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SAB Goblin 630/700/770 SAB Heli Division 630/700/770 - Goblin Helicopters Factory Support


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Old 01-27-2012, 05:01 AM   #101
worldofmaya
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I always recommend reading Henseleits TDR manual, he has all values in there. This extreme-rpm type of flying is something typical for those let's say international- or Align-style machines with their "interesting" way of thinking about what a governor should do. And don't speak about their interesting head-to-tail ratio...
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Old 01-27-2012, 01:37 PM   #102
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What is the head to tail gear ratio of the Goblin BTW? I know the TDR was designed to turn the tail fast at low headspeed (high ratio), but I doubt the Goblin is quite the same. The 110mm tail blades tell me it is a low ratio. Although didn't Bert mention in his SmackTalk video that the Goblin tail is OK at low headspeeds?
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Old 02-05-2012, 11:34 AM   #103
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Here's my shopping list:

Futaba BLS255HV - cyclic
Futaba BLS256HV - tail
Futaba CGY750 - flybarless
Futaba R6203SB - reciever
Power JIVE 120+
WR Hercules super BEC @ 8.4V
Xera 4035/2.5Y 480KV (need 26t or 28t pinion)
12S 5000mAh 45C batteries

About to build a rocket
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Old 02-05-2012, 11:52 AM   #104
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I think the main rotor/tail ratio is 4.77?

Last edited by popokatepetl; 02-05-2012 at 01:04 PM..
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Old 02-05-2012, 12:06 PM   #105
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i think it's 115mm tail blades. you can buy a smaller pinion and another pully for the tail. then you can run low headspeeds
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Old 02-05-2012, 01:06 PM   #106
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Quote:
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i think it's 115mm tail blades. you can buy a smaller pinion and another pully for the tail. then you can run low headspeeds
You are correct Yoda. The only question is why only a 4% change in tail rotor gearing going from the stock Z27 tail pulley to the optional Z26? The Z26 is for use with headspeeds below 2100. If I run 1800 headspeed, that's 14% less main rotor headspeed than at 2100. Seems like even smaller tail pulleys are needed.
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Old 02-05-2012, 01:24 PM   #107
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You'll be safe with 115mm blades even at 1700RPM!

I think you don't need to think about it. It will work for sure even with stock pulley.
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Old 02-05-2012, 01:39 PM   #108
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The stock t/g ratio must be >4. Anyone know the real number?
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Old 02-05-2012, 01:39 PM   #109
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There is a recommendation in the manual in case of head-speed < 2000 rpm. I have the same concern.
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Old 02-05-2012, 01:49 PM   #110
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I do recall reading that the tail blades were to be 110mm at some point. I assume going to the 115mm was to address the tail authority concern at lower headspeeds.
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Old 02-05-2012, 01:58 PM   #111
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Bert's video shows really good tail hold at 1700RPM. So unless they changed the t/g ratio last minute, I would think we're good to go with the 115mm tail blades.

On the other hand, I plan on running 2200RPM, and running the tail as slow as possible for good tail hold will really improve tail belt life. So if the stock t/g ratio is something crazy like 4.8-5.0, I think the high RPM guys are going to see a pretty short life for the belt.
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Old 02-05-2012, 02:32 PM   #112
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I though you could configure the tail RPM by chaning the pully system, was that just wishfull thinking on my part?
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Old 02-05-2012, 02:55 PM   #113
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I think there's only one tail pulley available.

You'll be 100% safe with 115mm blades even at 1600RPM. Don't worry.
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Old 02-05-2012, 02:56 PM   #114
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Quote:
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I think there's only one tail pulley available.
No, there are two pulleys available.
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Old 02-05-2012, 03:03 PM   #115
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No, there are two pulleys available.
Yes you are right. There is 26t as an option and 27t which is in the kit.
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Old 02-05-2012, 03:11 PM   #116
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Quote:
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Yes you are right. There is 26t as an option and 27t which is in the kit.
All us are having the opportunity to in-depth study the Goblin manual.
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Old 02-05-2012, 03:29 PM   #117
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Quote:
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All us are having the opportunity to in-depth study the Goblin manual.
Actually I don't understand why we should bother with that. I'm quite sure that the tail will work from 1600 up to the 2200RPM with default pulley.
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Old 02-05-2012, 03:50 PM   #118
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The tail should be no problem even at lower rpms because the main to tail ratio is pretty good.
-Klaus
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Old 02-05-2012, 04:00 PM   #119
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Quote:
Originally Posted by worldofmaya View Post
The tail should be no problem even at lower rpms because the main to tail ratio is pretty good.
-Klaus
But what is it?
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Old 02-05-2012, 04:37 PM   #120
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plan for me is to run idle1 1850 and idle2 1950. so i'll order 20t pinion and pully H0049-s then i should be ok running low headspeeds i think. would like to try to go below 1700rpm if that is possible
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