Is anyone interested in developping a new series of model engines?

[JasonBModerator @jasonb]

I think most people would put up with a few minor cosmetic defects provided the part was usable and only needed a reasonable amount of clean up not completely machining all over. The main issues that are not wanted are unmachinable hard castings, excessive mould shift particularly on smaller castings, undersize castings and blow holes where they are not sorted with a bit of filler such as flywheel rims and cylinder bores.

I think what got me into building from scratch was having to create parts for engines where the castings were pants, that group of small ones was from quite early in my building journey but I actually enjoyed the research as to what the parts should look like, designing them at a scale to suit the engine and then making them.

I’m sure some engines get started and then put under the bench when a builder looses heart due to problems. This engine I’m working on at the moment is 2nd or 3rd hand. Originally I was asked to tidy up the cylinder casting and machine the flywheels as the owner could not fit them on their lathe. You can see in the past someone gas tried to get a few flat surfaces so it could be held in the 4-jaw for boring. There is some quite bad shrinkage particularly on teh top right.

Some might be happy to leave it with the wonky cast surface which was 2.5mm low in places but thats not for me so it was machined all over

The bore still has more pock marks than the earlier mentioned spotty teens, the long 3/16″ for the valve steams have wanderd and the pockets for the valve seats are not concentric to those holes, taper, wrong depth and wrong diameter no matter what depth you measure them at. The 4 holes with counterbores are all off too.

Depending on what that casting might have cost if it is going to need so much work externally then there is a good argument for starting with a solid block. Not only can the exterior be made to look half decent you won’t have voids to spoil the bore of deflect the drill when doing the long deep holes. It will also be cheaper based on todays costs for solid and what I would likely pay for a casting and that does not include pattern work.

You will be pleased to know I have worked my magic on it and did a temporary lash up to check there was life in it.

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