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Old 01-30-2008, 04:42 AM   #301
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Hi Bob.

If you are laughing at me, I was definitely not trying to "get as much as possible" - but the correct amount of gyro gain. My tail wags just a little, so I believe it is time to turn down the gain, from the initial recommended setting of 74% on the DX7.


Best regards

Peter
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Old 01-30-2008, 04:45 AM   #302
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Bob,
the text on the user guide actually continues and covers exactly what you just mentioned>

It is not uncommon to find that the optimal gain value for a helicopter may be a small number such as 35-45%. The small value does not mean that the gyro will be limited in performance. Any gain value performs well as long as it is the optimal gain value. However, a gain below 35% indicates that the mechanical gain of the tail is too high and it is therefore recommended moving the servo arm ball link further in. Similarly if 100% is reached and no tail wagging is seen the ball link needs to be moved further out and repeat the gain adjustment procedure.

Also on a related topic - the mounting of the ball link on the servo arm - which affects the mechanical gain>

We recommend that the ball-link is mounted 13-17mm from the servo shaft unless a different distance is deemed essential for a particular helicopter. Ultimately, the most important factor is the servo travel which ideally should be around 45 on either side of the mid-point (+/-15%). For most servos this will result to gyro endpoints in the range 85-115%. This combination gives a good balance between tail pitch correction speed and available torque. If the servo travel or endpoints are significantly different than this recommendation you may wish to change the ball-link position to restore this balance.

-Angelos
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Old 01-30-2008, 04:51 AM   #303
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Quote:
Originally Posted by psindrup View Post
Hi Bob.

If you are laughing at me, I was definitely not trying to "get as much as possible" - but the correct amount of gyro gain. My tail wags just a little, so I believe it is time to turn down the gain, from the initial recommended setting of 74% on the DX7.


Best regards

Peter
Peter the DS gyro works a bit differently than others I have used. Too high a gain shows it in down wind flight before it shows it in just hover conditions. If your getting wag in hover then yea it's too high but also watch how the tail works when it is into the wind as you can get a wag if gain is still too high.

BTW no I was not laughing at you! I was laughing when Angelos posted that topic and the laugh was agreeing with him!

So you know on my Nitro600 with 9256 servo I am running 24% gain! YES that low! but the tail is a rock! Don't over work your tail servo by thinking a higher gain is needed!

Bob
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Old 01-30-2008, 05:02 AM   #304
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Hi Bob

Thanks for clearing that out.

I was hovering in pretty windy conditions (for me at least) and I definitely saw some wagging.

Now I have to go back to school to check how the gain is calculated with regard to the "50% mid point" reference on the DX7

Peter
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Old 01-30-2008, 05:08 AM   #305
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Quote:
Now I have to go back to school to check how the gain is calculated with regard to the "50% mid point" reference on the DX7
Thats easy Peter... JR (DX) works like this
X = gain
(50-X) x 1.44 = true gain

so lets say you have 70 in your gyro menu on the DX.
70-50 = 20
20 x 1.44 = 28.8 or 29% gain in the rounding.

Futaba radios dont do this and if your usng GEAR end points on the DX instead of the gyro menu, it is more 1 to 1 (but not quite). OK?

Make sense?

Bob
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Old 01-30-2008, 07:31 AM   #306
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Hi Peter for A500 DS760 DX7 heres some good numbers to start from. DX7 Align 500 with Futaba 9257 my gain in Tx is 38% Servo horn length is about 10mm.

Start with you rudder endpoints set around 90% for a managable piro speed and increase decrease to suit.

cheers Brian
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Old 01-30-2008, 08:11 AM   #307
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Quote:
Originally Posted by Finless View Post
Thats easy Peter... JR (DX) works like this
X = gain
(50-X) x 1.44 = true gain

so lets say you have 70 in your gyro menu on the DX.
70-50 = 20
20 x 1.44 = 28.8 or 29% gain in the rounding.

Make sense?

Bob
That makes a lot of sense! :wink:

Having my DX7 set to HH = 74% makes my true gyro sense:

74-50=24x1,44 = 35% true gain

Compared to your setting of 24% on your T-rex 600, it seems quite a bit to high.

New setting: (25/1,44)+50=67%

Peter
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Old 01-30-2008, 08:13 PM   #308
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RC Helicopters 101 should be given in high school so we don't bust our brains with all the super education we need just to BEGIN to understand this stuff. Oiy!
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Old 01-31-2008, 02:28 AM   #309
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Quote:
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RC Helicopters 101 should be given in high school so we don't bust our brains with all the super education we need just to BEGIN to understand this stuff. Oiy!
Or put another way. If we had listened in high school, we wouldn't have such a hard time understanding this stuff now.

Peter
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Old 01-31-2008, 06:14 AM   #310
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The manual states 'To fly in rate mode set the linkage lengths for approximately 8 degrees tail pitch in the direction that compensates the main rotor torque'.

Does that mean that this adjustment is not required for AVCS flying? TREX 500 manual states setting the tail pitch at 0 degrees when tail servo horn is at 90 degrees, so you get full travel of the pitch slider left and right. If I set the pitch on the blades to 8 degrees while the servo is at 90 degrees, won't there be less throw on that side? Could someone explain why you can't just leave the blades at 0 degrees pitch while the servo horn is at 90 degrees.

Cheers
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Old 01-31-2008, 07:08 AM   #311
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In AVCS mode, the gyro is going to push the blade pitch to about 8 degrees anyway, so there's no throw advantage either way. The only way you'd gain greater throws is if the blade grips could be adjusted to have 8 degrees of pitch when the pitch slider is at center.
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Old 01-31-2008, 09:21 AM   #312
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Quote:
Originally Posted by leeph View Post
The manual states 'To fly in rate mode set the linkage lengths for approximately 8 degrees tail pitch in the direction that compensates the main rotor torque'.

Does that mean that this adjustment is not required for AVCS flying? TREX 500 manual states setting the tail pitch at 0 degrees when tail servo horn is at 90 degrees, so you get full travel of the pitch slider left and right. If I set the pitch on the blades to 8 degrees while the servo is at 90 degrees, won't there be less throw on that side? Could someone explain why you can't just leave the blades at 0 degrees pitch while the servo horn is at 90 degrees.

Cheers
You only need the 8deg adjustment if you want to run in rate mode. However, keep in mind that if rate mode is not set the heli may piro uncontrollably if you accidentally switch to it in flight.

Regarding the recommendation in the helicopter manual, there is no need for the left and right throws to be perfectly symmetrical but see if you can keep them within +/-15% as the user guide suggests. As long as full pitch can be reached on both sides the gyro will work fine.

-Angelos
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Old 02-05-2008, 10:56 PM   #313
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What is the best method of measuring the tail blades to 8 degrees? From the 200 size heli's to the 90 size helis. Is there a common way to measure the tail blades?
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Old 02-05-2008, 11:34 PM   #314
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Quote:
Originally Posted by Sam2b View Post
What is the best method of measuring the tail blades to 8 degrees? From the 200 size heli's to the 90 size helis. Is there a common way to measure the tail blades?
Here is an outline of a blade at 8 degrees. Scale it, print, and cut it out and hold it next the boom and blade. You'll be amazed how well your eye can pick up the angle.
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Old 02-06-2008, 01:40 AM   #315
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Thanks, Bruce. How did you ensure this image is 8 degrees? (for curiosity's sake)
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Old 02-06-2008, 01:51 AM   #316
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I used Paint Shop Pro and typed in 8 degrees rotation on a section containing the shape.
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Old 02-06-2008, 08:46 AM   #317
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I bought the USB interface cable and can't get it to work in either Vista or XP; I have downloaded and installed the drivers about 10 times but windows keeps telling me it's an unknown device - what am I doing wrong??
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Old 02-06-2008, 06:01 PM   #318
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Just got my ds760 today from revolution models. I know it will have been worth the wait : )

Regards

Fergus
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Old 02-06-2008, 08:14 PM   #319
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Wondering if the metal plate is needed/recommended on a Trex600E. I was happy to find that the gyro itself is quite a bit lighter than the 401 it's replacing, but with the addition of the plate it seems heavier. My bird is slightly tail heavy so it would be nice to lose the weight, even if small, but not at the expense of gryo performance. Anyone else running one on a 600E yet and did you use the plate?

Thanks, can't wait to fly this thing.
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Old 02-06-2008, 11:00 PM   #320
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Just installed my second DS760 in my Trex 600, both were purchased from Mark Webber. Thanks again Mark. my first one I installed was in the Trex 500. I used the Align pitch gage set for 8 Deg. and sliped it over the tail rotor and aligned the edge of the gage paralell to the boom..
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