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Messages - Allen

31
Tracks / Re: Snetterton..
June 10, 2014, 01:32:13 PM
Alex had a reputation for being a miserable old git... actually not deserved at all (if you knew him).. and somewhat more than a good welder, a good engineer (did his own tuning work including big bore kit for TZ350s and designed his own chassis for a 250 Rotax)

and actually it might have been Cros and not Digger at the last meeting on the old circuit... it was a while back (and I certainly don't have the program from that meeting.. but might have some pics somewhere... hmm, that would take a while to go through dads old pictures to find them.. but that will have to wait as I have to do some work otherwise I don't earn any money..)
32
Physics / Re: Prototype gp500 physics model
June 10, 2014, 01:04:48 PM
EdouardB , highly simplified, two strokes tend to have a smaller, peakier power band to play with that probably makes it harder to hold a controlled slide... having said that, it does depend an enormous amount on what the tyres are designed to do whilst sliding, a radial should be worse in that regard and usually a little bias ply helps. In tyre terms I'll take a tyre with a good feel and a forgiving nature over a tyre with slightly better peak grip and fall off a cliff slide, any day.. Take the TZ350, depending on how the one you've ridden was set up (what pipes, carbs and barrels etc) it could be anything from reasonably docile to extremely peaky (the one I rode had Lectron flat slides, F Barrels, and F2 pipes that gave it a nice easy power delivery, when we ran it as a 250 it was on original pipes (G Barrels and a smaller set of lectrons) and was really quite peaky. My Armstrong on the other hand I always ran with the peakiest power delivery it gave (wider opening disc valves and a set of pipes with a narrower power band for more top end), but it was always easier to control slides with the Rotax engine, possibly due to the fact it fires both cylinders at the same time (effectively like a 250 single)
I never raced 4 strokes (the only 4 stroke I ever took on track was a classic 250 K2 Honda with around 25-30bhp.. still outran a YVPS 350 Yamaha around Snetterton.. actually I tell a lie, I did intend to race a CBX550, but gave it up as a bad job after testing it once... and the thought of the cost of rebuilding if I bent it put me off)... but the majority of my road bikes have been 4 strokes and I have been known to get the back end moving about whilst riding on the road (I'm not really a nutter, I just like riding fast)

Max, the graphs, yep wonderful, but it's extremely hard to measure anything other than longitudinal grip/slip for obvious reasons, that doesn't mean that same slip/grip doesn't apply in any other direction. Simply put, if your tyre is spinning (so it has any longitudinal slip) and the bike is leaned over, it's pretty much a given that the tyre must be moving sideways as well (would be lovely if it didn't as you would never be able to get high sided!). It is possible that the grip fall off needs to change (again you can exchange peak for fall off and get a better, more forgiving tyre that is just as fast but easier to cope with (so more sliding but less falling off).
At the end of the day you can do as much maths as you like, it doesn't really help to get to a point of being able to "ride" better in a sim with no haptic feedback.. and riding a bike really is all about feel (dumb as it may sound, I'd really like to see some feedback, and the removal of the limit on lean angle... if I want to ride off the edge of the tyres, I should be able to.. but I should get enough feedback to tell me I'm about to, so I don't... )
33
Physics / Re: Prototype gp500 physics model
June 09, 2014, 09:34:47 PM
OK Max, friction circles etc... .... it's just that whilst trying to simplify the basics of traction control, it's obviously NOT that simple, but the basic premise of max grip is achieved with around 5% slip as a total of grip slip ratio holds (so if you have a neutral throttle on and a nice two wheel drift, don't expect to be able to add any more throttle unless you can stand the bike onto the fatter part of the tyre first), first principle of trail braking, more lean = less brake, first principle of acceleration less lean = more throttle (up to a point.. ). And yes as a tyre wears the grip changes and so do the traction limits,  so as anyone who's wound open a superbike whilst bolt upright on a freezing day with a relatively worn tyre knows, every tyre has a limit... ultimately the way a tyre slides past it's grip limit is what gives a good feel (decent suspension setup helps there too).
An honest opinion, TC should be banned, it teaches bad riding practice (and we all know what happens when it fails... don't we Mr Pedrosa!)


grT, Yes I have GP500, yes it's easier to initiate and hold a slide and yes, I think the one drop off with GP-Bikes is and always has been (at least for the last 6 years I've been trying it) the lack of any rumble to hint at traction limits, I've tried several times to play with a wheel/direct lean, etc.... and it really does nothing for me.. but then I have never managed to get the hang of the on board view either (again some feedback would probably help that too)

34
Physics / Re: Prototype gp500 physics model
June 09, 2014, 07:08:57 PM
Quote from: HornetMaX on June 09, 2014, 06:14:22 PM
Quote from: Allen on June 09, 2014, 06:10:08 PM
I mean it's easier to feel IRL than see it and it's certainly easier to control IRL than it is in a sim with no haptic feedback (although if the traction control is set to give 5% slip, it should always happen anyway). As soon as I feel the bike start to move I would be adjusting the weight I'm putting on the pegs and bars and shifting around to keep things rolling without having to back off the throttle... which is reserved for those moments when things have got really out of shape!
OK, I do agree with you then: lack of feedback is exactly the reason I was pointing as #1 to explain why sliding is hard in GPB.

MaX.

P.S.
I doubt traction control can be set in terms of x% slip, it's surely much more complex than that.

I'd hope that that is precisely what the TC system is doing, if I call for 100% throttle it should give me the maximum amount the tyre will actually transmit (excluding any consideration of wheelies etc) and that should be around 5% slip. if that happens to correspond to actually being 50% throttle, then that's what I'd expect (a few years ago Michael Rutter said something along the lines of he found it hard to persuade himself to just open the throttle 100% and trust the TC to not just give him 100%... ).

It would actually be interesting if Piboso could output both rider applied and ecu applied throttle.. then you could see just how much the TC can cut things
35
Tracks / Re: Snetterton..
June 09, 2014, 06:16:48 PM
My pleasure...

I'd agree on Thruxton... another fast sweeping circuit (first time I ever got a knee down was at Thruxton, going through church onto the back straight... and that was without any knee sliders.. yeah, I'm that old  ;))
36
Physics / Re: Prototype gp500 physics model
June 09, 2014, 06:10:08 PM
Quote from: HornetMaX on June 09, 2014, 04:38:09 PM
Quote from: Allen on June 09, 2014, 04:26:51 PM
As someone who raced 2/350 machines in the 80s (TZs and Rotax 256 engined) I can say without any doubt it is a lot easier to feel yourself sliding a bike on the exit of a corner than to see another rider doing it in front of you
Just to be sure I get your point right, you mean that it's easier to control a slide being on the bike (for real) than watching it sliding (like in a simulation) ?

MaX.

I mean it's easier to feel IRL than see it and it's certainly easier to control IRL than it is in a sim with no haptic feedback (although if the traction control is set to give 5% slip, it should always happen anyway). As soon as I feel the bike start to move I would be adjusting the weight I'm putting on the pegs and bars and shifting around to keep things rolling without having to back off the throttle... which is reserved for those moments when things have got really out of shape!
37
Physics / Re: Prototype gp500 physics model
June 09, 2014, 04:26:51 PM
Quote from: EdouardB on June 06, 2014, 03:00:12 PM
Tracey, have you ridden the 1000 on GP bikes a lot? I think they have the right amount of powerslide. I'm strongly against putting more powersliding in for those bikes.

Also, I (respectfully :P) disagree with your comment "To an extent and to a degree powersliding and rear wheel steering is an integral part of the skills required to get a racing motorcycle round a race track at a competitive pace and lap time."

In over 100 trackdays, I've never seen a rider in front of me do a huge powerslide like you see in motogp or in video games. Including race winners. I've seen a lot of guys slide consistently at the exit of a turn, but it was more a wobble than "rear wheel steering" or a long powerslide.

Also, in the 500, very very few people actually managed to powerslide without crashing. Maybe 5 riders maximum per year. When I went to see the Assen 500 qualifications in 2000 and 2001, I remember only 4 or 5 riders doing proper powerslides: Rossi, Biaggi, Capirossi, Barros, and sometimes Checa.

So I think the amount of powersliding in GP bikes is fine.

As someone who raced 2/350 machines in the 80s (TZs and Rotax 256 engined) I can say without any doubt it is a lot easier to feel yourself sliding a bike on the exit of a corner than to see another rider doing it in front of you (unless you happen to be the poor sod following a nutter who is taking a long look over their shoulder whilst leaving a black line on the road... ). Modern tyres are no different, they get maximum grip when slipping around 5% and that 5% is what you feel through your arse cheeks...
38
Tracks / Re: Snetterton..
June 09, 2014, 03:47:08 PM
As a slight correction to grT, it was still called Russells chicane even before they castrated it. And the version that is available for GP-Bikes (rework of Lazercutters rf1 track I believe, judging by the too flat bombhole) is from after they opened it up a bit. If you look on google maps and see the satellite image, the two green areas around the chicane show where it went in 1990 when they first put it in... it was much tighter (I did hear that the F1 teams complained it was too tight!). The original 1970s-1990 chicane was actually a very fast sweeper, fourth gear, grabbing fifth on the exit . The reason they changed it was because there was just an Armco on the side of the track to separate Russells from the pit lane (but then the bombhole had no run off either). As an aside, they nearly had to delay the start of the 1989 Willhire 25 hour race (that's not a typo) to repair the Armco at that very place... and the man doing the repairs was none other than TT winner and Ex GP racer Alex George (he has a recovery firm based near the circuit and used to do recovery for the car racing, as well as having his race shop in the paddock. His ex boss the head of Honda Racing UK, who's name has completely slipped my mind at the moment, also happened to be the manager of Snetterton circuit at that time).
I could also mention the last time the long circuit was used, Phil Read was a major pain in the arse and kept asking the marshals for the track to be swept (it was used about once per year by then) and Wayne Gardner gave every one a good laugh pulling monster wheelies on a Moriwaki Kawasaki... and yes the hairpin was one reason they stopped using it, as there was no run off (just a large earth bank that I remember seeing some poor sod fly straight over when his brakes failed!)