Any ideas on how to get my home built engine working?

[HowToLou]

Wow. I never thought I would find a forum like this. This seems a perfect fit for my project. I am building an engine from scratch, using only off-the-shelf parts from a hardware store, and without using any power tools beyond a drill, saw, and sander. I have gotten pretty far, but would like any suggestions on where to go from here. I am getting gas in, and getting spark, because it will do a few revolutions, but I can get it to 'run'. Here is a short video of what I have so far and a couple of demo runs. Thanks, in advance for any insights.

Link

By the way, I have a MS in ME, and a Phd in Hacking , but neither of these has gotten me through this project.

 

[moon161]

Exhaust port? If you just let it exhaust, you should be able to get it to run as compressed gas motor w/o the spark.

 

[MikeHalloran]

You need to get clear on what the cycle is, and to develop a timing diagram for the engine in crank degrees and in clock time, and work out the flows that are required to sustain continuous operation.

For one thing, you need a crank-triggered spark. It doesn't have to be a mechanical thing; an interrupter on the crank, plus an Arduino or an old laptop (and some nontrivial programming) could give you easy adjustability, arbitrary spark curves, and even adaptive timing. ... or just use an old car distributor.







Mike Halloran
Pembroke Pines, FL, USA

 

[HowToLou]

@moon161 - Thanks. I had hoped there would be enough exhaust slipping past the piston, but I think I will have to drill a 2-cycle-style port in the side of the cylinder, at the very end of the stroke. Seriously, you think I could get this going without a spark? How would the oxy-propane mix, ignite?

@MikeHalloran - I think you are right about the timing diagram. I worry that there may not be enough fuel flow, from the tanks, to sustain repetitive cycles. I do have a crank-triggered spark. One of the fuel control rods, also presses a switch that engages the grill igniter just past top-dead-center.

 

[hydroman247]

Link

 

[HowToLou]

@Hydroman247 - I see. Like a diesel engine. I don't think I have near the compression I need for spontaneous ignition. Maybe. My spark seems to work ok, though.

 

[BrianGar]

Id prefer to see far less movement of the piston/conrod within the cylinder. It looks to be flopping about in there like crazy and could be locking up when it changes from power stroke, to what would be exhaust stroke.

Heavier flywheel as mentioned would be good, maybe duct tape a strip(s) of lead around it for a test.

Brian,

 

[HowToLou]

@BrianGar - Thanks. I can add a 1-inch to 1/2-inch copper pipe reducer, just like on the cylinder head, to guide and stabilize the conrod. I will also drill a few extra holes in it to make sure it does not cause any back pressure as the piston is coming down.

 

[moon161]

No, I was thinking just an expansion motor.

http://www.animatedengines.com/co2.html

 

[HowToLou]

@moon161 - Oh. I am trying to make an internal combustion engine.

 

[BigClive]

I not sure you will ever get it to run with that type of inlet valve gear. When the engine fires the combustion pressure goes back through the pipework to the valves.
As well as needing an exhaust port a piston-timed inlet port in the cylinder would probably be better. I would study the timing diagram for a conventional two-stroke engine and try and do something similar.
You also need a valve of some kind to control the amount of mixture entering the cylinder. Even if you do get it to run it will overheat and seize probably within seconds with the oxy/propane mixture and lack of lubrication.
But - an interesting (if slightly eccentric) experiment.

 

[HowToLou]

@BigClive - The inlet valves are piston-timed. They are not right at the cylinder, but my thinking is that the explosion presses against inlet valves, no matter where they are in the system. If the valves are closed, the explosion has no choice, but to push the piston. I control the oxygen-propane mixture with the valve push rods. If you look closely, as I turn the flywheel, the oxygen opens before, and closes after, the propane valve. I will be changing these to cams. I have already thought of the heat problem, but have not implemented the remedy until I can get the engine running at all. I plan to wrap and solder 1/4" copper tubing around the cylinder and connect it to cool water pump. I may also have to add an oil drip for lubrication, but hopefully not.

@MikeHalloran - I have taken your timing diagram comment to heart. I am planning to abondon the valve push rods and build in a cam system that lets the gases in, beginning just after exhaust and ending just before top-dead-center ignition.

 

[moon161]

http://www.animatedengines.com/twostroke.html

 

[BrianGar]

Perhaps the valving used on basic oscillatory steam engines 'could' provide more ideas also.

Brian,

 

[HowToLou]

@moon161 - Yep! Been there. Here is my old vs new fuel timing diagram.

 

[dicer]

Great job using basic stuff. Exhaust port is for sure a problem. The timing of the mixture will be a problem using that sort of valving. Because with pressurized tanks you can't let any pressure in till the piston is at or past TC. And while all that is being done the piston is heading towards BC and likely down the hole a bit before the ignition lites it.
Becareful if you do get it running, as it could run wild and parts go flying at you.

 

[moon161]

Good point about the runaway. Be careful with the 02 as well, I'm a bit nervous about that from here. Especially if you lubricate the system in any way- 02 and oil will spontaneously combust above a certain partial pressure (hence the 'use no grease or oil' sticker on gas regulators). Probably a bit safer to suck in or blow in air as an oxidizer.

Have you thought about finding a steam or small engine club?

 

[HowToLou]

Thanks for all the comments. Please keep them coming. Here is what you, and youtube said:

Here is where I am now:
Video

 

[HowToLou]

Sorry, I forgot to include my thoughts. Also, see the video at the bottom of my last post.

Add Exhaust Port 25 A LOT of you pointed out that there was no exhaust port. I was hoping that enough would slip by the piston, but I think you are right. I will drill a hole in the cylinder at the very bottom of the power stroke.

Make Flywheel Bigger 13 Many of you noticed that the flywheel spun partially around and then stopped, when it was trying to open the valves. Very good idea, but I am going to try to solve the problem with new valves that are at least 10 times easier to turn. I think the current flywheel will be able to handle them. If not, I will try a bigger one.

Change Fuel Mixture 12 The valves were actually set on the first engine to have slightly more oxygen than propane, but several of you said it needs to be 10-1, and I will change it to that. Thanks.

Add more gasses 10 A few of you thought that there were not enough gasses being let into the cylinder, with each cycle. I am worried about this too. I am changing to a cam system that will hold the valves open for more of the cycle, but worry that the torch heads will not allow enough flow to support continous explosions.

Change Timing 5 Some noticed that the timing was not optimal. The spark should happen at top dead center and the fuel should be let in right after exhaust. I added a cam system to allow optimum timing.

Use air, not oxygen 3 Air is about 20% oxygen, and that is the only part of air that combustion uses. An oxygen tank was only $8. An air tank would have been $50, and I would have had to pump it up. There are those little spray air cans, but no way to hook pipe to them.

This is a 2-cycle engine 2 Yes, I thought this would be easier than a 4-cycle, to build

Replace grill igniter with… 2 A few are concerned that the grill igniter will not be able to spark fast enough. Hmm. It is pretty fast. I will leave it for now and fix other stuff first. I may have to change it later

Add Cooling 2 A couple people thought that when this engine does start running, it will heat up and leak badly or seize up. I have plans to add a 1/4" copper pipe water cooling system, but wanted to get it running at all, first

Stabilize Connecting Rod 1 Some of you noticed that the connecting rod was pretty loose in the cylinder. I will add a 1" to 1/2" copper pipe adapter to guide the 3/8" rod.

Add a kill switch 1 A few of you thought ahead to when this engine actually starts running and worry that I could not stop it, if it started going too fast and parts started flying off! Good point. I actually have one. I can turn the battery off to the spark.

Make Cylinder Stronger 1 One person is worried the cylinder could explode. So far, so good. I hope not !!
Publish Email 1 One person wanted my email address to send me a PDF of a CAD drawing. It is HowToLou@Gmail.com

Use Gasoline 1 One person suggested gasoline to replace the propane. I need pressurized gas, because I am forcing in fuel while the piston is compressing. Gasoline needs to be pulled in with an intake stroke, but I don't have that in this 2-cycle engine

Use Check Valves 1 On person suggested using check valves and I thought this was a great idea. In fact, my first prototype used check valves, but since the gasses kept coming in, the first explosion just lit the gases at the source and I had an internal torch that never went out.

Add piston rings 1 One person suggested piston rings. This is pretty tough with hardware store parts. I hope I don't need this!!

Help Wrap Gifts!! 1 Oops. That was my wife.

 

[BigClive]

It's a bit hard to tell - but in the new video aren't the intake valves closing far too late? - causing most of the mixture to be pushed back out of the cylinder?

If you just want an IC engine that runs maybe a cycle like the very early (pre-Otto) Lenoir gas engines may be better.