5 cyl OHC Radial.

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josodl1953

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Peter,
So far I found no adverse running effects of the equally-spaced link rod pins in the master rod. The drawing of the cylinder liner ( the Robert Sigler version) specifies trimming of the liner top to achieve equal CR for all cylinders.
cilinder afdraaien.jpg

I myself adjusted the CR by trimming the piston crowns to the correct height because in case of an error is is easier for me to make a new piston than to go through the elaborate and messy process of making a new liner.
As far as the spark ignition of the original Edwards is concerned: I found proof on the website of the Miniature Engineering Museum Collection that the original Edwards did have spark ignition. I wonder whether Forest made corrections on the position of the link rod pins or that he kept the equally spacing.
originele  edwards.jpg

Either way, it seems worthwile to investigate how the linkrod configuration was arranged in "real " radial engines.
 

Peter Twissell

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Arguably, we are all building real engines.
Radial engines which we may consider to be full size would normally have relatively long slave rods relative to the pcd of the eyes on the matter rod, so the effect of the angles between those eyes would be less pronounced.
It is quite possible to correct ignition timing to match irregular tdc positions by manufacturing magnetos with irregularly spaced points cams.
 

petertha

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I seem to recall Carl's spreadsheet also calculated relative link rod angles through the motion range. I cant remember if the 'equalized compression ratio' (compensated) layout geometry on the master rod made it slightly better or worse when it comes to link rod angles, specifically potentially interfering with the base of the liner skirt. That's another design consideration over & above the basic layout. Sometimes you see notches in the liner bottom end or the rods sections are minimized, particularly the long strokers. Another example where model & full size engines may not scale to one another in certain respects.

That's a good point about matching non-equal ignition timing requirements on the distributor or equivalent.
 

Peter Twissell

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My engine has equalised timing, which creates high rod angles on the cylinders opposite the master rod. I have created clearance in the barrel skirts for the rods.
 

xpylonracer

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When I built my Radian I was not aware of any such problems until I was checking clearances on final assembly, I used shims between the liner and head to provide equal CR to each cylinder but did nothing to correct timing of TDC.
 

Brian40

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Simms motor units produced corrected magneto's for radial engines , unfortunately it was all finished when I joined the diesel development lab a long long time ago.
Brian.
 
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