Landracing Forum
Bonneville Motorcycle Speed Trials => Bville Motorcycle Speed Trials General Chat => Topic started by: Uncle Jimbo on November 10, 2013, 01:31:42 PM
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Trevor Lyons started riding when he was just 8 years old. He has race motocross and hairscambles over the years. Now 26 and a 4x land speed record holder shows his skills at the BUB Motorcycle Speed Trials on the Bonneville Salt flats where he handled a 160 MPH high speed wobble as he entered the measured mile at top speed on his Lloydz Motor Workz V-Twin.
Tevor and his boss Lloyd Greer along with Klock Works Laura and Brian Klock work with at risk kids with there "Helping with Horsepower" program. More on that in future videos.
Watch how Trevor handles a 160 + MPH wobble.
http://youtu.be/n7kIUzs1AR0
Please like this video on YouTube and share it, thanks.
Thanks Brother Lou for sharing
Jimbo :cheers:
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That will wake up the old pucker factor.
The problem with HSWs, is most of the time your not sure what started it, or just what gets it started.
Most of the time you come through it and not know what stopped it, just glad it stopped.
Glad he stead up on two wheels this time.
Rouse
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Trevor kindly tell us about your chassis. That was one rodeo ride, and am glad you rolled away with it and stayed upright.
Nice goin ! :-o
Makes me wonder what started it too Rouse ? I did notice a couple engine misfire/caughs at the start of it. Do you suppose the interruption in the power flow to the real wheel could have started an oscillation ? I know there are a lot of guys here at Landracing wayyy smarter then I when it comes to something like this. I hope some of em will weigh in on this. :cheers:
In 09 I had a eye opening shake on the Iron Ghost, turned out I reduced the trail numbers when I shortened the front end.
I wound up adding 5 deg. to the steering head and went back to the stock length forks and problem solved. 40 yr.old. Iron Head Sportster 147 mph
Jimbo
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Been there a few times. Like Rouse says, it eventually stops.
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Trevor kindly tell us about your chassis. That was one rodeo ride, and am glad you rolled away with it and stayed upright.
Nice goin ! :-o
Makes me wonder what started it too Rouse ? I did notice a couple engine misfire/caughs at the start of it. Do you suppose the interruption in the power flow to the real wheel could have started an oscillation ?
Jimbo
I can tell you that can do it. Once, I was running The Texas Mile and got to the finish line and just chopped the throttle with out pulling the clutch,, only ONCE. I nearly ran out of shutdown room before things settled down. That told me not to engine brake that bike again.. Period!!! (and there is not a caveat behind that Period!!!)
Rake and trail are very important factors * note * do not go fast on a V Rod without fixing the R&T, they are set up to look cool, not run fast.
Another thing is front wheel RPM vs. Rear wheel RPM, if that gets to far out (ie. rear wheel to fast or slow) you can have big problems. The wheel speeds needs to be within a certain % of each other or wobble will start, even if every thing else is right. A larger tire diameter on the rear will allow for more tire spin, as it works both sides of that % +/-.
Rouse
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Geez.
good for keeping it upright.
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i usually chop/roll off throttle, no clutch etc...and it has always slowed down in stable manner...
...it seems most of this stuff is variable
from system to system ie veh to veh...
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take my hat off to the young fella for riding that one out,,
i have found that the only way to diminsh a tank slapper/wobble is to keep on the throttle while easing on the rear brake, pulls them out nice and straight,, also helps if you have a rear tire go flat,,
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Speed wobbles were routine when we raced big Jap bikes in the 70's. Gradually it went away when the manufacturers paid attention to rigidity in the upper fork tubes, steering stem, and the frame around the steering head.
The triumph was a bad wobbler and I looked at this. The frame was nice and rigid. The forks, not so. Some gorilla strength triple clamps were made along with some thicker walled upper fork tubes.
Another thing I did was to install some flat track triple clamps with inserts. They could be changed and installed forwards or backwards to vary the offset distance between the steering stem and the fork tubes. The bike was almost unrideable with the larger offsets. It wanted to wobble in a bad way. A bit of futzing around showed me the ideal offset for high speed stability and I used that for the new clamps. The offset was reduced quite a bit to get it stable.
The bike in the video is a partial streamliner and the added fairing and tail weight makes it extra important to pay attention to the things mentioned in the previous paragraphs.
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As humans, I think we have the instinct to over correct in a speed wobble which makes the situation worse. When I took the high performance riding school (road racing school) about a dozen years ago, they taught us to relax our grip on the bars and squeeze the knees for best handling and to minimize speed wobble. Also reduces arm pump.
On my CB350 road race bike, I used later model triple clamps from a 550 with reduced offset (forks to stem), and the dang thing liked not to go around corners at all! I think Honda made them that way for better straight line higher speed handling. When you reduce the offset you increase the trail, which is a good thing for LSR bkes. I used this concept along with extremely stiff (1-1/2" thick lower, 1" upper) triple clamps with just 40mm offset compared to 65mm for the stock CB350 triple clamps on my A class bike. I've only got to 145 mph so far, but no sign of a wobble. However, I have experienced a slow weave if I don't keep my head down at speeds over 100 mph. And remember not to pick the head back up until the bikes slows down below 100 as well. Also got that weave when I had a bias ply rear with a radial front tire.
Tom
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The "good 'ol days" :roll:
http://youtu.be/z3OQTU-kE2s
Tiny
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Thanks for posting that. This is the best thing about landracing.com We can learn stuff to save our butt.
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Great old video! One thing he mentioned was that the slo mo camera showed that each fork leg was compressing independently of the other. I would suggest that a lot of wobble may be eliminated by stiffening up the forks, triple clamps, and probably a larger better connected front axle. Most of the newer bikes already have these features, but the old ones, including those shown in the video, do not. And keep your head down, even when slowing.
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'Bout 40 years ago I worked with a fellow who (in his younger days) was best friends with Dan Blocker. That led to a chance lunchtime visit with an older Hollywood stuntman. He explained that they could make "real nice wobbles" by loosening the front axle nut and the front fender bolts. It allowed lower speed for the wobble, and safer get offs for the crash scenes. It helped to run the right speed on a surface that had some evenly spaced bumps or grooves to get it working for you.
None of us knew anything about "gyroscopic precession" in those days, I bet. Now you can learn all about it on the internet. You only have to be able to tilt that spinning wheel a tiny bit, and it will turn itself into each tilt for you.
So....now we all take off the braced front fenders and go real fast. Add some extra rake, along with too soft front springs and no travel limit....hmmmm.
JimL
PS: for the last 3 years, I've been running schedule 40 PVC or ABS (slotted and hose clamped) on my forks. With travel limited to about 1/2" under power (and zero on decel) the front end stays planted. I actually learned this by accident, when I was curing too much front end lift by closing down the fairing opening above the front fender and adding forward weight. I was trying to protect my paint on the top of the front fender, and the bike suddenly became more stable. The older I get, the slower I learn. :-P
You can see it in this pic, on right edge....shown with no front wheel at full extension.
http://www.landracing.com/forum/index.php?action=dlattach;topic=12670.0;attach=40505;image
If you do this, be sure to pull them off and clean/oil the tube during cleanup. I cut about a 3/4" wide slice out of the ABS or PVC so they will snap in place to hose clamp....no need to disassemble the forks to install or adjust.
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It should be noted that all "speed wobbles" are not caused by the front end.....did the wobble occur at accel...decal... even throttle....wheel alignment...swing arm mounting....rear tire pressure.....too much engine power for the chassis/frame being used....can also be a cause for wobble....even the rider position on the bike (front end loading or not) One needs to look at all these factors in order to resolve a "wobble" problem...............................................
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You want to talk about a "wobble" back in the 1970's I got to ride on the salt on a very fast Vincent that had the old style Hampton girder front forks....at about 130mph it got in a wobble that was out of hand and I was looking for a soft spot on the salt to land.....the only thing that prevented a "get off" was to accel. and drag the rear brake to bring the speed down to below 100mph.....................we parked the bike and made a show piece out of it......................
PS. The later style Vincent front forks worked just great as proven by Marty Dickerson.
With above noted that the Vincent chassis/frame is very solid, in our case it was the front forks.
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Minor correction, the old girder forks used on Vincents are Brampton forks, not Hampton.
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Most of these wobble cures involve some sort of personal effort. Tiny's movie says fat guy's do not have the problem. Tonight it is time for a few burgers, lots of fries, and a big bottle of beer.
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Most of these wobble cures involve some sort of personal effort. Tiny's movie says fat guy's do not have the problem. Tonight it is time for a few burgers, lots of fries, and a big bottle of beer.
:-D :-D :-D :-D :-D , and I thought it was just because I have'nt been over 78 mph yet ?
I had to sacrifice 2 Kangaroo hides to fit my burgers, fries & beer into the leathers
Things will change next year, 'cos my not so friendly leather man refuses to work on my megga thick leathers any more, nope, not a diet, MORE cubettes :-D :-D :-D :-D :-D
Bring on the wobbles :cheers:
Tiny
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Hampton and/or Brampton front forks......I do know that they are not very good at any speed over 35mph. As noted in the previous post the bike is still just a show piece.....but boy, it does look good....................
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Rollie Free set the bathing suit 150MPH record with Brampton girder forks.
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This is what it looks like when it all goes wrong. El Mirage 1998
http://www.youtube.com/watch?v=XTfKJFrUi9w (http://www.youtube.com/watch?v=XTfKJFrUi9w)
Please make the distinction between a speed wobble that this starts out as, and a tank slapper, that it finishes with. They are definitely different animals.
Main point? Notice that the moment he lets go, the bike straightens up and goes as straight as an arrow. And goes, and goes.
No such luck the second time. Instant tank slapper and spit him off.
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I had the pleasure of spending some time with Rollie Free (Thru my sidecar racing partner Mike Parti) and I knew he was a better man than me already at that time.......................
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Indeed. Thanks for your contribution in getting Mike into the AMA Hall of Fame. The three of them, Rollie, Marty, and Mike, are a source of tremendous pride to those of us in the So Cal Vincent club. Mike is my go to guy when I need some machining work on my bikes.
Every few years, in September, a bunch of us get together with Mike and sit under the tree in his back garden, for an anniversary of Rollie's first record run. Mike has quite a bit of Rollie memorabilia, and Mike's scrap books also have quite a bit of space featuring you, and rightly so.