Jan Ridders Pressure-controlled Two-stroke engine

[Bill DawesParticipant @billdawes]

Interesting to see these posts on Jan’s engine. I started making it just after the plans were published in ME, not far off being finished now (yes I know it’s taken me a long time, other pressing engagements, familiar to most model engineers no doubt) I was beginning to think I was the only one in the UK building one as I had not seen any comments on the construction before. I did have a couple of queries at the beginning whhich was passed on to Jan who very kindly e-mailed me direct. It’s been an interesting first exercise in model engiineering, must plod on with it know.Look forward to see if I have any luck getting it started.

Bill D.

[Jim GreetheadParticipant @jimgreethead]

Well, I made a new ball valve exactly to the dimensions in the drawing except that I included the extra air tube in the valve body (using the correct dimensions) and added a screw to adjust the lift of the ball.

 

I have uploaded photos of the new valve including the inside and some video of the result and you can find it at http://www.youtube.com/watch?v=4vmnOxkSIos. Despite Terry’s advice, I could not figure how to give you a simple link – sorry about that.

 

The tank and ball valve combination works alright on my 30cc four stroke engine Bonza both with, and without the ball. But the engine faded away after about 30 seconds. The tank had become quite cold from the evaporation and found that Bonza would start again and keep running if I held the tank in my hand to keep it warm. So maybe Richard was right about the cold. But that is clearly not the only problem.

 

I made an adapter to fit the valve assembly to the much bigger Bonza tank and connected it to Debra. The tank did not get cold but the engine did not run any differently.

 

The Bonza test shows that the ball is lifting ok but, because Bonza is a 4 stroke with its own inlet valve, it does not show that the ball is seating reliably or in a timely manner.

 

I have now designed a poppet valve assembly but I will not have time to construct it until Monday. It will be interesting to see what happens.

 

I am convinced that friction is not the problem at this stage. The Colortune plug clearly shows that the engine is not firing correctly. When this problem is overcome, I will worry about friction if necessary. Incidentally, unless my maths is wrong, an engine with 24 mm bore and 24 mm stroke has a capacity of 10.0cc (or am I calculating it wrongly).

 

Please keep the comments and suggestions flowing, I need all the help I can get.

 

Jim

[TerrydParticipant @terryd72465]

Hi James,

At 24mm dia by 24 mm stroke I make the swept vol. about 10.85cc:

1.2² x pi x 2.4 = 1.44 x 3.14 x 2.4 = 4.52 x 2.4 = 10.85 approx.

In order to add links just copy your URL and highlight a suitable word or phrase such as James Link. Then click the ‘link’ icon at the top of the message box (arrowed).

 

 

Then paste your URL in the box shown below (Arrow). I then choose for the link to open in a new window (short arrow) so that you keep the Model engineer window open.

 

Hope that makes it clearer, sorry if I confused you earlier.

 

Best regards

 

Terry

Edited By Terryd on 18/02/2011 10:02:25

[Ian S CParticipant @iansc]

Jim, a rough calculation gives10.86cc, so your near as need be. Ian S C

[Richard ParsonsParticipant @richardparsons61721]

John there is one little point. Jan writes

The power of this engine is relative low because of the small cylinder content of 4.5cc.

I have avoided quotation marks as these give rise to smiles. Now your engine is 24mm bore by 24mm stroke. That is 10.857 cc if this is the swept volume then it is 2.413 times that of Jan’s statement above, but you do not describe the dimensions of the piston. If the cylinder has a swept volume 10.875 cc then remember the ‘Cube Square’ law. So the tubes should be 3.75 times larger.

A ball valve only makes contact with its seating at one line around its circumference. If there is any roughness or ovality in the seat whether it is sitting on a flat surface or in a chamfer this includes the hole. It will leak. You could also suffer from porosity in the metal.
If the ball came from an oriental source it may be soft or not spherical. Did you try a new ball? Tapping them with a mallet to seat the valve will do no good if the ball is not round as the thing floats free. I have had problems with this sort of thing with clack valves in the past.

 

By the way we used to build primitive Fridges with a few bricks and porous roof tiles. It was powered by pouring petrol over it. They worked but you had to put your stuff in good quality plastic bags.

[VersabossParticipant @versaboss]

Off Topic:

Thanks to the umpteen description before and now the latest by  Terry I can now definitely say that the method for creating a link is flawed. I did some experiments, step for step as pictured above, and got no links.

I suppose it is dependent of the browser, but I am not willing to throw away my trusty Opera.

Greetings, Hansrudolf

[TerrydParticipant @terryd72465]

Edited By Terryd on 18/02/2011 13:07:51

[TerrydParticipant @terryd72465]

Hi Hansrudolf,

I am trying the method of adding links in Opera so here goes.

Jim’s Video link.

It appears to have worked, however in a previous message the browser would not let me edit the link so there may be a problem there.  I will now post the message and test the link.

Best regards (fingers crossed)

Terry

[TerrydParticipant @terryd72465]

Hi Hansrudolf,  

It seems to be successful using Opera.  Just make sure that you paste the Url into the top box of the ‘link’ window.  It is better to copy and paste rather than try to type it in.

Regards

Terry

[Jim GreetheadParticipant @jimgreethead]

I tried creating a link with Google Chrome. I arrived here with the target URL on the clipboard.

 

Then I highlighted a word like (here) and clicked on the unbroken link above.

 

Everything went into a light blue mist and stopped. I had to kill out using right click/back and then come into the Forum topic again.

 

That is what was happening before as well and I thought I was doing something wrong. Maybe I was. Maybe I still am. Maybe it doesn’t work with Google Chrome.

 

First the engine, now this. I am not having a good time am I?

 

Jim

 

[TerrydParticipant @terryd72465]

Hi Jim,

 

The links facility appears not to work with Chrome, I have the same result as you.

 

Terry

[Jim ArnottParticipant @jimarnott21196]

Hi Jim,

A little thought have you tried the engine now you have modded it without the colourtune?

 

as If your colortune is like mine it needs an adaptor to fit into this sparkplug hole.

 

Introducing a lot more volume in the combustion chamber .. and it’s self maybe making the low compression very marginal.

 

Jim

 

[Jim GreetheadParticipant @jimgreethead]

Terry – Thanks. One problem down, one to go. I will use a different browser next time.

 

Jim – A good thought. I don’t have an adapter but the heads are so simple that I just made another one with 14mm spark plug hole. But the Colortune does introduce additional volume so I will change the heads and try it.

 

Jens – I will test for the “poof” when I have the head off. I get compression at the entrance to the expansion chamber but it will be interesting to see what happens at the cylinder.

 

Richard – You are a legend. Who would have thought of keeping the steaks cool until lunchtime with evaporating petrol and then just throwing a match in?

 

Overall, I am not sure how critical it is to have a perfect seal at the ball. Four stroke valves have to seal to stop them from being burnt by the hot gases but we don’t have this problem here. And we have all had four strokes that continued running while waiting for us to do a valve job haven’t we? A static test (by blowing into it) shows that the balls are seating very well. We just don’t know if they are doing it at the right time.

 

Not beaten yet.

 

Jim

 

[Jan RiddersParticipant @janridders31649]

Hello all,

I think there is some confusion here !
In the article of Model Engineer no 4333 Aug/Sept 2008 my “Simple 2-stroke engine” and my “Pressure Controlled 2-stroke engine” were mixed up: in fact the subject was the “Pressure Controlled 2-stroke” (see pictures and drawing plan) but the text was mainly about the “Simple 2-stroke”. The editor rectified that in some later issue of ME.
Now I recognize the same mix-up in this postings: on the (very nice) video with the Colortune spark plug I see the “Simple 2-stroke engine” and also the calculation about the engine’s content from Richard and Terry are based on the “Simple 2-stroke” that has a piston diameter and stroke of 24mm: so 10.8 cc content indeed.
But I am constantly talking here about the “Pressure Controlled 2-stroke” (and I think James and John are doing it also) and that engine has a piston diameter and stroke of 18mm, so the content is about 4.5cc as I stated before.
So, the power of this engine is significantly lower than that of the “Simple 2-stroke” . If, additionally, some ignitions are missing (which can happen with 2-strokes) the power will decrease even more. Therefore I emphasize the importance of low frictions for at least keep the engine running. So please mount the spacers on the crank shaft (they where not on the ME plan I believe) to make the engine run “like driven by the wind” . You only can adjust the engine to its optimal performance once it keeps running more ore less well.

Friendly greetings from Holland,

Jan

[Jan RiddersParticipant @janridders31649]

Hello, here Jan again.

I read some concerns about the low temperature of the petrol in the carburetot tank. Due to the evaporation the temperature of the petrol will go down somewhat indeed ( the physics in Holland is the same as in the rest of the world, ha ha). This is one of the reasons that after some minutes of running the speed of the engine can go down a little. But if you then reduce the extra air at the outlet of the carburetor a little you will see the engine run faster again and the situaton will stabiilze because the temperature of the fuel will not decrease futher at some point.

Another reason why the speed of the engine will go down somewhat after some minutes is the evaporation of the most volatile component in the autocar petrol. But that will stabilize also after some minutes. You can eliminate this separtion effect by using Coleman Fuel since this has much less (different) carbon hydrogen components.
Friendly greetings from Holland,

Jan

PS. I will measure the temperature decrease of the fuel during the first minutes of running exactly one of these days, only for my (and your) curiosity.

[TerrydParticipant @terryd72465]

Hi Jan,

 

I was not familiar with your models until I received your drawings for the ‘Sabina’ engine which is the subject of this thread (Pressure Controlled 2 Stroke). It was only when I got these plans that I saw it was a vertical cylinder engine and the one in the video is the horizontal ‘Debbie, I found that very confusing.

 

It was only when I visited your lovely website that I saw the difference. My calculations were based on the measurements given in this thread which are those of the ‘Debbie’. So I apologise for misleading anyone and thank you for your generosity in sending me the plans.

 

Best regards

 

Terry.

[John Somers 2Participant @johnsomers2]

Hello Jan

You have cleared up a small mystery for me. Until the last day or so I wasn’t aware that there was an alternative engine to ‘Debbie’ Simple Two Stroke (which is the engine I think I have built !). My friend Aussie Jim reffered to his ‘Pressure Controlled Two-Stroke’ that he calls ‘Debra’ as he felt this made it sound superior. I believe that both Jim’s and my engines are both ‘Debbie’ Simple Two Strokes – am I correct ?

 

I am currently away on holiday at the moment so am unable to make further progress with my ‘Debbie’. My engine spins freely almost to the same standard as yours – 5 revolutions with no compression from plug or chamber, 3 revolutions with just chamber and 1 to 2 revs with chamber and plug in place.

 

If my engine is not firing consistently on every revolution as Jim has discovered is the case with his, then surely this could be the reason for not running without assistance. Perhaps you may care to look at the short video of me attempting to start my engine. I appreciate that it may be very difficult to advise me from this alone but something may be obvious to you.

 

With thanks for your continued support on this perplexing issue.

 

John Somers

 

 

Edited By John Somers 1 on 19/02/2011 14:07:11

[Jim GreetheadParticipant @jimgreethead]

Confusion all round, and all my fault. Sorry about that. I had forgotten about the earlier 2008 article but I remembered reading John Woods Forum thread.

 

When I had problems, I simply tacked onto the thread without checking. For some reason, I just assumed that “Pressure-controlled”, “Simple Two Stroke” and “Debbie” were alternative titles for the same thing.

 

In regard to the name, I didn’t know that the Simple Two Stroke Engine was called Debbie until John Somers mentioned it. And mine is not called Debra to make it sound superior despite John’s mischievous suggestion. After I made some small changes to Jan’s design of Debbie, I felt that I had also to make a small change to the name.

 

Anyone seeing Jan’s original and John’s superb and beautiful copy would agree that if they were all real people, they would not have anything to do with my scruffy and very lower class Debra as shown in the Colortune videos.

 

If Debra runs, maybe I will tart it up. If it runs.

 

Jim

[Jim GreetheadParticipant @jimgreethead]

I have done some more work and here is the result:

 

Jim: I tested it again with the CM6 plug head and it made no difference.

 

Jens: With the head off, I get a very distinct “poof” from the transfer port. There is a general smell of Coleman fuel.

 

Jan: Your mention of two strokes misfiring led me to wonder if the cranking speed was too high for the (effective) throttle opening thus causing four-cycling like motorcycles do when the throttle is closed. After extensive tests, particularly at lower cranking speeds, I have concluded that this is not the cause of the problem.

 

To see if the ball valve really is the cause of the misfiring, I have replaced it with a poppet valve. I can see this valve operating. And it makes no difference. The valve and the tests are on YouTube and if TerryD’s advice is correct, you should find it here. Thanks Terry, it worked.

 

So I am not sure where to look now. The problem is not friction (because it is misfiring when cranked) and not the ball valve (because it is still there when the poppet valve is substituted for the ball valve).

 

I am wondering if, when it fires, it blows the next incoming charge back or contaminates it in some way. The only way I can think of to test this is to put another non-return valve right at the transfer port on the cylinder where the mixture in injected.

 

Any advice anyone? I am running out of ideas.

 

Jim

 

[Jan RiddersParticipant @janridders31649]

Hello Jim,

I am beginning to think your engine is “poisening” itself (too much burned gases left in the cylinder). The flushing process can be influenced by the adjustment of the cylinder relative to the exhaust opening. You can vary that by srewing the piston rod more or less in its fork. I found out that at the best adjustment the piston in its lowest position (BDC) is equal or somewhat below the bottom edge of the exhaust hole (so completely open). But you I already know that I suppose.But maybe you can do some experiments anyway.
Once I perceived somebody mounted the cylinder upside down (which is easily possible) and then the exhaust opening is on the wrong place of course. But I can’t imagine that you did something like that.
Friendly greetings,

Jan

 

[Jim GreetheadParticipant @jimgreethead]

Hi Jan,

Yes, I think something like that is happening. I have the piston just a bit lower – about 1.5mm below the exhaust port. That is where the transfer port is completely uncovered on my engine.

 

But just in case the exhaust gases are not being completely expelled, I put a vacuum cleaner on the exhaust port to extract them. It made no difference.

 

I also reduced the volume of the expansion chamber (just put tube in its place) to increase the pressure and velocity of the mixture as it is injected into the cylinder to assist scavenging. That made difference either (except that the extra pressure blew the tube off after a while).

 

My cylinder would look upside down to you because I am in the southern hemisphere where everything is upside down (as John Somers keeps reminding me) but it is the right way up for me.

 

I have now designed another poppet valve to go on the transfer port to stop any gases being drawn back into the expansion chamber. The next job is to build it and see what happens.

 

This is a very interesting problem.

 

Jim

[Jim GreetheadParticipant @jimgreethead]

I have now tried the engine with a poppet valve at the transfer port to prevent cylinder gases getting into the transfer passage and contaminating (poisoning) the incoming mixture.

 

Video of the test is here.

 

It made no difference. The engine still misfires.

 

When looking at the captured video, I noticed what appears to be condensation in the transfer tube. Further testing indicates that it appears to be oil from the bottom of the cylinder, picked up by the mixture and then deposited on the walls of the tube.

 

I don’t think this is fuel condensing out of the mixture and thus changing the ratio because heating everything with a hot air gun made no difference, and it was 30 degrees in my workshop anyway so additional heat was hardly needed.

 

That, plus the fact that the mixture remained rich as shown on the Colortune test part.

 

Jim

 

[Jim GreetheadParticipant @jimgreethead]

So that’s it. I am now giving up on this engine. I have tried everything I can think of and it still misfires and won’t run.

 

The problem is not friction because it misfires when driven by the drill.

It is not being driven too fast because it misfires at all speeds.

It is not the ball valve because it misfires with Jan’s original arrangement (on John Somers’ engine) and with Jan’s arrangement on mine and with a poppet valve instead of the ball valve.

It is not the fuel because it misfires on petrol and on Coleman fuel,

It is not the exhaust because putting a vacuum cleaner on the port to extract the burnt gases made no difference.

It is not gas contaminating the incoming mixture because the non-return valve made no difference.

It is not spark quality because it uses an RCEXL CDI system and we can see the spark in the Colortune video.

It is not mixture because we can see it firing on rich, correct and lean mixtures.

It is not compression ratio because I have tried different piston locations.

 

So I now join the others in this Forum who have given up without getting Debbie (or Sabrina which is similar) going.

 

But I will put it in a box, at least until I need to rat it for bits, in the hope that someone will solve the problem and put it on this Forum.

 

Jim

[Jeff DaymanParticipant @jeffdayman43397]

A safety note about applying vacuum cleaners to the exhaust ports of IC engines:

 

if ANY fuel/air mixture is present in the cylinder or ports and gets carried into the vacuum cleaner, there is a real chance of generating a big flame as the fuel/air mix travels over the motor brushes. In most vacuum cleaners the cleaned air passes over the motor to cool it, and often there is electrical arcing at the brushes. You might get a flamethrower out ot the deal with potentially disastrous consequences.

 

Please be very careful with all fuels and especially fuel/air mixtures around any electrical applicances.

JD

[John OlsenParticipant @johnolsen79199]

I guess this little story might add some emphasis to Jeff’s post… A school friend of mine had a habit of trying interesting and sometime hazardous experiments. So one time he built a petrol burner, which used a surface carburettor with the air being forced through it by a vacuum cleaner on blow. I never saw it going but other friends who did said it went very well. Until the day when he was showing one of my mates and forgot to put it on blow. The vacuum cleaner went up quite spectacularly, just as Jeff describes.The insurance company was very mystified, but paid up. I think one reason that I never saw it was that I was not all that keen to go near the thing at the best of times.

 

regards

John

 

 

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