What is this mechanical gadget called?

Most commonly seen on BMX bikes, there is an apperatus that provides a swivel-like braking system. It is two discs lying flat on one another, with a lazy-susan type ball bearing system. It allows a force on one, to be transmitted to the other, while still allowing a spinning motion. It basically makes tangled brake lines a thing of the past. Think of it as a lazy-suzan with connectors at either face, they can be pulled up or down, but can still spin.

I’m sure there’s a bike part name for this, what I’m wondering is if there is a mechanical name for this type of device. ME dopers?

This site calls them Gyros.

That answers the first part of my question, thanks. I’d really like to know if this is a device commonly used by ME’s though.


Besides bicycle brakes, I can’t think of any other application where cables rotate around a shaft. The closest type of application that I can think of is the clutch sleeve and shift fork used in manual transmissions, but that’s a linkage setup.

It is somewhat analogous to a universal gear, although it is clearly not that as it is used to avoid, not transmit, rotary motion.

I tried using Google to look up universal sleeve and rotating sleeve (and had to resubmit my search to include “-sex” to eliminate some stuff I’d have rather not encountered), but I did not find any general terms to match the bike gyro.

Another analogous application is the thrust plate that permits vertical motion around (and unaffected by) a rotating axis, but that is a specific device rather than a generalized concept.

Although I don’t work as an engineer, I have a mechanical engineering background. I don’t recall ever adressing this type of part in a generic sense though. For the most part, we didn’t refer to somewhat complex assemblies like this with any kind of stock name, rather we would just describe it (as you did quite well in the OP!).

There is a similar component used in helicopters that allows the rotors to turn while transmitting control inputs to the individual blades. Obviously the helicopter version is made to a much higher standard and is a bit more complex. I believe this part is called a ‘swash plate’, but I dont think I’ve ever heard the term used outside that context.

Funny thing though, I had a roomate for several years that worked in a bike shop. I don’t think I ever heard this device referred to in any way other than ‘that rotating brake thingy the BMX bikes have’! I don’t think his shop dealt with BMX stuff very much though.

Wouldn’t this just be a bearing assembly? I’m specifically thinking of ball bearings, where there’s an internal ring attached to the rotating bicycle wheel, a raceway with lubricated balls, and an outer ring attached to the stationary brake cables. Ball bearings aren’t just used for BMX bikes, of course; you’ll find them any time a shaft has to rotate against a fixed surrounding (or vice versa).

Howstuffworks.com article on bearings.

Crap, just re-read the OP, who obviously understands ball bearings. Anyway, I think “ball bearing system” is probably pretty much the best description/generic name you’ll get for it.

“swash plate” is a standard term for a collar that surrounds a rotating shaft and is used to feed either linear or tilt motion from the non-rotating part to the rotating part. the term can also be used for an endplate on a shaft that accomplishes the same thing.

Helicopter rotor heads are a common application as are constant-pressure / adjustable-flow-rate pumps.

Some are essentially 2D cams using springs & followers for the return motion. Others are positively connected for positive force and displacement feedabck.

I believe that in the BMX world they are known as ‘spinners’

Gyro is a name for a particular type of brake-spinny thing like you describe. I’ve also heard spinner and and older type called a Rotor. The Rotor style was cool in that it used regular brake cables. Break a Gyro type and its about $15-20 for just the new Gyro cable. I believe the Rotor type was made by a company called ACS.

Former bike mechanic and vintage BMX fan checking in.
Someone please ask me about my oldskool Hutch!

Please tell me about your oldskool Hutch.

(ntucker, proud former rider of a humble-but-solid Redline 500a with original (US-made) CW bars, Ukai shiny-side rims (can’t remember hubs), Tuf-neck, Tioga Task Force cranks + chain ring, Oddyssey Pitbull brakes, Dia-compe two-finger levers, beartrap pedals, headset and bottom bracket rebuilt almost weekly and clean enough to eat off. Serial number G0584 4639191. :slight_smile: )

Hmm?..Wellll, I don’t usually…I suppose I cooould…

Ok, its a '83/'84 Hutch ProRacer (19" top tube), perfect Hutch chrome, USA made. I also have the shiny Ukai rims (with the large letter decals between the spokes) and old GT flipflop cartridge bearing hubs, period-correct DK neck and pedals and the vintage Redline Flite Crank (180mm, single pinch bolt) I couldn’t afford when I was a kid. I’ve been shopping around for a Hutch fork but they’re really, really expensive and I’ll keep the Auburn one on there until then.

I’m 27 and I’ve had this bike for about 10 years. I steelwool it a couple times each summer to keep the shine on. I rode it tonight to school and back and love it alot. I even think the serial number is cool: 1234465.

Thanks for asking!

I am a mechanical engineer but have not come across a name that is readily applied to this type of device in academia.

In my industry we use them in certain applications and we use the term “slip ring”.

From an engineering standpoint, the concept is rather straightforward and takes on different naming schemes based on the implementation. I think this may be why there are so many different names around.