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HomeAircraftHelicopterThunder TigerRAPTOR 90 › Raptor G4
01-27-2012 10:30 PM  6 years agoPost 1
John Benario

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Las Vegas

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I had a slow year with helicopters because, among other things, I was buying and rebuilding gear machines!

Now that I have gotten back to the models, I recently finished my Raptor G4. I never thought I would be saying this, but I think the G4 is my new favorite helicopter. There were a couple of QC issues, one of my bearing blocks had the bolt holes untapped, and one of the blade grips didn't have the bearings installed, which I just fixed rather than waiting for new parts,

I did make a couple of changes. The G4, like the original Raptor 90, has a very high flybar ratio, and even though the G4 has an inner hole on the seesaw, the inner hole ratio is still high. I drilled a third hole inside of the inner hole to give flybar ratio of about .67, which is more suitable for 3D.

The stock nitro gear ratio is 7.92, which is fine for FAI, but too low for 3D, so I made a 115 tooth gear for a ratio of 8.21 which is very close to ideal for the HZ.

Also, just as an experiment, I made helical tail rotor gears to compare the noise and smoothness to the stock. The helicopter is slightly smoother, but any noise difference was imperceptible. Maybe on an electric it would be discernible.

The G4 is not my fastest model since the canopy is a bit broad, the landing gear is pretty obtrusive, and the high flybar head has more drag than low flybar heads, but the flying qualities are really nice.

Ron Lund put a little writeup about gear manufacturing and my gear machine on his website.

John Benario

Team highest quality
Futaba radios
Cool Power fuel
John's Ultimate building school

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01-28-2012 12:01 AM  6 years agoPost 2
ticedoff8

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Morgan Hill, CA. USA

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How is the flybar ratio calculated?

One of mine has the R-90 SE head (the other is a Trex 700N head).

There are some obvious differences between the G4 & the SE, but I wonder what the flybar ratio (on the old 90SE head) is when the bell-hiller mixers are moved to the inner hole?

Also, your main gear ratio seems odd: a 115 tooth main and a 9.21:1 ratio means you have a 12.48 tooth pinion. Kind'a scratchin' my head here.
Although, at about 15,500 to 16,000 on the engine (about right for a OS 91HZ-R) and a 9.21:1 ratio, the head speed comes out to 1700 to 1750 - and I like that on my R-90 (both of them).

Have you thought about cutting some helical-cut 11-tooth pinions & 95-tooth mains for the old R90 clutch bell?
I don't know if I could use the G4 clutch bell on the 90SE without a new flywheel, starter rod - etc.
Even though you didn't notice a big difference in sound on your tail drive gear, I think the helical-cut gears might be quieter & stronger than the straight cut.
I would be interested in giving it a try as a replacement main gear if you ever decide to try it.

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01-28-2012 05:01 AM  6 years agoPost 3
Dr.Ben

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Richmond, VA, USA

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John,

Are you sure you meant 9.21? If yes, then you have the only 91 HZ model on the planet running that ratio in a sport 3D model running the typical 1950 or so RPM.

Ben Minor

Peak Aircraft/Team Minicopter Team Futaba Team Kontronik USA

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01-28-2012 05:12 AM  6 years agoPost 4
John Benario

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Las Vegas

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Dr. Ben is of course correct, I corrected the typo to 8.21.

John

Team highest quality
Futaba radios
Cool Power fuel
John's Ultimate building school

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01-28-2012 09:43 AM  6 years agoPost 5
NitroAl

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Gold Coast Aus

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The stock gearing is optimized for the RL100 which produces peak power at 14500rpm
Apparently the G4 is nuts with the 120 @ 2000!

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01-28-2012 09:52 AM  6 years agoPost 6
nytflyer

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Temasek

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Well i had similar issue here..one of the pinion block mounting holes had its thread done halfway that i ended having the Torx screws broken and the remaining piece left embedded in the block..this is the second time the e720 parts failed on me..whats up with the QC over there??

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01-28-2012 12:42 PM  6 years agoPost 7
Mizark

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Sydney, Australia

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The stock gearing is optimized for the RL100 which produces peak power at 14500rpm
Apparently the G4 is nuts with the 120 @ 2000!
Are you sure? That means it will only run at 1830 or so for peak power? That is very low. The G4 manual actually recommends 2000-2100rpm headspeed on the nitro version.

I am running 2050 at the moment with a OS91HZ-R Speed.

Mark Lilley

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01-29-2012 05:04 AM  6 years agoPost 8
NitroAl

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Gold Coast Aus

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The manual says to run the RL100 between 1850 and 1980 (from memory) with 7.92:1 and going by the dodgy dyno chart the power does not drop off much above peak and there is overhead to 16000rpm.
I run my 105 @ 2000hs with 8.2:1 which works out to 16400 and it seems pretty happy regardless of the fact it is 400rpm out of it's "operating speed" so who knows how bogus these power @ rpm figures are ;-)

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01-29-2012 04:49 PM  6 years agoPost 9
Skaluf

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Champaign, IL

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Also, just as an experiment, I made helical tail rotor gears to compare the noise and smoothness to the stock. The helicopter is slightly smoother, but any noise difference was imperceptible. Maybe on an electric it would be discernible
Hi John, I'm a little confused with this statement as the G4 comes stock with helical cut gears on the tail.
There were a couple of QC issues, one of my bearing blocks had the bolt holes untapped, and one of the blade grips didn't have the bearings installed, which I just fixed rather than waiting for new parts
Do you have a stock kit or pre-production?

I'm glad you are enjoying the G4, it is a pretty incredible bird. It seems like most of the serious FAI F3C pilots in the US are moving to this machine as well as many of the top 3D guys.

Steve

Steve Kaluf
Hobbico

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01-29-2012 05:02 PM  6 years agoPost 10
John Benario

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Las Vegas

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Hey Steve,

I made helical gears for the tail rotor drive gear and pinion up front, you can see in the picture. I can't make bevel gears. I wish I had a Gleason machine for bevel gears, but that is a bit out of my league!

I have a stock kit from Ron Lund.

John

Team highest quality
Futaba radios
Cool Power fuel
John's Ultimate building school

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01-29-2012 05:50 PM  6 years agoPost 11
John Benario

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Las Vegas

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Regarding the RL100, (which I know nothing about) if 14,500 is optimum power, and you want 1950 on the head, that works out to 7.44 which is a 104 tooth gear. I went non-standard 4 teeth larger on my 115 tooth gear, which is probably at the limit of non-standard tooth profile.

I could probably go down to 107 teeth, but a 106 or 105 or 104 would probably be beyond useable limits.

Of course if you move the engine it becomes easy to change the ratio, but the problem with moving the engine in this helicopter is the fan shroud can't be moved.

John Benario

Team highest quality
Futaba radios
Cool Power fuel
John's Ultimate building school

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01-29-2012 05:55 PM  6 years agoPost 12
JPhillips

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Waco, TX

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Why change it? Just curious.

To each his own.

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