Prop balancing
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Yes - and the illustration contained in the link is not the correct way to have the balancer set up when using the threaded rod with self-tightening props. The correct way is shown in this vid (at 4m:22s).
OK ... the video shown by Steve777 is good BUT :
There is a fundamental error in use shown.
When balancing normal props and using the two CONES ... one cone should be turned and FLAT to the prop hub, while other CONE has the taper into the prop shaft hole. Reason is that for example - APC props are produced with the rear shaft hole as the precision hole.
See APC technical here :
Technical Support Advisories | APC Propellers
Funny enough - the Oday and OCDay manuals show correct with flat cone + tapered orientation. The DuBro manual is a bit .... 'lacking' compared to the Oday ... (ODay manual uploaded below ....)
Second - and this is easily checked by any user ... the requirement to be perfectly level is not actually necessary. The support discs that rotate with the shaft are designed to operate at near level state. Yes - it is good to level it best - but it works just as well at near level.
The push in rod to DJI props ... in the kit - there should be a bronze bush that is the fit for DJI props, this along with the silicon tube is the way to do it. Oday kits certainly have it and DuBro ones friends have - they have same.
Nigel
There is a fundamental error in use shown.
When balancing normal props and using the two CONES ... one cone should be turned and FLAT to the prop hub, while other CONE has the taper into the prop shaft hole. Reason is that for example - APC props are produced with the rear shaft hole as the precision hole.
See APC technical here :
Technical Support Advisories | APC Propellers
Funny enough - the Oday and OCDay manuals show correct with flat cone + tapered orientation. The DuBro manual is a bit .... 'lacking' compared to the Oday ... (ODay manual uploaded below ....)
Second - and this is easily checked by any user ... the requirement to be perfectly level is not actually necessary. The support discs that rotate with the shaft are designed to operate at near level state. Yes - it is good to level it best - but it works just as well at near level.
The push in rod to DJI props ... in the kit - there should be a bronze bush that is the fit for DJI props, this along with the silicon tube is the way to do it. Oday kits certainly have it and DuBro ones friends have - they have same.
Nigel
Sooooo, I was running my thumb and index finger up the port side landing gear and felt the unmistakable kink in the plastic. (This is a second hand unit, BTW.) I had originally inspected the bottom shell arms where the cracks seem to manifest themselves and was delighted to find none. After having improvising as @Steve7777's video shows, I found all 4 props were VERY much in balance. This led me to look elsewhere. Sure enough, there is a crack on the top shell on the LR arm (don't know how I missed this before).
I attempted to use HB-WELD epoxy to fix it. The first 2 flights of about 17 mins each turned out great. Upon inspection of the fix afterward I got home and reviewed the videos, I found the epoxy had cracked. Attached are pictures of the fix after the flights and after removing the epoxy and the screws that hold the shells together. As you can see, there was not enough epoxy on the surfaces of the crack to hold.
My questions to all are:
1) Would the amount of epoxy currently in the crack (second picture) compromise the integrity of another application?
2) Is there another adhesive that would be better to try to fix this, short of replacing the shell (I do have a top shell, but grrrrr)?
I attempted to use HB-WELD epoxy to fix it. The first 2 flights of about 17 mins each turned out great. Upon inspection of the fix afterward I got home and reviewed the videos, I found the epoxy had cracked. Attached are pictures of the fix after the flights and after removing the epoxy and the screws that hold the shells together. As you can see, there was not enough epoxy on the surfaces of the crack to hold.
My questions to all are:
1) Would the amount of epoxy currently in the crack (second picture) compromise the integrity of another application?
2) Is there another adhesive that would be better to try to fix this, short of replacing the shell (I do have a top shell, but grrrrr)?
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There's lots of talk here about how to repair cracks and what compounds are good. Search Results for Query: repair crack | DJI Phantom Drone Forum
However, that's a nasty one and I wouldn't mess around and would just replace the top shell, especially as you say you already have a spare one.
I did remove the screws and spread it apart to show the inside surfaces.
The reason I want to go the crack fix route is that I don't want to damage the bottom shell while attempting to separate them. I have the bottom shell as well as the top shell and while studying how they separate, I unintentionally snapped one side together and it was a royal pain in the arse to get it apart again.
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You might find this useful.
There are other vids showing fairly similar techniques on YouTube if you do a search.
I have to comment that a break such as that in a top shell is unusual and in my mind indicates an Impact Fracture - not a stress fracture as usually occurs in the shells - particularly the bottom half round motor screws.
The Top shell in that region does not carry load of the motor - but aids in stiffening the bottom shell carrying the motor.
It is possible to repair such break, but requires good filling material that bonds totally to the plastic as well as keeping the shape.
If it was me ... and not having a top shell spare ... a small thin strip of Carbon Fibre resined across the break inside to put back strength and support. The external part of the break ground to a V to allow filling with resin and ground plastic ... smoothed before fully set ...
Its not a simple job of fill with resin if you want long term results. Trouble with Epoxy and similar - are they are not best resins for plastics. They tend to crack away after time especially if subject to vibration. A better and much lighter resin is PolyUrethane ..... with moisture this expands and literally foams filling all spaces and voids.
Nigel
The Top shell in that region does not carry load of the motor - but aids in stiffening the bottom shell carrying the motor.
It is possible to repair such break, but requires good filling material that bonds totally to the plastic as well as keeping the shape.
If it was me ... and not having a top shell spare ... a small thin strip of Carbon Fibre resined across the break inside to put back strength and support. The external part of the break ground to a V to allow filling with resin and ground plastic ... smoothed before fully set ...
Its not a simple job of fill with resin if you want long term results. Trouble with Epoxy and similar - are they are not best resins for plastics. They tend to crack away after time especially if subject to vibration. A better and much lighter resin is PolyUrethane ..... with moisture this expands and literally foams filling all spaces and voids.
Nigel
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... and pretty easy to do too - so there's no reason for you not to go ahead and change the top shell. That will also give you (hopefully) plenty of time to contemplate and carry out a repair on the original, along the lines that solentlife has very usefully suggested above...
Replaced the top shell this morning. Actually went pretty well (practiced on the replacement shells). Next is test flight.
@solentlife, you say resin is best to fix cracks? There is some epoxy down in the crack on the ends, but there is a substantial portion that is still clean for solid contact.
@solentlife, you say resin is best to fix cracks? There is some epoxy down in the crack on the ends, but there is a substantial portion that is still clean for solid contact.
Flew 3 batteries worth last weekend and still had some jello. Not nearly as much as before. Prop balancing is next.
Everything is nice and properly fit with the gimbal and camera. Nothing is loose, no grinding noises.
One thing I have noticed (I always hand catch at the end of flight because of all the dust here in the desert) there is a lot of vibration. The AC is shaking in my hand right when I grab it until the motors stop. Could it be that a motor got damaged on the alleged hard landing? They all have the same resistance to spinning when powered off. The only thing I can think of is the axis of off just a fraction on one and not spinning true.
Everything is nice and properly fit with the gimbal and camera. Nothing is loose, no grinding noises.
One thing I have noticed (I always hand catch at the end of flight because of all the dust here in the desert) there is a lot of vibration. The AC is shaking in my hand right when I grab it until the motors stop. Could it be that a motor got damaged on the alleged hard landing? They all have the same resistance to spinning when powered off. The only thing I can think of is the axis of off just a fraction on one and not spinning true.
Carefully check all props for any deformations ... they may balance but if a blade has a slight deformation - vibration.
By hand hold AC and with other hand see if any motor has any slight movement in its mount ... cracked mount / loose screw can give a small amount of movement when power applied.
If a motor is slightly off angle but steady in that and does not move - it should not cause vibration as Flight Controller will compensate rpm / thrust ...
..........................................
This is a wild guess but if all else fails ....
Set up the AC on a solid flat surface and intention is NOT to fly but just to spin up motors / props.
If during a hard landing you may have caused a slight bend in a shaft .... that means the prop will not perform a flat rotation.
How to check ? You need a fixed pointer just above prop dead centre ... spin up motor and see if the prop centre shows any sign of wandering from that point ...
You can do by this by hand on its side if you can fix both AC and pointer .... spin prop by hand and watch ... you'd be surprised how good the eye is to catch this ...
If it has caused a slight bend - even a small amount would cause vibrations.
Nigel
By hand hold AC and with other hand see if any motor has any slight movement in its mount ... cracked mount / loose screw can give a small amount of movement when power applied.
If a motor is slightly off angle but steady in that and does not move - it should not cause vibration as Flight Controller will compensate rpm / thrust ...
..........................................
This is a wild guess but if all else fails ....
Set up the AC on a solid flat surface and intention is NOT to fly but just to spin up motors / props.
If during a hard landing you may have caused a slight bend in a shaft .... that means the prop will not perform a flat rotation.
How to check ? You need a fixed pointer just above prop dead centre ... spin up motor and see if the prop centre shows any sign of wandering from that point ...
You can do by this by hand on its side if you can fix both AC and pointer .... spin prop by hand and watch ... you'd be surprised how good the eye is to catch this ...
If it has caused a slight bend - even a small amount would cause vibrations.
Nigel
Amazon sells TWO Dubro prop balancing 'kits'... the only difference is the rod included.
One has a 6mm threaded rod... left-hand threads on one end, right-hand on the other end. The other Dubro kit has a different kind of rod for props that do not have threads.
Amazon also sells the 6mm threaded rod separately. For my p3p I bought just the rod and then balance on top of a wine glass.
One has a 6mm threaded rod... left-hand threads on one end, right-hand on the other end. The other Dubro kit has a different kind of rod for props that do not have threads.
Amazon also sells the 6mm threaded rod separately. For my p3p I bought just the rod and then balance on top of a wine glass.
umanbean,
Thanks for info. I'd ordered the DuBro balancer from a seller in Perth, Australia and it arrived today together with a 6mm shaft and it works perfectly.
3 of 4 "real" DJI props are just slightly out of balance and I'll give 'em a shave tomorrow when the sun is shining.
And hey, you should have better things to do with a wine glass, surely! Ha, ha.
Thanks for info. I'd ordered the DuBro balancer from a seller in Perth, Australia and it arrived today together with a 6mm shaft and it works perfectly.
3 of 4 "real" DJI props are just slightly out of balance and I'll give 'em a shave tomorrow when the sun is shining.
And hey, you should have better things to do with a wine glass, surely! Ha, ha.
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I think it's been stated here before, probably many times - but I personally find it better to stick tape on the underside of props to balance them. You can always remove the tape and re-balance the prop later if needed.
Many ways to do it ... but main is to not affect TOP surface .....
As here - the quickest way is to add a sliver of tape to the back of blade ...
My preferred way which preserves the longitudinal weight distribution of the blade is to lightly sand along the rear of blade from hub out to tip. Or you can add a lick of nail lacquer ...
For my P3P props ... I wanted painted tips to create visible circles ... so I used that fact to balance ... using very thin lacquer style paint to create the tips. This meant that each blade came out similar ...
It may interest some - Helicopter rotors ... its normal to wrap the tape round the leading edge and join at trailing edge ... sharp blade removes the extra. Reason is to not have an edge to the tape that air can lift.
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I also use the DU-PRO balancer but one problem with balancing drone props (P3A in my case) is that there is not a central hole all the way through the hub of the prop, it is threaded one side, right and left hand threads, and pointed the other side giving no accurate way to locate it on the balancer.
So I made a balance shaft from a couple of old motors.
The motors are out-runners so when you disassemble them you are left with the threaded part of the shaft, the aluminium outer casing (which had the magnets around the inside of it) and the internal shaft with is part of the threaded part. You need to cut/turn the aluminium part off the shaft just behind the threaded bit. I used my little wood turning lathe.
Make it nice and smooth using emery paper. Get a 6" length of .186" - 3/16" OD brass tube. The motor shafts are a snug fit inside this and I just put a bit of super glue to secure one of the spindles in each end.
Polish the outer surface of the brass tube so it runs smoothly on the balance rollers.
So I made a balance shaft from a couple of old motors.
The motors are out-runners so when you disassemble them you are left with the threaded part of the shaft, the aluminium outer casing (which had the magnets around the inside of it) and the internal shaft with is part of the threaded part. You need to cut/turn the aluminium part off the shaft just behind the threaded bit. I used my little wood turning lathe.
Make it nice and smooth using emery paper. Get a 6" length of .186" - 3/16" OD brass tube. The motor shafts are a snug fit inside this and I just put a bit of super glue to secure one of the spindles in each end.
Polish the outer surface of the brass tube so it runs smoothly on the balance rollers.
Innovation is the art of creation ...
But Cheddarman ... is there no spindle and smooth insert in your kit ? ODay which is same design as Dubro has a spindle ... a smooth brass ferrule and silicon tube ... the combo is a snug fit into the P3 prop and balances perfectly. Its designed so the rod can turn in the stand as well as the smooth bush turn on the rod ...
If you have a lathe - I think I would have just turned up a bush to fit the rod similar what I have. Using the threaded shaft ? That locks the prop and does not allow it to turn as well on the rod.
Sorry about the poor lighting and slightly out of frame - but its a quickie vid just to show the ODay / Dubro system ...
But Cheddarman ... is there no spindle and smooth insert in your kit ? ODay which is same design as Dubro has a spindle ... a smooth brass ferrule and silicon tube ... the combo is a snug fit into the P3 prop and balances perfectly. Its designed so the rod can turn in the stand as well as the smooth bush turn on the rod ...
If you have a lathe - I think I would have just turned up a bush to fit the rod similar what I have. Using the threaded shaft ? That locks the prop and does not allow it to turn as well on the rod.
Sorry about the poor lighting and slightly out of frame - but its a quickie vid just to show the ODay / Dubro system ...
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