Don Terrill’s Speed-Talk

piston guy wrote: ↑Thu Jun 18, 2020 4:48 pmThe lock "fragmenting" or inertia making it "saw" through the pin itself. Neither of which is good.

Agree, putting a spirolox in an application for which it was never designed could result in many unanticipated consequences.
However, given the miniscule weight, the inertial forces a spirolox could generate are pretty small and I just had to shorten some piston pins. Even with a industrial CNC lathe and the best tool inserts money can buy, it was a difficult operation. I'd bet a bunch the spirolox aren't going to saw through a piston pin.
Also agree, I'm not going to use them instead of spacers.

I have seen fragments of broken Spirolocks saw through piston rings on both sides of a piston since it was able to go to the other side through the hole in the pin. The "band" below the pin kept it captive and it stayed there "hammering" its way around until the engine began smoking. Inertia at 8,000 rpm makes the fragment "heavy" enough to do serious damage.

I thought that the big advantages to piston guided was the short very stiff, very light pin along with very stiff highly reinforced piston design.

Adding spacers doesn’t seem to take advantage of these benefits....

"I have never used or worked on an engine made with guided pin spacers. I never understood the reason or advantage for using them. Could some of the high end engine builders explain to me why they are sometimes used?"



I am guessing that you have never had experiences with 2,000+ horsepower engines where the crankshaft actually gets shorter from deflection at higher RPM.

Who makes them...
Guys who have a lathe.