Rotors

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Re: Rotors

Post by XieXie » January 15th, 2011, 1:10 pm

How many people are using Harlan Pennyplane Thrust Bearings?

We've been using paperclips so far. We did good at regionals, but for states we've been thinking about switching to music wire. Mr. Anderson suggests 0.020" to 0.025" music wire, but the pennyplane bearing has 0.018" hole...

Am I right in assuming that music wire thinner than 0.018" must be used with the PP bearing?
If so, is the benefit of the split tail over the SO bearing good enough to risk having the tiny smaller-than-0.018" wire bend/break?
I'm using 1/8" rubber right now.

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Re: Rotors

Post by smartkid222 » January 15th, 2011, 1:45 pm

Excellent question. I had thought of exactly the same thing.
Last year I used 0.017" music wire in the 0.018" hole. It fit but just barely. It held up at least to eh 58(15)=870 winds on 2 grams of 1/8" We didn't go any higher than that for other reasons. However, that size created another issue. I found that after a while the area around the hole on the thrust bearing would turn black. I realized that it was from the heat caused from friction between the shaft and the bearing. In other words the difference between 0.017" and 0.018" was too small and that it was creating friction, which i guess dissapated energy that would of went to turning the motors. Which means that really you need 0.016" or smaller shaft for that thrust bearing and that brings up the question again if it's going to hold the rubber motor.
Last edited by smartkid222 on February 13th, 2011, 1:20 pm, edited 1 time in total.
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Re: Rotors

Post by XieXie » January 15th, 2011, 6:43 pm

Hmm. I suppose that means I'll go with the SO bearing. But since it doesn't have the split-tail it'll pretty much be a one-use thing then. I suppose I'll just have to try making the bearings out of music wire with pliers then . . .

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Re: Rotors

Post by jander14indoor » January 16th, 2011, 5:56 am

Or you could get a 0.021 wire drill and drill out the PP bearing to fit your .020 music wire.

Oh, and the black stuff on smartkid222's bearing wasn't from heat, it was aluminum oxide from the bearing wearing to fit the wire. Its just aluminum vs the hard steel music wire. It wears in pretty quick and give low friction. Maybe add just a VERY small touch of oil and you'll be fine.

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Re: Rotors

Post by ironchef48 » January 17th, 2011, 7:09 am

I'm having trouble attaching my rotors- every time I attach the motor to the hook, there is so much tension between the bottom of the rotor and the prop hanger that the rotor spins very slowly even with a lubricant between the two or breaks all together. Any suggestions on how to fix?

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Re: Rotors

Post by blue cobra » January 17th, 2011, 7:26 am

It would help to know what prop hanger you are using. Also, are you putting some sort of bead or washer between the prop hanger and rotor?
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Re: Rotors

Post by ironchef48 » January 17th, 2011, 8:43 am

I've been using a variety of hangars from the piano wire mentioned on this forum to one i made out of plastic wire casing. In the first case I had a small round bead to keep the bottom of the rotor from rubbing the top of the bearing. The second had no bead, but still the same problem. I've added some commercial graphite lubricant (for pinecar racing) to reduce friction, but i don't think it helps as much as I thought.
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Re: Rotors

Post by XieXie » January 17th, 2011, 7:14 pm

So if you've eliminated having a bead/washer and having a lubricant as factors...

Too much tension between the hooks so that the whole thing snaps? Perhaps your rubber band is too short, pulling too much inwards?

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Re: Rotors

Post by illusionist » January 18th, 2011, 6:19 am

Make sure you use the full two grams that you're allowed. On 1/8 rubber, that will definitely reduce the amount of force on the bearings. And it allows you to put more wind into the rubber.
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Re: Rotors

Post by lllazar » January 18th, 2011, 5:05 pm

So i was just wondering, does anyone else double loop their rubber? We did this and got less than 350 winds....after improving my winding skills i can generally get about 1100 winds on 1/8 rubber.

Also, lately we've been having trouble getting our copter off the ground, as in it just falls to the ground...it is a new one we built and it weighs about 4.6 grams, would bringing the weight down help enough to get it up, or is there a bigger factor here affecting the flight capability?
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