# "Bouncing" 2-stroke model engine



## Jan Ridders (Dec 15, 2012)

Hi all interested,
I designed and made an absolute silly but unique 2-stroke model engine. The fly wheel and crank shaft are absent and are replaced by a only a steel weight, hanging on the piston. This weight pulls the piston downwards making the compression in the glass cylinder below the piston. The combustion of the gas mix below the piston pushes it upwards again with what the sucked-in fresh gas mix above the piston is flushed via two one-way ball valves through the combustion chamber below the piston so the process repeats itself; see the video:
[ame]http://www.youtube.com/watch?v=bumwz7kvjtQ&list=UUOWqwLEIfORZB09qQirdkag&index=1[/ame]
You can see and read all about it on my web site; page:
http://heetgasmodelbouw.ridders.nu/Webpaginas/pagina_stuiter_2_takt/stuiter_2_takt_frameset.htm
I will make some optimizations coming weeks and then make the final version with a new video, the description on my website and the drawing plan.
Friendly greetings from Holland,
Jan Ridders


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http://www.youtube.com/watch?v=bumwz7kvjtQ&list=UUOWqwLEIfORZB09qQirdkag&index=1
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## aonemarine (Dec 15, 2012)

upon first glance I didnt think this engine would run.....but it does!!! and runs well. shows what I know....


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## Cogsy (Dec 15, 2012)

Another excellent design. I'll definitely be adding this to my build list.


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## Herbiev (Dec 15, 2012)

Hi Jan. this engine you call silly is also beautiful and unique. It is really a work of art. Congratulations on another great design and many thanks for taking the time to post it


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## nemoc (Dec 17, 2012)

Hi Jan,  I really like this engine.  Runs great! Thm:  I have never seen anything like it.

Craig


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## mu38&Bg# (Dec 17, 2012)

This design is called a free piston engine. They were often used for air compressors where there is a second cylinder that compressed the air. There are also generator designs using this idea. Great execution and finish as usual.


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## myrickman (Dec 20, 2012)

Jan- very neat free-piston engine! Top shelf on the planning, fabrication and video documentation. MM


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## nemoc (Dec 20, 2012)

Thanks Greg,  I googled it and found some great stuff.

Craig


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## te_gui (Dec 20, 2012)

A friend has a Barco tamper that works off the same idea. the piston is inline and attached to the tamping foot and the cylinder floats. You pull the cylinder housing up and then down, the mag gets flicked and the whole thing jumps into the air.


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## Jan Ridders (Dec 22, 2012)

Hello,
Thank you all for your positive comments. I just implemented some significant improvements and the engine is running perfect now. I will revise the text on the concerning page on my website and show the results with a video some of these days, here and on my web site http://ridders.nu
Friendly greetings and a Merry Christmas and a Happy New Year to you all.
From Holland,
Jan Ridders


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## AussieJimG (Dec 22, 2012)

Another piece of moving jewellery! Thanks Jan and Merry Xmas to you.

Jim


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## Jan Ridders (Dec 25, 2012)

Hi all
I made an improved MK2 version of the Bouncing 2-stroke engine; see the new video:
[ame]http://www.youtube.com/watch?v=tYvBBTREuCk&list=UUOWqwLEIfORZB09qQirdkag&index=1[/ame]
Also because I got a lot of comments, questions and suggestions about the first version  I revised the whole text on the concerning page on my web site:
http://heetgasmodelbouw.ridders.nu/Webpaginas/pagina_stuiter_2_takt/stuiter_2_takt_frameset.htm
There you can read and see more details about the principle, my experiments and the final results.
I wish you all a Merry Christmas and a Happy New Year.
Jan Ridders


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## Jan Ridders (Jan 14, 2013)

Hi all,
I just finished the plans for the "Bouncing 2-stroke engine".
Available via my web site; page:
http://heetgasmodelbouw.ridders.nu/Webpaginas/pagina_stuiter_2_takt/stuiter_2_ta\
kt_frameset.htm
See also the video of the final version:
[ame="http://www.youtube.com/watch?v=tYvBBTREuCk&list=UUOWqwLEIfORZB09qQirdkag&index=1"]http://www.youtube.com/watch?v=tYvBBTREuCk&list=UUOWqwLEIfORZB09qQirdkag&index=1[/ame]
Friendly greetings from Holland,
Jan Ridders


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## Jan Ridders (Jan 14, 2013)

Hi all interested,
I just finished the plans for the "Bouncing 2-stroke engine".
Available via my web site; page:
http://heetgasmodelbouw.ridders.nu/Webpaginas/pagina_stuiter_2_takt/stuiter_2_ta\
kt_frameset.htm
See also the video of the final version:
[ame="http://www.youtube.com/watch?v=tYvBBTREuCk&list=UUOWqwLEIfORZB09qQirdkag&index=1"]http://www.youtube.com/watch?v=tYvBBTREuCk&list=UUOWqwLEIfORZB09qQirdkag&index=1[/ame]
Friendly greetings from Holland,
Jan Ridders


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## canadianhorsepower (Jan 14, 2013)

I'm speechless


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## cfellows (Jan 14, 2013)

Jan, you've provided many interesting projects and solved a lot of problems for the rest of us model engine builders and I would like to thank you for all the contributions you've made.  

This one is very interesting to me because some of the 2-stroke innovations you've made might prove valuable in the 2 stroke Bessemer model engine I'm trying to design.  I'm curious about the expansion vessel.  How did you determine the need for it and did you try different sizes?

Thanks for all you've done...
Chuck


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## Jan Ridders (Jan 14, 2013)

Hello Chuck,
If the piston is compressing the fresh sucked-in gas mix from the carburetor the pressure of it will counteract the piston movement. Without an expansion vessel this pressure can be so high that the engine runs bad or even not at all. The expansion vessel acts like the crankcase of a normak 2-stroke engine in what the gas mix is compressed to the right pressure. To find out the optimal size of the vessel I connected a rather long silicon rubber hose instead of the vessel that I could squeeze on various places and I determined when the engine behavior was best. In this case it turned out to be about 10 cc, but it is not that critical; +/- 20 % will be OK also.
Thanks for your reaction and  nice words,
Jan Ridders


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## aarggh (Feb 2, 2013)

That is simply amazing, what I wouldn't give to see one up close!

cheers, Ian


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## Scooterseats (Feb 21, 2013)

This concept reminds me of a gas powered Pogo Stick that I saw once.  It was galled a "Hop Rod" I believe.  I always wanted to try it out but it was on display in a store in a small town in Oklahoma.


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## cncjunior (Feb 21, 2013)

Hi Jan, 
This is amazing in elegance and style.  I like how you incorporate glass into your designs.  A group of use made one of your Stirling engines spearheaded by someone you have been in contact with kbcustom on youtube.  With glass you can see the workings of the engine which is one of the reasons I like steam engines with all the visible whirling parts.  Thank you.

Daniel


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## cncjunior (Feb 21, 2013)

Hi Jan,
I was just on your web site and reading about your evolution in this engine.  You mentioned that the engine runs for about 2 minutes or so at best.  I may have misunderstood this part.  When I watched your video you showed the petrol tank bubbling.  I think that this indicates what the problem is.  The engine sucks the petrol fumes out and through the carburetor.  Looks like the tank has created a vacuum in it.  Liquids will boil when under a vacuum.  I haven't looked at the tank drawing itself to see if there is a small air make up vent.  Like I said I may have misunderstood the problem.

Daniel


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## AlanHaisley (Feb 21, 2013)

Jan,
This is a fascinating engine. One point of interest is the cycle time. I would expect this to be somehow related to the mass of the moving parts rather than their weight. It seems to me that the mass can't really be decreased since you need the weight to make the compression cycle what it is.
It could be increased while maintaining the same weight though in one of two ways: either tilt the mechanism so that a larger mass would give the same resultant weight or add a bellcrank linkage to an additional mass configured to slide horizontally on some kind of linear bearing.
This might provide a means to operate the engine slower with reliability.
I wish I could visualize a way that might make it cycle faster.
Alan Haisley


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## Jan Ridders (Feb 22, 2013)

Hello Alan,
Indeed the cycle time is related (determined) by the system mass. But weight is the same as mass in the sense that weight is the gravity force on the mass, isn't it?
To be honest I don't understand the rest of your remarks, but it could be interesting anyhow if I should.

Thanks for your reacton.
Jan Ridders


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## Rivergypsy (Feb 22, 2013)

Yet another lovely engine, Jan 

Scooterseats - there was a guy where I used to work who built a two-stroke pogo stick, but I hadn't realised there was more than one. This was the same guy who built a mini rocket engine, which made enough power to slam a 6 foot heavy iron welding bench against the nearest wall - slightly 'eccentric'


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