First flight... flipped over. Help?

[ResidualBacon]

Thanks Crafty Dan, I'll reassemble it correctly. I'm also going to grab a bunch of nylock nuts.

 

[wmmc01@gmail.com]

Hi ResidualBacon, I noticed you were able to remove the bits in the legs to expose the web appearance - how did you manage that? Mine look like etching and don't budge if I try to push them out. Maybe I'm not pushing hard enough, but don't want to break them either.

Also, Thanks for starting this post - it helped me enormously as I was going through my first build! Just have to add the props and I am ready for the maiden flight, I think!

 

[BEEAH]

Hi ResidualBacon, I noticed you were able to remove the bits in the legs to expose the web appearance - how did you manage that? Mine look like etching and don't budge if I try to push them out. Maybe I'm not pushing hard enough, but don't want to break them either.

They pop out, I think I used an allen wrench, held the short end against and tapped it with something else to get them to pop out.

I don't even use that landing gear anymore as it breaks the wire ties to easy. Now I use thick wire ties wrapped up.

Pics in this thread.

[url]http://forum.flitetest.com/showthread.php?14952-Electrohub-w-8-quot-Booms![/URL]

 

[wmmc01@gmail.com]

Thanks!

 

[ZoomNBoom]

Almost -- washer goes between the nut and the prop, with any tapered edge on the nut side:

You sure? I assume the taper is there to help center the prop, so Id put it on backwards. NO point in doing it the other way since the nut will have a nice flat base anyway.

 

[Craftydan]

The taper on the washer is generally wider than the prop hole itself, so in either orientation it would press flat against the prop, not press outward like a collet in it's collar (which would also be bad . . . there's enough trying to tear apart the prop's hub as it is, it doesn't need help). The prop should be self-centered on the shaft by it's own internal washer.

Remember these are friction-fit devices, so in general, larger surface contact => greater potential holding force. Which of the two would I prefer to slip against the washer -- prop or nut? I want the prop to be held in angle and I want to be able to turn the nut when tightening it. With the "cone" pointed toward the nut it would take less torque against the nut to overcome the friction required to further tighten the nut, and more torque on the prop to overcome the friction on the washer to slip. In that last 1/4 turn or so of the nut, the washer should be locked tight to the prop as the nut slides smoothly against the washer.

As a further data point, I've run across knurled washers before with a cone shape. The knurling is there to dig into a softer material to increase hold -- generally that's the fastened surface, not the fastener. The knurling always on the wider side of the washer.

Flip those washers over and you won't have to torque down the nuts as much to still get the same clean response out of your props.

 

[ZoomNBoom]

The taper on the washer is generally wider than the prop hole itself, so in either orientation it would press flat against the prop, not press outward like a collet in it's collar (which would also be bad . . . there's enough trying to tear apart the prop's hub as it is, it doesn't need help). The prop should be self-centered on the shaft by it's own internal washer.

On many/most props, the adapter ring goes in just on one side (underside, facing motor on a multirotor) and doesnt go through all the way. That underside usually is also nicely flat while the other side tends to be tapered; it makes more sense to me to use the taper of the washer to help center the prop from above as well, and you may even get a larger friction surface depending on how compatible the taper slopes are.

As for tearing it apart that way; in theory you would be right, but from the last 100 or so props I killed, I dont recall I ever managed to destroy a propellor hub, so I wouldnt worry too much about that.

Anyway, you may be right, but I guess either way will work.

 

[Craftydan]

On many/most props, the adapter ring goes in just on one side (underside, facing motor on a multirotor) and doesnt go through all the way. That underside usually is also nicely flat while the other side tends to be tapered; it makes more sense to me to use the taper of the washer to help center the prop from above as well, and you may even get a larger friction surface depending on how compatible the taper slopes are.

As for tearing it apart that way; in theory you would be right, but from the last 100 or so props I killed, I dont recall I ever managed to destroy a propellor hub, so I wouldnt worry too much about that.

Anyway, you may be right, but I guess either way will work.

As far as the ring on one side, it generally does go on the machine flattened side of the prop, so it should be held square with whichever side it pressed against. Compression should then ensure centering is maintained by forcing everything to square on both ends of the shaft. As far as which side of the adapter gets the tapered side of the prop . . . that will depend if it's being mounted as a pusher or a tractor. Even pusher props have the machine flattened side on the dirty-air side of the prop . . . where the washer is supposed to be.

If the tapered slopes are machined to match angle, then I'd agree -- they are designed to mate -- but the propeller manufacturer is seldom the adaptor manufacturer so those angles are not coordinated -- a standard "countersink" angle does not exist, so far as I'm aware (I've seen plenty of dimensional diagrams of prop and have yet to see the non-machined side specified in any way). As far as getting better area, I'd rather have the washer have more grab farther out radially than near the center -- 3mm of cross-sectional contact length near the shaft is far less area than 3mm of cross-sectional contact near the outer edge of the hub. In a perfect world with props matched to adaptors, the washers would be self centered with clean contact from the inner edge of the washer to the outer. Clearly this isn't the case.

This convention for "low torque on the fastener vs high torque on fastened" using a cone-shaped washer does extend outside the toy airplane prop adapter realm -- I've seen this applied to machines long before I saw them on props. There are engineering applications where the surfaces can be reversed in good practice, but generally only when the surfaces are machined to precisely match, and the cone is not flattened at one end.

I do agree that the "tearing it apart" is a minor effect -- the taper on these is below 10 degrees so the radial force will be less than 20% of the axial force -- but I've often wondered about many of the larger multirotors shedding props are more from defective prop castings or some encouragement from the prop mounting. Minor effects will show up as the root cause from time to time, but few will believe it's the root simply because it happens so infrequently. I've got no evidence, so even I take it with a grain of salt.

In the end, I agree -- it *WILL* work either way -- however one orientation will require a greater torque to properly fasten. As I have mentioned in other threads there is an issue with people under-torqueing the adapter for fear of shattering the prop (if it does, they need to buy better props!). So long as it's tight enough the bell and prop can't be slipped relative to each other, how you got there is of less importance.