racer
-
Posts
1,135 -
Joined
-
Last visited
Posts posted by racer
-
-
G'day Racer
The point I'm trying to make is that if you spin the motor BACKWARDS, the swingarm WILL go down so with normal motor direction, the swingarm will want to go up, not down as you have mentioned. The swingarm however is attached to both the frame and a shockie which resist this movement and turn it into forward and up motion.
In the scenario of the bike with it's front wheel against the wall, if the bike could be supported at the same height and it's shockie removed, the chain is going to pull the back wheel UP, not down.
Sorry, Willy. Not a chance. If you doubt it, try it and see for yourself. (Nothing like the real thing, eh?)
I suggest you re-read my replies to Leftlaner at the top of the thread and put an eyeball on your own swingarm to notice where the chain is in relation to the swingarm. It is counter-intuitive, but, once you've scoped it out and try the "push her up against a wall" trick, I am confident that you will see the light.
As for what "is trying to lift the frame at the swingarm pivot point"...it is the swingarm that is angled upward toward the pivot point. If the swingarm was pointing down at this point (as would happen when applying rear brake with throttle on), then this would created a downward force at the pivot point and would lower the bike.Can you say precisely what force you believe is being applied to the swingarm and how? In what direction?
I'll give the rear brake/throttle/traction thing a bit more thought and get backCheers
Willy
Sweet as, mate! Looking forward to it.
Cheers,
racer
-
There used to be all different kinds of shift patterns--some on the right foot...
Did you read about the Carberry Enfield downunder in the current issue of motorcyclist magazine?
-
The bike is basically trying to counter-steer itself back up. I think the braking force causes the slowing front wheel to become an anchor point and the steering head behaves like a hinge with the momentum of the mass behind it applying force there that turns the wheel inward. The fork becomes a lever or moment arm with the fulcrum at the contact patch and outward force being applied at the steering head torquing the front wheel inward, hence, the bike comes up.
I'll try to edit that for clarity later.
-
Yee-aah. I wasn't sure whether to say something about that or not. Thanks in advance for inserting some breaks.
-
Hello all. It's been a while since I've been here.
I agree that the bike rises under acceleration but I don't think the chain has anything much to do with it. If you assume that the chain is trying to pull the rear axle down, then you could assume that spinning the gearbox sprocket in reverse would cause the rear axle to rise. Not gonna happen
I'd suggest that it has more to do with the angle of the swingarm to the frame i.e. it is trying to lift the frame at the swingarm pivot point.
Hi Big Willy,
Of course the angle of the swingarm to the frame is the critical issue. I thought that was made clear above. But, we've had long drawn out discussions between engineers here on this particular composition of component force vectors. Sufficed to say, at worst, it is both chain pull and what I believe you may be alluding to. In any case, without the chain, there would be no angular acceleration at the rear wheel, so, at the end of the day, it all comes back to the chain anyway. Can you be more specific about just what you think "is trying to lift the frame at the swingarm pivot point" as you state in your last sentence?
And, actually, if you could get the motor to spin backwards, the chain would still pull the swingarm down... due to its angle with the frame. So, no, I couldn't assume it would cause the rear axle to rise.
An interesting technique used in dirtbiking is to apply the rear brake while throttling on. This allows the chain to compress the shock effectively raising the rear wheel closer to the seat, effectively lowering the rear of the bike. This allows not only better throttle control, but alters weight distribution for better traction/drive. The same could theoretically be applied to track bikes.The rear brake is used as an advanced skill in several types of situations in road racing. Can you be more specific about how using the rear brake will redistribute weight "for beter traction/drive"?
Thanks,
racer
-
If this is true (and it is, just try and do a burnout from standstill), what situations cause it to compress? On occasion coming out of the T8,9 sections of Summit Main my swingarm comes up enough that I can feel it on the bottom of my boot. Also a buddy riding behind me said he saw the rear end squat under hard acceleration.
T8,9 at Summit main... the double apex carousel before the short straight that leads to the last corner onto the front straight?
If the compression damping on a rear shock is set too low and/or rebound set too high, the shock can "pack up" in high speed sweepers. But that isn't hard acceleration. It's cornering force at high speed.
In any case, your "buddy" probably needs glasses. Or he didn't know what he was looking at and was watching when you rolled out in the middle of the carousel to set up for the second apex. Unless of course you weigh like four hundred pounds and your rear spring is broken and the swingarm is angled up when you merely sit on the bike. Regardless, hearsay is inadmissable in any case. Go out and watch some bikes on track and tell us how many you see squatting under acceleration.
-
racer,
One sensation that I have in slow corners is that I feel like I can not lean the bike as far as in a fast corner. For some reason the slower speed gives me the feeling that I don't have enough momentum to actually keep the bike up. This is just a sensation that I get when trying to turn in to slow corners, almost like a sensation that the bike will just fall over. Of course to be specific about turn 7 at Road Atlanta, I do tend to miss the apex and run wide out of the turn. And at times I do have to roll back on and then off of the throttle. I have two main RPs in the turn, just before the end of the outside curbing for the turn in and just passed the crest of the inside curbing for the apex. I don't really have any other RPs beyond that other than doing my best to stay focused at looking down the track instead of to the outside of the track.
Thanks for your help. Also will you be at Barber on August 23 and 24?
Shane
Ok, if I understand you correctly, it seems that there are two parts to what you are experiencing or feeling as you approach and turn in to a slow corner. The first part is a mental reluctance or fear of leaning the bike too fast or too far at slower speeds because some part of your brain "senses" or believes that the bike doesn't have enough momentum to not fall over. The second part is a "sense" of being "rushed" or feeling like you are entering the corner too fast.
Hmm...
Ok... let me see if I got this straight.
Part 1: you feel like you are going too slow.
Part 2: you feel like you are going too fast.
(Sorry, I couldn't resist
)Seriously, I can see how part one could lead to part two. If you feel like you can't lean the bike fast enough or far enough, then there isn't as much space or time to get the job done. Hence, you simultaneously feel like you are going too slow and too fast. Man, that sounds frustrating. One part of you wants to go faster at the same time another part of you wants to go slower. What do you do?!
Well, assuming you have good tires and there is no mechanical problem with your bike that would cause you to fall over for no reason, I'd suggest finding some place like a large parking lot where you have enough room to conduct a little impromptu "skid pad" action. I would try to concentrate on counter-steering while you practice flicking the bike at slow speed. Then I would practice riding in a circle at slow speed while making the circle smaller and smaller, leaning more and more. First one way, then the other. Just try to get yourself comfortable with extreme lean angles at low speed in a safe open environment. Make sure the surface is clean and doesn't have greasy spots from parked cars leaking oil and whatnot.
Maybe there is some mental excercise you could do. Perhaps something as simple as some mental imagery. Like picture yourself doing what you want to do. If it is as you say, a bit of a mental block to doing something you know the bike can do if you apply the appropriate input at the bars, then maybe that could help make it easier, eh?
What do you think?
r
PS - Unfortunately, I don't have plans to be at Barber... unless of course the school decides to hire me on at Mid-Ohio... or something crazy like that. I suppose anything is possible. Now that I think about it, that has happened before....
-
I love the reverse shift pattern, if someone could tell me why the "street" shift pattern is the way it is that would be good.
Why don't all bike come straight from the shop with a reverse shift pattern?
Maybe because it is easier to think of down as down and up as up.
Shane
That's my theory. It keeps it simple for novice riders of the "general public".
The only time I ever had an issue with the GP shift pattern was during my first race weekend using it. It was a particularly intense 125 GP; and, dicing back and forth with a group of other riders, I overcooked a corner entry on the brakes. After I gathered it up mid-corner, I tried to grab a couple of quick downshifts in the heat of the moment and accidentally upshifted instead. So, no mechanical harm done, but, I lost all my drive coming onto the front straight and the video looked pretty funny with my wrist flailing on the throttle while grabbing about five downshifts exiting the corner. Luckily, I was leading the group when it happened and even though I lost several places, I finished my downshifts as the last rider came past and I was able to catch the draft and re-pass everyone on the brakes again going into turn one... lol. It was the first race weekend with the new shift pattern and it never happened again.
For the record, I greatly prefer the GP shift pattern over the street pattern for track riding.
-
If you use the search feature at the top of the page, you will find tons of information that has been written about this subject here.
The bottom line is that, on track, the reverse shift pattern allows for more positive, faster up-shifts with less movement, effort or distraction, hence, a faster, more efficient lap. It also allows upshifting in certain situations and at various lean angles that would be more difficult if you had to get your foot under the shifter and pull up.
PS - Matt Mladin is the only pro-racer I know of currently using the "street" shift pattern.
-
racer,
Honestly I never thought about the fact turn 7 at Road Atlanta is more than a 90 degree turn. That could be the biggest thing that causes me to go in to the corner too fast. Unfortunately the concrete patches are no longer there after the repave so a lot of the mid-corner RP are gone. I think my biggest issue is that I am turning in too early and using a lazy steering input. I really need to focus on waiting a little longer to turn in and finding the correct RP for the turn in. The quick steering input is something I will have to get my instructor to pound in to my head at Barber. Honestly it is something that I usually do not do. More than likely not being able to do the quick steering input is what leads to the early turn in as well. Ummm.
Thanks for the input.
Shane
Hi Shane,
Can you be more specific about your feeling that you are "going into the corner too fast"? Is there something concrete that you can point to? Are you running wide in the corner? Missing the apex? Are you up on the curb at the exit? Are you tempted to roll off the gas mid-corner? Is there some part of your plan, some specific mark that you are missing or sub-product that you are failing to achieve? Or is it "just a feeling" of being "rushed" at your turn point?
Do you have a plan?
racer
-
Forks don't travel until the bottom triple clamp hits the top of the slider on convential forks ..... They bottom out quite a few millimeters before then. How few of us mark the bottoming out point to see just how much of the actual amount of fork travel we're using?
So how is the bottom point calculated? I have asked this and have only gotten a range. I am close to being convinced that it's time to disassemble my forks (a whole other story). If I have to do it in order to find the bottom then it's +1.
It isn't calculated. It's measured. It bottoms where it bottoms.
Here's a decent diagram of a typical type of standard fork tube from "my day": http://www.racetech.com/articles/EmulatorFitting.htm
-
Unfortunately, at my level my club doesn't allow lap timers. I have to get bumped for that (soon I hope).
I'm not sure what that means, but, if you mean on board laptimers where you have to set up a beam next to the track:
Get a stopwatch and have a friend or acqaintance time you.
Of course, you'll need to actually have a friend or acquaintances to do this....
What a perfect excuse to make some friends!
(I prefer female pit crew myself...
) -
Hi Shane,
Ironically, most riders I know have the opposite problem, ie. fast corners being more difficult than slow ones. It is certainly the case for me. I wonder if there isn't another common feature to the corners you mention that isn't about speed per se.
The only corner you mention that I am familiar with is T7 at Road Atlanta, so... here's my off the cuff take on it.
First, the feeling of being sucked in too fast or rushed tends to be a matter of a lack of reference points (RP's). It's a lack of awareness of where you are in relation to what is coming next. The other thing I have to ask is if you are late braking such that you aren't off the brakes and relaxed and ready when the turn point arrives?
Aside from this, the only issue I've had with T7 at RA is that, while not being very fast, it is essentially blind. The approach is uphill, and the corner is bascially flat and the proper turn point is actually deeper than it looks because the corner is more than 90 degrees but unless you have walked it and looked at a track map, your brain (well my brain) tends to think it is a typical 90 degrees. I'm not sure why that is. Also, being that the approach is uphill and the corner is more than 90 degrees, the turn point is over the crest and the apex is beyond your line of sight when you look into it, as I recall. That is, when you look into the corner just before the turn point, you can't really see the next major sub-product (SP). Hence, you need something to fill the gap, some RP between the TP and apex that tells you where you are in relation to it. As I recall, I used some patches on the track surface.
Being a somewhat blind corner, my biggest issue with T7 is forcing myself to picture the corner as more than 90 degrees and wait to turn in deeper than I want to even though it leaves the door open to be passed because getting a good drive there is the key to a good run down that long back straight. But, people who (try to) outbrake there are only hurting their own drive onto the most critical part of the track. Of course, if they manage to block your drive/exit.... they gotcha!
Does this track for you?
racer
-
I've decided that I am definitely getting a new bike and going racing again next year. With the demise of the AMA 250GP I should be able to find a newer TZ250 for < $5k...
Well good luck with that racer, let us know how that goes!
I've got a friend that has got one in pieces in a garage--never put it back together after he crashed it last. I'll shoot him a note, see if he wants to part with it. He's had it there for a while, so likely not in a hurry.
C
Thanks.
-
I agree with you 100000 percent on the sense of speed thing Cobie. However, I had been suffering with confidence problems. And doing it this way, I could enter at a predicable speed each and every time until I was satisfied with my line and throttle control (smooth roll on, looking through corner, etc). Then I could focus on small increments of speed increases 2,3 or 5 mph and remind myself to keep the SRs in check that I was well within the limits. When the confidence picked back up and faster riders joined me...the speedo had to go and the speed climbed using sense of speed.
But alas, Soft Science is on my "To Do" list.
Excellent, glad to hear that. Hey Racer, lend me $20?
C
I'm sure we can work something out...
-
-
But alas, Soft Science is on my "To Do" list.
Grrrr.... don't get me started!
Do you need me to loan you $20?
-
google the "Gimli Glider" if you want a very interesting aviation story, plane was just retired.
As a lifelong student of aviation, that is a freaking fantastic story. I can't understand why I never heard about it before. That is the only example I know of a jumbo jet or any commercial jetliner executing an unpowered glide/landing.
A minor fire in the nose area was soon put out by racers and course workers armed with fire extinguishers.And don't forget to give a big thumbs up for our local cornerworkers on your cool down lap folks!
Coincidentally, the mechanics sent out to Gimli from Winnipeg Airport were left stranded when their van ran out of fuel...ROFLMAO
Thanks for that, sleepr. You made my day.
Speaking of slips, I should post some youtube links of my favorite 747 cross wind landings from Hong Kong... make your hair stand on end!
-
'good line' vs. 'fast line' is a good distinction. I just assumed that the good line was the fast line.
Perhaps a better distinction would be between a good line and the best line. And, like Kevin alluded, while different lines can be just as fast, one of them will be the most efficient, so to speak.
-
Still cross posting.
This set up doesn't work for IM'ing in real time very well.
I have edited my previous post again since you quoted it.
-
Yeah, we were cross posting just now. Didn't see your nic down there, kwh. Are you lurking? Heh heh.
Anyway, you can see I edited my post while you were posting a reply.
Actually the car was on the racing line and the biker thought that the car had moved over for him and went to dive past on the inside, the car merely took the correct apex for the corner, unfortunately the biker was already committed...Well, after watching several more times, I still disagree with your analysis. From my point of view, the car was well past the apex of that corner and was going quite slowly, ie. not committed to any line and made a sudden change in his line (very incorrectly) to move back across the track to line up for the next turn without checking his mirror. If you wait until the end, I believe that is the opposite angle from a stationary camera on the sidelines and you can see better what I mean.
-
Holy sh*t!!!
That first link looks like the car crashes that bike totally on purpose! The car totally moved over toward the inside of the exit of the turn into the bike's path for no apparent reason whatsoever... except to block the bike from passing.
Man, I would NEVER ride a motorcycle on a public track day with mixed vehicles like that. That's insane. It gives road ragers and maniacs free reign to kill someone and even get away with it. WTF!
EDIT: Ok, from the opposite angle you can see that the car must have been crossing the track to line up for the next corner except that he was going so slow he didn't have to and must not have checked his mirror first. At least that is what I will choose to believe so I can sleep tonight.
-
I guess I'm still not tracking this because while the points appear to make sense reality doesnt quite follow.
[snip]
So now that I can carry more speed through the corners (because I can make more use of the bike's abilities) how do I get even better lap times? I think the answer is figuring out things like reference points and lines.
That's a pretty big subject wrapped in a rather small question, yet, in a nutshell, it boils down to a pretty simple answer.
More gas. Less brakes.
As for the finer points... buy the books/DVD's, study, study, study and practice, practice, practice.
Going back to where I started and chunking it down a bit, lets break it in two. On one hand deal with the context of racing. On the other deal with the context of time trials.In the case of time trials (one bike on the track at a time like WSBK super pole) the rider can use whatever line he choses. If each bike had a GPS tracking unit on it and you collected all of their data I wonder what you would see? Would you see one line through the whole track, would it be thick or thin? Or would you see something like brownian motion? What if you had a lot of different classes participating and you had all their data (125cc, 250cc, 600s, liter bikes, motards and a few hells angles for good measure). What would you see?
You'd see a different preferred line in each class.
In the case of time trials I'm will to bet that in the hands of expert riders across all the classes you would actually end up with either concentric lines based on some factor (likely weight) or a fairly thin line followed by all the bikes. Thin line would probably be similar to the mechanical line (outside, inside, outside) you would draw on a map of the track. there would probably be a few variances to account for things line dips, tar snakes, gravelly spots, etc, but overall it would be like the mechanical line.But when you line up a bunch of competitive blokes on their bikes things change. During time trials I bet you don't see too many bikes sliding sideways on the exit of a turn or being backed in to a turn.
True enough.
How do the qualifing times compare to the race times?Typically, qualifying is conducted on special tires that give super-grip for a few laps before they are cooked. So, typically, qualifying times will be faster than race times; but, assuming a different tire is used for the race, the heat of the competition can drive the race pace down to the qualifying time and even surpass it. So, in this case, perhaps being all alone on the track isn't as important as simply having a clear track ahead of you.
ETA: Not everyone gets on well with qualifying tires, like reportedly Toseland. And some riders, in the AMA for instance, don't bother using them at all either for economic reasons or merely to minimize the distraction of yet another set up to worry about. At the end of the day, they may only lose a few spots on the grid and have a more realistic idea of how their set up compares and more practice time on their race set up!
If a race can absolutely be controlled from the front then why doesnt the guy on pole usually win from the very beginning? If all you need to do in order to win is get on the fast line and go fast then the guy in pole position should be able to win every time. I don't think that happens.Well, the pole winner does typically end up at or near the front. But, there are many factors involved between qualifying and the race. First, the qualifying session(s) are typically 1-2 days before the race, giving each team/rider time to improve the machine setting or learn the track better. Also, the difference between the first several riders is typcially less than one second. In fact, it's not unusual for the first 3-4 rows to be within one second of each other, that is pole and 12th place separated by less than one second. The difference between pole and 5th place on the grid may be less than three tenths of a second... you could cover them with a blanket in the blink of an eye! So, there just really isn't that much advantage to overcome in the first place.
And then, once everyone is together, all sorts of things like holeshots and braking and drafting and passing and blocking and tires and the heat of the moment, ie. RACING come into play.
Finally, that single hot lap for qualifying represents a level of riding that usuallly cannot realistically be maintained for an entire race either by the rider or the machine for various reasons including tire compound, tire wear, fuel load and the rider's physical/mental conditioning. More than anything, the heat of competition drives everyone's laptimes down. At best, the grid is a loose indicator of potential. There's nothing like another bike next to you (or in front) to cause the throttle hand to twist a bit harder!
Having said all of that, if the gap between the pole sitter and the next rider is big enough, say a half a second or more, like Casey and Rossi last week, it is not unusual for the pole sitter to jump off the line and lead the race unchallenged from "flag to flag" as the saying goes. I have seen it many times in my years at the track. And, in fact, that is what most everyone expected Casey to do last week. Ah, but then there's that little thing called racing again, and a guy like Rossi can qualify on the 3rd or 4th row and still win the race. I've watched him do it more than once this year.
We can throw in the fact that we're humans and fallable, but that pretty much does away with there being only one line. The physics might say "this is the line, there shall be no other", but then along comes man and screws it up. He enters the turn 3ft outside the leader but does his turn faster so that he ends up inside the leader on exit. However, physics says "you have sinned against me and I shall smite thee!" and his rear tire begins to slide a tad. But our sinner is a whiley rider and paid attention during level 4 and lets the bike begin to stand up with out giving back any throttle. Our sinner now is the race leader and he did it by not staying on the fast line and briefly stepping over the edge (just to be photogenic).While the average street squid might be 3 ft off the line from lap to lap, a good rider has the ability to be inch perfect from lap to lap. The best riders can literally put their bikes within about 3 inches of their line lap after lap after lap. Most importantly, they have a plan, a line in mind. And they KNOW where that line is even when they can't see it because other bikes/riders are blocking the view.
As for your "sinner", if I follow your train of thought, being faster or off-line in one part of the corner to get past another rider forcing a slower exit, but blocking the rider just passed is what's commonly known as a block-pass racing technique. And though the sinner may be in front, the lap will be slower and anyone behind will catch up. So it's risky business. All of these considerations are part of racing... and were outlined above. You really should re-read Kevin's post carefully and think about it. He covered all of this pretty well.
So is there one and only one line? Or are there several?Or Keith's book says "any line that allows your to apply good throttle control is a good line" - is this a round about way of saying - sorry dude - one line or what?
Again... you need to be really clear about the context. Keith is not necessarily talking about the fastest line. He is talking about a good line. Generally speaking, a good line has nothing to do with speed per se. It has to do with control. So, again, there is a difference between a good line, the fastest line, and a winning line. The one you choose depends on you, your bike and what your goal is.
racer
-
Hey sleepr,
What track is it you ride on up there in Winnipeg?
r
)
)
Bike Sitting Up Under Braking
in School Questions/General Discussion
Posted
This subject was discussed here a long while back and I seem to recall Keith weighing in and saying something to the effect that the bike is basically trying to counter-steer itself up, but, it was a long time ago. I may be mistaken. I will try to search for the thread when I have more time.
That said, I think a taller tire might amplify the effect.