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Flywheel Key backing out

AndyG

Registered
Last Subscription Date
01/13/2014
Late last season I had trouble with the flywheel key backing out on my Huber. I would drive it back in and things would be OK for awhile and then back out again. I have a tapered key that has worked fine for over 10 years even with occasional removal for repairs or maintenance. I'm afraid to drive it in very hard because it may become stuck and I've already been down that road. I have the key out and flywheel off off the crank shaft. Why did this start to happen? What should I look for?
 

JBoogie

Registered
Age
37
Last Subscription Date
11/12/2013
Late last season I had trouble with the flywheel key backing out on my Huber. I would drive it back in and things would be OK for awhile and then back out again. I have a tapered key that has worked fine for over 10 years even with occasional removal for repairs or maintenance. I'm afraid to drive it in very hard because it may become stuck and I've already been down that road. I have the key out and flywheel off off the crank shaft. Why did this start to happen? What should I look for?
Make sure the taper matches the hub and that its contacting on more than just one sharp point. Does it have a set screw? Burrs on the corners? Bent? Bottomed out? You actually do want it to get *stuck*, it's a friction fit same as in your lathe tailstock.

Clean the key, keyway and seat very well then mark the key up with sharpie, drive it in reasonably tight and remove it. Find the shiney spots and knock them down with a file or scraper. Repeat that procedure about 50-100 times til it shows good contact and you should be good. If the seats are different widths and hammered or bruised it'll be a tough job and a new key won't help.
 

Jim Conte

Sponsor
Last Subscription Date
07/17/2018
Hopefully, your key has a good, strong gib on it for removal when necessary.
Do not have any oil, grease or anti-seize in the hub, keyway or key when installing.
Friction is your friend in this case, as long as you can wedge it out when needed.
Parallel-Taper-Plane-Gib-Head-Key-ANSI .jpgParallel-Taper-Plane-Gib-Head-Key-ANSI .jpg
 

JBoogie

Registered
Age
37
Last Subscription Date
11/12/2013
1/16, 1/8, 3/16 and 1/4 are pretty common. I had the tapered keyseat in my crank disc EDM'd to ⅛/ft because the original was really boogered.

Crank and flywheel go to a Port Huron.
 

AndyG

Registered
Last Subscription Date
01/13/2014
Make sure the taper matches the hub and that its contacting on more than just one sharp point. Does it have a set screw? Burrs on the corners? Bent? Bottomed out? You actually do want it to get *stuck*, it's a friction fit same as in your lathe tailstock.

Clean the key, keyway and seat very well then mark the key up with sharpie, drive it in reasonably tight and remove it. Find the shiney spots and knock them down with a file or scraper. Repeat that procedure about 50-100 times til it shows good contact and you should be good. If the seats are different widths and hammered or bruised it'll be a tough job and a new key won't help.
Sorry I did not answer this earlier. Good weather has had me working on outside jobs. I thought that I was the only one who used a marker instead the the high spot blue. The Huber does not have a set screw. I will check to make sure that the key does not bottom out (good idea, I did not think of this). I'm working on the burrs and imperfections. The key has been filed and stoned, next is the keyway. When I wrote about the key getting "stuck" I was remembering how difficult removal was when I first started restoration work
 

Pete LaBelle

Registered
Last Subscription Date
11/15/2013
Sorry I did not answer this earlier. Good weather has had me working on outside jobs. I thought that I was the only one who used a marker instead the the high spot blue. The Huber does not have a set screw. I will check to make sure that the key does not bottom out (good idea, I did not think of this). I'm working on the burrs and imperfections. The key has been filed and stoned, next is the keyway. When I wrote about the key getting "stuck" I was remembering how difficult removal was when I first started restoration work
I had issues with my flywheel loosening and the key slipping. The set screw on the key was not truely a set screw. I replaced it with a square head set screw with a cup end on it. Still had issues with the screw loosening, so I put a jam nut on it. That took care of the loosening. Due to the nature of the clutch on my engine, there is some outward force applied to the wheel due to the clutch. It would cause the flywheel to creep outwards. Drilled the end of the crank shaft and installed a 1/2" roll pin to keep it from moving. Flywheel now stays in place and no issues with the key anymore.

Pete
 

Ryan Williams

Subscriber
Last Subscription Date
01/20/2019
I had issues with my flywheel loosening and the key slipping. The set screw on the key was not truely a set screw. I replaced it with a square head set screw with a cup end on it. Still had issues with the screw loosening, so I put a jam nut on it. That took care of the loosening. Due to the nature of the clutch on my engine, there is some outward force applied to the wheel due to the clutch. It would cause the flywheel to creep outwards. Drilled the end of the crank shaft and installed a 1/2" roll pin to keep it from moving. Flywheel now stays in place and no issues with the key anymore.

Pete
I see you had the correct set crew with the cupped point. However, did you have the screw tightening on a plain shaft or did you have the screw protruding into a drilled dimple in the shaft? It sounds like you had no dimple for it to bite into if it was slipping while the screw was still tight. Anytime we put something heavy together like that, we always make sure to drill a healthy dimple for the point of the screw to positively lock into. As long as the screw doesn't come loose, it is virtually impossible for the flywheel to slip. I would call that necessary on any tapered clutch engine like yours sounds to be. Glad you got yours fixed and working well though.
 

JBoogie

Registered
Age
37
Last Subscription Date
11/12/2013
I had issues with my flywheel loosening and the key slipping. The set screw on the key was not truely a set screw. I replaced it with a square head set screw with a cup end on it. Still had issues with the screw loosening, so I put a jam nut on it. That took care of the loosening. Due to the nature of the clutch on my engine, there is some outward force applied to the wheel due to the clutch. It would cause the flywheel to creep outwards. Drilled the end of the crank shaft and installed a 1/2" roll pin to keep it from moving. Flywheel now stays in place and no issues with the key anymore.

Pete
Sounds like you resorted to an extreme method to fix the symptom and not the cause.
 

4wheelin05

Registered
Age
35
You're probably all over this already but are you sure the key isn't bottoming out in the key way before the taper gets enough contact? I only ask because I've had that before and we cut the key an inch shorter and everything has been good since.
 
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