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| General RC Aircraft Discussion Discuss anything RC related |
Topic Review (Newest First)
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| 09-03-2012 08:33 PM | ||||||
| uberjay |
Re: Prop/Spinner/Prop NUT balancing? Quote:
 - but I did well with it. Now, I'm into whatever I can get my hands on. I like scale stuff, but I also like slapping together $ foam planes with my girls (9 and 12). Basically, I like the creative and building processes. The icing on the cake is watching a creation actually fly. Oh, and it doesn't hurt to see my girls at the sticks! LOL Quote:
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Cheers, J |
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| 09-03-2012 08:14 PM | ||||||
| Cougar429 |
Re: Prop/Spinner/Prop NUT balancing? Sounds like you're back into the hobby full time now. Get ready!!!!!! I found on a lot of those planes the tendency to nose over on grass can be pretty bad. Part of the problem is tire size as many seem to be designed for much smoother surfaces. I taught a friend how to fly and have the giggles of doing the maidens and many flights on all his craft. As we both are into WWII and scale that means Mustangs and Corsairs for him. Every one of his Mustangs are a bear on grass until the gear is bent far enough forward, (ahead of the leading edge is about right for grass). The Corsairs are a bit easier since they run larger wheels, but takeoffs and landings can be a bear if the toe in is not set correctly. If you have to keep the tail down to maintain tracking it usually means something is off and you also run the risk of the plane launching far too early, before adequate flying speed is reached. Even Rare Bear is a handful on grass and would nose over at the slightest opportunity. During the rebuild I too followed the same procedure and have the gear tilted forward when extended. Once the fuse is finished I'll see if that improves. Part of the problem is the fact with relatively tall gear the wheels move further aft in relation to the CofG when the plane is level, sometimes to the point where it is teetering directly atop the wheels. Add drag from grass ops and unless you are on top of it a nose over is almost a given. Personally I find grass a bit more forgiving when it comes to taildraggers. Perhaps it's just my own experience. The Harvard has that geometry right out of the box and excepting some other issues has rock solid ground handling. Now if I can just get it to land right.................. I'll likely have a table again at the London Swap Meet. Perhaps we can get together. Oh yeah, are those servoless retracts? I have upgraded all my retract setups to them and have another set for the Zero heading onto the build board this fall or winter. After all the fun with servo driven mechanicals have to say they are a very welcome improvement. |
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| 09-03-2012 06:03 PM | ||||||
| uberjay |
Re: Prop/Spinner/Prop NUT balancing? Quote:
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just for the takeoff and landing. Yeah, I know a tail heavy plane usually flies only once.... but man it's embarassing nosing over on a takeoff! LOL.Quote:
 . Maybe this fall I'll pull it out.Thanks for the tips. J |
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| 09-03-2012 05:41 PM | ||||||
| Cougar429 |
Re: Prop/Spinner/Prop NUT balancing? Nice looking setup. Glad you were able to solve it. Personally I have never had too much trouble from spinners until I got up into the 3" and up diameters. Does that have retracts? Unfortunately, other than moving the heaviest components, which in this case is likely the main battery, there may not be much to compensate for tail heaviness. As you report you've already successfully flown this one I think you have that one solved. I've had to deal with some real winners recently. The TT Rare Bear is horrendously tail heavy out of the box and my moving the elevator servo back there did not help any, (this was to eliminate the source of tail flutter and failures so common on this model). The GP F-15 was just the opposite and the servos and flight pack are as far aft as possible, (basically right at the tail). Even went as far as relocating the fuel tank to the CofG as a full tank would likely have make it impossible to take off or fly. |
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| 09-03-2012 03:02 PM | ||||||
| uberjay |
Re: Prop/Spinner/Prop NUT balancing? Success! (Finally  )After spending an hour or so balancing the back plate first (on the magnetic, Great Planes, balancer) and then the plate + cone on the DuBro balancer I am now able to throttle up to full with no ugly harmonics / vibrations creeping in. Thanks to all who pitched in with ideas! Attaching a couple pics of the plane. Cheers, J |
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| 09-02-2012 07:37 PM | ||||||
| uberjay |
Re: Prop/Spinner/Prop NUT balancing? Quote:
I'll check just in case. Thanks, J |
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| 09-02-2012 07:36 PM | ||||||
| uberjay |
Re: Prop/Spinner/Prop NUT balancing? Quote:
Note, the vibration was nonexistent with the same nut + prop and without the spinner. Quote:
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.... bringing back my engineering school days. Now, I was electrical, but they still made us do some mechanical and structural stuff. The answer to your question is that, yes, the vibrations with the spinner subsided completely by the time I was at about 3/4 throttle and beyond. So likely the spinner was vibrating at a certain frequency throughout and at/about 1/2 throttle I hit the harmonic and it became noticable. Thanks. Quote:
.Anyway.... thanks again for your input. I'm going to proceed with balancing the spinner better and will double check the prop too for good measure. J |
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| 09-02-2012 07:02 PM | ||||||
| groo |
Re: Prop/Spinner/Prop NUT balancing? Possibly loose or flexing motor mounts? Happened to me with the fun cub. |
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| 09-02-2012 06:29 PM | ||||||
| Cougar429 |
Re: Prop/Spinner/Prop NUT balancing? I would think the prop nut not likely to be the culprit here. Did you balance the prop laterally as well as longitudinally? Production props can have the center hole off the true axis or differences during manufacture can throw it off in more than one direction. Follow a true balance procedure and check the prop remains stationary throughout a full rotation. If it tries to rotate at any point then it is still off balance. Having said that I need to ask if you increased above the 50% throttle mark and what reaction occurred. Reason for this is if the vibrations settled down then you likely still have a prop imbalance, but at the 50% throttle mark your frequency hit the natural resonance of the airframe. This is true of any structure and why vibrations may seem so much worse at certain frequencies, (or rotational speeds, RPM if so inclined). With so many moving parts of great mass in real helis the chance for vibrations can be extreme and destructive and why designers try to set different parts of the structure to resonate at different frequencies. Along with lessening the chance of a resonance starting and building to destruction, having the other parts of the structure resonate differently can dampen them out. Our aircraft are just as likely to do this, just the structures are able to tolerate them better. |
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| 09-02-2012 04:17 PM | ||||||
| uberjay |
Re: Prop/Spinner/Prop NUT balancing? Thanks... my eyes are open now and I can confirm that I've used this prop nut and the 3 blade prop (balanced) before. So I think I have my answer - back to the drawing board with the spinner.I think I'm going to balance the spinner back plate on my magnetic balancer and then combine it with the cone on the DuBro balancer. Eliminate at least one variable. Thanks for helping me bounce this around - one of those things that if you talk (type) it out it sometimes starts to make sense. Cheers, J |
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