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Engine basics => Engine set up tips => Topic started by: Douglas Ames on October 11, 2016, 11:41:54 AM
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So... I bought this Fox .35 off an Old Timer at our last Contest. 50's case, spade type NVA, Ranger head, all original as far as I can tell.
It has a crank with a tapered end and matching drive washer, Never seen that before so I'm wondering if this an early Combat Special, production variation, or aftermarket crank?? Also, there are lightening cuts on the crank disc, another oddity? Pics below...thoughts?
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I dug out the early Fox 35 I have, which fortunately is still disassembled. The crank has the tapered front end but the crank disk is fully circular. I understand a mod to help balance this beloved engine a bit better is to cut away the disk as shown on your crankshaft. In fact, I think there are pictures here somewhere of a stunt crank with black lines added to the pics to show where one can safely grind away a few grams. Most likely a previous owner did this.
Bob in NEPA
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Doug,
The early 4 bolt sand cast Fox 35's and 29'S had the tapper shaft and drive washer.
Best, Dennis
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Love the surface finish on that taper, classic Fox.
MM
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Love the surface finish on that taper, classic Fox.
MM
It might have looked a little nicer the day it was made, ~ 50 years ago ;D
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Love the surface finish on that taper, classic Fox.
MM
Looks a little Galled, huh? lol
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It does look like there was some slippage there. Loose prop or prop strike with a Top Flight nylon maybe.
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It may have been galled deliberately. The drive washer would often slip on the crankshaft taper making it hard to tighten the prop. Some people would rough up the taper (like Doug's crankshaft) or put dirt on the taper to prevent slippage.
Remember, this was back in the day when the Fox .35 was the best engine out there. Slippage was a small problem.
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Guys,
I was going through my box of Fox 35 parts last night getting ready to do some work on the motor mount for my new Barnstormer and came across a crankshaft the had a full counter weight with no relief. Comparing it to several other cranks I have the others have the counter weight shaved backward on the front edge. This one is a square edge to the weight area, it is a couple grams heavier. I know some of the combat guys would modify the K&B's by shaving the area coming out of the shaft intake bore to get smoother flow through the engine and hoping for more power. Not sure which design is the latest. Anyone know when this design shaft was incorporated into the Fox 35?
Best, DennisT
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I knew a guy who had a friend that worked in the factory. He said some of the stuff that would get let out the door wasn't made right.