Pneumatic valve train in detail

[ringo]

riff_raff,
looking at the F1 diagrams we have here, i notice that they have rigid cylinders for the air chamber and not diaphragms that are typical on automotive suspension air springs.
What is your take on this?
I believe leakage with the rigid cylinder may be a bigger issue than we thought.

Here's a nice article if anyone is interested in air springs.

http://www.nts-bg.ttm.bg/journal/Archiv ... .mtm10.pdf

Apparently this article is about having an additional volume beside the main spring chamber. The additional chamber permits tune-ability of the spring rate.
what is shown is that the stiffness of the spring is dependent on many things, most notably, frequency dependence. I am not sure how this stiffness and frequncy profile will look at 150Hz (valtrain at 9000rpm, engine at 18000) or for lower engine speeds seeing as though the experiment was with much lower frequencies.
Other dependents are: gas pressure, piston area, gas constant .

The spring stiffness is inversely proportional to the chamber volume. I suppose in a F1 race car valve stem chamber, you can modulate the regulator to either reduce chamber pressure as the volume decreases, depending if you want a constant spring rate. I can imagine the chamber will have rapid changes in speed and volume thus rapid pressure changes.

All in all the physical system seems like it should be very simplified for a valve train. It doesn't have the needs that vehicle suspension would.

From this article.

waepubl.luth.se/1402-1617/2002/059/LTU-EX-02059-SE.pdf

There is an equation for a constant effective area, which sounds like an F1 valve stem chamber.

K = (atm. press + gauge press) * Area of piston ^2 / Chamber volume.

[jamesr20]

This is a basic question but what is the advantage of pneumatic valves over spring valves is it simply that at higher rpm's they are more affectiv or is more complex than that, sorry if this is a stupid question but you good folks will be able to tell me. Thanks

Jesse

[Hobbs04]

Sorry Jamesr20 don't know the exact answer to question, but my limited knowledge leads me to believe it has to do with stresses put on springs at high rpm would add unnecessary weight. I'm sure searching this site will give you some more info.

This isn't directly related to your question but worth a watch.

http://youtu.be/Bch5B23_pu0

Good video mostly good advertising for Koenigsegg, but interesting valvetrain technology. They have developed an engine without cam shafts. I'm not sure if this would ever trickle into F1. With all the engine mapping changes recently would it even matter but interesting none the less.

[jamesr20]

Sorry Jamesr20 don't know the exact answer to question, but my limited knowledge leads me to believe it has to do with stresses put on springs at high rpm would add unnecessary weight. I'm sure searching this site will give you some more info.

This isn't directly related to your question but worth a watch.

http://youtu.be/Bch5B23_pu0

Good video mostly good advertising for Koenigsegg, but interesting valvetrain technology. They have developed an engine without cam shafts. I'm not sure if this would ever trickle into F1. With all the engine mapping changes recently would it even matter but interesting none the less.

Thank you hobbs04 that gave me a better idea of how it all works, it seems to beneficial in road car usage, correct me if I'm wrong but would a spring return rate be much slower at 18,000 rpm in comprarison to compressed air return, hence to reason for using pneumatic valves?

[xpensive]

This is a basic question but what is the advantage of pneumatic valves over spring valves is it simply that at higher rpm's they are more affectiv or is more complex than that, sorry if this is a stupid question but you good folks will be able to tell me. Thanks

Jesse

One of the original advantages was that in a pneumatic system like this, the gas-chambers are not really springs as
they are interconnected to have an almost constant total volume, why the gas-pressure is also basically constant.
This way there is no hysteresis and very little heat generation compared to a conventional spring-system.

All in all, no heat means higher valve-load is allowed and thus higher revs.

[jamesr20]

Another question all be it slightly off topic how long have they been using pneumatic valve trains in f1, having only recently learned of usage I'm intrigued to know how long it's been around for?

[Brian.G]

Another question all be it slightly off topic how long have they been using pneumatic valve trains in f1, having only recently learned of usage I'm intrigued to know how long it's been around for?

1993 I think in the Fw15 Williams,


Brian,

[langwadt]

Another question all be it slightly off topic how long have they been using pneumatic valve trains in f1, having only recently learned of usage I'm intrigued to know how long it's been around for?

1993 I think in the Fw15 Williams,


Brian,

it was probably a renault, but I believe it was already in use back in the turbo era

[strad]

No float..no valve bounce,,less prone to failure with no metal springs to fatigue..I'm not sure about less weight but when Renault tried doing away with cams with electro-magnetic system the added weight high up on the engine and thus raising the center of gravity was part of the stated reason for abandoning the idea...I think it was too slow for today's high revving engines.

[jamesr20]

Been around for a good while then, thank you for the info folks

[riff_raff]

This is a basic question but what is the advantage of pneumatic valves over spring valves is it simply that at higher rpm's they are more affectiv or is more complex than that, sorry if this is a stupid question but you good folks will be able to tell me. Thanks
Jesse

Pneumatic systems have less mass inertia, no fatigue or stress limits, reduced volume requirements, less sensitivity to structural vibrations, and reduced friction losses at high operating frequencies.

[wuzak]

Another question all be it slightly off topic how long have they been using pneumatic valve trains in f1, having only recently learned of usage I'm intrigued to know how long it's been around for?

1993 I think in the Fw15 Williams,


Brian,

it was probably a renault, but I believe it was already in use back in the turbo era

Renault did pioneer the system - around 1986.

[wuzak]

riff_raff,
looking at the F1 diagrams we have here, i notice that they have rigid cylinders for the air chamber and not diaphragms that are typical on automotive suspension air springs.

I would think it is the stroke that would cause problems for a simple diaphragm.

[xpensive]

riff_raff,
looking at the F1 diagrams we have here, i notice that they have rigid cylinders for the air chamber and not diaphragms that are typical on automotive suspension air springs.

I would think it is the stroke that would cause problems for a simple diaphragm.

Different pressures as well I guess?

[wuzak]

Different pressures as well I guess?

Yes, I would think so. Not sure how that relates to the suitability of the diaphragm.

It may be that a diaphragm requires more power to use, due to the material being deformed (even though it is soft).