ceramic bearings

[Speedway]

Woa! Just checked this thread out. Ceramics are used in All forms of racing from Ceramic bearings (I have a set in my Highly modified YZ450) to Pistons (I have a ceramic piston in my YZ250. The Bearings take more of a load and I can bump my compresion up with no concern. They handle higher temps, dont chatter or scour and have a lower rolling resistance.

PS: In 71, Honda won every race in the 125 class with a 125cc In-Line 6 Cylinder (Pistons in it were smaller than my Big Picco's). The motor would rev out at 31,000 RPM (they said it could bench at 35K!) and the ENTIRE excersise for the motor development was CERAMICS and Less rolling friction. Oil volume was reduced to such a low amount in the motor that the film on the bearing surface was less than 3 micron.

PSS: Ceramics are also a form of "Semi-conductor", In other words, Energy is not Stored , in other-other words, energy is disipated, In real laymans terms, You get the heat out.

I can believe people still doubt Ceramics!

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.

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[Don Ferrette]

But as far as the flywheel weight needed for launch, I think mostly BS.

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Then try it. I have & yes you can go too far. <_<

 

[TimD]

But as far as the flywheel weight needed for launch, I think mostly BS. Peeps thought that back when there where big brass flywheels. If weight was good we would still be running brass flywheels. Also, your engine is not really turning any RPM at launch so again the weight of the flywheel is questionable to me.

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Before you say you think its mostly BS, have you tested it specifically? I have recently.

Heres the results of my tests on my current 21 rigger.....Novarossi Long stroke with Orlic crank. I'm now launching a prop with 50% nitro that was very hard, if not close to impossible to launch with the lightest flywheel and 60% nitro. Lightest flywheel and 50% I couldn't get away from the shore at all with the bigger props I'm using now. A lot friendlier heat race setup too now.

Why the drop in nitro? My tank is too small with 60%. On 50% it's more managable on the start clock. :blink: need bigger tank!

I will say this though - the results do vary from one boat to another, and motors and pipes have an effect also. If you are going to test flywheels - try and keep everything else the same and just try flywheels and props only. Forget radar guns etc. and just see what launches and what doesn't. Craig mentioned also that where you remove the weight from makes a difference too. Diameter should be kept as a constant if possible. A larger diameter can act like a heavier flywheel while maintaining the same weight.

 

[EatMyShortsRacing]

But as far as the flywheel weight needed for launch, I think mostly BS.

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Then try it. I have & yes you can go too far. <_<

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I told you the Klegecell flywheel wouldnt work!!!!

 

[EatMyShortsRacing]

I can believe people still doubt Ceramics!
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I (and I believe most others) are not doubting ceramics as a technology.... I am waiting for the best bearings for our application to be available -probably at a reasonable cost, enough information to be able to make that decision and more information on the best way to maintain those bearings.

 

[shoboat]

Preston,

I believe the same thing about flywheel weight,it is in the crankshaft design

that is critical. You guys should give Rod Geraghty a call sometime and learn

a little more about our engines. It will be some of the best money you will ever

spend in this hobby (2.9 cents a minute). I was going to start another post about

flywheels and launching,but on second thought I think I will just read. :lol:

Good Luck Launching, :lol:

Mark Sholund

 

[Don Ferrette]

I can believe people still doubt Ceramics!
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I (and I believe most others) are not doubting ceramics as a technology.... I am waiting for the best bearings for our application to be available -probably at a reasonable cost, enough information to be able to make that decision and more information on the best way to maintain those bearings.

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Absolutely. No one is doubting the ceramic technology, only what is CURRENTLY available to the majorityof users.

 

[Preston_Hall]

Mark brings up a good point. You guys don't see the big CMB's with some massive flywheel do you?

If no flywheel kills the launch, then why not go back to brass so you can launch anything? Something just ain't add'n up with that line of thought.

It was explained to me one time that the heavy flywheels were used to help maintain engine rpm in the turns back when boats were heavier, less able to turn, and had less power. Now I could agree with that.

By the way, the flywheels on my .12's were only made to be able to hold a belt. I have launched every prop so far. Maybe I will get an extra NR wheel and cut it down to see what happens. Eh, why waist a good flywheel?

I thought about it a little more. If wheel weight was a major consideration then you would see numerous versions. But instead you see the same wheel going over 100mph.

Tim,

To be fair, when you change nitro% then head volumes and pipe lengths change as well.

 

[Joe Warren]

Jeff If you want the EXTRA EDGE........... for heat racing???? Put some NITRO in the Tank of that GAS Boat..... :lol: :lol: :lol: :blink:

 

[Don Ferrette]

Mark brings up a good point. You guys don't see the big CMB's with some massive flywheel do you?

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The big CMB (Evo90's & 100's) flywheels are solid and heavier than you might think. It was on a CMB Evo 90 I experimented with flywheel weight & you can go too far. What I found in lightening flywheels is it comes down to how much blade you're trying to launch. A wicked big block prop will need a bit more rotational mass than a dinky little .12 prop. I've done the testing, not sat around & theorized about it.

 

[TimD]

Preston - your comments are true about the nitro relating to pipe length and head volume and those are things I worked on when I changed the fuel. However most of my testing was on the same fuel, and with the appropriate CR. I mentioned the fuel for 1 reason. A lot of people use nitro as the fix for launching bigger props. As a result of my flywheel tests I don't rely on the nitro any more to pull the fast props from the shore and solved my fuel volume problem as a bonus.

Maybe I wasn't clear on this before - if not I appologize whole heartedly. My MODIFIED flywheel was just too light. I'm certain of it because I can keep everything else the same except for going from the STOCK FLYWHEEL to the lightest modified flywheel and it will not launch the same prop. I hope that clears up any confusion.

Your comment about the CMB flywheel is missing a key point. Measure the weight and outside diameter of the CMB crank AND the flywheel and there is your answer. It's a big, heavy SOB. By comparison a K90 for example - (multiple Naviga 15cc hydro class world champion engine and dominant) has a smaller diameter crank and is lighter, with a bigger, heavier flywheel.

Now FSRV is a different story. CMB's dominate and no K90's to be seen. Why? Power curves are totally different and better suited to the loading those boats put on the engine. The smaller engines in FSRV run gear reduction to boost torque at the prop.

Look into centripetal and centrifugal force, and moment of inertia. It's common physics. Don't think of the crank and flywheel as 2 separate items, they are both contributing to the equation. You have to consider them both together.

 

[EatMyShortsRacing]

Now FSRV is a different story. CMB's dominate and no K90's to be seen. Why?

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K90 would have worn the piston / sleeve out in the first heat!!!!! :lol:

Just kidding!!!!

 

[TimD]

Can we get back on the subject of ceramic bearings and how to take better advantage of them, PLEASE??

 

[Don Ferrette]

Can we get back on the subject of ceramic bearings and how to take better advantage of them, PLEASE??

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Well until we can get our hands on something better than what is available right now to the general boating community we are at a standstill.................. :unsure:

 

[Joe_Knesek]

The stacked crank on a CMB more than makes up for the lack of flywheel. Isn't this similar to using a heavy grain bullet? The mussle velocity of the heavy bullet is less than a light one, but it has more knock down power. Thinking of this, it seems like the heavy flywheel would help keep the boat going once it's up to speed but make it harder to get going when the motor is not turning up.

I'm not an engine guy and most likely way off base on this but it's worth a thought.

 

[EatMyShortsRacing]

The stacked crank on a CMB more than makes up for the lack of flywheel. Isn't this similar to using a heavy grain bullet? The mussle velocity of the heavy bullet is less than a light one, but it has more knock down power. Thinking of this, it seems like the heavy flywheel would help keep the boat going once it's up to speed but make it harder to get going when the motor is not turning up.
I'm not an engine guy and most likely way off base on this but it's worth a thought.

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Sort of.... the flywheel effect is negated to a degree by the out of balance part.

That being said the A90s (especially the earlier ones) have a tiny flywheel in comparison. It seems to have no problems without a big flywheel. (also a stacked crank - may have a lot more mass in the crank system than a CMB)

 

[Preston_Hall]

Thinking of this, it seems like the heavy flywheel would help keep the boat going once it's up to speed but make it harder to get going when the motor is not turning up.

I'm with Joe on this.

What I found in lightening flywheels is it comes down to how much blade you're trying to launch. A wicked big block prop will need a bit more rotational mass than a dinky little .12 prop.

Don,

First, I used the .12 as an example because it is the weakest of motors. Mine has almost no flywheel. So with the hydro doing 78mph it must be pulling a big prop.

Second, when comparing a .90 to a .12 I think the .12 wins. Why? Well, top speed in F Class is 126mph compared to A class at 82mph. Seven times the motor and only 1.5 times the speed.

Third, to reinforce my point and to show that " A wicked big block prop will need a bit more rotational mass" isn't necessarily true, look at KP's F Seaducer. An entirely stock setup. It was a very fast heat racer at 70mph. But using the same weight boat and flywheel it was ablt to pull the wicked big block prop to record speeds. Like I said, nobody is going to heavier flywheels to go faster.

Besides, I never said to through the whell away just that it was mostly BS.

Lastly,

I've done the testing, not sat around & theorized about it. 

Well, I won't even get into your bench racing time. :lol: :lol: :lol: :lol: You left the door wide open on that one buddy!

 

[Preston_Hall]

A lot of people use nitro as the fix for launching bigger props.

Tim,

This is probably where most are going the wrong way. Speed is in a smaller diameter prop with more rpm. Generally speaking that is.

 

[TimD]

A lot of people use nitro as the fix for launching bigger props.

Tim,

This is probably where most are going the wrong way. Speed is in a smaller diameter prop with more rpm. Generally speaking that is.

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I agree.

My 21 rigger props are in the 43 - 44mm diameter range. According to KP - thats too small..... It probably is too small to run 76+ but I don't need to heat race that fast YET. Low 70's is enough

When I mentioned launching bigger props in my case I should have said higher pitched props as a more accurate description! Sorry.

 

[Don Ferrette]

"Third, to reinforce my point and to show that " A wicked big block prop will need a bit more rotational mass" isn't necessarily true, look at KP's F Seaducer. An entirely stock setup. It was a very fast heat racer at 70mph. But using the same weight boat and flywheel it was ablt to pull the wicked big block prop to record speeds. Like I said, nobody is going to heavier flywheels to go faster."

Yup, with the stock heavier flywheel & stock hi mass crank. That's basically the point I was making. I used to run the same Evo 90 motor & with a LIGHTENED flywheel it struggled to handle props it would launch on a stock flywheel, with no other changes whatsoever. Never said a heavy flywheel would make you faster.