ceramic bearings

[izitbrokeyet?]

I think you guys have hit on a good point. I believe that one could go with a closer fit and higher abec rating on a set of bearings if they could take the axial load off the crankshaft. I’d like to see a drive setup that could free up a motors front bearings to deal only with the crankshaft rotation/ balance. The lower friction drive could also resolve the thrust loading into the hull more efficiently rather than through the motor/motor mounts.

this could free up some of that rear plate scuffing and axial loading on front and rear bearings.

 

[TimD]

I have been using lead teflon bushes in struts for years.  Correctly maintained they seem to be fine.  The longer the strut the better though.  Allows less leverage on the stub shaft.  Bearings will last longer.

The performance issue is rotational friction, not longevity. If the argument is that the ceramic bearings offer a performance increase over good steel bearings, isn't it going to be hindered by the high drag part of the whole drive system - the strut and flex cable? After all, the shaft and prop are spinning at the same rate of rpm as the engine. The strut bushing and flex cable are acting as a brake on the engine bearings so to speak.

 

[izitbrokeyet?]

I have thought about using Angular Contact Bearings in the front bearing to directly resolve the thrust into the crankcase/ motor mounts/ hull.......only problem is that the thickness available on a .21 angular contact is 10mm while the standard thickness of a front bearing is 6mm.

I know it will fit but may appear to be a Jury-rigged setup

Anyone tried a fat ACB front bearing to resolve thrust using a standard flex drive system?

 

[EatMyShortsRacing]

I thought the whole point of square drive systems was to remove the axial load???

 

[EatMyShortsRacing]

I have been using lead teflon bushes in struts for years.  Correctly maintained they seem to be fine.  The longer the strut the better though.  Allows less leverage on the stub shaft.  Bearings will last longer.

The performance issue is rotational friction, not longevity. If the argument is that the ceramic bearings offer a performance increase over good steel bearings, isn't it going to be hindered by the high drag part of the whole drive system - the strut and flex cable? After all, the shaft and prop are spinning at the same rate of rpm as the engine. The strut bushing and flex cable are acting as a brake on the engine bearings so to speak.

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Lead Teflons do provide less drag than the bronze / brass bushing systems. The point in using longer stub shafts is to increase the life of the bearings so they dont start ot become inefficient. The brass bushing system is better for short struts because compared to lead teflons the lifetime of the bronze / brass system will be better. So the ideal situation is the long stub shaft with lead teflons.

 

[izitbrokeyet?]

I thought the whole point of square drive systems was to remove the axial load???

I agree....but it seems the squre drives have fallen out of favor for more elegant systems.

why is that?

The front deep groove bearings as I know it are designed for transverse loading and not for axial loading.

The standard flex system does resolve the thrust axially into the race on the race contact closest opposite the flex connection. This has the affect of changing the bearing fit while its taking up load to a tighter fit (slower fit).

I haven’t tried a squre drive but the ones I’ve seen have a good bit more spinning mass compared to a standard flex drive.

 

[EatMyShortsRacing]

I thought the whole point of square drive systems was to remove the axial load???

I agree....but it seems the squre drives have fallen out of favor for more elegant systems.

why is that?

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Elegant??? You mean simpler.... or even cheap and nasty!!!!

The only thing the cable/stub shaft combinations have got going for them is ease of installation.... Great if you have a stock of cables and props you are quite prepared to lose....

All that being said all my current Seaducers use that at the moment but future ones will be back to the Ferrule setups.

 

[TimD]

I have been using lead teflon bushes in struts for years.  Correctly maintained they seem to be fine.  The longer the strut the better though.  Allows less leverage on the stub shaft.  Bearings will last longer.

The performance issue is rotational friction, not longevity. If the argument is that the ceramic bearings offer a performance increase over good steel bearings, isn't it going to be hindered by the high drag part of the whole drive system - the strut and flex cable? After all, the shaft and prop are spinning at the same rate of rpm as the engine. The strut bushing and flex cable are acting as a brake on the engine bearings so to speak.

80436[/snapback]

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Lead Teflons do provide less drag than the bronze / brass bushing systems. The point in using longer stub shafts is to increase the life of the bearings so they dont start ot become inefficient. The brass bushing system is better for short struts because compared to lead teflons the lifetime of the bronze / brass system will be better. So the ideal situation is the long stub shaft with lead teflons.

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Again, The performance issue is rotational friction, not longevity.

Bronze / brass / lead teflon bushings are all high drag compared to a bearing. Think of the prop shaft being an extension of the crankshaft. Would you run a lead teflon bearing in an engine in place of a ball bearing?

 

[Don Ferrette]

Elegant???  You mean simpler.... or even cheap and nasty!!!!
The only thing the cable/stub shaft combinations have got going for them is ease of installation....  Great if you have a stock of cables and props you are quite prepared to lose....

All that being said all my current Seaducers use that at the moment but future ones will be back to the Ferrule setups.

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Properly maintained the conventional collet set up is far less failure prone. I've seen way more DNF's from broken/failed square drive parts than on collet set ups. Not to mention the collet set up is far cleaner (elegant?) than all that hoky crap hanging under your hull, but that isn't the point. You guys want to talk about parasitic drag of a bushing, take a hard look a those thrust washers needed on a square drive. I did & that's another reason I run the collet set up.

 

[EatMyShortsRacing]

I have been using lead teflon bushes in struts for years.  Correctly maintained they seem to be fine.  The longer the strut the better though.  Allows less leverage on the stub shaft.  Bearings will last longer.

The performance issue is rotational friction, not longevity. If the argument is that the ceramic bearings offer a performance increase over good steel bearings, isn't it going to be hindered by the high drag part of the whole drive system - the strut and flex cable? After all, the shaft and prop are spinning at the same rate of rpm as the engine. The strut bushing and flex cable are acting as a brake on the engine bearings so to speak.

80436[/snapback]

​

Lead Teflons do provide less drag than the bronze / brass bushing systems. The point in using longer stub shafts is to increase the life of the bearings so they dont start ot become inefficient. The brass bushing system is better for short struts because compared to lead teflons the lifetime of the bronze / brass system will be better. So the ideal situation is the long stub shaft with lead teflons.

80440[/snapback]

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Again, The performance issue is rotational friction, not longevity.

Bronze / brass / lead teflon bushings are all high drag compared to a bearing. Think of the prop shaft being an extension of the crankshaft. Would you run a lead teflon bearing in an engine in place of a ball bearing?

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Longevity IS an issue unless you want to add to your maintenance program.

Ideally ball races would be preferred but nothing is available in a small reliable affordable package so the choices go to the lead teflons or the bushings. Out of the two the lead teflons are better.

 

[EatMyShortsRacing]

You guys want to talk about parasitic drag of a bushing, take a hard look a those thrust washers needed on a square drive. I did & that's another reason I run the collet set up. 

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On my twin with square drive I have ball raced thrust washers. I also have collet with ferrule drive systems.

I think the failures with shafts usually can be attributed to maintenance or installation problems rather than the system itself....

 

[Don Ferrette]

I think the failures with shafts usually can be attributed to maintenance or installation problems rather than the system itself....

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Agreed. I think that applies to either, but I've still seen significantly more failures of properly maintained sq. drive stuff than conventional collet set ups. Not trying to start a debate but just sharing my observations over the years.

 

[shoboat]

Craig,

Do you balance your ferrules on your square drive set up? I think the collet

is the best way for me,add oil injection to your shaft and you are a winner. :lol:

Just A Little Humor,

Mark Sholund

 

[EatMyShortsRacing]

Craig,
Do you balance your ferrules on your square drive set up? I think the collet

is the best way for me,add oil injection to your shaft and you are a winner. :lol:

Just A Little Humor,

Mark Sholund

80474[/snapback]

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Hmmmm balanced ferrules???? on the balanced stub shafts??? with the balanced prop nut on the back????

 

[Jerry Wyss]

Craig,
Do you balance your ferrules on your square drive set up? I think the collet

is the best way for me,add oil injection to your shaft and you are a winner. :lol:

Just A Little Humor,

Mark Sholund

80474[/snapback]

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Hmmmm balanced ferrules???? on the balanced stub shafts??? with the balanced prop nut on the back????

80500[/snapback]

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Seem's exhausting, doesn't it? What happened to the 3/16 hard "music wire"

shaft and the little Prather or Octura "needle" or "roller" bearing "insert" into the

each end of the strut and holding the prop on with the "fuel tubing" idea?? :huh:

 

[Preston_Hall]

Square drive or collet? This shouldn't even be a question. Why would you put the load of the prop on a 3/8" diameter nonlubricated bearing when the load could be applied to a 1" diameter constantly lubricated bearing?

Sure, it would free up the motor. Only if the motor didn't have to turn the shaft. :lol:

I bet some people would see more speed if they just removed all that excessive grease they put on their shafts.

I still see that nobody has answered my question

The physics of the performance advantage comes from the lighter balls. The ceramic balls are 40-60% lighter than standard bearings

If this is true, which I agree, then just lighten your flywheel and use regular bearings. Right? Same thing?

So why use them? Any of the advantages stated here honestly don't seem to have bettered anybody's performance.

 

[izitbrokeyet?]

Yo Preston,

I spoke with the bearing guy yesterday and found out the following:

They ceramics are considerably smoother and rounder than steel (about 10 millionths less out of round than steel)

They have shape stability (they stay round inlieu of squashing out like steel balls do

They exert about 1/3 the force on the retainer (apparently this is a big deal I never knew of)

The balls exert about 1/3 the lateral load on the external race.

The ceramics don’t skid like steel...takes many more RPM before they start skidding

The reduced moment of inertia we already listed...turns out the spin up advantage is about equal in both the major axes and the minor axis.

 

[izitbrokeyet?]

on the ACB.....I'm thinking they would provide the best of both worlds...elegant flex collet system and resolution of thrust. I still think it would be worth trying if one could be found in a C3-C5 fit

KB

 

[Preston_Hall]

The reduced moment of inertia we already listed...turns out the spin up advantage is about equal in both the major axes and the minor axis.

So we could keep steel and lighten the flywheel for the same advantage.

Who knows if the steel balls skid now.

I am not trying to refute you but only asking "Why even try ceramic if you don't have to"? (preposittion)

If ceramics do indeed provide an advantage then there are probably only 1-5 people in the world who could take advantage of it.

 

[izitbrokeyet?]

So we could keep steel and lighten the flywheel for the same advantage.

Yes, but that would only help acceleration, not top end.

I actually think the acceleration advantage found in ceramics could be a negative compared to steel.

As an example.....I had some mod K&B 3.5's that could not handle a lightened flywheel unless it had a RPM rod in it….I’m sure there are others that have tried this as well. I don’t think it would ever be an issue in a Mac or a NR….just throwing that out there.

I am not trying to refute you but only asking "Why even try ceramic if you don't have to"? (preposittion)

P....I think there are very small advantages for sure in boats. I suppose only someone with a very high reving motor and deep pockets could take advantage of the top-end benefits of ceramics.

I'm thinking the advantages are going to only the top-end benefits in a hydro because of the ceramics because of decreased centrifugal loading on the retainer and balls Maybe some longevity benefits, but I cant qualify that yet. Maybe Ron Drake will be able to speak to the longevity since he’s been running his since February (ish) ’04. Two full seasons on a set of bearings would be impressive to me.