ORIGINAL: Kostas1
ORIGINAL:
canardlover
Hello again, another update on the Saito CR increase and some more ''swiss cheesing''..
Recently bought a Saito .72 GK in good shape and as usual I could not resist to take it apart for a closer inspection. Everything was in good order except that it was equipped with the early plastic rear crankcase cover which is rather flimsy. So I bought a new reinforced cover and gave my usual ''swiss cheese'' treatment and milling of the crankcase to take off 0.8mm for an increase in CR.
This time I went a bit further in my lightening of the conrod. I drilled four holes each 4.2mm dia. which is more than ever before..[X(]....!! See pic of the setup and wish me luck, testing it very soon...Thank you..!
As far as the conrod holes are concerned,
don't you think that you threw away some of the
stifness and
rigidity;
Kostas, you are absolutely correct that both stiffness and rigidity must suffer when you take away material from the conrod like this. However, I think the gains in power and sweet running is worth the risk of a potential failure. The more "classical" way of lightening a conrod is to make it into an I-beam by milling rather than drilling. See three examples where the original weight is reduced to 90%(Enya.60 4S) and 85%(Saito.56) and then the Saito.72 GK conrod at 83% after the much simpler drilling excersize. The material in these conrods is so very hard that my simple milling equipment can hardly cope with it - thus my risktaking to just drill them out.
I can honestly say that I was a bit nervous when I first fired up this Saito.72 GK and gave it full bore....[X(]...! Well, worst case would be that the broken conrod would poke a hole in the crankcase...[:@]..but second hand glow engines are cheap these days...
. OK, a dead stick landing may be added to this scenario....[:'(]...but then at least I will know for sure that 4 x 4.2mm is too much and back off a bit next time(or buy a better milling machine..
)