Worm Drive Servo?

[Tuner]

I am looking for a hobby servo that uses a worm drive. I have seen one kit that allows you to hook a continuous rotation modified servo to it.

Im looking for something that is a fully proportional servo that uses a Worm Drive. Small compact like normal hobby servos.

For those not familiar with what a Worm drive is its just like a screw drive garage door opener only it rotates a gear rather than move a nut linearly. The nice thing about a worm drive is it naturaly has a very High Holding Torque because the only way to rotate the servo is to turn the screw and that can not be done from the main gear. Though it is still possible to rotate the main gear(it depends on the pitch) from the outside it takes a lot of force to even slight rotate it so the servo has very little problem holding its position.

For VTOL aircraft with Rotating PowerPlants this is a MUST!!!
Heli guys would love this also due to its high holding torque

I have a design to replace a Hitech 5995TG gear box but I dont know anyone who can make me gears this small?

I am considering building my two gearboxes (one will be linear one will rotate) to go on to the Hitech servo in place of its gear box.

Any Ideas?

I am considering contacting Hitech to see if they will manufacture my design or point me to somone who can, anyone have a contact?

[rdresch]

Tuner, There is one problem with worm gears. They have a tendency to wear, though I doubt that would be problem for a tilt mechanics, unless you use it for pitch control also. It would probably wear and cause slop at that point. Acme precision threads (available from McMasterCarr) are one option. With geared pot should work. Smallest I could find was about .215 diameter. One turn gives about 1/2 inch movement. If your model is small and lite this is to heavy. What kit did you find? I'd be interested.
Rudy

[Hepdog]

I don't know what size you are looking for, but if you take apart any older CD ROM drive they ususally have a very nice 4"long worm shaft that opens the tray. Sometimes brass but occasionally you get lucky and its SS. :D

[Terry S]

worm drives dont wear if they are made right. Just look at the hard work your car wiper motors do.

Terry

[GWS4CEO]

GWS had done some special servos in other industry application. :)

You can contact us: service@gws.com.tw

[Tuner]

The chior leaps into action with a booming praise of GWS ;) THANK YOU I will take you up on your offer.

Thankyou I have a CAD desing of my own worm drive gear box using the base motor and controller from my hitec 5995TG servo.


Look to this thread for updates.


I will find out if GWS is interested in helping but my intention is to build a product line of several different worm drive based servos and sell them. It will probably start off as a nonprofit venture to pay for development costs or something like the Crocodile Brushless motor project.

* Linear Output Shaft Worm Servo
* Rotating Single Ended Output Shaft Worm servo
* Rotating Double Ended Output Shaft Worm servo
* Rotating Double Ended Differential Output Shaft Worm Drive
* 2in1 Rotating Double Ended(independant rotation) Output Shaft Worm Servo

These will be very popular among robotics guys trust me.

I basicly need 2 version of them a Micro and a larger high powered&speed standard size.

I am concerned about wear as worm drives do wear faster but its all about materials used as certain materials when used together have a highly reduced friction. Like carbon and metal though a micropolished surface is helpfull also but not happening for this type of application.

scott

[rdresch]

Tuner,
I wish you well in this endeavour. I can build a one off of whatever I need. My project is large, 1/10 scale. This is not a option for the smaller electric power VTOL. I am sure there would be many uses for these servos the power savings would be enormous. I've got mine working now using the hitec robot servo, which will suffice for testing. Still eventually a precision acme thread or worm gear will help servo life enormously. I have the acme thread and am working on a new design for the future. I just need to get this project going before the V22 is out of production.
Rudy

[Scott J]

Stock Drive Products:https://sdp-si.com/eStore/ has all kinds of gears. Also Servo City has gearboxes for servos:http://www.servocity.com/html/robotzone_servos.html

Scott

[rdresch]

http://www.wes-technik.de/English/light_ng.htm Mini screw drive servo. Should work for all the smaller VTOL.
Rudy

[Tuner]

All the stuff from servo city is to big and all the stuff from Stock Drive Products are closer to the size I want but still twice as large as is needed.

Thanks for the Small Worm Servo Links!!!! I could use these for other aspects of my projects I am sure somone can use this fore their VTOL Asprey or something?
THANKS.

Unfortunately I dont just need a linear worm servo.

Thanks!!!!!
Great links

[v22chap]

Here is a url to 1/8" lead screw material,, thought I had some smaller yet but can't find it right now,, scroll down about to bottom for the small ones.

lead screw material (http://www.smallparts.com/products/descriptions/LSX.cfm)

[v22chap]

Here ya go .05 mm series lead screws ,, not much more than the size of a plastic headed bulletin board tack.The outside screw dia on the smallest one is 1.8 mm dia. and they range on up to 14 mm dia
Think this might do ya ..... ;) :D :cool:

[rdresch]

Larry, I give up where is the link? I just found a servo from HITEC that is a winch servo. Up to 3.5 turns. Check it out on servo cities web page, under Hitec servos, winch servo. It is a full size servo.
Rudy

[v22chap]

Crap ,,Sorry that happens when the hair starts to go ,,and whats under the hair starts to go too ;) :D
This unit might be good for your setup too as they have some a little bigger also
Here it is :
micro leadscrews (http://www.congareebooks.com/tpa/kss_data.php?country=eur&menurefnum=154&menuref=1)
Larry

[vtolman]

Before the servo gear boxes came available
I geared down a similar specs hitec HS-725BB sail winch servo with its 3 1/2 turns with a 5:1 ratio and the results were huge torque with no slop and a strong hold, giving about 3 to 4 secounds for 180 deg rotation on the output 72 tooth gear or 7 secounds for about 160 deg rotation.

I made a simple round aluminium bush with 2 small screws mounting onto the top of the round hitec servo arm, the shaft of the 14 tooth pinion was then set screw held into this bush.

My JR PCM9XII TX can slow this down differently for inbound or outbound transition tilting. (faster inbound)
(project was a 12lb vtol with a single saito FA-180 throwing a 18 x 5 prop)
Kingsley

[flypaper 2]

I built a set of retracts from electric screwdrivers turning 3/16 cleaned up threaded rod. Two AA nicads for power. more than enough to lift 7 in. wheels. They're in a scratchbuilt, 9 ft.span FW 190 D9. Wouldn't be hard to make them smaller. Thinking of building a Canadair CL 84 Dynavert Tiltwing.

[rdresch]

The screw drive has some big advantages for retracts and slow moving mechanics. I don't understand why more aren't done this way. Good Luck on your tilt wing project. Keep us updated if ypu go for it. There are a lot off developments in electronics that are coming soon that will help.
Rudy

[Osprey WannaB]

Wen i had to fix my gear-box on my electric screw driver i was thinking of using it for tilting my pods.. It realy has some torque in it:D
Gud Luck,
Jamie

[Airboatflyingshp]

:Wen i had to fix my gear-box on my electric screw driver i was thinking of using it for tilting my pods.. It realy has some torque in it:D
Gud Luck,
Jamie


Thats exactly how some UK giant scale modelers power their UC retracts and or back them up ;) :D
I have a plan for a scale Supermarine Seagull 381 flyingboat it was an unusual plane in that it was powered by a single RR griffon engine with a contra prop set up and had a variable incidence wing 2.5- 12.5 degrees this was achived by a giant screw jack/worm drive.......so Im interested ;) as Ive been looking for gears and a way to do the wing :)
http://www.rcgroups.com/forums/showthread.php?t=474190

[v22chap]

That will be an impressive flying boat for sure.... :D
good luck on the build
Larry

[Airboatflyingshp]

Its a lovely flyer in original form by all accounts but I desperately want to get a working contra prop gearbox ....the variable incidence wing should be easy to build if a bit of an unknown in STOL take off landing mode....... use different materials one non metal for the thread and nut portions...advisable to avoid any chance of radio interference chatter ....don't forget that in your thinking for a VTOL ;)

You may wish to have a look at these guys if you haven't already seen the link
http://inter-ex.com/english/iexoverview1.htm :cool:

[electronker]

Have you seen these devices: www.firgelli.com/products.htm. They are basically a linear servo, ready to go. You can't backdrive them - they hold their position when power is removed. The one that is available now (PQ-12) has a pretty basic, raw interface (+5V/ground to extend, reverse polarity to retract, and you get an analog position signal back from the actuator). Their new models are supposed to have a standard RC servo PWM interface.

[rdresch]

That will really solve a lot of problems for many. Even though I have already built mine with a lagrge servo and externall pot with a jackscrew, this would be much simpler and lighter. Thanks
Rudy

[Thorn3]

You do realize that worm drives typically draw much more current than spur gear drives. For instance, a worm gear drive that will produce 120 inch lbs of torque using a worm drive, will draw well over 10 amps. A spur gear drive will produce the same output torque at only .4 amps. Take this into consideration. If holding power is what you are seeking, there are other, less current demanding methods.

[Thorn3]

In reading closer, are you wanting to make a worm gear drive, or a linear actuator? You could take a common servo and use a normal threaded rod in replacement of the output shaft. Remove the rotary pot as well and mount it externally. For bi-directional actuation, such as used for landing gear, you can use the bi-directional lead screw from a drawing compass, as well as the compass nuts.

[rdresch]

I already have a normal high torque servo with lead screw and remote pot. Still this is complex and very sensitive to any slop in the pot drive mechanics. By the way how much torque is 5n? My project is rather large and I am using a 330 inch oz servo with lead screw so it is extremely powerful. As for as the current demands if it only uses power when moving I don't care. If however it uses current to hold position I care a lot.
Rudy

[v22chap]

As for as the current demands if it only uses power when moving I don't care. If however it uses current to hold position I care a lot.
This is the exact reason that I also have a worm gear reduction in my tilt system with off micro switchs that keep the power off when not tilting and also hold the rotor disc in position .... the servo leadscrew system or even the large servo with remote pot ,, usually creeps forward if you stay in one position for a whole tank ,,, ( ie ,,hover out a whole tank) If I am not mistaken Rudy ,,you use about the same system except it doesn't have the worm gear reduction part.


Some where ,,and I can't find it now,, I ran across mini jackscrew retract systems .They were like 2 " long and looked to be used for mini airplanes and would have probably worked good on mini VTOL systems .... hope a search will bring them up again.
Larry

[rdresch]

here's what I am using now

[v22chap]

O.K. found the article ,,,it was in hard copy file... form MAN
and boy is my memory bad .... it is Likes Line for 1/5 to 1/4 to 1/3 scale birds ,,, 15 # to 55 # stuff . I looks to be using 1/4 " lead screw system and says they are made of T-6 aircraft -grade alum. They are also in the 300 .00 to 400.00 range for a set ,,but include adjustable micro switchs and very nice looking scale gear struts
Here is the url ,,, there are no pix on the page ,,I will try to scan the pix and post later. As I remember I was thinking they might be good for my use.
Likes line retract (http://www.aero-sports.com/likesline/)

[rdresch]

I checked into the linear actuators by www.firgelli.com/products.htm. Theses are cool. Includes a motor planetary gearbox overload switch and worm gear. All in one lite weight unit. The models for rc will be available in late Dec. Soon as they are I will try one. I Spoke to the manufacturer today and the stronger model is stout enough to lift a 10 lb weight. It also only uses current will in motion. Will report again in a few months
Rudy