Pneumatic valve train prototype

[Brian.G]

Hello folks, I thought Id post this here as some maybe interested.

My intent is to find out all I can about this device by building a prototype.

My main goal is to see If I can build a reliable item. I have done as much research and thinking as I can for a few yrs. It is now time to build an actual item to start testing on.

Ill be designing and making everything in house. Its a pretty simple test jig really, imagine just one valve and parts cut from a head, thats what It will resemble.

Since NO information exists on these, it is the only way to develop one. Ive read all the usual stuff. I thought of buying one off DelWest for testing, but they dont supply anything, instead design from scratch for your needs, at a cost of around 300K.
Nobody is will to share Info either, which I guess is ok, Im sure they have signed a ton of NDAs.

A fast rundown of the parts in mind.

A 40mm valve. Ill be turning this from Ti to have weights within what I hope to use later on. Its going to have a 7mm stem for the time being. I may waist it down in the port area for lightness.
The main body will be a cast housing.
The plunger will be Ti.
The piston housing will be an alloy sleeve, hard anodised in some xxxx spec I have to pick yet.
The finger follower will be steel. Im not putting that much design work into the follower geometry as yet, I simply want it to function. Although it will be designed in such a way as to prevent/minimise valve stem side loading.

Ill be cutting/grinding the cam also. The lift will be around the 15mm mark.

For the collet/retainer, I may make these, but Ive some on order from ducati which Ill look at first.

My target rpm is around 15-18krpm.

It will be oiled with an aux oil pump and assembly. Ill also probably heat the oil to around 120ish.

The guide will be silicon bronze of some sort.

My main concern at the minute, is getting some oil to the stem given that there is an 'air tight' seal there. But Ill figure it out in time. And also plunger galling to the bore walls.

I dont know how long its going to take, and I dont care, something to pass the time in the evenings right...

To view the valve contacting seat at high rpm, and to make sure its not bouncing Ill be monitoring it.
I haven't made up my mind just how yet, but its simple once I do so.
My options are
Stroboscope.
Proximity sensors coupled with an oscilloscope.
Fiber-optic interferometer.

Obviously these setups range in cost vastly, so perhaps Ill start with the strobe, and some for of macro viewing/capture device(camera)

Im doing all drawings and calculations on paper with pencils, so it takes a while. But, Im ok with drawing boards.

The reason for doing all the above is to develop a usable valve train for use in a single cylinder 4 valve test engine. This engine will have a bore of 98mm, and a stroke of 39.7mm. Target rpm is 15.5-16krpm.
I will use this to study a variety of things but mainly con-rod design, and journals.

The test engine is a while off, since I have only started drawing it about two months ago. You cant imagine all there is to think about in something that is technically a glorified lawnmower engine. But, Ill get there.

I hope it will interest some, as its what I wanted to do for oh...20yrs now...

Materials are not particularly dear either for the valve assembly, I cant even remember what they cost. The dearest thing is time, but thats free if its your own to pass.

Brian.G

[flynfrog]

do you plan on doing a once piece bladder or more of a piston with a seal? There are a lot of brilliant people on the forum who love projects like these the more detail you can post the more detail they can provide.

[Brian.G]

do you plan on doing a once piece bladder or more of a piston with a seal? There are a lot of brilliant people on the forum who love projects like these the more detail you can post the more detail they can provide.

Piston and seal at first, but Ill try anything until I reach my targets, no matter what it takes.
Dito on the great people,

Brian

[flynfrog]

Could it be as simple as High temp Oring. I think your losses will be kinda High might need a big air pump.

[Brian.G]

Could it be as simple as High temp Oring. I think your losses will be kinda High might need a big air pump.

The thought occurred to me to use itself as the pump, constantly topping itself up if it needed it against a preset reg. But, again, this is what this is about, to try everything out. The valve (air) bank will be arrangeable.

Brian,

[mep]

Huy that is an ambitious project.
Even so when the pneumatic valve train might not be complicated in principle, it's just some compressed air used as spring if I am not mistaken, it will probably become very demanding when it comes down to details and sealing.
I guess you have some machines available, a lathe and a mill and you are familiar with the use?

The reason for doing all the above is to develop a usable valve train for use in a single cylinder 4 valve test engine. This engine will have a bore of 98mm, and a stroke of 39.7mm. Target rpm is 15.5-16krpm.

Do you have this engine already or where will you get it from?
For me it seems to be a pretty big engine for a single cylinder. Also the bore/stroke ratio seems to be strange, or is it just me?
I recommend you to use an existing engine and try to add your valve train. Building your own engine from scratch + adding pneumatic valve train is a way to big project.
Will you use pockets for the valves in case something with your valve train goes wrong?
Good luck and keep us informed.

[bettonracing]

While it sounds like this isn't intended to be a profitable venture, You may want to leave the option open.

Consider mfg a single cylinder version of the Honda K20 engine. Many readily available parts - new, used, and aftermarket - and after You've come up with the-next-best-thing-since-sliced-bread (<-- not intended tongue in cheek), You'll have a marketable product. All those racing categories with 2.0L (+/- 0.4L...) restrictions would be a potential market (even though it's an already saturated market).

Saves You the time of designing all the complex areas of a complete engine (matching the combustion chamber to the cam profile comes to mind) until You're ready to focus on those specific areas. In other words, it would reduce Your development time (& likely cost), as well as reduce the amount of variables You need to get right in Your first cut. Something as simple as spark plug selection now becomes a design process, instead of a trip to the parts store.

If You were able to produce a K20 4cyl running at 16k rpm (or higher), You probably wouldn't be able to produce them fast enough. Or, after You've improved the overall engine design thoroughly enough, You'll be able to (morally and legally) call it Your own: The Brian.G.DFV Last but not least, if You were to produce components as radical as pneumatic valves, I'm sure race teams everywhere would at least pay attention to see results.

Another advantage of starting from an existing engine is You can start a blog (of some sorts) and put up Your wish list of parts, and give fellow F1Technical members a opportunity to donate to Your cause (without feeling like You're begging for money)...

Food for thought.

Regards,

Kurt

[flynfrog]

I would recommend one of the Honda clone engines. You can get them for $100 or less and they have a large after market already. I have a couple of them floating around the shop. One of the big problems is valve float on the high revving motors. That and when they blow up you can score another for $100

[Brian.G]

Mep, yes indeed, all machines here. I also have the ability do to all my own casting and heat treat too.

No, I dont have the engine already. I know how someone else could think this is a big project, and Ill agree that it is, but Impossible, no, its just what your into, and what you desire to see done.
Pockets in the crown? I doubt it. When Im finished loads of testing, Ill be confident.

Kurt, thats actually a great post. Many people who wouldn't know you would laugh at such an idea. But Im pretty serious.

As for making money, thats a nice idea, I have the ability to cast a head also if I wanted. The testing is done in that department already, for ages. The biggest problem I had with heads, is the area where the valve guide sits. This is a big mass of material near the thin port walls. And when it solidified it used to tear the test ports. But, Ive figured out all that now by using a pencil chill in that area. There is no other problem in casting a head as far as Im concerned once you break it all down, and think in the negative form always when designing so your moulds will all work.

Its a great idea about the honda parts in fairness. Perhaps someday I will do that. But first, I need to construct my own test single cylinder because Ive wanted to for an age. Its not a dream either, Im 20yrs thinking about it!

Its all about sharing my findings I guess, since no info exists on some of the finer parts. Ill post up the single valve train here first anyway. Theres a good mix of stuff in it, casting, machining, screwing things together, testing, etc, so Im more interested than anyone as to what can be achieved.

Thanks Kurt,

BG

[mep]

How are you doing the casting?
Some pics about that would be a nice start.
However I would still start with a of the shelf engine and modify or add a self casted head with the pneumatic valve train.
I can't imagine there is nothing available about it in the net.

[riff_raff]

Brian.G,

As a mechanical engineer, I have to say your project sounds like lots of fun.

But from a business standpoint, I'd have to say that you're probably wasting your money. Sadly, there is no commercial value in a pneumatic valve spring system, regardless of how technically superior your testing/analysis may show it to be over the current pneumatic valve spring state-of-the-art.

Regardless, in response to your specific questions:

A) You'd be better off doing as much simulation and optimization of your device using analytical tools such as ANSYS and MATLAB, prior to building any hardware. While these softwares are expensive, in the end they would still be cheaper than building and testing multiple sets of bench test hardware.

B) With regards to pneumatic springs, having low frictions and leakage is paramount. So using flexible diaphragms has replaced o-rings. And having extremely close tolerance fits between mating parts is also critical, which would require common materials.

C) The primary benefit with high-rpm pneumatic valve springs is the ability to vary spring rate over the rpm range. This requires a variable gas pressure feed rate.

D) The best way to get high-frequency measurement of valve displacement vs. time data is probably by prox sensors (non-contacting) or LVDT.

E) A dedicated valvetrain test rig will be less expensive, but it will not include the effects of cylinder pressures on the valves.

Good luck!
riff_raff

[Brian.G]

When did I mention its going to be a business
As a Mechanical Designer, the day jobs pays plenty fine.

This is what Im doing in my spare time as mentioned.

A. Understand, but as you know, simulations dont prove real life tests, which is why we still conduct real life tests.

B. As mentioned, Ill be testing many. O rings did the job for a long long time.

C. Yes, I Know, and designed.

D. See above,

E. More so with the exhaust, but the bore can be pressurised to simulate.

This is not a weekend project,

Thanks the the pointers, all counts,

BG

[Carlos]

It's always worth reading the literature, this might be of interest:

Pneumatic Actuating Systems for Automatic Equipment
PMed the details.

"... recent progress not only in the pneumatic systems themselves but also in the integration of mechatronics, electronic control systems, and modern control algorithms with pneumatic actuating systems..."

[Brian.G]

Thanks Carlos,

Drawings nearly done of basic jig, will post a few shots later,

Brian

[hardingfv32]

The Lamborghini F1 engine parts I have, the retainer holds a seal that travels in a aluminum cup/chamber. I did not get the seal, but it is not an O-ring. More like something with a 3 mm square profile. The cup looks anodized, but polished to a mirror finish.

Brian