stunthanger.com
Engine basics => Engine set up tips => Topic started by: frank mccune on February 08, 2022, 04:17:30 PM
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Has this ever happened to you? It just happened to me for the first time.
If anybody is interested in the details, let me know.
Frank
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What engine are you running that has a pressed in crankpin? Most production engines (and I think all modern production engines, but who knows?) have a crankshaft that's machined out of one piece of steel.
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I have at least 3 engines with a pressed in crankpin (maybe more but it's not something I usually look for). A K&B 40 series 70 rear disc, K&B 15 series 72 and a Taipan 15 gold head. What G Burford used to do was buy boxes of individual roller bearings for his crankpins. The K&B 15 had two different crankpins, the first type was hollow but apparently were prone to breaking so the later ones had a solid crankpin. I have examples of both where the serial number for the hollow pin starts with A**** while the solid starts with B***** however the A is the CL version while the B is RC but no one seems to know what the A or B indicates.
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What G Burford used to do was buy boxes of individual roller bearings for his crankpins.
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Numbered drill bits will work too.
Al
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About 60 years ago, I had a couple of K&B "Series '61" .35's that had pressed-in crankpins. These engines often broke the crank at the front bearing, sending the prop driver/prop off into the boonies. Of course, they kept running for a short while, sometimes eating the post in the cylinder and often working the crankpin out to where it gouged into the backplate. The aluminum passing through the running engine kills the glowplug and eventually the engine stops. All this destruction seemed to follow a relatively normal combat match prang.
I must add that K&B was always good about repairing these engines for free. I don't think I ever had one of them "broken-in" before it was just plain broken. While they ran, they were pretty amazing engines, as I ran only K&B 100 fuel and they were fast with a 9-8 Tornado nylon. Not many combat engines would pull a full 9-8 on low nitro fuel. My ST .35C would do it on 50% nitro, but also never broke, and eventually wore out. y1 Steve