Another Knucklehead, built via castings, as a Draw-Tech design, upscaled

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Foketry

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After seeing the construction done by Mayhugh, I also decided to build this interesting engine in a slightly larger scale.
The pistons of my engine will be 36 mm instead of 1.063 inch (27mm) and everything else will consequently be increased by the same proportion.
I have followed and studied all of Terry's posts, whose technique and precision I admire and I hope to obtain a well-functioning engine like his.
I also asked Terry for some 3D drawings and he kindly provided me with some ,I started from these drawings
After the 18-cylinder Isotta Fraschini, I returned to simpler engines, just 2 cylinders, even if Terry writes that it is not that simple
 
To make aluminum castings the first step is the 3D drawing of the finished part, then I eliminate all the holes and machining, add the allowance in the milled or turned areas, add an increase that takes into account the aluminum shrinkage .


Finished right crankcase


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drawing for casting mold

Carter destro fusione.jpg


3D printed mold with parting powder

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I generally paint the mold to obtain smoother surfaces but in this one I didn't paint

the sandblasted casting

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The crankshaft

My Knucklehead engine is larger than the Draw Tech project, the diameter of my piston is 36mm compared to 27 mm, 1.33 larger , so everything will be larger than the photos of the components that you have already seen in other constructions. The total displacement of the engine will be 90 cc, therefore all the components that you have already seen in other construction photos will be larger.

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I built the flywheels separate from the shaft that carries the bearings, I thus avoided turning many kg of steel and generating mountains of shavings

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I turned on the lathe and drilled the 2 flywheels together, then separated them with the band saw, to obtain the central hole and the hole for the connecting rod pin perfectly equal and aligned.

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I made the tapered holes for the rod pin with a Morse 1 tapered reamer

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the 2 flywheel shafts have an allowance of 0.5 mm, when they are assembled with the flywhee , connecting rods and the pin , I will do a final turning to ensure alignment and concentricity .
The assembly was done with a press.


CNC turning of the connecting rod pin

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the defective pins, 5 before getting the correct one

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oil quenching of the connecting rod pin
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Before you assemble you might consider a needle bearing on the con rod, I did it on my Hoglet and it seems pretty good. Also I drilled and reamed a hole at 180 degrees from the con rod hole to insert a dowel when aligning the flywheels, seemed useful.
 
Before you assemble you might consider a needle bearing on the con rod, I did it on my Hoglet and it seems pretty good. Also I drilled and reamed a hole at 180 degrees from the con rod hole to insert a dowel when aligning the flywheels, seemed useful.
For the connecting rods I provided bronze bushings, mechanically the needle bearing are better, they have less friction, but the bushings are simpler and more robust.
 
The cylinders
Terry who has already built this engine suggested lengthening the cylinders, to be more similar to the original.
In this drawing the black part at the top is the elongated part compared to the Draw Tech project ,of course I also had to lengthen the connecting rods by the same amount .


SPRUT Cylinder FIN Model .jpg


the first stages of turning


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the two rough-cut cylinders were separated with the band saw

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milling and drilling of the flange

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Head fixing holes

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milling slots for screws

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Milling equipment built with a 3D printer



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the cylinders after bluing

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Once you use one, there is no going back. Unless you down Z the thing onto your part and the ruby ball dismantles itself rapidly (I would never do that).
Also, a tool touch pad is awesome for tool changes, it takes care of the Z offset for you.
 

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