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Old 06-25-2008, 08:01 AM   #1 (permalink)
 

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Default Three Questions About Gas EB - Chris B. Please Conribute Your Suggestions

1.

My collective servo died last weekend and I managed to do a very nice auto with soft touchdown from eye level hover. Since collective servo was mounted from the inside of right upper frame, I had to to disassemble it to get it out. Now the question is: can I mount a new collective servo with mounting flanges from outside the upper frame? it seems that there will be no interference with the canopy, but the manual (Rev 1) suggests otherwise.

2.

My tail servo is 9256 which came with 611 Gyro. After the flight it gets very hot, but it's not burning my fingers and I'd guess the temp is lower then 60 deg C. I'm not sure if this is normal and I'm considering installation of "Chinese Weights". Tail grips on this machine are older design which are not anodized like new versions. I know that Chris made new ones to change something and I'm guessing the reason of redesign was to decrease servo load. Since I'm between jobs right now I'd rather not spend money on new grips at this point and go with cheaper solution. I'd like to add Chinese Weights, but don't know how to install them or how much weight to add and at what moment arm. Please advice?

3.

I've had almost 4 gallons of fuel through this machine/engine since new and the engine is tuned well with practically no vibration or at lest as good as it can get with Hanson Pro Plus mod. I've noticed that tail push rod and boom support struts are hitting harmonic frequencies at stable head speed and it's only matter of time until they fail from vibration fatigue. The question is: Is there a viable and simple solution which has been proven to solve this problem?

Thanks to everyone in advance for feedback.
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Old 06-25-2008, 11:37 AM   #2 (permalink)
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The servo needs to be inside the frames for alignment to the triple bellcrank. Check this for the procedure for getting it in and out without dissassembly. http://runryder.com/helicopter/gallery/2555/ , at eth very bottom of the gallery is a pic showing how to do it.

The 9256 does get hot, that's why it comes with the metal case and is ribbed to help dissipate that heat.

I have no idea, never having added the chinese weights to our blade grips, on how much or where. Interesting idea, I may experiment with them myself in the future, when I get some free time.....

If you're hitting harmonic frequencies, try different headspeeds. We do suggest a range of headspeeds, the point of which is to find where YOUR helicopter is happiest. 1450 is a starting point, 1550 is not out of the realm of possibilities. Up to 1650 for aerobatics.

You do also have the velcro strap, securing your tail pushrod?
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Old 06-25-2008, 06:26 PM   #3 (permalink)
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Quote:
You do also have the velcro strap, securing your tail pushrod?
No, never heard of this before. Could you please post a link or a picture?
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Old 06-25-2008, 06:30 PM   #4 (permalink)
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Found the picture of a velcro strap. How tight should it be?
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Old 06-25-2008, 06:42 PM   #5 (permalink)
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We're wanting to just put pressure on the pushrod, not enought to bend it, just slight amount of pressure.

This accomplishes 3 things;

1. dampens out any harmonics that EVERY helicopter has.

2. when placed just under the front of the horizontal fin, it prevents the pushrod from hitting the tailboom support.

3. If the pushrod does pop off the tail bellcrank, then it keeps the pushrod from hanging straight down, making for a very difficult landing....
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Old 06-25-2008, 06:55 PM   #6 (permalink)
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Thank you Chris. Regarding the new collective servo install: There is no way that i can it it inside the frames. It's JR 8711 with red metal case and it's slightly larger then Futaba 9252 which was there originally. I have two choses at this point, to disassemble the servo get it inside the frames and reassemble or just dremel the crap out of left upper frame.

Second option will be a permanent fix in case new servo needs to be taken out, but I don't want to ruin the frame....
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Old 06-25-2008, 07:06 PM   #7 (permalink)
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Hmmm. You're right, the 8717 is slightly larger. To get it installed without disassembly would probably take a LOT of hacking, Not my first choice.

Better to do it right and do a partial disassembly. Remove the front two sets of frame spacers, battery monitor mount (the angled plate), and the gyro mount plate. You should be able to then spread the upper frames far enough apart to get the servo in.

Also clearance the frames where the servo wire exits the servo.
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Old 06-25-2008, 07:28 PM   #8 (permalink)
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Sounds good! thanks!
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