Height of COG

[ERA2076]

What is a good number to use for the height of COG on an FIA?

x-cliff

[strictlypersonl]

17" is about right. I've sent you a spreadsheet with my estimates.

[Steve Cassani]

Decades ago a discussion of ride height, camber and so on saw one of the participants tell the group a suspension can be configured to lower the COG. He claimed Lotus (Chapman was alive at the time) designs for a COG that is effectively a foot or more below the road. I still have not been able to determine whether this claim has merit. What do you think?

[Jerry Clayton]

COG is 12,500 miles below ground surface------------

A old time rule of thumb is cog equals camshaft centerline (I think its a left thumb)

[ERA Chas]

Originally Posted by Jerry Clayton

COG is 12,500 miles below ground surface------------

A old time rule of thumb is cog equals camshaft centerline (I think its a left thumb)

Does that apply to DOHCs?? If so, which cam??

[strictlypersonl]

Originally Posted by Steve Cassani

Decades ago a discussion of ride height, camber and so on saw one of the participants tell the group a suspension can be configured to lower the COG.

You can create a geometry that lowers the car's COG a very small amount on roll but it's a physical effect that's hardly significant.

He claimed Lotus (Chapman was alive at the time) designs for a COG that is effectively a foot or more below the road. I still have not been able to determine whether this claim has merit. What do you think?

I've seen some fancy (all mechanical) designs that, with cornering forces, make the car roll in the opposite direction than you would expect. I think there was one in the Costin-Phipps book of the '60s, and I've seen another one more recently. But - it's all playing with geometry and linkage. You could do it more simply by having a roll center that's above the COG, but that creates a very unstable situation that actually raises the COG on cornering. (Think VW swing axles front and rear.) At this point, technology makes roll-less cornering pretty easy to do with active suspension, but apparently most people aren't very comfortable with how the car "feels". Some years ago I worked out an approach that required only a small amount of power to achieve near-zero roll, but it never got past the paper stage.

[Bobcat]

What Bob said about people being uncomfortable with no roll is very true . Years ago , I did some work with a company ( no name ... NDA ) that was designing an active suspension using hydraulics and microprocessors . They could actually make the car "tilt" to the inside of a turn just by doing some reprogramming .
The test drivers were very uncomfortable with it as were some test subjects .... I thought it was cool , but then I`m strange .

[Jerry Clayton]

And nobody noticed that I used the Earth's circumferance instead of the radius of 3,959 miles?????????///

sorta like Zimmerman's lawyer's knock knock joke??????

[ERA2076]

Originally Posted by Jerry Clayton

COG is 12,500 miles below ground surface------------

A old time rule of thumb is cog equals camshaft centerline (I think its a left thumb)

Yea - I've always used the cam. My car is without an engine. I saw recently height of crank + 5".

Bob sent me some very useful data.

Thanks Bob

chr

[lovehamr]

You're to smart for me Jerry!

[DanEC]

Originally Posted by Jerry Clayton

And nobody noticed that I used the Earth's circumferance instead of the radius of 3,959 miles?????????///

sorta like Zimmerman's lawyer's knock knock joke??????

I did but I didn't want to say anything.

[juneracer]

Originally Posted by Steve Cassani

Decades ago a discussion of ride height, camber and so on saw one of the participants tell the group a suspension can be configured to lower the COG. He claimed Lotus (Chapman was alive at the time) designs for a COG that is effectively a foot or more below the road. I still have not been able to determine whether this claim has merit. What do you think?

probably referring to roll centers. CoG is a tough one to lower significantly.