# Engine Valves



## vederstein (Sep 23, 2020)

I've done enough Steam and Stirling engines that I think I'm going to try my hand at a four stroke gas engine again.  My first experience was a Webster where I failed to get the thing running.

My question revolves around valves.

Why always poppet valves?  I had a hell of a time getting the Webster exhaust valve to seat and seal.  Perhaps this was the root cause of my failure?  (It could also have been the carburetor, which I made according to plans but learned later that that design was pretty much ****.)

In my steam engine designs I've had good success with spool valves.   A piece of drill rod and a reamed hole will give an very close fit.

So,  why can't an internal combustion engine have spool valves for the intake and exhaust?

As usual, I'll probably design my own engine with some inspiration from existing designs.

But the question still haunts me.  Why can't an IC engine have spool valves?

Comments?

...Ved.


----------



## earlwb (Sep 23, 2020)

These engines don't use poppet valves:
You can look it up but HP made the VT-21, 25 and 49 series of Aspen valve four stroke engines. It tends to remind me of a Ducati motorcycle with the shaft drive to the overhead Aspen valve.
The Webra made T4-40, 60 and 80 (and maybe a 91) drum valve or rotary valve four stroke engines. They use a belt to the top of the engine, reminds me of a overhead camshaft engine.
OPS also made a 1.20 or 20cc drum valve four stroke engine too. it also looks like a overhead cam type of engine.
RCV made the inline and upright sleeve valve four stroke engines in .58,.60, .91, 1.30 sizes. They have moved on to making larger drone engines for the military and commercial interests though.  These engines use a cylinder sleeve that rotates in the crankcase. There is a port at the top that rotates to the intake, then compression and exposes the glow plug, then on to the exhaust. The sleeve valve engine was used in some huge full size aircraft and bomber engines. The upright engines look quite normal but the inline engines are pretty neat though.

ref http://www.mecoa.com/hp/vt/21.htm

ref Webra T4-80

ref Steve Webb Models

ref RCV Engines Home | Specialists in multi-fuel engine technology

ref Sleeve valve - Wikipedia


----------



## vederstein (Sep 24, 2020)

The valve design of the RCV engine I like quite a bit.

Based on this I think my ideas may have some merit.  I'm going for simple, not exotic.

Therefore, when I get into the design work, I'll have to keep in mind of the valving.  If one valve technology is a bust, then I need to design the engine in such a way that the valving can be changed.

Thanks,

...Ved.


----------



## earlwb (Sep 24, 2020)

You can peruse the model engines reviews here for various model engines such as the rotary valve and sleeve valve engines.


			Model Engine Tests
		


For example:
OPS 1.20, RCV engines, HP VT-21, and Webra T4 series engines. Some of the articles or reviews go into more detail with them taking the engines apart to study too.
OPS 20cc 4 stroke for example OPS 120 4C
RCV 58-CD   RCV 58-CD
RCV 120-SP  RCV 120-SP
WEBRA T4-40 Webra T4-40 (1)
HP VT-21  HP VT-21


----------



## ranger (Sep 25, 2020)

Hi,
Google “ Condor 120 model engine “. I had one in the early eighties, this engine was made by Dennis Allen of A. M. and Merco fame. It has a belt driven overhead rotary drum type valve incorporating both inlet and exhaust ports. The inlet entering from the side and the exhaust “ exhausting “ from the end, so relatively simple to machine the cylinder head. One advantage of building an OHV type of engine is, when you have the bottom end finished you can experiment with different types of valve design ie, OHC : Aspen etc by making another cylinder head and valve design to suit, still using the belt drive for operation.
Doug.


----------



## vederstein (Sep 25, 2020)

I wonder why these alternative valving mechanisms didn't hold up?

That Condor engine seems like a four stroke version of a Corliss steam engine valve.  It seems very simple to me with the valving being one rotating assembly.

Perhaps carbon buildup and/or compression leaks were an issue?

I do like the concept though.


...Ved.


----------



## johwen (Sep 25, 2020)

Hello Ederstein,
There have been many different types of valving in the larger engines and success was never as good as the simple poppet valve. Sleeve valves were attempted dual sleeves then single sleeves rotary valves in head and all had the same problem and that was lubrication all burnt oil or if the didn't they seized. I have an engineer friend who has built Overhead roller valve heads for a ford 351 V/8 the rollers weigh a ton and the engine smokes and has to have a continuous drip oil feed. All this to extract more power so far a failure. The hours and cost if spent on developing the standard layout with cams an blowers and carburation would have been a tyre shredder.
The way to to get poppet valves to work and seal is not so hard if you are patient. first machine the stem in say 1/4 inch steps to size until you have the correct length, then machine the valve head and seat angle polish the stem. Put your retainer groove in the stem during first 1/4 inch. Do all this at the one setting so all is concentric.
When you do the valve seat if it is bronze insert put it in place first and then cut the seat. I usually don't cut the seat being bronze you only need to give the valve a tap with a brass punch and if the edge of the insert is sharp the valve will seat itself nicely. John


----------



## ranger (Sep 25, 2020)

vederstein said:


> I wonder why these alternative valving mechanisms didn't hold up?
> 
> That Condor engine seems like a four stroke version of a Corliss steam engine valve.  It seems very simple to me with the valving being one rotating assembly.
> 
> ...


I think the main problem with full size versions of this type of valve is to do with unequal temperatures and expansion of valve and head causing sealing issues. With model engines ie the Condor, running on Methanol and castor oil, ( total loss oil, mixed with fuel), this is less of an issue. You could probably use a cast iron sleeve in the head with a cast iron valve to minimise differential expansion problems.
Doug.


----------



## earlwb (Sep 25, 2020)

One problem was combustion chamber shape and then compression ratios. The rotary drum valve engines and top hat rotary valve engines are limited into how much compression they can get. The flat disc or Aspen Valve engines came out to help solve that problem. Then there is the combustion chamber shape cannot be optimized for best combustion.

The next problem was valve timing. Valve timing is somewhat limited due to a valve has to close before the next one opens. It is very difficult to get asymmetrical valve timing to increase performance.  They did try multiple sleeves to solve the problem, but then that led to more problems than it was worth.

Then with sleeve valve engines there is a heat transfer problem from the moving cylinder sleeve outwards.
Then as Ranger stated, sealing and leakage is a problem too. With model engines it isn't as big of a problem as it is with full size engines.

But then they did solve most of the problems with the huge Centarus engines used by the British Aircraft, up until the jet age took off.


----------



## ranger (Sep 25, 2020)

earlwb said:


> One problem was combustion chamber shape and then compression ratios. The rotary drum valve engines and top hat rotary valve engines are limited into how much compression they can get. The flat disc or Aspen Valve engines came out to help solve that problem. Then there is the combustion chamber shape cannot be optimized for best combustion.
> 
> The next problem was valve timing. Valve timing is somewhat limited due to a valve has to close before the next one opens. It is very difficult to get asymmetrical valve timing to increase performance.  They did try multiple sleeves to solve the problem, but then that led to more problems than it was worth.
> 
> ...


I seem to remember reading somewhere that the first Bristol sleeve valve engines were rejected by the Air Ministry because they didn’t meet the MINIMUM requirements for oil consumption!!! Bristol had to increase machining tolerances to use more oil. Apparently the boffins decided if an engine didn’t use a certain amount of oil, it was likely to seize.


----------



## Anatol (Sep 27, 2020)

Hello Ved and all - this thread is very interesting to me as I continue to be interested in alternatives to the poppet valve. Historically it seems poppet valve became obligatory as pressure and rpm increased, ie with uninflow etc. Doug Self has lots on rotary valves for steam and IC, The Museum of RetroTechnology (I love his site) and its pretty much a story of ongoing failure. I'm also reminded of Tom Kimmel's remark, 'there are two kinds of valves, poppet and those that leak' or words to that effect. I'm not a locomotive guy but it seems there are lots of spool etc type there - they're essentially round versions of slide valves. I'm more interested in rotation types continuous opr reciprocating, like trevithicks on puffing devil. My interest derives   from looking at automotive IC valves and specifically their return springs, which are huge, in order to close the valves fast -  this is wasted engine energy. I don't have numbers but it seems to me a constant rotation valve would be most efficicient. Does anyone have ideas about this?  prefereably with data to back them up


----------



## johwen (Sep 27, 2020)

Koenigseig in Sweden has perfected a fully electronic controlled  poppet valve system that eliminates a camshaft throttle valve can shut down cylinders independently change and vary valve timing to suit engine revs etc. For slow speed the valves are just cracked open and to increase engine speed the valves are opened increasingly more and timing changed by opening the valves earlier and closing them later in a continuously varying manner. Power and torque have massive increases over conventional systems and a significant saving in fuel consumption. Valves are opened and closed by solenoids. Overall height of engines are much lower as there are no camshaft or valve operating gear as such Cheers Johwen John not sure i have spelt the manufacturers name correctly


----------



## earlwb (Sep 27, 2020)

Anatol, there is also the way Ducati and some others did it with poppet valves. They use the cams to both open and close the valves. They only use weak valve springs to help close the valves for starting and idling. it is Ducati's Desmodromic valve system. Thus they solved the problem with valves floating at high speed and the need for heavy extra strong springs.








						Desmodromic valve - Wikipedia
					






					en.wikipedia.org
				




Oh yeah, the Aspen valve system is what you might call a constant rotation valve.


----------



## johwen (Sep 27, 2020)

earlwb said:


> Anatol, there is also the way Ducati and some others did it with poppet valves. They use the cams to both open and close the valves. They only use weak valve springs to help close the valves for starting and idling. it is Ducati's Desmodromic valve system. Thus they solved the problem with valves floating at high speed and the need for heavy extra strong springs.
> 
> 
> 
> ...


Most High speed racing engines in MotoGP and Formula One grand prix engines use compressed air to control valves as springs don't work that well at the revolutions that they run at. They have compressors to pump up the pressure.. Cheers John


----------



## Anatol (Sep 28, 2020)

earlwb said:


> Anatol, there is also the way Ducati and some others did it with poppet valves. They use the cams to both open and close the valves. They only use weak valve springs to help close the valves for starting and idling. it is Ducati's Desmodromic valve system. Thus they solved the problem with valves floating at high speed and the need for heavy extra strong springs.
> 
> 
> 
> ...



Earlwb - thanks I know about the desmodromic system.  
Johwen, thanks also I've read about this  technology. Mechatronics will be the answer, I'm watching piezoelectic valve research. 
regarding the  Aspen design - I googled it and got zip relevant hits. I went back through  the thread but didn't find a link. Could someone please post a relevant link?


----------



## earlwb (Sep 28, 2020)

I had found some information. They seem to just lump in the Aspin valve engines with rotary valve engines.





						Aspin valve - Wikipedia
					






					en.wikipedia.org
				



and


			aspin.info
		


They had a model engine review of the HP VT-21 engine here where they took it apart to view it: HP VT-21

I ran across this list of engines using a rotary valve.





						Rotary-Valve Internal Combustion Engines. Workbench Tool Box for Private Workshops.
					

Douglas Self, rotary valve engines, Minerva, Aspin valve, Cross valve, Froede valve, Wankel valve, Mellors Rotary Valve



					www.douglas-self.com
				




I found a custaway view of the little HP VT-21 Rc model engine.  I think that the Aspin valve is basically a vertical rotary valve whereas everyone else went with a horizontal rotary valve.


----------



## vederstein (Oct 3, 2020)

I've been working on my four stroke for some time and the main goal of this engine is that it be easy to make.  Think Webster but without the poppet valves.

Take a look at the video and let me know what you think.  I haven't made it to the ignition yet, and I'm very open to suggestions.

...Ved.


----------



## minh-thanh (Oct 4, 2020)

I think it would be interesting to build and see how it works - if the valve is airtight I think the engine will run
The exhaust valve problem on the  Webster engine
I know it's very difficult to make valves and valve seats airtight, but a lot of people have succeeded.
Just curious, can you describe the step by step how you lap a valve with valve seat ?
In a little bit of my experience, if I can't make the valve and the valve seat airtight,  I would make a new valve (or a new valve seat or both) , and start over


----------



## vederstein (Oct 4, 2020)

It's been so long since I gave up on the Webster, that I don't quite remember the exact steps.  I also tried a couple of different methods which all failed.  I remember trying spinning the valve and seat in a drill.  I remember trying to "coin" the seat with a press.  I remember trying to spin the valve and seat with my fingers.  Each try I made a new seat and valve.  It certainly was an exercise in frustration.

I suspect that my Webster had leaking valves, but I also cannot discount the face that I made the carburetor from the Webster plans and didn't just buy a carburetor that is known to work.

Speaking of carburetors, does anyone have any recommendations?  (Bore 7/8", stroke 7/8")

...Ved


----------



## earlwb (Oct 5, 2020)

Well I see some engines that they sell using  silicon rubber or viton O-ring piston rings. I think you can simply use small silicon O-rings on your slide valves. They call their rubber rings Fluorine Rubber rings. They actually make single cylinder, twin cylinder  and a V-4 cylinder one too. Anyway that might solve your sealing problem with the valves.
ref for example:  32cc Four-cylinder In-line Water-cooled Gasoline Engine for RC Car Ship


----------



## davidyat (Oct 25, 2020)

*Ved,
   OOHHH, I like it! Looks like you are experimenting with using what we learned from the Sun-Planet Engine? For now, until you perfect the design for this one, I think I'll tackle Brian Rupnow's simplified beam engine. I've thought about an IC engine, but the ones out there look like more than I'd like to chew on. Keep me posted on your progress.
Grasshopper*


----------



## vederstein (Oct 30, 2020)

davidyat said:


> OOHHH, I like it! Looks like you are experimenting with using what we learned from the Sun-Planet Engine?



Yup.  My experience with poppet valves is not good.  As I've written before, when I tried to make a Webster I had a hell of a time getting the valves to seal even after several attempts.  Eventually it went onto the shelf of shame then to an old gear-head co-worker to whom I gifted.

I know it's a crappy combustion chamber design.  Generally you'd want a hemispherical chamber or one that causes a "squish".  But I'm going for simple here.  I don't see why a piece of roundstock shuttling in a  reamed hole wouldn't have sufficient sealing.  The method works for stirling engines and they have near to no power density.  I guess I'll find out.

But if the idea doesn't work, making a new head and incorporating poppet valves shouldn't be too much of an issue.

I have the ignition on order.  When I receive it I'll measure it up and figure out how to incorporate it into the design.

...Ved


----------



## vederstein (Nov 29, 2020)

I've been quiet on this for some time, but I have been working on the engine:

The machined components are from the past few weeks and the castings I poured today.  (I'm quite happy with how the gears and the cams



 turned out.)

...Ved.


----------



## vederstein (Dec 4, 2020)

I machined the base casting and assembled the bottom end (minus the piston).

Overall, not bad, but I will need to rethink the connecting rod.  My earlier connecting rod design from my Sun-Planet engine (Contessa) worked quite well.  I may have to do something similar here.


----------



## vederstein (Dec 28, 2020)

Well, now I know spool valves don't work for an IC engine.  I got no compression.

I guess I need to redesign the head and try conventional poppet valves.

...Ved.


----------



## teeleevs (Dec 29, 2020)

Conventional valves are the way to go but you have to bore the valve guide and seat at the one setting.  Picture 1 is of a Hit n Miss engine I built about 10 years ago but I could never get it to run, even the miniature igniter worked,  2 the valves were made in two pieces, head was 10mm about 3/8" And stem 35mm long about 1.350" x 2mm dia 0.078" . Pic 3 a test setup I suspected valve leaks so my friend  Gil made up this plate and put the valves under 20 psi pressure and no leaks detected. We will have to re-bore the cylinder and remake piston and rings. 4 I had several attempts to make the rings, they were made from a MAN valve guide. 5 this Galloway was the closest I could find on the internet to an engine my father and I used on the Central Queensland Gem Fields in the 1960s it had no manufacturers markings on it whatever, I did find out that Galloways were made in Queensland under license,  6 the miniature made entirely from memory, no photos or drawings were available. 
Ted from down under


----------



## vederstein (Dec 29, 2020)

Thanks Teeleeves.

As I've written before, I had such a bad experience with my failed Webster that I went with this spool valve concept.  I tried several times to make the Webster valves with no luck sealing.  I knew the route I took on this design was risky, but it's more within my skill set.   I also designed the engine to redesign the head if my spool valves failed.

On contemplation, I have one possible way to recover.  I don't know if the leak is from the valve spool or the spool guide.  I'll disassemble and put some form-a-gasket to ensure a seal between the head and the valve guide.

I'm not expecting this to work, but it's worth a shot.

...Ved.


----------



## vederstein (Feb 7, 2021)

Thus far all my attempts have failed.

I've redesigned the engine for poppets and made the valves and vale guides twice.  My second try I get a bit less valve leakage, but no engine run.  Not even a single fire with ether as a fuel.  (Yes I have spark).  I have no compression.

I can turn the engine with a drill, put my finger over the inlet or exhaust port and hear air getting sucked in from the other port.  I disassembled the bottom end and manually ran the piston up into the cylinder.  I can hear the air leak out of the valves.

I've tried valves from 303 stainless and 12L14 leaded steel.  My valve seats are 360 brass.  Should I be using some other materials?  Is there a way to "coin" the valve seat to exactly match the valve?  At this point I don't care if the engine wears out after running for five minutes, I just want a running engine.  I've lapped the valves with a very fine grip lapping compound and can see a very good finish on the not-so-sealing surface.

I'm about to give up.  This project has lasted far longer than I expected.  It's cost far more than I expected.  I'm about just say screw it, redesign the cams, and turn this thing into a steam engine.  But I'll wait if anyone has any insights.

...Ved.


----------



## danallen (Feb 7, 2021)

I had a terrible time getting the valves to seal on my first internal combustion engine - a Farm Boy. What ended up working was mounting the valve guide in the lathe in a 4 jaw chuck. Put in a perfectly straight rod that just fits where the stem goes. Indicate it until it runs true in two places as far apart as possible and then cut the valve seat.


----------



## minh-thanh (Feb 7, 2021)

*vederstein !*
 Maybe i'm wrong, but when i see your plan picture, it seems the valve and valve guide are wrong.


----------



## Richard Hed (Feb 8, 2021)

vederstein said:


> Thus far all my attempts have failed.
> 
> I've redesigned the engine for poppets and made the valves and vale guides twice.  My second try I get a bit less valve leakage, but no engine run.  Not even a single fire with ether as a fuel.  (Yes I have spark).  I have no compression.
> 
> ...


I have to admit, I know nothing about this, but is it possible to putt some fine lapping material on the valve seat and put the valve in and grind with that?  It might work.


----------



## vederstein (Feb 8, 2021)

Richard Hed said:


> is it possible to putt some fine lapping material on the valve seat and put the valve in and grind with that?



Yeah, I did that.  I also took the head and with the valve(s) and valve guide(s).  Spring loaded them from the rear and turned them in the lathe to lap the valves.  That's how I got the very smooth finish on the actual mating surfaces.

(I think I just suck.)


----------



## ranger (Feb 9, 2021)

vederstein said:


> Thus far all my attempts have failed.
> 
> I've redesigned the engine for poppets and made the valves and vale guides twice.  My second try I get a bit less valve leakage, but no engine run.  Not even a single fire with ether as a fuel.  (Yes I have spark).  I have no compression.
> 
> ...


Hi,
A couple of things, how wide are the seats in the head? If they are quite wide,do you think they may seal better if they were narrower? ( less surface area means  spring strength gives more contact pressure). Do the valves have enough clearance in the guides? To allow them to float and seat fully without binding. Another thing to try is to machine the seat angle of the valve to a more acute angle (1/2 - 1 degree) than the seat in the head, then give the head of the valve a sharp “ tap “ to help seat it. When or if it starts and runs, the slight difference in angles should cause the valve to continue to “seat” itself into the head until the angles equal, by which time the seal would be as good as you could hope for.
One more thing to consider is the coarseness of the lapping compound. In these small sizes, unless you are using “ultra fine” compound, the usual “fine” grade is maybe too coarse and probably leaves tiny “tracks” for the limited amount of compression to escape!
You could try “Brasso”, or “Solvol Autosol” instead?
Doug.


----------



## Richard Hed (Feb 9, 2021)

ranger said:


> Hi,
> A couple of things, how wide are the seats in the head? If they are quite wide,do you think they may seal better if they were narrower? ( less surface area means  spring strength gives more contact pressure). Do the valves have enough clearance in the guides? To allow them to float and seat fully without binding. Another thing to try is to machine the seat angle of the valve to a more acute angle (1/2 - 1 degree) than the seat in the head, then give the head of the valve a sharp “ tap “ to help seat it. When or if it starts and runs, the slight difference in angles should cause the valve to continue to “seat” itself into the head until the angles equal, by which time the seal would be as good as you could hope for.
> One more thing to consider is the coarseness of the lapping compound. In these small sizes, unless you are using “ultra fine” compound, the usual “fine” grade is maybe too coarse and probably leaves tiny “tracks” for the limited amount of compression to escape!
> You could try “Brasso”, or “Solvo Autosol instead?
> Doug.


Very clever!


----------



## rutzen (Feb 10, 2021)

I had no compression on my Rumely engine I am making so I made a collet to fit the 3 jaw chuck.  Just a brass bush with a slit in it.  Mark the number 1 jaw position.  I took a very fine cut off the valve and used Solvol autosol to lap them in.  I now have compression!  Having said this I haven't got it running yet - still got the ignition system to make and some other jobs.


----------



## propclock (Feb 10, 2021)

3 very important steps to small engine poppet valves /seat.  Unless you have a perfectly!
true collet or chuck the valve is best machined in one chucking. 
The valve seat must be true to the valve stem. 
Sounds obvious , but not trivial in practice. 
Finally the valve seat width must be very narrow . 
At times you are forced to make 2 or 3 valve seat cutters . 
1 for the 45 degree  1 at say 30 degree ? and one at  85 degrees 
to get the seat width narrow.  Just like your car.  But very narrow ~ .010"
If you are lucky and your valve stem bore is perfect to your seat/cage bore
leave it sharp and all is well, otherwise , seat cutters are needed. 
This was a very difficult lesson for me to learn.  
I am sure it has been covered extensively elsewhere in the HMEM forum
but poppet valves work extremely well in small engines , but are difficult to make .
Just my 1.414 cents worth.


----------



## ninefinger (Feb 10, 2021)

Have you taken into consideration the volume that the intake and exhaust passages have before the spool valves? With your design you have a lot more volume in your combustion chamber/valve passages so you are going to have a relatively low compression ratio.  
Not sure if you can accommodate and increase the compression (taller piston?)


----------



## vederstein (Feb 14, 2021)

I give in.  This engine has defeated me.

I started with spool valves.
I redesigned to poppet valves.
I made the poppet valves and cages again.

Hell, I trying to get a single fire and I'm using ether (starting fluid) as a fuel.

No luck.

The plans for the engine (with 3D solid models) are here:






						T-Head Engine Plans
					

Ok,  For me, this engine was a failure.  I just couldn't get the valves to seal worth a damn.  I don't necessarily think it's in the design, I think it's because I suck.,  So in the following few posts, I present the design for this four stroke engine.  If anybody tackles this thing and is...




					www.homemodelenginemachinist.com
				




It's unfortunate, but sometimes one just needs to admit defeat.
*
Score Card:*
     IC Engine: 2
     Hobbiest: 0

*...Ved.*


----------



## ranger (Feb 14, 2021)

Before giving up completely, how about another head, maybe from brass, so no separate valve guides/ seats etc. OHV layout with a more conventional combustion chamber. Use the existing valve operating gear, longer pushrods with a rocker from each side to reach the valves? This should reduce the combustion chamber volume and increase compression. Or perhaps an engine like the old Land Rover, with one side valve and one overhead valve per cylinder, or less parts, and use an automatic inlet valve?


----------



## vederstein (Apr 11, 2021)

Being that four stroke engines still seem to elude me, I made some new cams, replaced the poppet valves back to the original spool valves, and turned the machine into an air motor.

It'll get painted eventually, but I just couldn't put this on the Shelf of Shame.  I just have too much money invested in it.

Here's the video of it running on compressed air...


----------



## Tim Wescott (Apr 11, 2021)

Y'know, I'd suggest that you make a test setup that lets you test one valve -- maybe with your setup above -- and just experiment with making valves work.

Don't think of it as "money wasted failing to make an engine", but rather "money well spent learning how to make valves".  When you _can_ build working valves -- then tackle an engine.


----------

