Weaves, Wobbles, and Tank-Slappers

Message

Boiler · #1 Unread post by **Boiler** » Wed Nov 01, 2006 1:39 pm

Hi:

I’m new to the forum and doing research in motorcycle dynamics and stability. In particular I’m interested in what is variously called weave, wobble, and tank-slapper. I would like to know if anyone has experienced a weave, wobble, or tank-slapper, or knows someone who has, and would be willing to share what happened.

In particular I am interested in the circumstances under which the weave, wobble, or tank-slapper occurred. Things like:

What type of motorcycle were you riding?
How fast were you going?
Were you accelerating or slowing down?
Were you going straight or in a turn?
What did you do to stop the weave, wobble, or tank-slapper?
What did you do to make sure it did not happen again?

In other words I’m interested in as many facts about the incident as you can give.

To help me in my research I have started a forum specifically for discussions about weave, wobble, and tank-slappers. Again, if you have experienced a weave, wobble or tank-slapper, or know of some one who has, and would be willing to share the experience please go to www.motorcycle-dynamics.com/smf/index.php?board=1.0

Thanks in advance.

Sev · #2 Unread post by **Sev** » Wed Nov 01, 2006 2:30 pm

2004 Honda 599.
Doing about a buck fifty (km).
I was accelerating up a hill in a corner and hit a small bump mid corner.
She shook her head hard enough to swing loose my left mirror.

Loosened up on the bars and accelerated slightly and the shake dissapeared.

I broke down the front end, inspected the steering head bearings, and repacked the grease.

Is that everything?

Mintbread · #3 Unread post by **Mintbread** » Wed Nov 01, 2006 6:58 pm

I get head shake all the time on my current bike and just about every bike I have owned (except my TL which had a steering damper).

I had a Yamaha RZ500 that produced tank slappers all the time. Always under acceleration and usually remedied by backing off the throttle.

My best tank slapper was on my '96 1200 Bandit (RIP).

I was accelerating around a slight bend, the front wheel was off the deck and the back slid out a touch. I felt it going and backed off a little and as it grabbed on the front wheel landed a little skewed. Bars were ripped clean out of my hands and over I went.

I never consciously do anything to prevent them happening but attempt to solve the problem as it arises.

Lion_Lady · #4 Unread post by **Lion_Lady** » Thu Nov 02, 2006 4:11 am

You might want to define the terms first.

To me a 'weave' is an intentional act. A 'wobble' could be, and a tankslapper definitely is NOT intentional.

P

#5 Unread post by **fireguzzi** » Thu Nov 02, 2006 5:17 am

A weave wobble and tankslapper basically just refers to the frequency of the front end turning back and forth.

A weave is slow

A wobble is faster

And of course a tank slapper is very violent and fast.

And I think they were referring to unintentional.

#6 Unread post by **sv-wolf** » Thu Nov 02, 2006 8:23 am

I found this a little while back. It challenges several things I had always believed about how bikes turned and what caused wobble and tankslappers. Who knows?

http://www.reverserotatingrotors.com/index.html

Check out the First Test Video to see what this guy is talking about.

Sorry Boiler, slightly off topic, but of related interest.

No significant wobble on SV1000S which has a steering damper, and never had a tank slapper.

Thu Nov 02, 2006 10:07 am

1976 yamaha rd400--passing car at 50 mph in left hand curve tank slapper started accelerated on through it.stopped cleaned out underwear.steering stem bearings loose.
i have had 5 1982 honda v45 sabres,every one of them has had a head shake between 40-45 mph.regardless of tire brand.

tripletrouble · Sat Feb 10, 2007 3:41 am

Years ago on my Commando doing about 95 mph when it went into a violent tank slapper, hard lock to lock. I was going in a straight line on the highway at the time. I had heard the best thing was to accelerate out of it and I figured I might as well die a 110 mph as 95 so I cranked it. The bike straightened out for a couple of seconds and I got hard on the brakes , pulled over and stopped for about 30 minutes until my heart slowed. Turned out to be a worn swing arm pivot, common on Commandos until you apply "the fix".

Pongo · #9 Unread post by **Pongo** » Mon Feb 12, 2007 10:23 am

Good to see someone else who had a commando.

Mine used to give me lots of warning when it was time to shim the isolastics. Just didn't feel so sure footed.

tripletrouble wrote:Years ago on my Commando doing about 95 mph when it went into a violent tank slapper, hard lock to lock. I was going in a straight line on the highway at the time. I had heard the best thing was to accelerate out of it and I figured I might as well die a 110 mph as 95 so I cranked it. The bike straightened out for a couple of seconds and I got hard on the brakes , pulled over and stopped for about 30 minutes until my heart slowed. Turned out to be a worn swing arm pivot, common on Commandos until you apply "the fix".

Fathertork · Mon Feb 12, 2007 1:02 pm

In New Bruswick Taking a short cut to the Plaster Rock Hwy, the road was gravel and I soon found out it had patches like sand traps.

Following two other Bikes, I hit one at 50 MPH and the bars were going stop to stop very fast (torn from my hands). Finally regained controll of the bars and brought the New 1989 FLHT to a stop.

Cause: Bike overloaded and light on the front end.

Cure: Do not overload.

The wife was with me and we were very lucky we never went down. Hey she still rides with me