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MotoAmerica changes for 2018

Discussion in 'General' started by rcarson15, Sep 9, 2017.

  1. stangmx13

    stangmx13 Well-Known Member

    the percentage change in all your examples is 22% because the only thing you are changing btw each rider is mass: (550-450) / 450 = 0.222. this suggests that gaps should be the same on all bikes, maybe it takes 22% longer to get down each straight. and yet we know that smaller riders are at a greater advantage on lower HP bikes. your conclusion from analyzing with only F=ma is incorrect.

    the effects of weight are revealed when u combine F=ma with a distance & time equation. lets assume constant acceleration.
    1) d=0.5(F/m)t^2 + vt
    - use a 1000m straight, a 40mph (18m/s) turn onto it
    - 1000 = 0.5(F/m)t^s + 18t
    2) lets make up some numbers for F/m because we don't actually know force
    - (a) == lowest HP, (b) == middleweight, (c) = highest HP
    - F/m: (a) = 1 & 1.22, (b) = 5 & 6.1, (c) = 10 & 12.2
    - notice that each pair is 22% different
    3) solve for t all 6 times
    (a) = 30.2 & 28.3 seconds
    (b) = 16.7 & 15.4
    (c) = 12.5 & 11.41
    4) find the difference btw each pair
    (a) = 1.9s
    (b) = 1.3s
    (c) = 1.1s

    now its obvious that a lighter rider on a smaller bike has a larger advantage than on a bigger bike. I think the advantage increases if you don't assume constant acceleration, but im not sure. and of course, this advantage has nothing to do with grip or skill.

    so whats the real issue - time. the smaller bike spends more time on each straight. so that 22% increase in acceleration is compounded over a longer time, allowing the lighter rider to pull further away on a lower HP bike.

    edit: I did the 22% the opposite way each time on accident. in the first paragraph, the heavier rider is 22% heavier. in my analysis the lighter rider has 22% more acceleration. a small diff that doesn't change the conclusion, but ya.
     
    Last edited: Jun 15, 2018
  2. grasshopper

    grasshopper Well-Known Member

    Chirp chirp chirp....
     
  3. Scott S.

    Scott S. Well-Known Member

    Interesting data, thanks for that. The 300 Cup isnt a apec class anymore so I dont know how to equalize things or even if they should try. Back in 2015 we had the smallest kid and usualy had the highest trap speeds but did not win any races. Perhaps just let the brands slug it out for overall bragging rights.. it sells bikes.
    By 2020 they may all be 400, 450, or 500cc bikes. Equal displacement all brands, engine configuration free, let the best rider-bike win.
     
    Last edited: Jun 15, 2018
  4. stangmx13

    stangmx13 Well-Known Member

    when racing is left to the whims of manufactures, we get the bullshit found in WSBK the last few years - a complete lack of parity, specific teams running away with all the wins/titles, terrible racing, and decreasing fans/viewership. racing is entertainment first and the manufacturers need rules so they don't mess that up. the RC390R and the Ninja400 are proof they will fuck it up if we let them.

    even if all the bikes are 400cc in a few years (more open rules wouldn't work if 400-500 was allowed), I really doubt the manufacture invested into making them track worthy would be anywhere close to equal. and without that, ull have something similar to an RC390R vs a CBR500.
     
  5. alan

    alan Well-Known Member

    WSBK has already made more limitations to the ZX10RR this year and hasn't changed the results. Rea is just the best rider in the field.
     
    Boman Forklift likes this.
  6. stangmx13

    stangmx13 Well-Known Member

    Yamaha has 3 wins, privateer teams have multiple podiums, and both Duc and Kawi are oddly slower with more frequency. nah, the results have changed. its just not enough to impact the championship all that much.
     
    Gorilla George likes this.
  7. Gino230

    Gino230 Well-Known Member

    Without putting up any formulas, I would think that over 100 MPH aerodynamics are far more important than smaller weight differences. Especially with smaller bikes, which are much more likely to reach terminal velocity on the straight- which probably has alot more to do with the size difference of the rider than the weight of the rider.

    The day I feel like I lost a race because of my size alone, I will resume worrying about it.
     
    cajun636 likes this.
  8. :D

    Me too. On the Grom (stock motor), I was never, ever, going to win a race against the kids and tinkerbell girlymen. It was a physical and mathematical impossibility. Against the lesser riders, I could make up ground in the corners, but even the shitty riders would pull 20+ bike lengths on the straights. Granted, that's because we were racing on large tracks. Perhaps on smaller (mini/go-kart) tracks, I might have a better chance.

    On the 600 I am much more competitive. It helps that my R6 is a missile, so it puts things on a more level playing field. But an equally skilled tinkerbell rider on an equally built R6, and I am back to being in a bind. Luckily there are very few (if any) equally built R6's :D.

    I do better on 1000's, but that might be because I like 1000's better. They are more fun to me and I feel more comfortable on them.
     
  9. The A=F/M formula is correct for the point I was trying to make. I was responding to Rob's "it does a difference" comment in regards to HP/weight ratio, and putting it in mathematical terms. Therefore I simplified it to the most basal level for ease of mathematics to address the point of acceleration (simply based on movement from point A to point B).

    As we all know, there are 6,973,254 variables when it comes to lap times and racing...especially when comparing different riders on different bikes. Not to mention different tires, suspension, motor builds, etc. Hell just the width of the rider's shoulders, arm length, windscreen height, and ability to get into a good tuck are all variables. Then of course, the biggest variable...skill.

    The main points I was trying to make were:
    1.) Rider weight does make a difference when it comes to acceleration.
    2.) On smaller bikes, rider weight plays a huge role in the outcome because everyone can utilize 100% of the available traction at all times (meaning within reason, no amount of skill can overcome a drastic weight difference, especially on very small bikes). On larger bikes, skill is a much bigger factor because grip availability and utilization is a much bigger factor...which means skill plays the biggest part in the outcome.

    This is one of those things that can be picked apart and analyzed to death. Hell, even the term "straights" is a huge variable. It is almost impossible to compare straightaway lengths (and time spent on the straights) between different bikes. As it applies to HP utilization and time/distance, the smaller bikes have shorter straightaways (assuming the rider on the Liter bike is applying the appropriate riding style to utilize the bike's strength). The main goal when racing a Liter bike is to spend as little time as max lean angle as possible. Hence Liter bikes carrying less speed at apex than smaller bikes. The goal is to "get it in there, get it slowed down, stand it up, and fire it out".

    But now we are getting into comparing different sizes of bikes, rather than comparing different sizes of riders. So that is a whole different discussion.
     
  10. stangmx13

    stangmx13 Well-Known Member

    U can’t make the assumption that a heavier rider is less aerodynamic. Bodies come in too many shapes. A tall skinny rider can be more aerodynamic than a short rider of the same weight because they fill more dead space near the tail without presenting more frontal area. Because of the variability in this, a general analysis concerning aerodynamics is mostly pointless and maybe impossible.

    And who cares if aerodynamics might be more important. Less weight is a provable advantage, which is why combined weight regulations exist in low HP classes.
     
    Last edited: Jun 16, 2018
    Boman Forklift likes this.
  11. stangmx13

    stangmx13 Well-Known Member

    Ya u said there was a difference, but then stated it was the opposite of what we know to be true: “So it isn't that things get "more equal" on bigger bikes, they don't. Actually the opposite is true.“. I’m not sure why u simplified things so much so that u contradicted common knowledge, hehe.

    The rest doesn’t need to be picked apart to death. I already gave u a proof with actual results showing something we’d all consider an “advantage”. All the other stuff u brought up doesn’t matter one bit. If a motorcycle is accelerating for any set distance, a lighter rider will have a larger advantage on a lower HP bike than a higher HP bike. That’s it.
     
    Last edited: Jun 16, 2018
  12. I made a comment a few months ago that if things keep going the way they are, we will be back to having new 600cc bikes again. :D The MW class has stalled because there is too little of a price difference between 600's and 1000's, with too much of a performance difference.

    There is (according to the specs) little to no difference between a 2006 GSX-R600 and a 2018 GSX-R600 (in terms of curb weight, HP, 0-60 time, 0-100 time, top speed, electronics, etc)...but yet the price has damn near doubled in that timeframe.

    The price has also increased on 1000's, but yet the bikes have improved drastically due to the focus on development.

    It used to be that 600's made 110hp, and 1000's made 150-160hp...with all of them having the same specs as far as electronics, braking components, etc. These days 600's still make 110hp, and are still analog...but 1000's make 180-190hp, have advanced electronics, Brembo braking components, race-worthy suspension, lightweight parts, etc. Liter bikes have gotten way more advanced, way more powerful, lighter, and overall much better...while 600's have stayed the same. Even the "new" R6 has the same motor, frame, swingarm, etc that it has been using for 10 years.

    It is no wonder 600 sales have dropped. Why spend $13k on a 600, when for $16k you can get a bike that weighs the same and handles damn near as good, but makes 60-70hp more, has advanced electronics, better suspension, and better brakes?

    BUT...the "little bikes" keep getting bumps in displacements. 250, 300, 400, 500, so on and so forth. Before long, the "little" bikes will be back to 600cc, and we will be getting all new MWs again. :D
     
    5axis likes this.
  13. I prefaced that by saying "if the rider weight and bike weight stays the same". I didnt mean "equal" in terms of race results and lap times, I mean "equal" in terms of the effect rider weight has on overall acceleration, again with all other variables removed. According to the figures I used, the ratio is around 18%...which means the end value changes as the HP changes. It is illustrated in my post.

    Im not talking about skill, or straightaway length, or available grip, or any other factors. For the sake of this point, we don't even have to be talking about riding on a track. I was only using the formula a=f/m, allowing hp to represent force, and rider+bike weight = mass. I know technically hp and force have different definitions, as do mass and weight. But again, I was only putting Robs comment into mathematical terms, and removing as many other variables as possible.

    But of course, we are getting way outside the realm of racing applications the further we go down this rabbit hole.
     
  14. stangmx13

    stangmx13 Well-Known Member

    why do u think thats illustrated in your post? u showed that weight changes acceleration by 18% which agrees with my first response to u. 18% smaller == 22% larger with these numbers. so since each case is an 18% difference, why do u conclude that HP changes anything? do u see something in the actual math that im missing or did u jump to that conclusion based on common knowledge? I don't understand how u got there.

    this is one concept that is at the heart of nearly all racing applications. theres no rabbit hole, haha
     
  15. Mongo

    Mongo Administrator

    Y'all talk too much.
     
    Last edited: Jun 17, 2018
  16. Gino230

    Gino230 Well-Known Member

    Good points, but without making any assumptions, the acceleration formulas only take you so far- wind resistance on the frontal area of the bike / rider is what is keeping the bike from continuing to accelerate down the straight. So the bike can't continue to accelerate at the same rate until it hits top speed.

    But of course as you said aerodynamics has nothing to do with weight, which is pretty much the only thing we can change anyway- so it's moot. :D
     
  17. RRP

    RRP Kinda Superbikey

    Now you see Chris, this one is a rant...

    :crackup:
     
    Gorilla George likes this.
  18. GNC

    GNC Jim Rashid

    When we raced 600's in the 750 class in AMA we had to add about 10lbs to the bike. At Road America and Daytona it was just about 1 sec per lap. At smaller tracks it was very negligible.
     
  19. *too

    Unless you are referring to someone named "much", in that case disregard.

    :moon:
     
    Last edited by a moderator: Jun 17, 2018
  20. I said "rabbit hole" referring to the hole things often go down on the beeb. Someone makes a generic point for simplification, then someone else comes along and takes one piece of that entire post (that wasn't even part of the main point) and over-analyzes it, then a discussion ensues, and before long nothing being talked about is relevant or had anything to do with the original point. But anyway, at least it helps pass the time. This response will be long, but im bored, waiting on more coffee, and type 95 words/min. So fuck it.

    Ok, we agree the difference in acceleration is 18% between the lighter and heavier rider. I was putting a mathematical value on what that 18% represents.

    For the sake of explaining the point, we could say acceleration represents the utilization of HP for forward movement. Which means the 18% represents the difference in forward movement for lighter and heavier riders.

    For the sake of making the point, if we remove drivetrain losses, etc, and could somehow have a rider that weighs 0lbs on the bike, he would affectively utilize 100% of the available HP for forward movement. In this case we have a 100lb rider, and a 200lb rider. The 200lb rider accelerates 18% slower...or he has an 18% lower rate of HP utilization for forward movement...I was putting a numerical value on that rate. When defining acceleration as the utilization of HP for forward movement, that utilization value is based on a %. As is the case with any %, as the number increases the end result of that % rate increases (18% of 200 is more than 18% of 10). That is what I meant by as HP increases the acceleration differential rate changes.

    Or in my original post, when using the formula a=f/m ...


    You alluded to another way to show how the differential changes as HP increases when you mentioned time. We agree that as it pertains to bikes, time = distance covered.

    Lets use Pedrosa. As pointed out by Rob earlier, he is very light, which gives him a much better HP/weight ratio...so he jumps off the line like a rocket. So for the sake of discussion, lets apply him to the figures we are using and say he has the same 18% better HP utilization rate. If the bikes only had 10hp, and T1 was only 100' from the starting line, he would barely be in front of anyone because not much time (distance) will have passed, and he only has an 18% acceleration advantage.

    18% of only 10hp, when only talking about traveling 100' isn't that big of a deal. He may only be a few feet in front of everyone.

    But give the bikes 250hp, that 18% difference is now huge. AND move T1 to 1000' from the starting line. Dude would have a good advantage by T1 (as we have seen in the past).

    *BUT... the reason this math doesn't necessarily apply to "common knowledge" (as you said), is because mini bikes do not weight 350lbs. As the weight of the bike increases, the rider weight becomes less of a factor overall. I was simplifying it by using the same bike weight in each equation.

    But in reality, that isn't the case because as HP increases, bikes typically get heavier. That is why I said this math is just for simplifying things to illustrating how weight affects acceleration.

    So yeah, because the rate of acceleration is based on a %, with all other variables staying the same, the end value of that % changes as HP increases. However, in the real world, where bike weight does change as HP increases, it alters the formula to a point of not necessarily being applicable in absolute terms. As the "vehicle" weight gets higher and higher, rider weight becomes less of a factor. For example, putting a 200lb passenger on an airplane in place of a 100lb passenger won't affect the acceleration (in any ass-dyno measureable way), because the "vehicle" weight becomes the dominant factor.

    But of course, if the airplane was on a treadmill, that would make all the difference in the world. :D
     

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