY to maintain a position of only saying things I KNOW are true rather than having to defend things that I THINK are true (unless I specifically include the words "I think" or some such similar disclaimer)! I should have done the legwork BEFORE I blurted out what I THOUGHT I knew. Dad-burn it.

While I am sufficiently [self-] convinced that "certain engine/prop combinations" on PA-22s did indeed once have that requirement, I have frittered away several hours now trying to lay hands on the supporting documentation! Without success. I am also POSITIVE that I have an "archived" panel stashed around here somewhere that I "set aside" because of the excessive amount of cracking all over this particular panel, it was quicker, easier and less expensive to just have replaced it when the airplane was restored, rather than patch it. Can't put my hands on it. Close as I can come to this "RPM Limitation" thing is a P.A.C. Service Letter (No. 259 30Nov1955) that obsoleted the "Avoid Continuous Op ON GROUND Between 2050 and 2250 RPM". I wish I had copies of the AFM for one of those airplanes, but I sure don't. So right there is the "final answer", by golly. If your Aircraft Flight Manual is the correct one for your ser. no. airplane and it does NOT contain such a requirement, I'm off the hook on backing up what I said. The proper AFM is the Final Authority for such things. Much as I hate being "wrong", I 'll be the first to say it when I can't prove differently, and I can fall back on the fact that I have "blown the whistle" on myself before. Only people that don't EVER make a mistake are those that do not participate.

Here is what you can do, empirically...go to a hardware store and buy a 8" to 12" length of "sink-stopper chain". That's the stuff (also used for porcelain light socket "pulls") that looks like tiny balls held together with a short piece of thin wire. Hang it from one of the diagonals (duct tape?) and go flying. There is no better [Farmer] indicator for "how much vibration" you have at different throttle settings

Unless someone can "help out" with something defending my claim, I have to backpedal at this time and state that I can NOT find the documentation that I recall. In my defense, I will say that several things have unquestionably "dissappeared" over the years from TCDSs (applicable starter, generator and other "accessories" for specific models on engine TCDS is a prime example). Quite possibly there WERE such limitations and extended research proved them superfluous and they were removed. The gnd op placard would be such an example, as well.

Now, I will add this: Anyone with an O-360 installation on their ShortWing (or any OTHER Type for that matter) should be aware of the existence of A.D. 69-09-03 R3, just to be sure they are not "missing an A.D." That's an easy one to "overlook" as all A.D. search engines to not make the "hit".

[Tom T.]

John, I too can recall such a placard in a tripacer I flew as a stufent pilot! But, I do not recall what it was there for.

[azevedoflyer]

John,
Many thanks for the time and patience!
I will, indeed, buy the ballstring and hang it there, if nothing else to amuse myself!
I've told you: I'm curious by nature...
Whatever documentation I have I'm sure does not mention any limitations, as I have read it forward and back many times.
But do I have all pertinent info? I doubt it...
Will beat the bushes and see what I can find and share.
Cheers,
Miguel

PS: flew the bird yesterday and found that vibration is a lot less at 2100 rpm. As these things go up and down with the square of the engine speed, it is to be expected. What was interesting was the noticeable difference between 2200 rpm and 2100 rpm!
Huuuuummmmmm..... :?

[pacerman]

I used to have a Cherokee 180B with the O-360 Lyc. It had a red line on the tach from about 2200 to 2400 rpm. I remembered there was a problem with harmonics at this rpm but could remember the documentation that required the tach to be marked.

I found the following quote on another Piper board:

"The limitation was due to resonance created by the combination of the Sensinich EMM60 series propellers and the Lycoming engines with hollow crankshafts. If you had an engine with the solid crankshaft, you were not affected by this limitation.

The limitation may be missing from earlier TCDS's because it first appeared as an AD in 1967 (I think, not sure of the year). Look up the info on youe engine to determine if you have the hollow crankshaft. It is usually determined by the suffix of the engine model. The A3x engines were hollow crankshafts and the A4x engine were solid. For example, my PA28-180D has the O-360-A4A engine which is not effected by the AD."

I don't know if any O-320s or other size Lycs are affected by this problem. Having said that, the mechanic who is just finishing the bottom end repairs on by Vagabond with Cont. 65hp called today and said the engine runs fine but there is a little more vibration than he would like if it were his plane. I'll check it out for myself. The prop (wooden) was refurbished (crushed hub by some previous gorilla mechanic) last year. It might need to be dynamically balanced I guess.

Joe

[pa20]

Propeller Installation on ShortWingPipers

Remove #1 spark plug. Rotate crankshaft till pressure begins to build
(place thumb in spark plug hole to feel/hear pressure building).
You are coming up on TDC for #1 cylinder. Continue rotating crankshaft
until #1 piston is TDC (use timing mark on back of ring gear aligned
with crankcase split or use markings on front of ring gear aligned
with punched hole in starter housing).

With #1 cylinder on TDC, the prop should be installed such that it is
Horizontal, ie level to the ground.

There should be a small "no 1" stamped near the hub on one prop blade.
That blade goes "over"/"toward" the No. 1 cylinder. It is permissible
to install the prop "180° out", but only as a "fix" for a SLIGHT vibration
at cruise. Nine times out of ten, it will NOT be an issue. Torque prop
correctly (visit Sensenich's website for detailed instructions or see pdf
file on this site) and safetie prop bolts, reinstall spinner and spark plug.
Button up airplane. Your prop will now be in the PROPER position not only
for handpropping, but more importantly will also be "timed" to best act as
a "flywheel" with the crankshaft.


I will ask for everyone's patience for re-opening this thread from long ago regarding the proper method for installing the prop. The text contained in the above post by Bultaco Jim was taken from the SWPC website, and is verbatim to the directions from Sensenich. (Note: It is listed under the installation instructions - Aluminum Prop - Experimental aircraft. The instructions for a certificated aircraft state to consult the manufacturer's specs, which gets us nowhere with a SWPC as it is not listed.)
I have never gone through the process as described, as I indexed my prop using felt pen lines years ago, and always put it back in the same location, which resulted in the "2&8" that Steve and other have mentioned. I discovered the installation instructions on the Sensenich site a month or so ago, and further research located this thread, so I went with it when I reinstalled the prop a few days ago.
My prop used to stop in the "2&8' position, but now stops more closely to 12 & 6. I can tell that the prop is now one lug off on the crank flange. The impulse used to fire at approx. the 7 o'clock position, but of course now fires at the 9 o'clock position as viewed from the front. During my test flight today, there seemed to be a low freq vibration, with a amplitude closely matching the RPM of the engine.
I really don't like what I am seeing (and feeling) now, having used the Sensenich/SWPC directions. Moving the prop 180 degrees is the alternate method called out in the instructions, but that is not going to solve the "clocking" problem.
I am pondering moving the prop 1 lug to get it closer to the 2&8 (10&4 viewed from the front).

[JohnW]

I would not for a second intimate that Bultaco Jim "plagiarized" that quote (Jim was -and I presume "is, still" a straight-shooting Dude, a Gentleman and a scholar- and I don't particularly CARE about "credit where credit is due"!) but the text you have C&P'd was authored in that Thread by me. I don't particularly give a hoot HOW that was attributed to Jim -perhaps he either "quoted" my Post, or C&P'd it himself- but you are right about one thing... yes, that IS very much the same as Sensenich's Posted information. But, anyone who has read any number of "my Posts" can see and immediately recognize the use of quotation marks, "slashed" word combinations, and several other telltale indicators, that this, beyond pure speculation, is MY "work". Thanks for the left-handed compliment. I appreciate it.

"The proof is in the pudding". The following was stated (again, by me) somewhere slightly subsequent to the quote you have provided and in that same thread, and is another salient point which you may be overlooking. That is, when (if?) you hand-prop your "flat four" Lycoming, you will find that unless you mount your prop as described, that the cylinder fires at the WRONG PLACE. Never mind that the mass of the "flywheel" dampens the vibrations generated by the power impulse, when the prop installed as described above...if it is indexed one hole (sixty degrees) FORWARD of cylinder TDC, the prop is indeed at the approximate 7:00 position. Woo, boy! The "propper" is at this point bent forward at the waist, head low...any slip or missed balance and he is in the DANGER ZONE. Even with only a HALF-stumble forward, this could get fugly, and QUICK. You do NOT want to be in this position! As the Red Queen said..."OFF WITH HIS HEAD!!!". If the prop is indexed sixty degrees LATE, the propmeister must stand WAY TOO CLOSE to the prop arc, because the "throw" is well over his head, and he has to "stretch" to effect it. The places the lower body in severe jeopardy of inadvertently getting into the prop arc when the engine fires. Just try it...stand upright, stretch your hands into the air, look down at your foot and simply lift your leg; notice that you knee just protruded FORWARD in unGodly amount. I don't mean to sound TOO GRAPHIC, but what will likely happen under these conditions is that when the engine fires, the prop will deliver a descending blow to the thus exposed knee/thigh. You will be spun around "in place", off balance, and get "sucked" ("fall" is a more appropriate word, but the common usage phrase afterward would be "he was sucked into the prop") into the arc, and the Red Queen makes her debut again. Any number or combination of amputations of various and sundry limbs could be expected, even if you noggin remains in place. (I do not consider this "funny".)

The "alternate method" to which you refer to has to deal with minor engine vibrations. Many times in my life around "bugsmashers", I have heard the complaint that "I have a teeny-tiny vibration in cruise and it's probably nothing, but it bugs me; can you do something about that?". Yeah, usually. Sensenich "identified" one blade as No.1, There is nothing dramatic about this...it is simply a REFERENCE. Engines themselves inherently run quite smoothly, as does a prop...IF each is quite closely balanced "circumferentially". It IS possible, however to "mate" a slightly heavy point of a prop IN LINE WITH the slightly heavy point of an engine. This would be the infamous "tolerance stackup". Usually, the referenced "slight vibration" can be eliminated by simply "flipping the blade over" 180 degrees. This is akin to properly installing your tubes and tires on your wheels in the prescribed manner and avoiding a "wheel shake" after you take off. These too are indexed as to their heavy spot, and you mitigate wheel shake but putting the dots in line with the "light spot" where the nipple hole has lightened the wheel, itself. In most cases, a "bugsmasher" will not require additional wheel weights to perform satisfactory.

All of which leaves a little room for the reader to "fill in the blanks".

[pa20]

I would not for a second intimate that Bultaco Jim "plagiarized" that quote (Jim was -and I presume "is, still" a straight-shooting Dude, a Gentleman and a scholar- and I don't particularly CARE about "credit where credit is due"!) but the text you have C&P'd was authored in that Thread by me. I don't particularly give a hoot HOW that was attributed to Jim -perhaps he either "quoted" my Post, or C&P'd it himself- but you are right about one thing... yes, that IS very much the same as Sensenich's Posted information. But, anyone who has read any number of "my Posts" can see and immediately recognize the use of quotation marks, "slashed" word combinations, and several other telltale indicators, that this, beyond pure speculation, is MY "work". Thanks for the left-handed compliment. I appreciate it.


John,
The text I quoted was from Bultaco's post #9. The text he quoted was credited by him to the SWPC, and I am sure that the SWPC credits Sensenich. I was not aware that you authored publications for Sensenich, and were the original author.

Thanks for the rest of the lecture on hand propping, etc. I got all that, and that is one of my concerns having reclocked my prop.

[Steve Pierce]

My experience has been they are way smoother when clocked at 2&8 on multiple airplanes. Cessna 100 Series Service Manual gives the 2&8 info. Never seen anything from Piper.

[pa20]

Steve,
After flying it the other way, I am in complete agreement. Heading out to do the work as I speak. Thanks for the input!

[Larry2011]

To Mark O.

Did you ever find the correct length for the prop bolts? If so, which are they?

Thanks,

Larry

[pa20]

Larry,
I ordered a bolt kit from Sensenich. I did the research on the Sensenich web site and then called the company to verify my order was correct. They shipped it out that afternoon, and I had them within 4 days.
i am not currently at home, but if you would like i can look for the kit number when I return.

To Mark O.

Did you ever find the correct length for the prop bolts? If so, which are they?

Thanks,

Larry

[pa20]

My experience has been they are way smoother when clocked at 2&8 on multiple airplanes. Cessna 100 Series Service Manual gives the 2&8 info. Never seen anything from Piper.
Haven't flown 44K much, and finally got around to reindexing the prop back to the orientation as Steve stated above. What a HUGE difference! The plane got about 10 hours with the prop clocked IAW with the Sensenich instructions, and it was not happy (neither was I for that matter).
Of course it was running better because I had just changed oil, too. Don't our engines always seem to run better on fresh oil??

[andya]

yeh, just like they are faster after a wash and polish.......



Haven't flown 44K much, and finally got around to reindexing the prop back to the orientation as Steve stated above. What a HUGE difference! The plane got about 10 hours with the prop clocked IAW with the Sensenich instructions, and it was not happy (neither was I for that matter).
Of course it was running better because I had just changed oil, too. Don't our engines always seem to run better on fresh oil??

[pa20]

yeh, just like they are faster after a wash and polish.......

Mine does!! :-) My research indicates that speed is inversely proportional to the depth of bugs and mud!

[Pacer 24C]

Have both a 0320 and a 0290D2 I have found the biggest balance problems have been with the starter flywheel - if the prop is well balanced - I use a static balancer to check the flywheel - then If still not satisfied - go with the Vibralux Dynamic Balance.

[pa20]

Dynamic balancing tomorrow. Will report back the findings.

Have both a 0320 and a 0290D2 I have found the biggest balance problems have been with the starter flywheel - if the prop is well balanced - I use a static balancer to check the flywheel - then If still not satisfied - go with the Vibralux Dynamic Balance.

[pa20]

Dynamic balancing tomorrow. Will report back the findings.

Dynamic balancing revealed that I was in the "very good" range already. Added one 3/16" large area washer (AN-?...i should know this), and that brought it into the "excellent" range.
I discovered (reaffirmed) that I have a harmonic vibration the occurs in the 2100-2250 RPM range. Totally smooth above and below those RPM's. Logical thinking would seem to be that this is due to the prop not being clocked IAW Sensenich specs, but it occurred when I had it there, too. Not sure what (if anything) could be done about that.

[pmanton]

What is the best position to clock or index a propeller for hand propping? If you can give me the prop referenced to the engine at TDC #1 I’d be as happy as a pig in mud.

Thanks

Paul

[Steve Pierce]

1 and 7 o'clock from the pilot seat.
http://www.shortwingpipers.org/forum/showthread.php?4534-Engine-Vibration&highlight=indexing

[Chris Iriarte]

Has anyone indexed their prop ala Schwaner? If so, any improvement noticed?

Chris


My understanding was the prop indexing was to position the prop so it best acts as a flywheel for the engine. I found some rather interesting info to this regard that possibly dismisses the 2/8 theory as that is, if I'm not mistaken, the best position for hand propping.

"The following is from the Sky Ranch Engineering Manual written by John
Schwaner.
Page 436, chapter 11 entitled "forces, vibration and Balance."
"With four-cylinder engines the propeller can be indexed so the blade
center lines are contained in the plane of the crank pins. This means that
the propeller blades are horizontal when any cylinder is at the top of the
compression stroke. This is the point of minimum crankshaft rotation
inertia. Historically, propellers are indexed 60 degrees ahead of
horizontal so the propeller is in a convenient position for hand propping.
However, if you do not intend to hand-prop the engine, this index
configuration will minimize transmitted vibration levels."
This book is a very good reference manual for anyone who wants to know
more"

[pa20]

Has anyone indexed their prop ala Schwaner? If so, any improvement noticed?
"With four-cylinder engines the propeller can be indexed so the blade
center lines are contained in the plane of the crank pins. This means that
the propeller blades are horizontal when any cylinder is at the top of the
compression stroke.
Chris

Yes, I have done it. Read the Sensenich instructions for installation and it called for clocking the prop with the #1 blade aligned with Cyl #1 when at TDC. Complied with that procedure, and flew it that way for about 25 hours. Significant vibration! Reindexed the prop back to what it had been for years (as Steve stated above), much smoother.
I knew John Schwaner, and he had forgotten more than I will ever know. But, my practical experience (and that of others) in this situation, indicated that it was not correct.

[AKJurnee]

I read someplace to index the propeller so that one blade will be swinging in front of the air box just as one of the intake valves open, as to try and extract any impulse of air. Not sure how in real world operation would we see any results, may be from an air racer theory. Interesting theory.

[Chris Iriarte]

Thanks Mark ... just the feedback I was looking for!

As far as timing with the intake opening, I would think the convoluted intake stream plus a giant sponge in front of the carb would negate any gains! Maybe it would work in a Mooney with the little "direct to the intake" hole in the cowling.

Chris

[mmoyle]

Chasing down the vibration in Marv’s 160 hp narrow deck. Has perhaps 200 hours on the rebuild after prop strike with new Millennium cylinders. The certified prop was removed and sent in for overhaul..it failed inspection...installed a new prop...vibration decreased a bit...but still to much...makes Mark not want to fly....
So....before Marv (fabricman) returns to Alaska to get his Pacer....we’re trying to find the problem and gain some trust in the engine...
Today we decided to tear into the engine. Found couple cracks in the exhaust system and a clamp missing from the tail pipe. Pulled the cylinders. All four piston skirts look like someone took sixty grit sand paper to them. Weighed the rods and pistons... dirty pistons were within 2/10ths of one gram. Rods are within 4/10ths of a gram. Next is to check crank flange run out...pulled the fly’n wheel...just as I’m setting it on the floor I notice two 1/4” nuts and bolts in the fly wheel....can’t find anything in the log book about it. No static balance...nada. Also discovered what looks like aviation gasket sealant between the case and cylinder base flange...dry brittle ****...now inside the engine..will pull the pan tomorrow..to give the internals a good bath and wash out the debris. Hope the crank flange indicates good... but those bolts in the fly wheel..enough to cause the vibration?https://uploads.tapatalk-cdn.com/20180517/009d23e38e6b89b3d6319255c8cb0377.jpghttps://uploads.tapatalk-cdn.com/20180517/98994084ace685c93976f0cbadb1da85.jpghttps://uploads.tapatalk-cdn.com/20180517/7e38440d82b6a332de5d62a7d51960b8.jpghttps://uploads.tapatalk-cdn.com/20180517/6164cb6f68f3fc4cb2185c6331849401.jpg
https://uploads.tapatalk-cdn.com/20180517/8aa5e5e9030807c1fcb4cf5fb9b82425.jpg


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[smcnutt]

One would assume those bolts were from an earlier dynamic balance that wasn't in the logbook but was done with the old prop before it was damaged. Come to think of it I will need to check if we have a logbook entry from when we did ours. Is a new dynamic balance in the plans?

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[Harold Kroeker]

The bolts on the flywheel are definitely enough to cause severe vibration. I have been balancing a few propellers recently using a DynaVibe Classic and it took 22g of weight at a radius of 6" to remove .73 IPS of imbalance on a Pacer and 6g at a radius of 6" to correct .18 IPS on my Clipper. Bolts in the flywheel holes are an approved method of attaching balancing weights but they should have been removed when the new propeller was installed.

Vibration Limits At Propeller RPM
DANGER —-------------- 1.25 Inches Per Second (IPS) Peak Amplitude. The propeller should be removed and a static balance performed.
VERY ROUGH —------- 1.00 Inches Per Second (IPS) Peak Amplitude. Propeller can be dynamically balanced; however a large amount of weight will be required. A propeller static balance is recommended. Operation at this vibration level could cause damage.
ROUGH ----------------- 0.50 Inches Per Second (IPS) Peak Amplitude. Propeller definitely requires dynamic balance. Long term operation at this vibration level could cause excessive wear.
SLIGHTLY ROUGH -- 0.25 Inches Per Second (IPS) Peak Amplitude. Dynamic balance will improve passenger comfort.
FAIR----------------------- 0.15 Inches Per Second (IPS) Peak Amplitude. This is the maximum acceptable vibration level after dynamic balancing.
GOOD -------------------- 0.07 Inches Per Second (IPS) Peak Amplitude. Vibration levels below 0.07 will not be detectable by pilots or passengers.

[Jeff J]

I agree with removing balance weights with any prop change or even a significant prop repair. I also think the weights should be removed and a balance accomplished after any maintenance that could affect the balance like a piston change unless the moving parts can be verified to weigh the same as what was replaced.

[Gilbert Pierce]

Good decision not to fly that engine.

[Steve Pierce]

I called Lycoming on an engine with a vibration after trying 3 different props. They recommended a vibration analysis and the frequency would tell you where to start looking. I will have to dig up my notes.

[andya]

would love to see your notes Steve, would be great reference material....

[walt.buskey]

Anything further on this? My A&P told me yesterday I need to start looking. He had an accelerometer instrument hooked up and it indicated too much vibration. Yes, this was around 2200. His suggestion was to start with a static balance of the prop. Suggestions as to how to get that done? Reading (and learning!) on this thread, I'll also be checking the position of the prop.

Walt

[Broncoformudv]

Anything further on this? My A&P told me yesterday I need to start looking. He had an accelerometer instrument hooked up and it indicated too much vibration. Yes, this was around 2200. His suggestion was to start with a static balance of the prop. Suggestions as to how to get that done? Reading (and learning!) on this thread, I'll also be checking the position of the prop.

Walt


You can take the prop to a prop repair shop and have it static balanced or call around and find someone local that does dynamic balancing of the prop which gets a better balance. Just had ours dynamically balanced and there was a noticeable decrease in vibration and thats with a new prop that had a static balance done.

[walt.buskey]

Thanks. So far, a reputable shop is "only" about 450 miles away.... (actually, quite near where 57A came from). There doesn't appear to be anything closer to central NH (that doesn't have a negative review). Anybody have experience with other prop shops in the Northeast? The one in Ltitz is New England Propeller Service.

[dgapilot]

When I lived in NY, I used New England Propeller in East Haden CT. Now that I live in MD, I use East Coast Propeller in Lititz PA. Looks like they are part of the same company now. Always had good results with both facilities.


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[akflyer]

Check into your local EAA chapters. Ours bought a dynamic balancer for the members to use. It is not very hard to do if you follow the steps.

[walt.buskey]

Thanks -- I'm planning to go with them when & if (most likely "when," methinks) I need to deal with a pro shop. When I first looked at their website it seemed they dealt with marine props, but now, yeah, I see they're part of the same outfit and do aircraft props as well. East Haddam, CT sure is a lot closer (only 180 miles); thanks!!

And I'll check with my local EAA (I am a member). Good suggestion, thanks!

[Brian]

I just downloaded this free vibration app to my Iphone from the app store. It would be interesting to capture and compare results from this app with the phone sitting on the glairshield in cruse flight. App is VibSensor.

https://m.youtube.com/watch?v=A-AnOwhJpOE

[walt.buskey]

Took prop down to NE Propeleer, had it overhauled (see other thread), same result. Still digging, just re-read this entire post, taking notes, lots of notes!

To Be Continued....