My first IC-engine - smaller version Webster four-stroke

[rake60]

Don't give up on it sorveltaja.

First we are model builders and then we become repair mechanics.
I built bugs into every model I've ever made.
Identifying and fixing those bugs is all part of the game.

I have engines were completed 2 years ago that have never run.
Someday the light will come on to get them there.

Rick

 

[Maryak]

Sorveltaja,

I,m with Rick

It WILL sort itself out - take a break - have a fag and schnapps or vodka or some other suitable medicinal aid to good health.

We're on your side sunshine

Regards
Bob

 

[wareagle]

Sorveltaja, hang in there! The little guy will run unless you decide it won't. It just needs a little persuasion, that's all.

On the ignition woes... Can you adapt a hall effect ignition into the design? Just a thought... There are many different ignition systems out there, it is just a matter of finding one that will fit the bill.

The compression problem is nothing more than a problem. And there is a solution to that as well. Just a matter of massaging it a bit!

Keep at it! You'll get there!!

 

[NickG]

Use the ignition system from Jan Ridders pressure controlled two stroke. It uses a roller microswitch which are very cheap and take very little power to operate.

http://heetgasmodelbouw.ridders.nu/Webpaginas/pagina_drukgestuurde_tweetakt/druktweetakt_frameset.htm

Scroll to near the bottom of that page for the circuit diagram.

Keep going with it, you will be able to improve those valves by lapping them in to get compression back.

Nick

 

[Twinsquirrel]

I dunno how micro switches would last with all that arcing I suppose the capacitor would limit that to some extent but I wouldn't like to contradict Mr. Ridders.

Keep going I think we are all with you at every step on this one, definitely EOM material IMHO.

David

 

[NickG]

I can only assume the current is that low that not much arching occurs. Good point though. I wonder if you could use some kind of optical sensor on there like some aftermarket electronic ignition systems do?

 

[wareagle]

I'll chime in with an educated WAG on the micro switch arcing potential...

There are numerous factors that effect arcing and the intensity of it. Voltage, current, gap distance, material and time all play factors in arcing between two contacts. For this, we'll keep it simple. If you have a low voltage with little current behind it, then the arcing will be minimal to non-existent. Even if there was some arcing, the heat generated by the arcing wouldn't be that great, and the contacts would survive for some time. On the other hand, if the voltage was fairly high, and there was some current behind it, then there would be some arcing taking place, and the longevity of the contacts would certainly suffer. On an engine, the time that your gap would be at an arcing distance will be very short in duration. This will reduce the likelihood of arcing, and if there was arcing taking place, the heat build up would be somewhat controlled because the arc is of a very short duration of time.

These micro switches are very inexpensive and likely readily available (they are in the states - not sure about other countries). With everything in consideration, I wouldn't hesitate to use a micro switch in this manor. If it fails after say 40-50 hours of use, then throw another on it and keep on going. My bet is it would last a surprisingly long amount of time.

 

[NickG]

To be honest, I'm not sure if that'll work! That's still a low voltage, usually, you'd have a high tension spark. i.e. thousands of volts. For this you'll need a battery that gives out a higher current I think, most people used motorbike coils and a battery with a bit of umph. Jan ridders uses the power tool type batteries.

I know what's happening there. The valves are leaking. So when you turn it over against the compression, piston is approaching TDC it feels springy which is good, but then when the crank gets past TDC it should spring back on it's own. But on yours the air is leaking past the valves slightly so then the piston has to create a vacuum to get back to bottom dead centre rather than using the pressure it should have held to spring it back.

If that doesn't make sense PM me and I'll try to explain it better. In short though, your piston sounds like it's a good enough fit, but the valves aren't sealing properly. The pressure is building up but leaks out before the piston starts to return. It should hold that pressure, if you get that right and the timing is right it should work!

 

[Bluechip]

Hi Sorveltaja

About 15 kV at the plug is a commonly quoted figure, for what it's worth.
I've seen others !

You need a coil, CB/whatever, and the capacitor is essential with a C/Breaker.

dave

 

[NickG]

You could try to seal those valve guides / seats with PTFE tape or thread sealant. That's what I did with my hot cap on my hot air engine. When it wasn't working that was the area it was leaking from so just wrapped more PTFE tape around it. Not sure if it'll stand up in a combustion chamber though so the other method with the accurate location diameter will be better. Then what do you do? Loctite them on or solder.

I agree, leaving a sharp edge for the valve seat will give you a much better chance of getting a seal, it would only require minimal lapping in.

This is what it's all about, problem solving and learning!

Nick

 

[NickG]

That should work better now! You could just put the inlet valve on the top of the block as per the webster drawing. I don't think you'll have room on the cylinder head, especially as yours is smaller. Also, there would need to be enough meat in the head for the intake port & carburettor.

Remember the intake valve spring only needs to be very very light.

Your exhaust valve spring only needs to be stiff enough to stop the valve bouncing. If you make it too stiff it will just cause unnecessary losses.

Regards,

Nick

 

[wareagle]

Looks like you are whipping 'er into shape! Great work!

 

[NickG]

Looks good, hopefully you will get good compression now.

Nick

 

[CrewCab]

Finally on the right track!!

Good to hear, please keep us updated

CC

 

[chuck foster]

;D 8) ;D 8) :bow:

keep us posted

chuck

 

[ksouers]

Woo Hoo!! :big:

 

[wareagle]

That's an encouraging sign! Sounds like you have it by the hair now!

 

[Maryak]

Sorveltaja,

I admire your tenacity :bow:

Best Regards
Bob

 

[crankshafter]

Finally on the right track!! When spinning the engine with spark generator + alcohol, it makes small pops .

It almost kicks, but carburetor and tank are not attached yet ;D

Have managed to start your tiny Webster

 

[Kimmo]

Hello everybody. Wondering sorveltaja`s whereabouts. You woudn`t be in Finland? Sorveltaja sound like a finnish joke.