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Oct 12, 2002, 05:20 PM
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Mario's Avatar

Ultra Light 3 Gram!!! Servos. You can do it!

Looking for alternative light servos (similar to the ultra light Westechnik 2.4's) that I could use in indoor models in the under 20" span and 4 ounce range, I decided to take two inexpensive HS-50 servos and perform some surgery.

I know this is nothing new, and we've all seen, from time to time, people doing similar things to lighten up existing components in order to make it work with smaller and lighter models. But I decided to go further and even lighten the tiny gears by drilling lightening holes in them also. What I ended up is a servo that weighs 3.0 grams !!!, this also takes into account that I had to replace the potentiometer and servo plug wires with much lighter ones.

Here is what my servos ended up looking at 3 grams. The photos show the servos prior to replacing the wires with lighter ones and covering them with scotch tape, but you'll get the idea.


I really believe GWS is capable of doing similar and better as a package with their exisiting Pico servos to cut down weight. Cost could be kept the same, but would sure love to see something lighter. Manufacturing would require some additional pins on the injection molds to create the lightening holes both in the gears and cases and perhaps offer the servo only without the PCB, Offer the PCB (One board ONLY) with the Micro Chip programmed to work with up to 4 or more servos, for instance. Perhaps marry the receiver with the servo motor drivers, all in one board, to minimize having dedicated boards to each servo, a good weight saving and perhaps manufacturing costs as well. An 8 wire flex thin copper cable with an ultra light connector similar to that used in todays computers devices like CD Roms would be ideal for lightness and this would connect direct to the brain module (Receiver with servo driver circuitry).

I wish I was in the manufacturing of servos, but since this requires machinery which I don't have, I am passing my wishes and peraps those of a thousand other people to the Servo manufacturers. I am addressing GWS directly because I know they listen to people and have grown fond of their direction with model products. They also make excellent stuff at reasonable prices.

I'd like to hear GWS commetns. Do we have some hope?
______________________ ______

Meantime, if you care to take the time and become a "plastic" surgeon for a couple hours, you can do as I've done. You don't need a drill press or similar, a sharp Exacto hobby knife works if you take your time and plan the lightening hole arrangement and start with small holes and enlarge them little by little.

Later on if I have some time, I will talk about how I modified the GWS servos and did away with all but 1 gear and How I am planning on using the elelments from a precision multiturn potentiometer to build the feedback control on the model itself.

Comments are welcome.

Mario I. Arguello
Last edited by Mario; Oct 12, 2002 at 05:32 PM.
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Oct 12, 2002, 07:26 PM
Registered User
Great job Mario.
What potentiometer did you use?
I can't wait to try it.
Oct 12, 2002, 08:27 PM
Grand Poobah of Nothing
Trizza's Avatar
Impressive! I'm not brave enough to attack the gears though.
Oct 13, 2002, 04:13 AM
Registered User
Neat idea Mario.
I also like the idea of a linear servo using HS55 bits.
Need a linear pot thats already setup or an easy way of modifying an existing pot.
This one is about 2.6 gram.

Last edited by david_dewit; Feb 10, 2003 at 04:39 PM.
Oct 13, 2002, 09:56 AM
in persuit of low wing loading
Gordon Johnson's Avatar
Nice job. Is the 3.0g complete with the external wires, a plug, and a servo arm? I can't tell, but it sounds like you replaced the three thick wires inside the HS50. The two going to the motor are pretty thin already.

Oct 13, 2002, 02:35 PM
Only nerd in the village
Here is my modded HS-50. Not quite "Cheesy" (all the holes - get it?) as Marios but still quite light at 3.8 grams without servo horn. Solder directly onto RX.

Be careful when drilling holes in gears that they don't distort from heat.


Oct 13, 2002, 05:19 PM
Permanently banned
Mario's Avatar
Yes, all the wires from the pot and 3 pin connector were replaced with magnet wire. No connector used, the hook up to the receiver is direct soldered. I know my servo lightening holes look "cheesy" and although I have the machines to do perfectly spaced and drilled holes, I forced myself to do the holes with the tip of an Exacto hobby knife so that I could relate the experience to others with no special tools.

It works and don't be afraid to dive into this project, the most you could loose is the cost of the servo if you do something crazy like using a soldering iron to drill the holes and you miss and mess up the circuit board instead, and perhaps a bloody finger if you are not careful with the Exacto knife. Nothing will happen if you take the time, approach the project with a good attitude, choose a day when you are in good standing with your wife, or partner, sweetheart, dog, cat whatever, it helps use common sence, but just as a disclaimer, I am not responsible if you get hurt or loose warrantee on your servo (given), so let's be clear on that .

Dave, You got the most obvious idea after seeing a Westechnik servo, the question is, hey just take the motor and use a precision pot, but the precision pots (normally blue in color) I have found are not quite as smooth as the ones in the Westech 2.4 servos. But they are not as fragile either. I have not looked hard enough, I am sure I would find the right ones if I put the effort into it. Maybe someone already has it here in the US and we just don't know it.

I think we can essentially arrive at some compromise with a similar precision linear pot (The blue ones) and motor configuration as you show for about maybe the same weight if not lighter weight. Anything that has a true servo with feedback control is got to be better than actuators, but I don't want to discredit actuators as these can work extremely well in some applications.

The point here is working with an existing inexpensive servo and simply make it lighter. Servo manufacturers have the capacity, it is just a matter of time. I just can't understand why it is taken them so long to produce 1/2 size/weight HS-50 servos when Westeck has had already done the 2.4 servos for a while now.

I mentioned cost could be kept the same as for existing GWS Pico or HS-55 servos, I would not mind and I don't think people would either, so long as we reduce the weight by 50%, ideally. What do you alll say? Mr Linn?

Mario I. Arguello
Last edited by Mario; Oct 13, 2002 at 05:27 PM.
Oct 23, 2002, 08:57 AM
Fanfold abuser
Jgardner's Avatar

GWS opportunity

Yes. How about a great combo of motor, Rx/ESC with circuits for two servos, two very light servos, very light connections a la rffs 100, and a matching motor. It would all be optimized for 2-3 oz planes. The setup should be designed for the 145 Kokams and the next larger size.

The goal would be a widely usable set like the IPS A, quallcoms, pico gear combo so popular in so many designs.

A brick arangement could be effective, with a thin housing for the whole set (less the motor). Set the brick up for future production planes and a few existing easy rubber/FF design conversions.

We could reconfigure the components as needed.
Last edited by Jgardner; Oct 24, 2002 at 12:29 PM.
Jun 10, 2003, 08:49 AM
Registered User

GWS Servo?


You mentioned that you modded a gws servo? What does it look like and how much does it weigh?

Jun 10, 2003, 09:51 AM
Registered User


it's my news servos

Jun 10, 2003, 10:42 AM
Registered User
Small Servo's

Falcon kits (UK) are in the process of manufacturing digital feedback servo's weighing 1.5g.They will come with a JST plug.Expected delivery 2 months.The prototypes weighed as little as 1.3g.It will be rotary output.They are also producing a range of 0.25 module pinions and gears and self assembly gearboxes to suit a variety of motors.The prototype has been tested in a 43g helicopter with a conventional swashplate.
Jun 10, 2003, 10:47 AM
Registered User
Re Falcon
I omitted the website
Dr Chris
Jun 10, 2003, 12:36 PM
Registered User

Re: 2.6g...

Maulionc that's cool! Is that an HS-50? What all did you do?

Originally posted by maulionc
it's my news servos

DrChris: Any pics? Price estimates?

Jun 10, 2003, 12:40 PM
in persuit of low wing loading
Gordon Johnson's Avatar
Nice to see you on the Ezone. I'd heard about the servos. It's nice you have posted about them. It sounds like what we have been waiting for for some time. The 0.25 mod gears also sound nice. Please keep us posted.

Jun 10, 2003, 01:17 PM
Registered User
Your sick, Mario. You know that? I have a lot of patience, but nothing to that extreme. It looks very promising. If I had the time or any real reason to attack a servo like that, I'd probably only have it in me to do the case (which you did very nicely, I must add). As of right now, though, I haven't moved to anything that small just yet. 5.6g is small enough, at least for the next little while. Keep it up, you've got quite a few promising items on the way.

Nick R.

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