" My seat is like swiss cheese from testing this year,"
Can I suggest a little maths and measurement for the occasion, which might help with the swiss cheese problem.
First, weigh your kart without fuel and without driver.
Lets assume that the kart weighs 83kg (my Formula Blue) and the weights are 50kg rear, 33 kg front.
Measure the wheelbase (centre of rotation rear axle to centre front axle) Mine is 1040 mm (it can be anywhere between 1010 and 1270, depends on the kart)
calculate the Kart moment arm (weight of kart times wheelbase), Here it is 83*1040 = 86320kgmm.
Calculate balance. rear weight / total weight=50/83=0.60241 or 60.2 percent.
Calculate CofG. 0.60241 *1040 mm= 626.506 mm from front CoR or 413.494 mm from CoR rear. (and if you have a 50mm rear axle it's 413-25 =388 mm from the axle.
Calculate CoG moment:= 0.60241* 86320kgmm= 52000kgmm. (Confirm ktweight * CoG= 83*626.506 =52000kgmm.
Weigh Driver in race suit (Me=84.5 kg)
Calculate Driver CoG. (me, a point 300mm from my back opposite my navel, about 7 cm in front of my navel (because my legs stick out in front when I'm sitting)
Total driver moment arm = driverweight * wheelbase = 84.5*1040 = 87880 kgmm
Combined moment arm =kartmomentarm + driver moment = 86320+87880= 174200 kgmm
Decide the ratio you want to start at; say 55:45 R:F.
the desired moment arm is 55%* combine moment arm=95810 kgmm
We know the kart CoG moment is 52000 so the driver placement moment (DPM) is 95810-52000 = 43810.
Therefore the driver COG is placed at DPM/Driver Weight= 518.4615 mm from the front CoR or 521.5 mm -25 = 496.5mm from the rear axle.
However since the driver cog is 300mm ahead of my back, the seat back is 496.5-300= 196.5mm from the rear axle at the horizontal point.
If I rework the figures for 56% rear balance then I get a seat position of 175.9 mm a difference of 20.6 mm.
In other words, for each 1% to alter the balance, I have to move the seat 20 mm.
To confirm 1% of combined moment = 174200/100=1742 kg mm
1% movement (by the driver)=1742/84.5= 20mm.
This should allow you to calculate and place your seat without the swiss cheese effect.
Something else to remember. If you place a 2kg weight down by the front rail 200mm in front of the front CoR, the effect is 1040+200mm * 2kg= 2480 kgmm. That's 1.4% forward for an 84kg driver
A bit complicated perhaps (it's easy with an Excel spreadsheet) but it should help you decide wher the holes should go in the first place or how much lead to use where to simulate moving the driver.
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Rotax maxing out at 1200 rev by 'fayying' (20 Aug 2012 @ 11:40)
