Landracing Forum
Tech Information => Aerodynamics => Topic started by: Roosters on April 16, 2019, 10:23:03 AM
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Hey guys, We have been racing for awhile now and have never really played with full bodywork before! We will be running this bike (APS-BF 250) at speed week. I am looking for a safety check from anyone with experience in this regard (anything stick out as dangerous?) Any Aero tips would be great , before we go to bodywork and paint!!
Thanks!
(http://i66.tinypic.com/2s9au60.jpg)
(http://i66.tinypic.com/2ezh8x3.jpg)
(http://i68.tinypic.com/nl92eu.jpg)
(http://i68.tinypic.com/9pm8ls.jpg)
(http://i64.tinypic.com/2dikh2d.jpg)
(http://i68.tinypic.com/2dv4y06.jpg)
(http://i68.tinypic.com/1072vd2.jpg)
(http://i65.tinypic.com/160zgjo.jpg)
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looks a bit more like APS-BF 1350 rather than APS-BF 250
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Hard to tell looking at the picts but it appears that there is a slight lip at the back of the seat overhanging the rumpass.
I have seen that disallowed in APS.
Nice work, Don
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Its a yamaha 250cc under the skin with a couple of turbos :-D
when the seat back is finished (Wally suggested I raise the seat height as well). The rider wont sit inside of any part of the fairing, the way I read the rules this should be fine? I hope!
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Welcome... You could fair in the opening where you hands are to almost the elbow... Be sure your tail does not exceed the length no matter what sprockets you are running....
The big question will be can you ride it slow and can you transition from start position to riding position quickly.... you don't want to burn up a lot of track getting into position.
Cool Idea 8-) :cheers:
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Generally looks great, but i think you will have a separation problem where the factory joins the fabricated on the sides ,
if the air doesn't stay attached you will probably have a handling problem ,
something like this https://en.wikipedia.org/wiki/File:Vortex-street-animation.gif
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Good job! And good luck. The forearms need to be enclosed. There is a lot of drag there, especially with a 250cc. As Stainless pointed out, is it possible for the rider to get his feet into and out of that position while accelerating? I don't think I could do that. Do some riding tests to make sure. Also it looks like the turbo inlet is right where the the front wheel will be spraying salt. Do you have a filter that can withstand that?
Also, the rear end is pretty blunt. I see you have holes for the rear wheel to pump air into the vacuum, but is it possible to make it come to more of a point?
Don
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Thanks for the feedback guys, Getting in to that riding position is surprisingly easy! we do have some tests planned at a local airstrip.
The tail section ended up a bit blunt do to the shortish wheelbase and the tail section length rules, working with what we had that was all we could do
We can look at tightening up where the ducati bodywork meets the aluminum but the thought was to use the factory vents to pull hot air out from the rad/engine. We would rather have a stable bike though.
The primary turbo inlet will be ducted up into the front nose of the upper fairing (ram air idea).
If it will make a big difference we can enclose the forearm are relatively easily. The goal (and I know it will be hard) is to push this little guy up to 200mph so every little bit helps!
(http://i68.tinypic.com/4j1h5d.jpg)
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Do you have substantial rubber pads under your knees to support them? Otherwise you'll get bounced around uncomfortably especially if the salt is bumpy. Also, how long can your rider hold that position without getting cramps in his/her feet? (I've had cramps in my legs during runs that had me wanting to pull my legs out prematurely.) This photo is before the tail was fully enclosed.
Tom
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Be real careful about the wind (crosswind)! With an full enclosed tail, the bike acts more like a kite than a motorcycle. Instead of the wind pushing you to the side, it tries to push the bottom of the bike out from under you. Wind tunnel test typically only shows the stability when the wind is a headwind.
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Be real careful about the wind (crosswind)! With an full enclosed tail, the bike acts more like a kite than a motorcycle. Instead of the wind pushing you to the side, it tries to push the bottom of the bike out from under you. Wind tunnel test typically only shows the stability when the wind is a headwind.
Ransom,
That is a very interesting effect that I observed at Loring with a side wind. I actually had to lean opposite to the direction I expected. That is, the wind between the mile and the mile-and-a-half hit me hard from the left and I found myself leaning the bike to the left (or the wind was blowing the bike out from under me), but my body to the right to maintain control. I never could figure out why until you just mentioned that phenomena. I didn't try another run until the wind died down.
Tom
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I have a Kamm tail design on my hand formed aluminum rear section on my APS-PG 2000 bike. It so far has performed well with good results in the wind Tunnel. Ransom hit the nail on the head in regard to side winds and how it feels like the lower half of the bike is falling over. You will be able to determine how much of an impact that will make on your design by trial and error. You do not have a flat bottom on the bike so your lean angle in wind should be able to handle any condition you feel comfortable riding in. My bike (and me) do not like side winds in excess of 5-7 MPH
As far as Aero goes, in most organizations in APS you can have a front fender cover 180 degrees of the wheel as long as it is not lower than a horizontal center line through the front axle. Your design is losing aero. As you stated earlier, getting all of your "stuff" outside of the fairing inside the fairing will help significantly. You must make sure you have enough travel between your front fender and the fairing so you have enough travel in your front fork suspension. You also have to have clear non-contact range of motion between the fairing and the fender during inspection as well.
One other item that may or may not impact your design...You have your feet in a position that does not lend them to being used for braking. I'm assuming that means you have a hand operation for your rear brake. That is fine for events at Bonneville but any of the Airstrip racing may require you (depending on speed) to have both front and back brakes. If that is the case they have to be controlled separately. No proportioning valve going to two brake systems. Good luck with your racing endeavor.
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So it sounds like we will only run without wind!, interesting on how it feels like he bottom would be blown out. We measure the lean angle at 25 degrees. This bike will only ever see Bonneville so brakes wont be an issue and it is electrically shifted.
so far the changes that have been recommended are:
taller front windscreen
higher seating
close in forearm area
radius the corners behind the legs
more coverage on the front fender (we had this one cut from running in modified)
So time permitting that is what we will do!
Thanks again
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I am not a motorcycle person but reading this thread reminded me of the Britten and I pulled the book for a re-read (The John Britten Story). They were playing with carbon forks in the early days, homemade engine (no frame), full engine mapping (in the 1990's) etc. Nothing necessarily new but put together to make a unique package. The V1000 bike (attached) was known to pass the factory Ducatis down the back straight on its back wheel. Unfortunately he passed away at 45 so no idea what might have been.
Admittedly that was a V twin built for the Battle of the Twins and BEARS track racing in the '90's, but Brittens also set several world records including the world flying mile record (1000cc and under) at 188.09mph, the world standing start quarter-mile record (134.61mph), the world standing start mile record (213.51mph) and the world standing start kilometer record (186.24mph), all set in 1993 (stats according to MCN).
I don't have the book in front of me here at work but paraphrasing it they observed that the 'barn door fairing' (fully enclosed) referencing the aero-d-zero and aero-d-one earlier bikes, one of which had what look like wings over the forearm area, were slower than the open bike pictured here which is described as a torpedo (fairing, tank, seat) mounted on a blade (wheels, engine etc) and it was asssumed that this was because of turbulent wake off the fully faired bike that the ducted airflow in the 'naked' bike between the riders legs and frame, through the nostrils via the radiator (mouted in line) and directed by the lower splitter etc 'filled in'.
Not making any claims here - just thought it was interesting, and even more so that several road superbikes seem to follow this design today, 25 years on.
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If you're ever in Wellington NZ, it's worth a look.
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Or here: https://www.barbermuseum.org/the-collection/motorcycle-spotlight/
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Actually the comments about Brittens open bike airflow reminded me about the current generation bikes airflow,
Kawasaki H2 and others split the air and create boundary layers, H2 and H2R pick up air in the front and ducts it to the fairing cutout near the hands , and directs air from the riders seat to the undertail
a huge sail to the wind is obviously not the only way to get the air around the bike and rider
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If your going to modify the hand-fore-arm part of the fairing...........think about turning the 'grips' downward which will rotate the riders elbows and shoulders to a much more narrow profile.