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CarbonXtreme . Midland Helicopters . HeliProz

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Flybarless Rotor Head Systems > Does Vbar require fast swash servos ?
 
 
demosa
Veteran
Location: Tigard, Oregon, U.S.A.

Does a Vbar setup require fast swash servos just like a good gyro requires fast tail servo ? How fast is fast enough ?

Thanks
06-12-2008 11:05 PM
 
 
Joe90
Senior Heliman
Location: Quebec, Canada

You can tailor the parameters to suit your servos. but mikado recommend digital servos

After testing S9252 on 5.6v are fast enough to have a ball
06-13-2008 12:45 AM
 
 
ArtK
Veteran
Location: San Marcos, Ca

Speed and Torque are both important

It works very similar to the tail rotor system. Speed is important to get gain as high as possible without oscillating. Torque is important to keep it far away from stall torque during maneuvers. With that said- a 50 size heli works fine with 9252 servos or equivalent, I use the brushless ones. For a 90 size- I would use the 8717’s. For my trex 500, 9650’s are working great.

I love these things!!!
06-13-2008 06:09 AM
 
 
Eco8gator
Key Veteran
Location: Palm Beach Gardens, FL

Speed is meaningless with out torque to back it up. The 8717's are extreamly durable servos that are both fast and have loads of torque.

The next big thing is the ability to handle decent frame rates(some digital servos have the ability to handle higher frame rates). The more information you can get to your servos the more your flybarless system can do to make it feel extreamly locked.

To give you an idea of whats going on.

Your typical Rx has an update rate of about 20ms.

A flybarless system with the option to choose a higher frame rate can get information to your servos at ~8ms...thats over 2x more data. The Rx is still updating at 20ms BUT your control system is spitting out critical corrective information faster which helps give you that locked feel.

C
06-13-2008 06:28 AM
 
 
demosa
Veteran
Location: Tigard, Oregon, U.S.A.

Thanks for all the responses.

I want to use the Vbar on my Lepton (same size as the TREX500).
I do have high-torque digital servos but they are slow 0.25sec or something... (its the Futaba 3150)

Should I consider faster servos before even attempting the VBar or will it be ok with the servos I have ?

Thanks again !
06-13-2008 04:45 PM
 
 
ArtK
Veteran
Location: San Marcos, Ca

I would get faster servos

They might be to slow. Gain would be reduced significantly to make that work. You might not get the locked in feel. However, nothing wrong with expirementimg if you have the time before you buy. Just set the gain very low to start and work up slowly.

I love these things!!!
06-13-2008 05:41 PM
 
 
Joe90
Senior Heliman
Location: Quebec, Canada

S9252 + V-Stabi + Vibe 90 = SUPER

Just to make things clear

I fly with S9252 + SGP regulator + Mikado V-Stabi on a VIBE90 and they work greath.

I have another vibe with flybar + 8717 altough you can feel a difference in hover and in the beginning on the manoeuver (showing the precision due to torque) it is not worth it if you already have S9252.

I tried too S9155 with more torque and less speed (.16deg /s @4.8v)
on the vibe they were a little bit better in hover and but they are far behind S9252 in pitch pumping and 3D, I had nodding too, too slow ! Of course I could have changed my parameters to suit these but I did not liked their slow reactions.

Personnaly, I did not try S3151 but they are too slow to show what V-Stabi is all about. You wont regret to have fast digital servos.

(edit) Last weekend I did try 8717 on a 50 ccpm machine, and they do make a worthwile difference from S9155

Regards

Michel
06-14-2008 02:07 PM
 
 
Reesy
Key Veteran
Location: In the doghouse ... Nottingham UK

Very interesting points here guys,

OK I've got 2 helis to fit out so some sage advice would be well appreciated.

Trex 500
Options are:
1. Volz maxx servo's off my 3DMP allthought they are small they've taken everything the big heli can throw at them. Plus points they won't cost me anything
Negative is they might be too slow @ 0.18 sec (not 100% sure of this as they are the "Jan modified" versions

2. Fut 9602 coreless 2.7kg and 0.09 sec (I have one I tried as a tail servo so only need 2 more) My guess is these will be less "precise" than digitals but if the Vstabi is constantly correcting will this be an issue?

3. 3x Fut 9650 good torque 4.5 kg sl less speed .11sec
4. 3x Fut 9257 less torque 2.0kg more speed .08 sec

Options 3 +4 are slightly less attractive as I'd have to buy 3 and I'd prefer to put my budget into:

3DMP

This will hopefully undergo a full size servo conversion + vstabi soon.

Options here seem to be

1. 3x JR 8231 (high precision 6.8kg .22 sec) nice as I happen to have 3 lying around but I assume will be too slow

2. Fut 9255 Fut's heli cyclic servo so I guess it must be good but maybe a tad slow at .16sec and 9.0kg

3. Fut SBL451 brushless 10.6kg 0.10sec similar price to 9255's but maybe less precise?

I have a source of Fut servo's which is why I didn't mention JR and my budget won't really stretch to 2 lots of 3 nobbyjobbies at least whilst I pay for 2 Vstabi's

Or I could wait a while if you think that was 100% the best solution.

Many thanks for any input

Ting Tong
.... ...... ...from Tooting
06-18-2008 09:32 AM
 
 
ArtK
Veteran
Location: San Marcos, Ca

full size servos don't do it

[quote]I would stick with mini servos only. 500 is on the heavy side already. .15 seconds or faster .40 oz or stronger. Metal gear is perferable for crash resistance.

I love these things!!!
06-18-2008 01:46 PM
 
 
Reesy
Key Veteran
Location: In the doghouse ... Nottingham UK

Thanks for the reply Art

The full size was for the 3DMP only.

I guess I was more interested in whether to go for the precision of digital v's the speed and torque of the coreless and brushless options

Ting Tong
.... ...... ...from Tooting
06-18-2008 02:38 PM
 
 
ArtK
Veteran
Location: San Marcos, Ca

Brushless

I fly the brushless on my flybarless logo 600 and really like the setup.

But in all fairness it seems to fly the same as my original setup with 9252's. I guess the big advantage with brushless is life span.

I love these things!!!
06-18-2008 03:20 PM
 
 
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Flybarless Rotor Head Systems > Does Vbar require fast swash servos ?
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