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  • Bad Raven: Balance lead extensions are pence from China, I bought bulk. I also cut the old balance plugs with lead off and if I get a broken plug body I just solder a new one lead to lead, can extend at the same time.
    Today at 14:17:22
  • Reman: Bajadre, With reference to balance leads, I bought a cheap JST XH crimper, plus a shed load of male/female plugs and pins a while back. It's amazing how many times that lots come in handy. Not just for repairing battery packs, But for things like adding quick release plugs to wiring harnesses so you can do things like pop gimbels on and off camera drones quickly, Or add plugs to the cables of hardwired components so you don't have to desolder them when you need to get them out of the way in a rebuild, And making charging extension leads so you can get the battery right into a Li-Po safe bag and away from the expensive charger. They're well worth adding to the toolbox..... The other day I only spent about 5 minutes hunting for my 4S charging lead before giving up and making a new one. If I didn't have the crimping kit I'd probabbly still be looking. :)
    Today at 14:00:55
  • hoverfly: Not unusual Reman, they just cant be ar$ed to deliversome if they get behind schedule.. Yesterday i had a delivery by Herpies,  got a sms telling me when they were going to deliver, then rang the door bell and knocked. The parcel was intact and damage free.  Not sure what is going on.... :hmm:
    Today at 13:23:11
  • Bad Raven: Where is it broken?
    Today at 13:22:29
  • hoverfly: If you cut them off make sure  you insulate the ends. :smiley:
    Today at 13:18:42
  • Bajadre: Quick question guys is it ok to snip off a broken balance lead and not run it i know i wouldnt be able to balance charge it again but would the pack be ok ? its a 3s 5500mah which the lead got dragged along the floor on sundays bahs :(
    Today at 12:44:55
  • Reman: About an hour ago I had the Yodel tracking system tell me that I wasn't in...... That's f*ckin' news to me !!!!!
    Today at 10:17:20
  • Reman: Like I said, In the past I've had a handful of packs "Go off" at me like fireworks after bad crashes (Usually with RC helis), So it's hard to get that image out of your head while stripping down Li-Po's. :)
    January 21, 2019, 11:22:54
  • shawdreamer: the horror stories will always incite worry when messing about with Lipo's but its the same as everything else when working on electronics alike, alsong as your careful and methodical there's very little to panic about, I regularly recycle 4s's with a single dead cell into usable 3s packs, end of the days its alot more economical, safer and enviro friendly than having to bin them....just a pain that the dead cell is NEVER one of the outer cells so you always end up having to strip a good cell off to get at the bad cell before putting it back afterwards, its like dropping toast, it'll always land buttered side down and inevitably covered in pet fur :angry:
    January 21, 2019, 00:11:16
  • Reman: Just did the one electrical job that still scares me. I dismantled some Lipo's with knacked cells and built usable packs out of the good cells. I've had packs go "VOOOOOOSH" at me in the past so I'm always slightly scared of having bare lipo contacts anywhere near what I'm working on, But all appears to have gone well and one of them is currently doing a charge/discharge cycle to make sure nothings a miss. :)
    January 20, 2019, 22:28:43
  • Reman: My original Dremel Pro made it to 14 years of heavy weekend use (And abuse) before it crocked. Dismantled that but it turned out to be a "Control module" fault, And Dremel made it ni on impossible to get into that without pooching it completely. :(
    January 20, 2019, 22:17:27
  • ched999uk: BR  ::)
    January 16, 2019, 22:26:54
  • Bad Raven: That's a warrnty claim if ever I heard one....
    January 16, 2019, 20:32:55
  • ched999uk: My 28 year old 12v 35w Weller soldering iron failed  :( I didn't fancy forking out £100 for a new one. Stripped it down and found conductor snapped in cable. 10Mins later all back working great. :smiley: ::) I am very happy!!
    January 16, 2019, 17:23:06
  • shawdreamer: "look up there....its a drone!.....and whats this noise?..... no.....no..... it cant be!....NOOOOOOOO.......OOOOOOOOOOOOOPS I DID IT AGAIN, I PLAYED WITH YOUR HEAR....."
    January 10, 2019, 14:17:24
  • shawdreamer: <starts downloading britney spears albums and preping his large frame to carry a PA system>
    January 10, 2019, 14:15:08
  • Bajadre: defo steveo :) we should get loads of drones together up there so how they handle more that one lol
    January 08, 2019, 19:39:07
  • steveo9007: its all a ploy to get who ever has won the contract for geofencing the airport in, i reckon  ::)
    January 08, 2019, 18:38:26
  • Bajadre: more lies hope they prepped the police staement already lol
    January 08, 2019, 18:27:49
  • Bad Raven: Take Offs resumed
    January 08, 2019, 18:24:45

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Author Topic: 700 nitro pro.. shaking on low throttle  (Read 436 times)

Offline Kez

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700 nitro pro.. shaking on low throttle
« on: June 09, 2018, 00:26:39 »
New toy - I'm told it has been set up and flown. So I bind my tx and set the paramaters, then head off to the field.

Started easy enough, although I think it needs a tune. However the thing thats unnerving me is when i increase throttle everything starts shaking.
I'm wondering, is something bent/unbalanced or is this normal. I mean, does it smooth out if i increase more? I was still on a fairly low throttle - nowhere near enough to take off.

Offline Two-Six

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Re: 700 nitro pro.. shaking on low throttle
« Reply #1 on: June 09, 2018, 11:09:41 »
All RC helicopters do wobble and shake quite a lot initially at spool-up because the blades haven't been pulled out straight enough by centrifugal force.  They don't find their "centers" until they are going at a good speed.  Perhaps your blade bolts are too tight.

A tip for how tight your rotor blade bolts should be.  Tighten them up enough so that they can hold the blade horizontal with the helicopter held sideways BUT will let go of the blade so it falls down vertically when you give the heli a reasonably hard bump. 

How hard a bump?  With small helicopters they should let go with an increasingly hard tap, with a 700 they need to be tighter, so a reasonably hard fist bump is probably about right....

You could try getting a blade ballancer but I am sure your blades will be balanced, no harm in checking.  You might also have a bent main shaft.  Test by removing and rolling on a very flat surface and check for wobbles.

So the heli was set up and flown...hummmmmm :hmm:

Well perhaps it was.  I would recommend you have a very close look at it all before flying it.  Even giving it a good strip down and re-build because you don't know if bolts are tight and thread locked and things are properly lubricated.  You can also have a good look for any damage.

Helicopters should be almost vibration free, so almost no detectable blurring/vibration of the skids or tail at all.  Usually any vibrations will be quite high frequency vibes.

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Offline Bad Raven

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Re: 700 nitro pro.. shaking on low throttle
« Reply #2 on: June 09, 2018, 12:55:03 »
RC helicopter blades like real world Heli's lead true alignment when retreating towards tail and lag when going forwards. It is common for blades to be over tightened and then then this does not happen efficiently. 

Also the blades are balanced and their CG is set during manufacture to be correct at flying head speed under that level of centrifugal force. (particularly true for flybarless blades as their CG differs).

Heli engines/clutches also contribute to the vibration at certain revs below their operating range.

While spooling up you may have mild vibration even when blades are correctly set/tensioned.

The trick is to get through this resonance period asap.

I have been around the heli flying arena for more than twenty years and currently have over 30, around 10 being engine powered, and have just got back from a 3D session at the field with a 230S, which though a great little Heli, isn't great while spooling up!


Offline Kez

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Re: 700 nitro pro.. shaking on low throttle
« Reply #3 on: June 09, 2018, 14:37:28 »

Thanks for the replies people.
I spoke to the previous owner and think I found the issue. Basically I wasn't revving it enough, and using a different fuel it needs a major retune. Then it should pick up better and smooth out.
Previously it was tuned for 40% nitro, but I can't seem to get hold of that now. I'm told we can't buy more than 25% without having a license to store it?

Offline Bad Raven

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Re: 700 nitro pro.. shaking on low throttle
« Reply #4 on: June 10, 2018, 06:30:46 »
If it genuinely was "tuned for 40%" (and that is rare and usually counter productive, making me a little suspicious ) then it will 99/100 have a head spacer/thicker gasket to lower the compression ratio.  Remove this! If it was done by modding other than that they needed their bumps feeling!!

I had years ago a couple of full on competition Heli OS Black head (gold body) engines. These had extremely high compression low nitro set up (as the rules withheld high nitro use), high on both both head and crankcase.

SO high that even a Dynatron starter on 24v had difficulty when the engine was cold in turning it over WITH THE PLUG OUT!!!!

I used to have to spin if over with the plug out and no fuel to friction warm the bore/piston, then fuel it and spin it over, still plug out, then finally replace the plug only half screwed in and get it firing to warm it up, then stop, refit plug properly, and restart. It was fine then for subsequent flights that session.

A right PITA, and done away with asap, though the POWER, OOOOOH the power!! (maniacal laugh)   ::)

Whip the head off, if you find a thick gasket/spacer, or more than one, remove it down to as thin as poss. If it hasn't then pass it on.

Thunder Tiger Redline engines are great, I standardised all my fleet on them after lots of trials.