The Craftmans Shop > Model Engineering

How NOT to make a model engine

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bogstandard:
This was sent to me recently, and I have only just started on the refurb of it. The customer said that he had made it, and it just would not run.

It was supposed to be a Stuart Turner twin oscillator.

http://www.stuartmodels.com/inprod_det.cfm/section/casting/mod_id/89

As soon as I stripped it down, I recognised the age old problem.
Because it would not run (caused by the ports in the main blocks being the wrong size and also in the wrong position) he did what normal people who do not know better do. He stuck the crankshaft in an electric drill and let it run for an hour, just to free it up? :bang: :bang:




Because the porting was in the wrong position, when he turned it over, instead of having a nice open to air running, it was building up pressure inside the cylinders, and putting heavy forces on the engine as it was being turned over. So effectively he has worn the engine out before it would even run by itself.

It isn't a major issue for me, everything can easily be rescued, in fact in the top right, I have already started on a new crank. But for the newbie, this engine would have to be scrapped.

Bogs

John Stevenson:
Crank main bearing hole looks badly worn John, either that or the screen want's cleaning again.  :med:

bogstandard:
John, shame on you, didn't you read my post, these are stupendous ST castings you are talking about here.

I have already cleaned it up as much as I can John, it has been reamed out to 4mm and the new crank is a perfect fit. It is because of the crap fantastic Stuart Turner, always perfect castings. The hole is in the correct position, it looks non central because the great ST castings are done like that to give them a hand made look ----- by blind chimpanzees.
:lol:

John

John Hill:

--- Quote from: Mr Bog Standard ---How NOT to make a model engine
--- End quote ---

You had me worried for a moment there John,  I thought you had sneaked a peek at my next project! :lol:

NickG:
Oh dear! How are you going to break all of this news to him gently?!  :lol:

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