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



## sorveltaja (Sep 4, 2008)

--


----------



## Twinsquirrel (Sep 4, 2008)

Welcome,

Very nice so far, super ambitious....that's what we like

David


----------



## cfellows (Sep 6, 2008)

I'm very excited to see your progress and how this works out. 

I'm particularly interested in the Piezo-Electric igniter. What kind is it and where are you getting it from?

Also, what are the bore and stroke of your scaled down engine?

Chuck


----------



## Bluechip (Sep 9, 2008)

Hi Sorveltaja

Re: PTFE insulated Spark Plugs.

If you have access to it, there was a write up in Model Engineer 5 July 1991 on the subject.

Plug Thread was 5/32" x 40 tpi.

Might be interesting to you.

Dave


----------



## Maryak (Sep 19, 2008)

Great innovation with the coins and much food for thought :bow:


----------



## Twinsquirrel (Sep 22, 2008)

That looks like some very good work..... Keep those pictures coming!!!!!!

David


----------



## kustomkb (Sep 24, 2008)

Very nice work, I am looking forward to see how the piezo works out, seems much simpler than coil/ battery.


----------



## wareagle (Sep 27, 2008)

I have been watching this unfold, but haven't chimed in until now. This is an interesting build. Thanks for taking us along on the journey!

BTW Hang in there, you'll figure out your ignition! When there's a will, there's a way.


----------



## steamer (Sep 28, 2008)

W/E is right.....As a good friend said to me on a particularly tough build....keep going your doing fine, you'll figure it out.....And I did.

So will you.

Dave


----------



## Maryak (Sep 29, 2008)

Sorveltaja,

Keep at it mate, what I know about electricity could be written on the back of a postage stamp ???

I'm sure you'll figure it out and when you do, perhaps I can make something other than a diesel, (assuming the one I'm making works). :

Bob


----------



## CrewCab (Sep 30, 2008)

sorveltaja  said:
			
		

> On the positive side, one thing learned about electricity ;D.



 ............... RIP faithful Multi Meter ....... look on the bright side, you are here to tell the tale, guys, please all be careful out there with electrickery, it can bite 

sorveltaja, this is a good thread, please make sure you stick around to keep it going ;D

CC


----------



## CrewCab (Sep 30, 2008)

sorveltaja  said:
			
		

> if any luck, laboratory conditions are almost ready for testing 8).



Good to hear, looking forward to seeing the completed version .............. gotta say it does seem incredibly small, very well done for working at that scale.

CC


----------



## MadKad (Oct 6, 2008)

lol I like the idea of the spark plug 

I am not to sure my self on what you were woundering what will happen to the PTFE in the part dirgram yo made, but I know that PTFE is great at high friction and high heats, well thats why they use the stuff on non-stick pans.


----------



## kustomkb (Oct 7, 2008)

Great work! I didnt realise the scale of it until I saw that 9V battery, Cant wait to see it run.


----------



## cfellows (Oct 8, 2008)

sorveltaja

How sure are you that you're piston isn't letting some air out around it? 

I've built engines where I was pretty sure the piston was airtight only to find out that adding rings or o-rings greatly improved the compression.

Chuck


----------



## NickG (Oct 8, 2008)

Wow, that is on a small scale. I'm glad you've left the piezo ignition idea, I was keen to see how you got on with it however, I remember seeing some comments by Jan Ridders that it takes a lot of power to drive them. In fact, on his vertical 2 stroke engine with a much larger cylinder bore and stroke than yours he had to resort to a circuit with coils and a roller micro switch operated by a cam. It takes much less force to drive it and looks neater.

Love the spark plug idea, I would be aiming for a CR of at least 5:1.

Nick


----------



## wareagle (Oct 8, 2008)

I am just trying to throw a few things out to possibly look at, so if you have, then please ignore. 

It the vlave timing right? In other words, is the intake valve opening when the piston is travelling away from the valves to let the air in the cylinder? If it isn't, you won't get much compression if at all because you aren't filling the cylinder with air. The exhaust valve must be closed during the compression stroke or the air will simply leave the cylinder. Another thing that seems to be a potential issue is the valve seats. Are the valves sealing on the seats? And the last item is the valve body and the cylinder... Is that connection air tight?

How much clearance do you have between the piston and the head at top dead center? If you have an abundance of space left over in the cylinder, the compression will certainly suffer.

If all of the valves seal, and the timing is right, the piston seals to the cylinder walls, and your compressed volume is narrow, then you should have compression. Somewhere there is a leak. You might be able to use some soapy water to find it.


----------



## NickG (Oct 9, 2008)

What does the compression ratio of your version work out at? It's the swept volume / dead space I think! Or is it swept volume + dead space / dead space? Can't remember!


----------



## wareagle (Oct 9, 2008)

Very nice looking fuel tank. I am getting anxious on this one! Keep up the good work!


----------



## Twinsquirrel (Oct 12, 2008)

Reminds me of those boys in thier 1.1 litre Citroen Saxo's (compacts for our friends in the U.S) with 8" exhaust tail pipes! ;D Kind of suits this little one though, it's looking great.

David


----------



## rake60 (Oct 14, 2008)

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 (Oct 14, 2008)

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 (Oct 15, 2008)

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 (Oct 15, 2008)

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 (Oct 15, 2008)

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 (Oct 15, 2008)

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 (Oct 15, 2008)

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 (Oct 17, 2008)

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 (Oct 17, 2008)

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 (Oct 17, 2008)

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 (Oct 18, 2008)

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 (Oct 19, 2008)

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


----------



## NickG (Oct 29, 2008)

Looks good, hopefully you will get good compression now.

Nick


----------



## CrewCab (Nov 1, 2008)

sorveltaja  said:
			
		

> Finally on the right track!!



Good to hear, please keep us updated 

CC


----------



## chuck foster (Nov 1, 2008)

;D 8)  ;D 8)  :bow:

keep us posted

chuck


----------



## ksouers (Nov 1, 2008)

Woo Hoo!!  :big:


----------



## wareagle (Nov 1, 2008)

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


----------



## Maryak (Nov 1, 2008)

Sorveltaja,

I admire your tenacity :bow:

Best Regards
Bob


----------



## crankshafter (Nov 17, 2008)

sorveltaja  said:
			
		

> 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 (Nov 5, 2019)

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


----------

