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Pusher Prop New, but 30 mins later & ovaled out? *Help* What did that?

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Pusher Prop New, but 30 mins later & ovaled out? *Help* What did that?

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Old 09-17-2009, 10:40 PM
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GizmoMadMax
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Default Pusher Prop New, but 30 mins later & ovaled out? *Help* What did that?

Help, any advise on this situation,

New APC 11x7P = pusher on my Bobcat 50 pudhrt with a NEW Super tiger .61 ABC.
Broke in the Engine on the plance, used 2 standard props the first 2 to 3 tanks, then used the pusher prop with another 1.5 tanks.
So I take off the prop to verify the direction of prop spin and how it was facing, because the fat edges was turning into the wind, counter clockwise, but my fellow members said that was normal... Soooooooooo what do I discover??

I discovered the BRAND new APC pushe is now loose on the shaft and ovaled to one side; WHAT the HECK?????
> How did a stick'in tight prop even move to get ovaled??? confused???
I used a fairly long 9/16" hand wrench to tight it on the new Great Planes 2-3/4" nylon spinner backing plate???
> Initially I had it bolted on without a spinner and took it off and I think it was fine??? could the nylon spinner backing plate be screwing it up???
-> could it be out of balance, I just borrowed a buddy's prop balancer(non-magnetic one) and will balance it for the first time(I have NEVER balanced a prop, although
I've only flown .15, .25 .40 & .46 engines, this is my first .61

*HELP*
Thanks in advance

P.S. Maiden flight is finally supposed to be tomorrow eve, weather break after 2 weeks, then club picnic sat, so I am scrambling on this last detail???

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Old 09-17-2009, 10:58 PM
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Default RE: Pusher Prop New, but 30 mins later & ovaled out? *Help* What did that?

hard to say.
but if it was tight then you should have no issues.
If you have a new prop balance and put it on. make sure it is good and tight and go fly.
good luck
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Old 09-18-2009, 12:36 AM
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Default RE: Pusher Prop New, but 30 mins later & ovaled out? *Help* What did that?

All I can say, is BALANCE IT FIRST! even if it takes FOREVER! I had one do it cause I got lazy and never balanced it- just threw it in the bow as a spare- (for a pylon racer on a .40 tt pro turning all of 16.5k to 17k. possibly more when unloaded..... The thing ran like crap, and vibrated like hell, ( you could hear the airframe resonating in the air) but it was right before a heat, so I just said to hell with it and flew. it looked like a kidney bean shaped hole for the shaft! I have been flying Giant scale for the past year and a half, or two and learned to not only balance the tips, but to balance the hub as well- been dong it on the glow props since, and they turn faster, and run better!
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Old 09-18-2009, 12:36 AM
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Default RE: Pusher Prop New, but 30 mins later & ovaled out? *Help* What did that?


ORIGINAL: Fledgling


I discovered the BRAND new APC pushe is now loose on the shaft and ovaled to one side; WHAT the HECK?????
> How did a stick'in tight prop even move to get ovaled??? confused???
So, was it loose or tight? It would have to be loose to get "ovaled" out. I doubt out of balance caused this but you should check the balance on your props before using them. I am a little confused also as I never had this problem.
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Old 09-18-2009, 12:50 AM
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lfinney
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Default RE: Pusher Prop New, but 30 mins later & ovaled out? *Help* What did that?

plastic backplate on spinner allowed your prop to spin on the propshaft, it happen frequently, get a spinner with at least a aluminum backplate.
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Old 09-18-2009, 12:54 AM
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Default RE: Pusher Prop New, but 30 mins later & ovaled out? *Help* What did that?

The prop got too hot. If the engine isn't set up right, the crankshaft can grind into the case while the engine runs. To make matters worse, a pusher doesn't blast the engine with cool air, the engine is shrouded somewhat from cool air and the fuel delivery can be more of a problem compared to an "engine first" type plane.
Any single issue or combination of issues could cause the extra heat.
The engine itself could have built up enough fine aluminum slurry to cause a bind on the shaft in the thrust washer / front bearing area. How does the engine feel when you flick the prop? The prop should bounce back and forth a few times after a flick if the engine is fit right and clean.
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Old 09-18-2009, 01:41 PM
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Default RE: Pusher Prop New, but 30 mins later & ovaled out? *Help* What did that?

Yup, loose or hot as Combatpigg stated.



On a pusher plane you also don't use spinners, you tend to use prop lock hubs/locks instead.

I use a double one on my Bobcat to prevent the prop from loosening.

BTW: Aluminum or Plastic, it makes NO difference...

It's NOT a "spinner" issue... spinners should NEVER be in contact with anything other than the MAIN prop hub only close to the shaft.

Too many people have the spinner plastic base in contact with the bottom of the blades, then tighten the prop nut down TIGHT ( as they should ) driving the plastic backward bending and breaking it. They believe that Aluminum prevents this bending back ( it does not, it is somewhat worst! ). Only the central hub must be in contact with the backplate of the spinner.

I've seem many newbies make this mistake, then throw on an aluminum spinner thinking that somehow that will correct the problem.


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Old 09-19-2009, 04:04 AM
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Default RE: Pusher Prop New, but 30 mins later & ovaled out? *Help* What did that?

Wow, you all were great, thanks for the tips....

exciter900rr, yea after this, I guess maybe balance so I borrowed a buddies balancer and the prop was off. I've NEVER balanced a prop before, then again, I've only had .15, .25, .30, .40, .46 and then this is my first .61. BUT I will balance all of them now, even my shock flyer foamies!!!!

Opjose, thanks, but what is a locking hub or whatever it is?

Thanks

P.S. My fellow club member who flies 5 different jet types (from ducted to .91 nitro) took the first attempted maiden flight of my Bobcat.... BUT, about 20 feet off of take off and the engine shutoff, crap.... so she came in for a fairly good landing at fast high AOA landing and bent the landing gear and broke one of those cheap THIN china plastic screws. So, I am frustrated that it shut down, what the heck????
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