Wankel Rotary Engine Geometry
Wankel Rotary Engine Geometry
(OP)
Hello all,
I am doing some research on the Wankel rotary engine andd have so far determined that the shape of the housing is peritrochoidal and that the shape of the rotor is the inner envelope of said peritochoid.
I have derived formula for the peritrochoidal housing shape based on rotor radius and eccentricity, but I cannot find any info on how to create the correct rotor flank shape.
Any one able to shed any light on this please?
Many thanks,
Jon Reynolds
I am doing some research on the Wankel rotary engine andd have so far determined that the shape of the housing is peritrochoidal and that the shape of the rotor is the inner envelope of said peritochoid.
I have derived formula for the peritrochoidal housing shape based on rotor radius and eccentricity, but I cannot find any info on how to create the correct rotor flank shape.
Any one able to shed any light on this please?
Many thanks,
Jon Reynolds
Regards,
Jon Reynolds





RE: Wankel Rotary Engine Geometry
There are lots of SAE papers from the Curtiss Wright days. Your research won't be complete without them.
RE: Wankel Rotary Engine Geometry
Ah I have that book by Yamamoto...the equations seem overly complicated. I derived my own formula for the housing in a much simpler way. Well simpler for me to understand... and I would rather be able to derive them myself than just copy them from a book.
I will continue to look around.
Many thanks,
Jon Reynolds
Regards,
Jon Reynolds
RE: Wankel Rotary Engine Geometry
RE: Wankel Rotary Engine Geometry
Are you referring to this:
https
If so, I have already come across that and not found it very helpful.
There seems a bit of confusion (for me at least) as to the shape, whether it is epitrochoidal or peritrochoidal. I have been saying it is peritrochoidal as this is what is in the book by Yamamoto. But I think perhaps both solutions lead to the same shape.
As for the rotor shape, I think I can work it out. Basically by rotating the shapes around and plotting the points on the housing surface that would be closest to the rotor... hard to explain but I think I see it in my head.
Regards,
Jon Reynolds
RE: Wankel Rotary Engine Geometry
RE: Wankel Rotary Engine Geometry
RE: Wankel Rotary Engine Geometry
Mind, even if I wanted to use Yamamoto's equations, I am not sure how to put 'v' into the excel formulas...
v = 1/6 pi ~ 1/2 pi, 5/6 pi ~ 7/6 pi, 3/2 pi ~ 11/6 pi
Regards,
Jon Reynolds
RE: Wankel Rotary Engine Geometry
There might be a physical significance to v but I have not figured it out.
RE: Wankel Rotary Engine Geometry
Just can't get them calcs into excel properly... could well be just syntax errors as its a long line to get in one cell, with umpteen parentheses etc.
so I am putting 30 - 90 as v, but what about in the equation where it says +/- e(... should I use plus or minus??
Thanks again.
Jon
Regards,
Jon Reynolds
RE: Wankel Rotary Engine Geometry
The guy at Wankel told me to use all plus or all minus. It seems to work that way.
RE: Wankel Rotary Engine Geometry
Closest I have got is a rounded triangle (right shape) but too big and rounded... this is basically a hypotrochoid. But something's not quite right.
Regards,
Jon Reynolds
RE: Wankel Rotary Engine Geometry
Cheers
Greg Locock
SIG:Please see FAQ731-376: Eng-Tips.com Forum Policies for tips on how to make the best use of Eng-Tips.
RE: Wankel Rotary Engine Geometry
Did you do some tidying up or am I imagining replying to a post last night that has now vanished? You're making me feel like I'm going mad...
But anyway...that is the best looking description/simulation showing how it is constructed. I knew how it was made from the motion of the housing, but I just can't get my head around the maths, without looking at other examples... hopefully this one will put it to bed.
Thanks.
Regards,
Jon Reynolds
RE: Wankel Rotary Engine Geometry
Cheers
Greg Locock
SIG:Please see FAQ731-376: Eng-Tips.com Forum Policies for tips on how to make the best use of Eng-Tips.