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Two stroke cylinder casting.

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Tjark:
Jo, the cylinders I am working on will be for a racing moped.
Over here are two moped engines very popular and these are the Minarelli AM6 and the Aprilia.
A friend of me is competing in this class with a Minarelli AM6 for hobby.
He’s not driving all the races, only those close to his home.
He also is 15 years to old and minimal 15Kg to heavy.
But in all the races he drove this year he finest in the top 5.
So for next year we will try to make a new cylinder with a different transferport and exhaust  shape.
The core boxes for the transfers and exhaust are ready and tested, see the pictures
Now the boost ports and water jacket are in progress as the outside.

  Tjark.

lohring:
Hi Tjark
Have you considered Calvin's method of making cores?  He calls them spider cores and would seem to be better at maintaining the relationship between the transfers and the cylinder bore.

Lohring Miller

Tjark:
Hello Lohring,

I have considered this way off working.
It shure gives always the good shape off the transfer ports in relation to the bore.
But it’s not as simple as it looks to make this.
I have my self no CNC machinery.
A friend of my has but then you have to draw this in 3D and convert this to a step file.
For me also not easy.
I make them now with some help of some original ports what I fill with melting rubber, then change the shape I think will work better and make some core mold’s by poring the melting rubber port shape’s in a couple of pieces with a polyurethane.
I am not planning to make great series off them so this will do I think.
Maybe I get some better ideas for this problem  in the coming time, whe will see.
Get these days a lot off ideas from professional molds, because  I am casting a lot off parts for a professional engine builder these days to generate  some pocket money for the hobby.

  Tjark.

lohring:
I'm also working (very slowly) on two stroke cylinders.  I also have only manual machines.  My plan was to build a model of the cylinder with separate sections at the transfer and exhaust port heights.  It could be assembled then the passage shapes could be modeled in clay.  After disassembling the parts again they could be used as the male plug with the passages attached for the core box mold.  I have done a little lost foam and sand casting in my foundry but planned to use lost wax investment casting for my cylinders.  They are only 26 cc, smaller than yours.  My cores would be soluble wax that's dissolved out before investing the cylinder.

Lohring Miller

Tjark:
I am working also on a water cooled  version of  Zenoah cylinder with a friend of me.
The problems with those cylinders is the base and the transfer port shape.
This is how we look at it at the moment.
I would like to make the transfer passage in the same shape as for the 50cc cylinders.
The bolds to connect the cylinder to the crankcase I would like to put inside the water cooling jacket.
This way the cylinder will not crack at the base, this is what I have often seen with the originals.
The pattern making is an issue where I am struggling with, the outside patterns are no problem but making the pattern  for the core’s are difficult for me.
This year I got some help from a professional  German   pattern maker, and this gives a big relieve.
The only problem is that I do not see him that often so progress is going slow.
But at the end we will getting there.
The casting I do is always in oil bonded   sand with SS core’s.
I think for the small Zenoah cylinders this will also be no trouble.

   Tjark.

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