HobbyKing.com New Products Flash Sale
Reply
Thread Tools
Old Feb 24, 2015, 05:28 PM
There's magic in those wings !
khaled_abobakr's Avatar
Joined Nov 2006
4,915 Posts
Discussion
Servo flapping Ornithopoter by mlbco

Hi

Servo-Flap Ornithopter (2 min 1 sec)



Both were built by mlbco aka Steve ...

I really like how the servo flapping Ornithopter flies ... the transition from flapping to short glide then resume flapping is smooth and I suppose it is 100% guaranteed ...

I'm sure if those servos were replaced by Brushless servos it will be even more reliable .. it feels so light and flaps slowly too ..

The result is a maintenance free Ornithopter ... also I suppose it will fly longer .. the consumption of the two servos should be less than a BL outrunner ... and a new realistic style of flying like a real bird does ... flap then glide . then flap then glide ..

I hope Steve chimes in , and tell us his thoughts .,,,

Ohh.... this cambered wing .... I love it ... it seems it benefits from the strong toss at launch .. it creates lift ... I thing I will nose in my Slow hawk if I toss it that hard ...

Hats of to you Steve

Khaled
khaled_abobakr is offline Find More Posts by khaled_abobakr
Reply With Quote
Sign up now
to remove ads between posts
Old Feb 24, 2015, 09:38 PM
Registered User
Palo Alto, California, United States
Joined Jan 2003
1,093 Posts
Khaled,

I didn't invent this concept, I saw it first mentioned in a thread about a university project (U Maryland?) where they used servos as a direct drive. Around the same time Nathan Chronister published a design using a similar set up. I had an old Basic Stamp controller laying around and decided to buy the servos mentioned in the original article and build a model. My model is heavier than the other prototypes (15.7 ounces) built by U Maryland and Nathan, and therefore need more power. I had problems with the servos overheating and I was running them hard at 8.6V regulated. Eventually I burned out a motor at this high voltage and haven't done anything with the model since.

I like the direct servo drive approach for a few reasons:
1) Near sinusoidal flapping is easily achieved by programming the appropriate flapping wave form.
2) Glide lock is trivial, just program the servos to a fixed dihedral when the throttle is below a certain setting.
3) It should be possible to program asymmetric flapping for turns ( I didn't try this)

This is the only ornithopter I've owned that I was able to catch thermals with and climb out, even in light lift. If someone makes a more powerful servo than the Futaba S9352HV servos I used I'd consider building another version, I just don't want to fly with overheating servos. I would also recommend using a better microcontroller than the old Basic Stamp I used. The Stamp was adequate but lacked the processing speed to implement all the functions I wanted to test.

Thanks,

Steve
mlbco is offline Find More Posts by mlbco
Reply With Quote
Old Feb 25, 2015, 03:36 PM
There's magic in those wings !
khaled_abobakr's Avatar
Joined Nov 2006
4,915 Posts
Hi Steve

I'm searching for better servos now and I will report back once I find any

1- Does the flapping frequency change with the throttle input ??

2- Can you program it to change the flapping amplitude ?
It's like having dual rate switch ... so you use high flapping amplitude to climb higher and higher then switch to low flapping amplitude to save energy once you reach the desired altitude

Thanks

Khaled
khaled_abobakr is offline Find More Posts by khaled_abobakr
Reply With Quote
Old Feb 25, 2015, 06:14 PM
There's magic in those wings !
khaled_abobakr's Avatar
Joined Nov 2006
4,915 Posts
Hi Steve

What about this one from MKS

http://mks-servo.com.tw/goods.php?goods_id=hv777

Torque: 28 kg-cm (6.0V) / 36.5 kg-cm (7.4V) / 38 kg-cm (8.2V)

Speed: 0.14 s (6.0V) / 0.11 s (7.4V) / 0.10 s (8.2V)

Weight: 81.4 g

Dimensions:40 x 20 x 45 mm
Operating Voltage:4.8 ~ 8.4 V DC Volts ( 2S Lipo un-regulated )
Working frequence:1520μs / 333hz
Dead band:0.0008ms (Default)
Bearing Type:2BB
Motor Type:Japan High Quality Coreless Motor
Gear Type:Chrome-Titanium alloy gear

MSRP:133.05 USD/pcs
khaled_abobakr is offline Find More Posts by khaled_abobakr
Reply With Quote
Old Feb 25, 2015, 08:58 PM
Wildlife Artist / RC Designer
DaVinciBrainchld's Avatar
Joined Jul 2014
245 Posts
Very interesting stuff guys. :-)

As a side note - I've often wondered what happened to Nathan Chronsler. Does anyone know??
DaVinciBrainchld is offline Find More Posts by DaVinciBrainchld
Reply With Quote
Old Feb 25, 2015, 09:48 PM
Registered User
Palo Alto, California, United States
Joined Jan 2003
1,093 Posts
Quote:
Originally Posted by khaled_abobakr View Post
Hi Steve

What about this one from MKS

http://mks-servo.com.tw/goods.php?goods_id=hv777

Torque: 28 kg-cm (6.0V) / 36.5 kg-cm (7.4V) / 38 kg-cm (8.2V)

Speed: 0.14 s (6.0V) / 0.11 s (7.4V) / 0.10 s (8.2V)

Weight: 81.4 g

Dimensions:40 x 20 x 45 mm
Operating Voltage:4.8 ~ 8.4 V DC Volts ( 2S Lipo un-regulated )
Working frequence:1520μs / 333hz
Dead band:0.0008ms (Default)
Bearing Type:2BB
Motor Type:Japan High Quality Coreless Motor
Gear Type:Chrome-Titanium alloy gear

MSRP:133.05 USD/pcs
That servo looks to be a bit better (3%) in terms of peak power output. I estimate power from torque/transit time which is proportional to torque*angular velocity. The power may be more usable at the higher torque and lower speed compared to the Futaba servo. The price is competitive too, I may need to try them!

Steve
mlbco is offline Find More Posts by mlbco
Reply With Quote
Old Feb 26, 2015, 05:17 AM
There's magic in those wings !
khaled_abobakr's Avatar
Joined Nov 2006
4,915 Posts
Quote:
Originally Posted by mlbco View Post
That servo looks to be a bit better (3%) in terms of peak power output. I estimate power from torque/transit time which is proportional to torque*angular velocity. The power may be more usable at the higher torque and lower speed compared to the Futaba servo. The price is competitive too, I may need to try them!

Steve
Hi Steve ...

It is surprising that brushless servos are not as fast as the brushed ones ...

Here is a One from hitec ... but the speed is only 0.14 sec

I wonder if you can use a reduction gear to just get the speed you want ... , of course that will reduce the torque a bit .... it seems like an optimization between the two ... but it is worth giving a try for a brushless servo .. to benefit from the durability

Khaled
khaled_abobakr is offline Find More Posts by khaled_abobakr
Reply With Quote
Old Feb 26, 2015, 06:04 AM
There's magic in those wings !
khaled_abobakr's Avatar
Joined Nov 2006
4,915 Posts
Quote:
Originally Posted by khaled_abobakr View Post
Hi Steve

I'm searching for better servos now and I will report back once I find any

1- Does the flapping frequency change with the throttle input ??

2- Can you program it to change the flapping amplitude ?
It's like having dual rate switch ... so you use high flapping amplitude to climb higher and higher then switch to low flapping amplitude to save energy once you reach the desired altitude

Thanks

Khaled
Hi Steve

I think you missed this post ...

Khaled
khaled_abobakr is offline Find More Posts by khaled_abobakr
Reply With Quote
Old Feb 26, 2015, 06:17 AM
There's magic in those wings !
khaled_abobakr's Avatar
Joined Nov 2006
4,915 Posts
Savox Servos

Okay ... it seems that Savox may have what you need ... Choose the the one that fits better

************************************************** ************************************************** ************

Brushless servos

savsb2231sg

Dimensions(mm): 40.3x20.2x45.0
Weight(g): 84.0
Speed(@6.0V sec/60): .14
Torque(@6.0V oz-in): 444.4
Speed(@7.4V sec/60): .10
Torque(@7.4V oz-in): 555.5

Gear: Unique Steel
Bearing: 2BB
Case: Full Aluminum
25 Tooth Spline
Frequency: 250-333
Pulse Rate Frequency: 1520

SAVSB2282SG

Dimensions(mm) 40.3 x 20.2 x 38.7
Weight(g): 79.0
Speed @6.0V: .09sec
Torque@6.0V: 236.1 oz-in
Speed @ 7.4V: .075sec
Torque @ 7.4V: 319.4oz-in.

Gear Type: Steel
Bearings: 2 BB
Frequency: 250-333Hz
Pulse Width Frequency: 1520>

savsb2274sg

Dimensions(mm): 40.3x20.2x38.5
Weight(g): 69.0
Speed(@6.0V sec/60): .105
Torque(@6.0V oz-in): 277.7
Speed(@7.4V sec/60): .08
Torque(@7.4V oz-in): 347.2

Gear: Unique Steel
Bearing: 2BB
Case: Full Aluminum
25 Tooth Spline

savsb2273sg

Dimensions(mm): 40.3x20.2x38.5
Weight(g): 69.0
Speed(@6.0V sec/60): .12
Torque(@6.0V oz-in): 319.4
Speed(@7.4V sec/60): .095
Torque(@7.4V oz-in): 388.8

Gear: Unique Steel
Bearing: 2BB
Case: Full Aluminum
25 Tooth Spline
Frequency: 250-333
Pulse Rate Frequency: 1520
Frequency: 250-333
Pulse Rate Frequency: 1520

savsb2270sg

Dimensions(mm): 40.3x20.2x38.5
Weight(g): 69.0
Speed(@4.8V sec/60): .19
Torque(@4.8V oz-in): 291.6
Speed(@6.0V sec/60): .15
Torque(@6.0V oz-in): 347.2
Speed(@7.4V sec/60): .12
Torque(@7.4V oz-in): 444.0

Gear: Unique Steel
Bearing: 2BB
Case: Full Aluminum
25 Tooth Spline
Frequency: 250-333
Pulse Rate Frequency: 1520


Brushed Servos

savsc1268sg

Dimensions(mm): 40.3x20.2x37.2
Weight(g): 62.0
Speed(@4.8V sec/60): .15
Torque(@4.8V oz-in): 160.0
Speed(@6.0V sec/60): .13
Torque(@6.0V oz-in): 208.3
Speed(@7.4V sec/60): .11
Torque(@7.4V oz-in): 347.2

Gear: Unique Steel
Bearing: 2BB
Case: Aluminum
25 Tooth Spline
Frequency: 250-333hz
Pulse Width Frequency: 1520

savsv1271sg

Dimensions(mm): 40.3x20.2x37.2
Weight(g): 63.0
Speed(@6.0V sec/60): .11
Torque(@6.0V oz-in): 277.7
Speed(@7.4V sec/60): .08
Torque(@7.4V oz-in): 347.2

Gear: Unique Steel
Bearing: 2BB
Case: Aluminum
25 Tooth Spline
Frequency: 250-333hz
Pulse Width Frequency: 1520

savsv1272sg

Dimensions(mm): 40.3x20.2x37.2
Weight(g): 63.0
Speed(@6.0V sec/60): .13
Torque(@6.0V oz-in): 319.4
Speed(@7.4V sec/60): .10
Torque(@7.4V oz-in): 416.6

Gear: Unique Steel
Bearing: 2BB
Case: Aluminum
25 Tooth Spline

savsv1270tg

Dimensions(mm): 40.3x20.2x37.2
Weight(g): 56
Speed(@6.0V sec/60): .14
Torque(@6.0V oz-in): 361.1
Speed(@7.4V sec/60): .11
Torque(@7.4V oz-in): 487.7

Gear: Titanium & Aluminum
Bearing: 2BB
Case: Aluminum
25 Tooth Spline
Frequency: 250-333hz
Pulse Width Frequency: 1520
khaled_abobakr is offline Find More Posts by khaled_abobakr
Last edited by khaled_abobakr; Feb 26, 2015 at 06:30 AM.
Reply With Quote
Old Feb 26, 2015, 11:34 AM
Registered User
Palo Alto, California, United States
Joined Jan 2003
1,093 Posts
Quote:
Originally Posted by khaled_abobakr View Post
Hi Steve

I'm searching for better servos now and I will report back once I find any

1- Does the flapping frequency change with the throttle input ??

2- Can you program it to change the flapping amplitude ?
It's like having dual rate switch ... so you use high flapping amplitude to climb higher and higher then switch to low flapping amplitude to save energy once you reach the desired altitude

Thanks

Khaled
Khaled,

I checked my notes and they say that throttle input controls both wing amplitude and beat frequency (i.e. increasing throttle increases both frequency and amplitude). I wanted to experiment with independent control of each variable but never got around to trying that. I can't remember why I had throttle controlling both frequency and amplitude but it probably had something to do with the limitations of the Basic Stamp controller.

Steve
mlbco is offline Find More Posts by mlbco
Reply With Quote
Old Feb 26, 2015, 04:17 PM
There's magic in those wings !
khaled_abobakr's Avatar
Joined Nov 2006
4,915 Posts
Thanks a lot for the reply Steve ... hope to see any progress soon

Good luck

Khaled
khaled_abobakr is offline Find More Posts by khaled_abobakr
Reply With Quote
Reply


Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Discussion DX7 Dual Flap Servos, Dual Aileron Servos, Dual Elevator Servos dickbeep Radios 5 Nov 13, 2014 05:04 PM
Discussion sport cub s2 flap servo question russrugg Beginner Training Area (Aircraft-Electric) 2 Nov 09, 2014 11:05 AM
Discussion Flap servos for Calypso kurtenstein Electric Sailplanes 5 Nov 05, 2014 07:48 PM
Help! JR 9503 and flap servo travel, It's has less travel on one of the 2 flap servo Mr.Greenjeans Sailplane Talk 14 Jan 26, 2014 04:23 AM
Discussion flapping by servos samwei1950 Ornithopters 5 Oct 30, 2013 02:55 AM