lighten your counter blancer?

[woodsracer144]

ok in this review the guy takes some weight off his counter blancer, what would that do??

http://www.atvsource.com/articles/product_reviews/2001/053101_mp_racing_trx250r_page_1.htm

[leager-n-ky]

they would do that so the motor could rev up faster.

[C-LEIGH RACING]

Originally posted by woodsracer144
ok in this review the guy takes some weight off his counter blancer, what would that do??

http://www.atvsource.com/articles/product_reviews/2001/053101_mp_racing_trx250r_page_1.htm


What would it do ;) :D :p make the engine vib & after every race you would need to check the frame for cracks.

Ran a cut one a few seasons, boy that engine would rev quick like a CR bike engine, but I just got tired of welding the frame everytime I turned around, won some races though.
Neil

[Honda 250r 001]

http://macdizzy.com/trxs2.htm

read what macdizzy said about it, i would say its not worth it unless you add weight to the crank or something to offset it.

[86 Quad R]

Originally posted by Honda 250r 001
http://macdizzy.com/trxs2.htm

read what macdizzy said about it, i would say its not worth it unless you add weight to the crank or something to offset it.

aint that kinda sorta redundant?

[Honda 250r 001]

Originally posted by 86 Quad R
aint that kinda sorta redundant?

my point exactly.

[MOVIN32]

most the time you cant keep the bike hooked up if its running good doing this will just make it harder to ride

[speedfreek]

I had mine lightened. i just figured that i wanted everything done and this was just next on the list. Less reciprocating mass means faster revs! Self explanatory.

[rustyATV]

Anyone tried narrowing the counter weights?

I always figured that if you wanted to lighten your counter balancer without developing too much vibration, you'd do so by narrowing the counter weights, rather than turning down their diameters. This would preserve the location of their mass centers, which is what's mainly responsible for their counter balancing effect.

Going further, I also thought it would be possible to lighten the counter balancer gear in such a way that you could not only lose more weight, but gain back some of the counter balancing effect that you gave up narrowing the counter weights

[jcs003]

Originally posted by rustyATV
Anyone tried narrowing the counter weights?

I always figured that if you wanted to lighten your counter balancer without developing too much vibration, you'd do so by narrowing the counter weights, rather than turning down their diameters. This would preserve the location of their mass centers, which is what's mainly responsible for their counter balancing effect.

Going further, I also thought it would be possible to lighten the counter balancer gear in such a way that you could not only lose more weight, but gain back some of the counter balancing effect that you gave up narrowing the counter weights

the opposing forces is what minimizes the harmonic vibrations of the crank assembly. so the masses are canceling each other out. if you change the mass of the balancer it will no longer "balance."

[rustyATV]

Originally posted by jcs003
the opposing forces is what minimizes the harmonic vibrations of the crank assembly.


Yes, but do you know what CAUSES the opposing forces? Mass is only part of it.


[i]so the masses are canceling each other out. if you change the mass of the balancer it will no longer "balance."

Ever wonder why the counter balancers of motors as big as the XR650R are so much smaller than the 250R's?

[jcs003]

Originally posted by rustyATV
Yes, but do you know what CAUSES the opposing forces? Mass is only part of it.

that is what causes the effect(opposing forces). the flywheel and counterbalancer act to make the vibrations = 0.

(crank+piston+rod) - (flywheel+counterbalancer) = 0


Ever wonder why the counter balancers of motors as big as the XR650R are so much smaller than the 250R's?

[rustyATV]

Originally posted by jcs003
that is what causes the effect(opposing forces). the flywheel and counterbalancer act to make the vibrations = 0.

(crank+piston+rod) - (flywheel+counterbalancer) = 0

Hardly what I'm talking about. I'm referring specifically to the counter balancer, ONLY the forces it generates, and how strategically removing mass from other components bolted to it can make up for mass removed from it in a certain manner.

Try this (http://en.wikipedia.org/wiki/Center_of_mass) and this, (http://en.wikipedia.org/wiki/Parallel_axis_theorem) while thinking of only the balance weights and drive gear.

[jcs003]

Originally posted by rustyATV
Hardly what I'm talking about. I'm referring specifically to the counter balancer, ONLY the forces it generates, and how strategically removing mass from other components bolted to it can make up for mass removed from it in a certain manner.

Try this (http://en.wikipedia.org/wiki/Center_of_mass) and this, (http://en.wikipedia.org/wiki/Parallel_axis_theorem) while thinking of only the balance weights and drive gear.

for example: you are refering to the cooresponding gears that
drive the counterbalancer?

thank you. but i am a mechanical engineer. i understand the dynamics of the assembly very well. i could get into some heavier calculations if my laymans equation wasnt clear enough.


you also, being an engineer should understand this.

on another note. you build on youtube is cool.

[rooster300ex]

my 300ex doesn't even have a counter balancer. It did do a number on my old frame because the motor mounts came loose, and i didn't notice.

[rustyATV]

Does anyone have a CRF450 balancer shaft out that they can take pictures of?


Originally posted by jcs003
thank you. but i am a mechanical engineer. i understand the dynamics of the assembly very well.

Good. Take a look at these pictures. On the left is a 400EX balancer shaft, and on the right a 250R's. What can you tell me about the center of mass on the 400EX's two balancer weights compared the the 250R's three? Especially when you keep in mind that the 400EX is a much larger displacement engine. I'm looking for you to tell me two things.

http://img.photobucket.com/albums/v11/hoppy/250R/BalancerArgument010.jpg

http://img.photobucket.com/albums/v11/hoppy/250R/BalancerArgument005.jpg

http://img.photobucket.com/albums/v11/hoppy/250R/BalancerArgument011.jpg

[rustyATV]

Originally posted by jcs003
for example: you are refering to the cooresponding gears that
drive the counterbalancer?

Missed this. Yes, that's where I'm talking about making up for a little bit that's lost.

[woodsracer144]

Who the he'll does that work!!!! Please explain

[rustyATV]

This isn't a fair comparison for a few reasons, but .........

400EX on the Left, 250R on the Right

http://img.photobucket.com/albums/v11/hoppy/250R/BalancerArgument007.jpg

http://img.photobucket.com/albums/v11/hoppy/250R/BalancerArgument009.jpg

[jcs003]

i see what you were meaning now. the proportions on the weights wont change but the other rotating components can be modified to lessen the loads on the counterbalancer weight .

similiar to taking casting lines off a connectiong rod.

[rustyATV]

Originally posted by jcs003
i see what you were meaning now. the proportions on the weights wont change but the other rotating components can be modified to lessen the loads on the counterbalancer weight .

similiar to taking casting lines off a connectiong rod.

Yes! It wouldn't be a huge gain, no more than a few ounces here and there, but it's all rotating mass out of the most detrimental area.

I thought about this when I first looked at a CRF balancer shaft

http://cgi.ebay.com/ebaymotors/HONDA-CRF450R-CRF450X-CRF-450-R-BALANCE-SHAFT-GEAR-NUT_W0QQitemZ140264856404QQcmdZViewItemQQptZMotorc ycles_Parts_Accessories?hash=item20a86fdb54

The gear is obscured from view here, but you can see that Honda took a lot of weight out of one side of the gear to gain a little balancing effect from it. Also, they made the main balancer weight thinner and taller, so it'd have greater effect. Both of these allow for the overall balancer weight to be less.

I theorized that with a little calculation, some weight could be trimmed off the 250R balancer without affecting the vibration. And, taken a step further, possibly some vibration could be taken out of big bore kits by trimming away some of the drive gear. Wouldn't be a lot, though.

[jcs003]

this is one of aspects of my job. i design aftermarket components for road construction mills and recyclers. i use plastics with better wear characteristics and lighter weight than the overweight rubber OEM rollers.

this in turn is beneficial to the municipalities and road construction companies. longer time between maintanance intervals. less overall weight puts less wear on motors. and the type of plastics allow the conveyor belts to last longer.


and in reference to the thread. a trued and balanced crank aids in the overall performance of the crank/counterbalancer relationship.

[bloodswet&gears]

are yall saying lighten the crank so you can lighten the balancer? or balance the crank to eliminate the balancer. got me interested. i know this is not a new concern to these engines and if there were a good way to eliminate it it would be part of everybodys eng. build procedure nowdays. what about lightening the flywheel and balancer the same amount of weight and balancing it all as an assembly? why wouldnt that work?

[C-LEIGH RACING]

Rusty, you ever seen a TRX250R or CR250R crank with the tins removed.

If I'm understanding the balancing of a crank, the fat lobes on the crank are to counter the offset weight of the rod & piston duing the rotation of it all & the addition of the counter balancer is to counter the vibs even more in the 4 wheeler frame.
Neil

[rustyATV]

No, I'm not talking about doing anything to the crank. I'm talking about trimming the counter balancer in certain opposing areas so that it's weight is reduced, but it still has the same effective damping qualities.


Neil:

This is for multi-cylinder engines, but I'd imagine the problem is similar since there isn't another connecting rod opposing the one flying around in a quad/bike engine.

http://en.wikipedia.org/wiki/Balance_shaft


during a given period of crankshaft rotation, the descending and ascending pistons are not always completely opposed in their acceleration, giving rise to a net vertical inertial force twice in each revolution whose intensity increases quadratically with RPM, no matter how closely the components are matched for weight.

[Honda 250r 001]

Im a little confused here, are you saying that if you would run a bigger O.D. counterbalencer, and less weight it would have the same effect?

Or are you saying that if you remove some material from the gear, oppsite from the half moon weight on the counterbalencer, then you could remove some weight from the half moon weight also?

[rustyATV]

Originally posted by Honda 250r 001
Im a little confused here, are you saying that if you would run a bigger O.D. counterbalencer, and less weight it would have the same effect?

Or are you saying that if you remove some material from the gear, oppsite from the half moon weight on the counterbalencer, then you could remove some weight from the half moon weight also?


Actually, I'm saying both.

If you look at the Macdizzy link, the way Rick turned down the counterbalancer (reducing the diameters of the weights) is what's commonly done. I was proposing that, instead, the weights be narrowed. This way the center of gravity of the weights stays in the same place (turning them down moves the CG's closed to the axis of the shaft) and they don't lose their balancing effect as quickly as material is removed. To illustrate, I referenced the XR650R, CRF450, and 400EX balance shafts to show how Honda balanced larger pistons and strokes with physically smaller balance shafts by using narrower but taller weights.

And further, yes, if you remove some material from the non-weighted side of the gear, then a proportional amount (you'll have to figure equivalent masses and centers of gravity) could be removed from one of the weights.

Like I said, I don't think much could be removed, but it might be a better situation than turning the weights down.

[jcs003]

the bottom line is: the benefits would be negligible. unless its in a drag engine where the transfer of power needs to be as fast as possible. a lighter/modified pistion would have the same effect.

but if you have the money to make all these small revisions. the sum of all small parts would possibly be signifigant. but reliability comes into the equation.

[derby]

Originally posted by jcs003
the bottom line is: the benefits would be negligible. unless its in a drag engine where the transfer of power needs to be as fast as possible. a lighter/modified pistion would have the same effect.

but if you have the money to make all these small revisions. the sum of all small parts would possibly be signifigant. but reliability comes into the equation.

As said previously benefit will be small. The only motor I have built that had more vibration than usual is a 78mm bore 77mm stroke pro-x. But smaller motors you do not notice any extra vibration. I am sure it depends on how much you take off and where you remove the wt. from the counter balancer. I would not put a lightened counter balancer in anything larger than a 370. As for reliability it will be fine you will hear the CB bearing when they start to go.