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HomeRC & Power✈️Aircraft🚁HelicopterFlybarless Rotor Head SystemsFutaba CGY › CGY 750 and SBUS servos
01-08-2013 02:23 AM  7 years ago
nickmaxwell

rrApprentice

Huntsville, AL

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I'd like to chime in here maybe helping explain a bit in detail the differences between some of these servos, or at least how I look at the differences and how it impacts the heli's peformance.

1) Regarding the confusion on SBus servo being used without an SBus support hub. The SBus capability is refering to how the servo parameters may be programmed post-factory programming using either the SBus port in the 18MZ or PC-Link. SBus servo paramteres are not controlled by the SBus hub, but rather are set-up by SBus technology, then respond to a programmed channel that is like a normal signal to any other servo. By using an SBus hub each servo is programmed to read the corresponding channel it has been programmed for. So if the Sbus servos are programmed for CH1 or in stock settings, they will just reply to whatever port they are plugged into as any other servo.

2)Regarding S9353HV vs. BLS255HV and BLS272SbusHV. I have tried all three of these servos now, specifically with extensive testing with the S9353HV to try to take advantage of their speed and torque. I found that really there is not much performance increase by using such a fast/torque-y servo. Actually it somewhat interfered with the CGY750 parameters that are set to match general heli servo speed and response to the rotor head. Since FBL control loops take all these things into consideration, simply using a faster responding servo is not always the best case. But regardless, they performed fine in general, just the 255/272 might be a little more elegantly matched with a CGY750. Over all I much prefer the BLS272SBusHV. The BLS255HV and a stock setting BLS272SBus HV will be the same servo. The 272 version I do feel has some advantages, for helicopters that cannot use round servo wheels that can be accurately drilled for 0 subtrim, the Sbus servo can be handy as the neutral can be fine adjusted in the servo to keep the FBL unit's subtrim at 0. That of course simplfies set-up, and I do feel that improves the performance of the system.

3) Longevity. As with any BLS servo, they are tough cookies! The actual power/control system will not wear out very fast at all, and the gears will wear before the servo performance. In this case, a lot of times after say 600-700 flights in a glow model, and 700-800 in an electric model simply putting new a gear train in a BLS servo makes them just as good as new.
This was also one of my concerns with the S9353HV. And I found that after 400-500 flights they did start to loose raw performance as any other coreless servo would. That being said, I've become spoiled with basically using one set of servos for year(s) at a time in a heli. So for me, I'll continue using BLS255/BLS272SBus.

Having tried the BLS157 (blue cases) as well. I can confirm that the torque really isn't needed, and the better balance of torque/speed out of the BLS255/272 seems to be a better match for most FBL systems out there.

-In some 800 size models- specifically direct servo to swash link 800+ sizes I could see where the BLS157 would be the cats meow. I am currectly using BLS255HV in my E820 and the performance is outstanding with 813mm blades. All the way up to 2000RPM, but this model is bell crank control driven, and also like all the G4 Raptors has the torque biased control arms between the swash/blade grip. So it is not as particular regarding servo parameters.

I hope this helps for any of those who were curious for some more opinions from guys who have tried the different servos.

Nick
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01-08-2013 02:43 AM  7 years ago
knightofcarnage

rrElite Veteran

chicago

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Nick , thanks for a great replay. I do have a simple question for you. Is there any know differences between SBUS servo vs SBUS2 servo?
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01-08-2013 03:04 AM  7 years ago
Bugcatcher

rrApprentice

Perth, Australia

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Awesome info Nick, thanks. Pretty much confirmed what I have experienced.

I actually didn't know about SBUS2 until I just looked it up.

From the Futaba Japan site.

'New "SV" and "SVI" servos are compatible with S.BUS 2 system allow you connect S.BUS 2 port in line with telementry sensors.'

'New "SV" series servos come presets with soft start in order to protect the linkage. Also you can change this to use servo program function.'

Also what alot of people aren't aware, Futaba is a much, much bigger company than just R/C electronics. They manufacture heavy industrial robotics along with other automation technology. SBUS was developed for this and has found it's way down into their R/C business line after alot of development so you can be assured of it's robustness and continuing development in the future.
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HomeRC & Power✈️Aircraft🚁HelicopterFlybarless Rotor Head SystemsFutaba CGY › CGY 750 and SBUS servos
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