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Discussion Starter #1 (Edited)
a while back I obtained a Gilson 55012 gear drive machine, circa early 1970's mfr., and went through it. it ran great.
last year I was getting it ready for a storm, and didn't notice the auger tines were frozen to the ground. also inadvertently had left the augers engaged.
upon starting it, the augers tried to instantly engage but did not. the impeller would spin, machine would move forward/reverse, but augers would not turn. this is after a complete auger gear box rebuild, new seals, bearings, races, oil, impeller bearing, and impeller shaft !
I thought for sure, the augers frozen in the ground, had taken out the bronze gear in the gearbox.
today finally got it apart- and much to my surprise, there was NO DAMAGE WHATSOEVER. what happened was, after removing the end bushings in the chute, and the impeller bearing, upon pulling the gearbox/axle/shaft assembly forward to remove it from the chute, the entire assembly slid OFF the impeller shaft, leaving the impeller shaft with impeller still inside the chute.
WTH ??:smiley-confused009:
upon disassembling the gear box, everything was intact, except for the snap ring behind the front gearbox bearing had slid off the impeller shaft, and the woodruff key for the worm gear was lose inside the gearbox.
how the heck did this happen ?
there IS a snap ring between the front gearbox bearing, and worm gear. but it came off the groove, allowing the impeller shaft to slide out the back of the gearbox, and disengage the worm gear woodruff key.
so....
I re-assembled the whole thing, being sure to seat all the bearings/races/worm gear firmly. tweaked the front snap ring to make sure it's on the shaft groove tightly. then set the front worm gear preload with the machine running. it did take one more cotter pin slot tighter with it running, compared to static setting with the axle out of the machine. now it's running again fine.

but for how long ? is it going to jump the key again ? if it does, I'm not pulling the entire assembly again, just going to remove the big front gearbox adjusting plug and the bearing/race, and take a look inside- next time.

anyone want to take a gander guess, WTH happened ? I'm stumped. I have video of this machine running on youtube last year, but SOMEHOW it pulled the woodruff key out of the worm gear, when the augers were stuck in the frozen ground.

I'm guessing the entire assembly flexed and impeller shaft jumped rearward in the machine, and spit the woodruff key off the worm gear ?

any ideas ? this is NUTS !!
 

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LOL - maybe that key left a bad taste in her mouth!!? IDK - I would hunt down a exploded view and see if your missing a snap ring or roll pin somehow? Especially while it's fresh in your mind. Obviously something was able to move an aweful lot.....
 

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Discussion Starter #3 (Edited)
well it had to move BACKWARD, cuz the impeller bearing is the 2 piece locking collar type, brand new, and was locked on there good.

something forced the snap ring off the groove, and somehow the worm gear moved rearward enough to clear the key, and the shaft was spinning with the worm gear sitting still while running.

yet it could NOT move very far backward either, cuz the IMPELLER itself would hit the back of the chute and stop it !!

wth happened ? it's a phenomenon !

weirdest damned thing I ever saw....
 

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hard telling - maybe the snap ring wasn't quite seated somehow....? Or maybe there a little wear somewhere that is just enough to allow things shift/hammer on each other? I suppose if it never happens again you fixed it without knowing how! ;>P
 

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This a new one!

I can see the retaining ring getting popped on a profound overload if the preload was sloppy enough to create an impact situation, especially if the sharp edge of the ring was facing the back. But with a securely locked impeller bearing that seems unlikely.

However, assuming it happened... You could then pull the worm drive off of the impeller shaft as you described IF the worm key was facing downward AND had a loose fit so it could escape the shaft in time to avoid the input bearing and seal.

Does that many any sense?

Pete
 

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Discussion Starter #6 (Edited)
you lost me....and I never knew until now a snap ring had a sharp side !




the loose key can't make it back to the seal- the rear bearing/race would stop it, as the shaft slid out. the loose key was found with the snap ring in the front bearing/race area

actually the front bearing, race, key, and snap ring were like a little stew in there, all mixed up, when I took it apart....:blush: the key and snap ring were in front of the worm gear, and key no longer inside the keyway in the worm gear

it just makes no sense to me.:huh:

the preload was not too loose, to my knowledge- but could it have been too tight ?
i.e. could I have tightened it to the point, the front adjustment nut pushed the snap ring right off the groove ?
the front bearing tension plug, as it threads in, pushes on the bearing/race against the thrust washer and snap ring. I could have very well pushed the snap ring right off the groove by over-tightening, it would work like a press as it's tightened inward.

the snap ring was visibly sprung like they get when too much outward pressure is used to remove them, like it was forced off the shaft groove by extreme force, the 2 ends didn't meet together, and had to be straightened out with pliers to re-use it.

the augers frozen in the ground and the augers engaged on cold start, was the stimuli that caused it. but now I'm starting to think, the snap ring was already off the groove. just needed that jolt to spit the key out.

I know one thing- just like Quinn in the movie Jaws with the life preserver....
I'll never start a snowblower with the augers engaged again
:redface:!
 

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Discussion Starter #7
However, assuming it happened... You could then pull the worm drive off of the impeller shaft as you described IF the worm key was facing downward AND had a loose fit so it could escape the shaft in time to avoid the input bearing and seal.

Pete
on second thought....maybe we should build another machine and freeze the augers, just to do it again and find out why....:wavetowel2:
 

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on second thought....maybe we should build another machine and freeze the augers, just to do it again and find out why....:wavetowel2:
Actually in hindsight even that won't work because the key can't get through the spacer and bearing. There's no way there could have been space between the bearings for the key to get out of the worm. :smiley-confused009:
 

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Discussion Starter #9 (Edited)
Actually in hindsight even that won't work because the key can't get through the spacer and bearing. There's no way there could have been space between the bearings for the key to get out of the worm. :smiley-confused009:
yeh I know, looking at the arrangement inside the gearbox, before I bolted the side cover on, it's all sandwiched together bearing-thrust washer-worm gear--thrust washer-snap ring-bearing from back to front, no room for the key to get out

I think this is what happened, I switched the impeller pulley key with the worm gear key, they are the same size, but the pulley key was beat up from being seized and having to be forced off the shaft, and heated, when I first disassembled this machine back when. the pulley was really seized on there. they key was really beat up too and had to be filed to flatten the sides of it

pretty sure what happened, was the key just fell out of the keyway, and was small enough to slide forward inside the keyway of the worm gear, and rise up and disengage the shaft- that's all

the snap ring was also disengaged as well, the thump of the quick engage broke everything free somehow

the impeller pulley has a set screw to hold the key in the keyway, this time I put the keys back in their respective places again, the better one on the worm gear this time, as it was at first.

if it happens again, I'll have to get new keys, and custom fit them to completely fill the keyway slots
 

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Discussion Starter #10
it was a relief to be able to remove the impeller pulley and bearing this time, by just undoing the set screws and pulling it off, and tapping the lock collar once with a drift.

unlike last time when I first got it, almost needed dynamite to get those parts off....:):icon_whistling:
 
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