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Dynavibe technique optimization ?

Larry DeCamp

Well Known Member
I used my Dynavibe the first time and it is amazingly simple to operate, but the optimization process is a little tedious 🤔 it appears that the best solution will usually end up with weight added BETWEEN two adjacent holes in the starter flywheel. To accomplish this, bolts must be installed in two holes with varying weight and location guessing. I started with 3.3 IPS and stopped at .05
It appears the ideal process would be a link that spans two adjacent holes at the approximate location needed, and a way to secure varying weights at easily adjusted location on the link between holes. I envision this is the only way to get really close to perfect without a lot of luck and patience.
Before I ponder this objective any more, I thought the braintrust may already have the solution. Your input is appreciated.
 
Larry, I’m not totally sure what you’re asking, but you have a finished ips of .05 and want to get it to finish lower? Not that you really need to since it’s already quite low, you could start a new job, leave the weight in place and run it. Your new solution should not require much weight at all. You can probably just add a thicker washer under a spinner screw and get the ips down lower, but you probably won’t feel the difference. I’ll assume you are using the Classic? I have the GX3 and it requires more programming info to start with, but gives much more detailed information and solutions. Are you sure the decimal is in the right place? 3.3?
 
Thanks Dave

You are right, the starting point was.33 with balanced engine and new Catto 3blade. It is noticeably smoother on ground run, but I did not fly yet.
Two questions:
How much variance ( IPS ) should I expect over time ? Ie, seasonal change, carbon deposits on pistons etc.
How much, and why will the IPS vary from ground run RPM to say 2400 RPM. I would predict the change would be linear, proportional to RPM change ?

Thanks for the clue .05 will be good in flight .

Clarification on original question. Has anybody devised a method to securely attach ONE weight or clamp BETWEEN flywheel holes and then easily vary weight on the attached device to minimize IPS value.
 
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If you re down to .05 IPS you 're good to go and in excellent range for first flight or for that matter anytime thereafter. You should not see any changes unless something in that rotating mass gets altered, And by that I mean down to washers and hardware on the spinner and the orientation that all that might go back together at some future date. You should mark all of that so you or someone can re assemble all that back to the balance run config.
Your question on the split weight between flywheel holes is a good question and there are programs out there which will let you split the weight between the 30 deg holes and MAYBE be abe to get the .05 down . But practically you prob realize that the bolt and nut you install on that second position will exceed the weight that is actually required to gain any reduction in the IPS reading. But just for fun you can't hurt anything by trying. You always know you can get back to that .05 ..
I'll look and see if I can find the split weight app for spreading it 30 deg , I had a ACES prop balancer at one time which I believe had that printed in the instructions. It's just MATH!
 
Thanks Dennis

I already split the weights in two adjacent holes and after washers and many adjustments got to .05 . It appears to be an infinite iterative process complicated by the minimum weight of an AN3 bolt and nut for primary attachments.
The spreadsheet would help if it can account for minimum faster weight.
Also, the option to use washers on the spinner adds some other radial locations for fine tuning without screws in the spinner back plate.
 
Larry , I did find this on split weight and various radius weight position. Not sure the link will go thru but here's a web site article on using a polar graph to do this . Maybe more interesting than practical in our case.
https://reliabilityweb.com/articles/entry/balancing_weights_radius_changes_and_splitting/

I know there are people on here that could set up a spreadsheet that I could even use, that would solve the 30 deg split weight solution or maybe the different radius placement. Maybe one of them will do that for us!!!
 
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Dynavibe

If you do a search for Dynavibe on the forum, someone posted they had an excellent program for splitting weights.
 
Larry, you could give Steve Sennett a call at DynaVibe. Steve is an authority on the balance/tracking/vibrational analysis subject.
 
...
It appears the ideal process would be a link that spans two adjacent holes at the approximate location needed, and a way to secure varying weights at easily adjusted location on the link between holes....

Yes, a small threaded rod with washers at each end and a nut on it would allow for fine adjustment of the weight (nut) between the two bolt holes. Maybe two nuts, to they could be tightened against each other. Probably not practical because you wouldn't want the weight of the contraption to exceed the weight to be added. Perhaps a tubular spacer between the two nuts to be cut to length to reach total weight needed ... nah, how would you control the total weight when welding the rod to washer?

Finn
 
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