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Don't Use Roll Pins for Shear Pins....


BigSix

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...or more correctly, do it at your own risk, as I did. (Note: this invovles what is techncially a walk-behind tractor, my 1966ish Ariens 6hp. 10M6D "two-wheeled tractor". It came in-unit with a 24" snowblower, (Mod. # 7-10M) but it is, techncially, a separate tractor/blower combo, so I feel it is okay to post it in the "Talking Tractors" forum.) A little over a year ago, I asked folks here what they did if they could no longer find replacement shear pins, like I can't, for my old 5hp., 2 stage snowblower, a Yardman "Sno-bird". Well, there wasn't a consensus, per se. In fact, there was confusion re: which sheared easier, Grade 8's or Grade 2's, with opinions on both sides, and the mention of roll pins as a substitute, which I had originally asked about. As I couldn't decide who was right re: the "which shears easier" debate (among different grades of bolts), I went with roll pins. To be extra cautions, (or so I thought) it was my idea to prescore them at the shear points, which I did, with a Dremel and cutting wheel. I began using them in my newly-acquired, personally-refurbished Ariens (mentioned above) which is a crime because, unlike my old Yardman Sno-bird, the shear pins for the Ariens are still available, but it was snowing, the store was closed, etc.... In fact, I scored them so deeply, I felt they were breaking easier than the factory pins had, so, of course, I put off getting the original pins. And it snowed again. And it might have worked out okay, except that (unbeknownst to me) one pin was slightly undersized, (or got knocked) and slipped partially out of alignment in the shaft, so that my prescored shear-lines were out of registration with the auger drive shaft. The pin broke on one side, but only bent, into a "z", on the other side, and not in the correct location. Add one coblerock as big as my fist, hiding near a tree where I'd missed seeing it over the summer. Result: one wiped out "pinion" gear, on the fan/impellor shaft. This shaft is the input shaft into the 90-degree auger drive's gearbox, and that's where the gear that got creamed is, so that the auger's ring gear no longer turns, even though the fanshaft and it's pinion gear are still spinning, albeit toothlessly. I have a donor machine (4 hp) and the ring gears are the same, but the fan shaft's gear is machined into the end of the fanshaft, and the 4hp. has a shorter shaft and different clutch, so no swap. Which is a shame, because the ring gear appears to be fine (so I have two of those--lol). I called the EXCELLENT support staff at Ariens, and spoke with the same senior rep. I had talked with in the spring, while sourcing the two-jawed clutch I needed to run the 26" mower deck attachment I also got with this snowblower/walkbehind tractor. And HE told me: "Roll pins are WAY harder than shear pins. If you were gonna substitute ANYTHING, you would use a Grade 2 bolt, but you MUST prescore that bolt." Now, that's kind of odd, since the ring gear is actually held to the augershaft (inside the gear box, and viewable by taking out the oil fill plug) by a roll pin, from the factory. I didn't ask the gentleman why that was, but he did indicate that if I was lucky, that roll pin might have broken. As you know, I wasn't lucky.... I'm just writing to try to prevent the heartbreak of thinking one was being careful, and actually wiping out a wonderful machine, by substituting roll pins (even prescored ones) for shear pins. For the record, when I drove out the shear pins on the four horse, (same size as in the 6 hp model) I found that they were so soft that one mushroomed, slightly, lengthwise, during the drive-out, and snapped almost instantly when I tried to use it anyway. IOW, the (presumably original, as it was prescored) shear pin was made out of EXTREMELY SOFT metal. And this would seem to belie the earlier discussion of tensile strength being the opposite of shear strength, as again, I drove it out lengthwise, and it bent just from the friction in the auger shaft, when I drove it out. IOW, it seemed equally soft, both compression-wise and shear-force-wise. Also for the record, the Ariens 10M6D tractor and 7-10M, "ST 24" blower is a WONDERFUL COMBO, with incredible traction considering the lack of studs or chains. It's heavier but better balanced than the Yardman product of 1972 that I have, has FOUR forward speeds, (the Yardman has only one--and it's slow) a squeeze-grip drive clutch, TWO blower clutches, (allowing use of wheels without running impellor/auger) and a nifty, one-button "neutral hold" feature, allowing you to stop without shifting out of gear. It also allows drive in both locked and open-diff modes, whereas the Yardman only drives when locked. The simple, approx. 270-degree (plus?) rotating chute is also both simpler and much superior to the Yardman design, and allows practially blowing over one's shoulder, saving some maneuvering. Did I mention that this machine almost never clogs? It will pump the slush out of the road and refuse to clog. (I carry a large paint stick when using the Yardman....) The biggest advantage over the Yardman (other than the mulitple forward speeds) is the fact that, when you stop forward motion or use reverse, the impellor/auger continue to turn, keeping the chute clear. On the Yardman, because the wheels drive the auger, stopping motion = instant snow jam, if conditions are wet. In short, this machine runs rings around any snowblower I've used in the past. I would grab one, if given the chance. The $25. I forced on my neighbor (he was throwing it out) seems like a bargain, especially considering the massively-built 26" mower deck that came with it. When I got it, the "bucket" (snow scoop) was torn at the side, the shoes had NEVER been adjusted from dead low, the carb was gunked and misadjusted, nails were substituted for cotter pins, and it barely ran. The oil was grotesque. The bucket "blade" was assymetrically worn, by virtue of the deformation of the torn bucket. (I ground a straight edge on it and reattched it to the straightened bucket.) Some hammering, welding, paint, TLC, and it was great--right up until yesterday.:( I should add that although it has pathetically low compression, it still pulls well and doesn't smoke or knock. I can only imagine how much power it would have if it had decent compression. Oh yeah: I'm also writing to see if someone has the fan/impellor shaft for a 1960's era Arien's snowthrower, roughly 24" in cut. I say roughly because apparently it was a popular blower affixed to a number of different horsepower machines. If anyone even has something they think might work, I'd love to hear from them, as this guru at Ariens can tell me in about 60 seconds whether it will swap or not. Thanks for listening, and I hope this saves someone else some serious grief. I'm used to laughing (privately) at other people's ignorant mistakes causing the ruination of fine machines, not my own.... But then again, I'm not actually laughing....
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We all learn some of these life lessons the hard way. It would seem that they come and hit us the hardest on the things we hold too much value in or when we're in too much of a hurry. lol That's when it hits me.
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I once dropped a bolt down the engine shroud and it ripped off six of the fins.... luckily I have a parts- rich friend nearby and saved $180
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I don't know if it helps at this late date, but I think ACE hardware carries a large stock of different sizes and lengths of shear bolts. At least my local old-style store does... Question. If we have to use a grade 2 bolt, how much and where do we score it? Both shear lines or only one?
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Dave, thanks for the wise words:
quote:
We all learn some of these life lessons the hard way. It would seem that they come and hit us the hardest on the things we hold too much value in or when we're in too much of a hurry. lol That's when it hits me.
It actually helps, to know I'm not alone in my self-induced predicament. Thanks. Mowingman--ouch! I can definitely relate. Parts rich neighbors are great, but I'm fresh out of those, where I live. My neighbor does have the wire-fed welder I was using, though, so I really shouldn't complain too much about the zip code I'm in, I guess--lol. dratkinson: You know, I appreciate any such sources. And I do have a wonderful, old, family-owned hardware store in my town--been there since the '20's, in fact. While they did sell off their small engine repair business years before I got here, I'll ask about pins anyway. And if they have them, man will I feel stupid![:0] Re: your question:
quote:
Question. If we have to use a grade 2 bolt, how much and where do we score it? Both shear lines or only one?
I'm not sure, given my recent history, that I'm the one to ask. :o) Seriously, I'm confident in saying you should score both sides, as that is how every original shearpin I've seen was scored. Especially since, in my case, when the pin slipped out of alignment, one side broke on the score, and the other merely bent, in a location NOT on the score, making me think that it all it took was one side of the unscored pin to wipe out the pinion gear. Re: how deeply, I will ask my guru, the next time I bother him (which I anticipate doing again, soon) but until then, I would say to duplicate what you see on the original pins, i.e., a 1/16 of an inch or so? You could also experiment, and score them radically, i.e., an eigth of an inch, or halfway through, and see if they break just under the snow load. If not, I guess you didn't score them too deeply, you know? The other thing I didn't like about using regular bolts, of any grade, is that the threads run up most of their length, meaning that the points of the threads are bearing on the inner surface of the shearpin hole in the shaft. I felt this would erode the inner surface of the hole, over time, but perhaps that is a groundless fear, given that the shaft steel would be harder than the bolt? With snowblowers, there's little dirt, but if the softer bolt's threads were working in dirt, (say, in a mower or tiller) I still think there could be some erosion of the internal diameter of the pin hole, that the smooth sides of an original shearpin would do less of. But perhaps I've got it backwards, and the threads would shift the dirt away from the sides of the hole, whereas the smooth sides of an actual shearpin would trap the dirt hard up against the inner surface of the shearpin hole? Any opinions on this, anyone? Thanks for the responses, guys, and I'm still hopin' somebody's gonna say "Hey, I've got an old, orange-and-cream-colored Ariens snowblower, for parts, in my back '40.... Come and get it!" Thanks again.
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A grade 8 bolt will shear before a grade 5 and a grade 5 will shear before a grade 2/non grade bolt Most shear pins are grade 8 in my experience. The shear pin/bolts in the simplicity 2 stage blower for the sunstar are grade 8. If you replace the roll pin in a Subaru CV joint with a grade 8 bolt it will snap them as fast as you can put them in the roll pin will last just about forever, a grade 2 bolt will last almost as long. The roll pin is not soft like a grade 2/non grade bolt but it is not hardened like a grade 8 either
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Off topic, but very related so here goes; Whenever you can, use the proper parts. ;) I know of a factory, that ran out of shearpins and used a 1/2" stainless steel bolt in its place. It was a large 12" stainless steel auger that did use 1/2" shear pins. anyway, after the fact, they figured a stock shear pin would have broken under much less resistance. :( Add to that, a teenager that didn't know any better, and maybe the standard shear pin would have stopped at my steel toed boot, rather than my knee where the bolt finally sheered. UMMM 2 1/2 wraps and 2 1/2 minutes later.....
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Unfortunatly, shortcuts are not always that. I hope find the parts you need :) Gord
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Sorry to hear of your bad luck. A few years ago during a big snow storm I was having a problem with our snowblower's right hand wheel where it would spin faster then the left causing the shear pin to shear. After going completely through my bag of shear pins, I talked to my neighbor who suggested roll pins. I remember my father doing that with our old snowblower and he busted the drive gears. I just ended watching the wheel an when it was about to fall off the axle, I would push it back on. When I had it tuned up two years ago, They told me the drive belt was so stretched that was what caused it, and probably exactly what happened to my fathers old Ariens and the combo of the roll pins he substituted.
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Dan: I have no words that are remotely adequate. I so wish that hadn't happened to you, but you're right--I don't think there could be a more potent reminder of the importance of not using the correct parts. Thank you taking the time. And congratulations on your Presidency--I've been away, and wasn't aware. Nick and Simpleman: Thanks for your kind words. Obviously it could have been much worse. I guess this is a lesson in keeping one's perspective, huh? I mean, every year, people put their hands in snowblowers, to clear the clogs, right? I've never understood how they could do that, but read on.... (and knock on wood three times!). Well (and this is very embarrassing to admit, but is related to hurring and being stupidly concerned about little things, to the point of danger): at one point, when I was trying to figure out what had happened to the blower, it was running, in neutral, with all three clutches disengaged (the two that power the auger/impellor, together, and the wheel clutch) and I actually grabbed the nonmonving auger, for a second. I couldn't believe it did it. True, it was physically disengaged, twice over (two clutches between rpms and the auger) but STILL. First time in my life I can recall doing something that stupid. What was it D-17 Dave said about "...when we're in too much of a hurry"? Dan's story points out how quickly something goes from inconvenience to tradgedy, though in my case it involved my own stupidity. Thanks everyone, and be careful (talking to myself here, of course, first). Peter
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