Longer lasting cush drive material available

[Hairy Cannonball]

Guys guys, you are going about this all wrong. What you need to do is replace all the rubbers, not just half of them, with genetically engineered gerbils. Under acceleration the gerbils would initially squish because they were asleep and relaxed, however upon being awakened they would become angry and tense firming up the dampening. Then they would frantically run inside the cush drive adding race winning horsepower as long as it was Friday. You could drill holes in the gerbils if that is your thing. Once in a while you could add a nice stinky cheese to the cush drive to keep the gerbils happy. I am pretty sure this would work.

 

[dlaing]

Guys guys, you are going about this all wrong. What you need to do is replace all the rubbers, not just half of them, with genetically engineered gerbils. Under acceleration the gerbils would initially squish because they were asleep and relaxed, however upon being awakened they would become angry and tense firming up the dampening. Then they would frantically run inside the cush drive adding race winning horsepower as long as it was Friday. You could drill holes in the gerbils if that is your thing. Once in a while you could add a nice stinky cheese to the cush drive to keep the gerbils happy. I am pretty sure this would work.

 

Did you get your name, Hairy Cannonball, from your expertise with gerbils?

Finally an expert worthy of answering my questions!!!!

Do you use muscle relaxants?

How do you get them out?

Have you ever had rabies?

Do you think when you die you will be reincarinated into a gerbil used for some idiot's pleasure?

Can intellectual pursuits in engineering be degraded even further?

[Hairy Cannonball]

Did you get your name, Hairy Cannonball, from your expertise with gerbils?

Finally an expert worthy of answering my questions!!!!

Do you use muscle relaxants?

How do you get them out?

Have you ever had rabies?

Do you think when you die you will be reincarinated into a gerbil used for some idiot's pleasure?

Can intellectual pursuits in engineering be degraded even further?

 

No, it actually came from my inability to swim.

 

Thank you!!

 

Not on myself

 

You never need to

 

Once, but not from the gerbils

 

Gawd I sure hope not.

 

We can try!!!! :lol:

[Ryland3210]

So, 60 foot pounds would be multiplied by 11.7589 to give us 705.534.

I know my bike with roughly 60 foot pounds of torque can't lift the front wheel without a bit of coercion.

How much more torque can we get by popping the clutch?

We know it is enough to bring the front wheel up, and I know that my bike won't wheelie from simply giving it 705 foot pounds of torque at the rear axle.

It does seem unlikely that we would have to escalate the force from 705 to 1250 just to make the front wheel come off the ground.

Assuming my 1250 number is correct, that would correspond to 106 foot pound of engine torque following the owner's manual's 11.7589 ratio.

That does seem a bit high. The true force to lift the front wheel is probably somewhere between 1250 and 705 foot pounds.

 

 

Dave, I think you should consider that a. The force at the rear wheel contact patch is generating a moment around the CG of bike and rider and b. Rear wheel torque then needs to equal this force at the contact patch times wheel radius.

 

Assume the height of the CG is 2ft, (wild guess). The force at the patch would be (1250ft-lb)/(2ft) for 625lb. The rear tire has a radius about 13", so torque at the wheel would need to be 625lbX((13/12)ft or 677ft-lb. Your 705ft-lb then puts you in wheelie land. (But this is too easy. Maybe the front wheel gets more than 250lb and/or maybe the CG is lower than 2ft.)

 

To make the math simple, assuming a weight of 600 pounds at a center of gravity 2 feet above the ground, to calculate the force required at the contact patch to lift that weight, one must know the horizontal distance from the contact patch to the center of gravity. Let's assume that's 3 feet. The torque applied by gravity about the axis of the contact patch is then 600 X 3 feet, or 1800 foot pounds. The force required at the contact patch to offset that is 1800 foot pounds divided by 2 feet, or 900 pounds. The torque required on the wheel is then 900 X Wheel radius. If we assume a 1 foot radius, then the torque required is 900 foot pounds.

 

That's more than Dave's calculated 705. However, the engine has significant rotational inertia, and can dump that energy through the drive train to temporagenerate the required 900 foot pounds, provided the clutch's dynamic frictional torque capacity exceeds that and doesn't slip instead. The static friction between tire and road must also exceed that generated by the weight of the bike on the contact patch. You can see from the equations that the higher the ratio of the height of the CG to the horizontal distance from contact patch to the CG, the easier it is to pop a wheelie. Once the front wheel is lifted off the ground, that ratio increases as the CG goes higher, and the horizontal distance decreases. That's why it easy to maintain a wheelie, once the front wheel is elevated.

 

For example, my Norton and Guzzi Cafe Sport easily can pop a wheelie, whereas my Venture burns rubber because of very different CG vertical to horizontal ratios.

 

Hill climbers want to avoid wheelies, so the rear wheel is moved way behind the rider.

 

This isn't nearly as entertaining, but it's my nature.

 

Oh, almost forgot! So the peak torque on the rubber baby buggy bumpers is limited by the dynamic frictional torque the clutch can transfer, or the static frictional force of the contact patch times the wheel radius, whichever is less, when the engine's inertial energy is transfered in addition to its torque output. Usually, conservatively designed clutches will exceed the latter, and force the contact patch to skid before the clutch slips. The equations to calculate the peak torque generated are somewhat complex, but in summary, the change in the engine's momentum as its RPM's decline when the clutch is dumped, is proportional to the integral of torque times the time it takes.

[Guest ratchethack]

Guys guys, you are going about this all wrong. What you need to do is replace all the rubbers, not just half of them, with genetically engineered gerbils. Under acceleration the gerbils would initially squish because they were asleep and relaxed, however upon being awakened they would become angry and tense firming up the dampening. Then they would frantically run inside the cush drive adding race winning horsepower as long as it was Friday. You could drill holes in the gerbils if that is your thing. Once in a while you could add a nice stinky cheese to the cush drive to keep the gerbils happy. I am pretty sure this would work.

 

Mr. Cannonball, may I congratulate you. You may be new around here, but it sure didn't take you long to pick up on the um, somewhat, er nuanced, "inside baseball" that's being played here. Like Dan, Paul, and all the rest who also seem to've not missed too much here (though they ought not -- they've all been here long enough! ) I do b'lieve you've grasped the true essence of this thread immediately!

 

I do b'lieve you've nailed down exactly wot "intellectual pursuits in engineering" means here. Possibilities of degrading such standards as we've seen in this thread. . . ?!

 

Over on the "Banter" Forum, DeBen's promoting some great bomber of a cigar called "The God of Fire". For all I know, this could be somethin' like a Roman candle. But wotever this thing is, DeBen seems to think it's a great prize. Now if I were DeBen, and I had one to give you -- why, I reckon that's exactly wot I'd do, simply because you're so quick on the up-take!

 

Nice to have you on board!

[savagehenry]

QUOTE (Hairy Cannonball @ Feb 21 2008, 02:36 AM)

Guys guys, you are going about this all wrong. What you need to do is replace all the rubbers, not just half of them, with genetically engineered gerbils. Under acceleration the gerbils would initially squish because they were asleep and relaxed, however upon being awakened they would become angry and tense firming up the dampening. Then they would frantically run inside the cush drive adding race winning horsepower as long as it was Friday. You could drill holes in the gerbils if that is your thing. Once in a while you could add a nice stinky cheese to the cush drive to keep the gerbils happy. I am pretty sure this would work.

 

 

...and Ratch added...

Mr. Cannonball, may I congratulate you. You may be new around here, but it sure didn't take you long to pick up on the um, somewhat, er nuanced, "inside baseball" that's being played here. Like Dan, Paul, and all the rest who also seem to've not missed too much here (though they ought not -- they've all been here long enough! ) I do b'lieve you've grasped the true essence of this thread immediately!

 

I do b'lieve you've nailed down exactly wot "intellectual pursuits in engineering" means here. Possibilities of degrading such standards as we've seen in this thread. . . ?!

 

Over on the "Banter" Forum, DeBen's promoting some great bomber of a cigar called "The God of Fire". For all I know, this could be somethin' like a Roman candle. But wotever this thing is, DeBen seems to think it's a great prize. Now if I were DeBen, and I had one to give you -- why, I reckon that's exactly wot I'd do, simply because you're so quick on the up-take!

 

Nice to have you on board!(END QUOTE)

 

...and to this I say...

You two are both on reefer sticks. Gerbils? Really...the OBVIOUS answer is: BANDICOOTor WOLVERINE. Genetic engineering is expensive,and takes alot of choo choo trains. And wolverines are particularily cheap in todays market...

 

And Ry, I knew I could count on you, you science freek, you

 

"When things get weird, the weird turn professional..."HST, Gods rest his soul, Love,S.H.

 

P.S. Jaap, forget banishment, let the CANEINGS BEGIN!!! "Thank You Sir, May I Have Another!!!"

[dlaing]

So, here is a recap:

Is "noticeably smoother" a good thing.

If you put a softer spring on your shock absorber, you may get a smoother ride over the smooth bumps, but the bumps that will break your spine are the nasty unexpected potholes that bottom out the shock and move your tailbone closer to your skull.

If you simply soften up your cush by drilling, you may get a smoother feel over the smooth normal shifts, but the shifts that will break your spline are the nasty unexpected shifts and aggressive clutch actions that make the front wheel come up or the rear wheel lock.

Is this compressing the rubbers to a bottomed out state?

I stuck one of the wedges in my door jam and started closing the door and watched as the rubber bushing wedge that is not chrome-alloy hard effortlessly mushed into a flattened out pancake.

Without some sort of meter measuring movement in the cush housing, I ain't sold on the drilling.

Or maybe someone can do the math to convert the torque at the cush to the torque measured on the dyno (about 60 foot pounds, although I get with clutch action you get the torque to momentarily be a bit higher).

If the wheel base is about 58.66 inches and the front of the bike with rider weighs 250lbs and one can pop a wheelie, doesn't that mean that we can divide 58.66 by 12 and get roughly 5, and multiply 5 times the 250pounds we get about 1250 foot pounds of torque.

Please correct me if I am wrong, but I think that would be like putting a wedge in the crook of a one foot lever and squashing down with about 208lbs of force. (1250 foot pounds spread over 6 wedges.(there are 12 wedges altogether, right?))

Assuming I got the math and theory right, it should be easy to test a wedge and see if the holes help.

Any "holes" in this theory?

The big hole I missed was the Center of Gravity.

But it was not caught by Ratchet, whose math or physics was off by over ten fold.

You already set me straight?? But. . . but Dave. I thought there was something wrong with my math?!?! You said so twice above.

 

snip

Though it's perfectly legitimate to consider the torque force on ALL cush drive blocks at the same time (that's a given here, it's 65 lbs./ft. max)

And then I came up with a second theory/question.

But I think your math is off.

I think that while the dyno is measuring RWHP, it is not measuring axle torque.

The measured torque is probably an estimate of the torque at the crank.

Geared down to first gear where we can pop a wheelie that torque is multiplied.

But how much?

Can we simply use the ratios from the owner's manual?

first gear is 1:11.7589 (engine-wheel)

So, 60 foot pounds would be multiplied by 11.7589 to give us 705.534.

I know my bike with roughly 60 foot pounds of torque can't lift the front wheel without a bit of coercion.

How much more torque can we get by popping the clutch?

We know it is enough to bring the front wheel up, and I know that my bike won't wheelie from simply giving it 705 foot pounds of torque at the rear axle.

It does seem unlikely that we would have to escalate the force from 705 to 1250 just to make the front wheel come off the ground.

Assuming my 1250 number is correct, that would correspond to 106 foot pound of engine torque following the owner's manual's 11.7589 ratio.

That does seem a bit high. The true force to lift the front wheel is probably somewhere between 1250 and 705 foot pounds.

To which Ratchet replied

I'm clearly on a different planet altogether. Help me.

 

Set me straight, please. I'm begging you.

 

Hilfe, Mr. Wizard!

 

Aufenthaltsort Wernher? Aufenthaltsort Albert?

Thankfully, Troy came up with the CG factor that I had completely missed:

So, 60 foot pounds would be multiplied by 11.7589 to give us 705.534.

I know my bike with roughly 60 foot pounds of torque can't lift the front wheel without a bit of coercion.

How much more torque can we get by popping the clutch?

We know it is enough to bring the front wheel up, and I know that my bike won't wheelie from simply giving it 705 foot pounds of torque at the rear axle.

It does seem unlikely that we would have to escalate the force from 705 to 1250 just to make the front wheel come off the ground.

Assuming my 1250 number is correct, that would correspond to 106 foot pound of engine torque following the owner's manual's 11.7589 ratio.

That does seem a bit high. The true force to lift the front wheel is probably somewhere between 1250 and 705 foot pounds.

 

 

Dave, I think you should consider that a. The force at the rear wheel contact patch is generating a moment around the CG of bike and rider and b. Rear wheel torque then needs to equal this force at the contact patch times wheel radius.

 

Assume the height of the CG is 2ft, (wild guess). The force at the patch would be (1250ft-lb)/(2ft) for 625lb. The rear tire has a radius about 13", so torque at the wheel would need to be 625lbX((13/12)ft or 677ft-lb. Your 705ft-lb then puts you in wheelie land. (But this is too easy. Maybe the front wheel gets more than 250lb and/or maybe the CG is lower than 2ft.)

And Ryland added with great clarity that even a gerbil with a high school diploma can understand:

To make the math simple, assuming a weight of 600 pounds at a center of gravity 2 feet above the ground, to calculate the force required at the contact patch to lift that weight, one must know the horizontal distance from the contact patch to the center of gravity. Let's assume that's 3 feet. The torque applied by gravity about the axis of the contact patch is then 600 X 3 feet, or 1800 foot pounds. The force required at the contact patch to offset that is 1800 foot pounds divided by 2 feet, or 900 pounds. The torque required on the wheel is then 900 X Wheel radius. If we assume a 1 foot radius, then the torque required is 900 foot pounds.

 

That's more than Dave's calculated 705. However, the engine has significant rotational inertia, and can dump that energy through the drive train to temporagenerate the required 900 foot pounds, provided the clutch's dynamic frictional torque capacity exceeds that and doesn't slip instead. The static friction between tire and road must also exceed that generated by the weight of the bike on the contact patch. You can see from the equations that the higher the ratio of the height of the CG to the horizontal distance from contact patch to the CG, the easier it is to pop a wheelie. Once the front wheel is lifted off the ground, that ratio increases as the CG goes higher, and the horizontal distance decreases. That's why it easy to maintain a wheelie, once the front wheel is elevated.

 

For example, my Norton and Guzzi Cafe Sport easily can pop a wheelie, whereas my Venture burns rubber because of very different CG vertical to horizontal ratios.

 

Hill climbers want to avoid wheelies, so the rear wheel is moved way behind the rider.

 

This isn't nearly as entertaining, but it's my nature.

 

Oh, almost forgot! So the peak torque on the rubber baby buggy bumpers is limited by the dynamic frictional torque the clutch can transfer, or the static frictional force of the contact patch times the wheel radius, whichever is less, when the engine's inertial energy is transfered in addition to its torque output. Usually, conservatively designed clutches will exceed the latter, and force the contact patch to skid before the clutch slips. The equations to calculate the peak torque generated are somewhat complex, but in summary, the change in the engine's momentum as its RPM's decline when the clutch is dumped, is proportional to the integral of torque times the time it takes.

Which is all excellent, but I disagree that "the peak torque on the rubber baby buggy bumpers is limited by the dynamic frictional torque the clutch can transfer, or the static frictional force of the contact patch"

In acceleration mode it is limited by the front wheel lifting and in deceleration mode, it is limited by the frictional force of the contact patch.

 

"rubber baby buggy bumpers"

Very nice!

[Troy]

To make the math simple, assuming a weight of 600 pounds at a center of gravity 2 feet above the ground, to calculate the force required at the contact patch to lift that weight, one must know the horizontal distance from the contact patch to the center of gravity. Let's assume that's 3 feet. The torque applied by gravity about the axis of the contact patch is then 600 X 3 feet, or 1800 foot pounds. The force required at the contact patch to offset that is 1800 foot pounds divided by 2 feet, or 900 pounds.

 

John, I was surprised on going through these numbers that the rear tire exhibited a coefficient of friction near one. But your iteration gets a coefficient of friction of 1.5, with a 600lb weight and a 900lb shear force at the tire patch. Is that one sticky tire, or what?

[Hairy Cannonball]

Ratchethack, we are going to have to find some of those God of Fire seeegahrs and a good bourbon and enjoy em some time.

 

Dlaing and all others, this has been a very interesting thread, and I must say it prompted me, since it was too cold out to ride here anyway, to take my cush drive apart for a clean up. Now I ain't never ever gonna tell anyone nohow noway whether or not I drilled or greased the rubbers in there, but I did find the bearing surface between the cush drive plate and the hub rusty so I cleaned that and gave it a good lubing.

 

And, just for clarity, no gerbils were harmed during the maintenance procedure. :rolleyes:

[dlaing]

Now I ain't never ever gonna tell anyone nohow noway whether or not I drilled or greased the rubbers in there...

Whether you drilled or not, there is no need for shame.

Some Guzzis run with no cush, so unless you drilled the

"rubber baby buggy bumpers" to the point of imminent deterioration, you still got cush.

[Guest ratchethack]

. . .Now I ain't never ever gonna tell anyone nohow noway whether or not I drilled or greased the rubbers in there. . .

Good move. This seems to have the potential of becoming the equivalent of making a confession of wot oil you use. In the dead of Winter -- not a good call, unless you're interested in launching a wild clusterfest/speculation extravaganza the likes o' which could make this thread look reasonable.

[Ryland3210]

So, here is a recap:

 

The big hole I missed was the Center of Gravity.

But it was not caught by Ratchet, whose math or physics was off by over ten fold.

 

And then I came up with a second theory/question.

 

To which Ratchet replied

 

Thankfully, Troy came up with the CG factor that I had completely missed:

 

And Ryland added with great clarity that even a gerbil with a high school diploma can understand:

 

Which is all excellent, but I disagree that "the peak torque on the rubber baby buggy bumpers is limited by the dynamic frictional torque the clutch can transfer, or the static frictional force of the contact patch"

In acceleration mode it is limited by the front wheel lifting and in deceleration mode, it is limited by the frictional force of the contact patch.

 

"rubber baby buggy bumpers"

Very nice!

 

I stand by my statement, but I think I may have not made it clear enough with the "or". That was intended to mean the lesser of the two. For example, if the clutch were covered with teflon and its springs were weak enough, then it would slip and be the limiting factor and prevent the wheelie. If instead, the clutch was normal, but the rear wheel was on ice, then it would be the limiting factor and still prevent a wheelie. If both have high friction, you might think the limiting factor would be only what it takes to lift the front wheel in accelerating mode, but that overlooks the inertia of the bike resisting its rotation about the contact patch as it lifts the CG.

 

To make the point with an extreme example, suppose the clutch and contact patch were replaced with rigid connections (infinite friction). If the engine is rev'd up and clutch dumped, the initial peak torque would be extremely high. If there was no elasticity in the driveline, it would theoretically be infinite but for a very short time.

[Ryland3210]

John, I was surprised on going through these numbers that the rear tire exhibited a coefficient of friction near one. But your iteration gets a coefficient of friction of 1.5, with a 600lb weight and a 900lb shear force at the tire patch. Is that one sticky tire, or what?

 

Hi Troy,

Keep in mind my numbers were only estimates to make the math easy, but they are in the ballpark. Static friction coefficients of 1 are not at all unusual for ordinary tires, and even higher, for relatively sticky tires. For example, the cornering G's pulled by Corvettes and many other sports cars approach 1, and that's under less sticky conditions than a standing start.

 

Consider also some sport bikes tests indicating cornering angles greater than the 45 degrees corresponding to 1 G, and a coefficient of friction of at least 1 as well, again while the tires is moving.

[dlaing]

I stand by my statement, but I think I may have not made it clear enough with the "or". That was intended to mean the lesser of the two. For example, if the clutch were covered with teflon and its springs were weak enough, then it would slip and be the limiting factor and prevent the wheelie. If instead, the clutch was normal, but the rear wheel was on ice, then it would be the limiting factor and still prevent a wheelie. If both have high friction, you might think the limiting factor would be only what it takes to lift the front wheel in accelerating mode, but that overlooks the inertia of the bike resisting its rotation about the contact patch as it lifts the CG.

 

To make the point with an extreme example, suppose the clutch and contact patch were replaced with rigid connections (infinite friction). If the engine is rev'd up and clutch dumped, the initial peak torque would be extremely high. If there was no elasticity in the driveline, it would theoretically be infinite but for a very short time.

Excellent point about the inertia.

Yes, I would agree that if the engine is rev'd up up high enough and clutch is dumped the clutch might slip or the rear wheel MIGHT slip before and or while raising the front end, the clutch would more likely slip in higher gears.

I hope that is not the real world way that people treat their Guzzi, but if so, you are correct.

But you are not correct about infinite torque, although the torque could be large enough to break the driveline, but assuming by no elasticity you mean it is also unbreakable and the only give is the cush and the rising of the front wheel, you still could not reach infinity even with one of them 600HP Hayabusas and a one ton fly wheel.

Dumping the clutch might be equivalent to shooting a cannon at a torque wrench with deflection equal to that of the cush rubbers when the wrench is metering its maximum of One Trillion foot pounds, with the torque wrench hooked to the axle in such a way that it turns the wheel. It won't reach even One Trillion foot pounds. Maybe a patriot missile might reach a trillion foot pounds. Infinity is a much larger number than what is relevant here.

Still you made an excellent point that the impact force can be far higher than steady engine acceleration, and that the clutch or tire traction could give before the front wheel rises and if the force is high enough the clutch or tire friction will surely give before the front end rises.

This reinforces the potential benefits of a bushing that could better absorb the impact of a dumped clutch!!!!!

[Ryland3210]

Excellent point about the inertia.

Yes, I would agree that if the engine is rev'd up up high enough and clutch is dumped the clutch might slip or the rear wheel MIGHT slip before and or while raising the front end, the clutch would more likely slip in higher gears.

I hope that is not the real world way that people treat their Guzzi, but if so, you are correct.

But you are not correct about infinite torque, although the torque could be large enough to break the driveline, but assuming by no elasticity you mean it is also unbreakable and the only give is the cush and the rising of the front wheel, you still could not reach infinity even with one of them 600HP Hayabusas and a one ton fly wheel.

Dumping the clutch might be equivalent to shooting a cannon at a torque wrench with deflection equal to that of the cush rubbers when the wrench is metering its maximum of One Trillion foot pounds, with the torque wrench hooked to the axle in such a way that it turns the wheel. It won't reach even One Trillion foot pounds. Maybe a patriot missile might reach a trillion foot pounds. Infinity is a much larger number than what is relevant here.

Still you made an excellent point that the impact force can be far higher than steady engine acceleration, and that the clutch or tire traction could give before the front wheel rises and if the force is high enough the clutch or tire friction will surely give before the front end rises.

This reinforces the potential benefits of a bushing that could better absorb the impact of a dumped clutch!!!!!

 

I'm still convince my statement is correct. It was qualified by "theoretically". Of course the peak torque would not be infinite in the real world! The key point is that I did not assume the only elasticity is the cush. If you read my statement carefully, you will see I assumed no elasticity. No means no!

 

In the equations to calculate the peak torque, the rotary inertia of the bike will be in the numerator and the time it takes to transfer the engine's energy to the bike will be in the denominator. The rotary inertia is more than zero no matter how much the bike weighs, unless all of its mass is in a single point, which is absurd. If there is no elasticity in the driveline (and just in case you think of it, none in the tires either, which I consider are part of the driveline for the purpose of this discussion) then the time is zero, and the result of the calculation something divided by zero, which is infinity.