8n flywheel ?

[TraktorTom289]

This is my third message as I chase my problem to
ground. I discovered my tractor wouldnt turn over
because the ring gear spins on the flywheel
I split the 8n and removed the flywheel to find Ring
gear to flywheel welds that had broken. I
removed that ring gear and cleaned up the flywheel.
I noticed that the ring gear sits on a diameter of the
flywheel SMALLER than the diameter it has to pass
over when expanded by heat. Is this normal for
the flywheel to have a pocket that the ring gear
shrinks in to? I have pictures but havent figured
out how to post. I could email them if you think
they would help clarify my situation. Thank you

 

[KCM]

How much smaller in diameter are you talking: a couple thousands of an inch or a lot more? I don't remember any necked down area on any flywheels I have installed gears on, Ford tractor or other. If just a few thousands, a previous owner may have let the ring gear slip too long and wear a groove in the flywheel, hence the spot welds to hold it. Normally it is a shrink to fit application so can't be much if any smaller where the gear fits. If the gear is good, I would just spot weld it back on and call it good.

 

[TraktorTom289]

Here is a photo of the undercut. I would guess no more than .005 inches

 

[mhb@ufe]

Yes that is normal on the N series flywheels.

Mark

 

[JMOR]

(quoted from post at 19:38:22 11/07/22) Yes that is normal on the N series flywheels.

Mark

normal"? Normal wear or the way it came from factory, 'normal'?

 

[mhb@ufe]

Normal from the factory, most ring gears I have replaced were worn out not loose and all the N series flywheels I have seen Have the reduced diameter where the ring gear sets.

Mark

 

[wore out]

''Ring gear to flywheel welds that had broken.''

NOT at all surprising, since the flywheel is cast iron and the ring gear is steel.

Welding the two materials together without preheating the cast iron and using special rods usually results in a very weak weld that easily tears away from the cast iron.

Some folks on here report great success with it though. (AKA, LUCK!)

 

[Lynn Patrick]

Some have suggested drilling/tapping/inserting a bolt in the "seam" between the flywheel & ring. What's the group's opinion of that fix???

 

[Abbby]

Welding is the best option IMO

 

[DanielW]

That step in the wheel is normal - and it makes for a real PIA to get the new gear on. Has to be heated uncommonly hot to get around the larger area before it gets to this groove. I (and loads of others) have had good luck with welding, but I freely acknowledge that welding to the cast flywheel isn't theoretically 'proper'. It's a shade-tree fix that can be done quite easily, and (at least for me and others) does the job without requiring a split. Interestingly, I've always been surprised at how well the ring gears weld to the flywheel compared to other cast. To have any chance of your weld holding at all, you usually need proper pre-heat and high nickel wire (if MIG) or special rods (if stick). The N flywheels on the other hand, seem to take a bead of standard filler quite nicely with no pre-heat, and I've never seen one crack yet (knock on wood). I wonder if the N flywheels had a lower carbon content than other grades of cast? Of if there was some variability in their carbon content - some had less than others, which is why some people have luck with welding while others don't?

Your post also got me thinking: I wonder if one of the reasons so many of us have success with welding is not so much due to the strength of the weld holding, but rather the subsequent shrinking of the ring gear. Usually when they slip, they're still a tight fit, and a difference of a few thou would be all that's required to make it hold properly. Welding near the I.D. of the ring gear would cause it to shrink - it's an old trick that's used lots of times to remove stubborn bearing cups or races that are pressed into blind housings; lay a bead around the inside of the race and it will shrink enough to drop right out with no tools required. I suspect enough weld about the I.D. of the ring would shrink it at least a few thou. Just a thought.

I'm not advocating going ham with the welder however: If it's still slipping, chances are it was worn more than they typically are, and you might have to investigate other methods.

 

[Bcurlee]

I ve had to mess with my flywheel 2 times, where the ring gear was loose after after installing. Last time I did the welding and it worked for a while, but it was off in a few places and made my starter lock up. Figured I d buy a flywheel with a worn ring gear, then I could just replace the ring gear. Had to hassle with it a bit to get the new gear on, only to find out it also slipped. Is it possible to stretch the ring gear on installation?