Well, all the hard work I put into that diagram goes to waste. It keeps deleting all the spaces. Oh well :flaming:

Man I had to look that one up. Neat mechanism but no, not what we were talking about.

I had to look that one up too... Once I saw it, I realized I've seen a design that used it before. I think they used them on some old motorcycle engines. It seems like the little pin and slots would wear pretty quickly, but it might work if it were part geneva mechanism, part normal gear..... it looks weird in my head and is probably not even possible, but now I want to draw one.

The idea is for it to work like a 4-position geneva mechanism for exhaust and intake, but use a normal gear to turn through the compression and power strokes. The way my valve is situated, the pressure from compression and power will make it seal more tightly, and also make it more difficult to turn during those strokes. So, it would be 1 position per stroke, but only for half of them... a half-linear gear of sorts.

You guys just keep making my brain go off on these nice mental exercises, and I think in the end it will result in very good things. :nod:

I've seen "gears" that were part geneva mechanism and part gear. Before the advent of stepper and servo motors manufacturing machines used cams and gears to do the movements that are now done electronically. Everything was done mechanically. Oval gears, square gears, rotary to linear mechs, linear to rotary, all kinds of ideas that got the job done.

http://www.dself.dsl.pipex.com/MUSEU...alveIC.htm#mel

Good reading there. When I did some digging on various types of unusual valve mechanisms I came across a fascinating overview of different types of mechanisms for steam engines. Absolutely amazing combination of mechanical complexity and in a way simplicity as well. Those guys were geniuses.

Well Mr. Maximillian, you first told me to go to and do some reading, and then you come to say that you find me comical. I dont know about your tongue, but your fingers run on ball bearings. As if you know what I have or have not studied. What I've worked with and what I've havent.

In this thread - actually in many others too, I've seen you trashing anyone who doesn't think what you think - you are the only person that has insulted anyone and the only that has made the stupidest "arguments", if you can call it that, comparing apples to maybe rotten oranges, and then you come and you've been talking, cover yourself like a kid and say that you dont talk because you dont know, well guess what, defending it without an argument is ridiculous, pittyful indeed. Maybe you think you had an argument, even worst.

You even look naive believing a salesman that has not sold his product in 15 years to anyone.

Obviously not today, but Dude, 10 years ago GM, Ford, Toyota, Mercedes, and probably ten other brands had the money to not only buy that design, buy the designer, his children and grand children. An F1 team spends over$250,000,000 in their racing season, believe me, Ferrari shows a check to this guys for half of that, The whole company probably does a collective shit on their pants. I've given reasons leading to good arguments, you can agree, or not, but come back with one of your own.

This thing may work, who knows, but everything points in the other direction when you consider the common racing poppet valve, that is a fact that you only look childish if you deny. I have no problem with being wrong, I've been wrong before, and I would love to be able to take that valve out of the way, but I wont just believe the first crap that apears in front of me becouse someone says its good or it looks cool if every single physical characteristic it has says the contrary.

Get your arguments straight. Kid.

Guys, use the PM button if you want to argue.

Even if some ideas, concepts, or information may not be right, proven, or were complete failures in the past, it still makes us think - and great things come from creative thinking. In my mind, that is what is so great about this thread.:nod:

I love the flow of information and ideas in here. Let's keep it rolling.:tire:

Stroke will be the same as a "long stroke" .21 buggy engine.

So, when I got out of the shower last night after coming home from a race, I had a little flash of an idea of how to use the crankcase to supercharge a 4 stroke engine. You could simply valve it with reed-valves. The intake charge would get sucked into the crankcase when the piston goes up, then pushed back out into a the intake manifold as the piston goes back down. This would happen twice as often as the intake stroke, so I'm guessing it could give a significant boost without adding more rotating parts. Of course, other types of valves could be used, but it's just a generic and random idea at this point.

Has anyone ever seen this used in any type of 4 stroke engine?:weird:

The closest I've seen would be the Husqvarna 4 stroke MX engines of the early eighties. They didn't have a regular oil pump (for weight and parasitic loss reduction), but had a reed valve in the bottom of the case to control oil flow. When the piston moved down and pressurized the crankcase, oil would be forced through a small reed valve and on its way through passages to where it was needed. This created the pumping action. Worked OK as long as the oil was changed OFTEN, and was high quality synthetic. They were air cooled, didn't carry much oil (by 4 stroke bike standards) and had a rep for cooking the oil (and failing).

Two stroke (GMC type) diesel engines use an external supercharger to pressurize the crankcase. The engine has exhaust valves in the heads, but no intake valves. The cylinders have ports like a two stroke gasoline engine.

I think you wouldn't have any gains by having the engine draw the intake charge into the crankcase and then forcing it through some other valve (reed or otherwise) into the cylinder (only using the botom of the piston as your 'supercharger'). Remember that the pumping action is the same on both sides of the piston. You'll have losses rather than gains. Now using an external supercharger to pressurize the crankcase on the other hand would be a different story, and would allow you to get plenty of lubrication to the lower end.

I haven't seen an engine using it, but again, the reason is likely based on energy loss. The problem with that system is given by the actual lower crankcase compression. Since the case's compresion is so low relatively speaking, there is not enough energy to supply the combustion chamber with enough fuel/air at the higher flow/rpms.

When the valve opens in the usual combustion chamber in a high compression 4 stroke, there is so little space in the chamber at TDC that the pulses that the piston produces as it moves up and down are reflected with very high efficiency so there's a lot of energy to move the gases to and from the chamber to fill it up. Actualy the higher the compression, the easier it is for the engineto breath at high rpms.

X

Hmmm. I thought it was a good thought experiment. I understand the crankcase is not efficient at pumping, but it's how many high-peformance, high-RPM 2 stroke intake systems work.... and they only get one "pump" per intake, where the 4 stroke version would get 2.

Again, it's something I would love to try and may not work at all... Maybe something to try sometime later on.

You are absolutely right on that, but the 2 stroke engine is not that good in volumetric efficiency, its the actual "one combustion per every other stroke" what makes "the good overtake the bad", BMEP on the racing 2 stroke usually is not high compared to the 4 stroke counterpart, which is the real measure of efficiency and thus, torque production at a given rpm. The 2 stroke combustion process is very dirty, the fresh mixture mixes a lot with the used one, so it's unlikely to get the eficiency of a 4 stroke if we consider only the power stroke, the 4 stroke's cycle stages are so well separated that they can do their respective jobs better, without the intrusion of the next stage. It's easy to see that in a 2 stroke, the overlap of the intake ports with the exhaust port is 100%!, in a 4 stroke is what, 5%? just around TDC.
So what I'm sayin is that the 4 stroke uses more air, rpm being the same.

X

I completely understand... but there's a part of my brain that won't let it go.

It's definitely on my "want to try" list. I'm going to have lots to do this winter during the off-season.:D It could be done fairly easily with an existing engine, and probably could be better than reed valves with a backplate-based rotary valve driven the same way a pull-start shaft is. I'll need to make a test stand with some sort of dyno so I can tell if it's a gain or loss.

The day we let it go is the day we stop learning. :nod:
There's something I really like from that system, in a single cylinder 4 stroke like ours, how do you properly seal and lubricate the crank case? and how do you keep the preasure pulses from blowing the front engine seal? with reeds andair/fuel passing through the crankcase lubrication is not a concern and the preasure delta goes down considerably. that could be preatty cool.

X

Here's another idea I came up with while shaving the other morning:

A sliding valve that works similar to an electric shaver.. 3 steel plates with many small slots in them -

The top one is stationary, and the slotted area covers the entire top of the combustion chamber (except for the glow plug). The intake and exhaust ports could each cover half of the combustion chamber except for the glow plug area.

The bottom plates slide the distance of the width of one of their slots (very little movement). It's reciprocating, but since it doesn't move very far, it could be actuated by a very non-linear captured cam, thus requiring no springs.

Of course, the limitation of this design is that each open "port" could only account for less than 1/4 of the total cylinder head area, but there would be very little time spent opening and closing valves. Each valve's cam could also have an independent profile.

The other cool thing about it is I think the valvetrain would be much more compact than my other rotary valve designs. It would also have a very tidy combustion chamber with a centered glow plug. It even has the potential to be designed with a hemispherical or slightly coned shape - of course flat is easier to make...

YS does very well with crankcase supercharging in their four stroke engines. It is effective and efficient. It has been attempted one way or another many times over then last 30 years. I found maybe a dozen patents for such systems.

Greg

Doesn't YS use a supercharger to pressurize the crankcase ? That's not using the engine's piston to 'supercharge' the the intake air/fuel like DP was thinking of. I suggested to DP that using an external supercharger to pressurize the crancase would work well. The YS engines have the supercharger built into the back of the engine, but it is still external (or rather seperate from the piston)...

Two stroke engines do move the intake charge through the crankcase and into the cylinder via ports, but don't 'supercharge' the intake charge. I didn't say the engine you proposed wouldn't run at all....just that it wouldn't have an advantage over a conventional four stroke that breathes straight from the carb to the intake valve (and certainly not one that has a supercharger).

I believe the 4-Mix engines that Stihl makes (for some of their string trimmers, brush cutters, and backpack blowers) breaths through the crankcase some how. It does have valves....is a four stroke....and doesn't have a seperate sump of lubricating oil. It runs on premix...

Take a look at one.

http://www.google.com/patents?id=zcY...age&q=&f=false

http://tech.flygsw.org/ys91.htm

If you guys haven't studied the history of model airplanes engines you are missing out on a lot of interesting designs. Think the RCV concept is original? it was done by a German company in the 70's. Four stroke with reed valved crankcase supercharging and Aspin valve, Webra early 80's, though the engine wasn't strong at all.

I bumped into this today.

http://www.youtube.com/watch?v=eJlE-1dmEak

Greg

Interesting. The YS I looked at years ago had a roots type supercharger on the back of it (as did a supercharged OS I saw around the same time)....not that air chamber thing on the engines you linked to. Realy cool stuff you linked there. Same guy at the field also had a Webra with belt driven cams and an HB with the rotary valves. Neat. I've been into old model engines for decades. They've tried some weird stuff over the years. Always wanted to play with an OS wankel...

I'll have to do some searching. I've never heard of a Roots type YS. Webra engines were all rotary valve. There was an OPS OHC belt driven four stroke.

Greg

It was in the late '80s that I saw that YS IIRC. Big roots type blower behind the backplate, similar to the supercharged OS four strokes. Makes sense that those belt drive Webra's had rotary valves. The head wasn't tall enough for there to be rockers up there...

The HB rotary valve four strokes had a shaft that drove the valve rotor. The shaft tube in the front reminded me of a bevel drive Ducati. I never saw one of those engines disassembled...

I don't remember seeing any OPS four strokes. Their aircraft engines weren't popular here for some reason. The only OPS engines I have any experience with are their 2 stroke car and boat engines. That square head .90 was a BEAST!

The OPS was a 1.20 size. It's hard to find any info and the engines are rare. HB are bevel gear driven. I have a few and have had one apart.

On the louvered gate valve you'll want to check what the flow coefficient of that might be. Doesn't sound good to me.

I love big four strokes (especialy the sound). I hope to see one of those big OPS four strokes turning a big prop some day. The OPS .90 I refered to was a watercooled 2 stroke inboard boat engine. It was a beast, and looked the part due to the big square jug. I understand they still make them.

I just remembered that the HB valve drive shaft (and the tube it runs in) is in the rear of the engine (not the front like I said earlier), and the carb is in the front (aimed downward at an odd angle). The HB was also available in a .25 car version, with big vertical fins on the head. Never saw one of those in person.

I agree about the louvered gate valve. So many port edges mean a lot of turbulance. High speed airflow will be lousey I'm afraid.

what about a rotary valve running off the crank like in the old boat motors

That's pretty sweet that some of the YS engines supercharge that way. I have to admit, I just assumed they were using an external supercharger.

I had also wondered about the extra turbulance that a slotted port design would introduce. It does greatly simplify (and compact) the valve assembly, allows the glow plug to be centered, while allowing a non-linear opening and closing. I wonder if these advantages would matter...

I can totally see how flow would be impeded by small slots vs one large open hole. ...especially with liquid flow, as surface tension would probably really kill it - BUT, we're not working with liquid. There's got to be a way to make a rig to test gas flow through a few different arrangements of slots, holes, etc... I'm sure one already exists for physics type experiments.

I should really do some experimentation with that sort of rig before deciding how I want to do the valve. It shouldn't be that hard since all I want to test is relative flow rates - I don't need hard numbers, just "is this one better than that one" tests.

So, I think I've figured out how to fairly easily build a flow tester of sorts.

I can use water as long as I keep the surface being flow-tested submerged - that eliminates surface tension. So, the "test rig" consists of a 2 liter bottle with a few different caps - each with a different "port" cut in it. Drill a hole in the bottom of the bottle as a vent. Plug vent hole. Fill the bottle with water. Fill a sink partially with water so the bottle cap can be submerged during the test. Screw the test cap on and cover the "port" with thumb. Turn bottle upside down, submerging the bottle only to the neck. Pull the vent plug. Uncover the port and start the stop-watch at the same time. Stop the timer when the water level reaches the neck. Keep the bottle's neck level with the water in the sink the full duration of the test.

My high school physics is a little rusty, but I think this will give me a good comparison of flow rates of different types of ports.

I think you'll need to account for viscosity and reynolds number effects. Why not use air? Rotameters are fairly cheap on thebay. Vacuum cleaner, throttle, rotameter, dummy cylinder with valve arrangement.

I just ran into a website with some info about the OPS 1.20 four stroke. I don't know if this is current or just informational. Bottom of the page.

http://www.mantuamodel.com/index.php...elli&Itemid=92

Greg

That OHC engine is pretty!

I hadn't thought about just using a vacuum cleaner. That's a good idea!

I wanted to let you guys know I still have ideas swirling around in my head about how to make the first prototype - regardless of the type of valve I decide to use.

Since I'll be trying to replicate all the current .21 engine specs (mounting-wise, etc...), I'll just start out with something like a VG-30. There's a pull-start version, so it'll have the nub on the end of the rod journal to drive the supercharger valve (if I decide to go that route) and valvetrain. It also has a fully functioning induction valve and a very standard place to mount the carb if I decide to try supercharging. Most importantly, it's got a long enough stroke for the larger displacement thumper. If I can bore out the cylinder big enough to fit the FS40 sleeve, it'll just be that much easier. If not, I know a guy who could weld a machined cylinder to the crankcase easy enough.

Basically, it's just that much less stuff to design/engineer/prototype/test to get the very first working prototype. I'm sure this method will save lots of money and time.

With the racing season wrapping up this month, I should have a little more time to work on this.

The other day I thought of a variation on the slotted valve idea that would allow almost 2/3 of the valve's surface area to be fully open vs the current limitation of almost 1/2. It requires 2 sliding components per valve and offset sealing surfaces, so it would be much more complicated and expensive to produce... Probably never see the light of day, but it is an interesting concept to think about.

Well, I ordered the VG 30 yesterday, so I'll have something to play with by this weekend. First thing is to figure out if the 40 sleeve will fit in that block or if I'll need to make a cylinder to weld to it. Then it's on to fitting the piston to the rod. THEN, on to the valve train/supercharger valve.:D:D

THEN, the hard part - the cylinder head.:sweat:

The way the prototype is designed, I can easily switch between normally aspirated and supercharged. That way it'll be easy to tell if it is worth doing.

Cool. I look forward to seeing some chips flying.

Greg

I did some more exact calculations on how much surface area is available for air flow through poppet valves vs the sliding valve. The slider has a slight "fully-open" area advantage. I based the poppet valve numbers on the biggest diameter valves that will fit in the FS40 cylinder, with a lift of 2.6mm (which I measured from the Alpha 56). Taking into account the very quick opening and closing mechanism I've got planned, area under the curve should heavily favor the sliding valve.

I can't wait to be able to work with more than numbers and drawings.:nod:

any update.

Got the VG30 last week. Racing this weekend, so I only got as far as tearing it apart.

Little update:

I've begun the drawings for the backplate/supercharger/valvetrain assembly. I also figured out another way to use poppet valves just in case... :sneaky:

It would end up being a 4 valve hemi - head with smaller exhaust valves and a centered glow plug. Very common in full-size engines, but I haven't seen it in small glow engines. Does anyone know if there's a smaller diameter glow plug? That would help with the valve size if I end up designing it that way....

Unfortunately, there are no smaller glowplugs. You have either 1/4"-32 or turbo. With having to make room for the plug, I don't think you'll have more valve area with 4 than you will with two.

You've probably run into this in your research.

http://www.radiocontrolmodels.co.uk/...n/Page2852.htm

Greg

I had that thought too. The .40 jug is pretty small. It may have to be a 3 valve head with the glow plug where the 4th would normally be. 2 small intake, 1 large exhaust. I'm pretty sure I would want it to be OHC too.

It is more of a backup plan anyway. Thanks for all the cool links! If nothing else, I will have seen all kinds of really neat engines because of this project.:D

It's been a while... but I've scheduled to get some machine work done Sunday! It's just to fit the sleeve to the block and to make the small-end of the rod fit the FS40 piston pin, but it's SOMETHING.... Bathroom remodels and that pesky real life keep getting in the way, so I'm happy that I'll finally have something CUSTOM to hold in-hand and analyze. :nod:

Oh, and I've been thinking alot lately about all the different valving designs I've contemplated. I'm pretty sure I'm going with the slotted sliding design with the centered glow plug. I'm currently contemplating making the cylinder head a larger diameter than the bore to allow more room for the valve opening. Since it will be flat and I can make the piston come all the way to the top of the sleeve, I can expand the squish chamber to the side instead of up, gaining some valve area on the outside where it counts most.

One down-side of the valve design I've chose is I have to choose between an equal number of intake and exhaust slots, or having them differ by 2. The more slots, the harder the whole thing becomes to manufacture and also I lose valve opening area to allow for sealing area for each opening, so I've been throwing around 5/7 and 6/6 which makes 30 degree slots. 5/7, makes for an intake/exhaust ratio of .71 which I've read is too low for supercharged engines - it's more of a number you'd want to make more torque at the low end on a normally aspirated engine. From what I can gather, numbers closer to .9 are better for higher revving supercharged engines. These are the things that keep me up at night.:lol:

Baby steps
 

Here's the .40 sleeve and piston in its new home. The wristpins on the FS40 and VG30 are the same size, so I didn't need to modify the rod at all to make it fit. You can't really see it in this picture, but the exhaust port is no longer. Now I have something real to start designing the head for. :nod:

Great! Keep going. I'm almost done setting up a "new to me" lathe and working on a 4th axis fro my mill. I hope to be building some engines this winter!