my modest 2-stroke

[IgorW]

12mm bore, 12mm stroke, ci piston, steel liner with 3 intake passages, intake timing governed by a rotor plate. sorry for poor description but i'm using on-screen keybord... more to come. cheers from Poland!!!

 

[Niels Abildgaard]

Hello Igor
and thank You for posting something wildly out of the ordinary.
Why are there two holes in cylinder and please use a better camera.

 

[moerman]

Very nice Igor! What tools have you used. Lathe and mill? Or lathe only? Doesn't looks very modest to me!

 

[IgorW]

hmm, that was my first post soo.. Hello everyone! My name is Igor, I'm 28 (1988) and I come from Poland. Thank You for the kind words, it means a lot to me.

Ok, so i bought a wireless keybord as it was cheaper then repairing the existing one (laptop).



@Niels : Unfortunately i don't have a photo camera, only a mobile phone with a camera so the only thing i can promise is keeping the lens clean. My engine is loosely based on a popular engine but i can't recall the name at the moment. It even looks similar but that might be due to the maximum simplicity of the design. Do You mean two bores? That may be an illusion. In the picture there is cylinder head standing behind the cylinder liner. I will add more pictures and hopefully this will be self explanatory.

@moerman :
Both. My mill is Avia fnc25 - popular Polish mill, wery versatile, lots of add-ons available. Like tilting tables, high-speed spindles, shaper heads... My lathe is... I don't know. the only "name" i found is APETOR which did not yield any helpful results in google... It's probably the name of the manufacturer responsible for the electric harness. It's an old heavy lathe, 1 meter between centers. I saved it from the scrapyard. It's in a very poor condition.

. I'm in love with "combustion engines" since I can remember so my own engine was inevitable. I'm a metric person and I couldn't find metric plans that satisfied me so I had to make my own. I used SolidWorks software, almost every part is included. I can share if someone wants to have them but firts I want to make it run.

More about the engine:

It's an evolving project so things change along the process. The aluminium head was changed to a steel piece because the engine was first meant to be a compression ignition or diesel style and the cylinder liner was longer as it had to accomodate the contra-piston. Now with glow ignition i have less parts to make.

EDIT: There are two bronze bushings in the engine nose to hold the steel crankshaft. The connecting rod is made of steel but its a temporary replacement as it has no bearings at all. Maybe a full bronze piece will be made. The cylinder liner fits with a light press fit into the block. It has 3 inlet ports milled in the lower part with 2mm holes drilled into the cylinder. The piston is cast iron and it has a steel pin holding it to the conrod. The timing rotor is not developed yet.

Now with the glow ignition the cylinder liner was shortened on the top end. The compression ratio was "set" to 7.6:1. The steel cylinder head is press fit on the liner and it has no cooling fins. It's also made in a way that the compression ratio can be increased if necessary without any changes to the head. I chose steel because i had no alu stock. This engine is not meant to be pretty. It's meant to proove myself i could build a running engine. If it happens i take up the hobby more seriously.

 

[moerman]

OK, I found tha Avia mill. Not exactly a table top model but not an elephant either. It seems to be copied quite a lot according to the info on http://www.lathes.co.uk/avia/.

BTW: that webpage mentions: "If you have an FNC-25 the writer would be interested to hear from you". Maybe the writer of that site could help you to learn more about your APETOR lathe?

Photo's of the Avia FNC-25: http://www.maszyneria.pl/1838,2180,foto.html

 

[lohring]

What a great way to build a simple two stroke! Drawings might encourage some others on this forum to build one.

Lohring Miller

 

[IgorW]

No updates because I'm stuck on the glow plug thread. A hand or machine tap is almost impossible to buy in Poland or is very expensive and my lathe only does metric threads.... What to do?

 

[joco-nz]

Great looking start. Post drawings, we all love drawings and being from a metric generation i love metric drawings. :thumbup:

 

[Cogsy]

No updates because I'm stuck on the glow plug thread. A hand or machine tap is almost impossible to buy in Poland or is very expensive and my lathe only does metric threads.... What to do?

I had a quick look on eBay and grabbed the first listing I could see - looks like just over $4 AUD delivered from China to you. You'll have to wait a bit for it though. Here's the link - http://www.ebay.com.au/itm/1-4-32-U...648817?hash=item45fd6eed71:g:BtsAAOSwEeFVB-ao . I know it's only a cheap Chinese tap but should be good enough to cut a thread or two if you're careful. Otherwise it looks like about $30 for a good one out of the US but that is getting expensive, although if you plan on making a few glow engines then a quality tap would be a good investment. Good luck - I'm keen to see your engine run.

 

[IgorW]

Well I'm back with some good news. It pops! I was so excited i took only two pictures Yesterday i was cleaning up my shop and i stumbled upon this little engine which i kinda forgot about. It was a quick decision - no more cleaning, let's finish building the engine I couldn't find the rotary valve plate so i changed it to reed valve. The valve flap is made of high carbon steel, heat treated, 0.2 mm thickness. Its a bit too stiff but it seals nice and that was what i had laying around. Took my 'carb jar' from a shelf and found a nice little OS carb from a rc car. Drilled and reamed the back plate to accept a small 12 mm OD and 10mm ID intake and coupled both with some loctite. The carb is 9.95mm and has two orings so a light press fit should suffice. Left it overnight to cure. Today I woke up early and I think that was the fastest trip from home to the shop in my life I have quickly organised a test bench - clamped the engine in the big vise on my mill ,fuel lines ,glow plug cables etc. Magnetic dial indicator base made a huge deal with holding the temporary fuel tank made of a small plastic syringe as its easily adjustable - you can kinda adjust fuel pressure by changing the height of the fuel tank. With a glove on my right hand and holding the throttle with the other i started cranking... 3 hours later after changing 3 different power sources for the glow plug, fiddling with the carb, putting an oring to serve as a head gasket it started to pop. Ooooh what a joy! Well its not fully running but this is something! I managed to make it run for less then a second, maybe 20-30 pops in a row. Its overfueling a lot and i adjusted the carb to the lowest settings available and its still spurting fuel like crazy. Couldn't stay any longer. Thats it for now. Cheers

 

[IgorW]

Ok here is a quick video. Sorry for poor quality. I got it to run for 10 seconds and it dies. I want to try a hotter glow plug. If anyone has any ideas what might be wrong, please let me know. Cheers!

 

[Sprocket]

Try spinning it the other way. Looks like your prop was made to spin clockwise from the back, and if I remember correctly, that's how model airplane engines run, even though they might run backwards. Also, try a "chicken stick" even though you have something protecting your fingers.

 

[Cogsy]

I agree with Sprocket on both counts. When I flew RC the engines would start up and run backwards but never ran as well as forwards (and you are trying to run yours backwards) so changing the direction may help. Plus, a chicken stick is a very good idea as the prop can and will do nasty things to your fingers when you least expect it. For example, at the 0:49 mark in your video when you pull it over TDC like that, as unlikely as it seems, it can fire and run at that point and your fingers get chewed up quickly.

 

[minh-thanh]

IgorW !
Try with more heavy propeller

 

[NickP]

Looking good Igor - previous writers have mentioned direction of rotation and hand protection , however I would also add (as an RC flyer of over 35 years) I don’t believe hitting a prop is a good idea - you can injure yourself or damage the prop. If the engine is small enough you can also bend the con-rod in the event of a hydraulic lock.
The best technique for hand propping does take practice but in my experience involves a flick of the wrist. This way I can hand start small engines (.15 cu in) to large petrol 80cc. The really tiny ones often had starter springs fitted as they could be tricky to hand start. Some people prefer electric starter motors as they keep fingers out of the prop arc and give you several revolutions rather than just one for the motor to catch but these can again damage con-rods if you flood the motor (more likely if you haven’t found the mixture setting and/or are set rich for running in).
Best of luck with the motor. It’s aleeady running backwards so should be very close to successful runs forwards. Hope you don’t mind my two penny worth - let us know how you get on.

 

[IgorW]

Today I've made another reed valve flap (petal?), this time bigger, covering the intake hole better then the previous one. Checked it with my mouth blowing and sucking air through the intake. I think it seals better - but thats just the 'mouth comparison'. It tries to run. I can clearly hear the combustion. Sometimes it would rev up a bit, hold the revs for 2-3 seconds and then die. I've got several runs like that today.

@Sprocket, Cogsy - I may be wrong but I think that 2 stroke engines with a reed valve don't have a 'set' direction. They may be used to power something in a particular direction but only rely on the piston going up and down. When I was 16 we have started a dirt bike backwards - it had 6 reverse gears but i digress...
About safety ... Yes, your both right. I should't have started it with my fingers. I found an old tooth brush with rubber coating - safe for fingers and the little prop - which acts as a chicken stick when I hold it at the 'business end'.

@minh-thanh - I've been ahead of your idea and first thing in the morning i made a flywheel from a piece of aluminium i dug up from underneath my old lathe. It made a difference but I think its still too small.

Few other things to try:
- Dissasemble, clean and assemble back again using some automotive grade silicone to seal the crankcase as I suspect its leaking. Something that translates directly from Polish as 'left air'...
- The exhaust port is tiny. The engine is 12x12mm (just shy of 1/2 inch) bore\stroke and the exhaust port looks like 4-5mm (0.2 inch) and its just a drilled hole. I don't know the exact durations, but it looks good by eye. First the exhaust opens, then the trasfer ports. It run and revved up a bit so i think the timing is not that bad.
- Reed valve... So the lung test is one thing and running the engine is another. I think i should try the rotary valve concept even though I don't like it. Will have to make new backplate.

Now when I see it starting, reving up and suddenly dying it seems like a fueling problem.

EDIT:
@NickP Thank you for chiming in Yes, I will learn the safety notes by heart. For now I've changed the prop to a flywheel as I'm not going to fly It. I've bought the prop only for the looks and cooling.

 

[Cogsy]

You are right that the engine doesn't have a set rotation, but I think the flywheel effect of the prop is reduced when it's turning backwards, or something like that. I know RC aircraft engines just don't run nicely in the wrong direction, but you can put a reverse pitch prop on and run then backwards just fine.

 

[bluejets]

Looks to me like the fuel tank ( or whatever is used...not shown in the photos) is sitting waaaaay up above the engine.
Result would be flooding of fuel with the needle open.
With the needle shut to stop flooding, the motor won't run.
Normal practice with a vented tank is , ( say for example a tank around 40mm square) centreline of tank should be around 10mm below centreline of needle valve.

 

[minh-thanh]

IgorW !
This is a 13mm inner diameter cylinder and exhaust port, hopefully it will helpful

 

[mu38&Bg#]

You are right that the engine doesn't have a set rotation, but I think the flywheel effect of the prop is reduced when it's turning backwards, or something like that. I know RC aircraft engines just don't run nicely in the wrong direction, but you can put a reverse pitch prop on and run then backwards just fine.

If the engine is designed to run either direction (reed, piston port) it most certainly doesn't care about the prop. Prop efficiency is poor when used incorrectly, but it has no impact on engine performance.

Between a tiny exhaust port which limits breathing with an oversize carb for a 1.3cc engine means the carb isn't feeding fuel. Venturi bore must be no larger than ~Ø2mm.