Formula1 pneumatic valve engine

[alfasud]

Originally posted by RWC
f1 engines were NOT limited to 13000rpm before the pnumatic systems were developed.Honda motorcycle 4 stroke racing engines of the sixties had redlines of 15000-23000rpm(!!!),depending on the model.

If you want to go for higher reves then you just use stronger springs...

Someone already mentioned bike engines earlier in this thread, and as previously discussed, all those 20,000rpm+ bike engines had very small cylinders (62cc for 4 cylinder 250, 83cc for 6 cylinder 500) and hence very small valves with less valve lift than a 3000cc V10.

Please name a 1960's bike (or any other) 4 stroke engine with single cylinder size of 300cc (or more) that ran at greater than 13,000rpm.

I'm sure stonger springs would help for a while at least, but I'm wondering how long those springs (and whole valve train - cam lobe wear etc) would last (if the spring is doing more work, there are heating losses and I'd expect that eventually the spring will lose it's temper)?

As for 2 strokes, I'm told their efficiency isn't too good. This implies a 2 stroke F1 car will be carrying a lot more fuel, or stopping more often (and I don't think the rules permit 2 strokes anyway).

[madmat666]

ducati
1000cc v twin
may be wrong but id be surprised if they didnt rev above that
i think the road engined peak at 11500 but the tuned racing engine???

[alfasud]

Don't know about the revs for a ducati 1000cc v twin racing engine.... but I guess my question (in responce to the preious post) was about valves closed with springs. Is the Ducati you refer to using valve springs or is it a desmo?

[madmat666]

i see, yeah they are desmo
dont fully understand the mechanics of the thing coz there are still springs present but i overlooked that one

[Guisbro Rod H]

Desmodromic valves are adequately explained with diagrams on the following web page:

http://www.usq.edu.au/users/grantd/mcycle/desmo.htm

Any help?

[madmat666]

nice diagram, after a bit of a search i found lodsa techy stuff on the ducati site, some of it pretty interesting

[gttouring]

Well aside from the pneumatic issue in F1 valve trains, (i still don't quite see where the penumatice return system is in relation to the spring and valve)
F1 and even Corvettes now i am sure use either Sodium filled valves or hollow valves thus rducing the mass and inertia of said moving components, so with hollow valve technology oavilable, and older motor design from the 80's or earlier, may have used thes to gain Rev's in regards to the spring limitation.
when simple reduce the weight the spring has to accelerate.
so the previous 13K limit may be avoided or pushed higher, and the use of double springs might help the cause as well.

[gttouring]

i might add after reading about the desmodromic ssystem- it is a wonder why 1) i never thought of it and
2) it really is simple and there are no real spring issues, so why doesn't everyone use it - it can't be more expensive than spring valve trains...as it is said on www.ducati.com (tech section)
To obtain good results with a spring system, it is necessary to find a compromise between heavier spring loading requirements (possibility to turn at high RPM, while preventing valve bounce) and lighter spring loading requirements (loss control, loss being the amount of work necessary to open the valves against the spring loading: it should be remembered that the camshaft is driven by the engine; and smaller sizing of the parts involved, proportional to the spring loading).

These problems are all solved by a desmodromic system: smoothness (and consequently, decreased losses) at low RPM and reliability at high RPM (without valve bounce) are obtained.

Why trouble yourself with a pneumatic system if this is doing the work for less trouble than a tank of air and leakage trouble.
it's even an old piece of tech since 1956 according to the Ducati website.

[avsfan733]

the problem that i see is the lack of dwell time in the zero lift valve position which would make it a problem to get proper compression and expansion

[gttouring]

well with the lack of dwell time at zero lift, would necessesitate (sp) faster engine, higher revs- so the time at TDC and BDC (dead centers -top and bottom) would be minimized as well. So compression can be reached and be rather high i imagine..

[avsfan733]

no the dwell time in that situation wouldn't change. At least not in relation to the piston speeds. With the desdomonic, it seems like it forces the valve to always be moing, so you can't have the flat part of the profile. the cams need to be able to spen the entire compression and expansion stroke (in the basic sense ignoring valve tuning isues) sealed shut. If they don't, you leak compression. the desdomonic looks a lot like the crankshaft on the engine, and that never really spends any time at TDC or BDC, its always moving