Topic: Ever heard of dynabeads?

[SiliconDoc]

I just did a little more research, as I was considering taking an out of balance tire to a tire balancing shop and doing a test with a before and after to show if it does, indeed, balance tires.

However, this has been preempted by dynabeads claim that they would not work with a static balancer.

Why?
Markcb750, you are a physicist (or something), explain this to me. How can the dynabeads defy the laws of physics while attached to a vehicle, yet not defy this same laws when attached to a balancing machine?

Since Dynabeads effects (or lack thereof) is apparently immeasurable unless in tires attached to a moving bike, I guess what has to happen is a sensor that measures...... what, lessee, travel of the fork, and applied longitudinal force to the forks at the axle. and run the exact same road at the exact same speed and compare data...
Yeah, dun think I'm gonna be able to swing that one.

A static tire balancer in a shop has no forward motion upon spinning, so the beads do not have a static  inertial load in the force direction parallel and opposite with the plane of the road and direction of vehicle movement.

In other words, on the balancer the beads grab the inner wall of the tire in clumps and faster, while on your motorcycle, your tire travelling forward leaves the static interial load of the beads "sitting" in the spot your tire just moved from, to do the balancing work as they "lazy sling" toward the back of the inside of the tire (in effect).

You'd have to mount the balancer on a vehicle and move in the direction of the tire spin up at appropriate speeds equalling the spin up speed, to have a "valid" test.

[mlinder]

The bumblebee thing was stated in the 30's. Physics has long since solved the puzzle.

[mlinder]

I just did a little more research, as I was considering taking an out of balance tire to a tire balancing shop and doing a test with a before and after to show if it does, indeed, balance tires.

However, this has been preempted by dynabeads claim that they would not work with a static balancer.

Why?
Markcb750, you are a physicist (or something), explain this to me. How can the dynabeads defy the laws of physics while attached to a vehicle, yet not defy this same laws when attached to a balancing machine?

Since Dynabeads effects (or lack thereof) is apparently immeasurable unless in tires attached to a moving bike, I guess what has to happen is a sensor that measures...... what, lessee, travel of the fork, and applied longitudinal force to the forks at the axle. and run the exact same road at the exact same speed and compare data...
Yeah, dun think I'm gonna be able to swing that one.

A static tire balancer in a shop has no forward motion upon spinning, so the beads do not have a static  interial load in the force direction parallel and opposite with the plane of the road and direction of vehicle movement.

In other words, on the balancer the beads grab the inner wall of the tire in clumps and faster, while on your motorcycle, your tire travelling forward leaves the static interial load of the beads "sitting" in the spot your tire just moved from, to do the balancing work as they "lazy sling" toward the back of the inside of the tire (in effect).

You'd have to mount the balancer on a vehicle and move in the direction of the tire spin up at appropriate speeds equalling the spin up speed, to have a "valid" test.

I thought about this.
Doesn't quite make sense unless you are accelerating or decelerating at a constant rate.
This is the same reason you feel pushed back in your seat accelerating to 60 mph, but feel nothing once you reach 60mph and maintain that speed.
There is no "interial load in the force direction parallel and opposite with the plane of the road and direction of vehicle movement" once you reach and maintain any given speed inside the tire.

[BVCB650]

OK. I've forwarded this to NASA. They'll get back to me soon.

[Markcb750]

mlinder

correctamondo...

[SiliconDoc]

Right, your butt is attached to the bike and your travelling along the in the same direction it is.
Your tires, however are spinning, and anything inside them light enough to "stick" to the inner circumference is spinning along with them, travelling forward in an up and down WAVEFORM, instead of straight ahead in a line as you are...

 The beads inside the tire rest on the bottom, the tire moves forward as you take off, the beads DO NOT, until they hit the friction of the back inner wall of the tire that just moved forward and smacked them. The back of your seat, for instance does the same thing, put armor all on it real slick, then hit the gas hard with a curb ten feet in front of you.

 Your butt bead will slide backwards on the seat, while the seat travels forward (like the tire and beads) - then your butt will hit the curve of the back of the seat as it comes forward (like the beads getting hit by the moving forward wall of the back of the inside of the tire. Then when your bike hits the curb, the back of the seat rises upward and moves forward, like the back of the spinning tire, and you are caught in a looping forward motion, just like the beads....
 
Things change from there for you and the beads, unless you manage to loop your bike end over end a few times.  


So, the point is the beads remain at rest like your butt on a slick seat that moves forward when you hit the gas.


In a static balancer in a shop, it would be like spinning your bike 360 when you're sitting in it. You would have much less tencency to slip toward the back of the seat before being hooked into the roll over. In fact, the gas tank would wail you in the crotch as the spinning began.

[mlinder]

This is my last post on this subject. I doubt most people could feel a slightly out of balance wheel as they never ride hard enough to notice it any way. I have only ever once felt an out of balance wheel out of the 20 odd bikes i have owned the last 20 years and it wasn't a balance problem it was the spokes needed adjusting. All my bikes have needed balancing when the rims have been put on a balancer but there was no discernible wobble in the first place. Having worked in bike shops and seen hundreds of wheels balanced i bet if you took a freshly balanced wheel to another shop it would still be slightly out of balance. Have fun with your little balls....

Mick

I, personally, have a natural tendency to study and evaluate claims and issues, with as much knowledge as I have, or can find.
I also prefer to follow practiced, scientific methods to prove or disprove a claim or theory. Anecdotal evidence and bad math are not acceptable to me, nor are unscientific methods of data gathering.

We aren't 'afraid' to use them, 1974CB, we just refuse to be suckered in to buying something that we, personally, can't see working.

Me 'trying' them is an unscientific method, as I know that a.) I am incapable of measuring minimal (or nonexistent) changes in a complex system while being able to ascribe said changes to a single element of a complex system with multiple elements and b.) I am already predisposed to believing they do not work, which could color my perception, and therefore report, of the item in question.
Also, any claim I made would also be anecdotal, which is unacceptable. Without the use of a calibrated measuring system, that gives me quantifiable, repeatable results, I cannot make a claim as to it working in good conscience.

So, you are saying that there is no way to tell if they are working by riding the bike because the change would be so small? Yet, you pay someone to put weights on the tires even though there is no way, according to you, that you would ever know the difference? 

No, I'm saying I pay someone to put them on when they are needed. I also pay them to take them off when they aren't.
My statement was that no one here has taken a wheel, with weights, had it checked on a balancer, removed the weights, had it checked again on a balancer, then added dynabeads, and again had it checked on a balancer.
This is the only way to really effectively check what has changed between each iteration of the experiment.

OK, here we go. Please understand this is not a personal attack, this is merely a statement on how arguments are made.

Get outta here with your humble opinion, Achmed.
You have a goat for an avatar, goats don't understand physics, therefore, you do not understand when other people understand (or don't understand) physics.
We clear?

Looked like a personal attack to me...

If you really see that as a personal attack, I don't know what to say, Mickey. Perhaps if you reread the entire thread, you'd see that Achmed and I poke fun at each other through the entire thing off and on, and we both know it's just that, fun.

I don't know that they don't work. I theorise that they don't work, based on physics that I know.
Again, I could be missing something very important in this equation. I've said it many times.

"Tire balance, also referred to as tire unbalance or imbalance, describes the distribution of mass within an automobile tire and/or the wheel to which it is attached. When the tire rotates, asymmetries of mass cause the wheel to wobble. This wobbling can give rise to ride disturbances, usually vertical and lateral vibrations. The ride disturbance due to unbalance usually increases with speed. Vehicle suspensions can be excited by tire unbalance forces when the speed of the wheel reaches a point that its rotating frequency equals the suspension’s resonant frequency."

I know, it's wikipedia so I'm pushing it when it comes to actual fact here by posting that but, in this case it's true.

Yes, I know what tire imbalances are.

Also, my back tire was balanced at the shop. I felt no difference between it and the front one with dyna beads except that I can tell it takes about 10-15mph for the beads to settle. Yup, I can feel it. I'm willing to buy more beads, take off the back weights, ride without, see what that does and then put in some beads. I'm curious and $7 is a small price to pay compared to $50 at the shop. It think the weights are highway robbery for something that, according to our "experts", can't possibly be felt or make a difference anyway.

I've never told anyone not to buy them, I've only stated my own conclusions about their validity. I've also stated that I could be very wrong, by leaving out an important fact of physics.

"The only true wisdom is in knowing you know nothing." -
   Socrates

That applies to everyone

(man, this quoting jungle has me confused)

[SiliconDoc]

Once the tire is up to speed, the beads have distributed and are temporarily stuck to inner circumference wall of the tire - when the tire hits a bump(bulge), the inner wall squishes at the road bump and throws a few beads stuck to it off - as the rim and tire move upward travelling over the bump, a similar intertial effect occurs - the beads, not being attached to the tire, do not move upward on the top inner half of the tire, only on the bottom half, and more so the closer to bottom dead center they are.
 So at that point you have "floating beads" to a degree in the top half, and beads slung upwards in the bottom half along with the tire, and a few "shooting" off the spot inside where the tire tread hit the bulge.
 The tire moves forward, spinning and back down, and the beads are "recaught", generally further to the rear half of the tire as it's forward motion is maintained by your bike and the front fork bearing -
 So there is quite a lot going on inside that tire, since it has direction travel and rotational travel - that has to be kept in mind, as well as the fact that the beads are not permanently attached to the inside of the tire, and only achieve a "spot stick" temporarily, whilst they travel not only forward but up and down as well.

[mlinder]

Right, your butt is attached to the bike and your travelling along the in the same direction it is.
Your tires, however are spinning, and anything inside them light enough to "stick" to the inner circumference is spinning along with them, travelling forward in an up and down WAVEFORM, instead of straight ahead in a line as you are...

 The beads inside the tire rest on the bottom, the tire moves forward as you take off, the beads DO NOT, until they hit the friction of the back inner wall of the tire that just moved forward and smacked them. The back of your seat, for instance does the same thing, but put armor all on it real slick, then hit the gas hard with a curb ten feet in front of you.
 Your butt bead will slide backwards on the seat, while the seat travels forward (like the tire and beads) - then your butt will hit the curve of the back of the seat as it comes forward (like the beads getting hit by the moving forward wall of the back of the inside of the tire. Then when your bike hits the curb, the back of the seat rises upward and moves forward, like the back of the spinning tire, and you are caught in a looping forward motion, just like the beads....
 
Things change from there for you and the beads, unless you manage to loop your bike end over end a few times.  


So, the point is the beads remain at rest like your butt on a slick seat that moves forward when you hit the gas.


In a static balancer in a shop, it would be like spinning your bike 360 when you're sitting in it. You would have much less tencency to slip toward the back of the seat before being hooked into the roll over.

You are ignoring both centrifugal and centripetal forces here, which are the only two that really matter once the tire is up to speed.

[bistromath]

I can't believe this went on for nine pages.

The problem with the armchair physics analysis in this article is that the posters invariably assume the beads' motion to be circular and subject only to centripetal force. It isn't. It's elliptical in an unbalanced wheel. This eccentricity provides the restoring force moving the beads into a static position, which in turn balances the wheel. It was mentioned earlier that the beads should "clump" together in a wheel rotating in a circle, or more accurately, that there is no force acting on the beads other than centripetal force: lateral force would be necessary to break up the beads from their "resting" state on the bottom of the wheel. This is correct. But when the wheel is rotating eccentrically (i.e., unbalanced, with the shocks taking up the acceleration), with a periodicity equal to the rotational rate, there is an additional force acting on each individual bead which can be modeled as a change in acceleration over the period of rotation. This restoring force is what distributes the beads in a balancing manner. The restoring force is proportional to the eccentricity of the wheel's rotation. This is why balancing on a static wheel balancer won't work: without displacement due to shock travel, the restoring force is very low, and the beads may not have enough force to overcome friction inside the wheel and migrate to a balancing location.

I can do the math if you like, but that's the gist of it.

SiliconDoc, the problem with your analysis is that at a steady speed, there is no rotational acceleration, which would be necessary to cause the beads to move rotationally with respect to the tire's inside surface, and therefore redistribute accordingly when the tire compresses from a bump. The beads will simply move up and down along with the tire's surface, "stuck" to the tire surface by centripetal force.

And mlinder, centripetal force IS centrifugal force, at least by the way I believe you mean the term.

[SiliconDoc]

Right, your butt is attached to the bike and your travelling along the in the same direction it is.
Your tires, however are spinning, and anything inside them light enough to "stick" to the inner circumference is spinning along with them, travelling forward in an up and down WAVEFORM, instead of straight ahead in a line as you are...

 The beads inside the tire rest on the bottom, the tire moves forward as you take off, the beads DO NOT, until they hit the friction of the back inner wall of the tire that just moved forward and smacked them. The back of your seat, for instance does the same thing, but put armor all on it real slick, then hit the gas hard with a curb ten feet in front of you.
 Your butt bead will slide backwards on the seat, while the seat travels forward (like the tire and beads) - then your butt will hit the curve of the back of the seat as it comes forward (like the beads getting hit by the moving forward wall of the back of the inside of the tire. Then when your bike hits the curb, the back of the seat rises upward and moves forward, like the back of the spinning tire, and you are caught in a looping forward motion, just like the beads....
 
Things change from there for you and the beads, unless you manage to loop your bike end over end a few times.  


So, the point is the beads remain at rest like your butt on a slick seat that moves forward when you hit the gas.


In a static balancer in a shop, it would be like spinning your bike 360 when you're sitting in it. You would have much less tencency to slip toward the back of the seat before being hooked into the roll over.

You are ignoring both centrifugal and centripetal forces here, which are the only two that really matter once the tire is up to speed.

Not quite, the acelleration and decelleration of the vehicle and it's tire dynamically changes the "sticking" forces of the beads against the inner tire wall. No one keeps a constant speed on their ride, even grade changes affect this.
 
What you say is much truer when it comes to the rims, for instance, but for the beads, they are able to move around  relative to the inner point on the tire wall, even "at speed".

If you're talking about a perfectly round tire inner, and an absolutely constant speed of rotation, on a perfectly level surface, in a straight line only, well ok, then. That is not what is occurring though, not at all.

[Gordon]

So from what I can see, none of the people claiming that these beads work have any real basis to make this claim because they either tried them on rims with brand new tires that they had never ridden on before, or they made some other change at the same time as installing the beads, so there is no way to tell if they actually made any difference, or if the difference that was felt was caused by the beads or the other change that was made.  

I don't have any stake in either side of this discussion, but this kind of reasoning is the same as if I gave my bike a full tune-up and then put in some Marvel Mystery Oil, and claimed that the reason the bike is running better is because of the MMO.  You have to make just ONE change at a time if you want to have any reasonable expectation of knowing which change had what effect.  

[BVCB650]

So from what I can see, none of the people claiming that these beads work have any real basis to make this claim because they either tried them on rims with brand new tires that they had never ridden on before, or they made some other change at the same time as installing the beads, so there is no way to tell if they actually made any difference, or if the difference that was felt was caused by the beads or the other change that was made.  

I don't have any stake in either side of this discussion, but this kind of reasoning is the same as if I gave my bike a full tune-up and then put in some Marvel Mystery Oil, and claimed that the reason the bike is running better is because of the MMO.  You have to make just ONE change at a time if you want to have any reasonable expectation of knowing which change had what effect.  

I didn't run my new tires before the beads, but the guy at the shop said they were out of balance when I picked up the mounted pair. Maybe he was just trying to sell me a balance job.

[mlinder]

Once the tire is up to speed, the beads have distributed and are temporarily stuck to inner circumference wall of the tire - when the tire hits a bump(bulge), the inner wall squishes at the road bump and throws a few beads stuck to it off - as the rim and tire move upward travelling over the bump, a similar intertial effect occurs - the beads, not being attached to the tire, do not move upward on the top inner half of the tire, only on the bottom half, and more so the closer to bottom dead center they are.
 So at that point you have "floating beads" to a degree in the top half, and beads slung upwards in the bottom half along with the tire, and a few "shooting" off the spot inside where the tire tread hit the bulge.
 The tire moves forward, spinning and back down, and the beads are "recaught", generally further to the rear half of the tire as it's forward motion is maintained by your bike and the front fork bearing -
 So there is quite a lot going on inside that tire, since it has direction travel and rotational travel - that has to be kept in mind, as well as the fact that the beads are not permanently attached to the inside of the tire, and only achieve a "spot stick" temporarily, whilst they travel not only forward but up and down as well.

This is implying that the inertial force caused by the slight upward movement is somehow greater than the inertial force caused by centrifugal force.

I don't have the formulas for calculating these in front of me. But I'll bet Markcb750 knows em.

[Gordon]

I didn't run my new tires before the beads, but the guy at the shop said they were out of balance when I picked up the mounted pair. Maybe he was just trying to sell me a balance job.

Either that or they're still out of balance, but just not enough for you to notice. 

[mlinder]

And mlinder, centripetal force IS centrifugal force, at least by the way I believe you mean the term.

Nope, I'm talking about the force that causes the beads to head towards the point furthest away available form the axis, and the force that causes them to not travel in a straight line (in this case, the wall of the tire itself, and it's imperfections.)

I am going to re-read the rest of your post a few times before I comment. As I said (again) it's possible I didn't factor in something, and this may be it.

[bistromath]

This is implying that the inertial force caused by the slight upward movement is somehow greater than the inertial force caused by centrifugal and centripetal forces.

I don't know what you mean by "inertial force" in this context. But the forces acting rotationally on beads inside the tire are zero when the tire is in balance, meaning the beads will not migrate after the tire is in balance. They are only nonzero for a tire which is out of balance (and in this I use "tire" to mean "tire and beads system"), and this is when they move inside the tire toward a position of balance. There is no "inertial" force acting rotationally on the beads that is keeps them from moving freely about the inside of the tire, EXCEPT the restoring force caused by the eccentricity of the wheel's motion.

Nope, I'm talking about the force that causes the beads to head towards the point furthest away available form the axis, and the force that causes them to not travel in a straight line (in this case, the wall of the tire itself, and it's imperfections.)

I don't mean to be condescending, but you're really close: there isn't one axis of rotation in this system. The axis is a line, since it's an ellipse, a line in the direction of the shocks' travel. Factoring that in should clear everything up.

[SiliconDoc]

SiliconDoc, the problem with your analysis is that at a steady speed, there is no rotational acceleration, which would be necessary to cause the beads to move rotationally with respect to the tire's inside surface, and therefore redistribute accordingly when the tire compresses from a bump. The beads will simply move up and down along with the tire's surface, "stuck" to the tire surface by centripetal force.

Quite incorrect you are. A bump in the road does in fact induce a reduction in speed, and in fact in rotational velocity of the wheel and tire. Furthermore, the direction of bead travel, for instance, just forward of TDC inner tire, is forward and DOWNWARD - when the tire hits the bump and moves UPWARD and forward, those beads release from the inner wall.
 There are other spots that dynamically release in the movement, including in a dip or pothole.
 There are also sideways forces in turning and the biker just simply balancing the vehicle induces movement out of sync with the inner wall "at constant speed" which is a rare continuing condition over ride time.

 We aren't talking about a static system, either, where the forces are looked at in just one point in time. If that were the case, nothing would be moving.

 One has to realize that unless the rotational velocity of the tire is fast enough (that speed can be measured) to negate the effects of other disruptive movement (faster, slower, bumps) and keep the beads all stuck exactly where they are, that just doesn't happen.
 Don't get me started on ANY LATERAL movement of the tire side to side, because that is ALWAYS going to move the beads. (except in very rare localized areas that combine with the turning/ tipping the bike.

 Keep in mind gravity as well. That changes the dynamics of beads moving upward in the rear half of the tire vs downward in the front half. I'm not in weightless space here.  (which is generally how centrifugal forces are taught or thought of by people)

[BVCB650]

I didn't run my new tires before the beads, but the guy at the shop said they were out of balance when I picked up the mounted pair. Maybe he was just trying to sell me a balance job.

Either that or they're still out of balance, but just not enough for you to notice. 

Could be. If they are, they still run smooth at 70-75 mph. I guess the beads aren't making them out of round.

[bistromath]

Mlinder, just noticed that I replied to your reply to SiliconDoc. Thought you were making a point toward me.

SiliconDoc, I believe I understand what you're saying, but the small changes in rotational velocity of the system won't significantly overcome static friction and imperfections of the inner tube. And more significantly, the beads do not rotate with respect to the inner tube, other than to distribute themselves to a balanced state. They won't roll like "spinner" hubcaps inside the inner tube. Frictional losses will account for that motion very quickly.

[CBGhia]

So from what I can see, none of the people claiming that these beads work have any real basis to make this claim because they either tried them on rims with brand new tires that they had never ridden on before, or they made some other change at the same time as installing the beads, so there is no way to tell if they actually made any difference, or if the difference that was felt was caused by the beads or the other change that was made.  
 

Thats not quite true.  I did a test where I rode my bike before adding the beads.  i have had my wheels trued, but never had the tires balanced.  I was having a problem with headshake if I removed both hands from the bars, and sometimes if I removed even one hand. 
I added Dynabeads and went down the same road within 10 minutes of my last ride.  The only change was dynabeads.
My headshake was pretty much gone.  I still feel it a little bit on occasion, but I can take both hands off of the bars when cruising and do not have a problem now.   It honestly made a difference for me. 

Further more,  I did it one tire at a time and the front tire was done first.  It had the larger impact in handling.

[mlinder]

This is implying that the inertial force caused by the slight upward movement is somehow greater than the inertial force caused by centrifugal and centripetal forces.

I don't know what you mean by "inertial force" in this context. But the forces acting rotationally on beads inside the tire are zero when the tire is in balance, meaning the beads will not migrate after the tire is in balance. They are only nonzero for a tire which is out of balance (and in this I use "tire" to mean "tire and beads system"), and this is when they move inside the tire toward a position of balance. There is no "inertial" force acting rotationally on the beads that is keeps them from moving freely about the inside of the tire, EXCEPT the restoring force caused by the eccentricity of the wheel's motion.

Yeah, I'm sorry, inertial force was not correct. I'm not sure what to call it, because the direction of the travel of the axis is inertial (it's in a  straight line), the direction the forks travel, but the beads are are not at the axis, and not stationary, but traveling in an ellipse around that axis. So I guess it's a compound force, and is variable depending on where the beads are in relation to the axis when the forks are pushed 'up' and 'down' , causing inertial force in those directions.

Nope, I'm talking about the force that causes the beads to head towards the point furthest away available form the axis, and the force that causes them to not travel in a straight line (in this case, the wall of the tire itself, and it's imperfections.)

I don't mean to be condescending, but you're really close: there isn't one axis of rotation in this system. The axis is a line, since it's an ellipse, a line in the direction of the shocks' travel. Factoring that in should clear everything up.

'kay..

[Gordon]

What about the valve stem?  Won't a lot of the beads just find their way into it and stay there until the tire stops rotating?  

[BVCB650]

Probably not many because of the valve core taking up the slack. They do say to blast some air in there to free up and stragglers before you take an air pressure reading.

[mlinder]

Bistro,

Read through your statement a couple more times.

I realise that I had considered the same thing when this thread was first posted, though not as succinctly as you wrote it above.
I dismissed it for a couple reasons, one being the variables of competing forces for putting the beads where they are 'supposed' to go, the variables being cause by, for the most part, speed; and because, though I haven't done the math (I suck at math, I have someone do it for me), it seems to me that if the beads moved as soon as balance was needed, then moved again as it wasn't, they'd spend quite a bit of time in 'air', negating the effect they may have. Need to think about that one some more, though. Had another reason, too, but can't remember what it was, yet.