Hairpin turn in low hp kart

Can you elaborate? I don’t quite follow.

The industrial 4 strokes eg. Honda 270 have a much 'flatter 'torque/ revs curve compared with a kz so that these engines will pull well over a fairly wide proportion of their rev range. Max torque around 3000 rpm ,serious drop off under 2000 and over 4000.
I wouldn’t think a commercial rental operator would want to gear for more than 5000 max .which might well bring the revs at that track down to below 2000 if the clutch is engaged.
Imo a 100 cc 2 stroke with direct drive ( no clutch) would struggle even more than the 270 honda round that track due to the apparent variation in top track speed to hairpin speed.
Afterthought:
Don’t rental karts usually run with the engine governor fitted.? which would mean 3,600 rpm. max!

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Ah ok that makes sense. Thank you. So basically, in order to preserve their rental fleet, they are likely compressing the useable range of the engine. Coupled with a turn you can’t gear for… whole lotta nothing.

Very similar to driving direct drive with a 2 cycle. My technique, the day I learned how to drive a kart, in a turn very similar to what you have, River kart track in Herndon California 1969, was to go “straight” into the turn, breaking as late as possible, start your turn, and get back onto the gas as soon as possible. At the speeds and the horsepower that you’re talking about, you should be able to get back on the gas almost as soon as you start your turn. I set fast time, new track record, that day in Mc 91 and won all 3 heats. The race was called the “Coca-Cola race”. Kind of a big attendance race. Almost a Regional.

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Since it may be impossible to break grip under acceleration alone (I am assuming) I may be wrong about feeding it in. It may be just as effective to go flat as soon as possible in that it’ll take a few for the kart to speed up by which time you are straight. There may not be enough power to even have to worry about little traction loss moments.

Pavle,
This might be very useful. The karts are very heavy with the extra safety stuff. If they have differentials this doesn’t apply. Try leaning outwards (left) as you turn here. Hang your weight over the planted wheels on left.

Also this thread has some info in it that isn’t exactly to your question but possibly helpful. Accessing peak performance
It’s not about how to take a turn but rather more about thinking about speed and there’s stuff in there that is directly related to this. Take a good look at the writings of Warren Chamberlin in that thread, he offers some insights that are exceptional.
Another thought: we have a rental kart racer from Holland named Matthijs who likely has rental kart mastery. @Matthijs_Hofman He runs and races a rental kart series.

Completely truth

This is also one thing I did not really mention at all, but I feel almost no grip loss, no rear end twitching when applying throttle, except in this this corner, where most people actually spin:

Slika

Yes, I read a lot about this and I am really keen on trying this out at the track, will try it out on Thursday, it is really flipping hot right now, some rain should pour on Wednesday, I really want to see the effect. :grimacing::grimacing::grimacing: It should theoretically lift the inside rear wheel and therefore increase kart rotation, right?

It will in theory allow your inside wheel to stay “up” longer allowing for a free turn. You definitely don’t want the inside wheel coming down as you will bog hard.

This is familiar. Did you happen to ask on r/karting at one point? I recognize this wacky complex. That’s a funny turn at the end of a fast bit. There’s a series of low speed turns so how fast you go in seems to be less important. It kinda looks like you can karate chop late apex straight down! I exaggerate but I sure would try to see how much I can ignore those bends.

You might be simply braking/slowing too much. What happens when you carry more entry speed?

Rental karts have a pretty linear torque band, it’s just very low.

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Well it can be chopped but it is really hard to maintain stability and to keep the momentum, as kart is heavy and carries a lot of speed into weird sequence of low speed corners. I tried going over it, it doesnt do much, but what I found more useful is just glazing it, just a tiny ride. It helps the turn in after so much speed is carried into it, and it actually has solid amount of grip as paint is fading slowly. The thing is to clip the white lines that are painted like 5-8cm from apexes and avoid riding apexes, as they just bounce you off in those low speed corners and destroy your momentum.

Was not asking on r/karting but there are probably people also struggling on these weird looking bits haha

It happens to slow down too quickly as karts tend too have enormous difference between each others. So if you hop into a kart that has brakes that lock the moment you press them, it is hard to even keep the control of the kart in almost every corner, so braking earlier is quite a common consequence in first few laps.

If I try to carry more speed, I get a lot of understeer and my line tends to go towards the tyres, requesting more brake pressure and momentum loss. Or you can simply end up crashed as many do. That hairpin is veery sharp and causes so many problems, almost every session.

I wish we could get context. Their darn website doesn’t allow you to paste their pictures. If I am not mistaken, this turn is VERY narrow, yes? If you had to guess base speed at apex?

If you are referring to a hairpin, looking at telemetry from another guy, similar line and laptime in general to mine, I would say around 34-36kmph at the middle of the corner, at the apex.

If you meant the turn I circled at the map, as a spinning point, then I am not sure, but over 47-50 kmph for sure as the max speed ar the straight is about 60-65 kmph.

I mentioned both, just incase

21-22 mph. So that’s probably like lightpole at E-town. The interior kerb radius appears similar. That’s plenty fast enough to keep a wheel up, I’d think. I’m on and feeding well before apex there. Flow that turn.

Only difference I noticed while watching some replays is that my track is much more narrow in comparing to E-town. But yes, radius seems, to be the same and corner in general.

Let me just ask, how much leaning would you recommend and when to start doing it, in what part of the corner, before or at the apex?

Dear Pavle, I haven’t read all of the comments (I know I should but I’m at work) but I saw Dom bringing me in the discussion. So my apologies if I advise something that is being mentioned by someone else!

I watched the footage from 1:19 to 1:34. You will always struggle in slow corners with rental karts because it takes time to get up to speed again, but I feel there is something to gain. I have the impression that you can try to get to the outside of the entry (left side of the track) earlier than you do now (I know it’s not your footage, but my comment is based on it). You do reach the outside of the track, ready to turn in, but the center of gravity is not yet on the left side of the kart. Probably even leaning a bit towards the right. If you reach the outside of the entry two or three yards earlier, you can already start moving the COG towards the outside of the turn (the left) with minimal steering input towards the right. I watched the clip without sound (again, I’m at work) but I have the impression that the driver is sliding a bit, rubbing of speed and revs. I think that is because the weight is swinging from right to left while turning in (just like a sail on a boat can jibe/gybe) causing the rear tires to slide. Please let me know if it makes any sense.

Thanks Dom for the heads up!

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I think you are right on the money. I was thinking about this very often right on the track but I assumed that it “could not have that big of an impact, speeds are not too big”, trying to explain to myself why I kept on going very wide on exit, thinking it will ruin my momentum if I turn in more aggressively. Since I had no one to really approve or correct me about it until now, I was doing that most of the time. But now when you mention COG swinging, it really makes sense. I usually feel that I close up to the that left apex too late and that I am kind of attacking it instead of going parallel to it.

Deo

Tried to visualize it through paint, my line looks something similar to this, exaggerated a bit as it is not such a deep line and there is no sharp left turning, but similar.

I did not feel it can cost me time but it certainly made me uncomfortable because after quick left turn, I had to get back to the left side, while doing so, prepare myself for braking and brake in very short amount of time and there was immediate turn in point afterwards. It looks like bit too much for a kart and tyres in those 50m. I will certainly try out later turn in for a tighter line at the exit and will post the experience here.

Just to make sure I understood correctly, you are saying something like this should be the line (paint pro coming):

Deo%203

Just a sketch of course but the idea is like that I assume.

I feel a lot of things when I am on the track but I often can´t remember everything or just don´t know how to express what I am feeling, especially here as I am not a native English speaker and I need to decode the phrases sometimes, so with pictures, I am just making sure I got your point completely :sweat_smile:

Good to hear we might be onto something. I’m not a native English speaker as well, but I think I understand you.

I read some things in this thread about being aggressive and all, but I don’t think you need to do that much. I think when changing COG goes fluently, the kart will do the work for you! I find @Terence_Dove’s book a very interesting read on this subject.

I think your red line is a bit too extreme. Not only because you lose speed in the fast left hander, but also because you are effectively making a straight between the two turns, meaning the COG is going back to neutral. That’s a waste, because it takes time and effort to move the COG. If only you can find a way to blend the fast lefthander into the tight righthander. I think it can be done by steering towards the left edge of the track just a few yards earlier, allowing yourself to (immediately) steer very slightly to the right before the actual turn-in. In that way the COG is already moving towards the outside of the kart where it should be. When you then do the actual turn-in, I bet the kart will react immediately without much hassle.

It’s a similar theory as driving a (motor)bike. A bike will only turn after you move the COG (your body) to the inside. A kart (or car) works the same way, only the COG must be on the outside. Hope this helps!

Your original orange line looks better. I don’t know that the line really changes that much. I think Matthjis is talking about weight transfer in a different way but towards the same end.

Loaded flow. Link the feeling of the run out from the prior turn smoothly into the next.

Yeah, maybe I’m using ‘COG’ and ‘weight transfer’ wrong. Hope I’m not confusing things.