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Message started by verslagen1 on 11/02/16 at 19:40:37

Title: Death wobble
Post by verslagen1 on 11/02/16 at 19:40:37

http://speedandengines.com/2016/04/05/cbs-5-investigates-harley-motorcycles-known-for-death-wobble/

Title: Re: Death wobble
Post by MMRanch on 11/02/16 at 21:11:19

Those big Harleys ain't right anyway . ;D I also suspect there is something wrong with anybody who would spend $20,000 + on a Cheep-Transportation-Vehicle .

It seem like Harley would balance there motors better so they didn't need "Super-Soft" rubber mounts to keep the motors in the frames.

That being said : I haven't found any major flaws with the 883 (2007) Sportster yet. One of my brothers got a "solid-mounted-motor" 1200 sportster (1994 all chopped out looking) last summer. I rode it a few miles two weeks ago --- , it reminded me of a 1972 BSA I rode last spring , vibrated more than a little. ::)

:)

Title: Re: Death wobble
Post by justin_o_guy2 on 11/02/16 at 21:16:11

Rumor and innuendo..

Title: Re: Death wobble
Post by oldNslow on 11/02/16 at 21:56:17

Easily seventy five or eighty percent of the bikes I encounter out on the road are Harleys, a lot of them big twins with big fairings, bags, trunks etc. How come all those guys aren't dead or in the hospital?

Local CBS affiliate someplace. I taking this one with a pretty large grain of skepticism I'm afraid,

Title: Re: Death wobble
Post by verslagen1 on 11/02/16 at 22:46:49

Oscillations like that occur with certain frame spring rates.
could be mfg tolerances, could be certain mods.
As someone with a modified bike, I prefer to be informed.
You can put your head in the sand if you wish.

Title: Re: Death wobble
Post by justin_o_guy2 on 11/03/16 at 04:17:13

I've seen a stretch of road that scares me. No visible marks on the road. Nothing that I can see that would make it shake, but it was exciting and unfunny, I THINK it was that way coming and going, both trips.. so, I have a hard time condemning the windshield as catching a breeze,,

When you have Documented Evidence of the Fact that the HD is misbehaving, better to find out why.
The 05 without any windshield, and shocks set up tight acted like a drunk rubber cow on a local sweeper..
I have not tried a full on assault with the 02.
Just got the new Metzler rear tire in yesterday, now, gotta get it ON.

Title: Re: Death wobble
Post by Dave on 11/03/16 at 05:00:32

They got videos on YouTube.

https://www.youtube.com/watch?v=Gmw6QppXnEY

[media]http://www.youtube.com/watch?v=Gmw6QppXnEY[/media]

https://www.youtube.com/watch?v=Qs8o9-sqU2c
[media]http://www.youtube.com/watch?v=Qs8o9-sqU2c[/media]

https://www.youtube.com/watch?v=yvDI2dmzDEA
[media]http://www.youtube.com/watch?v=yvDI2dmzDEA[/media]

Title: Re: Death wobble
Post by Drestakil on 11/03/16 at 05:07:57

This is the first I've heard of it. Never had much desire for a big Harley before and even less likely to end up with one now. A Sportster would be nice but I still prefer smaller lighter bikes.

Title: Re: Death wobble
Post by justin_o_guy2 on 11/03/16 at 05:50:55

I'm gonna be studying the windshield and make sure it's setup as square to the frame as possible.
Maybe the Metzlers will calm it down.
I'm pretty sure the bags are not hitting the wind with symmetry.
The shocks are set on the softest setting.
It's gotten a bit scary a few times.. And I was running traffic speeds.

Title: Re: Death wobble
Post by Dave on 11/03/16 at 06:01:58

Jog:

One fellow on the forum mounted a tool roll under his headlamp, and it caused his bike to wobble at speed.

I haven't read that any of our folks have had problems with their windshield causing a problem - but I can believe it is possible.

The road I was riding on last Sunday had several patched areas in the asphalt....and it appears that they drove a backhoe on the patches and it imprinted the tractor tread into the asphalt. That created some spooky vibrations while I was leaned over in a few corners!

Title: Re: Death wobble
Post by justin_o_guy2 on 11/03/16 at 06:13:49

Thanks for the input. I have a fanny pack on top of the light, and the windshield gap at the light isn't exactly symmetrical, or real small, so, after the tires are on, if it's still twitchy, I'll be looking..

Title: Re: Death wobble
Post by oldNslow on 11/03/16 at 06:42:42

Aint just Harleys:

http://hondaf6b.com/showthread.php?2134-Does-Anyone-Have-Front-Wheel-Wobble

Reading through the thread, a lot of this is just the usual MC forum bickering but the issue has been around on GWs for a while, with all sorts of opinions as to cause and cure.

Here's one that focuses on HDs:

http://ridermagazine.com/2009/11/17/motorcycle-weaves-and-wobbles-how-to-avoid-them-and-deal-with-them/

ANY motorcycle (or bicycle for that matter) is susceptible to headshake or weave under the right combination of speed, rider input, suspension, road surface, weight distribution, mechanical condition etc.

I rode a buddy's beat-to-sh*t CB 750 years ago that started a high speed weave at about 70 that could only be controlled by laying down on the tank and gently rolling off the throttle. We never did figure out why it did that. That bike was entirely stock, and when I rode it at least, had nothing tied, strapped, or bolted to it anywhere.

I still think the the CBS story was basically just a hatched job.

Title: Re: Death wobble
Post by mpescatori on 11/03/16 at 07:13:47

My two cents.

Harley Davidson make mediocre motorcycles with lousy frames but package it all into such a beautiful looking (and sounding) item it sells like hotcakes.

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.
:-?
Yep !
They only had to buy a 1950's brit bike and copy the frame, but no, they had to go their own way
and improve a 1920's design to the point you just can't improve it any more... and this is what you get.

Death wobble.

Look at the three Youtube videos posted a while up the thread.
Ask yourselves... would you buy a car whose rear axle was not bolted to the chassis but to ... whatever else ?

:P

BTW My other bike is a Dyna... ;D

Title: Re: Death wobble
Post by engineer on 11/03/16 at 07:44:27

Weaves and the more violent head shaking has been well documented and filmed since at least the 50s. Some models seem to be more prone than others, like the short wheelbase BMW R60/5s & R75/5s in the early 70s. BMW lengthened the swing arm after a couple years and solved the problem but many are skeptical and believe it was never a problem. I recently bought an early short wheelbase /5 toaster tank and am in the slow process of restoring it. When I get it on the road next summer I guess I will find out if it shakes or not.

Title: Re: Death wobble
Post by oldNslow 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.

Title: Re: Death wobble
Post by HAPPYDAN on 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!

Title: Re: Death wobble
Post by justin_o_guy2 on 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..

Title: Re: Death wobble
Post by Ruttly on 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!!!!'

Title: Re: Death wobble
Post by Dave on 11/03/16 at 10:52:42

0D2A2B2B33265F0 wrote:

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

[media]http://www.youtube.com/watch?v=XiKmPFo6xNA[/media]

Title: Re: Death wobble
Post by justin_o_guy2 on 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..

Title: Re: Death wobble
Post by Ruttly on 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

Title: Re: Death wobble
Post by Ruttly on 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 !!!

Title: Re: Death wobble
Post by Ruttly on 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 ! ;D

Title: Re: Death wobble
Post by Nigel-in-SoCal on 11/03/16 at 22:35:57

0C32333F2D31305E0 wrote:

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]

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.

Title: Re: Death wobble
Post by Steve H 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?

Title: Re: Death wobble
Post by oldNslow on 11/04/16 at 09:45:32

5249101312151718210 wrote:

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=hdmc&a=646&b=32&c=0&d=2007%20FXDB%20DYNA%AE%20STREET%20BOB%AE%20(GX)%20SUSPENSION%20-%20SWING%20ARM%20W/%20BELT%20GUARD%20AND%20DEBRIS%20DEFLECTOR

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.

Title: Re: Death wobble
Post by Nigel-in-SoCal on 11/04/16 at 14:13:35

6E50515D4F53523C0 wrote:

[quote author=5249101312151718210 link=1478140837/15#24 date=1478268565]You mean to tell me the swingarm is mounted on rubber bushings?

What idiot thought up that one?

Title: Re: Death wobble
Post by verslagen1 on 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.

Title: Re: Death wobble
Post by gizzo on 11/04/16 at 15:57:16

2D366F6C6D6A68675E0 wrote:

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.

Title: Re: Death wobble
Post by oldNslow on 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=hdmc&a=780&b=36&c=0&d=2010%20FLHRC%20ROAD%20KING%AE%20CLASSIC%20(FR)%20FRAME%20ASSEMBLY%20-%20REAR%20W/%20REAR%20FORK%20AND%20LUGGAGE%20RACK

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

Title: Re: Death wobble
Post by mpescatori on 11/07/16 at 05:31:35

27202E2C252B283B222C3B490 wrote:

[quote author=0C32333F2D31305E0 link=1478140837/0#14 date=1478185112]
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]

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.[/quote]

I think somebody saw wrong...

http://https://upload.wikimedia.org/wikipedia/commons/thumb/3/3b/Ducati_1199_Superleggera_%2810760579253%29.jpg/1280px-Ducati_1199_Superleggera_%2810760579253%29.jpg

That big fat triangular thing is the fuel tank, designed to act as part of the frame.
NOWHERE does it say that the steering stem and swingarm are bolted to the engine.
I personally had a Ducati 450, the biggest single Ducati ever made [library pic]
As you can see from this picture, the downtube of the frame connects to the engine case... certainly NOT to the head!

http://https://upload.wikimedia.org/wikipedia/commons/thumb/e/e7/Ducati_Motorcycle.JPG/1280px-Ducati_Motorcycle.JPG

Furthermore, Ducati twins have the front cylinder flat horizontal, and the rear downright vertical BUT at the rear of the engine.
So there is no way you can attach the steering stem to the vertical (rear) cylinder.
Also, the rear swingarm is bolted on the apex of the upside-down triangle under the seat - a design copied by Willie Davidson 30 years later when he came up with the FXR.

::)

Actually, yes... the last time I testo rode a Panigale it did have a little bit of wobble... but then I was doing 205mph !!! :D

http://youmedia.fanpage.it/video/ad/VAnePOSwHTKu10U1

Title: Re: Death wobble
Post by Ruttly on 11/07/16 at 06:40:29

Yes Harley rubber mounts their engines
That video looks like that Harley came out of a Jello mold
Would never own any bike that handles like that

Title: Re: Death wobble
Post by gizzo on 11/07/16 at 06:52:37

Belt drive ducatis have the swingarm pivot in the back of the crankcase. But a normal steering head arrangement. The paralever BMW's are an example of a motorbike with no frame: everything hangs off the engine. They handle pretty ok. Never ridden a panigale and probs never will. That must have been some kind of fun.

Title: Re: Death wobble
Post by oldNslow on 11/07/16 at 07:01:01

Quote:

Gone is the traditional Ducati trellis frame that usually wraps around the engine. The Panigale is famously the first production bike to abandon an ordinary frame altogether. One chunky piece up front joins the main front end headstem bearing races to the top radiator and the front and rear cylinder heads.
A pair of boomerang-shaped supports hold the seat and tail unit up off the engine's rear cylinder, and a similar boomerang shaped mount hangs the swingarm off the crankcase. The rear shock sits slightly beyond horizontal, attached to the side of the rear cylinder. The engine doesn't sit in a frame; the engine more or less *is* the frame.

Title: Re: Death wobble
Post by mpescatori on 11/07/16 at 10:35:05

766C686A6B55647771776C616260050 wrote:

I beg to differ.

Up until my accident on 7/17/'15 I had two Beemers, both with telelever front suspension.

I can assure you there was a frame, it's just not your average everyday tube frame.

http://put.edidomus.it/dueruote/news/foto/telaio_gs-1200_2013.jpg

But it handled like a million dollars. Never have I had such a wonderfully Handling bike !

Incidentally, my "Big Blue" scrapes the pegs on full throttle and a full load - 90mph on highway bends on a 800 lb. bike is no easy feat, but I can do it on the Beemer 8-) (again, library pic)

http://media.motorbox.com/cache/images/1/0/6/106449/106449-16x9-lg.jpg

Really ! I believe she is the only fuill dresser on which you can scrape the pegs and NOT fall over !

Title: Re: Death wobble
Post by Ruttly on 11/07/16 at 19:18:59

Looks like "A frame suspension from a car

Title: Re: Death wobble
Post by Kris01 on 11/07/16 at 19:40:40

5F454143427C4D5E585E45484B492C0 wrote:

They called it their Isolastics system. From what I understand, it was hard to adjust properly. But when it was dialed in, it was a well-oiled machine!