acceleration

Discussion in 'Track Racing' started by bikeguy, Aug 13, 2004.

  1. bikeguy

    bikeguy New Member

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    I just did a few short sprints yesterday on a flat section of bike path and hit about 37 km/hr within just about 25 meters from a speed as slow as I could go without falling over measured as a max off my cateye speedo. Anybody else tried something like this? I wonder how fast a top track rider could reach 40 km/hr?!
     
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  2. taras0000

    taras0000 New Member

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    I think your speedo is off mate. through physics calculations, the numbers you gave means that you covered those 25 meters in about 2.5 seconds. how fast was "as slow as you could go without falling over"? A top level track sprinter takes about 10 seconds to get to 40 kilometers pre hour
     
  3. bikeguy

    bikeguy New Member

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    A top male 100 m dash sprinter will reach 37 km/hr in about 3 seconds, you must be severely underestimating a track cyclist sprinters speed. 10 seconds?? Yeah right. No the speedo is accurate, I took a rollout accurately and have measured against a known distance of 100 metres (100 meter straightaway on track). As slow as I could go is about 30 cm/sec. I know a really fast time for a 250 m is 18.0 sec so these guys must be ripping through the first 100 meters really fast. By the way I'm using a regular geared racing bike not a fixed gear.
     
  4. velomanct

    velomanct New Member

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    i did some big gear starts today. used a 53x13 and started at about 10km/hr. it took me exactly 10 seconds to reach 45km/hr on flat road. looking at my powertap data my peak watts were about 1400, but that was at a very low 75rpms. peak torque was 475 inch lbs, i thought it would be higher.

    standing starts are a lot faster in a smaller gear like 39x15. elite track racers can hit 65km/hr 20 seconds off the line(standing start, team sprint) BUT that is in a big gear like 50x14.

    what gear were you using? try a 53x13 from 10km/hr, it takes some muscle.
     
  5. velomanct

    velomanct New Member

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    i think he is about right. at an average of 5.36m/sec(~20km/hr) he will cover the 25 meters in about 4.5 secs. from 0 to 37km/hr at an acceleration rate of 8.2km/hr per second, that's about what i can do, at these lower speeds(<40km/hr).
    the difference is, he is probally using a smaller gear than trackies, which makes the acceleration a lot quicker.

    i myself can go from 0 to 40km/hr in about 10 or 11 seconds, in a big gear like 53x14, and i consider myself a sprinter.
     
  6. velomanct

    velomanct New Member

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    you can't compare the acceleration of a runner vs a cyclist.

    plus, the trackies are using big gears like 50x14, so they are way overgeared at the start.
     
  7. bikeguy

    bikeguy New Member

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    I think I used 36x17 or something like that so it was easy to accelerate although starting up the first 1/2 sec was slow as heck and I was spinning too fast at 34 km/hr. As to running and cycling if a sprinter can come up to 37 km/hr in 3 sec a top track cyclist should be able to easily beat it with the efficiency of cycling being much better than that of running assuming a suitable gear. As for time to cover the 25 meters I'm estimating about 3.40 sec assuming a similar accel curve to top 100 m sprinters. If I was held in blocks and could press down hard on the pedals while holding the brakes and then release the brakes I would be able to go much faster.

    Velomanct, 10 sec 10- 45 km/hr in 53x13 sounds quite good, unfortunately by left upper back and shoulder were injured in a crash and I try and avoid accelerating really hard in big gears 'cause you have to pull up so hard on the handlebars if you actually want to accel quickly. I really shouldn't even be doing these accels.

    -bikeguy
     
  8. velomanct

    velomanct New Member

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    i would have to say that the most efficient way to accelerate from 0 to 37km/hr would be running, not cycling. cycling is not more efficient than running, when you are accelerating from a dead stop, no matter what the gear. the only way cycling could become more efficient than running in this situation is if a highly advanced automatic transmission was used on the bike to allow the rider the most optimal cadence throughout the whole effort.
    give an elite trackie the choice of any gear combo and put him up against an elite 100m sprinter(runner). i still think the runner would reach 37km/hr first.
    i just can't imagine there being a faster acceleration from 0 than running.
     
  9. RyBike

    RyBike New Member

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    Well said, I completely agree. You need some kind of specail gearing system to beat a runner in initial acceleration.

    Now...if we are talking about top-end speed, I think the cyclist has a little bit of an edge. :)
     
  10. taras0000

    taras0000 New Member

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    simple reason why a runner will always beat a cyclist is the fact that a runner is not applying his force through a disadvantaged lever. the bigger the gear you use, the less leverage you have. it doesn;t matter how small a gear you use, you will never be able to accelerate as fast as the runner for the simple fact that the runner has not lever to work against.
     
  11. velomanct

    velomanct New Member

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    i am willing to bet that elite track sprinters can go 0-40km in considerably less than 10 seconds, in those big gears.
    i did some more standing starts in the 53x14 today. it took me 8 seconds to go from 0 to 40km/hr, according to my powertap data, during 2 of these efforts.

    i will have to ask christian stahl about this, he is racing the team sprint in athens.
     
  12. taras0000

    taras0000 New Member

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    velomanct, what sort of wattages were you hitting for these efforts. 0-40 in 8 seconds is pretty good.
    Haven't tested it in a while, but my best 0-40 time was 9.02s
     
  13. velomanct

    velomanct New Member

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    after looking at the downloaded data, i started at 4kph and 7(!) seconds later hit 40kph. so i adjusted for that and said 8 seconds for 0-40. (next time i will make sure i am completely stopped)

    around 1400 in the last half of the effort. my true peak is 1700, during normal sprints. i don't know how accurate this timing is, i am just looking at the power tap data on my pc.
    i should also add i am 80kg
     
  14. drewjc

    drewjc New Member

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    Im not too sure about the speeds that i am reaching but if it helps, i am a reasonable sprinter (11.5sec 200m) and state medallist in the team sprint (as starter) and i can do 100m standing starts in around 9.8secs. Sorry i have no way of telling you how fast i am travlleing at this point but i thought that some of you physicists may have a formula that can approximate the speed? I usually ride about a 91.8 (51x15) gear for this type of effort. From my estimates i would be doing over 45km/h by the 100m as a runner doing the same distance would be doing a similar time (ie 10sec) but i would overtake him basically at the 100m mark at a much higher speed.
     
  15. velomanct

    velomanct New Member

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    100 meters in 9.8 seconds is an averaged speed of 37kph. assumming a steady acceleration, you were probally at around 53kph at the end.

    one of my standing start efforts was 0-50kph in 53x15, and it took me about 10.5 seconds, for those 100 meters.

    you are a little faster than me. 11.5 is a very respectable 200m time.
    i haven't been on the track yet, but i did a flying 200m effort on my road bike in my 53x16 with an average speed of 62kph, or high 11s.
     
  16. bikeguy2

    bikeguy2 New Member

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    Cycling is far more efficient than running and I can think of four reasons off the top of my head: 1) body's centre of gravity doesn't pop up and down like in running 2) leg acceleration and deceleration and kinetic energy is far lower in cycling (almost constant) leg tip velocity exceeds 100 km-hr for good 100 m dash runners 3) you can't use the hamstrings and hip flexors to actively assist in running but you can pull up on the pedals in sprint cycling 4) cycling uses constant and lower forces applied to the pedal continuously while in running the power only comes when in contact with the ground which is a very short period of time in sprinting.

    This is probably why the marathon time for 42 km is 2 hrs 5 minutes while a good cyclist can take it down in less than an hour. I can easily beat my 100 m sprint time on a bike and am faster over 10-25 meters as well.
     
  17. velomanct

    velomanct New Member

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    we were talking about accelerating from 0 to ~37kph/23mph. running is more efficient during the first few seconds of acceleration. i think we all know that cycling is more efficient just about everywhere else.
     
  18. bikeguy2

    bikeguy2 New Member

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    Velomanct, as I said I can easily beat my 25 meter dash time on the bike, no way I can run 3.40 25 meter. If I used starting blocks and could hold the brakes and press down hard on the pedals before accelerating I would go even faster over the 25 meters. Cycling is more efficient period, none of the factors I listed are affected by velocity they are true at all speeds and distances.

    Try a 36x17 and see how fast you can go.
     
  19. rayner

    rayner New Member

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    Just outa curiosity what kind of time are you doing for your start lap?
     
  20. closesupport

    closesupport Banned

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    i see you all saying that you get up to 23mph in said seconds, now i ride at that where ever i go, just this afternoon using 49x15 i was maintaining 32mph, how fast does one have to be able to spin at (RPM) plus whats the best way to improve the strength in your legs for spinning in bigger gears when im on the 11 it seems i pedal alot slower but still maintain 30mph.

    now i consider myself to be a cyclist but have decided that i like track and would like to continue doing it, plus would using a larger front chain ring 56tooth make it easier when i go to ride a 50x14 fixed. would the larger ring help if build up strength or would i be better working on RPM's in smaller gears or both..

    whats the key to becoming a good track cyclist?
     
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