It's cool, but the fucker doesn't work (HDD Gyrocompass)

[bogan]

http://www.instructables.com/id/Gyrocompass-Dead-Reckonator/

My latest instructable. Any kiwibikers with ideas on how to make the fucker work?

262384

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[jonbuoy]

Hi mate,

I service marine gyrocompasses amongst other things, whats up with it? Usuall problems with marine north seeking gyros are rotor not up to speed or too much friction in the bearings or gymbals.

[bogan]

Yeh that's about all I can think of too. What size/speed rotors do they use in commercial ones?

[jonbuoy]

Yeh that's about all I can think of too. What size/speed rotors do they use in commercial ones?

Depends, older Models use quite heavy Rotors spinning at lower rpms the newer ones use much smaller rotors but higher speeds. Older ones are fully servicable down to the bearings, newer ones are factory overhaul only with only external gymbal and follow up parts servicable. Put it this way if you pick up the rotor casing of something like a Tokimec ES11 rotor running at only 10krpm or so from memory (we measure rotor speed from the current draw and voltage on the rotor) you need a firm grip with both hands, if you turn it in your hands the bugger will do its best to fight you, surprising how much power is in them. Those rotors weigh a few kilos, your hard drive platter has nowhere near the inertia so your gymbal will have to be spot on. Best way to check bearings is with no rotor fitted to the gymbal, should be as friction free as you can get it. I've noticed a bit of fight back when picking up a hard drive but not much.

[wtf?]

Yeah, whats wrong with it?

If you want it to point the same direction on your desk, I assume you've made a compensation for latitude?

Earth rate or apparent wander.
Transport wander
Real, or random wander.

[jonbuoy]

Yeah, whats wrong with it?

If you want it to point the same direction on your desk, I assume you've made a compensation for latitude?

Earth rate or apparent wander.
Transport wander
Real, or random wander.

Won't need to worry about that unless its north seeking which is a lot more complicated, could work as a free space gyro with a gymbal and slip rings.

[bogan]

Yeh the plan was to have it north seeking. But from the example jonbuoy has given, there just isn't anywhere near enough rotational inertia in the rotor to overcome the gimbal friction.

I was going to get onto fluid damping and latitude correction later, but since the earths spin doesn't cause it to precess at all, there is no point doing either.

[Oakie]

Well I'm lost.

[wtf?]

but since the earths spin doesn't cause it to precess at all

sounds like real wander is far greater than apparent. either get better bearings or can you spin it up faster with more volts dude?

[bogan]

Well I'm lost.

Well then, I have just the product you are looking for, how would you like to know whether you are still heading in the same direction as before! This device can do that, and look good too. Order now and you'll also receive a reaming from our billing department :banana:


can you spin it up faster with more volts dude?

I like the way you think, I already tripled the voltage, which is a high as my motor controller will go (15V), though I've heard people get the motors up to 50V. Which might cut it, of course if a platter fell apart at those speeds there would be some other things getting cut too :nono:

[wtf?]

Well then, I have just the product you are looking for, how would you like to know whether you are still heading in the same direction as before! This device can do that, and look good too. Order now and you'll also receive a reaming from our billing department :banana:



I like the way you think, I already tripled the voltage, which is a high as my motor controller will go (15V), though I've heard people get the motors up to 50V. Which might cut it, of course if a platter fell apart at those speeds there would be some other things getting cut too :nono:

Alternatively, get a multi platter HDD unit. As multi as you can get.

I'd be surprised if it fell apart, they weigh f all and I reckon you could get a fair few rpms out of it. If in doubt, put a mudguard on it.

[bogan]

Alternatively, get a multi plater HDD unit. As multi as you can get.

Got six of them on there at the mo, double what it is supposed to have. And starting it is pretty tricky. Would probably need about 20 or 30 of the bastards to get it going, not overly practical.

[wtf?]

better bearings then. not an easy fix tho.

[mashman]

could you go bearingless and use an electromagnet? Or are you just going for the HDD one... coz I have no clue. Look like fun though.

[bogan]

could you go bearingless and use an electromagnet? Or are you just going for the HDD one... coz I have no clue. Look like fun though.

Yeh, was a HDD salvage project, upgrading the bearings sound like it'll blow out my $0 budget!

[wtf?]

model aeroplane pilots use cheap as frictionless magnet balancers for their propellors. may be you could adapt one to suit you?