[SEL] Question re tapered gib keys

[David Rotigel]

Good doG Jerry, Think outside the gib key. Drill and tap a hole in the  
flywheel hub 90 degrees off the key slot and put a grade 8 bolt in it  
to tighten the flywheel to the crank!
	Dave
PS, "The welder did a great job" and it lasted 3 rallies? Could I have  
the name of the guy please. I know it's a long way away, but I still  
have to know who to avoid!
PPS, Arnie tells me that cats tast like rattelsnake!

On Sep 14, 2009, at 2:55 PM, Jerry Evans wrote:

> Hi to the knowledge base (that's all you guys out there in  
> engineland) :-)
>
>         A few questions re tapered "Gib Keys" but first I'll explain  
> the
> problem - this may be a bit long winded!
>
>         The flywheel on my little Ronnie N keeps coming loose. (To be
> fair, Arnie did warn me that, if I called him Reggie I should expect
> trouble :-)).
> <http://www.oldengine.org/members/evans/reggie/index.htm>
>
>         After restoration (and a few "rallies") he developed a knock
> (which sounded just like a bearing knock) and I discovered that the
> flywheel was loose. Closer inspection revealed a crack in the  
> flywheel hub
> starting in one corner of the keyway and going to the outer edge of  
> the
> hub. (A common problem with them, I believe, related to incorrect  
> removal
> of the flywheel).
>         I had the hub machined (just a tad) to fit a reinforcing steel
> ring around the outside of it and had the whole lot professionally  
> welded.
> This welding was done with a mandrel (sp) a few thou smaller than the
> crankshaft inserted and clamped up with the bolt to prevent  
> distortion.
>
>          The welders did a great job and it worked fine for 3  
> rallies but
> then the knock (and loose flywheel) started again although the crack  
> has
> not reappeared - the repair has held.
>         The flywheel is cast with a teardrop shaped slot (opposite the
> keyway) into the web of the flywheel and going "all the way through"  
> to the
> crankshaft.
>         Fitting entails sliding the flywheel onto the crankshaft,  
> lining
> up the keyway on flywheel and crankshaft, fitting a straight key,  
> and then
> tightening a large bolt which theoretically clamps the flywheel to the
> shaft - the key just there to locate it and prevent the flywheel  
> slipping
> around the crankshaft.
>         Removal entails loosening the large bolt and inserting a wedge
> into the teardrop shaped slot (from the back) and knocking it in just
> enough to loosen it (the flywheel) from the crankshaft. This is  
> where the
> damage "happens" if done incorrectly ie. wedge hammered in too far  
> causes
> the crack on the opposite side of the hub (in the corner of the keyway
> which is a "weak spot").
>
>         The repair has held (as mentioned earlier) but now I'm  
> wondering
> if a tapered gib key is not the answer. (I wonder why the  
> manufacturers
> never used that system in the first place as it seems infinitely  
> better
> than what they did but it was 1936 and the design was even earlier  
> so maybe
> that will explain why they went that way).
>
>         O.K. that covers the explanation of the problem - now my  
> questions?
>
>         a) What do you guys think of the idea of a tapered key to  
> replace
> the straight key - I would knock it in very slightly first - then  
> tighten
> the clamping bolt as tight as possible - - then give the tapered key a
> whack to seat it - after a few "runs" of the engine maybe another  
> whack?
> (ie. after a good few hours of running).
>
>         b) How do I measure to be able to give the key manufacturer  
> the
> correct dimensions? I know that most standard tapers are 1:100 (and  
> I'd
> probably go for this unless otherwise advised). The question is hard  
> for me
> to describe but what I'm trying to establish is, is there a point  
> along the
> key where the taper must start to grip (eg 1/3 or 1/2 way along). Is  
> there
> a tried and tested formula for this? I do not want the key to go in  
> too far
> so that I cannot "Grip" the head to remove it later and it must also  
> not
> stick out too far and interfere with a crankhandle adapter I have on  
> there
> to enable me to use the same crank as my Wolseley engines. ( I put an
> adapter on each of my engines so that I only have to take 1  
> crankhandle to
> any rally.)
>         3) Is it  acceptable to use shimstock under a tapered key if  
> I get
> the measurement wrong and the key goes in too far?
>
>         Thanks in advance for any suggestions.
>
> Keep the revs up (or down)
> Jerry Evans
> Near Johannesburg in Sunny South Africa.
> Etched Brass Engine Plates made to order:
> <www.oldengine.org/members/evans/plates/index.htm>
>
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