Before I describe the problem I would just like to say that I'm no engineer this is my hobby, all I know is from google or if someone told me or from books. Something obvious to you may not be obvious to me. Thanks

I want to move a gear with the shaft like they were one in one moment and in the other I want to stop the gear using clutch brake while continuing to rotate the shaft.

One way to achieve this is using air bearings which would be the perfect solution if they weren't so impractical because of the required compressor and other parts.

Second solution would be to use two clutches. One to connect the gear to shaft and another clutch to brake the gear when the first one is not connected but I don't want to use more than one clutch pack because they are expensive.

Third solution is to use sync cone but that is much slower than clutch and that is why I don't want to use it.

Fourth solution which I found is using a shaft mounted brake to lock the gear with the shaft but I'm not sure if this would count as a clutch brake and if it would lower the efficiency of the system as whole.

So my question would be is there a way to achieve the problem described without using more breaks or clutches (if shaft mounted brake wouldn't count as a break then that is also OK)? The perfect solution would be a bearing which I could "turn off" and let it rotate with the shaft but I'm not sure if something like that exists.

  • $\begingroup$ You need to provide a lot more info. Tell us exactly what you are doing and provide the specs on how fast and how frequently the gear needs to be toggled. There are hydraulic coupler devices that may be better suited to your needs. Does the gear need to free spin in both directions relative to the shaft, or just one direction? does the shaft have to transmit torque in both directions, or just one? $\endgroup$
    – Phil Sweet
    Commented Jul 8, 2019 at 2:45
  • $\begingroup$ A small marine tranny such as Hurth or Twin Disc can be had for a couple thou. $\endgroup$
    – Phil Sweet
    Commented Jul 8, 2019 at 2:47
  • $\begingroup$ Ok sorry. I am designing some sort of a transmission so the gear would need to be toggled couple of times in a minute. It actually doesn't need to free spin it just needs to be disconnected and when it is I would use clutch brakes to stop it so you could say it only needs to spin in one direction. The shaft transmits torque only in one direction. $\endgroup$ Commented Jul 8, 2019 at 5:14
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    $\begingroup$ I think the A/C clutch from Solar Mike and a separate brake would be your best bet. I've seen a cheap lawnmower that had a single clutch/brake pedal, and even it split that motion into two separate devices. (The "clutch" simply pulled a spring tensioner away from a belt, and the brake was a mini disc brake on the transmission output. My brother and I geared it way up to make a 5-speed manual go-kart...and learned a few things about designing to a price point.) $\endgroup$
    – AaronD
    Commented Jul 8, 2019 at 7:15
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    $\begingroup$ Okay, try looking at detent clutches (aka ball clutches). They are a type of overload disconnect. All you have to do is apply the brake. When you release the brake, the clutch will reengage automatically. link $\endgroup$
    – Phil Sweet
    Commented Jul 8, 2019 at 9:30

1 Answer 1


Yes use a electromagnetic clutch, often used on car a/c compressors to disconnect them when not needed.

When engaged they drive and freewheel when not energised.

  • $\begingroup$ Thanks for reply. But, for example, in an automatic transmission it is viewed as a bad thing to have many clutches and brakes. Would an electromagnetic clutch count like other clutches which are used in compound planetary gears to move and stop certain parts? Real life example would be ZF 8HP transmission uses 5 clutches in total. If they added electromagnetic clutch to their transmission would it count to total used? $\endgroup$ Commented Jul 6, 2019 at 17:09
  • $\begingroup$ Case international had electro-hydraulic clutches.. why is it important to count them? You need to work out if it will work in your design - which is not clear by the way. $\endgroup$
    – Solar Mike
    Commented Jul 6, 2019 at 17:17
  • $\begingroup$ Well, it's not important to count but it would be important to keep the number as low as possible. And yes it would work this is final piece of the puzzle so to say. $\endgroup$ Commented Jul 6, 2019 at 18:11
  • $\begingroup$ @DominikSerbinek if this helped, you should accept the answer or vote for it... $\endgroup$
    – Solar Mike
    Commented Jul 7, 2019 at 5:42
  • $\begingroup$ It helped I just wanted to ask you more about it. I upvoted when you answeredbut since I have less than 15 reputation it doesn't show $\endgroup$ Commented Jul 7, 2019 at 7:41

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