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Engine basics => Engine set up tips => Topic started by: Rob Killick on August 15, 2008, 11:00:33 PM
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Hi ,
I'm looking for the size of the prop nut for a Super Tiger .46 G 21.
I don't have a thread pitch guage at home , so I'm hoping someone might let me know ?
I'm guessing it is 1/4" X 28 TPI ?
Thanks ,
Rob Killick
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Hi ,
I'm looking for the size of the prop nut for a Super Tiger .46 G 21.
I don't have a thread pitch guage at home , so I'm hoping someone might let me know ?
Thanks ,
Rob Killick
Hi Rob
the shaft is a 7mm shaft with 1/4 x 28 threads
Randy
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Aha !
Thanks Randy .
I wonder why a Standard thread on a Metric shaft size ?
Rob Killick
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I think (strictly a guess) that when the G21/.46 was released, a vast majority of all engines from .19 - .45 used the 1/4-28 thread. Note that you still have to counterbore the rear face of the prop to clear the 7mm shaft.
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Aha !
Thanks Randy .
I wonder why a Standard thread on a Metric shaft size ?
Rob Killick
HI Rob
The front ball bearing ID is 7mm, they used it on the ST 60 ST 51 and ST 56 also
Randy
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I think (strictly a guess) that when the G21/.46 was released, a vast majority of all engines from .19 - .45 used the 1/4-28 thread. Note that you still have to counterbore the rear face of the prop to clear the 7mm shaft.
Most engines (.19 to .65 or even bigger) still use a 1/4-28 prop nut. In spite of that, most engines made outside the USA also use a metric hex size, but with the 1/4-28 thread. The .46LA is an example. Reason being that the metric hex stock would be what is available (cheapest) wherever the engine is made. I don't know about everybody, but I dispose of the metric hex nuts and substitute a Grade 8 nut from a good industrial fastener supply store, with an SAE hex.
You might choose to use an adjustable wrench, or carry both metric and SAE wrenches. I don't like adjustable wrenches, or open end wrenches, and avoid them as much as possible. Besides, most folks, even engineers, don't know which direction to pull on a Crescent wrench. There is a right way, and a wrong way. I like a box-end, FWIW, and I'd actually prefer that we convert to metric. What we actually planned to do in '80's was stupid, as was what I heard the British did (55 degree thread form angle instead of 60), and the European metric threads are said to be different than Japanese. What we need is a standard, world wide. R%%%% Steve
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(Steve:) Besides, most folks, even engineers, don't know which direction to pull on a Crescent wrench. There is a right way, and a wrong way.
How correct you are Steve. There is a correct way to pull on adjustable wrenches, pipe wrenches, channel locks, water pump pliers, etc.. Just about ANY *adjustable* device, including pipe straps, will have to be *pulled* and not *pushed*.
There is usually a technique to be used (properly) with all tools (like files!), many people just never learn the techniques. ;D
Mongo
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With a "Crescent Wrench", it's not just push/pull, but how you load the movable jaw...the weak point of the design. You want to load the jaw as close as possible to it's root. You can see this easily by loosening the wrench so's it's a loose fit on a large-ish nut or bolt head. Try it, mark the point of the hex with a Sharpie, then flip it over and pull again, and mark again.
Mike Haverly and I were talking about this once. When I worked for Boeing, we had a shop edict that we would have to take our "Crescent Wrenches" home, because they were tired of their toolpost nuts and such being battered and rounded off. I talked to my Leadman and told him that I really hated Crescent wrenches, and didn't use it, but would feel nekkid without it. He said "Ok, fine, keep it." He also let me keep a lead hammer, tho we really weren't supposed to have them. Ok on most materials, but death on Titanium. Mike said that when he went to work at Boeing, they had a test to take, and one of the questions was which way to pull on a Crescent Wrench. They said he was wrong, to which he disagreed and proved his point. Turned out that an Engineer had written the test! LL~ Certainly NOT Howard or Paul. 8) Steve