In my opinion the slipstream distance is still too far/overpowered. I took this screenshot when I was already affected by his slipstream. It started 10m before.
(http://i58.tinypic.com/2eq8j6s.jpg)
That's a very big 10m distance. Lol ;D
But yeah, I know what your saying.... Maybe it could do with setting at about 3 bike lengths, 4 including the rider in front.
There should be a scientific formula for this slipstream effect? How about it Max? This is your arena; it's always great to hear how these things actually work and are worked out. ;) 8)
Quote from: Hawk_UK on May 08, 2014, 11:28:21 PM
That's a very big 10m distance. Lol ;D
But yeah, I know what your saying.... Maybe it could do with setting at about 3 bike lengths, 4 including the rider in front.
There should be a scientific formula for this slipstream effect? How about it Max? This is your arena; it's always great to hear how these things actually work and are worked out. ;) 8)
I've little knowledge in aerodynamics (just the basic stuff). I remember the slipstream being way too important in beta 3 and much better in beta4, but I've heard other respectable opinions that it is still a bit too much.
Notice that it's a pita to evaluate properly as it depends obviously on the speed and (maybe in to a smaller extent) on the bike front section.
You'd need the bike running on a straight at a fixed speed, note down the throttle position, then repeat with a bike preceding you at various distances and with you keeping the throttle open a tthe very same position as before (and bike aligned right behind the other one), then check if the resulting acceleration is acceptable ... in 2 words, no go.
I wouldn't care too much about a scientific approach here: Piboso's model is probably good enough and just needs a little tuning to lower the impact. If a couple of riders with real race track experience agrees on that, I'm for it.
MaX.
Neil spalding will know lol
Tough one..
I would agree with around 4 bike lengths in general..
Me on my oldschool R6 against other oldschool yams and CBR's.. Its hard to tell, a track I race at, Darley moor. Has a very long straight but sometimes I can be tucked in behind someone and still not make any ground.. Sometimes it sucks me right in and straight past!
Depends on the run onto the straight as well I think!
I guess motogp bikes would benefit more from slipstream because of the speed they do?
4 bike length are about 9 meter.
In my opinion its too much.
i would agree 3 bike length out of personal experience where the draft takes a noticable effect.
Another story is when 2 bikes are driving next each other , in this case you´ve got a huge slipstream area (it´s like a bus driving in front of you).
Quote from: C21 on May 09, 2014, 07:27:21 AM
4 bike length are about 9 meter.
In my opinion its too much.
i would agree 3 bike length out of personal experience where the draft takes a noticable effect.
Another story is when 2 bikes are driving next each other , in this case you´ve got a huge slipstream area (it´s like a bus driving in front of you).
+1
Quote from: C21 on May 09, 2014, 07:27:21 AM
i would agree 3 bike length out of personal experience where the draft takes a noticable effect.
At which speed ?
MaX.
sorry but i don´t have a speedo on my track bikes ;)
maybe 180km/h upwards
Quote from: C21 on May 09, 2014, 02:03:23 PM
sorry but i don´t have a speedo on my track bikes ;)
maybe 180km/h upwards
Do you (or Desteban or any other rider with track experience) think/know if the speed makes a diffrence ?
I mean, OK, below a certain speed slipstream is just not there or is irrelevant, but let's say between 200Kmh and 280Kmh ...
MaX.
I think slipstream does not affect bikes very much. In formula 1 you can easily overtake someone with slipstream but in MotoGP you barely gain speed. You're just able to get closer and overtake him in the corner. In GP Bikes you gain 25kmh or so.
I tried to find information about slipstream/draft on Google but I couldn't find any. Then I tried to find a clear overtake (birds eye view) on youtube but I couldn't find a good one...
Quote from: HornetMaX on May 09, 2014, 02:31:27 PM
Quote from: C21 on May 09, 2014, 02:03:23 PM
sorry but i don´t have a speedo on my track bikes ;)
maybe 180km/h upwards
Do you (or Desteban or any other rider with track experience) think/know if the speed makes a diffrence ?
I mean, OK, below a certain speed slipstream is just not there or is irrelevant, but let's say between 200Kmh and 280Kmh ...
MaX.
Yes it does make a difference, more speed=more air resistance you are not slamming into because you are tucked in behind someone. So yeah, big difference comparing let's say 150Kmh and 250+Kmh.. Of course it all depends on how fast your exit from the previous turn was.
Quote from: LoriX on May 09, 2014, 03:10:42 PM
Yes it does make a difference, more speed=more air resistance you are not slamming into because you are tucked in behind someone.
Hmm but that's not the only factor.
Actually my question was more related to the distance the slipstream works on: is it bigger at higher speeds or not ?
Just got a brillant idea, I'll ask my wife (she's into applied maths, parallel computing, PDE etc).
MaX.
Quote from: HornetMaX on May 09, 2014, 03:30:15 PM
Hmm but that's not the only factor.
Actually my question was more related to the distance the slipstream works on: is it bigger at higher speeds or not ?
Just got a brillant idea, I'll ask my wife (she's into applied maths, parallel computing, PDE etc).
MaX.
for me, it depends on the distance: the faster the one in front of you goes, bigger is the quantity of air it moves ( sorry for my italian-english lol ). Just my opinion
Look at 0:50. 4 riders are riding at top speed. The 4th seems to get closer to the 2 guys but not super fast. I think this is a very good example of the slipstream. (Straight, top speed).
https://www.youtube.com/v/BzWf-6UzQUA
If two riders are going at top speed and the second rider in the slipstream has a different gearing ratio than the rider in front, then it is quite possible that the rider in the slipstream cannot catch the rider in front even with the advantage of the slipstream, in fact he could well blow his engine trying to pass the rider in front if there is no rev limiter on his bike. This is just one scenario you have to think about when both riders hit top speed before the rider behind can take advantage of the slipstream effect. So it's not always a case that the rider in the slipstream can overtake the rider in front if they have both hit top speed unless he has something left in his gearing and rev limit to do so.
Quote from: Alby46 on May 09, 2014, 03:39:49 PM
for me, it depends on the distance: the faster the one in front of you goes, bigger is the quantity of air it moves ( sorry for my italian-english lol ). Just my opinion
Hmm ... doesn't work exactly like that.
AFAIK, slipstream is a zone of low pressure practically sucking the following vehicle in. The "quantity of moved air" is not really relevant. Speed is, as the size of the zone depends on it.
MaX.
Its a tough one..
Look at moto3 it seems very important to slipstream the rider infront but it sometimes looks like it takes the whole length of the straight to have an effect.. U usually see the rider behind take a wider entry onto the straight to get a better run for the line if its the last lap..
Faster bikes.. NW200 for eg. Top speeds are increased alot with slipstream!
So I would say it has a bigger effect at higher speed..
Did anybody watch that tv programme.. ''Speed with Guy martin'' the episode where he gets in the trucks slipstream on a pushbike and does about 100mph?
Truck had a huge windbreaker but the air pocket was still very small..
I looked at a lot of onboard videos to find another example but it's difficult to find a clean slipstream. (corner exit, topspeed of the bike,...)
It starts at 2:54
Speed increase at 2:59
https://www.youtube.com/v/Nzvlu8603J8
Arvoss, you won't be able to grab any info from videos: maybe the bike behind was just faster, we don't know at which speed they were etc.
I guess the best shot is to ask our real riders.
MaX.
I can try to watch the data recording next time when I get some slipstream, then I can says something definite.
If I say anything now it wouldn't be more than a guess...
Quote from: Desteban on May 10, 2014, 02:12:50 PM
I can try to watch the data recording next time when I get some slipstream, then I can says something definite.
If I say anything now it wouldn't be more than a guess...
I really doubt we can gather something useful from the data recording, but if you can have a look why not.
I've contacted a more knowledgeable (wrt me) friend of mine, I should come up with some sort of information soon.
MaX.
+1
Quotesometimes looks like it takes the whole length of the straight to have an effect.
Not only sometimes.
I needed the whole star/finish straight to get next to my team mate riding Brno in 2004 to outbrake him. Both bikes had the same gearing and engine are mostly equal. My engine was 2hp up on his one (same dyno, same day).
I posted a few days ago that i would say an increase will be noticable at 3 bike length. If i remember correctly i would take it down to 2 bike length now.....but the speed increase is not that much....the longer the straight the more it will be.....i would say a speed increase between 5-10km/h maximum. Funny when the wind is facing you from the front...you sneak behind the one in front of you then try to overtake him but stuck on the same height of his fairung nose due to the wind...... ;)
Quote from: C21 on May 14, 2014, 07:50:24 AM
Quotesometimes looks like it takes the whole length of the straight to have an effect.
Not only sometimes.
I needed the whole star/finish straight to get next to my team mate riding Brno in 2004 to outbrake him.
At which speed ?
MaX.
Max i told you we don´t have speedos at the track bikes ;)
I can only presume the speed upon the gearing but i have to look into my sheets and run a calculation.
gearing was 15/50 or 15/49 if i remember correctly.
Speed must be 220-230 KM/h i presume.
Running 3rd gear on the beginning of the straight up to 6th gear...
Quote from: C21 on May 14, 2014, 08:35:35 AM
Max i told you we don´t have speedos at the track bikes ;)
Oh, forgot it was you, sorry ::)
All the info I'm finding on the subject is very messed up ... annoying.
MaX.
try and find a video of "speed, with guy martin" was some good slipstream info on that..
Wow, it's really really a PITA that slipstream stuff ...
First part of this article (http://www.recumbents.com/wisil/demma/aero_review.htm (http://www.recumbents.com/wisil/demma/aero_review.htm)), from beginning up to 1st paragraph after the 1st graph.
Results are different for streamlined / poorly streamlined vehicles and I'm not sure where racing motorbikes falls (somewhere in between, probably closer to poorly streamlined case).
Speed is not mentioned, but I'll ask C21 once again :)
For streamlined vehicles you can see some funky stuff: when the following vehicle approaches he gets a benefit but once he gets too close he's worse off.
Also, the front vehicle gets a benefit too once the following vehicle is close enough. This is a bit surprising but makes sense. It is also a know fact in Nascar racing, where two cars running close can go faster than a single one (two-car drafting, or tandem drafting, banned by Nascar in ... 2014 !!!
For poorly streamlined vehicles it seems to be even worse: for the trailer, Cd goes down, then up and then down again.
I'm more and more convinced we don't need this level of detail.
MaX.
QuoteI'm more and more convinced we don't need this level of detail.
Correct but the slipstream effect has to be reduced!
QuoteSpeed is not mentioned, but I'll ask C21 once again
NOOOOOOOOOOOOOOOOOOOO ;D
I know Piboso greatly reduced the slipstream effect from Beta 3 to beta 4/b, but it does seem that the effect does need reducing yet again. Personally I'd say to around 3 bikes lengths of good slipstream tailing off greatly over say the next 3 bikes lengths, but with the effect increasing and increasing as you get closer to give that sling shot feeling just before you pull out to overtake the rider your slipstreaming.
It's great when you engineering/science buffs get together debating these subjects.... It's very interesting and I learn a lot along the way too....
More of these type of debates please guys! ;D 8)