your mail

Roy Alan Oxlade spectric at globalnet.co.uk
Sat Feb 28 20:05:31 GMT 1998


Roy says

Most con rod failures occur on the exhaust stroke, under conditions of combustion
or compression  the rod is under compressive stress wheras on exhaust it is
tensional stress.  Bolt failures also occur normally on tensile loadings not
compresive.

Jim Davies wrote:

> On Mon, 23 Feb 1998, Christopher E. Hill wrote:
>
> >       I am sorry if I have caused any confusion.  Yes, the pressure due to
> > combustion does produce a stress on the conecting rods.  However, the
> > stress due to rpm on the rod I feel is higher than that of combustion.  I
> > have not done the actual math to prove this, just using my common sense, as
> > I have never seen a rod broken under normal cicumstances(i.e. lacking
> > SEVERE detonation) but have seen some come appart at high rpms.
>
> The last SAE paper I saw on this subject showed the load at TDC exhaust to
> be far higher than any other load on the rod, including the power stroke.
> I have read of Allison rods breaking from detonation related problems,
> which could become severe enough to push crankshafts out of the block, but
> these were highly loaded, very highly supercharged engines using 150PN
> gasoline. We are not going to see similar cylinder pressures with the
> fuels currently available.
>
> Jim Davies






More information about the Diy_efi mailing list