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Joseph Browning
02-05-2004, 01:50 PM
Andre Espalait (sp) had a good explanation of the mechanics of a tank slapper once and I can't find it anywhere. What are the dynamics behind the causes of a tank slapper? I'm not concerned with worn head bearings, bad tires, misaligned chain, or stuff like that- I am really angling after the underlying phsyics of the event. Seems like Keith Code blames it on frequency harmonics between the frame and the forks. Just interested.

Joseph Browning
02-05-2004, 01:50 PM
Andre Espalait (sp) had a good explanation of the mechanics of a tank slapper once and I can't find it anywhere. What are the dynamics behind the causes of a tank slapper? I'm not concerned with worn head bearings, bad tires, misaligned chain, or stuff like that- I am really angling after the underlying phsyics of the event. Seems like Keith Code blames it on frequency harmonics between the frame and the forks. Just interested.

Steve Breen
02-05-2004, 02:15 PM
Here\'s a decent explanation of the physics of oscillation in a physical system (http://www.kettering.edu/~drussell/Demos/SHO/mass.html)

There are some more pages there that describe lightly damped and undamped systems too.

Steering damper good. /ubbthreads/images/%%GRAEMLIN_URL%%/laugh.gif

Steve Breen
02-05-2004, 02:15 PM
Here\'s a decent explanation of the physics of oscillation in a physical system (http://www.kettering.edu/~drussell/Demos/SHO/mass.html)

There are some more pages there that describe lightly damped and undamped systems too.

Steering damper good. /ubbthreads/images/%%GRAEMLIN_URL%%/laugh.gif

KELLY DAVIS
02-06-2004, 09:26 PM
tank slapper or highside?

KELLY DAVIS
02-06-2004, 09:26 PM
tank slapper or highside?

marcus mcbain
02-08-2004, 08:39 AM
Tank Slappers were really common on motorcycles from the 1980's and earlier. On both bikes I rode and other bikes, there were/are three dominant causes for Tank Slappers.

1) The most common cause was when the owner/builder "beefed up" (strengthened) a particular area of a motorcycle. Usually this was either the swing arm or forks/triple clamps. Sometimes, builders would also weld up/brace the cradle area below the seat/tank seam. Regardless, all this usually achieved was that you changed the characteristics of the frame harmonics from consistent flex throughout the motorcycle to one very stout area and two or three areas where the bike would won't to oscillate violently.

2) In modern bikes, the most common cause is improper wieght bias in conjuntion with improper spring/valving rates. This means that you have two much/little ride height on the front or rear that the most cause is those NEW TIRES THAT YOUR TIRE GUY GAVE YOU A GREAT DEAL ON JUST CHANGED YOUR GEOMETRY.

3) As alluded to in point #2, sometimes you just need to get your bike's suspension checked.

Thought about steering dampers. The best definition of what a steering damper does is, "It is a band aid for a problem with your motorcycle".

I have seen many, many riders just crank the crap out of their steering damper as normal procedures. Why? I have raced some of the most violent bikes now and then and I can tell you that if your bike works properly, you don't need a steering damper. (They are handy when you don't quite know how to fix the problem and need some immediate help though).

Good Luck,
Marcus

marcus mcbain
02-08-2004, 08:39 AM
Tank Slappers were really common on motorcycles from the 1980's and earlier. On both bikes I rode and other bikes, there were/are three dominant causes for Tank Slappers.

1) The most common cause was when the owner/builder "beefed up" (strengthened) a particular area of a motorcycle. Usually this was either the swing arm or forks/triple clamps. Sometimes, builders would also weld up/brace the cradle area below the seat/tank seam. Regardless, all this usually achieved was that you changed the characteristics of the frame harmonics from consistent flex throughout the motorcycle to one very stout area and two or three areas where the bike would won't to oscillate violently.

2) In modern bikes, the most common cause is improper wieght bias in conjuntion with improper spring/valving rates. This means that you have two much/little ride height on the front or rear that the most cause is those NEW TIRES THAT YOUR TIRE GUY GAVE YOU A GREAT DEAL ON JUST CHANGED YOUR GEOMETRY.

3) As alluded to in point #2, sometimes you just need to get your bike's suspension checked.

Thought about steering dampers. The best definition of what a steering damper does is, "It is a band aid for a problem with your motorcycle".

I have seen many, many riders just crank the crap out of their steering damper as normal procedures. Why? I have raced some of the most violent bikes now and then and I can tell you that if your bike works properly, you don't need a steering damper. (They are handy when you don't quite know how to fix the problem and need some immediate help though).

Good Luck,
Marcus

Chuck C.
03-08-2004, 09:23 AM
<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">I have seen many, many riders just crank the crap out of their steering damper as normal procedures. Why? I have raced some of the most violent bikes now and then and I can tell you that if your bike works properly, you don't need a steering damper. (They are handy when you don't quite know how to fix the problem and need some immediate help though).
</div></div>Correct me if I am wrong but doesn't Moto GP
teams use dampers? If so why would they need this "band aid". If they can't get a bike to handle who can? I find it doubtful that they would be so used if not needed, or at least helped handling some.

Could this be a case of better safe than sorry?

Thanks,
chuck

Chuck C.
03-08-2004, 09:23 AM
<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">I have seen many, many riders just crank the crap out of their steering damper as normal procedures. Why? I have raced some of the most violent bikes now and then and I can tell you that if your bike works properly, you don't need a steering damper. (They are handy when you don't quite know how to fix the problem and need some immediate help though).
</div></div>Correct me if I am wrong but doesn't Moto GP
teams use dampers? If so why would they need this "band aid". If they can't get a bike to handle who can? I find it doubtful that they would be so used if not needed, or at least helped handling some.

Could this be a case of better safe than sorry?

Thanks,
chuck

marcus mcbain
03-08-2004, 11:55 AM
Like I said,

It is a band-aid when things arem't working right. A Moto-GP bike is something you and I will never ride. High HP brings on different dynamics. I will use T6 at TWS as an example. Coming out there are some ripples in the pavement that combined with the fact that larger bike is almost at a "wheelie" the whole way through there caused the front end to skip and shake. The real problem is the fact that there is too much rear end squat. I don't remember having to crank the steering damper at TWS higher than off. Many times on a bike, you have to decide to wheelie the bike to take those situations out of play.

Several people have rode my 1000's. Ask Travis Pierce if the bike ever one-time even shook its head wrong. Steering damper is off ALWAYS. Again, if you can't get a bike sorted out, turn it on a bit. If you are at Daytona (an animal unto itself), turn it up.

95% of the time you don't need it. Rules require them now, because indeed sometimes a rider does need it. I just find that many riders immediately go to tighten the damper up (which makes the bike less likely to turn easily) rather than look at the source of the problem.

Marcus

marcus mcbain
03-08-2004, 11:55 AM
Like I said,

It is a band-aid when things arem't working right. A Moto-GP bike is something you and I will never ride. High HP brings on different dynamics. I will use T6 at TWS as an example. Coming out there are some ripples in the pavement that combined with the fact that larger bike is almost at a "wheelie" the whole way through there caused the front end to skip and shake. The real problem is the fact that there is too much rear end squat. I don't remember having to crank the steering damper at TWS higher than off. Many times on a bike, you have to decide to wheelie the bike to take those situations out of play.

Several people have rode my 1000's. Ask Travis Pierce if the bike ever one-time even shook its head wrong. Steering damper is off ALWAYS. Again, if you can't get a bike sorted out, turn it on a bit. If you are at Daytona (an animal unto itself), turn it up.

95% of the time you don't need it. Rules require them now, because indeed sometimes a rider does need it. I just find that many riders immediately go to tighten the damper up (which makes the bike less likely to turn easily) rather than look at the source of the problem.

Marcus

Chuck C.
03-09-2004, 09:00 AM
O.K. i see what your saying. If your bikes head shaking don't assume its normal, and certainly dont't just crank up the steering damper to compensate. Good advice, and your comments on dampers makes much more sense to me now.

One of my few and worst head shakes was on the street. I rolled on the gas hard in 1st (rear end squats) and as i neared red line the front caught some wavy asphalt (lightend front end). Well you know what happend next /ubbthreads/images/%%GRAEMLIN_URL%%/eek.gif Seemed to last forever as I had time to look at where I was heading and where I might bail off or impact. Sucked!! It cleared and I stayed up, but was one of those times I had to question if I liked riding enough to deal with the risk.

See you at the track Friday!

Chuck C.

Chuck C.
03-09-2004, 09:00 AM
O.K. i see what your saying. If your bikes head shaking don't assume its normal, and certainly dont't just crank up the steering damper to compensate. Good advice, and your comments on dampers makes much more sense to me now.

One of my few and worst head shakes was on the street. I rolled on the gas hard in 1st (rear end squats) and as i neared red line the front caught some wavy asphalt (lightend front end). Well you know what happend next /ubbthreads/images/%%GRAEMLIN_URL%%/eek.gif Seemed to last forever as I had time to look at where I was heading and where I might bail off or impact. Sucked!! It cleared and I stayed up, but was one of those times I had to question if I liked riding enough to deal with the risk.

See you at the track Friday!

Chuck C.