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Thread: Shock lenght question

  1. #11
    Join Date
    Jun 2008
    east of holland 50feet from the german border

    Re: Shock lenght question

    Whahahahawa, nice one Kendo, FPMSL. Flat fookin' sausages.......... .................
    Birdie num num........

  2. #12
    Join Date
    Aug 2011
    Rainycity Glasgow

    Re: Shock lenght question

    Quote Originally Posted by kendo View Post
    Very much , it corners like it is on a paddock stand.

    What do you mean, an African or European Swallow?To begin with, I needed basic kinematic data on African and European swallow species.

    South African Swallow
    (Hirundo spilodera) European Swallow
    (Hirundo rustica)
    Although 47 of the 74 worldwide swallow species are found in Africa,1 only two species are named after the continent: the West African Swallow (Hirundo domicella) and the South African Swallow (Hirundo spilodera), also known as the South African Cave Swallow.

    Since the range of the South African Swallow extends only as far north as Zaire,2 I felt fairly confident that this was the non-migratory African species referred to in previous discussions of the comparative and cooperative weight-bearing capabilities of African and European swallows.3

    Kinematic data for both African species was difficult to find, but the Barn or European Swallow (Hirundo rustica) has been studied intensively, and kinematic data for that species was readily available.

    It’s a simple question of weight ratiosA 54-year survey of 26,285 European Swallows captured and released by the Avian Demography Unit of the University of Capetown finds that the average adult European swallow has a wing length of 12.2 cm and a body mass of 20.3 grams.4

    Because wing beat frequency and wing amplitude both scale with body mass,5 and flight kinematic data is available for at least 22 other bird species,6 it should be possible to estimate the frequency (f ) and amplitude (A) of the European Swallow by a comparison with similar species. With those two numbers, it will be possible to estimate airspeed (U).

    In order to maintain airspeed velocity, a swallow needs to beat its wings forty-three times every second, right?Actually, wrong. By comparing the European Swallow with bird species of similar body mass, we can estimate that the swallow beats its wings 18 times a second with an amplitude of 18 cm:

    Species Body mass Frequency Amplitude
    Zebra Finch 13 g 27 Hz 11 cm
    European Swallow 20 g ≈ 18 Hz? ≈ 18 cm?
    Downy Woodpecker 27 g 14 Hz 29 cm
    Budgerigar 34 g 14 Hz 15 cm

    Note that even the tiny Zebra Finch flaps its wings no more than 27 times a second while cruising.

    If we ignore body mass and look only at bird species with a similar wingspan, we can estimate an average frequency of 14 beats per second and an amplitude of 23 cm:

    Species Wingspan Frequency Amplitude
    Budgerigar 27 cm 14 Hz 15 cm
    European Swallow ≈ 28–30 cm ≈ 14 Hz? ≈ 23 cm?
    Downy Woodpecker 31 cm 14 Hz 29 cm
    European Starling 35 cm 14 Hz 26 cm

    By averaging all 6 values, we can estimate that an average European Swallow flies at cruising speed with a frequency of roughly 15 beats per second, and an amplitude of roughly 22 cm.

    Skip a bit, BrotherLast month’s article on The Strouhal Number in Cruising Flight showed how simplified flight waveforms that graph amplitude versus wavelength can be useful for visualizing the Strouhal ratio (fA/U), a dimensionless parameter that tends to fall in the range of 0.2–0.4 during efficient cruising flight.

    For a European Swallow flying with our estimated wingbeat amplitude of 24 cm, the predicted pattern of cruising flight ranges from a Strouhal number (St) of 0.2:

    ... to a less efficient 0.4:

    If the first diagram (St = 0.2) is accurate, then the cruising speed of the European Swallow would be roughly 16 meters per second (15 beats per second * 1.1 meters per beat). If the second diagram (St = 0.4) is accurate, then the cruising speed of the European Swallow would be closer to 8 meters per second (15 beats per second * 0.55 meters per beat).

    If we settle on an intermediate Strouhal value of 0.3:

    We can estimate the airspeed of the European Swallow to be roughly 11 meters per second (15 beats per second * 0.73 meters per beat).

    Three shall be the number thou shalt countAirspeed can also be predicted using a published formula. By inverting this midpoint Strouhal ratio of 0.3 (fA/U ≈ 0.3), Graham K. Taylor et al. show that as a rule of thumb, the speed of a flying animal is roughly 3 times frequency times amplitude (U ≈ 3fA).5

    We now need only plug in the numbers:

    U ≈ 3fA
    f ≈ 15 (beats per second)
    A ≈ 0.22 (meters per beat)
    U ≈ 3*15*0.22 ≈ 9.9
    ... to estimate that the airspeed velocity of an unladen European Swallow is 10 meters per second.

    Oh, yeah, I agree with thatWith some further study, it became clear that these estimates are accurate, though perhaps coincidental.

    An actual study of two European Swallows flying in a low-turbulence wind tunnel in Lund, Sweden, shows that swallows flap their wings much slower than my estimate, at only 7–9 beats per second:

    “Compared with other species of similar size, the swallow has quite low wingbeat frequency and relatively long wings.” 7
    The maximum speed the birds could maintain was 13–14 meters per second, and although the Lund study does not discuss cruising flight in particular, the most efficient flapping (7 beats per second) occurred at an airspeed in the range of 8–11 meters per second, with an amplitude of 90–100 (17–19 cm).

    And there was much rejoicingAveraging the above numbers and plugging them in to the Strouhal equation for cruising flight (fA/U = 7 beats per second * 0.18 meters per beat / 9.5 meters per second) yields a Strouhal number of roughly 0.13:

    ... indicating a surprisingly efficient flight pattern falling well below the expected range of 0.2–0.4.

    Although a definitive answer would of course require further measurements, published species-wide averages of wing length and body mass, initial Strouhal estimates based on those averages and cross-species comparisons, the Lund wind tunnel study of birds flying at a range of speeds, and revised Strouhal numbers based on that study all lead me to estimate that the average cruising airspeed velocity of an unladen European Swallow is roughly 11 meters per second, or 24 miles an hour.

    So they only need turned once to complete the cooking cycle , unlike they tubular fuckers that you get south of the border that continually need rotating to stop them getting cremated .

    like it

  3. #13
    Join Date
    Jun 2014

    Re: Shock lenght question

    Quote Originally Posted by Hodgierex View Post
    like it
    Me too
    What Goes Around..........!!!

  4. #14
    Join Date
    Jul 2005
    Scotland (West of)

    Re: Shock lenght question

    Anyway , back on topic.

    You will need to graft the ZRX stem onto the lower GSX yoke , the upper will need bushed to take up the space between the skinny ZRX stem and the hole in the yoke.

    If you want to fit the original steering damper then a bracket will need fabricated to mount the damper onto the steering head tube.

    A bracket will need made and welded onto the steering head lock stops to prevent the tank from getting dented.

    No need for brackets for the original clocks as it wont have them as it is a track bike.

    You will need a set of risers to clamp the bars onto or you could fit clip-ons to save you the work.

    Take the pieces and build them skywards !

  5. #15
    Join Date
    Feb 2018

    Re: Shock lenght question

    Thank you very much. Hayabusa set up looks Proper ! I have not decided yet, but it is possible ill go this way

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