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Help with Using Dynavibe

blueflyer

blueflyer

Well Known Member
I test ran my Lycoming 180 hp engine with my new dynavibe hooked up. It read .7 IPS at 300.
Will someone check my math here please:

weight=((180/10)+30))*IPS
weight=48*.7
weight=33.6 grams

Since I am putting bolts through the existing flywheel holes, do I install 33.6 grams, or do I double that weight and install 67.2 grams?

I understand that the weight should be installed 180 degrees from 300, and the rotation should go in the same direction as the prop spins.
 
that's correct except the most weight on one bolt is 1 oz or 28 grams. I would suggest splitting the weight using 2 bolts. one at 090 and the other at 150. use about 17 to 18 grams per bolt. Do that and tell us what reading you get on the next run. If you don't have a grams scale, buy one on ebay for about 10 bucks. Also, put the nut on the prop side of the flywheel. Keep an exact record of the weight you use.



blueflyer said:
I test ran my Lycoming 180 hp engine with my new dynavibe hooked up. It read .7 IPS at 300.
Will someone check my math here please:

weight=((180/10)+30))*IPS
weight=48*.7
weight=33.6 grams

Since I am putting bolts through the existing flywheel holes, do I install 33.6 grams, or do I double that weight and install 67.2 grams?

I understand that the weight should be installed 180 degrees from 300, and the rotation should go in the same direction as the prop spins.
Click to expand...
 
Start small

Start with the smaller weight, then do a run. I would then plot the point on a polar chart. Adjust the weight and re run. Its not a one run deal, takes about 3 to 4 runs depends how lucky you are. Does the dynavibe have a solution program? If not old fashion plotting on a polar graph will help a bunch.
 
balance

The 33 grams is correct but you have to split it because it is too much for one bolt. Just follow my instructions. I do this a lot. Jim

t
blueflyer said:
sorry for my ignorance, but which one is correct? Do I install 33 grams or 67 grams?
Click to expand...
 
Dynavibe results

Initial run was 0.93 IPS at 294 (I used 300)
So I added 22grams at 90 degree and 150 degree holes

Next run was .67 IPS at 323 (I used 330)
So I added 16 grams at the 120 degree and 180 degree holes

Next run was .38 IS at 004 (I used 360)
I just stopped here because I would have been adding weight to holes that already had weight added from previous runs.

From what i've read, i there should have been about a 90 difference between each run if I was doing this correctly. I realize I need to keep going to get the numbers down.

Anyone have any thoughts about these numbers or what I may be doing wrong?
 
balance

"I test ran my Lycoming 180 hp engine with my new dynavibe hooked up. It read .7 IPS at 300."

"Initial run was 0.93 IPS at 294 (I used 300)"

Which was correct?
 
Balance Solution

I own a Dynavibe Classic and have balanced quite a few props with it. Since this model doesn't compute a resolution, you have to do that part yourself. I found a nifty little phone app called iRotorBalance. This app will compute a final solution after an initial "best guess" run with a trial weight. Adjustments are also calculated to include a different position radius, split weight positions etc. It costs $5 on the Apple App Store.
 
balance

As I understand it, your initial run was .7 @ 300.

Then before adding any weight, you ran it again and got .93 @ 294

Something is not right. You should never have two runs with that much difference in IPS and .93 is a HUGE vibration.

Can you better describe your situation, prop, setup and maybe text a photo to me.
 
Dynavibe Identifies the Heavy Spot

If the vibration got worse at about the same angle, I suspect you added weight to the heavy spot. The Dynavibe identifies the heavy spot for you, so you have to add the weight on the opposite side. If the machine says 0.7ips @ 300 degrees, you'd add weight at 120 degrees to compensate. A temporary weight of about 10grams on one of the spinner screws would get you started. Once you measure again with the 10grams installed at 120 degrees, you can use that reading to calculate the correct amount of weight and it's location with more accuracy. It's a matter of fine-tuning using the same technique after that. The final weights are installed in the flywheel if it has holes, or in the spinner bulkhead if it doesn't.
 
Last edited:
Just for clarity, I ran the dynavibe 3 times.
First was .93,
then .67
then .38. I'm sorry i created confusion.

Please ignore my post saying .7.....

I appreciate the tips so far. Since I started at .93, I may get someone more experienced to help. I could need a static prop balance.
 
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