Post by tom on Jan 11, 2014 14:37:21 GMT 9.5
How many teeth do I need ?
One of the fundamentals in getting a good result in karting is to use the correct gearing for the conditions. The general approach is to ask your engine builder what he recommends as the maximum rpm for your motor, then put a gear on that will hit that rpm number at the end of the longest straight.
That is a good approach, but will not give you the best lap time, and almost certainly will not give you the best opportunity to pass other karts, which is what will win you race meetings. If you look at the recent titles (or any title for that matter), even in a field of 20 karts, the one that wins will rarely finish outside the top 5 in any race, and will have to win at least one race. You NEED to be able to pass other karts.
So how do you work out what gear to run? Firstly you need to know your motor. Each motor will be different in the way it delivers it’s power. Your engine builder should be able to supply you with a dyno-sheet showing peak torque and peak horsepower, or at least be able to give you rpm numbers for peak torque and peak hp.
In between those two rpm numbers is where you want to spend the majority of your time on the track. As most people don’t run data-loggers in dirt racing, it’s harder to know exactly what gear to run.
In my experience, rather than gear for a maximum rpm number, you will get better results from finding out the peak torque number for your motor, and gearing so that you don’t go below this number at any point on the track (ie: exiting slowest corner). It also helps to know this number so that if you are on pole you can try to start at the optimum rpm for your motor.
Now comes the tricky part, and the part that separates the good drivers from the average ones.. If your peak torque for example is 8000rpm, you will look at your tacho coming out of the slowest corner, and if your rpm is 8000 you will be bang on with your gearing. Problem is the likes of a Dave Carruthers etc, will have the same gearing, and be coming out of the same corner at 8400rpm. Good for them, they will go to the pits, take off 2 teeth, and smoke you down the straight in the races.
Point is that even if your motor has a narrow rev-range, if you are slow off the corners you won't be able to pass at the end of the straight, if you gear so that you aren't bogging out of any corner, you can pass if someone makes an error, and by using the power band of the motor out of the corner, you will make a break down the straight so you cannot be overtaken. Rather than just touch on the maximum rpm, you are better off sitting on the max. rpm. for a second or so.
I’ll leave it for another time to explain a few things that you can do to keep corner speed up, but next meeting try gearing for rpm off the corner rather than rpm at the end of the straight, and see how you go!
One of the fundamentals in getting a good result in karting is to use the correct gearing for the conditions. The general approach is to ask your engine builder what he recommends as the maximum rpm for your motor, then put a gear on that will hit that rpm number at the end of the longest straight.
That is a good approach, but will not give you the best lap time, and almost certainly will not give you the best opportunity to pass other karts, which is what will win you race meetings. If you look at the recent titles (or any title for that matter), even in a field of 20 karts, the one that wins will rarely finish outside the top 5 in any race, and will have to win at least one race. You NEED to be able to pass other karts.
So how do you work out what gear to run? Firstly you need to know your motor. Each motor will be different in the way it delivers it’s power. Your engine builder should be able to supply you with a dyno-sheet showing peak torque and peak horsepower, or at least be able to give you rpm numbers for peak torque and peak hp.
In between those two rpm numbers is where you want to spend the majority of your time on the track. As most people don’t run data-loggers in dirt racing, it’s harder to know exactly what gear to run.
In my experience, rather than gear for a maximum rpm number, you will get better results from finding out the peak torque number for your motor, and gearing so that you don’t go below this number at any point on the track (ie: exiting slowest corner). It also helps to know this number so that if you are on pole you can try to start at the optimum rpm for your motor.
Now comes the tricky part, and the part that separates the good drivers from the average ones.. If your peak torque for example is 8000rpm, you will look at your tacho coming out of the slowest corner, and if your rpm is 8000 you will be bang on with your gearing. Problem is the likes of a Dave Carruthers etc, will have the same gearing, and be coming out of the same corner at 8400rpm. Good for them, they will go to the pits, take off 2 teeth, and smoke you down the straight in the races.
Point is that even if your motor has a narrow rev-range, if you are slow off the corners you won't be able to pass at the end of the straight, if you gear so that you aren't bogging out of any corner, you can pass if someone makes an error, and by using the power band of the motor out of the corner, you will make a break down the straight so you cannot be overtaken. Rather than just touch on the maximum rpm, you are better off sitting on the max. rpm. for a second or so.
I’ll leave it for another time to explain a few things that you can do to keep corner speed up, but next meeting try gearing for rpm off the corner rather than rpm at the end of the straight, and see how you go!