Jan Ridders Pressure-controlled Two-stroke engine

[John Somers 2Participant @johnsomers2]

Like Jim I have also recently completed building Jan’s Simple Two stroke and like Jim and others on this forum, the engine steafastly refuses to run for longer than a few seconds. It will fire quite happily aided by the ‘start’ drill and on one occasion ran for something like 30 seconds.

 

An account of my build is featured on my blog and whilst I am reluctant to abandon this project I am running short on possible solutions to this perplexing problem.

 

The engine does seem to be very sensitive to the level of fuel in the carb and, more understandably, to fuel mixture. Mine appears to be happiest with a very rich mixture (air valve almost closed). This suggests air is being sucked in further down the induction line but I don’t think this the case.

 

I first tried a coil and micro switch type of contact breaker which produced a healthy fat blue spark but the micro switches didn’t appear to have the stamina to be used for this purpose. In the end Ielected to replace with an RCEXL CDI unit in the hope that this may provide a magical cure.

 

It is curious that a number of people are experiencing the same difficulties and hopefully someone out there might know the answer.

 

John

[Richard ParsonsParticipant @richardparsons61721]

Ah! Good Gentles all. I worked in an unheated shed in the U.K. Mine is now heated –by law’. I got a right royal growling from the Rendorsheg –rozzers or Old Bill to you and me- repairing a snow blower out of doors!

I know that you are suffering from the COLD.

Remember that it takes energy to vaporise petrol and the cold air will not do it to the required amount. I will bet that the ‘Good Hollander’ has a heated workshop. Most continentals recon that the English are as ‘mad as hatters’ and will work (for the love of the work) in places and temperatures that a continental would only be seen dead in!

[Jim GreetheadParticipant @jimgreethead]

Can’t be the cold, it is still summer out here on the fringes of civilisation. Temperatures in the mid to high 20s. Winter, of course, is a different matter.

 

I keep telling myself that it can’t be all that hard. After all, it is just suck, squeeze, bang and blow. And two strokes are so simple. Aren’t they?

[John OlsenParticipant @johnolsen79199]

Hi James, Simple is not the same thing as reliable. I got a lot of fun out of watching my mates change plugs on their two stroke motorbikes. Size for size they might have been marginally faster, but they burnt more gas and used many more sparkplugs. Mine started much more reliably too.

 

Hopefully you have not been too affected by the surplus of water over there recently?

 

regards

John

[Jan RiddersParticipant @janridders31649]

Hello folks, here Jan Ridders.

I feel sad (and somewhat “guilty”) to read about the persistent problems some of you have with letting my “pressure Controlled 2- stroke” run. Just today I took my engine out of the cabinet where it was “resting” for some months. I did that because of the recent postings and remarks here again. I put only only some droplets of petrol in the carburetor and cooled the carburetor down anywhere between zero and 5 degrees Celsius in my home freezer ( I used the separate carburetor that I use for all my experiments). I could start the engine very easiliy with some few pushes to the fly wheel by hand!
So, to invalidate some suppositions and remarks:
– Although the vapor pressure will be lower at lower temperatures indeed this doesn’t effect the working of this carburetor identifiable;
– The level of the petrol in the tank is of no influence also.
At least this is true while using fresh petrol.

I will add an extensive trouble shoot part on the page for this engine on my web site within two days from now; I will report that here if it is ready. Because there are some changes on the present drawing plan compared to the plan in ME I think it is advisable to use my most recent plan that I will send you immediately by mail if wanted:
jan.ridders@tiscali.nl or jan.ridders@gmail.com

The most important change is an improvement of the ball valves making them less critical. If there was a problem with this engine the valves were the reason in almost all cases according to my experience.

 

I hope that something on my trouble shoot list will solve your problem because this engine is easy to make and to start in my humble opinion and experience.

 

So long and don’t give up (sorry for my limited English).

Jan Ridders

 

 

[Richard ParsonsParticipant @richardparsons61721]

Jan I fear that the whole engine has to be cold. I and my mates seldom were able to fly our control-liners on a nice clear crisp winter’s afternoon. Our little CI engines just would not start. In Ted’s shed which had an electric fire they would start after they and us warmed up a bit.

There is a way to settle if the problem is fuel or ignition. It is to remove the plug and place a small (birthday cake) candle very close to the plug hole. You then spin the engine over. After a few revs if she is getting a good mixture she should give a ‘poof’ or two. No poof – no fuel mixture. Jan’s spark indicator should tell you about the spark and might well improve the internal spark’. I have had big fat blue sparks on the old Villers two strokes but they just would run. Generaly it was a Duff plugs

James – as Jan says these engines must be free running as “as driven by the wind”. They have very little power and are probably only just self sustaining. Perhaps a little more ‘lapping’ would not come a miss.

[Jim GreetheadParticipant @jimgreethead]

John Somer’s engine is much prettier than mine. After hearing of his problems, I took a few short cuts (sorry Jan) in regard to the purely decorative parts of Jan’s beautiful design. If I get it running, it might get a coat of paint.

 

Thank you Jan, for your continuing interest in our attempts to replicate your beautiful work. I would be really interested to know how you made the teflon bearing so smooth and yet still sealing. I took a lot of care with this but it is still not as free-running as your engine.

 

And I am very interested to hear about the ball valve. I assumed that it was just another version of the reed valve on two stroke engines but it seems that yours is different. Can you explain the difference please?

 

And it can’t be the cold. Yesterday was about 23 degrees and today is forecast to be the same.

 

Richard: I have not previously thought of using a birthday candle like that. But I have been using a Colortune transparent spark plug that lets me see the spark and the flame in the cylinder. The flame colour varies with the mixture from yellow (rich) through bunsen blue (about right) to almost white (lean). I will try to get some video of it to put up so all can see,

 

I did take some video showing how free-running the engine is (or isn’t ) but I hesitate to put it up because Jan will see the changes I made to accomodate my limited skills.

 

Thanks everyone, I will keep you posted

Jim

 

[Jan RiddersParticipant @janridders31649]

Hello James,

If you send me a mail I will send you the present drawing plan with the improved ball valves with it; mail to: jan.ridders@tiscali.nl

The change is that the balls are in a kind of small cavity on the connecting pin(?) above the ball so that the ball only have a free space of some tenth’s of a millimeter in both vertical and horizontal direction. That avoids floating so the ball falls back on its seat in time.

Don’t bother about the cosmetics of the engine, I am not that good as well. I saw some replica’s that look like jewels. The most important thing is that it runs.
Friendly greetings from Holland,

Jan

 

[Jim GreetheadParticipant @jimgreethead]

Thank you Jan, I will certainly send an email and look forward to seeing the changes.

 

I spent a lot of time today trying to reduce the friction in the engine and I am convinced that it now as good as I can make it. It is still not as free-running as yours.

 

I also took some more Colortune video which shows that even with the correct mixture, the engine does not fire consistently. So I am wondering if the problem is the ball floating as you suggest.

 

I also have not fitted the exhaust to the engine and maybe that is part of the problem. I know that the inertia of the gases is important in two strokes and that the exhaust can have a big effect. So I will do that next.

 

Jim

 

[Jan RiddersParticipant @janridders31649]

Hello Jim,

I just send the drawing plan as a reply on your mail.
The exhaust silencer for sure can influence the process for most (industrial) 2-stroke engines, but not with this model; it damps the noise somewhat but in fact it is more cosmetic than functional. As a matter of fact you better leave it untill the engine is running well and than mount it to see if there is any effect, which I think is hardly or not the case.

Friendly greetings and success,

Jan

 

 

 

[Richard ParsonsParticipant @richardparsons61721]

Jan – I have messed about with 2 Strokes for many years. The exhaust system can be very important. It can help to both scavenge spent gas and draw in fresh mixture (the Kaaden effect). Some designs will not run properly unless there is some back pressure which prevents part (sometimes a major part) of the new charge escaping.

[Jan RiddersParticipant @janridders31649]

Hello Richard,

I am fully aware of the importance of exhaust systems to optimize the flushing process with 2-strokes to avoid loosing unburned gas mix on the one hand and to avoid remaining burning gasses in the cylinder (“poisening”) on the other hand. But if the pison is well adjusted relative to the exhaust opening in the cylinder all my 2-stroke models run very well with or without a muffler. For sure it will be possible to improve the efficiency but that is not important in case of these kind of models if you ask me.
So you are right in principle but this cannot be the real reason for the problems mentioned in this discussion about this model.
Thanks for your reaction,

Jan

 

[Jim GreetheadParticipant @jimgreethead]

I have now posted video of the Colortune plug test on YouTube at

 

http://www.youtube.com/watch?v=IEL06n7X_RM

 

I just hope this link works. I am not sure how else to do it. Comments and advice will be most welcome.

 

Jim

 

[Jim GreetheadParticipant @jimgreethead]

Sorry about that, it looks like the link does not work. But it is there if you go to AussieJimG and look for Debra Colortune.

Jim

 

[Jens Eirik Skogstad 1Participant @jenseirikskogstad1]

Posted by James Greethead on 15/02/2011 21:42:41:

I have now posted video of the Colortune plug test on YouTube at

 

http://www.youtube.com/watch?v=IEL06n7X_RM

 

I just hope this link works. I am not sure how else to do it. Comments and advice will be most welcome.

 

Jim

 

 

It fire in the combustion camber, but it will not make a working pressure on the piston by combustion gas. Probably poor compression, poor fit between piston/sleeve who are too leaky, then the combustion gas is blowing out of between piston and sleeve. The other problem can be retarded ignition angle.

 

Increase compression and igniton angle a bit before TDC.

 

 

Edited By Jens Eirik Skogstad on 15/02/2011 23:24:25

[Jim GreetheadParticipant @jimgreethead]

Thank you Jens, I am glad you found the video. I took the following measurements just before I did the test:

 

Exhaust port opening 162 degrees around BDC

Transfer port opening 112 degrees around BDC

Compression 25 psi

Ignition timing 2 degrees BTDC

 

The port openings were measured on the rim of the flywheel with steady pressure on the piston crown. They are probably withing 5 degrees either way. I can’t believe how many different values I measured, those are the best.

 

Compression is very low but the piston fits closely in the bore. One reason for the low compression is that the piston has a 6 mm radius fillet all around the crown which limits the minimum volume at TDC.

 

The ignition angle was measured with a timing light at cranking speed. Ignition is by RCEXL CDI which has electronic advance.

 

Jim

[Jim GreetheadParticipant @jimgreethead]

I have now posted a photo on this forum site of the Colortune test setup if anyone is interested.

Jim

 

[TerrydParticipant @terryd72465]

Hi Jim,

 

I can’t help you with your engine, but to post a working link use the ‘link’ icon (an unbroken ‘chain’) above the text box when writing a post. If you highlight a word or phrase in your text before adding the link it attaches the link to that word preventing the dreaded ‘adverts over messages’ problem with long URLs. Like this:

 

Here is your video

 

Hope this helps in future,

 

Best regards

 

Terry

[Jim GreetheadParticipant @jimgreethead]

Ah! So that is how it works. Thanks Terry.

[Richard ParsonsParticipant @richardparsons61721]

I have a good look at the Colortune images. I see what you mean. It seems to fire when there is mixture and from the images the mixture is correct. There is no sign of a ‘weak mixture’ firing.

The results show you either get mixture or nothing. Pity we cannot see the ‘bubbles’ in the petrol tank that might show us something. Erratic bubbling would say there is little or no ‘suction’ at times. At 1100 RPM she should be firing some 18 times a second which should give a continuous glow with a little ‘flicker’.

What could be causing it? Whatever it is it is intermittent so we can eliminate leaks in the pipe work. ‘Blow by’ would also cause a continuous leak as would a problem in the gland nut. So it must be the valves which sometimes close properly and more often do not. Are the holes nicely reamed and the valve faces a burnished/lapped finish? Is it possible for the valves to lodge on the side of the face? Are the balls truly round or have flats on them? How about ‘crud’ inside any of that the valve chamber(s)?.

[John Somers 2Participant @johnsomers2]

Jim

 

It seems that you are homing in on the source of the problem which also confirms Jan’s belief that most problems relating to poor running or even non starting can be traced back to the one way valve system. Like you I have spent a considerable amount of time focusing on this valve even trying a square edge seating rather than a taper as suggested by Bogs. I wonder if a very light coil spring to return the ball to its seating might help things though perhaps the resistance may be too high for suction to do its job. At least through your logical approach we have eliminated all other potential problem areas.

 

Richard raised the possibility that the balls may not be truly round. I have tried balls from different sources with this possibility in mind without any apparent improvement. In using a square edge ball seating I have gently tapped a ball into position to provide a good seal on the seating then replaced that ball with a new one. I really cannot envisage a way of producing a better seal unless a spring assisted arrangement could be made.

 

John

 

[Jim GreetheadParticipant @jimgreethead]

We all seem to be agreed that the reason that the engine will not run unaided is that it is not firing consistently. Once this is sorted, we can worry about reducing the friction if this still causes problems.

 

And the most likely culprit is the ball valve. As you suggested John, I started off with a square edge and tapping the ball. This is the normal approach. But a couple of times when I sucked/blew into the tube to check the seal, I found the ball had stuck. This could be because I used a 4mm diameter hole and the ball sat too far down and wedged.

 

But relieving the edge with a small chamfer did not make any difference.

 

I did try a light spring but this did not help. Perhaps I did not pay enough attention and this might be worth another try.

 

I also tried an acetal ball with is lighter in case there was not enough “suck” to lift the ball high enough. This was when I was still wondering if the engine was getting enough mixture to make a big enough bang. No difference.

 

You and John Woods both used Jan’s design without success. So how come this design works for Jan and not for other people?

 

Today, I will build one to Jan’s design but with a screw adjustment through the top to vary the maximum ball height. I don’t think my machining skills will permit me to get it right otherwise.

 

My other thought is that since this ball valve is doing the same job as the automatic inlet valve on my hit & miss engine (Bonza), I could use a spring loaded poppet valve. I am still playing with arrangements for this to try to get one that looks a bit elegant. But I might have to forget elegant and just make one. We shall see.

 

El Illegitima, nil grindem carborundum!!

 

Jim

 

[Jens Eirik Skogstad 1Participant @jenseirikskogstad1]

To test the compression under bottom piston with cylinder head removed from cylinder: Can you hear there is a good “Poof” sound when the transfer port is open while the piston is at way to BDC?

 

Can you smell there is mixed petrol/air out of transfer port with a “poof” sound while the engine are cranking by hand with cylinder head removed?

 

Maybe there is a stiff spring for non return ball valve or there is leakage in non return valve seat?

 

Can the engine keep compression pressure in longer time?

 

 

 

 

Edited By Jens Eirik Skogstad on 17/02/2011 10:52:42

[Jan RiddersParticipant @janridders31649]

Hello all,

I really appreciate all the remarks about the ball valves and most of them make sense. But I did a lot of experiments with these valves in the past (inclusive the ones that are suggested in this discussion) and finally found the best solution, at least for my engine and for others as far as they gave me feed back. I won’t say that this solution is heaven but my engine never fails (anymore) and starts very reliable after one or two pushes to the fly wheel. So I really suggest to make the valves exactly as they are now on the drawing plan; I will be glad to send this drawing plan to everybody who asks for it via e-mail (jan.ridders@gmail.com).
I promised you to make a kind of extended Trouble Shoot List for this engine, but I am not quite finished with that because of some lack of time. But I wrote the first 2 items that I paste here below:

“”Trouble shoot hints “Pressure Controlled 2-stroke Sabine”>>

> >

1. The mechanical frictions must be made as low as possible. >>

The power of this engine is relative low because of the small cylinder content of 4.5cc. Therefore it is important that the whole mechanism is running smooth and with low frictions; it must run “as driven by the wind”. That is the reason why there are no rings on the piston; they are not necessary if you make the clearance between the piston and the cylinder equal or smaller than 0.05mm.
Make sure that everything is lined out well and that the spacers on the crankshaft are placed (see drawing sheet 2) to prevent turning parts are touching each other. The spacers only may touch the inner rings of the ball bearings. >>

At the end of the video below there is a demo to illustrate what I mean by low friction in this case:
http://www.youtube.com/watch?v=DnYLEd_1euY&feature=channel_page>>

The rather low compression of about 2 ato (30 psi ) contributes also to this easy running and starting-up.

>>

2. The ball valves.
In fact the ball valves are the only real critical parts of the engine. If the engine runs bad or not at all most of the time there is something wrong here. The balls in the valves must not only close well on their seats but also in time! That means that the seats for the balls must be lathed very smoothly and that the free moving space for the balls must be small: about 0.5mm in the vertical direction and only some tenths of a millimeter in the horizontal direction. If this free space is too large the balls can start floating with the result that they don’t fa

[Jan RiddersParticipant @janridders31649]

Hello, here Jan Ridders again.

I saw that I apparenty crossed the limits for the text box with my previous posting.

Herewith the remaining part:

 

2. The ball valves.
In fact the ball valves are the only real critical parts of the engine. If the engine runs bad or not at all most of the time there is something wrong here. The balls in the valves must not only close well on their seats but also in time! That means that the seats for the balls must be lathed very smoothly and that the free moving space for the balls must be small: about 0.5mm in the vertical direction and only some tenths of a millimeter in the horizontal direction. If this free space is too large the balls can start floating with the result that they don’t fall back on their seats in time. That’s the reason why the balls now are in a small cavity on the connecting pins above them; see drawing sheets 7 and 8.
I did a lot of experiments with this ball valves and the present design appeared to be the best. A spring to keep the ball on its seat with a light pressure appeared to be not a good alternative because the spring pressure made the system only more critical and it was never better than the free ball solution according to my experiences. Also a 45 degrees seat for the ball turned to be better than a square edged hole; tapping the ball on it. The 3/16 inch steel ball is absolutely not too heavy; it will will always be easily lifted during the intake stroke. Sometimes it can happen that the ball sticks somewhat on its seat due to some kind of pollution. If you think that this is the case put some droplets of petrol in the valves that will loosen the ball in most cases.
So, if this valve system is made accurately according to the present drawing plan there should be no problem. Keep them clean also; if necessary wash them with some dry cleaning naphtha (no oil!), which could be necessary occasionally.””

 

Friendly greetings to you all

Jan Ridders

 

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