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Post by Deleted on Jul 3, 2016 20:17:12 GMT -5
Interesting. It is held closed by a cam and then opened by a cam...no spring that I could see. The only problem I see there is that...with just a tiny bit of wear on the valve "closed" cam surface, then that valve may not be totally sealed. I never saw anything like that before so, thanks for showing it.
Bill
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Post by jeff84 on Jul 3, 2016 20:18:37 GMT -5
that is brilliant
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Post by jeff84 on Jul 3, 2016 20:21:42 GMT -5
Interesting. It is held closed by a cam and then opened by a cam...no spring that I could see. The only problem I see there is that...with just a tiny bit of wear on the valve "closed" cam surface, then that valve may not be totally sealed. I never saw anything like that before so, thanks for showing it. Bill surely in a practical application there would be a valve shim so adjustments could be made |
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Post by acvw74 on Jul 3, 2016 20:58:23 GMT -5
I think it is probably great for racing...you could rev the engine to the moon...but for a "street" engine, I think wear would force you to make adjustments all the time.
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Post by aeroxbud on Jul 4, 2016 7:55:01 GMT -5
That's right Ducati are the only manufacturer in motoGP not using pneumatic valves as the Desmondromic valve's system works as well.
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Post by FrankenMech on Jul 4, 2016 19:02:43 GMT -5
The Ducati valve would need some sort of hydraulic lifter type mechanism or a small spring to hold the valve shut. There may be something hidden behind the cam. Shims or 'adjustments' would not work due to temperature variations.
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Post by 190mech on Jul 4, 2016 19:21:52 GMT -5
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Post by jeff84 on Jul 4, 2016 22:51:46 GMT -5
idk. what is the limiting factor in two strokes? us it just heat?
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Post by 2stroked on Jul 5, 2016 20:41:08 GMT -5
Back in TH early 2000's around 00-01, Ford was experimenting with spherical rotating dual purpose valves for a concept program. I only know about it because I was in an ASE prep class, and an engineer from Ford came and talked about it and even brought a cut away V-8 head with he valve spheres.
The main limits of a 2t, I believe, are crank bearing and con rod abue from high revs. I could be, an probably am wrong in that though.
Back to the spherical valve concepts, thy were just orbs of some type of metal that the engineer wouldn't disclose, that were rotated by hydraulic force lubrication. There were two spheres on each cylinder on the I-4 an only one on the V-8. Each sphere had an odd shaped cut away that acted as the open section of the valve movement. The engineer talked about the limiting factor of that valve type being a that time sealing surface warping with extreme heat. He also said that they had tested and retested and that they found the redline revvs to be near 1200 an that the crank would fail long before the valves would float o cause issue
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