Dynamic Prop Balance - Grumman Style
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- Опубликовано: 20 окт 2024
- Dynamic Prop Balance - Grumman Style: A practical example of prop balancing. Setting the system up, removing old weights, first run, calculate weights and position, apply, then run again until balance is done.
Very clear, hands-on demo. Thanks.
Thank you.
Learned alot from this video. Great job! I'm ready to fly up there and let's get to balancing.
Come on up and we can do this for you.
Gotta love the guy at 9:35 getting absolutely blasted after losing his hat and glasses, then continuing to chill in the propwash lol
Everybody had a good time.
I am ordering a DynaVibe for my Skyhawk.
I will balance my prop with the spinner installed.
Engine static balanced, "0" time. Propeller static balanced, "0" time.
Engine/Propeller will be dynamic balanced when I receive my DynaVibe.
This Cessna owner thanks you for showing the process, the test equipment, and the calculations.
Just a little $1700 toy?
OK
Did you balance it yourself? How did it do?
I probably will get flamed for posting this but back in 1982 we did a prop replacement on a privately-owned AA5B on the grass by the tower at Southampton/Eastleigh airport in the UK. The old prop had cracked through one of the mounting holes but the owner had only picked this up when he'd had to replace the alternator. Undid the old prop, torqued the new prop up, rammed a stick in the ground and did a prop swing to check it was properly aligned, put the spinner on then took it into the circuit for test flight!
Smooth is always better than rough.
I think you should balance the muffler bearings and replace the high compression hubcaps
Glad you liked it
The advantage of dynamic balancing is that it balances ALL of the rotating components concentric to the output shaft, the prop, spinner and its bulkheads, starter gear and for the most part the prop end of the crankshaft. I assume the spinner was removed for better visibility during filming this video.
According to FAA advisory circular AC20-37E the reflective tape must be removed from a metal prop because it can possibly trap moisture causing corrosion.
For an experiment we twice balanced a prop, got our reading after final balance. Then we added the spinner, so light and near the center of rotations, too long screws would cause a bigger problem (all the same size). No reading change. FYI. I could see sitting on bare metal, but primed and painted (wax removed in the area) should cause no problems. Let me go and read up on this.
@@GrummanPilots I don't disagree but thought you might like to know what it says in the Advisory Circular. Let's face it most all prop manufacturers and prop repair shops put manufacturers decals on props all the time. I balanced two last week on very recently overhauled props, one with a Sensenich the other with McCauley stickers on them.
It was the McCauley propped Cessna that I accidentally reinstalled the spinner 180 degrees out after installing the permanent weights and the confirmation run said I MESSED UP SOMETHING! That was when I noticed the miss-aligned index marks! At least it was an easy fix!!
no spinner? the Spinner plays a part into this gentlemen, your readings will be off if it isn't installed
The spinner is thin and very light and does not add much to imbalance unless it is damaged.
@@GrummanPilots Or off center, you can see them occasionally wiggling a bit toward the front. The spinner is also all near the center of rotation so contributes MUCH less to overall balance than the same offset of weight near the tip. THUS, the DYNAMIC balancing. Something can be "perfectly" statically balanced, but if it has large mass concentrations somewhere, be horribly dynamically imbalanced and shake like heck.
Correct. This should have been balanced as a system, with the spinner on.
I looked but didn't see a video on checking the prop is indexed correctly. Is there one? And I assume you verify it is correct before balancing the prop. Thanks a lot for all of the video's!
k
@@GrummanPilots what a garbage response.
Based on your calculations, you were to add 16 grams, then 5 grams on the second, finer, round. You then doubled the weight, why?
I THINK he said it was because the calculations are for weight at 1-foot from the axis of rotation. The bolt holes are ≈6 inches from the axis, so more weight is needed for the same effect.
Good question.. might need a good explanation
weight assume a 12 inch radius (1 foot). we are using 5.5 inches so .4386 into the weight gives heavier weight at closer radius.
Shouldn't the oil be up to temp before you start running up to max RPM?
The plane had flown for 2 hours to get here, so it was warm.
@@GrummanPilots Good, you guys had me worried for a bit!
@@GrummanPilots yeah right. You guys are boobs
Maybe over in Pussy-town where you are from. But not in the real world.
Shouldn't this be done with the spinner installed?
Since he's using the ring gear to put his balance weights, you're right. He could have left the spinner on.
Yes
Not really needed, caN BE CHECKED AFTER BACK ON WITH ONE RUN, BUT NOT ENOUGH IMBALANCE TO MATTER
where are you all at for this. sounded and looked like Apopka ???
KHAO, Hogan Field NW of Cincinnati, Ohio. Come and see us!
Your calculation comes up to 15.84 grams (you wrote on the board), but then on the next scene you are adding 30 grams. Why?
The holes are at 5.5 inches from center and the weight from the calculation is for 12 inches from center, so you have to divide the weight by ,4583 to get the value to use.
so whatever 5.5 / 12.0 comes to to get the equivalent weight for this location closer to the hub.
@@GrummanPilots thank you so much. I’ll be doing the balancing tomorrow. Thanks for the amazing video. Keep them coming.
So,if we remove the flywheel and balance it should read cero with those added nuts and bolts ??
Or as close to zero as you choose to pursue.
Great video, thanx
Glad you like it, that is why we make these to help folks master a new area.
I’m a little confused how engine HP/10+30x.033 comes to 15.84? By my calculations it comes out at 27.9?
180/10 + 30 * .333 = (48 8a .333) = 15.94
The other thing is that that weight calculation assume mounting at a 1 foot radius, but we mount it at 5 something inches, so you need to up the weight by the ratio 1 ft / mount distance) to get the weight to use. FYI
After finishing the balance, Do you remove the tape on the blade or do you keep it place? Thanks.
We leave the reflective tape there in case we ever need to balance again.
Thanks for the video. Formula was the key using the budget dyna vibe.
Agree
Used YOUR formula on my tiger: second dynavibe reading had same angle but half the IPS so added another weight to get the IPS to .03
This is why I share information not charge for it as a perk of membership!
Not sure what you’re saying. My comment rephrased: 1 thanks for sharing, 2 formula seems off by factor of 2 . I had to double the weight the formula calculated to cancel the vibe, using the same aircraft and same DynaVibe as you. What was the source of your equation? Cheers
Any reason why the spinner wasn't on?
Yes, it is light, near center and very balanced in its mass distribution and it makes it easier to add weights as you test the balance. After doing many planes we have never seen a spinner put it out of balance.
I was concerned if the spinner baffle structure could crack or damage itself while running without the spinner . Thanks for the response and info. @@GrummanPilots
good job
Thanks for watching and commenting.
Did anyone notice the G.M. one wire alternator? As good as it gets!
Ford actually
Well unfortunately you were supposed to balance that with the spinner intact as well.
I do not believe much imbalance is in a spinner. FYI
Where’s the spinner, wheres the warm up and why wasn’t the sensor moved much further forward?? Who did not read the manual
The spinner is not used, the was a warm up, and the sensor location is in range and quite reliable.
Just read thoroughly the manual and the spinner has to be taken into account and the sensor should have been one if not 2 crankcase holes more forward??
One more hole could be done, but then the sensor would not hit the prop. So two holes forward is out.
Good job my friend
k
VERY GOOD BALANCE PROPELLER, BRASIL OK
Many kinds, choose what you like can afford.
How do I become a aviation mechanic ??? I’m getting old and I love air planes!
Study for aircraft maintenance engineering (AME) course.
Vipul Cenation how long does it take?? I race a lot and have little time at home. Is there a online deal
Groom Lake Attend an FAA approved school. Takes about 15 months and then you need to test which can prove rather difficult for some people.
Buzz and Woody I like taking tests I’m pretty good at them. Can you pass the test and not have to do the schooling ??
Groom Lake No. Unless you have 30 months of documented experience working under an A&P or if you prior military with approved experience.
I haven't watched this yet in its entireity but just off the top of my head, the transducer should be as close to the front bearing as possible. You could have gone two case bolts to the front to mount it - you must have had some reason for mounting it towards the back.
Someone below says something about you doing some math to figure out your weight placement. No math is necessary. The Classic model Dynavibe tells you how far it's out of balance and exactly where weight is needed. What math is necessary?
The GX-3 model even tells you exactly how much weight is needed, in addition to the location.
In any case, the Dynavibe is extremely accurate and is a pleasure to use. I haven't looked to see if you have the Classic (the original) or the GX-3 but in either case you've got the best.
The engine manufacture, airframe or test equipment manufacturer will tell you where to mount the transducer to get the correct vibration readings. Crankshaft vibration at #3/#4 journals may be part of the equation.
The longer arm from the motor mount cause issusd like that
@@GrummanPilots Eh? Not grokking that since the videos show two case bolts closer to the prop that could have been used. Motor mount wouldn't have anything to do with the distance between your sensor and the prop, would it?
Too close of course doesn't work. The sensor needs about 8 inches or more from the reflective tape in order for it to register - I've no clue why that is but I've encountered it enough times to have noticed this factor. My decision to place the sensors (I have both sensors on the same mount) is choosing the closest case bolt that still gives about 8 inches, maybe 10, spacing from sensors to prop.
Your mention of taking the crank bearings into consideration is worth thinking about . . . I'll talk to Steve or Matthew at Dynavibe and see what they say.
It's really great to have ones' own Dynavibe. For me it's an essential hangar tool. It also allows one to be of service to hangar neighbors or friends.
Happy New Year
In first attempt he ended up with weight calculation of 15.8 g but he finally installed 32g ! Why he did that ?
Because the weight calculation assumed a location at a mounting radius that was not available. He had to go closer in, so to get the same effect the mass had to be increased. It's a simple proportion calculation; if the radius is half as much you need twice the mass. But he also SAID that- weren't you paying attention?
Weight is based on a 1 foot radius, we are using the holes at 5.5 inches, thus .4583 into the weight to get the proper weight at that location
Excuse me what can I do if we have low oil pressure thanks
MAHER RASHAD low oil pressure on a gauge or actual low oil pressure?
TIG881 Or maybe attempt to diagnose the issue?
Unless you’re being sarcastic
Anything above 5psi oil pressure is acceptable.
Check pump with manual gauge, repair as needed
These guys will be buried wearing a Grumman T shirt......LOL
Not an insult, maybe I'll wear an old AYA shirt
Wow. Pilots trying to be A&P Mechanics lmfao. You need spinner on to do dynamic balancing....
Yippi ya! Hey Joe, even worst!
Imagine people trying to be aircraft manufacturers.
LaughingYfaoff every July in Wisconsin dude.
Maybe
Not really. Taking the spinner off and on while doing run-ups is a major PITA. Better to do run-ups without spinner and, once spinner is re-installed, make any small correction necessary using a spinner screw washer (it's only going to be off by a hair, if at all). The spinner screw washer (or piece of lead weight) can be installed inside the spinner using adhesive. Centrifugal force will only strengthen that adhesive bond. Putting it inside eliminates anything "unsightly" - as some might consider with a visible external washer under a spinner screw.
I started to say kudos for getting everyone out of the prop line and in front of it before starting and running that thing up, just mounted with the balancer. THEN people start walking in from the right during and just after the run up. Facepalm. One of those things that probably almost NEVER happens, but when it does ...
Also, I'm surprised in this day and age you have to do hand calculations. Why aren't those designed INTO the device, with inputs requested for the parameters you need, just to prevent stupid math errors? In this day and age a tiny cheap processor costs basically nothing ($0.05?). Some designers need to be drug kicking and screaming into the 20th century, and yes, I meant 20th.
I think the fact that he's measuring at the front of the prop and not balancing there is the reason for the discrepancy in readings. I think he should be taking the weight OFF opposite the heavy point at the hub by a very light surface shaving. Just sayin'. Dynamic balance is definitely the way to go, especially if you are having vibration problems. Checking all the prop dimensional parameters on a measuring stand should be done prior to balance, though, if the vibration is at all bad, as there are other things that can cause vibration than balance, like a prop bent to over or under pitch, especially out toward the tip asymmetrically just slightly, even. Kind of like with a wheel on a car, you can balance a square one to a "gnat's eyebrow", but it's still not going to roll worth a damn. ;-)
Yeah, you'd think for a 2500 to 4000 dollar device it'd have the ability to do do the calculations for you.
@@mfk12340 Bullshit. I do these calcs in my head- it ain't rocket science. FURTHERMORE, the indicated location and correction weight doesn't mean shit if there's no place to mount the weight; usually you wind up splitting the weight to distribute the mass either side of the desired location...but then the CG of the combo isn't at the same radius, meaning you need ANOTHER correction. You guys that are complaining that the DynaVibe doesn't do all that for you are classic Dunning-Kruger idiots; if you actually understood the process you'd know why it's not in the cards.
Besides that, the errors due to the inconvenient weight placement means that it's futile to try to calculate "exact" correcting weights; if you can't arrive at a plausible correcting weight off the top of your head you probably buy lottery tickets because _you're lousy at math._
A couple other things: 1) it's not necessary to run "max" RPM; 1500 rpm is fine. 2) the transducer needs to be as close to the plane of the prop as you can get it- otherwise you're only getting a fraction of the signal, although that's not a show-stopper. Same with offset transducers. You can do it, but why handicap yourself? 3) Finally, you're not done until you take readings at every few hundred RPM up from idle to look for resonances or under-performing vibration isolation in the motor mount- you'll know that problem exists if the phase angle or IPS suddenly changes as you go through the range of RPMs. In that case you either have a forbidden operating point or you need new rubber isolators...or in some cases, you've got a bent piece of tubing in the motor mount. And BTW- last I looked, the DynaVibe was only $1600.
BTW new machines do the math for you and get you there quicker. FYI
@@GrummanPilots I expected as much.
.06 is as good as you can get with all those old farts and several math problems?! Wizzzzzeak!
Glad you liked it
The rookie walks up behind the plane.
All welcome
Need to kick all those spare people out of the area. Working on spinning props is dangerous enough when you only have yourself to watch out for. You also need a spreadsheet for that calculation.
You will notice folks disappeared prior to a run
8:47 stop asking really good questions...
Glad you liked it
Most unsafe test ive seen. Dogs, people all round and in prop arch. Just wow
Too bad you did not see the sections where the tests were run.
Very much agree. I sweep the area below and around the prop and for sure don't allow any dogs or people running around anywhere close.
You need to stop acting like a bitch.
@@GrummanPilots : those dogs are perfectly suited for airports. Rod Machado even tells of guy who used his dog as his Safety Pilot during IFR practice. The dog always barked if alerted to traffic.
Heck yah.
Machado wondered what would happen if the PIC flew near the Alpo Factory.
10 guys to balance a prop... ha ha.
Teamwork!