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Low Head Speed Helicopters Low Head Speed Helicopter Setups and Flying info


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Old 11-23-2016, 11:31 AM   #1
Mash USA
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Default Goblin Black Thunder 650 low RPM

Building a G650 and I have some questions about RPM . I recently built and flew a Goblin 570 and notice for low head speed that I had to change the tail pulley from T22 to T 21 for it to fly with out tail wag . So that's the question will I need to change the motor pulley and or the tail pulley to achieve low RPM . Also what is considered an average good low head speed for a 650 Goblin . I appreciate any advice thanks Todd

Last edited by Mash USA; 11-23-2016 at 10:14 PM..
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Old 12-19-2016, 07:35 PM   #2
amphibia
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Quote:
Originally Posted by Mash USA View Post
Building a G650 and I have some questions about RPM . I recently built and flew a Goblin 570 and notice for low head speed that I had to change the tail pulley from T22 to T 21 for it to fly with out tail wag . So that's the question will I need to change the motor pulley and or the tail pulley to achieve low RPM . Also what is considered an average good low head speed for a 650 Goblin . I appreciate any advice thanks Todd
T22 to T21 on tail is a good idea but probably not enough if you intend to go to half 3D headspeed (e.g. 600-700clss at 1000rpm).

Low rpm flights has a much lower demand on motor as the air parastic drag is significantly reduced. I think motor pulley option is not that strict. No need to split hair to decide on 1~2 more/less tooth on the pinion.

A guideline that I find useful for tail authority is when it hovers close to the ground at your desired rpm, you observe (safely but closely) the tail sliding ring and lever arm. They should still be at close to 90% angle. If not, you probably need to increase the tail authority:
1. even smaller T20, T19 to speed up tail (which probably are not available)
2. longer tail blades (e.g. I use 95mm blades on my JR E6-550 for low rpm)
3. more blades (3-blade tail)
4. longer boom (which probably isnt an option for goblin)

As t
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Last edited by amphibia; 12-20-2016 at 01:37 AM..
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