Introduction: How to Almost Build an Engine With Only Parts From the Hardware Store (Take 3)

This is my third attempt at an engine.  I have switched to a 4-cycle design, and have switched from propane to gasoline.  It still does not work, and I need your help.


Grikovien (author)2013-07-22

Try moving your intake to the other side of the cylinder so the process goes : intake - > cylinder/ingition - > exhaust. Try a manually adjustable valve for the exhaust. Your exhaust could be releasing too much pressure, keeping the cylinder from experiencing the force. You could also try pressurizing your fuel+air which could give you better concentrations of fuel+air and would assist in moving it into the intake. Be careful with this though.

HowToLou (author)Grikovien2013-07-28

Good ideas. I think you are right about moving the intake. I actually built a pressurized bubble carb, The first time I tried it, it caught on fire. If you look closely at the board, there is a dark spot behind the valves, from the smoke. You can see that build at, but I got too scared to use it any more. I tallied all 117 suggestions, so far, from hackaday, video comments, instructable comments, and emails. Here is what they said and my responses.

15% Check valves are too slow to close. Evidenced by the gasoline splashing back and fire coming out of the intake manifold. Try cam controlled valves –Lou: I plan to replace the exhaust valves with one cam-controlled gate valve.

15% The flywheel should be more massive. Maybe try a wheel and tire –Lou: I am probably being stubborn, but I have seen a good fire send the flywheel around through all the cycles. I think it will be fine. I plan to focus on getting fire every time, and then look at the flywheel.

15% The compression is too low. The valves should be moved closer to the cylinder to decrease space and increase compression. –Lou: I wrapped foil around the piston and got a nice increase in compression. I also plan to move the valves closer to the head, as suggested, to increase the compression ratio.

13% The spark timing is off. Get rid of the string and micro-switch set up. You need something a lot more stable. Try timing gun. –Lou: See next comment. I think the grill igniter is the main problem. If not, I will switch to a cam driven spark.

12% Grill igniters do not have reliable timing. When you push the button there’s a short, unpredictable delay until the first spark. –Lou: I totally agree. I just went out and bought a coil, points, and condenser, at an AUTO PARTS store, but don’t tell anyone.

12% You aren’t getting the right air/fuel ratio Your fuel isn’t atomizing properly with the bubble system, so there is an inconsistent fuel/air mixture with each cycle. –Lou: I was totally ready to give up on my bubble carb, but then someone posted this:

5% This looks dangerous. –Lou: We are not having fun until someone gets hurt  I will wear goggles, at least.

3% The stroke is way too long for the air to properly compress and combust. –Lou: Maybe. I will work on other stuff first and then look at this.

3% The spark may be too weak. –Lou: See comment above about replacing grill igniter.

2% Build a better starter motor. –Lou: Maybe. I hope I don’t have to.

1% a choke cuts the amount of air through the carburetor to enrich the mixture — your ‘choke’ just lets more air into the cylinder and less fuel, thus leaning it out. –Lou: my “choke” allows me to change the fuel/air mixture. I think that is all I need.

1% This can’t be done without precisely machined parts. –Lou: You are right, so far.

1% Hundred if not thousands of engines are operation with intake valve what is essentially a check valve & the valve timing with that is automatic. –Lou: I plan to stick with a check valve on the intake side, for now, at least.

1% Just buy an engine at the hardware store! –Lou: I wish had thought of that, a year ago, when I started this project!!

dasimpson1981 (author)2013-07-22

your timing is out

rimar2000 (author)2013-07-22

Anyway, you had done a great job.

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