Now, here's a brainstorm for you........

Making A "Modern" Lenoir Engine


The "Lenoiresque" Engine

If you've already read this part of the saga, you can go directly to the 2008 page of of the saga by clicking here

I was reading "Internal Fire" by Lyle Cummins and came across one of the seminal types of internal combustion engines from way back.  Etienne Lenoir came up with a gaseous fueled non-compression engine that predates Otto, et al.  His patent dates from about 1861 and engines of this design were used until around 1868.  About 500 Lenoir engines were produced during that time.  They suffered from low efficiency, high maintenance and low output but were among the very first internal combustion engines to be used in any significant number. 

His engine was two-stroke.  In other words, there was a power impulse on a part of every down-stroke of the piston.

The engine was setup more like an air compressor than anything else.  The Lenoir engine has very little head space because it doesn't have compression.  Because of that, it doesn't have a compression ratio.  If you spin one of them over, it will have very little resistance unless you restrict the exhaust, then it will compress air.

Here's more or less how it works:

1: With the piston at TDC and on the way down the cylinder, the intake valve opens and a flammable gas/air mixture is drawn into the cylinder. 

2: At some time well before BDC, the spark plug fires, closing the intake valve and pushing the piston the rest of the way down the cylinder.

3: At a little before BDC, the exhaust valve opens and the piston pushes the burnt gases out.  The exhaust valve closes at TDC and the process repeats.

Lenoir was ahead of his time in one respect.  He used high tension ignition with a spark plug.  There was a difference between his version of high tension ignition and what we're used to seeing.  His buzz coil ran all the time and the high voltage output was switched to the spark plug at the right time.  Hard on batteries but it worked.


Enter the Geek.  I decided to take a small air cooled engine and make it into a "Kind-of Lenoir" engine, using some ideas I've come up with.

In my version, I'll use an automatic intake valve and a cam operated exhaust valve.  This necessitates removing all the original valve gear and making a cam that runs on the crankshaft.  I'm also considering using propane as a fuel.

I propose to control the power(??) output of my engine by adjusting the spark timing.  If it fires right after TDC, when only a small charge has been acquired, the power will be low.  As I retard the timing, the piston can suck more charge before the plug fires, giving more power.  I know that there will be a point where the charge will be large but there will be but a small portion of power stroke remaining before the exhaust valve opens so I figure that, as the spark is retarded, a nearly silent exhaust note will change into a louder and louder report as more charge is blown out of the exhaust valve.

Frank gave me a Tecumseh one-lunger that had been retired and was deemed past it's useful life.  I got a box of parts.  When I cleaned it up, I found that the engine was actually in pretty good shape and that the only real problem was that the ignition was shot.  No matter, I wasn't gonna use it anyway.

24 February 2006:


First things first.  Because the Lenoir needs to have as little head space as possible, I had to make a new head.  If there had been enough space between the valve pockets and the bore or the deck had not had pockets for the valves, I could have just sealed it off with a gasket.  Not so with this particular engine.  I have to block off the original valve ports.  I took a couple of carriage bolts and a couple of washers and ground them to fit into the tapers of the valve seats as shown.  The "plugs" are held down by nuts and lockwashers at the bottoms of the original valve guides.


Then, I filled the space between the valves and the deck with Devcon.  While this was hardening, I painted the block.  Might as well be pretty.  After the epoxy hardened completely, I used a large file and finished the top surface to the deck surface.  The new head gasket will seal this area off.

I had some pieces of 1/2" thick cast aluminum plate laying around to use for fabricating the new cylinder head (the old head goes back into the junk box).  It's roughed-out here.  Note the two "extra" holes that were in the original plate.  I'll grind and file it to shape.



Oh, yes, I'm going to try to do as much of this project without the use of a lathe or mill.  All I've got here is a small drill press with a 1/4" chuck, a bench grinder and hand drills, etc.  It's gonna take some ingenuity but I think it can be done............I also intend to do this without drawings, if possible.


25 February 2006:

A little progress today:  


       I got the epoxy filed flat with the deck.                                     And got a head gasket made.

I'm gonna use the two valves in the foreground and, maybe some of the pipe fittings outta the junk box to make the cages.  I'll let the possibilities bubble in my brain box for a while 'til some good ideas float to the top.  I've got some compression springs in another junk box.  I may cut down a Briggs spring for the exhaust and make a low force one for the "automatic" intake.


12 March 2006:

Well, for the last few days, I've been thinkin' on the valves.  What I decided was to go to the local hardware store and get some 1/4" pipe fittings.  Today, I did some "whittling".


I decided to use a close nipple, a cast iron cap, a cast iron plug and a steel coupling for each valve cage.


Here's my "milling machine", a small drill press.

After I marked off the locations of the bores to fit the couplings and the modified caps, I used trial and error to set the depth then used a rotary file and some time and patience to "machine" them.


Here is the intake cage set into the head.  On the other side is bore for the modified cap (done with a bench grinder).


Now, I apply good ole JB Weld to all the surfaces and assemble the cages and caps into the head.


With the cages in place, here is what the combustion chamber side of the head looks like.  Using the trusty hacksaw, I now cut off the caps near flush with the mating surface of the head.


Using a nice flat file and some elbow grease, the valve seats are "milled" flat.  I set the head in a drill press vise and made sure it was in the same plane as the drill press table.  After finding the centers of the cages, I bolted the vise down solid to the table.  The guides were drilled undersize then drilled to 1/4", the diameter of the valve stems.


Here's what the head looks like with the valves in place after a lot of work with the Dremel, a valve seat tool and a lot of lapping.  The valves ended up being too thick (remember that the head space is supposed to be as small as possible) so I used the bench grinder to thin the heads and make the O.D. smaller.

For the "manifolds", I drilled the cages and tapped them to 1/8 NPT.  The intake is kept at 1/8" NPT.   For the exhaust, I tapped the I.D. of a piece of 1/4 NPT pipe to 1/8" NPT and threaded a close nipple into it.  To help the breathing, I drilled out the 1/8 NPT pipe and nipple to 3/8".

With the manifolds screwed into the cages as tight as I dared, I used the Dremel tool to trim the inside of the cages for smoother flow.


13 March 2006:

Today, I'm fiddling with valve springs and keepers.  These parts may have to be fiddled with when it comes time to see if this puppy will run.  More Dremel, reamer and file work.


The top keepers and the exhaust bottom washer are from the Tecumseh, the bottom washer for the intake valve spring is made out of a flat washer.  The intake spring is out of the junk box.  The exhaust spring is out of a Briggs that bit the dust (I stretched it a little).

I guess I'll make the rocker arm next, then the exhaust cam.  After that, I'll have to figure out the ignition and the mixer.


16 March 2006:

The other day I went out and bought one of those six dollar spark plug thread chaser gizmos.  (I shoulda gone ahead and spent the bucks for a real-live tap!)  The guy in the parts house said that it would also cut threads.  Technically, he was right, but the darned thing wanted to go sideways and the only way I could save the thread was to just let it go on it's merry way.  Now, I've got an inclined spark plug but it should work fine.

Since the head space is very close, I modified the spark plug out of the dead Briggs so it was almost flat in the chamber.  Also found out that my 0.031" thick head gasket allowed the piston to just kiss the valves at TDC.  Made another gasket out of 0.062 material and now they clear.

Here it is with the head in place.  No leaks!  Talk about compression!  If this was set up as a regular 4-cycle, I think it would have too much compression even for Diesel!  

I've got the shaft collars on the crankshaft in preparation for laying out the cam(s).  I'll explain that later.


17 March 2006:

Did some more "whittling" today.  This time it was the cam(s).  The reason I use the plural for one cam is that I want to be able to adjust the cam timing and the open and close angles.  The way I'm going to do this is to make two cams, one attached to each shaft collar.  The opening (high area) for each cam is 135 degrees.  The little ball bearing shown at the end of the crankshaft in the previous photo is going to be used for the cam follower and will ride on both of the cams.  By adjusting one or both of the cams, I can adjust the opening and closing angles and can also adjust the duration from 135 degrees to 270 degrees.  The lift is 0.250".

Theoretically, the exhaust valve should only be open for 180 degrees, from BDC to TDC, but if the charge cools enough before the piston gets to BDC, I could extend the closing a little to take advantage of the vacuum (if any).

Anyway, here we go with the cam(s).


The left picture shows the rough rough cam plates mounted to the shaft collars.

Now, here I'll confess to breaking my "no drawings" rule for this project.  I used my AutoCad program to make a drawing of the cams.  In working with some model engines, I've found that a cam profile can be freehand filed (and cut-and-tried) to work reasonably well but it's not fun to do.  The CAD drawing is printed exact size so I glued one of the drawings to a blank then used my trusty band saw to rough-out the shape.

The right hand photo shows my drill press "milling machine" shaping one of the cams with a rotary file.


Now, after the "milling" operation, on the left, I'm using a smooth cut file to finalize the shape.

On the right, I've mounted the other blank and the finished cam on the crankshaft and am scribing the outline of the first cam to the blank.  More sawing and "milling" and filing and then I mounted both of the cams on the crankshaft and finish filed them so they were identical - or, as identical as a file will get 'em.  After all, this ain't no NASCAR engine!

Here is the completed cam(s) ready to go.  The aluminum piece bolted to the engine will hold a junkbox shaft and bushing assembly which I will slot to hold the cam follower ball bearing.  At this time, I'm thinking I'll keep the pushrod from turning and hook it solidly to the lifter to keep the follower aligned with the cam(s).


18 March 2006:

This part of the project took longer than I thought it would.  First, I had to take the aluminum part in the picture above and "mill" a slot in it to fit the tube with bushings I had in the junk box.  See below.


I then cut a "lid" for the slot so I could sandwich the tube with the bushings in it between the two pieces.


Above are a couple of pics of the completed cam(s) and follower.  The follower roller is a small ball bearing out of a dead hard drive.  I slotted the follower shaft and used a 10-32 machine screw as a shaft for the bearing.  I also drilled the top end of the follower shaft and tapped it to 1/4-20 for the pushrod.

I may have to re-think the pushrod.  Right now, there's no way for the rod to move sideways as the angle of the rocker changes.  To keep the follower aligned with the cam(s), I may make a slider to go on the shaft that runs against one of the clamp pieces for the bushing tube.  That way, I can use balls and sockets on the pushrod.  I'll think on it some.


19 March 2006:

Last night I thought about how to arrange the cam follower alignment.  What I came up with was a two-piece pushrod with a guide for the lower part.  The top half will be a short pushrod with a ball and socket arrangement. 


In the left photo, you can see the lower pushrod and guide in position.  It took a mess of whittling to make the guide block and shaft.  I use a piece of cloth phenolic between the "cap" and the guide.  There's a drill point to make a sort of ball joint in the top of the guide.  The bottom of the guide and the follower shaft are threaded 1/4-20 and jammed together to keep them in position.


Here's another shot of the guide.  On the right is the whole sheebang along with the unfinished rocker stand and arm.


20 March 2006:

It's gettin' there!  I have the valve train finished although I may have to do some filing on the cam(s) to get the valve timing to work out.  As you recall, the exhaust valve closes at TDC and, with the very small head space, the piston has a tendency to contact the valve when approaching TDC. The closest I can set the valve closing is about 350 degrees or 10 degrees before TDC.  This should work all right but  I may want to make the valve close faster so I can get it timed to really close to TDC. 


You can see the short pushrod above the guide block.  This pushrod fits into sockets in both the guide block and the rocker adjustment bolt.  The sockets are just 1/4" drill points.   The angle on the "ball" ends of the top pushrod were made on the drill press with a file.  Valve lash is adjusted at the 1/4-20 bolt on the pushrod end of the rocker arm.

I found a piece of brass tubing in the junk box and used it to make a bushing for the rocker arm.  I then laid the rocker arm on the drill press table and reamed it to 19/64" to get it straight.  I had a 5/16" cap screw that I worked over with a file in the drill press to fit the bushing.   I capped off the rocker arm by making an oil hole.

I didn't like the screws on the cap for the guide block so I made up a couple of 8-32 studs and use nylon insert nuts.  I can now tweak it to exactly where I want it to be and it will stay there.

Before quitting for the day, I filled it with 15W40 and spun it with a drill motor.  Ayup!  It shore makes a fine 'n dandy compressor or vacuum pump!

Again, I broke my "no drawings" rule.  I used AutoCad to make up a degree strip which I have glued to the flywheel.  It came out about 4 degrees off but,  since I don't need to know angles past about 190 degrees, I simply cut out about a 30 degree portion of the strip.  Close enough for guvmint work.

Next, I'll tackle the ignition.  This shouldn't be too hard to do as I think I'll use one of the magneto magnets inside the flywheel to trigger a Hall-Effect transistor that I'll mount on an arm that can be swung between about TDC and BDC for adjusting the spark timing.  With my electronic ignition borrowed from my Hoyt-Clagwell, I should have no problem lighting the fire.


22 March 2006:

After thinkin' on it some, here's what I'm doing about the ignition.


The first thing I did was to look into my box of unsold solid-state ignition system parts (I KNEW I'd use 'em for somethin').  In the left picture above, I have made up a Hall Effect transistor magnetic sensor to use with my Hoyt-Clagwell ignition module.

The picture on the right, above, I've whittled out a mount and concentric ring which bolts where the magneto came off.


I made the ring out of a big washer.  I had some flanges from old 2" video tape reels from my broadcast days so I filed the washer 'til it was the same thickness as the the reel flange aluminum then used some brass washers to hold it in place and give it some drag.  It now rotates concentric with the crankshaft.  I'll mount the Hall Effect transistor to the aluminum block that's attached to the handle and, viola!  I have adjustable timing.



Here is the whole sheebang (minus the transistor)


24 March 2006:

Today, I finished up the ignition (mounted the sensor on the arm) and made a crude mixer.  My mixer is made of some 1/8" pipe fittings  and other junk.  I'm using the regulator from a long-dead gas grill and the valve in the gas line is a needle valve which gives me me some adjustment room.

The first try at running the engine wasn't a big success unless you consider noise to be success.  I used a drill motor on the flywheel nut to spin it.  After a few minutes of fiddling with the fuel needle and the timing, it popped some and and tried to run.  When it did hit, it would jerk the drill forward but there isn't enough inerta in the Tecumseh wheel to allow it to carry over a few times.   I think I need to investigate a bigger flywheel.  My thoughts run to finding an industrial junk yard that has a collection of cast iron pullies.  A double vee belt pulley about 10-12" in diameter for a one inch shaft should work fine and will bolt righrt up.

I'll also probably try making a demand regulator for the propane and, if I don't get any joy from gas, I can always make a liquid fuel mixer.  Frank suggests trying Mapp gas instead of propane - more energy.

Here's how the outfit looks as of today.


14 April 2006:

The engine is now in KY and at Frank's shop.  We decided that the engine need to have a larger flywheel so Frank rooted in his junk and found the front crankshaft damper from a Jimmie 6-71 engine we'd disassembled for study.  (By the way, the upended block is now used to store raw materials, the crankshaft is a mailbox post and most of the rest of it is a yard sculpture - NOTHING goes to waste!) .

Frank rooted through another pile and found some flanges that he whittled on the lathe to fit inside the damper and we now have a nice heavy flywheel.

Today, I went over to Frank's for a couple of hours.  I hooked up my "first try" propane mixer and gave it a spin.  Pretty quick, we could see that the flywheel was what it needed to run at all.  After fiddling with mixture, intake spring tension and spark timing, it ran on it's own.

After some more fiddling, it was starting and running okay at a couple of hundred RPM, although it very seldom "hit" twice in succession.  During the session, we found that intake valve spring tension has a lot to do with how the engine runs.  It seems to run best with the spring a little too weak.  Get it too weak and it is a real celebration as it runs because the valve doesn't close fast enough to keep the flame from igniting the fuel in the manifold.  It sounds like a .22 going off in the shop.  The actual exhaust is pretty quiet as I expected it to be, it's the intake explosions that are making the most noise.

We're thinking of maybe changing to a reed valve or some other fuel induction method.  We're also doing some noggin scratchin' about the fuel system.  It needs to have some kind of demand regulator to run right.  We've got several ideas and will settle on one soon.  

My first thought is to eliminate all fuel in the intake manifold and work-up a direct injection scheme, drawing air only through the intake valve.  I don't want to lose the timing change feature to change power output yet so the injection has to be timed to shut off right before ignition.  This could be done by using a solenoid to open the fuel valve in the injector with a switch hooked to the exhaust rocker and placing another sensor on the ignition sensor arm just ahead of the ignition sensor to close the fuel valve.  This way, there's no flammable mixture in the manifold to explode if the inlet valve is a little slow to close.

I also found that my ignition timing scheme needs to be changed.  The engine ran best with the timing set as far past TDC as I could get it.  Remember that "advancing" ignition timing will reduce the intake cycle and reduce power output and "retarding" ignition timing will increase intake and power to a point.  Right now, it's firing at about 65 degrees into the downstroke and I think I need to change the arrangement so the timing can be retarded to past 90 degrees.  Of course, get it too far retarded will get us poor fuel economy and loud exhaust because of the burning mixture still expanding when the exhaust valve opens.


25 April 2006:

Frank and I had some time today so we fiddled with the fuel system.  Our theory du-jour as to why the engine 4-cycles a lot is that small changes in speed would make my original system lean-out as speed and fuel demand increased.  When the mixture leans-out, the engine quits firing and slows down 'til the fuel catches up.  I think this is more of a problem with propane than it would be with naptha or gasoline because, according to a chart Frank downloaded, the flammable fuel/air ratio range for propane is much narrower than that of some other fuels.   The narrower the range, the tougher it is to get a good burnable mixture.

Remember that we aren't going for a stoichometric ratio as needed for compression engines.  Any ratio that will burn will fire in the engine.

On the same subject, the absolute best gas for fuel/air ratio range is acetylene, and the engine would probably run better on it but we don't think we want to have a really uplifting experience if things get outta hand like happened during our experiments of the day.  Another good gas would be hydrogen which is much better than propane but we don't have a handy supply of it around so it looks like propane is it.

Of course, if I get disgusted with propane and the smell of the unburned gas, I may just make a naptha mixer with a check valve pickup.  I bet that'd work fine.


The picture on the left shows the whole lash-up, including the scientific duct tape holding the ignition module.  We located the engine, facing into the grinder housing (grinder removed) so we could use the exhaust fan to keep from stinking up the shop.  As things turned out, this ended up being a very good idea.  

Taking an air pressure regulator and changing springs turned it into a demand regulator.  It is located downstream from the grill regulator on the tank.  This part of the fuel system is shown in the picture above.   On the outlet of the demand regulator, we added a needle valve.  Teed into this is another needle valve to control the amount of air admitted and make a little suction so the demand regulator would work.  The thingy that looks like a muffler is a silencer from an air motor that Frank filled with a piece of a metal scouring pad.  This was added to quiet the little explosions that were set off when the intake valve didn't close fast enough.

With a little fiddling, we got this setup to work.  It did work better than the original non-demand system but the engine still ran sloppy.  I tried loading it a little and it ran a little smoother but had a tendency to quit when it slowed down.

Frank got the idea that we could do better without the pre-regulator, hooking the demand regulator direct to the tank.  We did this, then after getting the engine to run a little, it refused to start.  After about a half hour of getting the occasional hit, I discovered that the propane cylinder was empty........DOH!  We robbed Frank's grill of its' cylinder and hooked it up.  Then, the fuel adjustment was so touchy, it was hard to get the engine to hit at all.

After fiddling with it for a while, we smelled propane and looked down at the tank.  The demand regulator was frozen and the clear gas line to the engine was full of liquid!  Obviously, this will not work so it's back to the set-up in the picture.  The exhaust fan idea was good to get the propane vented outside.  We ran out of time and had to quit for this session.

During our sessions when we had the engine running, it became clear that the intake valve spring strength was very sensitive so in the meantime, Frank's going to pull the head and modify the intake valve by cutting some of the stem off.  Then he'll drill a hole through the valve stem and use a "hairpin" shaped music wire spring. 

I'm still trying to get my head around the fuel induction part of the non-compression Lenoir principle.  Fuel demand isn't like it is for an Otto cycle engine so I'm having to think different than I have all these years of fooling with compression engines.  Something I want to try is to move the fuel needle valve to the inlet side of the demand regulator.  This ought to make the fuel delivery more demand oriented but I still think I'm missing something.  I'm sure it'll come to me............another "DOH!" moment, I'm sure.

We may be able to get back to "fiddling" in a couple of days so stay tuned.


27 April 2006:

Okay - today, we made some more progress.  I moved the needle valve to the inlet side of the demand regulator and after fooling with the air inlet, I found that enough restriction to operate the regulator could be had by just using a brass 1/8" close nipple, a length of rubber hose and the inlet silencer.

Above is the latest lash-up.  Frank dug out a variable speed permanent magnet motor drive from his "archives".  To keep from grinding my fingertips all the way down to the quick while cranking, we used an available tooth belt pulley and belted the motor to the flywheel.  This saves a lot of energy!

To add to the setup, I wired a Model "A" Ford ammeter in series with the motor and a light socket across it to make a light load (get it?!?!?!) for the engine.

I spent a couple of hours adjusting this and that and, at the end of the day, the engine would make enough power at about 200 RPM to spin the motor as a generator and light the 120 Volt, 100 Watt lamp dimly.  If I screwed one of the 32 Volt, 100 Watt lamps in, the engine would quickly fall on it's face and stop.  A wild guess is that the engine at this point is producing a grand total of about 1/10th of a horsepower.

Frank's going to make a new and lighter weight intake valve, his theory being that the Briggs valve is too heavy to be able to open and close fast enough.  He's also going to make a hairpin spring for it.  I've got my doubts that it'll make a noticeable improvement but he'll probably prove me wrong.

After we test the new valve on propane, I'm gonna make a mixer for naptha and try that as a fuel.  Since naptha has a much wider flammability range, it ought to be a lot less touchy to get the engine fuel/air ratio adjusted.  I'm getting really tired of smelling propane every time the engine misfires.  Naptha smells much nicer!

Maybe next week I can get back to it.


5 May 2006:

A couple of days ago, I made a naptha mixer for the Lenoiresque engine but didn't have enough time to get it to do any more than try to run.  Then, yesterday I made a little adjustment of the height of the jet then broke the inlet barb and check valve so spent a couple of hours making another one.


The left photo above shows an exploded view of the naptha mixer.  There's really no rocket science to making one of these beasties.  There need not really be any actual venturi action, just enough inlet choke to draw the fuel from the tank and through the jet.

The needle valve is out of some long deceased and forgotten engine.  The needle and jet body is some kind of pheumatic fitting out of the junque box and the fuel inlet barb (and check valve) is out of the same box.  To give you an idea of the sizes here, the body of the mixer is an 1/8" NPT tee fitting.  The thread on the barb/check valve is 10-32.  The close nipple on the air inlet gives about enough restriction to draw fuel.  The only made from scratch part is the jet itself (right hand end of the left photo).

The center photo shows the check ball inside the barb.  I've used a punch to pein over the end so the ball cannot be sucked into the mixer itself.

After using up valuable time remaking the check valve, I had little time to fiddle with getting the engine running.  About the time I got it to run on it's own, I had to quit.  I did have enough time to fine-tune my ideas some more about further improvements.  The intake valve definitely needs to be lightened so as to work faster and keep the blow back under control.  Frank's going to try to get to it this weekend.

Although there are very few fuel explosions (different from intake tube blowback where the fuel is not ignited) in the intake tube with naptha as compared to propane, I think the blowback is messing up fuel mixture.  When a blowback occurs, I can see a small amount of vaporized fuel issuing from the air intake nipple and I think it takes a couple of strokes to get the mixture back to "normal" after one of these so the engine misfires a lot.  Every good, solid power pulse (with blowback) is followed by the misfires.

If lightening the valve doesn't make a marked improvement in the blowback, I may have to resort to going into the ignition module circuitry and getting an output from the box as the magnet approaches the Hall sensor (in this application, spark occurs as the magnet leaves the sensor).  I can take this "pre-ignition signal, amplify it and cause it to pull-in a solenoid that's attached to the intake valve.  This will make sure the intake valve is closed before ignition occurs. 

The only other thing I can think of to make it run better (after speeding intake valve action) is to emulate a buzz coil.  On Otto cycle engines, I've found that only one spark need be present to fire the charge if the engine's in reasonably good condition.  Maybe, in the Lenoir cycle, the lack of compression keeps the fuel/air mixture from being homogenious (sp??) enough to fire reliably at the first spark. 

Anyhoo - that's it for now...........Gotta go out and do something useful!


13 July 2006:

Okay, it's been a while but I finally got back to the project to try some things out.  As you can see, I'm now using another ignition system that requires an automobile coil.  Not too neat but it gets the job done.

I haven't tried the buzzcoil idea yet but have added a solenoid to the intake valve in order to make it close faster.  The solenoid is actuated by the leading edge  of the Hall Effect transistor (as the magnet approaches the sensor) that senses the timing magnet.  Spark occurs on the falling edge or after the magnet has passed the sensor.  This should give enough time for the valve to be pulled shut before the plug fires.


After spending a few hours fiddling with the setup, I got the engine to run a little better but it still doesn't fire evenly or make any useable power.  Part of the fiddling was to make a venturi of sorts for the mixer (helped a little) and make a better check valve because the previous one would stick closed occasionally (also helped some).

Now, I think I need to use a stronger spring on the intake valve and a larger solenoid to push the valve open.


15 July 2006:

Today, I made a stronger intake valve spring and changed to a larger solenoid to push the intake valve open.  I added a contact that un-grounds when the exhaust rocker moves to the valve closed position.  That signal triggers a circuit that turns on the transistor you can see attached to the coil.  When the ignition sensor approaches the magnet, the circuit turns off the valve solenoid.  

The circuit works fine to control the solenoid but, so far, no good!  The engine won't hit often enough to run on it's own.  There are some more things I can change and fiddle with to see if an improvement can be made.  Presently, the 24 Volt solenoid is only being driven with 12 Volts.  Maybe if I make up a power supply to increase the voltage, it will open the valve faster and more positively.

Now, I'm wondering if the Lenoiresque can be made to run well at all.  I suppose I could make up another cam and pushrod to operate the intake valve off the crankshaft with fixed ignition timing but I'd have to guess at the intake timing.  Right now, it looks like ignition at about 45-50 degrees past TDC is optimum although it can be moved somewhat with no big change.

Otto and friends were right in that the Lenoir was only a pre-workable internal combustion engine.  If I can't get this one to work well enough to display, I think I'll change it into a regular Otto four cycle.  I KNOW I can get one like that to run well. 

I'll keep trying a little longer, though.


19 July 2006:

Well, I've decided that all the fancy valve mechanism with the digital circuit is a little too high-tech for Monsieur Lenoir.  I  made a 24 Volt power supply to drive the solenoid.  With this arrangement, the intake valve opens smartly just as the exhaust valve closes and closes just before ignition.  Nothing good to report!  I fiddled with everything - timing, mixer choke, fuel mixture, cranking speed - I mean everything!  It still only hits occasionally and once I got it to run on its own for a few seconds.  Also, because it's getting a full charge of fuel/air, when it hits, it hits HARD but won't fire consecutively.  You can see the setup below.  Too complicated!

I got really disgusted and finally, getting ready to shut it down for the day, pulled the plug from the 24 Volt solenoid power supply.  The doggone thing ran better with the intake valve being sucked open by vacuum.  Even with the strong spring!  

Now, I'm gonna go back to the automatic intake valve and fiddle with springs and stuff.  With that setup I can at least get it to run reliably enough to demonstrate the principle.


20 July 2006:

I think I've done about all I can do to get it to run well so today I took off all the fancy-schmancy valve gear and re-made the intake valve for automatic operation.    I can adjust the mixture so it -almost- doesn't miss a beat at a fixed load and speed.  The maximum speed it'll do now is somewhere around 500 RPM.  After having a brainstorm last night, I made a spring loaded choke a-la Fairbanks-Morse Z and it helps a lot to keep the engine running at a mild range of speeds.

You can see the choke, screwed into the end of the mixer.  It's made of some junk pipe fittings, a little drilling and a few choice words.  The spring tension on the choke washer is adjustable by turning the #4-40 screw in the end of the inlet plate.  Please excuse the dorky looking exhaust pipe.  I needed SOMETHING to hang the electric cooling fan onto so i just slipped the length of 1/2" pipe over the 1/4" exhaust pipe.  It now runs well enough to need the fan - Yippee!

You can also see in the above photo, the intake valve spring arrangement.  In the previous experiments, I'd "whittled" on the valve stem to a point where all I had was some #6-32 thread and not enough room for a compression spring to allow for the valve to open.  What I did here was to drill a #70 hole in a brass 6-32 nut and pass one end of the little tension spring through it.  I then bent the spring end so it would stay put.  The nut is tightened to the end of the thread on the valve stem so it won't unscrew and cause the engine to swallow the valve.  That would be more than a high "oops" rating, very nearly an "aw-shoot!".  The other end is hooked to the piece of copper wire that hangs off the rocker tower.  This arrangement works better than I thought it would.

After putting it back together, I fiddled with the needle valve, choke spring setting and timing until it ran pretty well.  I then let it run for an hour or so.  It smoked a lot out of the breather at first because it had been run numerous times without getting warm.  Also, when I had the engine apart for cleaning, I put the original rings back in.  I know, I know........They'll probably never re-seat but with this amount of non-compression, who cares.  Must have been a lot of condensate in there because it took nearly the whole hour for the smoke to go away.

The photo below shows it actually making a little power, driving the DC motor as a generator to light the floodlight.  Maybe a couple of tenths of a horsepower is being generated.

The DC variable speed drive motor isn't needed any longer for cranking.  It starts fairly easily by spinning the flywheel.  Since it has no compression, cranking is nothing more than turning the flywheel.  

I think I'll take the big flywheel off and give it a coat of paint.  While it's off, I'll file on the exhaust cam ramps to give slightly slower opening and closing times.  This ought to quiet the valve clatter a bit.   At this point, the loudest sound when it's going full tilt is the sound of the exhaust valve working.  Because the intake valve is "automatic" or "atmospheric" and it closes when the fuel charge is lit (changing the slight vacuum in the cylinder to a substantial pressure), it blows shut with a loud "snap", making that the second loudest sound.  The exhaust sound is only a slight "whoosh-whoosh" sound.

Now that I've got it running fairly well, I fiddled with the timing and find that it runs best when the plug fires at between 35 and 40 degrees past Top Dead Center.  I'm sure this changes with fuel quality and type.

I may take this one to some shows.  I'll bet I have the only Lenoiresque engine there.  'Ol Etienne would be proud to see it.


19 May 2007:

This is just a note to let you know that the project isn't dead.  In the past year, I've gotten some more ideas to try so I may dust it off in the future and do some updates.  One comment I received was that the intake was too small.  In thinking about it, I agree that it may need to be fixed.  I'll rework the head with a larger intake port then make a larger mixer and spring loaded suction choke.  I also may pack some heavy steel wool in the intake valve pocket to see if I can retard the flame that causes the occasional backfires and messes up the next few induction cycles, causing a lot of misfiring.  

First, though, I've got to get my shop set up at our new digs and catch up on some other stuff.


Go to the 2008 page of of the saga by clicking here

If you have any comments, please email me at:

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Oh, yes.  Frank coined the new name for the engine "Lenoiresque" on the 13th of April, 2006.  I like it so it shall forever be.

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