Where is the COG located on the various variants of this car? Has anyone done the measurements and the calculations?
cheers
Gary
cheers
Gary
COG
- Thread starter gyrogary
- Start date
There is probably not going to be a lot of variance between models. CoG of cars with big blocks and heavy transaxles will obviously be a bit further rearwards unless some heavy items are placed near the front to compensate eg battery.
Since no one has replied to this since you posted. My car has 351W Dart iron block, alloy heads, 930 (which is a reasonably light trans @ 53 kg dry). Complete with oil and water and large alloy radiator, light weight body, the CoG is 950 in front of the rear axle line giving a 59/41 weight distribution without fuel or driver.
Hope that gives you something to go on. Fuel and driver are going to move the CoG forwards as will most other bodies and chassis which are considerably heavier than mine.
Still planning to be up your way this Sunday, will call in for a natter on the way through. See you then :thumbsup:
Since no one has replied to this since you posted. My car has 351W Dart iron block, alloy heads, 930 (which is a reasonably light trans @ 53 kg dry). Complete with oil and water and large alloy radiator, light weight body, the CoG is 950 in front of the rear axle line giving a 59/41 weight distribution without fuel or driver.
Hope that gives you something to go on. Fuel and driver are going to move the CoG forwards as will most other bodies and chassis which are considerably heavier than mine.
Still planning to be up your way this Sunday, will call in for a natter on the way through. See you then :thumbsup:
Thank you for that. What height is it?
Look forward to meeting you on Sunday.
cheers
Look forward to meeting you on Sunday.
cheers
Ah well! That is the sixtyfour thousand dollar question!
I have no idea, not so easy to measure. I would suggest maybe 150mm above the crank centreline. Percentagewise CoG height is going to vary greatly from car to car, depending on whether the input shaft is above or below the output shafts, chosen ride height plus all the other factors that affected the longitudinal position.
In the past when I have replied with guesses to a thread that has gained no traction, the minute I provide a guesstimate, someone always comes along with some hard data to blow me out of the water! LOL Keep your fingers crossed for some good info!
I have no idea, not so easy to measure. I would suggest maybe 150mm above the crank centreline. Percentagewise CoG height is going to vary greatly from car to car, depending on whether the input shaft is above or below the output shafts, chosen ride height plus all the other factors that affected the longitudinal position.
In the past when I have replied with guesses to a thread that has gained no traction, the minute I provide a guesstimate, someone always comes along with some hard data to blow me out of the water! LOL Keep your fingers crossed for some good info!
Hi Mick
That's how you do it.
Has any one done this to their GT's
That's how you do it.
Has any one done this to their GT's
hi Russ and Gary,
This Diagram will help you find the lateral C.G.
When I started my GT40 scratch build 18 yrs ago, there was no internet. so my reaserch was done with books. these formulas, and diagrams, are from .
Fred Phuns book "How To Make Your Car Handle." by HP books
Another good book to read is,
Competition Car, SUSPENSION. Design.Construction. Tuning. by Allan Staniforth, by Haynes books
They may be old books. but there is lots of really good information in them..
I have also included the text that goes with both of the diagrams.If it is not clear, send me your email addy, and i will send it to you
Mick
This Diagram will help you find the lateral C.G.
When I started my GT40 scratch build 18 yrs ago, there was no internet. so my reaserch was done with books. these formulas, and diagrams, are from .
Fred Phuns book "How To Make Your Car Handle." by HP books
Another good book to read is,
Competition Car, SUSPENSION. Design.Construction. Tuning. by Allan Staniforth, by Haynes books
They may be old books. but there is lots of really good information in them..
I have also included the text that goes with both of the diagrams.If it is not clear, send me your email addy, and i will send it to you
Mick
Attachments
<o:smarttagtype namespaceuri="urn:schemas-microsoft-com<img src=" http:="" www.gt40s.com="" forum="" images="" smilies="" redface.gif="" border="0" alt="" title="Embarrassment" smilieid="2" class="inlineimg"></o:smarttagtype> Hi Mick
Thank you for all the info. I read those books and others and copied heaps of info from them back in the late 80's when I did a Lotus 7 scratch build. No internet then just the local library and ordering in books from the national library.
I am after the COG location of some of the current builds so I can incorporate some anti squat and anti dive in my suspension design. My research says that the originals had 30% anti squat and anti dive.
Hopefully your info will inspire someone to measure there car.
<st1:city><st1
lace>Gary</st1lace></st1:city>
Thank you for all the info. I read those books and others and copied heaps of info from them back in the late 80's when I did a Lotus 7 scratch build. No internet then just the local library and ordering in books from the national library.
I am after the COG location of some of the current builds so I can incorporate some anti squat and anti dive in my suspension design. My research says that the originals had 30% anti squat and anti dive.
Hopefully your info will inspire someone to measure there car.
<st1:city><st1
lace>Gary</st1lace></st1:city>hi Gary,
I will Try to do the calculations with my car this week
Then it would be possible to calculate Weight transfer, under braking.
I have used a exel spread sheet to calculate Front and rear brake mastercylinders. disc diameter. caliper size and amount of pistons, etc.to get the correct front to back brake bias (posted by Clayton, on this site. the post was about 4 months ago, and was called..."How do I set up my brake bias bar ?)
The exel sheet does have a changable value for the height C.G. but as most people dont know the height of the C.G. of their car. they wont be able to put the correct values in for their car. It is suprising, how Just changing the CG height by 2 inches. changes the bias
here is Claytons exel sheet
View attachment Claytons brakes.xls
mick
I will Try to do the calculations with my car this week
Then it would be possible to calculate Weight transfer, under braking.
I have used a exel spread sheet to calculate Front and rear brake mastercylinders. disc diameter. caliper size and amount of pistons, etc.to get the correct front to back brake bias (posted by Clayton, on this site. the post was about 4 months ago, and was called..."How do I set up my brake bias bar ?)
The exel sheet does have a changable value for the height C.G. but as most people dont know the height of the C.G. of their car. they wont be able to put the correct values in for their car. It is suprising, how Just changing the CG height by 2 inches. changes the bias
here is Claytons exel sheet
View attachment Claytons brakes.xls
mick
Gary,
Its very intresting to see what you have built, and that you are going to use anti dive, and anti squat, on your car.I didnt use any anti dive , or anti squat on my car , as I wanted to keep it simple......
my car is useing a rover 3.5 V8 alloy engine. The car is not finished but it is a rolling chassis with the spider, front and rear clips fitted, but no petrol tanks. The chassis weighed about 230 lbs. but i have modified it a lot from the original chassis, so Im not sure what the chassis weight is now...(less I hope)
.I am also going to lower the engine by 2 inches, so it will be intresting to see how the C.G. changes with the differnt engine positions
mick
Its very intresting to see what you have built, and that you are going to use anti dive, and anti squat, on your car.I didnt use any anti dive , or anti squat on my car , as I wanted to keep it simple......
my car is useing a rover 3.5 V8 alloy engine. The car is not finished but it is a rolling chassis with the spider, front and rear clips fitted, but no petrol tanks. The chassis weighed about 230 lbs. but i have modified it a lot from the original chassis, so Im not sure what the chassis weight is now...(less I hope)
.I am also going to lower the engine by 2 inches, so it will be intresting to see how the C.G. changes with the differnt engine positions
mick
Hi Gary,and Russ
well I had a go at measureing the COG Height. It wasnt easy.I bolted the load bars to pallets, and bolted a frame to the load bars to support the wheels, , then I raised the pallet supporting the rear wheels with a forklift unfortunatly the frame work hit on the chassis at the back, so I was only able to raise the back of the car by 16 inches. but if I get up early tomorrow, i will modify the frame so i can lift the car at least 24 inches
With the car level
Rear wheel height 941 lbs
total weight 1617 lbs
wheelbase 95 in
giving F the value of 55.31
With the rear of the car raised 16 in
Rear wheel weight 935 lbs
Total weight 1621.4 lbs
L = 93 in
Giving G the value of 53.6 in
I havnt done the calculations to find the height as I cant remember how to do sines, etc, but I did measure it, and it seems to be about 16.5 in above ground level. with a 4 in ride height
The centre of the crankshaft is 14 in above ground, but it will be intresting to see how the COG height changes when I lower the engine by 2 ins
The car is not finished, so It is only an approximate COG height. but I hope this helps you Gary. I will see if I can get someone with a finished GT40 to let me measure their car, and get a more accurate COG height
well I had a go at measureing the COG Height. It wasnt easy.I bolted the load bars to pallets, and bolted a frame to the load bars to support the wheels, , then I raised the pallet supporting the rear wheels with a forklift unfortunatly the frame work hit on the chassis at the back, so I was only able to raise the back of the car by 16 inches. but if I get up early tomorrow, i will modify the frame so i can lift the car at least 24 inches
With the car level
Rear wheel height 941 lbs
total weight 1617 lbs
wheelbase 95 in
giving F the value of 55.31
With the rear of the car raised 16 in
Rear wheel weight 935 lbs
Total weight 1621.4 lbs
L = 93 in
Giving G the value of 53.6 in
I havnt done the calculations to find the height as I cant remember how to do sines, etc, but I did measure it, and it seems to be about 16.5 in above ground level. with a 4 in ride height
The centre of the crankshaft is 14 in above ground, but it will be intresting to see how the COG height changes when I lower the engine by 2 ins
The car is not finished, so It is only an approximate COG height. but I hope this helps you Gary. I will see if I can get someone with a finished GT40 to let me measure their car, and get a more accurate COG height
Attachments
Hi Mick
Awesome. Above and beyond the call of duty.
Interesting to see that your COG is only about 50mm ahead of where Russ has his.
With a driver, passenger and some fuel on board the cog will be heading towards the 50/50 split. The height surprised me as to how low it is, probably quite a bit lower when loaded.
Gary
Awesome. Above and beyond the call of duty.
Interesting to see that your COG is only about 50mm ahead of where Russ has his.
With a driver, passenger and some fuel on board the cog will be heading towards the 50/50 split. The height surprised me as to how low it is, probably quite a bit lower when loaded.
Gary
If you know the height of your front and rear suspension roll centres, that gives you the car roll axis. The distance of the CofG from this roll axis determines some of the roll behaviour during cornering. It is a bit like metacentric height in ships, relating their CofG (as I recall) to their centre of displacement.
The inclination of the roll axis (plus the relative spring stiffness front to rear) then affects the weight transfer front and rear during cornering. All interesting stuff.
The inclination of the roll axis (plus the relative spring stiffness front to rear) then affects the weight transfer front and rear during cornering. All interesting stuff.
Not exactly. While the roll axis has an effect on suspension jacking and the amount the chassis rolls, there's no change in the real weight transfer from acceleration and cornering. The moments from those forces must be translated into actual weight transfer. No way to get around the free-body analysis...
Yes, but the roll axis does affect the diagonal weight transfer which has a significant effect on the balance of the car.
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