Using values to derive the general shape of a rotor

[josh18_2k]

just measure a rotor and figure it out?

im guessing 105mm is the arc radius of the face, and then the midpoint is offset 15mm (to the inside obviously) to clear the peanut shape. but i dunno, ive never even seen a rotor IRL lol

[vex]

Alright looks like I need to give RCC a refresher course in geometry. More specifically in conic sections.

Originally Posted by Mobius

If someone on this forum actually understands what vex is asking, I will give that person an e-cookie Because all i got was:

Eccentricity (e) is the term used to describe a conic section. For instance in the case of a circle e=0. Eccentricity in geometric and orbital understanding is unit-less, thereby the term an eccentricity of 15mm is outside my understanding of the term usage.

Furthermore e is the ratio between c and a, where a is the semi-major axis value or the distance between the center point and the longest edge, and c is a geometric constant which is resulted from the sqrt(a^2-b^2) where b is the semi-minor axis or the distance from the center to the shortest edge.

Originally Posted by josh18_2k

just measure a rotor and figure it out?

I would, but I don't have one readily available. When I had my engine apart I couldn't take the time to get all the dimensions I need so I am stuck doing things this way.

im guessing 105mm is the arc radius of the face, and then the midpoint is offset 15mm (to the inside obviously) to clear the peanut shape. but i dunno, ive never even seen a rotor IRL lol

That was my thought as well, but using those values produces a rather 'bloated' rotor from what I remember. As this is a link to where I'm pulling the values from:

Rotary History