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Old Aug 02, 2012, 09:37 PM
Look ma, no hands!
1Pilgrim's Avatar
United States, WI, Sheboygan
Joined Aug 2011
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Originally Posted by installerblizz View Post
Just to clarify - when you guys say you have cut your blades 10mm, you do mean that you cut 10mm off each blade, for a total rotor diameter reduction of 20mm?
Yes. But you might want to start with 5mm per blade and work your way up. Balancing and tracking the blades is important too.
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Old Aug 02, 2012, 11:00 PM
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United States, MS, Tupelo
Joined Jun 2012
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Originally Posted by 1Pilgrim View Post
Yes. But you might want to start with 5mm per blade and work your way up. Balancing and tracking the blades is important too.
Thanks! I actually trimmed 10mm off each about a week ago. I have since balanced them, the flybar, and tail rotor. The ability to fight wind is like night and day. Before I was hesitant to fly when there was any wind but now 15 mph winds are manageable. It's a challenge, but it only serves to build my skills. I did miss the loss in lift at first, but I installed the Xtreme motor today and now have a Hyperion 25C battery and the lift seems back about what it was before the blade trimming. I did develop some mild tail wag (1/4 inch back and forth every second or so), but trimming 7mm (total) off of the tail rotor eliminated it completely, after balancing of course. This is exactly what I wanted out of a heli. I came from a V911 and wind was its nemesis.
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Old Aug 02, 2012, 11:11 PM
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St. Louis, Mo.
Joined Jun 2008
394 Posts
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Originally Posted by 1Pilgrim View Post
See post #14516. Also, does the drift occur on takeoff or does it persist or start up again after you achieve stable hover?
More so after it reaches a stable hover. Has some drift right off the bat getting off the ground, but mostly after that.
Nice vid in the house. Hovering like you did is my goal.
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Old Aug 03, 2012, 08:19 AM
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United Kingdom, Oxted
Joined Dec 2011
426 Posts
What really surprises me with the 120sr is how small the tolerances are. Mine has been wobbling very slightly and the tail was quivering in flight. I could see nothing wrong whatsoever.

Today, I tried different tensions on the blade grips and I found that there was a 'sweet spot' but the quiver was still (just) there. Tightening and loosening the grips made the blades track a little better.

Then I replaced the flybar. The new one could spin in a table mat and the old one wouldn't. So little difference, it couldn't be seen. (No oval shape in the middle of the old one)

I fitted the new one anyway and the heli now hovers smoothly!! We're talking gnat's differences here so those tolerances are pretty critical to get it to fly smoothly to say the least.
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Old Aug 03, 2012, 09:13 AM
Look ma, no hands!
1Pilgrim's Avatar
United States, WI, Sheboygan
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Originally Posted by iancraig10 View Post
What really surprises me with the 120sr is how small the tolerances are. Mine has been wobbling very slightly and the tail was quivering in flight. I could see nothing wrong whatsoever.

Today, I tried different tensions on the blade grips and I found that there was a 'sweet spot' but the quiver was still (just) there. Tightening and loosening the grips made the blades track a little better.

Then I replaced the flybar. The new one could spin in a table mat and the old one wouldn't. So little difference, it couldn't be seen. (No oval shape in the middle of the old one)

I fitted the new one anyway and the heli now hovers smoothly!! We're talking gnat's differences here so those tolerances are pretty critical to get it to fly smoothly to say the least.
+1 And it's a moving target - the helicopter is such a dynamic machine that it seems SOMETHING is always going awry. After more than a year flying just two types of helis (two MCX2's and one 120 SR), chasing that elusive "sweet spot" is what keeps me interested.

btw what does "spin in a table mat" mean?
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Old Aug 03, 2012, 09:53 AM
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United Kingdom, Oxted
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Sorry - me and words - spin ON a tablemat. 'O' and 'I' are so close to each other on the keyboard. Solly me.

The old one was slightly curved for some reason. More on one half than the other and it was barely noticeable. The only reason I saw it was the fact that I spun the new one on a tablemat and it spun freely. The old one didn't which pointed out that it wasn't actually flat.

Also, the blade grips were not at the same tension so one of the blades was rising slightly higher than the other, resulting in a slight imbalance.

The thing is, these adjustments are so minute each time but they do make a big difference to the hover in particular.

I put it all back together with its new flybar this afternoon and gave it a spray with a silicone lubricant.

I feel as though I have a new heli; especially now I have the Extreme canopy on as well!!
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Old Aug 03, 2012, 02:18 PM
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Originally Posted by 1Pilgrim View Post
Just to be clear...

Drifting can be cured either by adjusting the mechanical linkage or by dialing in some trim with the tx.

The tendency to roll to the right in forward flight is not caused by the heli "lean"-ing; it's caused by asymmetrical lift. The rotors turn clockwise when viewed from above; in forward flight the blade on the left side of the heli is moving through the air faster than the blade on the right. Faster blade = more lift. More lift on left = roll to the right. Mixing aileron (roll) in proportion to stabilizer (pitch) counters the extra lift so the heli flies straight ahead (or at least follows its nose) in fff.

Remember, hovering into the wind is the same thing as flying forward. Depending on the amount of wind you will end up with some asymmetric lift from the relative airspeeds of the blades on different sides of the rotor. If you adjust the aileron mixing based on stick position you may not get enough aileron compensation in this situation.
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Old Aug 03, 2012, 06:06 PM
Look ma, no hands!
1Pilgrim's Avatar
United States, WI, Sheboygan
Joined Aug 2011
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Originally Posted by ssobol View Post
Remember, hovering into the wind is the same thing as flying forward. Depending on the amount of wind you will end up with some asymmetric lift from the relative airspeeds of the blades on different sides of the rotor. If you adjust the aileron mixing based on stick position you may not get enough aileron compensation in this situation.
Excellent point. I had the best results adjusting the mixes (AILE > ELEV & RUDD > THRO) in the gym last winter.

Of course I have to use completely different settings (a different tx model actually) when flying in confined spaces.
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Old Aug 03, 2012, 09:41 PM
NotAnotherMomentLostToSei zures
Chap1012's Avatar
United States, MA, Malden
Joined Mar 2008
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Blade grip tension

How tight is too tight? I have found that tips passed off to me I try to pass off to you.

Tighten the blade screw tight enough where it will hold both blades horizontal to the floor, nose of heli pointed downward. Now, with a slight "downward jerk" the blades will fold down. That's how I adjust my "blades to blade grips."

This is how I do my 120SR and V4 folding blades.

Mike.
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Old Aug 04, 2012, 06:44 AM
Always, against the wind
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United States, IL
Joined Oct 2011
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Quote:
Originally Posted by 1Pilgrim View Post
Excellent point. I had the best results adjusting the mixes (AILE > ELEV & RUDD > THRO) in the gym last winter.

Of course I have to use completely different settings (a different tx model actually) when flying in confined spaces.
Do you mind posting the settings?
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Old Aug 04, 2012, 10:13 AM
Look ma, no hands!
1Pilgrim's Avatar
United States, WI, Sheboygan
Joined Aug 2011
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Originally Posted by Thetis View Post
Do you mind posting the settings?
If you haven't already done so I highly recommend that you download Mr. Salt's "e-guide for the MSR and 120 SR". It includes a lot of tips and tricks for these two helis, including settings for the dx7 and dx6i. You can download it as a pdf file (the only way to get it) for about $9 at

www.rchelicopterfun.com
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Old Aug 04, 2012, 10:29 AM
Always, against the wind
Thetis's Avatar
United States, IL
Joined Oct 2011
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Quote:
Originally Posted by 1Pilgrim View Post
If you haven't already done so I highly recommend that you download Mr. Salt's "e-guide for the MSR and 120 SR". It includes a lot of tips and tricks for these two helis, including settings for the dx7 and dx6i. You can download it as a pdf file (the only way to get it) for about $9 at

www.rchelicopterfun.com
Thanks, heading there
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Old Aug 04, 2012, 04:47 PM
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United States, TX, Houston
Joined Aug 2011
637 Posts
I tell ya. for as many "Mr Salt" books we have sold here, we should be getting a commission
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Old Aug 04, 2012, 06:13 PM
Look ma, no hands!
1Pilgrim's Avatar
United States, WI, Sheboygan
Joined Aug 2011
1,252 Posts
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Originally Posted by Blackanthem View Post
I tell ya. for as many "Mr Salt" books we have sold here, we should be getting a commission
I'm just glad to see so many people having a good experience with the 120. Mr. Salt kept me from dropping the hobby altogether! Well, him and Mike of course...
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Old Aug 04, 2012, 10:37 PM
Rockin' & Flyin'
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Virginia Beach
Joined Dec 2009
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John Salt answered my emails when I didn't know anything what I was doing. I owe him, too, for eliminating my frustrations.
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