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How serious IS Dorna?

Discussion in 'Racing, Motorsports, and Track Days' at netrider.net.au started by hornet, Feb 3, 2007.

  1. Matt Oxley in a recent BIKE magazine highlights the double-standards (one might say dishonesty) of Dorna with respect to the current crop of sub-miniature riders in MotoGP. Danny Pedrosa, for example weighs only 6 stone, but is allowed to compete on 'equal' terms with riders who weigh up to two stone more. Weight on the grid of Pedrosa's bike with him on board is 195kgs; Hopkins' bike tips the scales at 215kgs.

    There IS a minimum weight figure for 125cc racing (and F1 as well, not to mention weight handicapping in horse racing) but Dorna refuses to weight balance the 250cc and MotoGP classes. I wonder why that is??


     
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  2. Can I be a cynic and suggest that Honda have DORNA's jatz crackers in their purse? This 800cc class is purely for Pedrosa's benefit so they can win back the championship - after all, it is THEIR champinship :twisted: So having jockey sized riders suits their agenda.
     
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  3. I've often wondered how much difference it really makes (within a certain range).

    I mean, peak corner speed is determined by the angle of the CoG, which is affected by how far a rider can get their weight off to the inside of the bike/corner.

    A shorter lighter midget rider will have less mechanical leverage to affect the bike's CoG. Sure, they'll accelerate quicker due to less weight and less wind drag, but theoretically they shouldn't be able to hold as high of a corner speed as someone who's a little taller and heavier who can affect the CoG to a greater degree.

    The differences may not be large, but then again, with 200-210hp over a combined total of 200-230kgs, the acceleration difference isn't going to be enormous either. In fact, various wind-tunnel tests show that a larger rider can actually effect a lower co-efficient of drag because they can form a smoother flowing shape from the screen to the rear of the bike. Obviously this depends on how big the bike is too.

    I guess that it comes down to what really are the differences, and are they large enough to worry about? It's not like the riders are riding racing horses where even a couple of kgs can make a significant difference to the speed of the horse.
     
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  4. I suppose when less than a second can separate the key positions at the front of the grid, the tiniest advantage over 26 laps could make all the difference.

    Meh...just so long as the racing is good!
     
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  6. 38kgs :shock: I think he'd be too small to be a jockey :p

    I'm no racer, but agree that lighter weight would be advantageous simply due to "power to weight" being better for DP.
     
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  7. And yet the MotoGP media have been questioning Pedrosa's ability to fully control the bike due to his small stature. and Honda put him on a program to help him build himself up as much as possible.
    AFAIC, if the little guys rule, so be it.
     
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  8. Nah, friction physics means that as the weight is increased, so does the total friction.

    If that were not true, then trucks could not stop anywhere near as quickly as they do.
     
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  9. I thought that if mass increases, friction must increase to compensate for it, If the tyres are already on their friction limit when mass increases the tyres will slip, or you can reduce the speed allowing the tyres to hold to the road.

    If haeavier blokes were better Hayden would not look like an ethopian this year and he has commented how he has tried to become lighter.
     
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  10. That's true. What I said, and what you're ignoring, is that total friction is proportional to the mass, so as mass increases, so does the friction. The two effectively balance out.

    What a heavier mass may achieve though, is greater tyre carcass flex which may or may not assist with having more rubber on the road, and thereby increasing the co-efficient of friction.

    Total tyre friction is proportional to mass which is pushing them against the road. Increase the mass, you increase the friction. It balances out. What may alter is as I said above, more rubber in contact with the road, giving a slightly better benefit to the heavier rider as the tyre has a larger contact patch with which to deal with surface irregularities (i.e. increases the co-efficient of friction).

    This may be because of the 800cc's power delivery. With the 990cc bikes, you could probably get away with being a ltitle heavier and it'd balance out. With the 800cc bikes, that may be less true, which brings us back to the opening post and the question I raised - how much of a difference does it really make?
     
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  11. Wouldn't there be an 'absolute' limit for the tyre friction? Or are you saying that even a 200kg rider would produce friction proportional to the weight increase?

    Personally I would back the little guy over a bigger guy any day. :LOL:

    (I'm not a little guy)
     
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  12. so your saying the harder the tyre is pushed into the ground, the more friction the tyre can cope with?
     
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  13. As long as the tyre doesn't burst, or the ground start to break up and start sliding itself, there is no real limit.

    The harder you push two surfaces together, then the friction increases with the pressure applied. The only time it varies would be due to compressible surfaces (e.g. tyres being "squishy") and the qualities thereof.

    So to answer your question, you could put a pair of the "Biggest Loser" contestants onto a ZX14R, and given the exact same tyres as put onto an NSR125 (not likely - but just for arguments sake let's run with it) with a 40kg rider aboard, and given that both bikes were able to lean without touching hard parts down to the point where the tyres started to slide, that lean angle would be the same, or given that tyres are squishy and you haven't caused the tyre to deform into some bizarre shape, may even slightly favor the big guys on the big bike because the tyre contact patch would be a bit larger.

    If you go down to PI track days, there's a guy there who occasionally turns up. He rides a 600cc super-sport and would easily weigh on close to 180kgs, if not a little more. He is freaking massive, and yet he is able to get around the track with both very high lean angles (as high as anyone else) and at lap times that embarrass all but the extremely skilled.

    Heck, I even remember go-karting with a friend who weighed in at 120kgs while I was at 80kgs, and it was impossible to match his corner speed because his kart would not slide anywhere near as easily. Of course, acceleration was another matter, but he'd hold a higher corner speed and slighshot onto a straight, and by the time you caught him up due to your lower corner exit speed, he'd be into the next corner carrying more speed than I was able to without sliding out again.
     
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  14. Danny Pedrosa weighs 51kg. The majority of riders weigh between 60 and 70kg. On a 125cc bike I would expect the effect would be more, but on a bike that weighs around 140kgs and makes 220hp I'd imagine the effect would be far less.

    And he needed the box to get on the bike due to injuries sustained the previous week, not because he wasn't tall enough.
     
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  15. It is in Dorna interest to have a competitive Spainard in the premier class. As for the wieght issue. I see both advantages and disadvantages to it.

    The larger guys like Hayden and the rest can realy muscle a MotoGP bike around. There strength and extra leverage can often stop the front from folding and they are better equiped to reduce the bikes constant need to flip itself over and launch said pilot to the moon. There disadvantages are probably an increase tire wear (Which is only a real issue in the last 10 laps of a race) and they are a little bit less aerodynamic at the stupid speed levels.

    I read once Troy Bayliss was always several km/hr slower down a straight than Loris Capirossi, and if you ever saw photos of them going at it, TB alsways had a very elbows out style. Not a massive disadvantage, but it still equaled a few km/hr.

    We onced bumped into Nicky and Earl Hayden in a pizza shop in Cowes, and he is by no means a large guy either.

    (Although I did have to strangle my friend into silence after he shouted something about doing better than sixth in the championship despite having a full factory Honda... :LOL: )
     
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  16. 51+140kg = 191kg => 220/191 = 1.0995 HP/Kg

    70+140kg = 210kg => 220/210 = 1.0476 HP/kg

    That's a 0.0519 HP/kg difference.

    Is that really a significant difference :-k Is Honda really spending a bazillion dollars on a 0.05HP/kg advantage????
     
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  17. Don't know. What was Honda's budget for the Asimo->Pedrosa cyborg project anyway?
     
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  18. Surely though with a cornering bike the force of the rider/bike's mass is acting in more than one direction. Yes increased mass means a greater force pushing down on the tyre, which increases friction - but it also means a greater force pushing the tyre sideways, which reduces friction. So it's going to come down to which is the greater force and if the rider is cornering at a force greater than 1g (something I imagine would be quite common in MotoGP) then it would have to be the lateral force. So more weight would mean greater grip in a straight line - but less on fast corners. I mean after all if extra weight were an advantage then shouldn't a bike go faster with a pillion.
     
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  19. Assuming that 0 degrees of lean is vertical, then the weight that is pushing down on the tyre is proportional to the cosine of the lean angle.

    So long as your lean angle is less than 90 degrees (bike is sideways) there is always some proportion of the bike+riders weight total (whatever that total is) pushing the tyres down onto the road.

    Weight pushing sideways does not reduce friction as such (not in the physical sense), it's just a type of force, for which so long as the size of the force is less than the friction of the tyre against the road, then the tyre will not slide.

    The tyre's friction is proportional to the weight of the bike+rider. The force pushing sideways is also proportional to the weight of the bike+rider. On both sides of the force equation we have the bike+rider weight, which therefore cancel out.

    The weight of the bike+rider does not alter when the tyres will slip out.

    This does not, of course, factor in what I was talking about where the weight of the bike+rider may deform the tyre to a more beneficial contact patch against the road.
     
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  20. Yes - but as long as the lean angle is anything other than zero there's also a proportion of the rider+bike's weight pushing the tyre sideways (which varies depending on forward momentum). Short of going down a very steep dip the mass of the rider/bike is only going to apply a force pushing the tyre downwards equivalent to it's weight since it's only acted on by gravity. But since the cornering force can be much higher than 1G that same mass can apply a force greater than it's weight (mass and weight are not the same thing obviously).
     
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