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DLRA Speedweek 2019

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  • #16
    17.5 but wouldn't get asked for ID in a pub at 6'1"

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    • #17
      Originally posted by Andy View Post
      I don't even know what 0.004mph is but it's small.
      It's just a tiny bit less than one thousandth of a second. Or two inches if that helps.

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      • #18
        Originally posted by Andy View Post
        17.5 but wouldn't get asked for ID in a pub at 6'1"
        Ah, good one mate...
        Had the same with our two young blokes; eldest ended up at 6'2" and youngest 6'1" in their teens too.
        The 'Old Man'? Well, I topped out at 5'9½" so not sure where the tall genes came from...

        Mal.

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        • #19
          Originally posted by Andy View Post
          Zed's best pass for the week was a 123.170mph average over the mile, the record for his production class is 123.174mph. I don't even know what 0.004mph is but it's small.
          To refine theonetruepath's numbers a bit more, if the two bikes were racing side-by-side and Zed was *exactly* 0.004mph slower when the other bike hits the finish line Zed would be 2.05757708607336 inches/0.0009491579847482414 seconds behind him. Small indeed!


          Java "Go Zed Go!" phile
          Toys! I must have new toys!!!

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          • #20
            Same same here Mal, must be what we feed 'em.

            Good one fellas, I'll let Zed know about the 2" (50mm to him). The best I calculated in my head while driving back was that he needed to be 6.5 meters an hour faster to get the record by 0.001 (which is all you need to beat it by).

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            • #21
              Or 52.26245798626334 mm, which makes it sound a bit bigger.
              But seriously, congratulations on another successful meet, albeit beaten by the weather this time. Even so, the results must give you great confidence for next year.
              I can't stop thinking that the attention to detail demanded by a career in roasting, mixed with a little of that black art that seems to be required, has so much to do with your success on the salt.
              And that Brazen has to be the most impressive coffee maker that I've seen in a campsite! Makes an Aeropress look insignificant.
              Once again, congratulations.

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              • #22
                Each generation seems to be just a little bit taller. My brothers and I were a little bit taller than our old man. My brother's kids are taller again. Better build those those doorways just a bit higher!

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                • #23
                  Originally posted by Otago View Post
                  congratulations on another successful meet, albeit beaten by the weather this time. Even so, the results must give you great confidence for next year.
                  It was a pity we didn't get more runs in better conditions, as luck (or bad lack) has it, some of the downtime for lightning smoked timing gear was during the coolest, nicest morning and would have been faster than any other day for Zed. His 123mph run was at 3pm after a 7 hour wait in the staging lane and would have been way quicker at 8am.

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                  I'm now understanding just how much "the planets need to be aligned" for a great run even with all the right preparation.

                  We did learn a lot from the runs we had and tuning between runs on my bike has resulted in a far better setup, we made lots of gearing changes to Zed's bike during the week and have a better understanding of the "zone" we need to be in. All good positives and we know the bikes will return next year better again.

                  And that Brazen has to be the most impressive coffee maker that I've seen in a campsite! Makes an Aeropress look insignificant.
                  Once again, congratulations.
                  It was surreal to hear a Brazen finished beep that deep into the red dirt. Life's luxuries are a little extra special the more remote you are. The Aeropress does a fine job too and got used on the salt while waiting for a run, made in the back of a ute with a gas burner and a stainless pot.

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                  Emptying the trailer at home we found it had a small air leak that we missed, Zed's rim was black when we packed the bike in, now red dirt coloured and the other end of the bike has some obvious skunk-stripe salt build-up.

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                  Lots of washing already on both bikes, low pressure soaking over and over and a overdose of chain oil before the pull-down and manual clean. I think the snob van will need pressure washing inside and out, so much red/white in every crack and crevice and every surface feels sticky with humidity making the in-ground salt tacky.

                  Ahh the fun of post-race.

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                  • #24
                    Andy, you have to point the exhaust into the wake behind the bike. The faster you go, the more important it is.
                    There was some guru engineer doing testing on fast bikes. It's like a 5% reduction in drag at 200kph. I can't find the paper right now. Maybe it's gone to dark web repository.
                    They were testing with speeds at the end of one racetrack straight, the modified tailpipe bikes were faster, and then slower without the pipe.
                    Even if you don't believe me, make a pipe and take it next year to try. Gotta be worth trying it..

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                    • #25
                      Interesting idea, I had heard of pointing it into the rear rim for a similar effect. Our class rules say the exhaust needs to finish in front of the rear of the rear tyre, point away from the rider and the salt surface. I think where it is now is inside the wake, unlike the previous bike that was outside.

                      My bike also throws a 5 foot flame when backing off (spectacular in the dyno room)

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                      • #26
                        Originally posted by Andy View Post
                        My bike also throws a 5 foot flame when backing off (spectacular in the dyno room)
                        post up a photo if you have one, be awesome to see!

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                        • #27
                          Originally posted by Jackster View Post
                          Andy, you have to point the exhaust into the wake behind the bike. The faster you go, the more important it is.
                          Yep, a major cause of drag is the large trailing area of negative pressure sucking you backwards, anything that fills the vacuum will help.

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                          • #28
                            Originally posted by Mb21 View Post
                            post up a photo if you have one, be awesome to see!
                            Too busy driving the dyno, the bike and the laptop while on the dyno to also get a picture but it's pretty awesome to see.

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                            • #29
                              How much exhaust volume? So glad you asked...

                              Stolen from a engineering forum:

                              Originally Posted by SBBlue (Automotive) - 4 Oct 04 23:46
                              Okay, class. Excellent question, Jaded. Pay attention now, because this will be covered on the test.

                              Several assumptions: 1) This is a gas engine we are talking about, 2) it is a four-cycle gas engine, 3) Combustion will be stochiometric and complete, 4) the compression ratio is about 10:1, 5) the engine is throttled (no variable valve timing), 6) normal aspirated engine (no turbocharger), and 7) volumetric efficiency (the amount of air that makes it into the cylinder during the induction stroke) is 1.00 (actually it depends upon the RPM and intake manifold pressure, but work with me here.)

                              First, it should be intuitively obvious to the most casual observer that the amount of air that passes through the engine in will be equal to the engine displacement times the RPM divided by 2. For an engine of 3 liter displacement going at 3000 RPM, the amount of air pumped for minute will be 4500 liters.

                              That will approximately be the intake volume flow for an engine with the throttle wide open. If we assume that the throttle is only open 33%, the intake volume flow will still be 4500 liters, but the pressure will be one-third of an atmosphere. The equivalent mass of air will be the same as 1500 liters at one atm of pressure.

                              Neglecting the addition of the fuel mass, the mass of the exhaust gas will be the same as the mass of the intake gas. From the ideal gas law we know that the increase in volume of the exhaust gas will be proportional to the increase in absolute temperature. If we assume an intake temperature of 80 deg F, and an exhaust temperature of 1800 deg F (reasonable assumption, depends upon compression ratio), the absolute temperature will be 540 and 2260 deg Rankine, respectively. The volume increase will therefore be 2260/540, or 4.185.

                              For the hypothetical 3 liter engine running at 3000 RPM and full throttle, the exhaust gas volume will be about 4500*4.185, or 18,833 liters/min. At one third throttle the corresponding flow is 6277 liters/min. Since one cubic foot is equal to 28.3 liters, the respective CFM flows will be 665.4 and 221.8, respectively.

                              How about the contribution from combustion products? Assuming stoichometric combustion, there will be one pound of fuel burned for each 14.55 lbs of air. Air is 21% oxygen, so there is 3.05 lbs of oxygen available to burn each pound of gas.

                              A reasonable chemical approximation for gasoline is octane, which has a chemical of C8H18. The molecular weight is (12*8+18*1)= 114.

                              The combustion formula is C8H18 + 12.5 O2 ==> 8 CO2 + 9 H20. For each 114 grams of C8H18, there will be 12.5 moles of oxygen consumed, producing 8 moles of CO2 and 9 moles of H2O. For gas volume purposes, since equal moles of gas produce equal volume, the volume of exhaust gas replacing oxygen will be equal to 17/12.5 = 1.36.

                              The volume percentage of oxygen in air is about 21% (not exact, but work with me here). This volume will be removed, and replaced by exhaust gas with a "volume" of (21*1.36) = 28.56%. The resulting post combustion volume is (79% + 28.56% = 107.56%) of the pre- combustion volume -- assuming no temperature increase.

                              So what do we have? Combining the increase in volume from combustion reactions and thermal expansion, an engine with a 3 liter displacement running at 3000 rpm with the throttle wide open will have an exhaust volume (at 1800 deg F) of 665.4*1.0756 ~~ 715 cubic feet per minute. For the throttle one-third open, the exhaust flow will be 238.6 cfm.

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                              • #30
                                But, you have a supercharged 1 litre, Google says 35psi (wow!). So let's say that's equivalent to a 3 litre aspirated engine.
                                But the kicker is you not at 3000rpm, so triple the figure to 2150cfm.
                                That's 61000 litres per minute!

                                Obviously that is not much compared to the hole you are pushing in the air at 320kph..

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