I have been playing around with some link calculators and it always asks for a center of gravity height. And I found ways of figuring it out with a car but it involves weighing your car, then tipping it towards the front to get a movement of weight and then you can calculate where your center of gravity weight is.

Has anyone ever done this with a first gen?

i figure in all of the rx7 boredom someone would have actually tried to find a decent answer.

 

Not what you're asking, but neat and relevant to the thread


cross sectional weight and lift chart:




Isaac

 

Cool! Now I want to make a model of that line, I'm sure there's some way to integrate (pun definitely intended) this information into my CAD model... (which is still very early before you ask).

In response to the OP, I haven't done that, but I really want to/have access to both a lift and a set of longacres. I'll have to do that before I graduate, and after I get my car running.

The lift data is also really interesting. I wish I knew more about aero, so I could actually do anything with that.

 

The 1st gen really is a nice looking car.

 

i found this website that seems to simplify it down to some basic figures.

http://www.longacreracing.com/articles/art.asp?ARTID=22

it doesn't give you forward and side to side location of the CoG, but that could be figured out at least with just the 4 corner weights.

but if i had, or had access to some weighing pads i would just through mine on there and measure it.


edit: here's a site that has all three, just need the plug the figures in. i need me some weighing pads.

http://www.agileruggedterrainvehicle...CG_HTCGV2.html

 

Did anyone notice the Center of Gravity symbol on that previous drawing? The two little black pie pieces in the middle of the car, you even get its height, take some measurements off the drawing, and scale it to the real car, question answered

 

well all be damn, i didn't even see that.

looks to be around the front u joint area. that's easy enough to measure.

 

can anyone read what that picture says?

 

Oooh, Oooh! I see a 12A in between all the japanese spelling. ...That's all the help I can offer haha

 

i saw it but it just looks like the center of the drawing?

 

Nope that IS the symbol for center of gravity.

 

The front/rear weight of these cars is very close to 50/50, so the COG should be very close to the center of the drawing horizontally. The vertical point is the hard one to figure out and is important for roll center.

 

ok, that was too easy then

 

actually it's not that hard to figure out, you just need access to scales and the ability to lift one end up off the ground a good couple feet.

i gave links to calculators if there was numbers to put in them. i just don't know anyone that has weight pads.

 

if you move the seat all the way to the rear and the roll center should be at the top of the seat where your thigh rests.obviously in the center right behind the shift ****. should be the same height as the driveshaft tunnel

 

Roll center is different than center of gravity, but I'm sure you meant CG.

 

No, he meant roll center. They are different things, but what he was referring to was that the relationship between roll center and CG height is important.

 

Alright, I just did the maths, so in case you don't want to do the math yourself, based on this drawing, the CG height of an SA is 16.06in (407.9mm). When I get my SE driving around, I'll throw it on some scales and see how different the two numbers are.

Also, the F:R weight distribution was 50:50 near as it makes no difference.

 

And don't forget:
Gas tank 1/2 full NOT FULL. You dont run the entire race (or trip) on a FULL gas tank.
Also, when you weigh the 4 corners, have someone (or you) that sit in the dirver's seat
with the seat at the position (forward/back and up/down) the normal driver of the car
uses.

I spun out at 85mph once in my '79. It took chunks off the edges of the tires! The change on the passenger seat never moved! So, I think that the back of the shift lever housing is pretty damn close to the lateral CG.

 

Fixed.

~T.J.

 

Haha, turns out I am way more helpful than i think...


Isaac