Looking for the Smallest physical size Servo

[george]

Hello
I am aware of the SG90 mini servos BUT I was wondering IF there was anything Smaller that can be used in small R.C subs so I guess metal gears should be available OR not?
Please include a link to a source in your reply.
Thanks
George

[He Who Shall Not Be Named]

https://www.ebay.com/itm/1-5g-Micro-...58248f88426604

[Subculture]

Another option are these if you want a more conventional rotary output plus a little more torque- https://www.banggood.com/2Pcs-1_7g-L...r_warehouse=CN

Compared with an MG90 (metal geared SG90) and a 3 gram diamond servo.

[Bob Gato]

These are probably the smallest true servos you'll get (only .3" wide)-so small-no screws holding it together-but quite powerful- there are smaller available but they amount to an electromagnet and two tiny magnets (used for indoor RC )

[Bob Gato]

Sorry I couldn't add the link also in the above post...

[george]

Wow, Thanks to ALL for your replies. I have a "Crazy" 1/35 scale Bronco Seehund XXVIIB/B5 submarine that I would like to make into a Static diver BUT it`s WTC is max. diameter of 1" O.D I think. Time to start hunting for SMALL GUTS for it.

[Bob Gato]

You should go to this guy's you tube channel and look thru what he's done-here's a ballast system using syringes...

[Bob Gato]

Or this...

[george]

Hi Bob
Thanks for posting those two. I really like the first one. I understand the syringe connections BUT I don`t see what his electronic control is.
Also I could NOT find his main website, would like to see his work in progress BUT got to figure out how to translate text to English.

[Subculture]

He’’s using mini servos to drive pistons back and forth. Pros and cons to this. It’s simple and cheap, and you get built proportional control. However the mechanism isn’t self locking like a jack screw, so the servos will be straining to keep the pressurised pistons in position once retracted inside of a wtc. If a valve was placed in line to pinch off the water, then the servo could be shut off and have an easier life, alternatively a jack screw could be used with a consequential loss of efficiency to prevent overhauling, but no check valve needed- the servo would need to be dismantled and some gear stages removed, plus mods to the feedback pot. A second snag with the system shown is that the linear throw of the piston is very restricted, so tank volume will be tiny. Okay for some boats perhaps or trim tanks. Better throw can be obtained using the afore mentioned jackscrew, or by using a rack and pinion on the servo, with mods to the feedback pot to allow a much longer throw..

[Bob Gato]

Its an easy translation-watch it in Google and select "translate"-this is the guy who brought us "the submarine on a selfie stick" ( https://www.youtube.com/watch?v=ITETqmNFqHM ) and he seems to specialize in micro subs-I find his ideas very refreshing..

( https://www.youtube.com/watch?v=WuddI-FnYFA )-this is pretty cool

[Bob Gato]

Go here for more of his YouTube videos ( https://www.youtube.com/channel/UCZJ...bEWaaYPFywUjCA )

[george]

Hello again Bob & Subculture. Thanks for the replies and extra links. Very informative. Subculture I have to say that yes I agree with your comment that jack screws are more efficient BUT the only problem I see with them is where is the room for the end of the jack screw in a small WTC?

[He Who Shall Not Be Named]

Hello again Bob & Subculture. Thanks for the replies and extra links. Very informative. Subculture I have to say that yes I agree with your comment that jack screws are more efficient BUT the only problem I see with them is where is the room for the end of the jack screw in a small WTC?

Employ bearing stops to prevent linear travel of the screw. The piston is threaded to the screw. As the screw rotates it jacks the piston back and forth. Piston O-ring friction prevents rotation of the piston.

David

[Subculture]

I said that jack screws are less efficient, not more. If you use a normal v-thread, like all commercial piston tanks and most diy units, they're only about 10% efficient, meaning you lose 90% of your power in friction. Conversely rack and pinion are over 90% efficient, meaning you can use a much smaller motor for equivalent force, but the mechanism can easily overhaul.

For a mechanism to be self locking it has to be under 50% efficient. All this information is readily available online- school level physics.