Gyro stabilizers

[MapisM]

Agree all that, although the 24v backup pump option would also need some smart switching (or at least i'd need a generator shut down alarm)

No need to invent anything particularly smart, I reckon.
Just put along the 24V pump wiring a "normally on" relay, actuated by the same 220V of the gyro.
As soon as you turn on the gyro switch, the relay goes off.
You turn on also the 24V pump switch, and nothing happens (because the relay is cutting the line).
If and as soon as AC goes off, so does the relay, hence turning the 24V pump on. :encouragement:
Btw, you might attach to the very same relay also an alarm, if you want to be alerted of the missing AC power...

 

[MapisM]

Also the bearing loads change between thrust bearing loads and rotational bearing loads, due to gravity, as it prescesses.

Good point. I suppose that's bound to affect the bearings wear and tear too, not just the noise.
Makes me wonder if anyone has yet considered to build a maglev gyro...

 

[grumpy_o_g]

Good point. I suppose that's bound to affect the bearings wear and tear too, not just the noise.
Makes me wonder if anyone has yet considered to build a maglev gyro...

We have, or possibly had, magnetic bearings in some the DRUPS (diesel rotary UPS, basically ruddy great flywheels that have enough momentum to power the generators in a datacentre backup system long enough for the diesels to kick in). Ironically they had a battery to power the magnetic bearings in the event of power failure so I suspect that's one reason it's non-starter for something like the Seakeeper as a power loss could trash the thing even quicker than losing the cooling system. In fact just getting power to the main bearing through the cages adds a layer of complexity I would imagine. The other thing is that, whilst rotational speed is mostly irrelevant to magnetic bearings they don't like being overloaded by a force that's not in line with the shaft. Everything's fine no matter how small that gap but, once metal hits metal you've got two surfaces that weren't designed as bearings graunching against each other. I'm sure the technology will get there soon, especially as passive (non-powered) bearings are advancing rapidly, but it's not there yet as far as I know.

 

[Portofino]

In post# 56 Nick reports bearing failure shortly after Geny problems attributing it to suspected lack of water cooling ?
In post # 60 eludes "5y ,2000hrs "
Firstly does anybody know from SK what the av life is ,expected of the main bearings in terms of hrs ? Is there a strap line figure banded about ?
Are there any preventive maintainance recommendations from SK ? I,am thinking lubrication issues here -dunno -just find it hard to understand having spent a lifetime working with instruments operating from 30,000 to mostly over 3-400,000 rpm
( hundreds of thousand ) where bearing integrity is critical .The higher the rpm the shorter the life -months or even weeks !
It's not just cooling ,another important arguably in my book more important from experiance is lateral load and balance .
A very slight imbalance ,so slight that humans don't notice over the general hubris of the machinery at constant ,high rpm (Nick says 2000 hrs ) -- cause damaging oscillations ,which will eventually prematurely wreck the bearings .

Just to be clear I,am not talking an imbalance of sufficient magnitude that shakes the boat to bits -ie you notice .
And the damaging occilations occur at high rpm for sustained periods -hrs on end .

The more lateral load -pressing sideways if you like at high rpm on the bearing housing is not conducive with extended life .So if understand how they work correctly -gyro stabs ,then sizing on the edge ,ie a smaller one will be working harder than a bigger -next size up - Begs the Q is the maths re sizing correct ?

Interesting to see ATBE after a bearing change -how long the next set last -with or without the odd intermittent water flow incident ?

 

[grumpy_o_g]

In post# 56 Nick reports bearing failure shortly after Geny problems attributing it to suspected lack of water cooling ?
In post # 60 eludes "5y ,2000hrs "
Firstly does anybody know from SK what the av life is ,expected of the main bearings in terms of hrs ? Is there a strap line figure banded about ?
Are there any preventive maintainance recommendations from SK ? I,am thinking lubrication issues here -dunno -just find it hard to understand having spent a lifetime working with instruments operating from 30,000 to mostly over 3-400,000 rpm
( hundreds of thousand ) where bearing integrity is critical .The higher the rpm the shorter the life -months or even weeks !
It's not just cooling ,another important arguably in my book more important from experiance is lateral load and balance .
A very slight imbalance ,so slight that humans don't notice over the general hubris of the machinery at constant ,high rpm (Nick says 2000 hrs ) -- cause damaging oscillations ,which will eventually prematurely wreck the bearings .

Just to be clear I,am not talking an imbalance of sufficient magnitude that shakes the boat to bits -ie you notice .
And the damaging occilations occur at high rpm for sustained periods -hrs on end .

The more lateral load -pressing sideways if you like at high rpm on the bearing housing is not conducive with extended life .So if understand how they work correctly -gyro stabs ,then sizing on the edge ,ie a smaller one will be working harder than a bigger -next size up - Begs the Q is the maths re sizing correct ?

Interesting to see ATBE after a bearing change -how long the next set last -with or without the odd intermittent water flow incident ?

Rotational speed, flywheel mass and speed of precession are the three factors that will determine the lateral load on the shaft. Basically the greater the force exerted to stop the boat rolling the greater the force acting at an angle to the shaft's centreline. In that sense the size of the gyro is irrelevant, it's the force exerted to precess it.

 

[Portofino]

Rotational speed, flywheel mass and speed of precession are the three factors that will determine the lateral load on the shaft. Basically the greater the force exerted to stop the boat rolling the greater the force acting at an angle to the shaft's centreline. In that sense the size of the gyro is irrelevant, it's the force exerted to precess it.

Agree hence
The "more lateral load"
A bigger one will have bigger bearings for that same amount of precession required to steady the boat .
A smaller be could quite well gave the necessary precession ,but it's at the top of its game with little headroom with that same force on much smaller bearings = lower life .

Just not convinced bearing failure is linked in this case to apparent lack of water cooling . Remember some gyros don,t need water cooling and your bearings in a typical internal combustion engine or Jet engine are subject to high temp .

Exploring other possible reasons

 

[jrudge]

Aside from the why I suppose the big question is how much and how hard to replace?

Lets face its a VERY large mass rotating at 10,000 rpm for 2000 hours is pretty significant in the bearing world so a failure is perhaps understandable at some point in time. Lets face it wheel bearings go etc.

Nick - are you prepared to say the bill and just how difficult this is to do ( i.e. how much of the boat needs to be taken to bits)?

 

[Nick_H]

Nick - are you prepared to say the bill and just how difficult this is to do ( i.e. how much of the boat needs to be taken to bits)?

No problem. The bearings cannot be replaced in isolation, so you have to buy an exchange sphere. The cost is USD15k + tax + shipping. Removal of old and installation of new is EURO 8k + tax in south of France. Seakeeper absorbed the cost of return shipping of the old sphere. They offered a very keen deal on upgrade to an SK9 instead of exchanging the M8000 sphere, but it didn't suit my requirements.

Above is all for a 30T boat size, and I assume the costs would be lower for 20T boat size, as discussed in this thread.

 

[Deleted User YDKXO]

No problem. The bearings cannot be replaced in isolation, so you have to buy an exchange sphere. The cost is USD15k + tax + shipping. Removal of old and installation of new is EURO 8k + tax in south of France. Seakeeper absorbed the cost of return shipping of the old sphere. They offered a very keen deal on upgrade to an SK9 instead of exchanging the M8000 sphere, but it didn't suit my requirements.

Jeez thats a hell of a cost. Are they definitively blaming the bearing failure on the cooling failure? Are the bearings directly cooled (and lubricated?) by water? What is the normal expected life of these bearings?

Sorry to hear about this. You must be really pissed off

 

[jfm]

Crikey Nick, that's a huge % of the whole new gyro - hardly any change from $30k. I've often wondered whether the installed fleet will start needing expensive repairs, with the result that these high bills become common knowledge. My worry is that the labour cost is going to be high because these things are installed in places that are hard to reach, but yours is high despite very simple access in your boat.

The parts cost is mind blowing. The bearing set in isolation should be less than $500 yet the need for a new (exchange) sphere is multiplying that. Obviously the sphere has to be split and re-vacuumed, but the need for a new one beggars belief.

 

[MapisM]

Jeez thats a hell of a cost.

Positively +1, puts the whole attractiveness of gyro stabilization in perspective... :ambivalence:
Otoh, 400 hours/season sounds a lot. I guess you must have found the system very effective, to keep it running that much!

 

[jrudge]

No problem. The bearings cannot be replaced in isolation, so you have to buy an exchange sphere. The cost is USD15k + tax + shipping. Removal of old and installation of new is EURO 8k + tax in south of France. Seakeeper absorbed the cost of return shipping of the old sphere. They offered a very keen deal on upgrade to an SK9 instead of exchanging the M8000 sphere, but it didn't suit my requirements.

Above is all for a 30T boat size, and I assume the costs would be lower for 20T boat size, as discussed in this thread.

Gulp ... so glad i asked that question.

Nothing to add to other posters other than bill shock!

The exchange parts are daft given it is to an existing customer and is ... exchange ...

 

[Deleted User YDKXO]

Positively +1, puts the whole attractiveness of gyro stabilization in perspective... :ambivalence:

It does indeed. That is why I asked NickH what the normal expected life of the bearings is because a $30k bill every few years significantly increases the overall cost of a SK gyro

 

[stillwaters]

Very sorry to hear about your M8000 problem NickH, but I'm grateful that you've shared the info, as I've just been considering buying a boat with an M8000 of similar age to yours fitted in it. In fact, in the absence of little currently for sale with fins, it was the gyro which attracted me to the boat in the first place. Strangely not quite as attractive, suddenly though.
However, I've also recently discovered that the relatively new Sleipner SPS55 actuators may well be compact enough to retro fit into my existing mobo, which would then enable the fitting of their curved zero-speed vector fins, which are claimed to be far more efficient than flat fins. So far, I've only been given ballpark figures, but am led to believe that the supply and installation cost would not be hugely more than fitting an equivalent gyro, which in my case would be a Seakeeper 5 at around £50k max. The equivalent Sleipner fins are the smallest 0.65sq.m. ones, which according to their website, they even obtained very impressive results with on a Princess 56 ( 97% roll reduction at 11 knots and up to 72% at anchor, and that's with the smallest fins!!!). And all running via a relatively small power pack unit off the generator.

 

[NGM]

It does indeed. That is why I asked NickH what the normal expected life of the bearings is because a $30k bill every few years significantly increases the overall cost of a SK gyro

I happened to speak with Sk today regarding their current models. I was told the latest models require no cooling at all during spool down. So once deactivated the genset can also be turned off immediately, obviously implying any genset failure that shuts down the SK will not cause any damage. One wonders if this was a high priority fix due to previous reported problems.

 

[jfm]

Very sorry to hear about your M8000 problem NickH, but I'm grateful that you've shared the info, as I've just been considering buying a boat with an M8000 of similar age to yours fitted in it. In fact, in the absence of little currently for sale with fins, it was the gyro which attracted me to the boat in the first place. Strangely not quite as attractive, suddenly though.
However, I've also recently discovered that the relatively new Sleipner SPS55 actuators may well be compact enough to retro fit into my existing mobo, which would then enable the fitting of their curved zero-speed vector fins, which are claimed to be far more efficient than flat fins. So far, I've only been given ballpark figures, but am led to believe that the supply and installation cost would not be hugely more than fitting an equivalent gyro, which in my case would be a Seakeeper 5 at around £50k max. The equivalent Sleipner fins are the smallest 0.65sq.m. ones, which according to their website, they even obtained very impressive results with on a Princess 56 ( 97% roll reduction at 11 knots and up to 72% at anchor, and that's with the smallest fins!!!). And all running via a relatively small power pack unit off the generator.

My brother (poster SilverDee) had SPS55/0.65msq fins retrofitted last year and we got closely involved with the installation. Very viable project, and they work very well. The SPS actuators are small, low profile, and it's easy to find space to fit them. You need a good installer because it isn't a trivial job.

I'd expect all in £60k not 50k GBP, btw, inc VAT, but that's a bit of a guess

While the performance of fins and gyros at anchor is similar and each has some advantages over the other but gyro probably wins by a small margin, the performance of fins in big seas is far far better than better than gyros.

 

[curiouskb]

I happened to speak with Sk today regarding their current models. I was told the latest models require no cooling at all during spool down. So once deactivated the genset can also be turned off immediately, obviously implying any genset failure that shuts down the SK will not cause any damage. One wonders if this was a high priority fix due to previous reported problems.

That is a very useful feature indeed. Just wonder what is the warranty period of SK in terms of hours used? And do they offer extended warranty?

 

[Nick_H]

Positively +1, puts the whole attractiveness of gyro stabilization in perspective... :ambivalence:
Otoh, 400 hours/season sounds a lot. I guess you must have found the system very effective, to keep it running that much!

Obviously i'm not happy about the big repair bill, but I don't regret buying the gyro as it transforms life at anchor and at displacement speed, so has been money well spent, and it kept a charter client coming back year after year so arguably has paid for itself.

In terms of expected life, I can't find any formal estimate from Seakeeper, the only info on their website is on this copy article which claims 8-12,000 hours.(https://www.seakeeper.com/wp-content/uploads/2016/09/SB_03-15-54_Adding_Stabilizers.pdf) They did issue a press release recently about a unit which had completed 18,000 hours on the original bearings.

A google search also didn't find any other owners complaining about premature bearing failure on Seakeeper gyros, and as they've now fitted over 5,000 units it does seem to back up their claim that my failure was an isolated occurrence, although if that's the case i'd have expected them to provide an exchange unit FOC on a goodwill basis, with just shipping and installation to pay, which I requested, but they declined.

The warranty is 2 years, 2,000 hours

It may be relevant that they've recently introduced a heavy duty / commercial range, which appears to be the existing range with max rpm downrated by about 20%. I don't know if they change any other parts. If I was buying a new gyro now I may opt for this option, and put durability above performance.

It seems you do get a bit more than new bearings with an exchange unit. From their website "each refurbished unit comes equipped with new bearings, brake system, and cooling system, as well as updated electrical components".

 

[Bouba]

Obviously i'm not happy about the big repair bill, but I don't regret buying the gyro as it transforms life at anchor and at displacement speed, so has been money well spent, and it kept a charter client coming back year after year so arguably has paid for itself.

In terms of expected life, I can't find any formal estimate from Seakeeper, the only info on their website is on this copy article which claims 8-12,000 hours.(https://www.seakeeper.com/wp-content/uploads/2016/09/SB_03-15-54_Adding_Stabilizers.pdf) They did issue a press release recently about a unit which had completed 18,000 hours on the original bearings.

A google search also didn't find any other owners complaining about premature bearing failure on Seakeeper gyros, and as they've now fitted over 5,000 units it does seem to back up their claim that my failure was an isolated occurrence, although if that's the case i'd have expected them to provide an exchange unit FOC on a goodwill basis, with just shipping and installation to pay, which I requested, but they declined.

The warranty is 2 years, 2,000 hours

It may be relevant that they've recently introduced a heavy duty / commercial range, which appears to be the existing range with max rpm downrated by about 20%. I don't know if they change any other parts. If I was buying a new gyro now I may opt for this option, and put durability above performance.

It seems you do get a bit more than new bearings with an exchange unit. From their website "each refurbished unit comes equipped with new bearings, brake system, and cooling system, as well as updated electrical components".

400 hours is only a little more than two weeks at anchor. The impression I get is that you are a commercial operator so is it possible that there has been some abuse from your clients or is your boat skippered? Because TBH the Italian jobbie is looking more and like a better bet.

 

[Nick_H]

Not a commercial operator, I just chartered the boat a few weeks a year to help with running costs. The skipper is well known to me and I trust him completely.