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Jan 09, 2008, 06:31 PM
Registered User
Thread OP

1.2 gm servo improvements

The 1.2gm servo has been updated to use the original gears from
4.3/4.7 gm servos without purchasing a 2nd set of gears. The output
gears are made by modifying G5 and G6 from orig. servos.

I will have a number of the updated units completed for sale in 2

See attached photos of completed servo and individual parts. The servo
weight includes 2" wire leads and connector pins. The servo operates on
3 to 5.5V and has >1 oz. thrust. The servo is made from the following
parts: 4 x 8 mm, 10 ohm pager motor; 3mm, 10k ohm feedback pot;
five 1/64" laser cut ply parts, 2 CF & 1 Alum gear shafts, 6 gears from 4.3 gm
servos, servo amplifier from United Hobbies 4.3 gm servo, # 36 AWG
stranded wire. If you are interested in some of these servos
let me know. I sell completed/tested servos and complete kits for
DIY. Note: The DIY kits should only be attemtted by those who have
mechanical and soldering skills, to work with very small parts!

I have tested these servos in 1/2 oz to 3 oz airplanes with great results.
The 1/2 oz airplane operates on a single 90mah Lipo cell.
Last edited by scharlach; Mar 28, 2008 at 10:45 AM. Reason: Updated design
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Jan 09, 2008, 06:53 PM
Inciting Riots
village_idiot's Avatar
Is it correct to assume that the gears and circuit board are from the same servo?
Jan 09, 2008, 07:23 PM
I used to be all thumbs...
NumbSkull's Avatar
Very impressive!!!
Jan 09, 2008, 07:59 PM
Thanks for the Fish!
aerogel's Avatar
I love's what I love about this board
Jan 09, 2008, 08:10 PM
Good Better Best quest.
olmod's Avatar
I think hes done a fine job one suggestion i would like to make is ,if you take the allum cover off a floppy disc a u shaped chanel could be formed into wich the servo could be built ,this not only would be light but dimensionally stable to keep gear mesh tolerences lash free.
Jan 09, 2008, 09:13 PM
Registered User
Thread OP

servo gears

Yes, you can use pinion gear, and gear 2,3,4,5 from 4.3gm servo but
you need to order a second gear 3 as this size gear is used twice in
this design. BP Products carry gear sets for Arrow 4.3gm servos.
Jan 09, 2008, 09:21 PM
A&P Mechanic
may-day's Avatar
will you sell any pre built servos?
Jan 09, 2008, 09:27 PM
Inciting Riots
village_idiot's Avatar
OK, thanks. I wonder if we could source that extra gear from someplace like so that the waste could be kept down. I guess the extra gears would be useful for repairs.
Jan 09, 2008, 09:40 PM
Dongo's Avatar

What servo board are you using the Blue Arrow 4.3g or the EM 4.3g? What about the pot, source or datasheet?


Jan 09, 2008, 10:00 PM
Registered User
AleG's Avatar
Originally Posted by scharlach
Yes, you can use pinion gear, and gear 2,3,4,5 from 4.3gm servo but
you need to order a second gear 3 as this size gear is used twice in
this design. BP Products carry gear sets for Arrow 4.3gm servos.
How about using less gears? less weight and complexity.

Here´s a picture of my attempt at modding an 7.5g servo; end weight is 2.5 but doesn´t work, way too jittery. I think it should be OK with a second gear reduction.

Jan 10, 2008, 04:16 AM
Registered User

diy servo

This is the servo that i make:
little 2g servo (0 min 22 sec)
Jan 10, 2008, 05:41 AM
diy heli maker
U.S.U.L's Avatar
Scharlach, thanks for posting.
I already bought two nokia 3210 vibra motors(4x8mm), will they be strong enough?

I also wonder about choosing the right SMD pot, they make much resist while being turned and this reduces speed and torque a lot. Did You try to mod them anyhow?
Jan 10, 2008, 06:00 AM
Registered User


For my experience in work with diy servo you have to use 4x8mm motor 24 ohm or 4mm motor 13ohm.Please verify the ohm between the + and - of your motor.Ivan
Jan 10, 2008, 06:24 AM
For Sale-everything over 250 g
Hi scharlach,
Thanks for posting you servo, it looks very nice! I was working on doing a similar servo but with a worm drive. My problem was the shaft connection to the pot, can you show how you did yours?
Edit: On closer examination of your parts picture I see how you did it.
Jan 10, 2008, 06:42 AM
A.K.A sir Crashalot
methuso's Avatar
For trimpot, would a Vishay TS3Y do ?

(Im Electically challenged)


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