elliptical timing gears.

[DesertRunner]

I would like to try to make a couple of elliptical timing gears that can be driven with a timeg belt.  The thought would be to have one and each end of the belt, in other words just the two gears on the belt.  If I do succeed in getting it to work will the speed of the driven be variable as it is with gears.  They will only be 1st order gears.
My problem is that I am developing a engine and I need to find a way to alter the rate of movement of a valve driven on a crank.  I really don't want to use a cam if I can aviod it as it will require a spring for the return.  My feeling is that if I use gears they may not stand the speed of around 6,000 rpm.

Open to suggestions please.
Tony

[ArtF]

Im not sure I understand..you mean elliptical timing pulleys ort two elliptical gears meshed together and driven by pulleys?

Art

[JustinO]

Sounds like you want to reinvent the Corliss steam engine.

[JustinO]

The problem I see with non circular timing pulleys is that the circumference of the system would not be constant except for a few degenerate instances....I think.

Linkages are surprisingly adaptable...

[DesertRunner]

Good morning or evening which ever it maybe,
Art I am talking about elliptical timing pullies.  Is there a formula to calculate the speed of the driven shaft?
Thanks.
Tony

Edit Just sorted out ratio so I am all good, now only need to figure out how to cut with timing belt teeth.
Tony

[ArtF]

Tony:

  You cant really. Tooth profiles on ellipticals are different than round, they are actually diferrent on each side of the tooth depending on the instant of radius on the gear at each point. I imagine it
can be cheated to get close enough to hold a belt.. youd have to cad that though, GM wont make one.
  That having been said, yes the ratio would act just as if they were gears..

Art

[DesertRunner]

Thanks Art,
Really appreciate it, keep well.
Tony