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T28 Trojan

Old 01-18-2009, 06:57 AM
  #126  
benovisoff
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2-blade. But whos counting?
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Old 01-18-2009, 05:04 PM
  #127  
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Originally Posted by groundrushesup View Post
Yes, I have solved it. Balance your props, even the stock ones. When you put a huge 3-blade 12x8" whomper on and it is out of balance, there is no big mystery why the motor mount gives out. 12x8 is kinda redonkulous from the start for a plane which is typically 30oz AUW, especially one that has such a purpose-built airframe (trainer).

GRU
I am running stock prop and got rid of 50% of vibration by tightening prop adapter but it has a nasty vibration at full throttle that is so severe it threaten to break something.

Based on this thread the suspects include:

1. Motor shaft play (didn't detect any movement)
2. Motor mount problem (didn't notice anything amiss)
3. Unbalanced prop

(or perhaps the combination of minor problems with all three conspiring to create a nast resopnance)

I'll check prop balance but as I recall, I swapped props but still had the same vibration.

The fact that so may people mention vibration with T28 seems to suggest a potential problem with motor mount.



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Old 01-18-2009, 06:27 PM
  #128  
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Its not the prop, because when I uprgaded the stock 9.75X7.75, to a 10X10, still no vibration at all. It didn't occur until I went to a 12X8 on full was the violent shaking. I know the motor mount can't handle thats why it is shaking. An aluminium mount is the way to go. I've seen an 800 watt outrunner with a 60amp esc and 4s 2250 lipo on a trojan that had an aluminium mount, and it took the power without any shaking. Oh, and it was using a 12X10 prop! The aluminium ones are 20 dollars. The cheap plastic ones are the problem. They will break on anything 11 easily.
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Old 01-18-2009, 06:57 PM
  #129  
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Originally Posted by benovisoff View Post
Its not the prop, because when I uprgaded the stock 9.75X7.75, to a 10X10, still no vibration at all. It didn't occur until I went to a 12X8 on full was the violent shaking. I know the motor mount can't handle thats why it is shaking. An aluminium mount is the way to go. I've seen an 800 watt outrunner with a 60amp esc and 4s 2250 lipo on a trojan that had an aluminium mount, and it took the power without any shaking. Oh, and it was using a 12X10 prop! The aluminium ones are 20 dollars. The cheap plastic ones are the problem. They will break on anything 11 easily.

I fear you aren't getting me when I say that you should balance your prop. Yes, another prop did not shake your system until it breaks, so now you can reasonably assume that the 12x8 is off and needs to be balanced.

Do you make a habit of balancing props? Just curious. Previous hints at this likelihood haven't gotten a response so I figured I'd ask directly.

GRU
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Old 01-18-2009, 07:19 PM
  #130  
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It didn't shake with other props because the others props are 10X7s and this is a 12X8. I know its the motor mount. How do you balance a prop?
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Old 01-18-2009, 07:29 PM
  #131  
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Prop balance was not the issue on mine. (Prop was already very close to being balanced. Making it perfect did not help vibration.)

Looked carefully at motor mount and noticed I could flex it by hand more easily in one direction than the other. Snugged up all of the mounting screws and noticed that it was not flexing as much. (50% improvement.)

Powered it up - no horrific vibration! Happy!

Conclusion, flexing in motor mount can definately cause problems even on stock prop in perfect balance. Start by tightening up all of the screws.



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Old 01-18-2009, 07:31 PM
  #132  
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well mine is very secure, and the prop is fine. I think it was only because it was a 12X8 prop it was too much for the mount, so i'll get a metal one so I can have more power without upgrading the motor/esc.
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Old 01-18-2009, 07:45 PM
  #133  
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Originally Posted by benovisoff View Post
well mine is very secure, and the prop is fine. I think it was only because it was a 12X8 prop it was too much for the mount, so i'll get a metal one so I can have more power without upgrading the motor/esc.
BenoBub:: You gotta give up this obsession you've got with that prop!! get you one that'll do better, a 10/6 would fix all your prob's bub, steve PS don't make me mail you one!!!!!!!!!!!!!!!!!!
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Old 01-18-2009, 08:15 PM
  #134  
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alright. I've already been using a 10X7. I'll stick to that. for now....
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Old 01-18-2009, 08:24 PM
  #135  
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Originally Posted by benovisoff View Post
alright. I've already been using a 10X7. I'll stick to that. for now....
BenoMaticBub::I'll poke though my old Big props an see if I gotta a lower pitched 12/something for you, (PM you if I can) your bub, steve
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Old 01-18-2009, 08:26 PM
  #136  
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Wait no. The problem with the vibration was too much power with a 12. I already have a 12 and it is the problem. It doesn't vibrate with a 10
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Old 01-18-2009, 08:29 PM
  #137  
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this will work Too!!bub steve EP1147 11x4.7 $1.65 http://www.gwsprops.com/gws_spinners.htm
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Old 01-18-2009, 08:33 PM
  #138  
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I have been looking at a smaller pitch 11. But its the power, not the speed that is the issue. My adapter is apc. your bub, ben
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Old 01-19-2009, 12:38 AM
  #139  
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I am using a round piece of wood that is glued on and a E-flite 480 and zinger 11by7 prop.
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Old 01-19-2009, 12:42 AM
  #140  
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how does that work?
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Old 01-19-2009, 05:15 AM
  #141  
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A lot of spacers and long screws.
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Old 01-19-2009, 05:18 AM
  #142  
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I'll go with the sure fire aluminium one, but thanks
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Old 01-19-2009, 12:00 PM
  #143  
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Originally Posted by son of alpea42 View Post
A lot of spacers and long screws.


http://www.hobbycity.com/hobbycity/s...idProduct=4689
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Old 01-19-2009, 09:07 PM
  #144  
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Today I drainde 3 more lipos on it. Went great. Today was a big day in the testing of its aerobatics, strength, and what it can do under what speeds. I tried to do some snap rolls. it can take off fairly slow, and it can fly with its nose up at 70 degress and full throttle and inch forward slowly. It is pretty sound. The wings do give a little with a big prop and fresh full lipo on full throttle when pulling out of a dive . All is well and aluminium mount should arrive this coming weekend.
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Old 01-19-2009, 10:05 PM
  #145  
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I bought that mount, but because I wanted to use the radial mount for the prop on the trojan it didn't work. Gonna try it on my Mustang with the 35-36B though.
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Old 01-19-2009, 11:44 PM
  #146  
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I'll get an aluminiun one, except the guy who is making it only makes it for 480s and I want a neo 10.
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Old 01-22-2009, 11:47 PM
  #147  
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Now things are going wrong. it flips on perfect landings, the nose gear is weird, It stays left or right, it flies like its NOSE heavy yet it isn't, and it is just starting to get weird. this always happens to me. I need a power 10 or neo 10 because it needs full throttle just to stay upint the air, yet it can't maintain airspeed.
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Old 01-22-2009, 11:57 PM
  #148  
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Originally Posted by benovisoff View Post
Now things are going wrong. it flips on perfect landings, the nose gear is weird, It stays left or right, it flies like its NOSE heavy yet it isn't, and it is just starting to get weird. this always happens to me. I need a power 10 or neo 10 because it needs full throttle just to stay upint the air, yet it can't maintain airspeed.
1. Sounds like something in the steerable nose is either slipping or stripped.

2. What kind of surface are you using for your "perfect landings"

3. Regarding power -

a. does this happen on more than one battery? (Could be battery problem.)

b. is the motor or ESC getting hot?

c. are the flight times also short

d. Any chance you put the propellor on backwards? (it happens)
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Old 01-23-2009, 12:26 AM
  #149  
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Originally Posted by cbatters View Post
1. Sounds like something in the steerable nose is either slipping or stripped.

2. What kind of surface are you using for your "perfect landings"

3. Regarding power -

a. does this happen on more than one battery? (Could be battery problem.)

b. is the motor or ESC getting hot?

c. are the flight times also short

d. Any chance you put the propellor on backwards? (it happens)
I land on a paved basketball court
this happens with all my motor, esc, and battery combos I've tried
flights are 8-9 min with a 2100mah
prop numbers are facing forward
and the motor and esc do get warm but not hot enough
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Old 01-23-2009, 01:02 AM
  #150  
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Originally Posted by benovisoff View Post
I land on a paved basketball court
this happens with all my motor, esc, and battery combos I've tried
flights are 8-9 min with a 2100mah
prop numbers are facing forward
and the motor and esc do get warm but not hot enough

Sounds like you are having the same problem I was having - more powerful motor on the same thrust offset.

With my 35-36C and a 11x5.5, it was super squirrely and would tuck under to the right in a dive, dutch roll at the weirdest times, and generally it was a handful. It was disconcerting because it was such a great flyer out of the box.

I put the stock motor and prop back on and it flew great again - until nature decided to mace me and I crashed. I think the stock offset is far too much right and perhaps a little too much down for the powerful motors we are using.

[media]http://vimeo.com/2917783[/media]
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