(Please visit one of our advertisers)

No donations or subscriptions are required

   OR   
   
Subscription choices:
Board Karma = 40  (3488 positive of 3870 votes is 40 %pts higher than a neutral 50%)
All Things (Safety Oriented) Motorcycle   
Username:
Password:
Save Password
Forgot your Password?

You can the entire collection of Safety Tip articles in a 33 Megabyte PDF Portfolio

 All Forums
 Motorcycle Safety
 Physics and the theoretical
 To accelerate or remain constant, that is the question
Previous Page | Next Page
Member Previous Topic Discussion Topic Next Topic
Page: of 6

rayg50
Male Moderator
2082 Posts
[Mentor]


NYC, NY
USA

Honda

Shadow Spirit 750DC

Posted - 06/19/2011 :  8:32 AM
Cheers Rob, given the time difference and the fact that it is a weekend I am not expecting a reply to my first challenge any time soon. Quite frankly I do not believe I have anything to add to my position. What I like about this board is that both sides can lay out their supporting arguments and allow the readers to decide for themselves.

quote:
Originally posted by Robsalvv
One of them is right. It's that simple. This is not an apples and oranges thing. It's a science thing.


So let us move on to the science thing, my second challenge. Let's not repeat the mistake of the first one by not coming to some basic agreements before making our points. Rob, Mr. Davis, all others, here is the first part upon which my challenge will be based. Please correct any of the points below. If I am beginning with a false assumption then I may need to adjust or withdraw my challenge.

1- Adding weight to a tire will increase it's traction. Reducing weight from the tire will decrease it's traction.
2- Accelerating will shift weight from the front tire to the rear tire.
3- Deceleration will shift weight from the rear tire to the front tire.
4- Prior to entering a turn, while travelling in a straight line at a steady speed there is a fixed amount of traction and traction reserve.
5- As you begin to turn there is an increase in traction demand and therefore a reduction in traction reserve.
6- The greatest traction demand and therefore the least amount of traction reserve is at the sharpest point in the BIKES turn which I would call the BIKES apex.
7- Once past the bikes apex the process reverses. Traction demand decreases and reserve increases until the bike is once again travelling in a straight line.

I invite not just Rob but anyone to clarify my thinking. The above analysis is the basis of my contrary position. If any of the above is incorrect then I must go back to the drawing board.

Actually the basis for my disagreement is a second part that I will post after we have reached agreement on the above. The second part is a widely accepted theory so I do not see it being refuted but will be offered for review and comment as a preface to my actual challenge.

Thanks,
Ray

Edited to add one last point for agreement.

8- Constant speed causes no shift in weight either forward or back.


Edited by - rayg50 on 06/19/2011 11:07 AM
Go to Top of Page

(Deleted or Lost)

Posted - 06/19/2011 :  12:21 PM
quote:
Originally posted by James R. Davis

When a discussion becomes a discussion of and critiques of the information presented by only one side of that discussion, where no new information is contributed, it is merely a critique. When you offer information in support of your opinion, I'll be happy to reengage.

Does maintaining constant speed or increasing speed result in the highest amount of 'stability' in a turn? Why?


Stability was not my term James. I've agreed with you that a constant radius constant speed turn by definition must be stable - and must be more stable than an accelerating turn which is continuously changing direction. You showed that to be the case.

The roadcraft book links stability and grip. Grip = traction. It says stability and grip are maximised in a constant speed turn.

The motorcycling world instead argues that grip, stability, handling or some other illdefined term is maximised by increasing acceleration in a corner. You've stated as much too, using the words "handling stability".

I asked the question are the two concepts correct and can they live side by side? That hasn't been answered yet.

I genuinely want to understand, hence my tenacity - because I am indeed picking up inconsistencies in your words which I hope you would want to resolve for your own benefit. I've read many times where you ask for exacting intellectual honesty and clarity of expression on these forums. This is not a critiquing exercise. It's not about winning. It's about understanding... and if that understanding isn't going to come from msgroups.org, then frankly, it's unlikely to come from anywhere.



Go to Top of Page

gymnast
Moderator
4260 Posts
[Mentor]


Meridian, Idaho
USA

Harley-Davidson

Sportster Sport

Posted - 06/19/2011 :  12:37 PM
The employment of sophistry rarely improves ones ability to make their motorcycle go where one wants it to go in the manner that one wants to make it go. I generally ascribe to careful use of the throttle when one is maneuvering on thin ice or in a curve when approaching the limits of traction.

Go to Top of Page

(Deleted or Lost)

Posted - 06/19/2011 :  12:58 PM
quote:
Originally posted by rayg50

quote:
Cheers Ray, just so long as your thought processes have placed the "opposing" technique in the right light! It's always good to test what you take forgranted and if that testing confirms it's validity, then all the better.
Cheers Rob, I am hoping that you will help in putting the technique in the right light.

My current challenge centers on the claim of added safety. I gave you a scenario to which your response was
quote:
So those two riders of yours entering a corner at a near maximum available traction speed... well, they'd be going in pretty darn fast! I suspect they'll have a few other issues to deal with - accelerating through the turn will be their last priority!
Which I interpret as "they shouldn't do that". So I will pose my question differently. How can a technique that has a higher possibility of failure be the safer technique?




Actually Ray, those two riders will do whatever they want and it's likely they will crash if they enter at a speed that demands near maximum available traction. IMO they've already messed up the corner - it's a public road for goodness sake. But just say they enter and make it stick, the accelerating rider is very likely to start getting signs that the rear tyre is about to let go (acceleration provides some oversteer - another positive benefit of the technique). If such a rider was capable enough to enter a corner at such speed and make it stick (i.e., not freak out and become overwhelmed by survival reactions), we must assume he/she is capable and will know to stop rolling on the throttle at the first signs... otherwise, they will crash.

Let's not forget, this is about modest acceleration ~0.1G. The two riders entering the same constant radius sweeper at the same speed will exit with two different speeds... the difference will be an increase of 1m/s per second of time in the corner (assuming instant roll on after tip in). What's the probability increase of that technique being more dangerous?

The context of the technique being IMO safer was in relation to entering a corner with a speed that allows acceleration, in conjuction with a wide entry point which maximise sight lines, in conjunction with increased rear wheel traction from the weight transfer and in conjunction with a more compliant suspension - at the very least a partly unloaded front end which gives it more chance to deal with lumps and bumps while leaned over. So any perceived increase in the probability of failure/danger due to a marginally increased speed I think is more than balanced by the advantages offered.

In comparison, the constant radius, constant speed, highly stable approach is a conservative and safe approach that doesn't have the maximised sight lines, traction or handling benefits - but has other advantages that I highlighted in an earlier post. In particular, if one enters with a speed that one can stop safely within the distance seen to be clear, it's very likely that this speed will not demand a high percentage of the available traction.

Go to Top of Page

(Deleted or Lost)

Posted - 06/19/2011 :  1:09 PM
quote:
Originally posted by rayg50

Cheers Rob, given the time difference and the fact that it is a weekend I am not expecting a reply to my first challenge any time soon. Quite frankly I do not believe I have anything to add to my position. What I like about this board is that both sides can lay out their supporting arguments and allow the readers to decide for themselves.

quote:
Originally posted by Robsalvv
One of them is right. It's that simple. This is not an apples and oranges thing. It's a science thing.


So let us move on to the science thing, my second challenge. Let's not repeat the mistake of the first one by not coming to some basic agreements before making our points. Rob, Mr. Davis, all others, here is the first part upon which my challenge will be based. Please correct any of the points below. If I am beginning with a false assumption then I may need to adjust or withdraw my challenge.

1- Adding weight to a tire will increase it's traction. Reducing weight from the tire will decrease it's traction.
2- Accelerating will shift weight from the front tire to the rear tire.
3- Deceleration will shift weight from the rear tire to the front tire.
4- Prior to entering a turn, while travelling in a straight line at a steady speed there is a fixed amount of traction and traction reserve.
5- As you begin to turn there is an increase in traction demand and therefore a reduction in traction reserve.
6- The greatest traction demand and therefore the least amount of traction reserve is at the sharpest point in the BIKES turn which I would call the BIKES apex.
7- Once past the bikes apex the process reverses. Traction demand decreases and reserve increases until the bike is once again travelling in a straight line.

I invite not just Rob but anyone to clarify my thinking. The above analysis is the basis of my contrary position. If any of the above is incorrect then I must go back to the drawing board.

Actually the basis for my disagreement is a second part that I will post after we have reached agreement on the above. The second part is a widely accepted theory so I do not see it being refuted but will be offered for review and comment as a preface to my actual challenge.

Thanks,
Ray

Edited to add one last point for agreement.

8- Constant speed causes no shift in weight either forward or back.



I don't sleep much Ray... lol

Point 4 will hold for the corner IF the corner is perfectly flat and has the same road surface. Add a positive camber and there will be a component of cornering forces which increases the weight of the tyres into the pavement and hence increase traction.

Point 6 & 7 don't hold for a constant radius, constant speed cornering approach. There is no apex so to speak.

I agree with all the rest of the points.
Go to Top of Page

(Deleted or Lost)

Posted - 06/19/2011 :  1:13 PM
quote:
Originally posted by gymnast

The employment of sophistry rarely improves ones ability to make their motorcycle go where one wants it to go in the manner that one wants to make it go.



Gymnast, please point out where I have used fallacious arguments or subtly deceptive reasoning in my discussions?
Go to Top of Page

James R. Davis
Male Administrator
17276 Posts
[Mentor]


Houston, TX
USA

Honda

GoldWing 1500

Posted - 06/19/2011 :  1:32 PM Follow poster on Twitter  Join poster on Facebook as Friend  
quote:

The roadcraft book links stability and grip. Grip = traction.

Really? And despite my definitions previously put forth, you persist in thinking of stability as if it's merely traction? Why do you suppose that roadcraft decided it needed a third word for traction? Wasn't 'grip' enough? And while 'grip' is certainly a part of traction, it is not at all the whole story as it lacks the frictional component. (You would agree, I assume, that a steel wheel on a railroad car has traction, but is it from 'grip' or 'friction'?) But if it's close enough for roadcraft, maybe it's good enough for all of us.

Does a bike that is wobbling back and forth along its path of travel constitute something other than 'unstable'?

Is a bike that has twitchy steering something other than 'unstable'?

Would a bike that under-steered 'feel' as stable as a bike that over-steers?

quote:
Add a positive camber and there will be a component of cornering forces which increases the weight of the tyres into the pavement and hence increase traction.

Really? So a bike can brake or accelerate at greater rates with a cambered (banked) slope than on a level surface? Are you sure? Said differently, if a 100 pound tire at rest on a level surface takes 100 pounds of pull to make it start skidding, are you certain that it would take more than 100 pounds of pull to make it start skidding if that surface had a super elevation (slope to the side)? Would the measurements be different if that 100 pound tire was rolling along at 100 MPH in a curved path? (There is no argument that it would be able to handle greater lateral forces on a banked surface, but is that because of 'traction'?) Does the 'added weight' you mentioned mean that the tire weighed more than 100 pounds? (Weight is a measurement relative to the center of the earth, is it not?)

When I get some free time (very precious lately), I will endeavor to smooth out those discrepancies in my articles.
Go to Top of Page

(Deleted or Lost)

Posted - 06/19/2011 :  2:19 PM
Due to nested quotes causing server errors on posting, I've pulled out my quotes and reposted them as italicised text.


I said: The roadcraft book links stability and grip. Grip = traction.
quote:
Originally posted by James R. Davis

Really? And despite my definitions previously put forth, you persist in thinking of stability as if it's merely traction?
No James I don't persist in this thinking. I'm stating that that's what the book says. It says constant speed cornering gives maximum stability. We've agreed that this is the case. The book however equates maximum stability with maximum grip/traction. This tripped up my eye.



quote:
Why do you suppose that roadcraft decided it needed a third word for traction? Wasn't 'grip' enough? And while 'grip' is certainly a part of traction, it is not at all the whole story as it lacks the frictional component. But if it's close enough for roadcraft, maybe it's good enough for all of us.
Well I am here to fathom out the truth of their words. And clearly if modest acceleration increase the traction of the rear wheel and a bike steers from the rear (my extreme paraphrase of tip 66) then the constant speed approach can't both have the most stability and the most traction/grip?



I said: Add a positive camber and there will be a component of cornering forces which increases the weight of the tyres into the pavement and hence increase traction.
quote:
Really? So a bike can brake or accelerate at greater rates with a cambered (banked) slope than on a level surface? Are you sure? Said differently, if a 100 pound tire at rest on a level surface takes 100 pounds of pull to make it start skidding, are you certain that it would take more than 100 pounds of pull to make it start skidding if that surface had a super elevation (slope to the side)?
You and I had another protracted discussion elsewhere on this forum about available/reserve/maximum/total (pick one because we differed about the definitions in that discussion) traction increasing in a curved path on a positively banked corner. I draw my statement from that discussion. If I have recalled that discussion erroneously, I will gladly retract my statement. Otherwise I stand by the statement that in a banked corner, a component of the cornering forces adds weight to the tyres and hence increases the total traction available.



quote:
When I get some free time (very precious lately), I will endeavor to smooth out those discrepancies in my articles.

What discrepancies? I only pointed out a confusing inconsistency in a statement you made in this thread compared to what you stated in multiple tips. Are all those tips wrong now? Can I change tack. You said your book is internally consistent. What does it say on the topic of cornering and throttle control? And why?
Go to Top of Page

James R. Davis
Male Administrator
17276 Posts
[Mentor]


Houston, TX
USA

Honda

GoldWing 1500

Posted - 06/19/2011 :  2:39 PM Follow poster on Twitter  Join poster on Facebook as Friend  
Once again you wish to use my words (extreme paraphrase or not) to prove you are right and I am not.

That article, as it turns out, was really about STABILITY - and pointed out that the rear tire is primarily responsible for MAINTAINING a path of travel while the front tire is used to DESTABILIZE the bike in order to arrive at a new path of travel.

As to what's in my book ... you can buy it and see for yourself. It will fit right next to, on top of, or under, your book on roadcraft. If there are errors or inconsistencies or discrepancies in it, please feel free to share them with us. No doubt the book explains things differently than roadcraft does. Perhaps telling them about those differences would also be in order - perhaps not.
Go to Top of Page

rayg50
Male Moderator
2082 Posts
[Mentor]


NYC, NY
USA

Honda

Shadow Spirit 750DC

Posted - 06/19/2011 :  6:42 PM
Cheers Rob, I just returned from a pleasant ride. We are entering our summer so I have to take advantage of any good days. I assume you are approaching your winter since you are south of the equator.

quote:

RG: 4- Prior to entering a turn, while travelling in a straight line at a steady speed there is a fixed amount of traction and traction reserve.

RS: Point 4 will hold for the corner IF the corner is perfectly flat and has the same road surface.

Did you have a different one other than #4 in mind? I make no reference to cornering. I just wanted to state that no unusual forces were influencing the bike prior to the entry. I actually do not care what the road condition is as long as we can agree that for the purposes of this discussion there is no change in road surface between the curve and the straight approaching it. My focus is on the curve itself which is what I thought was your point of reference when speaking of accelerating rather than maintaining speed.

quote:
Point 6 & 7 don't hold for a constant radius, constant speed cornering approach. There is no apex so to speak.

Which is why I referred to the bikes apex and not the curves. What I am hearing you say is that you do not use any lines in negotiating a curve. You follow the contour of the curve. I assume your use of the word approach was a slip. I want to discuss the dynamics once you are in the curve.

We can always add a couple of points of agreement to cover that situation. I had wanted to limit the variables but I am fine with adding some points of agreement. Please describe the progression of traction change in a constant radius constant speed curve. Unless you say there is no change I will probably agree.

What I am trying to do is set the stage for an honest exchange of ideas. I am intentionally not using any terms other than traction, traction demand, and traction reserve. I am happy to accept whatever definition you would care to assign them. I intentionally spoke of the bikes apex for fear that if I said the curves apex I would find myself in an ever changing list of possible apexes.

I just want to see if what you propose holds water. If it does that is fine. I will have learned something new and any day I learn something new is a good day. So let us agree on the ground rules and move on to the actual disagreement.


Edited to remove some things that serve no real purpose.

Edited by - rayg50 on 06/19/2011 7:08 PM
Go to Top of Page

gymnast
Moderator
4260 Posts
[Mentor]


Meridian, Idaho
USA

Harley-Davidson

Sportster Sport

Posted - 06/19/2011 :  7:55 PM
In order to see if the questions posed in this thread, beginning with the first one posed by "rider 5", having to do with "maintaining throttle position" or "rolling on the throttle" had practical relevance in terms of my usual riding habits I took a ride this afternoon known locally as the "Lowman Loop" The route, on a two lane paved road includes every type of curve that one is ever likely to encounter namely constant, decreasing, and increasing radius curves, as well as on camber, 0 camber, and off camber variations in flat as well as upgrades and downgrades of up to 10%. http://www.google.com/search?q=The+...nt=firefox-a and various U-Tube videos, http://www.google.com/search?q=The+...nt=firefox-a

The bike used for the ride was a 1997 Sportster Sport with modifications to the engine and original unmodified suspension. Tire pressure was 35 lbs front, 40 lbs rear. Temperature ranged from 58 degrees F at 2400 feet at the start of the ride to 40 degrees at 6200 feet going over the passes. I ran the corners at 15 MPH over the signed advisory speeds (when clear of traffic which occasionally did not allow the higher speed)and never came close to dragging a peg. While negotiating the corners I intentionally added, maintained, or chopped the throttle as appropriate to maintaining control for the various cornering configurations as they were encountered. To see if "stability" was significantly affected, in some curves of each type I would add, maintain or chop (reduce) throttle. The ride was done 2 up, with the Missus as passenger. Within the curves described while negotiating the curves at the speed and throttle parameters described, stability was never once significantly effected.

I normally make a practice of riding as smoothly as possible, and normally enter curves "off the brakes" having completed all braking, as appropriate prior to the apex of the curve. Today I made a point of not using the brakes at entry, concentrating on approaching the curve entry at 15 MPH over the speed advisory signage.

Anyone concerned with the subtleties of "upsetting the stability of their bike while in a curve" is likely going far too fast to begin with and needs to do a bit more thinking about the compatibility of their riding habits within the normal parameters of safe and legal operation of their motorcycle. On the other hand it is a good thing to maintain a constant safe speed throughout a curve by the correct use of the throttle (adding, maintaining, or reducing throttle) to maintain an appropriate speed for conditions.

Riders "pushing their ability envelope on the Lowman Loop" http://www.videosurf.com/video/gsxr...ho-138045062

2 cents worth.


Edited by - gymnast on 06/19/2011 8:08 PM
Go to Top of Page

James R. Davis
Male Administrator
17276 Posts
[Mentor]


Houston, TX
USA

Honda

GoldWing 1500

Posted - 06/19/2011 :  9:45 PM Follow poster on Twitter  Join poster on Facebook as Friend  
100% spot on Gymnast.

Despite the technical details, it's the impact on the practical (real-world) riding that counts. If stability is already adequate, what difference does it make if you can make it even less prone to destabilize? As long as nobody thinks that aggressive acceleration in a curve is appropriate except on a race track, what difference in a real-world sense, does it make if you use zero or modest acceleration in that curve?

Thank you.
Go to Top of Page

rayg50
Male Moderator
2082 Posts
[Mentor]


NYC, NY
USA

Honda

Shadow Spirit 750DC

Posted - 06/20/2011 :  6:52 AM
Cheers Rob, while we set the stage for the discussion please elaborate on the following:

quote:
KC's rule number one is: "Once the throttle is cracked on, it is rolled on evenly, smoothly and constantly through the remainder of the turn." - this rolling on is done as soon as possible once the steering input is completed.

While you and I may be miles apart in our perspectives, KC and I may not. Please read post #6 in this thread by Scottrnelson. It describes how I make my turns and what I thought was the prescribed method for negotiating a curve that everyone uses.

Specifically I would like you to tell me at what point in negotiating a curve does he say to begin the acceleration? I don't think that the steering input is ever complete in a curve so I would need to have a better definition of the point at which acceleration begins. Please use the apex as the point of reference. For this particular reply you can consider the apex to be the middle point in the curve where your path of travel reverses direction.


Go to Top of Page

staticattic
Male Senior Member
410 Posts


Tampa, FL
USA

Honda

Shadow Spirit 750

Posted - 06/20/2011 :  12:00 PM
After reading all of this, my brain has popped. I know what my bike "feels" like when executing turns, curves, acceleration, and deceleration. When these threads come up diving this deep into the math and physics behind what's going on, it sometimes gets quite confusing.

One question I have involves coasting. The way I see it, there are 2 different ways to coast; releasing the throttle or pulling in the clutch lever. Releasing the throttle would still use the engine to keep pressure on the drive mechanism, while pulling in the clutch would allow the drive mechanism to totally "free wheel." IRT coasting through a turn or around a corner, would one be worse than the other or is "coasting" coasting no matter what?
Go to Top of Page

rider5
Male Starting Member
4 Posts


Melbourne
Australia

BMW

R1100GS

Posted - 06/20/2011 :  7:31 PM
Jeez - the worms in this can are certainly getting messy. To be honest guys, I'm not qualified to get involved in the science because I only have a laymans knowledge. I teach Roadcraft and believe that it is fundamentally correct for the level of rider I generally teach. By espousing its content I figure I'm on safe ground and that the student who leaves me thinking that a constant speed will in most cases make them safe is more likely to be safe rather than leaving me with the believe that they must accelerate all the way through a bend.

To me the issue is contextual. In the broad sense of day to day riding, my aim is to make good day to day riders because these guys represent the majority. I get the increased traction thing through acceleration incerasing weight, but I teach people to be comfortably within the traction envelope anyway. I teach people to look for the 'limit point' and to understand its significance in deceision making in the same way I teach latish apex cornering in order to maximise vision, options and preparation.

Roadcraft is not, does not attempt to be so definitive it becomes limited, nor is it incorrect. It doesn't actually say constant throttle increases stability and grip, but what it does say is "to get maximum cornering control, avoid altering your road speed at the same time as altering direction."

This goes back to issue of context. Control is highly subjective term, but to me includes 'control' of the machine,the environment and the ability to change my plan.

James I thank you and all the other contributors including my friend RobSalvv. I have learnt from the exchange, but have not changed my opinion regarding roadcraft. It is still the most workable text for my purposes and until something better comes along that meets my requirements of creating better riders, it'll do.
Go to Top of Page

bachman1961
Male Advanced Member
2260 Posts
[Mentor]


colorado springs, co
USA

Honda

CB750 NightHawk

Posted - 06/20/2011 :  8:17 PM
quote:
Originally posted by staticattic

After reading all of this, my brain has popped. I know what my bike "feels" like when executing turns, curves, acceleration, and deceleration. When these threads come up diving this deep into the math and physics behind what's going on, it sometimes gets quite confusing.

One question I have involves coasting. The way I see it, there are 2 different ways to coast; releasing the throttle or pulling in the clutch lever. Releasing the throttle would still use the engine to keep pressure on the drive mechanism, while pulling in the clutch would allow the drive mechanism to totally "free wheel." IRT coasting through a turn or around a corner, would one be worse than the other or is "coasting" coasting no matter what?




I think releasing the throttle, even gently will cause engine braking and no 'coasting' whereas pulling in the clutch 'freewheeling' may slow, speed or remain constant depending on the road grade. Knowing what the bike is doing and having the constant control and feedback makes coasting (IMO) not much of a sensible option.

Road surface conditions that are sketchy or unknown are times I've went 'hands-off' and let the bike coast just bit though.

~brian
Go to Top of Page

Mikeydude
Male Advanced Member
739 Posts
[Mentor]


Ft. Worth, Texas
USA

Harley-Davidson

03 FXD Super Glide

Posted - 06/20/2011 :  9:34 PM
This is a personal experience, and I hope that it helps a little... I took the same turn 3 different times and got 3 different results.

1. I slowed to the posted entry speed of the turn and I grabbed the clutch at the start of the turn. The bike coasted and slowed some and felt really poor. There was a feeling of 'not pushing' into the roadway or the turn. I didn't like it at all. It just didn't feel stable at all.

2. Slowed to the entry speed posted and just held the throttle without making any changes. The bike slowed noticeably and at the exit of the turn felt weak.

3. Slowed to the entry speed posted and as I reached the apex I lightly rolled on the throttle. I found that I needed to lightly increase that roll just to maintain posted speed. Bike felt great and I felt more in control.

Granted I'm speaking of how it feels, but I'm not a physics person. I can only talk about what I know...

The original poster asked if we were actually speeding up, or merely maintaining speed.

In this situation:

Are we calling accelerating = increasing speed?

Or are we calling calling accelerating = lightly rolling on the throttle to maintain speed?
Go to Top of Page

rayg50
Male Moderator
2082 Posts
[Mentor]


NYC, NY
USA

Honda

Shadow Spirit 750DC

Posted - 06/20/2011 :  9:38 PM
quote:
Originally posted by rider5
... I'm not qualified to get involved in the science because I only have a laymans knowledge.


IMO other than the use of the word science none has been presented in my series of exchanges. So far it is mostly word games. Hopefully we can get past that.
quote:

To me the issue is contextual.

I agree. Picking one word out of a complete thought and then debating it IMO serves no purpose.
quote:
Roadcraft is not, does not attempt to be so definitive it becomes limited, nor is it incorrect. It doesn't actually say constant throttle increases stability and grip, but what it does say is "to get maximum cornering control, avoid altering your road speed at the same time as altering direction."

I think Robsalvv is having trouble understanding that. The pity is that he raised an interesting point but appears more interested in winning a word game then shedding light.
quote:
I have learnt from the exchange, but have not changed my opinion regarding roadcraft.

Nor should you change your mind. IMO roadcraft is an excellent model to be followed by all riders.

What is being proposed by RobS IMO is not something many could apply even if the logic were correct, which I do not believe to be the case. It is just not street riding for fun applicable. How many riders do you know that could come close to being able to know how much throttle will produce a .1g acceleration? Of those how many could consistently do it regardless of all the variables that different curves provide? When asked about the 2 riders entering just below the traction roadcraft provided the answer not KC (do not do it).

My point? Continue to champion and teach Roadcraft.

I am only part of this thread because I do not want a rider going off the road because they actually buy into unsafe practices.
Go to Top of Page

(Deleted or Lost)

Posted - 06/20/2011 :  9:40 PM
quote:
Originally posted by James R. Davis

Once again you wish to use my words (extreme paraphrase or not) to prove you are right and I am not.

That article, as it turns out, was really about STABILITY - and pointed out that the rear tire is primarily responsible for MAINTAINING a path of travel while the front tire is used to DESTABILIZE the bike in order to arrive at a new path of travel.

As to what's in my book ... you can buy it and see for yourself. It will fit right next to, on top of, or under, your book on roadcraft. If there are errors or inconsistencies or discrepancies in it, please feel free to share them with us. No doubt the book explains things differently than roadcraft does. Perhaps telling them about those differences would also be in order - perhaps not.


What a puzzling post.

Clearly we are no longer communicating effectively.

So be it.

Edited by - Robsalvv on 06/20/2011 9:47 PM
Go to Top of Page

(Deleted or Lost)

Posted - 06/20/2011 :  10:06 PM
quote:
Originally posted by rayg50

Cheers Rob, I just returned from a pleasant ride. We are entering our summer so I have to take advantage of any good days. I assume you are approaching your winter since you are south of the equator.


RG: 4- Prior to entering a turn, while travelling in a straight line at a steady speed there is a fixed amount of traction and traction reserve.

RS: Point 4 will hold for the corner IF the corner is perfectly flat and has the same road surface.


Did you have a different one other than #4 in mind? I make no reference to cornering. I just wanted to state that no unusual forces were influencing the bike prior to the entry.

Ray, I was just pointing out where point 4 wouldn't hold, i.e., in a banked, positive cambered pavement turn. If a bike entered and maintained the same speed it had on the flat pavement, then total/available/maximum amount of traction would increase by some amount in a banked/cambered pavement turn (if my understanding is correct), given that the effective weight of the bike has increased. This has been discussed in these fora.


quote:
I actually do not care what the road condition is as long as we can agree that for the purposes of this discussion there is no change in road surface between the curve and the straight approaching it. My focus is on the curve itself which is what I thought was your point of reference when speaking of accelerating rather than maintaining speed.
I'm not sure how my comment is at cross purposes with your statement.



quote:

Point 6 & 7 don't hold for a constant radius, constant speed cornering approach. There is no apex so to speak.
Which is why I referred to the bikes apex and not the curves.

If one is cornering with a constant radius, what point do you call the apex? So then you must be assuming a "line" through a corner. Is that correct?


quote:
What I am hearing you say is that you do not use any lines in negotiating a curve. You follow the contour of the curve. I assume your use of the word approach was a slip. I want to discuss the dynamics once you are in the curve.
I said no such thing. I was only doing as you asked, pointing out where the points might not hold.

I simply pointed out that your points 6 and 7 cannot hold if the approach one takes though a corner is a constant radius approach. Much of the discussion in this thread has been about constant speed, constant radius approach. I'm happy for you to define the kind of cornering line that you wish to apply to points 6 and 7, but as stand alone statements, I believe they don't hold true in the constant speed constant radius situation described.


quote:
We can always add a couple of points of agreement to cover that situation. I had wanted to limit the variables but I am fine with adding some points of agreement. Please describe the progression of traction change in a constant radius constant speed curve. Unless you say there is no change I will probably agree.
I think you ask this question with an incorrect assumption. Please consider these responses and if the question still remains pertinent, I'll answer it.



quote:
What I am trying to do is set the stage for an honest exchange of ideas. I am intentionally not using any terms other than traction, traction demand, and traction reserve. I am happy to accept whatever definition you would care to assign them. I intentionally spoke of the bikes apex for fear that if I said the curves apex I would find myself in an ever changing list of possible apexes.

I just want to see if what you propose holds water. If it does that is fine. I will have learned something new and any day I learn something new is a good day. So let us agree on the ground rules and move on to the actual disagreement.
You're singing to the choir Ray. :-) I look forward to the subsequent discussion.


Go to Top of Page
Page: of 6 Previous Topic Discussion Topic Next Topic  
Previous Page | Next Page
Jump To:
All Things (Safety Oriented) Motorcycle © Master Strategy Group Go To Top Of Page
  This page was generated in 0.41 seconds. Powered By: Snitz Forums 2000 Version 3.4.05