"Topsy" 0.375c.c. compression ignition engine

[GailInNM]

RR17,
The Topsy has such a long front bearing that there should be no need to lap them, but because it is a front rotary valve a good fit will be necessary. On my small engines, I turn the crankshaft a few "tenths" oversize and then polish to size with 600,800,1000,1200 abrasive paper in order with a drop of oil. I back the paper with a piece of ground steel like a parallel. This will not take out all the machining valleys, but will smooth out the hills to give more of a bearing surface.

Nice work on the Topsy. The way you are going it will be a fine engine.

Gail in NM,USA

 

[roadrage17]

Thanks For the reply GailInNM very useful and i will put it to use in this project of mine

Best regards

RR17

 

[roadrage17]

more progress . Bored out and screw cut for the fuel tank to screw in . and also pressed the main bearing in .

Best regards RR17

 

[roadrage17]

There are some problems im having though because of the size of the engine i cant use a boaring bar, i tried to grind one up but it just chattered to much. For example to do the main bearing i would of idealy boared it near size then ream it out. instead im having to use a drill then ream it, But the drills are wondering! So im doing the best i can. Next Engine BIGGER lol. Like the one your doing sean.

Best regards RR17

 

[Seanol]

RR17,
As long as you use aluminum you will be fine. Ti is for the birds!

Sean

 

[roadrage17]

Yeah point taked Sean ,

Regards RR17

 

[DavesWimshurst]

RR17,
The chatter problem and crooked drilling problems can be alleviated by using D bit reamers as described recently: http://www.homemodelenginemachinist.com/index.php?topic=5251.0
The D bit should make a straighter hole which could be reamed with a standard machine reamer if the D bit doesn't give a smooth enough finish. Adjust shaft size to suit.
Hope this helps.
Dave

 

[roadrage17]

heey guys quick update ive looked more closely over the drawings and ive found out im missing quite a few dimensions on the cylinder, and few other things. So for now the project on hold till i get some more.

However on a brighter note ive got some drawings from hom shop machinist i think it is, and the engine called "Alpha". Ill get some pics up have started the crankcase so far.

Best regards RR17

 

[Seanol]

RR17,
Sorry to hear about the Topsy, I was looking forward to it. Can't wait to see the new "Alpha" project!

Looking forward to it,
Sean