Gyro build problem

[steamdaveParticipant @steamdave]

Slightly off topic; but the Sperry Mk.XIV gyro compass of the 1950/60s had a 56lb wheel and it spun up to 7000 rpm. The compass was mounted as near to the centre of gravity of the vessel as practicable in order to reduce movement of the 'machine' due to roll and pitch. Quite a fearsome beast when it was running at full chat!

Dave
The Emerald Isle

[MuzzerParticipant @muzzer]

Interesting experiment in low gravity. Not much effect from a small spinning plastic disk but interesting all the same.

[Neil WyattModerator @neilwyatt]

Thinking about my toy gyro, the problem looks like it's simply too heavy to get it up to speed easily with a bit of string. You need it to go as fast as possible but you can only put a given amount of energy in with one string pull, so a relatively slender flywheel with a modest rim you can really get shifting will work better than a fat one you can only get to a fraction of the speed.

[john carruthersParticipant @johncarruthers46255]

It's all proportional to the V^2 rather than the M.

[MichaelRParticipant @michaelr]

A home made Gyroscope and a novel way to get up running speed. Here

Mike.

[Michael GilliganParticipant @michaelgilligan61133]

As others have indicated; Clickspring's Gyro doesn't look suitably proportioned for scaling-down: At reduced scale it will need to be run much faster than a string-pull can provide.

Missile guidance Gyros were [before things went solid-state] typically spun-up by gas pressure, operating on turbine notches cut in the periphery of the 'wheel'. Have a look at the two monochrome photos on this page, and consider the possibility of milling notches in Clickspring's wheel … a short blast from a CO2 cylinder should do the trick.

MichaelG.

[Gordon WParticipant @gordonw]

I'm not sure it would be a good idea to spin these things, with plain bearings, to high speeds. I saw what happened when someone spun a ball-race up using the compressed air gun. I think this is the first cautionary tale I've posted.

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Gordon W on 14/12/2015 11:28:31:

I'm not sure it would be a good idea to spin these things, with plain bearings, to high speeds. I saw what happened when someone spun a ball-race up using the compressed air gun. I think this is the first cautionary tale I've posted.

.

Duly noted Gordon

Thanks for the prompt and very wise response.

My post should really have said 'consider the possibility, and the implications'

MichaelG.

[Ian S CParticipant @iansc]

Here's an aircraft instrument gyro.The turbine/ gyro wheel is either brass or bronze, and the conical point runs in a cup with three(I think) ball bearings, each end. The ball races are adjustable. Ian S C

[Roger HartParticipant @rogerhart88496]

Tried an experiment, span up a toy gyro with 3/16 shaft using string. On the tacho this got to 4500rpm but dropped fairly quick to 3000. I reckon you would be lucky to do much better. Using the criterion of a gyro that will sit horizontal and do 1 rev/sec with a rotor speed of 2000rpm the 75mm diameter rotor is marginal – OK if turning a bit faster but losing energy fairly quick.

The snag is that a toy gyro to sit horizontal on a little tower is pretty challenging, the weight (mass) cannot be too much but you need the mass to get the gyro couple – and the practical rpm achievable is in the 2000 to 3000 region. This design criterion is quite different from designing a gyro compass.

As a kid I remember a pretty good gyro that was about 70mm diameter with a thin ish rim – but made of lead painted in shiny brass lacquer – probably not allowed now….

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Ian S C on 15/12/2015 11:40:25:

Here's an aircraft instrument gyro.The turbine/ gyro wheel is either brass or bronze, and the conical point runs in a cup with three(I think) ball bearings, each end. The ball races are adjustable. Ian S C

.

Ian,

Yes that's an excellent bearing arrangement [also once popular on 'unipivot' pick-up arms and some electric clock balance wheels] … Can't recall the proper name for it though.

You might find this Patent of interest … same concept on a much larger scale.

MichaelG.

[Ian S CParticipant @iansc]

The bell crank on one of my hot air engines uses the bearings from a tone arm, mainly because they were there and needed using. the bearing on each side is in the brass bit with the lock nut. This motor(similar any way) appeared in ME a number of years ago as the winner of the Gnat power section, it was published first as a BETA type, then later as a GAMMA. It has a 5/8" bore, and will drive the generator with enough power to run a 3v radio.

Ian S C

[the artfull-codgerParticipant @theartfull-codger]

Anyone remember the linaze giroscope that used to be advertised in model engineer quite a few years ago, it had ball bearings.?

[Neil WyattModerator @neilwyatt]

Interestingly I picked up a rather large (old) external HDD yesterday while it was running, and I could feel it twisting in my hand.

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