Jan Ridder's simple two stroke

[bentprop]

I started on this engine last year,before earthquakes interrupted my hobbies.
Made some progress in the last two weeks,and here are a few pics of various parts:

The cylinder is supposed to be cast iron,but I didn't have any,so I used a piece of unknown steel.The piston is cast iron,and this is my second.A "senior moment" on the handwheel made the 1st one too small.

Con rod and fork.The fork is my second,as the first one had a wobbly thread.

Exhaust muffler and manifold.

Crankshaft parts.The shaft looks bent,but that's just an illusion.It's a piece of 10mm shaft out of an old photocopier.The disc is supposed to be silver soldered on,but I'm worried this will distort the shaft.I'm therefore going to fit the disc with Loctite,and pin it to the shaft.

The uprights in the raw,with bearings.I'm still deciding how to bore the recesses for the bearings,as I don't have a boring head.I might have to drag the face plate out of the cupboard,and give that a workout.I've never used it,so that would be a new experience.

There's a flywheel in there somewhere ;D
Jan's instructions give no circuit for the ignition,so if anyone has built this engine,I would be grateful for a crap-o-cad drawing of it.I'm using a 12mm lawnmower spark plug,as I couldn't find any teflon at the time to make one.
Oddly enough,someone pointed me in the right direction and I now have some.
Now to fill the swarf bucket with the remains from that hunk of steel that will become the flywheel.
More pics in due course.

 

[kjk]

If it's "debbie" you are building, John Somers at start model engineering may have some insights.

http://start-model-engineering.co.uk/category/jan-ridders-simple-two-stroke/

 

[JohnS]

Hello BP

I have just completed a build of Jan Ridders' simple two stroke though at times it felt far from simple. It took me two months to build and another two to get it running !
It seems I am not alone in having problems and I know there are several people who gave up. My problems were successfully overcome by increasing compression thanks to experimentation by friend Aussie Jim.
The build of my 'Debbie' is detailed on my blog and website
http://start-model-engineering.co.uk
including details of both coil and CDI ignition systems - both installation and setup. There are also details of a modified piston and cylinder head which proved successful in overcoming my starting difficulties. Please feel free to contact me if you think I may be able to assist.
Good luck
John-Som

 

[bentprop]

Thanks for your thoughts,John.Looks like all's not as simple as the title would suggest.I'll keep your mods in mind.
Actually,I might modify the head before I put it together.The way I see it,if I take something off the outer mating surface of the head,that would give me the increased compression,without having to redo the whole head,correct?
How much did you reduce the inner section?
I see on Jan's video that his flywheel has more holes than a Swiss cheese.I would have thought lightening the flywheel would have a negative effect on the ability of the engine to keep running.I'll try it with the standard one first.
I've bookmarked your site,so I can keep up with your developments.
regards,Hans.

 

[JohnS]

Hello Hans

Your suggestion to increase compression by taking material off the mating surface of the head would no doubt help. In my case so that I could return to original spec I made a second head and reduced the cavity by 2mm, I also took the opportunity to lower the spark plug deeper into the combustion area.

The other mod was to make another piston without the 3mm shamfer around the top and in its place I machined a transfer guide about 5mm wide and coming down the piston about 4mm. The piston was then set so that the crown was aprox 2.5mm from the top of the cylinder. This should give port openings of 100 degrees about BDC for the transfer port, and 120 degrees for the exhaust as recommended by 2 stroke guru Dave Parkes. You should have very noticeable 'bounce' as the piston approaches TDC.

You may also find that your engine will be sensitive to fuel level in the vapour carb.

I shouldn't be too concerned about the number of holes, or lack of, in the flywheel. Diameter has much more influence than weight. Incidentally many experiments were carried out with lighter v heavier flywheels to see if the running problems were in that area.

John

 

[bentprop]

A little update on my progress(or lack of it :big
The crankshaft assembled:

The crank disc is loctited and pinned to the shaft.
Crankshaft pulley and spacer:

The eccentric being milled on the rotary table:

The finished eccentric:

And fixed to the flywheel with 3mm hex bolts;

Milling the crank supports.

One of the very few times I actually had a use for the swivel base supplied with the vise.Normally it's not used,to increase the space under the head.:

Because I only have a 6' ceiling in my workshop,I can't raise the head on the mill very high.This is a problem when using the rotary table with the 3-jaw mounted on top of it,not giving me enough working clearance.I intend to remedy this by cutting a hole in the ceiling,and making a sort of "cubby hole" above the mill,to allow me to raise the head high enough.One of these days.........

 

[AussieJimG]

Hi Hans,
Here is my version of the Simple Two Stroke: [ame]http://www.youtube.com/user/AussieJimG#p/a/u/1/o-zo52flDbI[/ame]
I used an NGK CM6 spark plug and an RCEXL CDI ignition system with the magnet carrier on the crankshaft and the Hall Effect device embedded in one of the bearing standards (easier because I was too lazy to cut out the fancy one). I will try to post phots of the setup. Sorry, posting the images didn't work - I need to find out how to do that.
Jim