Author Topic: Broken Gib keys  (Read 9087 times)

lev-l-lok

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Broken Gib keys
« on: May 01, 2006, 02:32:08 PM »
List, well we've gone and broken the heads off both Gib keys on my buddies Metro. Note: to accomplish this we did the following. First, we stripped all paint from keys and crank, as well as the keyway itself, washed down the area with thinner, and dried. Second, soaked both keys for 4 days with Kroil, occasionally tapping the keys w/ a small hammer (about the same amount of force used to carefully center punch something) and adding more Kroil front and from crankcase side as well. We used a piece of 3/8 X 2 X 6 steel, split lengthwise diagonally as tapered wedges. Tapped the wedges together between the flywheel and the head of the Gib,with the wedge closest to the flywheel as the movable wedge. Tensioned the Gib for a couple of days, again with liberal feedings of Kroil. After 3 days of increasing pressure, the heads of course snapped off, with the failure point being at the base of the key head. Note that the face of the wedge against the head of the key was smooth, with carefully broken edge to clear the 90 deg intersection of head to shank of key. We have now made a drill guide and drilled the remnants of the keys to a depth about 3/16 past the center of the flywheel, carefully tapped 5/16-18, constructed a slide hammer using same threaded bar (B-7) and a slide weight of approx. 3-1/2 lbs. NO JOY!
we have considered packing the key area w/ dry ice to hopefully shrink the area some to reduce the grip, please help!

Paul
Paul

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cujet

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Re: Broken Gib keys
« Reply #1 on: May 01, 2006, 03:17:14 PM »
Looks like you sheared off the key. This is why I made my own gib key puller with 4 bolts to tension the device and a slide hammer to break it loose. That way no stress risers are placed on the key itself. Just a smooth surface applying the pressure.

I made it out of iron pipe with a slot milled in the end. Welded on some steel to pull the key, while leaving enough room to install the device.

Chris
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Halfnuts

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Re: Broken Gib keys
« Reply #2 on: May 01, 2006, 03:30:14 PM »
Paul,

At this point, I think you've gotta ask yourself if the flywheels REALLY need to be removed.  Were I you, I'd clean it up and be happy with it until further notice.

For the sake of the others reading this, one thing I'd suggest contributed to the problem is that by using two tapers simultaneously to wedge the key out, you pulled straight on the keys.  The method I saw on the Utterpower CD involved using a single taper.  The advantage I see with doing it that way is that the key is first pulled and twisted one way as the taper is tapped, then the taper is removed and tapped in from the other side.  That concentrates the force, stretching first one side of the key, then the other.  That worked for me.  Key bent like a potato chip from the force, then slowly began to move.  It's important to keep the wedge from climbing the head  of the key, so I used a C-clamp to restrain that tendency.  As force is applied, the wedge wants to climb the head of the key and that makes a failure like you describe more likely.  

None of that helps you now, though.  All you can do is continue to drill, but you'll likely bugger the keyways.  Dry ice might work, but holding it in place until it can cool the crankshaft is going to be difficult.  I don't know what new crankshaft and flywheels cost, but that might be what you're facing.

Halfnuts

akghound

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Re: Broken Gib keys
« Reply #3 on: May 01, 2006, 03:39:33 PM »
This happened to us on a Sawmill drag chain once. I don't know how good you are at welding, we simply welded a bolt onto the remaining part of the Jib Pin. The portion that was welded was ground flat so as to get a good match on the surface of the pin. Then a Slide Hammer was attached to the bolt and the pin came right out with just a few whacks of the hammer. I think that the heat from the welding helped loosen it. Use caution here not to over heat the shaft!!
Ken Gardner
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Geno

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Re: Broken Gib keys
« Reply #4 on: May 01, 2006, 04:36:44 PM »
I did the same prep as you Paul but then used the Utterpower method. When I could see the key begin to "arch its back" I backed off. I was really wacking the wedges hard. I put on my loggers helmet, goggles, gloves, etc. I'm going to make or hopefully borrow a remover like the one Rocketboy (I think) made. I'll leave the engine out in the sun on a real hot day, put some insulation around the flywheel, spray the key and shaft with the coldest stuff I can find. Put the puller on quickly and hope for the best. Good luck. Let us know what you find.
Thanks, Geno

OK Joe. Utterpower CD method as of 12/30/05
« Last Edit: May 02, 2006, 02:35:09 AM by Geno »

Joe

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Re: Broken Gib keys
« Reply #5 on: May 01, 2006, 09:59:49 PM »

Utterpower has more than one way to remove a gib key...call George.
Brucem was kind enough to post a picture of the puller I built on Feb 21 in coppermine. This was from a verbal description I found on this forum….
... No hammers involved….

Joe
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Andre Blanchard

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Re: Broken Gib keys
« Reply #6 on: May 01, 2006, 11:16:36 PM »
Could also check the archives at this site, they know all kinds of ways of break... getting stuff apart.
http://www.smokstak.com/forum/forumdisplay.php?f=5
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hotater

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Re: Broken Gib keys
« Reply #7 on: May 01, 2006, 11:25:54 PM »
 Paul---

Wow.  I was *really* hoping you'd quit before drilling.....

I know that there are (at least) two different crankshaft/flywheel keyways made in Listeroids.
I "proper" Gibkey way is tapered on the shaft and on the hub so any hole drilled *has* to be crooked to start with....OR longer than the shaft sticking out past the key so you can get a straight run at it.
  There's at least one parrallel keyed engine with a tapered key in it....or was in it.

To solve the problem---

The only sure-fire way to save the shaft and wheel is with a portable EDM with a custom-made electrode and a LONG time for it to work.  It'll work...no doubt about it, but probably at a price approaching the engine, plus shipping.....IF you can find one.  They're used to remove burnt bearings and studs in large equipment.

What *I* would do---  I'd make a collar to fit flush with the flywheel hub to be sure that dang thing don't *fall* out, and I'd run the engine until it HAD to have a new crank.

IF the flywheel starts knocking and acting loose you can cool the crank with dry ice and white gas (Coleman fuel) and try to use the clearances created with temperature differential to move it.   Concentrate on moving the flywheel IN, not the gib key out.  If the wheel moves .050 the key is as loose as it's likely to get.
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JohnF13

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Re: Broken Gib keys
« Reply #8 on: May 02, 2006, 12:41:17 AM »
This method will only work if you have some clearance behind the wheel between the wheel and the crankcase housing......
If you do (and it should be about 1/3rd inch) you can weld the broken key head back in the groove then make up a flywheel PUSHER as opposed to a key puller.  As others have said, it doesn't matter if the key moves or if the wheel moves - either way the  key comes loose.  You need to make the pusher out of 1/2" plate steel, anything thinner won't work.  After you get the pusher locked behind the welded on head, you push the flywheel by tightening down bolts (at least 3, preferably 4) sequentially that press on the centre portion of the wheel.  Again, time, patience and a lot of oil is going to be needed here.  As you are pushing, try to rotate the wheel while holding the shaft still.  Once it begins to move you will be able to work the key droppings out.  The big problem here is that the key has been drilled - that is going to cause problems as you could have damaged the keyway or the wheel.  George B is talking about making a drill guide to help do this - send him an email to see whre he is with the project. 

If you can get one off, you should be able to remove the complete crank, then you can back-drill the second.

Good luck!
John F
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Re: Broken Gib keys
« Reply #9 on: May 02, 2006, 02:01:11 AM »
FYI:

Even light taping on the shaft of a TBR engine or ST head shaft will shorten the life of the bearing by causing what is called "Brinelling Damage". Small pits or ruts in the case of the TRBs caused by the slightly harder Balls or Rollers denting the softer races. Cheap bearings suffer more of this damage due to poor heat treating at the factory.

Doug