Author Topic: Guy Martin - Triumph Rocket Streamliner  (Read 41077 times)

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Offline joea

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Re: Guy Martin - Triumph Rocket Streamliner
« Reply #45 on: October 14, 2016, 11:23:58 PM »
I'm not telling you ..I posted the video so it could speak for itself ...it shows July runs ..the 271 run reasoning behind handling (track ) then speaks of running many weeks later and new footage and mishaps from sept

I made the mention that st shootout course was yet smoother than many weeks earlier when they went 271...

only as fodder following an earlier thought posted that it seemed course/ rider experience culprit over any inherent issues with vehicle itself

Just observations ...

Offline wobblywalrus

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Re: Guy Martin - Triumph Rocket Streamliner
« Reply #46 on: October 15, 2016, 12:19:57 AM »
That is a weave and different than a speed wobble.  A wobble is much higher frequency and the instability is the wheel flopping around  in a harmonic imbalance.  It looks like the wheel is steady in this video and the harmonic imbalance is in the steering mechanism.

Offline dw230

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Re: Guy Martin - Triumph Rocket Streamliner
« Reply #47 on: October 15, 2016, 11:01:57 AM »
No steering wheel as commonly known. The bike uses joy sticks and it looks like Guy braces his hands against his knees to steady the bike.

DW
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Offline RansomT

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Re: Guy Martin - Triumph Rocket Streamliner
« Reply #48 on: October 15, 2016, 11:07:36 AM »
That is a weave and different than a speed wobble.  A wobble is much higher frequency and the instability is the wheel flopping around  in a harmonic imbalance.  It looks like the wheel is steady in this video and the harmonic imbalance is in the steering mechanism.

Could be the center of gravity of the bike is pushed back too far.  The next harmonic may occur at about 294 mph.

Offline wobblywalrus

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Re: Guy Martin - Triumph Rocket Streamliner
« Reply #49 on: October 15, 2016, 10:15:02 PM »
That is what I think, too.  Some lead placed near the steering stem calms my bike down when it starts the weave.

Online kiwi belly tank

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Re: Guy Martin - Triumph Rocket Streamliner
« Reply #50 on: October 16, 2016, 02:50:53 AM »
You can't think in terms of a ride on bike when it comes to a bike liner because there is no rider weight shift, just like you can't treat a four wheel liner like a door slammer. Take another look at the video as he changes direction to go to his pit, that steering is too fast even for a four wheel liner.
Simply going through a ground thermal or a short cross wind could start off the right-left-right weave & the over correction compounds the situation. It was an accident looking for somewhere to happen when he had the foresight to shove his knees in it. Steering being too fast has got a lot of people into trouble with four wheelers on the salt but they usually just become spin clubbers.
  Sid. 

Offline maj

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Re: Guy Martin - Triumph Rocket Streamliner
« Reply #51 on: October 16, 2016, 03:58:07 PM »
Sid you could be correct , but a sit on rider is not shifting weight much if at all at speed , personally i am gripping the tank with knees and elbows , still able to move my shoulders and upper body a little ,i think at this point the riders of both sorts of bike are not necessarily exactly the same but still similar , and that motion looks very familiar
i have had it when the front was lowered too much and contacted the front fairing on the fender slowing the steering like an overactive damper ,(Not the same sort of slowing steering that could help )
 also with all the weight i carry i am often battling with a weight imbalance and this is 3 dimensional  height of your COG matters more than most think .

On good hard salt you will not know you have a problem,but damp or soft salt, a dust devil or x wind will set it off
My feeling like the other riders is its primarily a weight placement issue, maybe compounded by steering control 

Offline wobblywalrus

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Re: Guy Martin - Triumph Rocket Streamliner
« Reply #52 on: October 16, 2016, 05:13:27 PM »
Sid, on a normal bike we can slow the steering by increasing the trail.  Our steering is at a 1:1 ratio and it is sorta hard to change.  It seems like there are two options on the triumph liner.  One is to change the steering ratio be linkage change and the other is to increase trail.  Any thoughts on this?

Online kiwi belly tank

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Re: Guy Martin - Triumph Rocket Streamliner
« Reply #53 on: October 16, 2016, 05:59:26 PM »
 I would expect it would be a lot less work to try a ratio change with steering arms, even multiple position holes to tailor the feel for the driver rather that saying this is it, learn to like it.
  Sid.

Offline Koncretekid

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Re: Guy Martin - Triumph Rocket Streamliner
« Reply #54 on: October 16, 2016, 11:22:53 PM »
I think that weave can also be caused by steering bearings which are set too tight or a steering damper that is set too tight (I believe a small amount of free movement is beneficial).  A bike that is well designed and set up correctly will naturally want to go straight.  But either of the above conditions can cause the rider to have to force the bike into a straight line and may cause him to overcorrect due to the resistance of the steering components, setting up an oscillation.
Tom
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Offline RidgeRunner

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Re: Guy Martin - Triumph Rocket Streamliner
« Reply #55 on: October 17, 2016, 06:28:48 AM »
I think that weave can also be caused by steering bearings which are set too tight or a steering damper that is set too tight (I believe a small amount of free movement is beneficial).  A bike that is well designed and set up correctly will naturally want to go straight.  But either of the above conditions can cause the rider to have to force the bike into a straight line and may cause him to overcorrect due to the resistance of the steering components, setting up an oscillation.
Tom
[/quote

     A slow weave problem developed for me years ago after I had the front end of a street bike apart, readjusting the old style friction steering damper didn't help.  Loosened up the adjustment just a tad on the steering head bearings [non caged balls in race type], reset the damper, and the problem went away with no other changes.

              Ed

Offline TheBaron

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Re: Guy Martin - Triumph Rocket Streamliner
« Reply #56 on: October 17, 2016, 10:06:40 AM »
Hello All,

I saw this thread and I have some input here as the safety of the rider is so critical with this weave issue

1- everything that has been mentioned is valid ( too quick steering, not enough trail, CG and CP too close together, etc).

2- I would love to see the weather conditions for all the runs as pertaining to winds,,,,  no other vehicle I know of has greater sensitivity to "Yaw Input" than a two wheel motorcycle streamliner....

                          The steering head bearings can be thought of as a "hinge" in the chassis in the lateral direction.

                          Any crosswind, whatsoever, will create an aerodynamic/mechanical instability that can build with speed until it equals,,,
                          thens exceeds the natural stability of the rolling chassis.  Aircraft can swing their nose into the wind and "Crab"
                          forward, as they are a free body in a fluid medium, whereas tires in contact with the ground prevent doing this
                          in a ground vehicle....

                          I would have your team member aero specialist look at this ......

3- Do you 100% know for a fact the natural frequency of the chassis, and are you monitoring the vibrations in the chassis with your data acquiring system???
         
                         I have a simple method for finding the natural frequency, that works for any vehicle, if you would like to try it...

Good luck and be safe,
Robert "Smitty" Smith
Former Air Racing Crew Chief


 
 

Offline grumm441

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Re:
« Reply #57 on: October 18, 2016, 04:35:22 AM »
Not wearing gloves?  Strange...

I saw 273 on the dash
That doesn't make it a record
However, where are his gloves
I don't care if he's just doing a test run, he is supposed to wear his safety gear
G
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Offline TrickyDicky

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Re: Guy Martin - Triumph Rocket Streamliner
« Reply #58 on: October 18, 2016, 05:52:19 AM »
Not wearing gloves?  Strange...

I saw 273 on the dash
That doesn't make it a record
However, where are his gloves
I don't care if he's just doing a test run, he is supposed to wear his safety gear
G

The event in question was private time for testing.  It might be good practice to wear gloves at all times, but as far as I know there is nothing that says he has to.

As Malcolm UK pointed out, when the filming moves to the Shootout he is seen putting on gloves and tethers to reduce the amount his wrists/arms can move around.  He also changed to a higher spec helmet.

As someone who has raced and crashed on the Isle of Man, Guy Martin's attitude to risk may be different to most people's.

Offline Frank06

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Re:
« Reply #59 on: October 18, 2016, 08:11:26 AM »
@thebarron: can you post about your method of determining natural frequency?  I would be interested as I have experienced weaving on a stretched drag bike

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