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Mar 06, 2013, 05:13 AM
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Shikras GWS multirotor prop balancing guide

Shikras GWS multirotor prop balancing guide

If you want good vibe free quality - follow this. You will get better over time. I thought I was good at this a year ago. I now realise I wasn't.
It takes time to achieve perfection. Any one of these points will introduce vibes. A chain is only as good as the weakest link. Same principle.

If this is done correctly:
  • You will not need any anti vibe material
  • You will not have any vibes
  • Your copter will fly better (sensor become more accurate)
It's easy, logical but time consuming.....

Starting point:-

Select good props - known good ones in common use.
Select good motors - if can afford the ones with Jap EZO bearings or NMB even better.
Select good prop adapters

Prep work - start with crap end up with crap.

Check props visually - if they look twisted throw them - or use method below to reshape.

Check prop adapters hole is drilled in the center. If it looks off - throw it away....
Check tightening slots in prop adapter are cut evenly. If not - throw it away...
Check prop nuts hole is in the center some are not...
Check holes in prop nut washers are in the center - again, some are not...
Prop adapters can struggle to stay on shafts - especially anodised ones - So to fix that I hold motor upside down, hold fine emery paper against the shaft and turn it a few times to roughen it up a little. Must not let any of the filings / emery bits get into the bearings. Hold upside down.
On anodised prop adapters it may help to roughen / cut some slots into the face that touches the prop. This helps prevent the prop from moving around

Check motor shaft runs true. Especially if previously landed inverted
Check motor bearings are good - smooth, not rumbling and minimal play.

Setting up... Motors

Cut a small piece of prop balancing tape say 10mm *10mm and place on sid eof motor without prop. Now spin up and feel the vibes. Move the tape around until find the point with least vibes. Now increase/decrease amount of tape until you hit the sweet spot.
You can also add a very very thin film of threadlock glue on the shaft for extra grip onto the prop adapter. Not usually needed, but if you suffer from props coming off it may help.

Setting up... Props and adapters

Objective: Select / manipulate prop to ensure blades run true.

Put props on table with hub flat to table (light finger pressure may help). Now look at the blades and tips to see if they are all the same profile and distance from the table. Sometimes one blade can be out a fair bit.

Either pick the best ones from a bunch of props, or for extreme perfectionists:
I use slightly cooled boiling mater poured onto the blade whilst applying pressure at the area needed to reshape. Be careful and select the bend points and pressure needed carefully.
Aim is to get all the tips running true but without misshaping the air foil. Its quick and easy once done a few.

Objective: statically balancing of prop

Use a prop balancer. Carefully scrape along heaviest blade(s) with the edge of a Stanley knife removing a little at a time. It's important not to deform the overall shape. I Usually scrape only the top of the blade - along the whole length and keeping the same prop profile until it balances properly. Also a little from leading edges to remove any sharpness. On GWS, you'll soon learn the blades to trim! it's always the same 2 that need lightening on 9060....

Objective: True running of assembled prop/adapter on motor - and in position of least natural vibrations

Assembly the prop/ prop adapter, put on motor, gently tighten it up (not fully at this stage).
Visually check the adapter is running true and the point is not wobbling around. The prop tips should also be running fairly true with each other. No more than +/-2mm variation. Aim for best you can.
Now carefully ...
Spin the motor up using a servo tester whilst holding the motor and feel the level of vibes. Or use a vibe monitor.
Now turn the prop around on the motor until you get the point of least vibrations. You'll get better with practice! Especially hexa/octo users!
One optimum point found tighten it up fully - and check the prop adapter / prop tips are still running true. Sometimes have to loosen a little, apply sideways pressure and retighten.
Note that if you use washers with prop adapter - make sure they are centered and run true
Visually check the adapter is running true and the conical end is not obviously moving around. Should be no evidence of wobble when motors are running at low rpm. The prop tips should also be running fairly true with each other. No more than +/-2mm variation

Objective: dynamically balancing of prop for motor running

Spin the motor up using a servo tester whilst holding the motor and feel the level of vibes. Or use a vibe monitor.
Now cut a small piece of prop balancing tape say 10mm *10mm and place in center of one of the blades. Test for vibes and try on each prop. The one with the least vibes is the one to work on. Now move that prop tape in/out from center and/or increase/decrease size of tape until you hit the sweet spot. Sometime you have to do it with 2 blades.

Objective: review and perfect

Take a break - come back and test the vibes. If any one motor feels like it has more vibes than the others, it has! And you can do something about it....
Last edited by Shikra; Nov 04, 2013 at 05:19 AM. Reason: typo
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