Simple 4 cycle vertical model engine

David Kerzel, Pompano Beach, Florida david@FloridaAME.org

Simple 4 cycle vertical, 1.00 bore X 1.00 Stroke

The work in progress has gotten rather long, so it is now in 2 parts Go to the first part, building the engine

Making it Run!

The Hall sensor finally came Saturday. A mounting block and a interconnecting cable was all that was needed. I tested it on the bench before I put it on the engine and it worked fine. When I put it on the engine it worked crazy, two or 3 sparks per cycle at different magnet positions. After a lot of probing I found the batteries were bad.

Once the timing was all set and verified I added some fuel and gave it a spin. It was a lot of spinning. From time to time it would pop and some oil mist would come out of the exhaust. There was enough of this to the warm up the head. As I was watching all of this not doing much, I noticed some oil mist coming out of the carburetor before each pop. So my valves still leak and they will have to wait till next week.

9/17/2006

I made an adapter to inject compressed air into the cylinder. Air rushed out the intake valve. I started by lapping again but no change.

It turned out the leak was around the valve inserts. You can see a bigger gap at 4 to 5 o'clock on the right valve insert. A quick clean and a drop of gap filling LocTite and the leak should be gone. Back together and it was better. Turned out there were still facets on my cams and during the lapping I lost my valve clearance. I got to the point where I could hear no compressed air escaping.

I made a driver with a one way clutch to spin the motor with a drill. As I adjusted the carburetor I could get it to fire perfectly as long as the drill was on. The instant I stopped the drill the engine did not make it through the next cycle.

I tried a faster drill and got it to run for 2 or 3 seconds before it would stop.

I am convinced it is either a fly wheel being too small or a carburetor problem. So I will make a larger heavier flywheel and make a better carburetor.

The carburetor I have been using were several from past hit and miss engines. Some had coarse screw threads some have a choke. None were very fancy.

9/24/2006

These are the old carburetors I have been testing with.

This is the first of 2 new carburetors. It has a barrel throttle, a long needle with a long taper, it is soldered together. This carburetor has parts that fit better than any of the old ones.

I got the engine to run for over a minute several times, but I was not able to get it to restart. More carburetor Ideas are in the works.

The old and new flywheels. The old one could not carry the engine through one full cycle at 600RPM the new one is good for 3 or 4 cycles. I believe this one will allow starting with a flip when it all works.

9/26/2006

The new flywheel and the new carburetor

Dale Detrich recommended the OS airplane engine carburetor. It has a barrel throttle the same size as my new one. It has a idle bypass needle adjustment for idle air which is very nice. It also has a low speed throttle adjustment. when the needle was full in no fuel was pulled in. At about 5 turns out it flooded and stopped popping,

When the engine is flooded severely, the spark starts to jump on the out side of the insulator. If it can jump 1/2 inch when the tip is wet spark is not the problem.

It worked about the same as my carburetor but it got rid or any doubts I had.

Tonight I started by putting compressed air in the spark plug hole. No sound, no leak at the intake or exhaust. I do not have all of the crank case plate in place and when I grabbed it my fingers went inside and I felt a breeze. Lots of air was leaking past the piston.

I took it apart. The inside of the cylinder has a little burnishing but measures the same as new. The piston has a little burnish on the bottom skirt by the pins. The top ring was polished for about half its width fully along its circumference. The bottom ring looks untouched. The piston now falls through the cylinder with its own weight, before it needed a genteel push.

It does not take much force to compress the rings. They are .030 thick and have cross section of .043. I am wondering if they need to be thicker and springier.

10/1/2006 New Piston and new rings made from cast iron, lapped for an great fit. The new rings are .050 X .050 cross section and my fixture needed some minor changes. These are the first rings I have made that needed gapping to fit in the cylinder. They were made from the same lapped material that the piston was made from so the OD should have been perfect. The old rings were flexible. that new ones are stiff and very springy. After heat treating a few strokes on 400 grit silicon carbide paper the remove the oxide and a few strokes in the cylinder with 1000 grit lapping compound make them shine.

The new piston was lapped until it had a great fit in the cylinder. It is 0.0015 larger diameter than the first aluminum piston. I suspect that it would work with no rings.

I used the lap ring to compress the ring ( I decided to start with just one). Every thing move smoothly with a very consistent drag. I started putting the engine together but had all the screws loose. A few spins by hand and more by the drill and all was great. I was thinking I should have included the second ring. Then I tightened it all up and it froze. After a few cycles of taking it apart and putting it back together I realized tightening the 4 screws that clamp the 2 plates on the cylinder caused the piston bind in the cylinder. It was mentioned on the board to lap the cylinder after parts are pressed together but I figure I was not affected since my engine screwed together. It was too late for lapping the cylinder again with the screws in place. I an surprised 4 screws can distort the cylinder but maybe everything is that exact with the precise lapping I have.

10/2/2006 All day at work my mind was filled with thoughts of lapping cylinders and running engines.
It took about 30 seconds of lapping to get the piston to pass through the cylinder again.
I cleaned the parts, oiled then, cleaned them again, and assembled it all with both rings.
Back together, and a splash of fuel.
Instant Pops and several short runs.
The cordless drill I am using went into torque limit so I changed the setting due to the new better compression ratio loading it down.
When the engine would catch for a few cycles it started to jump off the bench, it needs to be clamped down. The exhaust was much louder and had a hint of black.
But it still does not run!
Tomorrow I will look for new leaks. Or just let it be for a few days.

10/8/2006 I found no new leaks but I noticed the engine ran best on the first catch each day. I wipe the engine down and oil it before I start, and oil on the cylinder seems to be the key. I decided to add a oil control ring, put the end plates on the crank case and add oil. I had enough gray iron from making the new piston and rings for 2 oil control rings. They sure looked good, but both snapped at holes as I tried to put them on the piston. I am out of iron.

I decide to test with oil. I made a lexan end so I could see what happens. I driller a crankcase vent hole but didn't make the negative pressure ventilation check valve yet. I used about 1/4 inch of 20-5W oil . When the engine runs the oil is thrown all around in the crank case the oil level drops to about 1/8. With oil the engine runs much better, It is easy to get about 2 minutes of running but 5 minutes is still elusive. A quick flip is all it takes to get it going, speed varies with speed bursts.

10/16/2006 This is a summary of what has happened during the last week.

Battery

The day before I tried to start the first time, about 4 weeks ago, I charged my NiMh batteries. They worked great for checking the wiring and setting the timing. By time I go to starting the engine two cells were gone. They were many years old so I replaced them with Duracell Alkaline D batteries. I had 6 volts in stead of 4.8 and new batteries, so there would be no ignition problems.

As the leaks were fixed and oil added the engine continued to operate better and better but it never has run as expected.

I was working around the engine during a short run and my arm hit the top of the spark plug and there was just a mild tingle. So I went looking and found the great new batteries drop to under 4 volts when the coil is on. Next I decided to look at it with an oscilloscope and the battery voltage drops to under 4 volts as soon as it is turned on. About a minute later, my typical run time, it is at 3.8 volts.

I did some research about batteries.

Alkaline D batteries are for loads of under 2 amps and have a short circuit current of 3 amps. This is not very exciting if your coil needs 4.5 amps.

Old fashion Carbon Zinc D batteries are for loads of under 4 amps and have a short circuit current of 8 amps. These would run my coil at full.

Rechargeable NiCd Nickel Cadmium D batteries are for loads of under 30 amps and have a short circuit current of 100 amps. These are almost a perfect battery.

Rechargeable NiMh Nickel Metal Hydride D batteries are also for loads of under 30 amps and have a short circuit current of 100 amps. These are also almost a perfect battery and a lot les toxic.

When I changed battery types I ended up loosing 3/4 of the power (heat) in my spark.

When I went looking for new batteries I found good old lead acid gel batteries are the most cost effective and they have high load currents like the other rechargables.

Switching to the new lead acid battery with the auto coil caused some increase in engine performance. The lead acid battery and Mikes coil performed about the same. This indicates to me that the battery was the issue not the coil.

The new battery has characteristics like the original battery and both the coils are working again,

Coils

I have been using one of Mike Neal’s Coils since the first day of testing of this engine, it worked great on my last engine.

Everyone has concerns about dwell times and angles. So I did the calculations and found mine is 57 degrees (1/8 magnet on a .5 diameter wheel). I made a spread sheet to do the calculations.

Next I needed to know the time constant for the coil I was using. The time constant is the time needed for the coil to store 63% of the remaining amount of current that can flow through the coil. Generally 3 time constants are enough to get to 95% of the maximum current. This is measured with an oscilloscope and then calculated:

For Mike Neal’s Coil 3 time constants is .006 seconds.

For an Areotronics Coil (looks like a Modelectric) 3 time constants is .004 seconds.

For my automotive coil 3 time constants is .011 seconds.

For my engine that indicates I can have full coil energy up about 9,000 RPM with Mikes coil and about 5,000 RPM with the auto coil. I have never had any luck with the Areotronics Coil, but it was putting out great sparks over 1/8 long.

Once the time constant is known the amount of energy the coil can store can be calculated and that energy directly relates to the heat in the spark:

For Mike Neal’s Coil the energy is 0.023 joules.

For an Areotronics Coil the energy is 0.013 joules.

For an automotive coil the energy is 0.030 joules.

It is logical, bigger coil more stored energy. So I switched to the Auto coil and it caused the biggest increase in engine performance to date.

Spark plug

I have been using a 1/4 inch spark plug that I got from Bob Shores.

In the past I have always made my own plug.

I am wondering if this little plug is getting fouled with fuel or oil. When the engine stops, it looses power over 5-10 cycles. Most times it does not restart on the first flip but the third is good.

So it would appear that most carburetor problems are ignition related as Bob Shores said many times.

I made a quick and dirty test spark plug. Jay Rich makes plugs using the plastic tube from a spray can as the insulator. I made a brass plug and glued a length of THHN wire (Nylon covered thermoplastic) through the center with super glue. It was not very good until I bent a single strand from the wire and bent it to arc to the threaded side of the plug. It worked as good as my little plug.

Oil

I changed the crankcase oil to red ATF to figure out where the oil at the exhaust and in the cylinder comes from. I was getting about 1 drop of oil per minute with camp fuel and WD40. I tried pure camp fuel and it took nearly 2 minutes for that amount of oil to form at the exhaust. In 2002 I made a demand propane regulator from plans Richard Remington gave me. With the carburetor needle ready to fall out, the engine ran but the oil was still forming at the exhaust. When I opened it up the oil on the top of the piston was red.

Last week I tried to add oil control rings but they snapped as I installed them. Dale Dietrich shared his ring making and installation techniques and I go them on this time. The piston has a lot more drag as it moves in the cylinder and I am concerned about it running.

Crank Case pressure

I made a check valve from a ball to have the crankcase pressure be negative during operation.

Last week I tried to add oil control rings but they snapped as I installed them. Dale Dietrich shared his ring making and installation techniques and I got them on this time. The piston has a lot more drag as it moves in the cylinder and I am concerned about it running.

Trying to start

As expected the engine does not run and does not coast for long. It pops every time and wants to run but there is so much drag. The battery on the starting drill gave up as I was starting to get 15 second runs, so maybe with a little more time it will just run.

I am using propane for fuel and it is nice because it does not make the shop smell.

Today, Monday, I got a run of over 3 minutes at 800-2000 RPM along with 2 other 2 minute runs tonight on propane. They were the best and smoothest runs I have ever had. It does not feel as tight as yesterday. The head is at 220F when it stops so I will try a computer fan tomorrow to see if it still goes longer. I will also change from ATF back to real oil.

10/23/2006 Once my battery issues were resolved and I had a good charger I got a lot of 15-20 minute runs. The runs always end when the engine temperature goes over 200F.

I put a 65mm computer fan on it Sunday morning and got a 30 minute run before the carburetor vibrated off.

The next run was stopped when the carbon monoxide detector went off after 55 minutes. I am still running propane and I assumed it burned clean because there is little smell in the closed shop. I need to figure out how to get around this. This is a serious concern and we all need to give it serious attention.

I moved outside and it was hot. The high voltage wire fell off the spark plug after about 30 minutes. I did not notice and gave it a spin and got a good jolt not like the tickle with the old batteries a few days back. It would not start, the hall sensor stopped working. I think I need to clean up my ignition system.

I think I need to say my engine now runs. It starts in half a second with the drill and in 3 or 4 manual flips.

I think the carburetor I am using is too small for full power propane operation and I never finished trying carburetors from a month ago.

10/28/2006 I made a test carburetor but have not yet tested it.

This carburetor has 2 main jets, one in the center of the barrel and a second one behind the barrel. Only one will be used at a time but I have wondered which is the best location. The hole in the top is a idle bypass port and is adjusted with a set screw. The 2 small cap screws on the top limit the rotation of the barrel. It has a o'ring in it so the barrel stays in position as the engine runs. The needles throttle fuel using the large OD in a bore rather than the point in a orifice which should allow more flow.

11/1/2006 The carburetor looks done but needs the needles fitted so I an still running the OS carburetor.

I installed a new hall sensor. it was a little out of position so the spark moved 6 degrees after TDC and it barely ran.

I moved the sensor to get the spark at TDC and the engine just took off. I was surprised that a few degrees made so much difference.

I was asked for a video of the engine running. It starts with a flip but speed never gets too high and changes as it runs

VIDEO 1 (Windows media file).

After the videos I let it just run, It stopped after 40 minutes. The new hall sensor failed. why is it failing? temperature is about 150F it uses the same power wire that is the spark ground.