Paddleduck cylinder bore query

[Andrew EvansParticipant @andrewevans67134]

Hello all – any advice would be much appreciated. I am making Bogstandard’s paddle duck engine, remaking the main cylinder block at the moment using brass rather than CI. My question is for the 2 10mm cylinder bores I cannot decide whether to bore with a boring head in my Cnc milling machine or use the nearest sized reamer I have which is 3/8″ (9.5mm). Is reducing the cylinder diameter going to have much effect on the running of the engine? If I do use the boring head can anyone give any tips – I always struggle to get the bar rotated in the right way and the head lined up with the drilled hole – if that makes sense?

The main reason I am remaking it is that the cast iron off-cut I found proved to be full of inclusions and really hard. The surface quality of the bores was too rough I decided and no end of honing and polishing seemed enough. Went for brass instead.

Thanks in advance. Andy

[Andrew EvansParticipant @andrewevans67134]

[BogstandardParticipant @bogstandard]

Andrew,

 

I designed this engine so that you can do what you suggest, change sizes or materials to suit what you have available.

 

Brass will be fine for the cylinder, as will your 3/8″ reamer.

All you will need to do is to resize the pistons, top cylinder cover and gland end cover to suit the bore.

 

The engine will run fine with with the new sizes.

 

Hope this helps

 

 

John

 

[Andrew EvansParticipant @andrewevans67134]

Many thanks John. I have used a drill and honing to finish the bores now and they seem fine.

Can I also say that I really appreciate the effort you went to to produce the book originally – for someone lIke me it’s invaluable.

Andy

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