SuzukiSavage.com - Death wobble

HAPPYDAN

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Re: Death wobble
Reply #15 - 11/03/16 at 08:15:06

It was reported that Kawasakis of the '60s and early '70s had a similar problem. A side-to side oscillation would begin slowly at certain speeds, increasing in frequency until the rider backed off or fell off. Riders blamed all sorts of things, and as a fix Kawasaki added a little shock absorber between the frame and fork on the right side. Ultimately, the frame geometry was found to be at fault. Did HD accidentally re-create Tesla's Earthquake Machine? Some Chuggers might like to think so!

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justin_o_guy2

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Re: Death wobble
Reply #16 - 11/03/16 at 08:18:39

One of Dave's links show a Dyna sans engine. The guy is shaking the transmission and rear end effortlessly.
It's not exactly stable.
Conflicting stories on the crash/ double fatality on the rally ride.
Wife says rumors at the hospital were
He was going fast and the handlebars started wobbling...
Guy in Texarkana says our Longview paper said he was flying up on Something and elected to lay it down.
Wife says the dead man's son ran over his dads head,, but, no dependable Source.

The reports indicate heavy front end damage, but I didn't see wreckers to attend cars, only an ambulance passed us.

Reports of the bikes damage at LEAST were from other riders, that day, not chatty nurses.

I've just been Allowing it to wobble around, I don't Accelerate, naturally, but I hold the speed and go on till it settles down, usually, a couple of times it's been exciting enough to slowly ease back on the gas a bit..

Maybe I should see just how well the head bearings are adjusted..

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Ruttly

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Re: Death wobble
Reply #17 - 11/03/16 at 10:16:54

Bent frames, forks ,swingarms ,axles , loose steering head bearings. Bad wheel bearings ,bent wheels,mis matched tires , tire pressure take your pick it will drive you nuts trying to find a cause .

And that's not even close to a death wobble , that's when it wobbles so hard your wallet flys out your pocket, you can barely hang on totally out of control & brown spot them drawers , meet your maker kind of wobble , almost make your helmet spin around ,
I'll never ride again type of wobble. That's a death wobble!!!!'

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Re: Death wobble
Reply #18 - 11/03/16 at 10:52:42

Ruttly wrote on 11/03/16 at 10:16:54:

And that's not even close to a death wobble , that's when it wobbles so hard your wallet flys out your pocket, you can barely hang on totally out of control & brown spot them drawers , meet your maker kind of wobble , almost make your helmet spin around ,
I'll never ride again type of wobble. '

You mean like this?

https://www.youtube.com/watch?v=XiKmPFo6xNA

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justin_o_guy2 Serious Thumper Offline What happened? Posts: 55279 East Texas, 1/2 dallas/la.	Re: Death wobble Reply #19 - 11/03/16 at 11:05:41 There for just a split second I thought he had a chance. Bouncing off the wall didn't do him Any good,, Dang,, awful crash..
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Ruttly Serious Thumper Offline Thumpers Rule Posts: 5107 Manteca , CA Gender:	Re: Death wobble Reply #20 - 11/03/16 at 12:08:24 Thats It ! Horrible video , Isle of Man is as brutal as it gets !!! Makes me sick watching that , Thanks Dave
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Ruttly Serious Thumper Offline Thumpers Rule Posts: 5107 Manteca , CA Gender:	Re: Death wobble Reply #21 - 11/03/16 at 12:56:56 Had a front tire blow out at about 70 mph , on a BSA two lane road oncoming cars tank slapping death wobble , snapped the throttle off it got worse back on the throttle than eased out of it , White as a ghost & trembling just dropped the bike on the side of the road , but I saved it but there was no saving the fruit of the looms !!!
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Re: Death wobble
Reply #22 - 11/03/16 at 20:25:54

That guy survived the crash , 2nd video interviewing him !
I feel better knowing he didn't die !
Only the bravest race IOM and there's never a shortage willing riders to dare the TT !!!
Many have tried to end the racing on the Isle but none have succeeded , they say it's a monster that can't be killed , the races continue unabated !
Some people climb mountains while others were jump out of perfectly good aircraft but IOM riders are a breed apart, some of the best racers in the world won't race it. But it would be fun to do a couple laps of the Isle ,
At about 70 mph ! Grin

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Nigel-in-SoCal

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Re: Death wobble
Reply #23 - 11/03/16 at 22:35:57

oldNslow wrote on 11/03/16 at 07:58:32:

Quote:

I don't know about Sportsters, but Dyna and Touring bikes all share the same design fault: the rear fork is hinged not on the frame but on the gearbox.
Huh]

Take a peek at a Ducati Panigale. Steering stem and swingarm are both bolted to the motor/gearbox. Is that a design fault too,?

http://newatlas.com/ducati-panigale-1199-naked-fairings-frame-pictures/22035/

There have been, and I think there still are, MotoGP bikes that are built similarly.

The execution is likely more important than the design itself.

True! I think the front end, swing arm and rear sub frame are solid mounted to the engine on the Ducati. But the HD power plant is rubber mounted to the frame, I believe. That must be less stable.

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Steve H Serious Thumper Offline SuzukiSavage.com Rocks! Posts: 1223 Spartanburg, SC Gender:	Re: Death wobble Reply #24 - 11/04/16 at 07:09:25 You mean to tell me the swingarm is mounted on rubber bushings? What idiot thought up that one?
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Re: Death wobble
Reply #25 - 11/04/16 at 09:45:32

Steve H wrote on 11/04/16 at 07:09:25:

You mean to tell me the swingarm is mounted on rubber bushings?

What idiot thought up that one?

http://partsfinder.onlinemicrofiche.com/ronnies/showmodel.asp?Type=13&make=hd...

That's an 07 Street Bob, I had to pick a specific model to get the diagram, but they are all basically the same. The swingarm pivots on a shaft, through the back of the frame, with bearings, just like most other motorcycles.

Sportsters, at least the ones I'm familiar with, have a bolt and a bearing on each side rather than a through bolt/shaft.

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Re: Death wobble
Reply #26 - 11/04/16 at 14:13:35

oldNslow wrote on 11/04/16 at 09:45:32:

Steve H wrote on 11/04/16 at 07:09:25:

You mean to tell me the swingarm is mounted on rubber bushings?

What idiot thought up that one?

http://partsfinder.onlinemicrofiche.com/ronnies/showmodel.asp?Type=13&make=hd...

That's an 07 Street Bob, I had to pick a specific model to get the diagram, but they are all basically the same. The swingarm pivots on a shaft, through the back of the frame, with bearings, just like most other motorcycles.

Sportsters, at least the ones I'm familiar with, have a bolt and a bearing on each side rather than a through bolt/shaft.

I'm not so sure about that. Using the same site, the frame assembly fiche doesn't show any swingarm attachment features, but the transmission housing looks like it might. The Sportsters are probably different.

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Re: Death wobble
Reply #27 - 11/04/16 at 14:39:17

As to the cause of these oscillations, I've assumed that it is frame stiffness.
It's the weight of the engine swinging back and forth to cause the effect.
This could be torsion on the frame or it could be whippyness of the forks.
A camera on the handlebars pointed down the forks and one pointed back along the frame will tell exactly where the issue lies.

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Re: Death wobble
Reply #28 - 11/04/16 at 15:57:16

Steve H wrote on 11/04/16 at 07:09:25:

You mean to tell me the swingarm is mounted on rubber bushings?

What idiot thought up that one?

Norton did it with the commando. Engine/transmission/final drive were all rubber mounted together to isolate vibration from the frame. Difference is, Norton understood how to build a fine handling motorbike so they got it right.

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oldNslow

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Re: Death wobble
Reply #29 - 11/04/16 at 16:21:19

Quote:

I'm not so sure about that. Using the same site, the frame assembly fiche doesn't show any swingarm attachment features, but the transmission housing looks like it might. The Sportsters are probably different.

I think you're right. On that model it looks like the transmission is bolted to the back of the frame and the swingarm pivot shaft passes through the back of the transmission case.

Interestingly. the bike that went out of control at low speed, the one that belonged to The guy named Costa, in the news report, was a Road King, which does have a swingarm pivot shaft that is attached to the frame. Kind of an unusual arrangement though. It has rubber bushings in the brackets that bolt to the frame that the shaft passes through. There are a lot of fasteners there to potentially come loose.

http://partsfinder.onlinemicrofiche.com/ronnies/showmodel.asp?Type=13&make=hd...

The policeman in the news article that crashed and died was on an Electra Glide. Same arrangement as the Road King.

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