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11-22-2006 04:05 PM  11 years agoPost 1
asong26

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VA

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Hi guys,

I finally found a gyro servo horn / arm that fits @ perfect 90 degree angle without any modification, and in a process of recalibrating my gyro / tail push rods. So here's the question:

I am calibrating servo using Normal mode on both the Gyro and the Radio. I've adjusted the short push-rod (on the servo arm) so that the bell crank that is attached to the heli's main body and the servo arms are perfectly parallel (vertically at 90 degrees) at neutral. Next comes the longer push-rod adjustment to make sure that at neutral the the tail pitch slider is sitting at the correct position.

With the motor off, and everything at neutral, should my tail blade have any pitch? Currently at neutral, my tail pitch slide sits closer to the tail gear box, rather than sitting in the middle.

Since when the motor spools up, and the gyro will begin add pitch to the blades to keep it steady, it should have some pitch shouldn't it? Or does that affect my equal tail movement during flight?

Here's my current setup:

Carbon Pred w/ tail bell crank (2 push rods control the pitch sider)
GY611
Tail Metal Gear Box
120mm tail blades.

Any thoughts?

Andrew

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11-22-2006 04:19 PM  11 years agoPost 2
JuanRodriguez

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The Villages, Florida

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asong26,
Many manufacturers will design their pitch slider system so that when the pitch slider in center travel, there is a few degrees of pitch on the blades to compensate for the torque of the main rotor.... If the t/r blades were at 0 pitch in hover, the a heli with a clockwise rotating head would spin counter clock wise because of the lack of offset to the t/r blades....

So, not to confuse you, it would not surprise me to see your pitch slider offset a little in one direction or the other (depending on heli brands) when everthing else is at neutral....

If you took your blades and folded them together as much as possible, you should be able to measure about 30 mm's between the blade tips..... that's a good starting point to get you into the ball park.... the rest of any adjustment to your pushrod will be made after you've had a chance to hover to see whether to make the push rod longer or shorter.... Generally with a HH type gyro, the drift adjustment should be made by altering the length of the push rod and NOT with the trim slider on the radio....

Hope all of this helps...

PS- having your slider "offset" a little as you describe is no problem...... There is more pitch range in the whole system than you will ever use...

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11-22-2006 04:24 PM  11 years agoPost 3
bwarkent

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Houston Tx

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I don't have any experience with the 611 gyro but I do know that you can adjust the end points independently in both directions with it. You won't lose travel by centering the servo with slight pitch on the tail with that gyro. Now if you were running the futaba 401 gyro then the slider would need to be centered or you would lose travel in one direction.

As to the benefits of having pitch with the servo centered, for the head you center all the linkages for zero pitch and servo horns at 90 degrees so you have equal rates of head movement in both directions from 0 with the rotation of the servo wheels. It seems to me you would do the same on the tail. My vote is pitch slider centered with 0 pitch and control horn at 90. I am not into 3D yet so if anyone has good reason to do it the other way I'd like to hear it.

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11-22-2006 04:37 PM  11 years agoPost 4
asong26

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On the predator, with the pitch slider centered, you will have a pitch. Zero pitch on the pred, at least on my heli the pitch slider sits on the tail box side of the output shaft...

I guess the more I think about it, this makes sense, since the tail will be compensating for the rotational spin.

I guess the big question is, what is the what is the correct trade off for all 3 flight conditions, and assuming that my max main rotor speed will be around 1900 - 1950 @ idle-up 2....

I guess I'll just have to mount it on the Rotopod and test it out, since the pod has a free spinning mount.

Andrew

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11-22-2006 06:34 PM  11 years agoPost 5
JuanRodriguez

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Andrew,
Do as I suggested in the above post and you'll be OK for any flight condition....

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11-22-2006 06:40 PM  11 years agoPost 6
asong26

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Juan,

Can you clarify the blade tip to tip(30mm) relationship with the pitch. Shorter vs. longer, what effect does it have. Do you mean the difference in distance from one another from a pitch stand point? Or do you mean just simple straight line distance between the two?

My tail blades are 120mm size. I would like to learn how I can use this distance relationship calibrate my push-rod for correction length and positioning.

Thank you.

Andrew

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11-22-2006 07:21 PM  11 years agoPost 7
JuanRodriguez

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The Villages, Florida

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Andrew,

The "30 mm" distance between the blades is an old setup tip from many years ago. I believe that is the measurement Miniature Aircraft (Xcells) used in their setup manuals.....

It still works today and seems to work with every brand heli I've owned. Reason being is that the 30 mm measurement is actually setting the hover pitch of your tailrotor blades without the use of a pitch guage....

Turn your radio system on and let the gyro initialize per the gyro directions.... Then fold the rear blades toward each other. The blade grips will not permit the tips to touch so fold them as far as you can. Measure the gap that you see between the two blade tips...... If the measurement is not approximately 30mm (STRAIGHT LINE DISTACE MEASURED FROM TIP TO TIP), pop off the control rod and lenghthen or shorten the push rod until you get the desired 30 mm. If you followed the mfg's setup instructions you may be very close already...

What you are accomplishing in essence is to set the tail rotor pitch to about 7 or 8 degrees pitch.... IN THE DIRECTION that will counteract the torque of the main rotor.

Don't go to crazy trying to get exactly 30 mm.... that is a starting point that will get you very close. The "fine tune"
adjustment you will make when you hover the machine...

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11-22-2006 08:08 PM  11 years agoPost 8
asong26

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Juan,

That clears it up. Thanks for the tip, and detailed explanation. I will give it a try.

Andrew

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11-22-2006 10:11 PM  11 years agoPost 9
JuanRodriguez

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The Villages, Florida

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No problem... glad to help.

Feel free to also PM me if you need any further help...

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11-23-2006 02:26 AM  11 years agoPost 10
asong26

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I've just posted this in the radio forum...., but maybe I'll get a quicker response here...

---------------------------------------------------------

Quick question regarding the centering of the servo. I am using GY611, w/ 14MZ.

In order to find the perfect center of the gyro servo, I've set it to Normal Mode on both the Gyro, and the Radio.

On the radio, I've also put the gain to 0%. From what I understand, this is where it needs to be to find that perfect center.

The question is, do I need to do set the gain to 0% on the Gyro as well?

Or does any of this matter on the 14MZ, since it offers servo neutral test? Just want to make sure that I have the correct settings, since I spending a lot of time calibrating this thing, and would hate to find out that my settings were wrong for calibration.

Thanks

Andrew

Andrew

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11-23-2006 01:59 PM  11 years agoPost 11
JuanRodriguez

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The Villages, Florida

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The question is, do I need to do set the gain to 0% on the Gyro as well?
If it makes you feel better you can, but gyro gain has nothing to do with servo centering.......

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11-23-2006 02:35 PM  11 years agoPost 12
asong26

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Thanks Juan!

Andrew

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11-23-2006 04:28 PM  11 years agoPost 13
Wayne Mann

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United States of America

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Hi Guys,

I didn't read every post so some of what I am going to suggest may have already been mentioned.

When the radio is booted up the tail rotor servo arm and the tail rotor push rod should make an exact 90 degree angle. Like some have said adjust the tail rotor push rod so that the tail rotor pitch slider bell crank is also 90 degrees to the push rod. This is just a starting point as you have to mechanically flight trim the tail rotor once the model is in flight.

Now that you have the model ready to fly make sure that you can flip a switch and go from heading hold to normal gyro. The model should hover at half stick. With the model hovering flip from heading hold to normal gyro and be careful and ready to flip the switch back as the tail rotor may be considerably out of trim. When you flip into normal mode the tail rotor should be very close to being perfectly timmed. If not land the model and adjust the tail rotor push rod and try again. Continue doing this until the model will sit timmed in a hover in normal mode. This is an important step because if the tail rotor is too far out of mechanical trim it will effect the gyros ability to hold the tail in heading hold.

Once you have completed this task adjust the end points in the gyro so that the tail rotor servo doesn't bind up at either end when you give full tail rotor throw in either direction.

I hope this helps

Wayne Mann

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11-23-2006 04:43 PM  11 years agoPost 14
asong26

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Thanks Wayne Mann,

I have the vertical alignment of the horn and bell crank set at perfect neutral position of the servo. You're the difficult part is the correct length of the tail push-rod (long one).

Based on your you're saying, I should set my Gyro to CMT mode, and on my radio use Heading Hold mode for the take off. Once the tail is holding, I need to set it to normal mode while hovering to see if the tail still holds, if not land it and mod the tail boom length and try again?

Andrew

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11-23-2006 05:04 PM  11 years agoPost 15
Wayne Mann

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Hi Andrew,

You can do it either way. Actually it may be safer to pick the model up the first time in normal mode to get an idea of how far it is out of trim.

Wayne Mann

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11-23-2006 05:07 PM  11 years agoPost 16
asong26

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VA

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I have a better idea. I have the rotopod that I bought off the ebay for $20.(great deal!)

I'll just use it since the pod as a free spinning center that allows the heli to spin freely.

Thanks.

Andrew

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