Counter Rotating Brakes Vid

[Dezmo]

Originally Posted by millemille

Counterbalanced engines viabrate because they operate over a wide rpm range.

There will be an rpm, and multiples thereof, where viabrations do not exist. This is due to the primary balance factor used in the balance calculations - an engine can only be balanced for a set rpm, or multiples thereof (unless an engine, such as ducati 90 degree v twin, has perfect primary balance). Engine manufacturers decide during the R+D process where they believe the engine will spend the majority of time within the rpm range - the primary balance factor will then be derived to balance the engine at some point within the chosen band.

Anyone who believes otherwise is welcome to throw their hat into the ring on how to fit lighter pistons and conrods to a rotax V60 engine and retain primary balance via the two balancer shafts.....

not to hijack a thread here but, what does RPM matter when the balancer is spinning at the same speed?

and why do you think they use the term primary balance? Simpe, because there are secondary forces, and when you throw in a counterbalancer, it adds in its own secondary forces.....despite of what RPM youre at, no engine will ever be 100% vibration free.

Balancer isnt a good name, since they dont really balance anything, just get the vibes down to a tolerable level.

And putting lighter conrods/pistons in your aprilia should be easy, provided you know the math to figure out how much mass to reduce the counterbalancers by....reminds me of an old harley trick, guys would get an 883 sportster, bore out the cyls and put wiseco 1200 pistons in them, and it actually improved the balance because wiseco 1200 pistons are slightly lighter than stock HD 883 slugs.

[Mashuri]

Originally Posted by Dezmo

not to hijack a thread here but, what does RPM matter when the balancer is spinning at the same speed?

and why do you think they use the term primary balance? Simpe, because there are secondary forces, and when you throw in a counterbalancer, it adds in its own secondary forces.....despite of what RPM youre at, no engine will ever be 100% vibration free.

Balancer isnt a good name, since they dont really balance anything, just get the vibes down to a tolerable level.

And putting lighter conrods/pistons in your aprilia should be easy, provided you know the math to figure out how much mass to reduce the counterbalancers by....reminds me of an old harley trick, guys would get an 883 sportster, bore out the cyls and put wiseco 1200 pistons in them, and it actually improved the balance because wiseco 1200 pistons are slightly lighter than stock HD 883 slugs.

And what have we learned from all this?
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From now on, every motorcycle should have an inline six.

[roadkill]

Originally Posted by Mashuri

And what have we learned from all this?
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From now on, every motorcycle should have an inline six.

I thought that the moral of the story was that every motorcycle be a V-twin.

[hank]

Originally Posted by roadkill

I thought that the moral of the story was that every motorcycle be a V-twin.

A 90-degree V-twin?

[PSk]

Originally Posted by banda

And you're right again. leaning doesn't produce a turn. It produces a turning force. A force which can be counteracted or enhanced by other forces.

Every movement (or acceleration to be more technically correct) is based on a force imbalance.

Thus the wind was pushing you one way ... you were counter steering your bike the other way to balance the force. Take the wind away and you would have turned ... thus the bike WAS trying to.


I think way to much is made of counter steering as being some mystery, even on this counter rotating brakes site (and has made me very sceptical, considering he stated that he spent a year studying the effect and wrote a paper ... ).


My view on what happens when we counter steer:

If you think about the only 2 constants on the bike related to the road, they are the 2 tyre contact patches. When you push one side of the handle bar, the front tyre turns, it does/can not slide across the road because of grip. Now because of rake when the front tyre turns something else has to move ... and that is ofcourse the head stock (or handle bar pivot, if I have not used the correct term).

Thus we have a lever situation, and thus on my bike atleast, the force of my push is magnified to a larger force that pushes the bike's head stock towards the centre of the turn, hence leaning the bike so positively.


Try it when you are stationary and you can feel the force pushing the head stock sideways or inwards.


This is (one of the reasons, or the only reason?) why rake is so important to bikes. It gives the rider the ability to balance the bike by using force on the handle bars. Witness bicycle riders who balance when stationary ... they move the handle bars around a lot, thus pushing the head stock of the bike left or right to balance.

Its nothing magical ... no gyroscopics involved, plain force balancing. The gyroscopic affects caused by wheels or the motor simply dictates how much force is required to lean the bike.

Pete

[Mashuri]

Originally Posted by roadkill

I thought that the moral of the story was that every motorcycle be a V-twin.

Nothing's more inherently balanced than a 60 degree inline six (or multiples thereof).

[PSk]

Originally Posted by Mashuri

Nothing's more inherently balanced than a 60 degree inline six (or multiples thereof).

Er, an inline 6 has no (included) angle and yes they are very balanced because each pair of cylinders are spaced 120 degrees apart on the crank.

Thus the perfect V angle for a v6 is actually 120 degrees, and 60 degrees for a v12.

I'll have to think about the 60 degree v6 ... some more.
Pete

[roadkill]

Originally Posted by PSk

If you think about the only 2 constants on the bike related to the road, they are the 2 tyre contact patches. When you push one side of the handle bar, the front tyre turns, it does/can not slide across the road because of grip. Now because of rake when the front tyre turns something else has to move ... and that is ofcourse the head stock (or handle bar pivot, if I have not used the correct term).

Thus we have a lever situation, and thus on my bike atleast, the force of my push is magnified to a larger force that pushes the bike's head stock towards the centre of the turn, hence leaning the bike so positively.


Try it when you are stationary and you can feel the force pushing the head stock sideways or inwards.


This is (one of the reasons, or the only reason?) why rake is so important to bikes. It gives the rider the ability to balance the bike by using force on the handle bars. Witness bicycle riders who balance when stationary ... they move the handle bars around a lot, thus pushing the head stock of the bike left or right to balance.

Its nothing magical ... no gyroscopics involved, plain force balancing. The gyroscopic affects caused by wheels or the motor simply dictates how much force is required to lean the bike.

Pete

Please correct me if I am wrong...but reading this made me think of a wheelbarrow....think of how you change direction with a loaded wheelbarrow....very little is required to get it to move off a straight line, just raise one handle a tiny bit.....same with rake....if the distance from the handle is short, it takes more effort to acheive the same amount of turn, conversely, if the handle is looooong, it takes a tiny amount of effort to inititiate the turn....the classic and basics of levers and leverage...same thing on a motorcycle, ne pas? Although, I wonder about the Easyrider bikes with the front wheel in another area code...how do they turn?

That is why rake and trail are so critical. Also, makes you appreciate unicyclists more, eh?

[PSk]

Originally Posted by roadkill

Please correct me if I am wrong...but reading this made me think of a wheelbarrow....think of how you change direction with a loaded wheelbarrow....very little is required to get it to move off a straight line, just raise one handle a tiny bit.....same with rake....if the distance from the handle is short, it takes more effort to acheive the same amount of turn, conversely, if the handle is looooong, it takes a tiny amount of effort to inititiate the turn....the classic and basics of levers and leverage...same thing on a motorcycle, ne pas? Although, I wonder about the Easyrider bikes with the front wheel in another area code...how do they turn?

That is why rake and trail are so critical.

Agree. As my bike is only a GN250 with flat bars I assume it has longer bars than most sports bikes thus my counter steering effort is lower.

I need to read more about rake and trail ... this is the magical area of bikes, me thinks. After all there is not many other variables (other than say swing arm length).
Pete

[hullspeed]

Originally Posted by banda

Kevin Cameron, brilliant as he is, is just wrong about this.

The Wright brothers (bicycle makers before anything else) were the first to describe the physics of single track vehicles and how countersteering makes bikes turn.

What happens when you yank the wheel of your SUV to the left while driving? The body rolls in the opposite direction, to the right. That's just disconcerting in an SUV, but on a motorcycle, the effect is to roll the bike onto a coned part of the tire... that's how the corner is initiated.

Gyroscopes got nothing to do with it. To prove it, motorcycles have been constructed with counter rotating sub wheels to cancel out or even override the gyro effect. Guess what. They still turn just like a regular motorcycle.

Gyro shmyro. Even Kevin Cameron can make a mistake.

no way in hell you're smarter than kevin cameron

[AZ Scott]

Can someone please find us a link to this supposed Kevin Cameron article?

I'd like to know for myself if he's really incorrect on this matter, or if you guys have seriously miscomprehended what he was actually talking about.

I have a great deal of respect for Cameron, and I have a hard time believing that he thinks motorcycles steer because of gyroscopic effect...

[PSk]

Originally Posted by banda

What happens when you yank the wheel of your SUV to the left while driving? The body rolls in the opposite direction, to the right. That's just disconcerting in an SUV, but on a motorcycle, the effect is to roll the bike onto a coned part of the tire... that's how the corner is initiated.

Gyroscopes got nothing to do with it. To prove it, motorcycles have been constructed with counter rotating sub wheels to cancel out or even override the gyro effect. Guess what. They still turn just like a regular motorcycle.

I agree regarding gyroscopics only affecting how hard it is to turn a bike, not how a turn is initiated (I think Dezmo must have misquoted/remembered what this Kevin Cameron guy said, or yet another expert is not always right ) ... BUT I do not agree that a bike's corner is initiated by the type rolling on to the coned part of the tire.

A bike's turn is initiated by either:
1 - Handle bars turned IN to the corner for low speed steering, or
2 - Weight on the inside of the bike causing the bike to want to fall that way for higher speed cornering (counter steering does this by producing a inwards force on the head stock of the bike).

Pete

[Mashuri]

Originally Posted by PSk

Er, an inline 6 has no (included) angle and yes they are very balanced because each pair of cylinders are spaced 120 degrees apart on the crank.

Thus the perfect V angle for a v6 is actually 120 degrees, and 60 degrees for a v12.

I'll have to think about the 60 degree v6 ... some more.
Pete

You misunderstood. I meant a 60 degree crank.

[millemille]

If the issue of balancing a v60 Rotax engine after changing piston and/or rod weight was easy it would have been done many times succesfully - do you know how many times it has done, other than by the aprilia factory, succesfully? (quantify succesfully - retaining same levels of viabration and reliability as oem)Simple answer - never. Only aprilia/rotax know the pbf needed for calculations to remove weight from the crank and/or the balancer shafts. No one, other than aprilia/rotax, actually knows definitively what the two balancer shafts in the V60 engine actually do in relation to the dynamic forces of the reciprocating components of the crank assembly- the primary balance shaft every one is pretty much agreed balances primary forces generated by the crank components - though whether material needs removing from this or the crank to reatin oem primary balance after fitment of lighter compoentns is unknown, and as for the secondary balance shaft in the rear cylinder... does this balance the rear cylinder assembly, come into efect at higher rpm to balance the crank components or is it even there to balance forces created by the primary balancer? This subject is a great debate on numerous threads on Aprilia websites - people such as jet turbine engineers, formula 1 engine tuners, mechanical engineers (such as myself) and intuitively clever back yard tinkerers are all coming at this from different angles ('scuse the pun) with no solid conclusions or solutions.

Balancers only work for certain rpms and multiples thereof because the dynamic forces generated by the crank components vary with rpm - the higher the rpm the greater the force, don't even begin to factor harmonics. The mass of the balancer shafts is fixed therefore the effect of the balancer shaft is fixed. If you were building a racing only engine you would have the balancer shaft mass set to nullify the crank forces at a higher rpm than a road engine.

[Dezmo]

OK, I have put some thought into this, and theres one major flaw with thinking the bike 'falls' into the corner without the influence of gyros, and its the one force that cannot be cancelled out while on earth.....gravity.

Watch a GP or Superbike race sometime, and pay close attention to a particulary tight corner.....see how fast those guys slam the bikes over? Gravity alone cannot do this....if you need proof go hold your bike upright, then tip it just off center and let go....it will fall but it takes a second or so for any speed to build up. (You dont really have to do this, just using an example). If gravity isnt moving the bike over that fast, what is?

secondly, a spinning wheel is a gyro, and it will have a gyro effect whether you want it to or not. The laws of physics state this, and your front wheel is a gyro, you cannot deny any of this. I honestly wish I had the Cameron article handy (the web is horribly understocked with his material), as he explains it in ways anybody can understand.

And Mille, youre right about the balancer mass being constant, but so is the crank mass, and they spin at 1:1....your theory here is flawed, sorry.

And if Aprilia wont tell anyone their balancer formulas, maybe they know something they dont want you to know.

at any rate, any decent mech engineer (banda?) should be able to figure it out. Its just math, albiet very complicated math.

[wildchilds74]

Dezmo

try that little trick with your bike, and pull the bottom of the bike in the oppisite direction. I am no engineer, or anything even close. But if you pull the bottom out from under something that is balancing on a center point (or something like that) it will fall faster. When they flick the bike from one side to the other they are steering away from the corner, and moving their weight to the inside. This would not be the same as something you just let go of and watch how slowly it fell over.

Now, does anybody remember what it is they are trying to talk about here?
I don't understand (not very educated in this area) why the reverse spinning brakes would be good or bad.
I understand that lighter wheels make a bike handle better, because they are easier to move around, and they don't take as much effort to move.

scott

[millemille]

Dezmo

Please read and digest the following thread from an Aprilia forum, all 196 posts...
http://www.apriliaforum.com/forums/s...ad.php?t=73644

Or this one - only 76 posts I'm afraid
http://www.apriliaforum.com/forums/s...ad.php?t=44020

http://www.apriliaforum.com/forums/s...ad.php?t=77868


http://www.apriliaforum.com/forums/s...ad.php?t=72919

[Dezmo]

Originally Posted by wildchilds74

Dezmo

try that little trick with your bike, and pull the bottom of the bike in the oppisite direction. I am no engineer, or anything even close. But if you pull the bottom out from under something that is balancing on a center point (or something like that) it will fall faster. When they flick the bike from one side to the other they are steering away from the corner, and moving their weight to the inside. This would not be the same as something you just let go of and watch how slowly it fell over.

Now, does anybody remember what it is they are trying to talk about here?
I don't understand (not very educated in this area) why the reverse spinning brakes would be good or bad.
I understand that lighter wheels make a bike handle better, because they are easier to move around, and they don't take as much effort to move.

scott

Scott, you have the right idea, as the wheel is pulled the other way as the bike leans, but its being pulled by.....gyroscopic precession (gasp)

I really dont see how difficult this is to understand, it should be clear to anybody with a basic grasp of HS physics.

Now, do I think gravity does nothing to a turning bike? of course not, it helps...theres no denying that, but the predominant force making the bike lean is gyroscopic. If you took away gravity (and somehow still held the bike down) or took away the gyro force (by having some magical device with 2 identical objects spinning in opposite directions in the same physical space) the bike would still turn using the other force involved.

Mille: I'm no engineer, I cant solve your problem (that and I really dont care). But if Aprilia (or rotax) came up with it, surely somebody else can figure out how it works. OK, so its extremely complicated math, but its not voodoo

and counter-rotating brakes? maybe he is onto something, maybe he is full of shit, but either way its too heavy and complex for any gains it might have

[PSk]

Originally Posted by Dezmo

Scott, you have the right idea, as the wheel is pulled the other way as the bike leans, but its being pulled by.....gyroscopic precession (gasp)

I really dont see how difficult this is to understand, it should be clear to anybody with a basic grasp of HS physics.

Now, do I think gravity does nothing to a turning bike? of course not, it helps...theres no denying that, but the predominant force making the bike lean is gyroscopic. If you took away gravity (and somehow still held the bike down) or took away the gyro force (by having some magical device with 2 identical objects spinning in opposite directions in the same physical space) the bike would still turn using the other force involved.

Mille: I'm no engineer, I cant solve your problem (that and I really dont care). But if Aprilia (or rotax) came up with it, surely somebody else can figure out how it works. OK, so its extremely complicated math, but its not voodoo

and counter-rotating brakes? maybe he is onto something, maybe he is full of shit, but either way its too heavy and complex for any gains it might have

Sorry don't agree. Gyroscopic force HELPS a wheel stay vertical [CORRECTI