Physics Help

A racing kart goes around a 60 ft radius turn at 40 mph. What is the lateral acceleration of the kart in G's? I should be able to solve this in my sleep, but too much time has passed since graduation :) Don't make me dig out the text books, please! -- Pat Dotson

a=v^2/r

I>A racing kart goes around a 60 ft radius turn at 40 mph. What >is the lateral acceleration of the kart in G's? I think it would be done as follows: Velocity=40mph=about 17.9m/s 60ft=about 18.3m Accel. cent.=velocity^2/radius Acceleration centripital= 17.9^2/18.3 17.5m/s^2 / 9.8m/s^2 About 1.8g's. Can anyone else verify my answer? Racer X Veteran Sim Racer #4 Corvette C5-R in the GTIC #24 Monte Carlo in the DORL Victory Lane- http://www.geocities.com/MotorCity/Speedway/1423/

Pat... Centripetal acceleration = v^2 / r = (40 miles/hr x 1.47 ft/sec / mile/hr)^2 / 60 ft = 3442 ft^2/sec^2 / 60 ft = 57.4 ft/sec^2 x 1 G / 32.2 ft/sec^2 = 1.8 G Mine were handy. ;-) Jack "Pat Dotson" <[email hidden]> wrote in message news:[email hidden]... A racing kart goes around a 60 ft radius turn at 40 mph. What is the lateral acceleration of the kart in G's? I should be able to solve this in my sleep, but too much time has passed since graduation :) Don't make me dig out the text books, please! -- Pat Dotson

Thanks for the help guys! Now, just to clarify, the 1.8G means that the lateral force acting on the CG of the kart/driver is 0.8 X total weight. Correct? On a side note, I would have guessed that the G's would be between 1.8 and 1.9. This is probably all that a kart is capable of generating regardless of speed or turn radius. I've got a new oval track racing kart on the way for this summer. What I want to do is determine the left side weight percentage I need, so that while cornering, the weight is distributed 50/50 between the right side and left side tires. This should be a straightforward calculation once I measure the vertical center of gravity of me in the kart. BTW, LTO go kart setup is pretty interesting. I always felt like I had a pretty good basic knowledge of car setups, and most of it transfers directly to kart setup. Thanks again, Pat Dotson Pat Dotson wrote:

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> > A racing kart goes around a 60 ft radius turn at 40 mph. What > is the lateral acceleration of the kart in G's? > > I should be able to solve this in my sleep, but too much time > has passed since graduation :) Don't make me dig out the > text books, please! > > -- > Pat Dotson

Pat Dotson <[email hidden]> wrote in message news:[email hidden]... > Thanks for the help guys! > > Now, just to clarify, the 1.8G means that the lateral force > acting on the CG of the kart/driver is 0.8 X total weight. > Correct? Er... no, it means the lateral force is 1.8 x total weight. It also means you've got tyres coated in glue; or you're pulling some serious downforce; or you've got Magnatraction(tm)! Seriously, are you sure that the radius of the racing line is that small - or is that radius to the centreline of the track? 1.8g without wings is bloody amazing - 1.2 is usually about all that's possible. > On a side note, I would have guessed that the G's would be > between 1.8 and 1.9. This is probably all that a kart is > capable of generating regardless of speed or turn radius. I'd be impressed... > I've got a new oval track racing kart on the way for this > summer. What I want to do is determine the left side weight > percentage I need, so that while cornering, the weight is > distributed 50/50 between the right side and left side > tires. This should be a straightforward calculation once > I measure the vertical center of gravity of me in the kart. Yup, that should work fine. Jonny

>Now, just to clarify, the 1.8G means that the lateral force >acting on the CG of the kart/driver is 0.8 X total weight. >Correct? .8*total weight+total weight Racer X Veteran Sim Racer #4 Corvette C5-R in the GTIC #24 Monte Carlo in the DORL Victory Lane- http://www.geocities.com/MotorCity/Speedway/1423/

"Pat Dotson" <[email hidden]> wrote in message news:[email hidden]... > Thanks for the help guys! > > Now, just to clarify, the 1.8G means that the lateral force > acting on the CG of the kart/driver is 0.8 X total weight. > Correct? No. The lateral force is 1.8 x total weight, acting on the kart/driver and pointing in the direction of the centre of the turn.

Oops! Let me re-check the radius. I thought 1.8 looked funny. I thought it should be 0.8 or 0.9 at most. Jonny Hodgson wrote:

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> > > Now, just to clarify, the 1.8G means that the lateral force > > acting on the CG of the kart/driver is 0.8 X total weight. > > Correct? > > Er... no, it means the lateral force is 1.8 x total weight. > > It also means you've got tyres coated in glue; or you're pulling > some serious downforce; or you've got Magnatraction(tm)!

"Pat Dotson" <[email hidden]> wrote in message news:[email hidden]...

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> Thanks for the help guys! > > I've got a new oval track racing kart on the way for this > summer. What I want to do is determine the left side weight > percentage I need, so that while cornering, the weight is > distributed 50/50 between the right side and left side > tires. This should be a straightforward calculation once > I measure the vertical center of gravity of me in the kart.

Are you sure that is what you want? I don't know about oval karts but on a normal kart you want as little weight as possible on the inside rear wheel because you have no differential, if you have weight on the inside rear it 'fights' with the outside wheel, the tighter the corner, the worse this is. At some corners you will even see people leaning out to lift the inside rear. > BTW, LTO go kart setup is pretty interesting. I always > felt like I had a pretty good basic knowledge of car > setups, and most of it transfers directly to kart setup. It is very interesting but the differential does cause 'unusual' steering affects which you don't usually get on road cars, you may if you have a LSD or locked axle however. Paul --- Outgoing mail is certified Virus Free. Checked by AVG anti-virus system (http://www.grisoft.com). Version: 6.0.313 / Virus Database: 174 - Release Date: 03/01/02

That concept is used on regular karts. I read about it on some web site, and it had me screwed up all last summer! :) If you are going LTO on an oval, you run stagger on your rear tires. The LR wheel doesn't have to unload to go around a corner. You do, however, have to turn the wheel to the right going down a straight, just like in N4 :) Yea, my current theory is that while cornering, you want the weight 50/50 at both ends of the kart, and use stagger, caster, camber, crossweight, etc., to make the kart turn. On an oval, if you transfer all the rear weight to the right rear tire, you overwork that tire. I was lifting my RR tire for a while when I had my cross weight set really low. Trust me, it isn't the fast way around an oval! -- Pat Dotson Paul Laidlaw wrote: > "Pat Dotson" <[email hidden]> wrote in message > > I've got a new oval track racing kart on the way for this > > summer. What I want to do is determine the left side weight > > percentage I need, so that while cornering, the weight is > > distributed 50/50 between the right side and left side > > Are you sure that is what you want? I don't know about oval karts but > on a normal kart you want as little weight as possible on the inside rear > wheel

I re-checked everything. It all looks correct. The radius isn't much more than 60'. Speed is close to 40 mph. There is slight banking to the track, but not much. I'll have to think about it some more. Is there some part of this equation that is being left out? -- Pat Dotson Pat Dotson wrote: > > Oops! Let me re-check the radius. I thought 1.8 looked > funny. I thought it should be 0.8 or 0.9 at most. > > Jonny Hodgson wrote: > > > > > Now, just to clarify, the 1.8G means that the lateral force > > > acting on the CG of the kart/driver is 0.8 X total weight. > > > Correct? > > > > Er... no, it means the lateral force is 1.8 x total weight. > > > > It also means you've got tyres coated in glue; or you're pulling > > some serious downforce; or you've got Magnatraction(tm)!

Pat Dotson wrote: > > I was lifting > my RR tire for a while when I had my cross weight set > really low. That would be a trick, eh? I meant LR tire. -- PD

Pat, You've got the right idea. I raced karts on clay ovals back in the early to mid 90's and had a blast. I didn't have an offset chassis but did offset the seat as far to the left as possible. It really helped to have one of those oval-type seats that wrap around your right side rib cage too. Made the longer heats a lot more comfortable. If you're running on clay (as opposed to loose dirt) you'll probably want to try running a larger/wider RF tire (helps overheating). I used to run a stagger on the rear with as narrow a LR tire as I could get. Caster stagger will also help you get the thing turned (just like in N4). Make sure that your nerf bars, bodywork, etc. aren't binding up the chassis either. Keep them as loosely mounted as possible. You'll need as much chassis flex as you can get. Not a bad idea to be able to adjust the spindle height of the RF as you're driving either to adjust the crossweight as the track changes. I used to have a U-joint at the top of the spindle attached to a rod that ran back to the steering uprights. Put a crank handle on the end and you can tweak all you want. Wayne Hutchison "Pat Dotson" <[email hidden]> wrote in message news:[email hidden]...

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> That concept is used on regular karts. I read about it on > some web site, and it had me screwed up all last summer! :) > > If you are going LTO on an oval, you run stagger on your > rear tires. The LR wheel doesn't have to unload to go > around a corner. You do, however, have to turn the wheel > to the right going down a straight, just like in N4 :) > > Yea, my current theory is that while cornering, you want > the weight 50/50 at both ends of the kart, and use > stagger, caster, camber, crossweight, etc., to make the > kart turn. > > On an oval, if you transfer all the rear weight to the > right rear tire, you overwork that tire. I was lifting > my RR tire for a while when I had my cross weight set > really low. Trust me, it isn't the fast way around an > oval! > > -- > Pat Dotson > > Paul Laidlaw wrote: > > "Pat Dotson" <[email hidden]> wrote in message > > > I've got a new oval track racing kart on the way for this > > > summer. What I want to do is determine the left side weight > > > percentage I need, so that while cornering, the weight is > > > distributed 50/50 between the right side and left side > > > > Are you sure that is what you want? I don't know about oval karts but > > on a normal kart you want as little weight as possible on the inside

rear > > wheel

I ran a straight rail chassis this summer, and actually got it running pretty well. Everyone runs offset chassis on ovals now though. Most run 8" wide tires on 10" rims on both the RF and RR, so overheating the RF isn't much of an issue. All kinds of in-car chassis adjustments are illegal, so that's out of the question. I'm buying a 2002 Ultramax Blaze. It has adjustable caster and camber, Ackerman, and a weight jacker on the LR bearing hanger to adjust cross weight. Should be a fun summer. -- Pat Dotson Wayne Hutchison wrote: > > Pat, > > You've got the right idea. I raced karts on clay ovals back in the early to > mid 90's and had a blast. I didn't have an offset chassis but did offset the > seat as far to the left as possible. It really helped to have one of those > oval-type seats that wrap around your right side rib cage too. Made the > longer heats a lot more comfortable. > > If you're running on clay (as opposed to loose dirt) you'll probably want to > try running a larger/wider RF tire (helps overheating). I used to run a > stagger on the rear with as narrow a LR tire as I could get. Caster stagger > will also help you get the thing turned (just like in N4). Make sure that > your nerf bars, bodywork, etc. aren't binding up the chassis either. Keep > them as loosely mounted as possible. You'll need as much chassis flex as you > can get. Not a bad idea to be able to adjust the spindle height of the RF as > you're driving either to adjust the crossweight as the track changes. I used > to have a U-joint at the top of the spindle attached to a rod that ran back > to the steering uprights. Put a crank handle on the end and you can tweak > all you want. > > Wayne Hutchison > > "Pat Dotson" <[email hidden]> wrote in message > news:[email hidden]... > > That concept is used on regular karts. I read about it on > > some web site, and it had me screwed up all last summer! :) > > > > If you are going LTO on an oval, you run stagger on your > > rear tires. The LR wheel doesn't have to unload to go > > around a corner. You do, however, have to turn the wheel > > to the right going down a straight, just like in N4 :) > > > > Yea, my current theory is that while cornering, you want > > the weight 50/50 at both ends of the kart, and use > > stagger, caster, camber, crossweight, etc., to make the > > kart turn. > > > > On an oval, if you transfer all the rear weight to the > > right rear tire, you overwork that tire. I was lifting > > my RR tire for a while when I had my cross weight set > > really low. Trust me, it isn't the fast way around an > > oval! > > > > -- > > Pat Dotson > > > > Paul Laidlaw wrote: > > > "Pat Dotson" <[email hidden]> wrote in message > > > > I've got a new oval track racing kart on the way for this > > > > summer. What I want to do is determine the left side weight > > > > percentage I need, so that while cornering, the weight is > > > > distributed 50/50 between the right side and left side > > > > > > Are you sure that is what you want? I don't know about oval karts but > > > on a normal kart you want as little weight as possible on the inside > rear > > > wheel

Pat Dotson <[email hidden]> wrote in message news:[email hidden]... > I re-checked everything. It all looks correct. The radius > isn't much more than 60'. Speed is close to 40 mph. There > is slight banking to the track, but not much. > > I'll have to think about it some more. Is there some part > of this equation that is being left out? How much banking? It might just be enough... Let's say Q (read theta) is the bank angle, v is speed, M is total mass, r is radius, g is gravity and mu is friction. Resolving forces relative to the track surface, I get M (v^2/r cos Q - g sin Q) needed down the slope, and M (g cos Q + v^2/r sin Q) download on the tyres Check at Q = 0 => sin Q = 0, cos Q = 1 leaving Mv^2/r across and Mg into the ground. Sound good. So adding tyre friction, to corner at the limit we have mu M (g cos Q + v^2/r sin Q) = M (v^2/r cos Q - g sin Q) Since I can now see a trig identity coming on, and I don't like those ;-), cheating and using Excel gives me a bank angle a little under 19 degrees for mu = 0.9 and the data you've already given. Less, obviously, if the tyres are stickier than 0.9. See if that sounds plausible! Jonny

Hi "Pat Dotson" <[email hidden]> wrote in message news:[email hidden]...

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> That concept is used on regular karts. I read about it on > some web site, and it had me screwed up all last summer! :) > > If you are going LTO on an oval, you run stagger on your > rear tires. The LR wheel doesn't have to unload to go > around a corner. You do, however, have to turn the wheel > to the right going down a straight, just like in N4 :)

Ah ha! yes, that would explain all!

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> Yea, my current theory is that while cornering, you want > the weight 50/50 at both ends of the kart, and use > stagger, caster, camber, crossweight, etc., to make the > kart turn. > > On an oval, if you transfer all the rear weight to the > right rear tire, you overwork that tire. I was lifting > my RR tire for a while when I had my cross weight set > really low. Trust me, it isn't the fast way around an > oval!

Have fun! Paul --- Outgoing mail is certified Virus Free. Checked by AVG anti-virus system (http://www.grisoft.com). Version: 6.0.313 / Virus Database: 174 - Release Date: 02/01/02

OK, here are the results of intensive work :) First, I spent an afternoon measuring the race track. The actual radius of the turns is 95 feet, so the lateral G's are a little more than 1 G. There is 2-4 degree banking on the track. Second, what I really wanted to know is, how much left side static weight bias do I need so that during cornering the weight transfer evens out to a 50/50 split between the right side and left side of the kart. Jonny Hodgson came to the rescue with the following equation: x = h (v^2/r cos Q - g sin Q) ----------------------- (v^2/r sin Q + g cos Q) Where x is the offset distance of the static CG from the center of the kart, given, h=VCG v=velocity r=turn radius Q=track banking g=gravity Then the percentage of weight on the inside is just: 100* (x + 0.5t) / t The results are that close to an 80% left side weight bias is needed to balance the weight transfer between the right and left side of the kart. So I'd like to see if there are any comments on the validity of these calculations. Not necessarily whether or not a LTO kart will work with 80% LS weight (though thoughts on that are welcome), but is the formula correct for predicting the weight transfer? Thanks, Pat Dotson Pat Dotson wrote:

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> > A racing kart goes around a 60 ft radius turn at 40 mph. What > is the lateral acceleration of the kart in G's? > > I should be able to solve this in my sleep, but too much time > has passed since graduation :) Don't make me dig out the > text books, please! > > -- > Pat Dotson

Doug Milliken wrote: > I've heard from a friend that the short track cars ("super modifieds"?) > that used to run at the Oswego, NY paved oval had up to 80% left weight. I've been getting more and more pumped up that I'm on to something here. This news is icing on the cake! Thanks Doug. > They were very > fast. Also very easy to roll over if you spun 180 deg...or maybe even if > you had to turn right (up the banking) to miss something in front of you?? That's scary. I wasn't actually going to start out at 80%, more like 70% or so. The key is how low I can get my VCG. The lower it is the less left I have to run. > It will be interesting to hear how this works out for you. I'll probably just end up scuffing my shiny Simpson Super Shark! :) Kart people are very skeptical about high left side weight. Everyone has a stock answer - too much left bias will cause a four wheel drift. With normal setups, cornering at 1 G, 75% of the total weight of the kart is on the right side tires. If you suddenly go to 50% of the total weight on the RS, but still have the same tire setup, of course all the grip is gone. My answer to that is use softer tires and less air pressure until they start gripping. -- PD

Pat, That formula looks familiar, although I haven't used it (writing it down now :0)). If it came from Jonny Hodgson, I'd trust that it's right. How did you find the center of gravity height with yourself on the cart?

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>OK, here are the results of intensive work :) > >First, I spent an afternoon measuring the race track. The actual radius >of the turns is 95 feet, so the lateral G's are a little more than 1 G. >There is 2-4 degree banking on the track. > >Second, what I really wanted to know is, how much left side static >weight bias do I need so that during cornering the weight transfer evens >out to a 50/50 split between the right side and left side of the kart. > >Jonny Hodgson came to the rescue with the following >equation: > >x = h (v^2/r cos Q - g sin Q) > ----------------------- > (v^2/r sin Q + g cos Q) > >Where x is the offset distance of the static CG from the center of the >kart, given, > >h=VCG >v=velocity >r=turn radius >Q=track banking >g=gravity > >Then the percentage of weight on the inside is just: > > 100* (x + 0.5t) / t > >The results are that close to an 80% left side weight bias is needed to >balance the weight transfer between the right and left side of the kart. > >So I'd like to see if there are any comments on the validity of these >calculations. Not necessarily whether or not a LTO kart will work with >80% LS weight (though thoughts on that are welcome), but is the formula >correct for predicting the weight transfer? > >Thanks, >Pat Dotson > > >Pat Dotson wrote: >> >> A racing kart goes around a 60 ft radius turn at 40 mph. What >> is the lateral acceleration of the kart in G's? >> >> I should be able to solve this in my sleep, but too much time >> has passed since graduation :) Don't make me dig out the >> text books, please! >> >> -- >> Pat Dotson

Todd Wasson --- Performance Simulations Drag Racing and Top Speed Prediction Software http://PerformanceSimulations.Com My little car sim screenshots: http://performancesimulations.com/scnshot4.htm

Todd, There are kart setup programs that include a worksheet to calculate VCG. The typical range for VCG is 11" to 14". What you do is first scale the kart to measure the weight at each wheel. Then tip the back end of the kart up and record the new front wheel weights. The programs will calculate VCGb based on the transferred weight, kart wheelbase, and the distance the rear tires are raised. What is intersting is that oval track racing kart setups never use much more than 60% left side bias - usually more like 56%-58%. Yet, to balance the weight transfer between left and right, you need more than 70% left bias. I think I can gain an advantage by running higher left side bias which will work the left tires more. Whether or not the kart will work right or handle well remains to be seen, since they are designed for less left bias. -- Pat Dotson "J. Todd Wasson" wrote: > > That formula looks familiar, although I haven't used it (writing it down now > :0)). If it came from Jonny Hodgson, I'd trust that it's right. How did you > find the center of gravity height with yourself on the cart? > > >Second, what I really wanted to know is, how much left side static > >weight bias do I need so that during cornering the weight transfer evens > >out to a 50/50 split between the right side and left side of the kart. > > > >Jonny Hodgson came to the rescue with the following > >equation: > > > >x = h (v^2/r cos Q - g sin Q) > > ----------------------- > > (v^2/r sin Q + g cos Q) > > > >Where x is the offset distance of the static CG from the center of the > >kart, given, > > > >h=VCG > >v=velocity > >r=turn radius > >Q=track banking > >g=gravity > > > >Then the percentage of weight on the inside is just: > > > > 100* (x + 0.5t) / t > >

Interesting. That VCG is with the driver, correct? Do you sit on the kart when the rear is tipped up, or just estimate the driver's effect afterwards? I've seen this approach before in books, but haven't tried it. Just curious, what's the most popular software for this kind of thing in carting? That's odd that they don't usually run more than 60% left side bias, I wonder why that is. Maybe it's not practical for some reason, although I can't imagine why it wouldn't be.. It seems like you're on the right track there anyway (no pun intended) :-P. Todd Wasson --- Performance Simulations Drag Racing and Top Speed Prediction Software http://PerformanceSimulations.Com My little car sim screenshots: http://performancesimulations.com/scnshot4.htm

J. Todd Wasson <[email hidden]> wrote in message news:[email hidden]... > Pat, > > That formula looks familiar, although I haven't used it (writing it down now > :0)). If it came from Jonny Hodgson, I'd trust that it's right. How did you Don't do that! I was famous at uni for my silly mistakes and factors-of-2... :-) Jonny

Try: http://www.nacoma.cc/kartsmart.htm Yes, that's with the driver. You only have to tip the kart up as little as 6", though the higher it is the more accurate the result should be. -- PD "J. Todd Wasson" wrote: > > Interesting. That VCG is with the driver, correct? Do you sit on the kart > when the rear is tipped up, or just estimate the driver's effect afterwards? > I've seen this approach before in books, but haven't tried it. Just curious, > what's the most popular software for this kind of thing in carting?

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>> That formula looks familiar, although I haven't used it (writing it down >now >> :0)). If it came from Jonny Hodgson, I'd trust that it's right. How did >you > >Don't do that! I was famous at uni for my silly mistakes and >factors-of-2... :-) > >Jonny > > >

Hehe :-) Alllllllll-righty then! Todd Wasson --- Performance Simulations Drag Racing and Top Speed Prediction Software http://PerformanceSimulations.Com My little car sim screenshots: http://performancesimulations.com/scnshot4.htm

For CG height calcs--these are usually very sensitive to any small inaccuracy with the scales. The few times I've done it, I've taken weights at a number of different heights, plotted the results, then fit a good line through the scatter in the data points. I've heard from a friend that the short track cars ("super modifieds"?) that used to run at the Oswego, NY paved oval had up to 80% left weight. There must have been one guy that figured out (by trial and error, and by being clever) what it took to get the car to drive reasonably with that much offset... and then I suppose every one else copied him. The big block V-8 engines were set between the F and R wheels on the left side of the car, drive shaft passed just inside the left rear wheel, rear axle had an offset pumpkin, driver sat next to the driveshaft. These cars were banned some years ago (I'm not clear on the full history). They were very fast. Also very easy to roll over if you spun 180 deg...or maybe even if you had to turn right (up the banking) to miss something in front of you?? It will be interesting to hear how this works out for you. -- Doug Milliken On Thu, 31 Jan 2002, Pat Dotson wrote:

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> Try: > > http://www.nacoma.cc/kartsmart.htm > > Yes, that's with the driver. You only have to tip the kart > up as little as 6", though the higher it is the more accurate > the result should be. > -- > PD > > "J. Todd Wasson" wrote: > > > > Interesting. That VCG is with the driver, correct? Do you sit on the kart > > when the rear is tipped up, or just estimate the driver's effect afterwards? > > I've seen this approach before in books, but haven't tried it. Just curious, > > what's the most popular software for this kind of thing in carting? > >

On Thu, 31 Jan 2002 18:30:10 -0000, "Jonny Hodgson" <[email hidden]> wrote:

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> >J. Todd Wasson <[email hidden]> wrote in message news:[email hidden]... >> Pat, >> >> That formula looks familiar, although I haven't used it (writing it down now >> :0)). If it came from Jonny Hodgson, I'd trust that it's right. How did you > >Don't do that! I was famous at uni for my silly mistakes and >factors-of-2... :-)

Hehe, whatever happened to just off-by-1? ;-) Ruud van Gaal Free car sim: http://www.racer.nl/ Pencil art : http://www.marketgraph.nl/gallery/

Ruud van Gaal <[email hidden]> wrote in message news:[email hidden]...

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> >> That formula looks familiar, although I haven't used it (writing it down now > >> :0)). If it came from Jonny Hodgson, I'd trust that it's right. How did you > > > >Don't do that! I was famous at uni for my silly mistakes and > >factors-of-2... :-) > > Hehe, whatever happened to just off-by-1? ;-)

<g> I was fine with the off-by-ones; my answers almost always came to a factor of 2, whenever they were wrong! I think it's actually something to do with my inability to operate a calculator... Jonny