Nice job and write up, Stew! That's a good amount of snow to contend with. Nice when you have the nose of the tractor pointed outward and can fire up the blower and make a straight shot out from the garage. I can see the efficiency of the blower over a loader- ha! I've never had the opportunity to run a GT with a blower before and I'll bet it is a rewarding experience.
Snow Build Up Around Gear Case On Tubeframe Round Back Snow Caster
Posted February 16, 2021 - 05:20 PM
- Dave in NY and 29 Chev have said thanks
Posted February 17, 2021 - 03:12 PM
Since lately I have sheared a couple of roll pins that hold the smaller gear to the input shaft on my snow caster I have been doing some research to try and find out why. I was having this same problem with my lawn mower deck a couple of years ago and I finally replaced the gear case on it with the newer spiral cut gears and used a spiral wound style roll pin in the smaller gear on it. Have used the deck for two seasons and have not had the pin break since - not sure whether the newer style gears or the new gear case were what seems to have cured the problem as I had used the spiral wound pins in the older straight cut gears and they still broke periodically.
For those interested here is a link to the thread I did on the lawn mower deck gear case and the steps I tried before replacing the gear case with a new one
I came across the attached article today called a white paper on the spiral pin and describes how to properly pin a shaft and gear hub which I thought I would share. I replaced the gear set in my mower deck back when I first got it with new gears from an MTD dealer (about 20 years ago) but they were still the straight cut style and the one thing that I do remember was the shorter roll pin was a spiral wound pin that was supplied. I remember quizzing the dealer about it at the time and he said that the spiral wound pins were a stronger designed and that he figured that the split pin design had been upgraded as the split pin style was prone to breaking in some applications. I found the article was an interesting read so I thought I would share it as others may be interested in it - it points out that any imperfections at the hole edges of the shaft and the inner part of the hole in the gears would place stress on the pin since there would be gaps where the pin would not have surface contact. It also mentions why the spiral wound roll pins are more forgiving / stronger in the shaft to hub applications over a traditional split style roll pin.
Going to do some more thinking and the next time I break the roll pin in my snow caster I am going to closely examine the condition of the pin holes in both the shaft and the gear. Still doesn't completely explain why it appears that only the roll pin for the smaller gear always seems to be the one that breaks. The lawn deck gear case increases the speed of the output shaft by having the smaller gear on the output shaft where the snow caster has the smaller gear attached to the input shaft since on the snow caster application the output shaft's speed is decreased.
- KennyP, Dave in NY, Austen and 1 other said thanks
Posted February 17, 2021 - 03:36 PM
I saved a copy of that. Thank you!
- Austen and 29 Chev have said thanks
Posted February 17, 2021 - 05:48 PM
- 29 Chev said thank you
Posted February 18, 2021 - 01:26 PM
I wish my roll pins on the small gear were well behaved but they do break occasionally in the snow caster gear case. Did some more thinking overnight and this morning I dug out the original smaller gear that came with my deck and examined it closely. While the pin holes do not seem to be worn excessively compared to new gears they do have issues on the inner surface where they have been gouged on the edge of the hole by the split style roll pins breaking or shearing. I have included pictures of the remains of the last two pins I replaced. The spiral style had been in use for about a year and the split style pin I replaced it with lasted about 3 days. I know there were marks on the inner surface of the smaller gear in the snow caster gear case and I imagine the pin holes in the shaft at the edge are not healthy either. I ordered a new set of helical cut gears and a new input shaft (from Bolens Parts & Supplies) for the snow caster which I hope will get installed this summer if things work out. Interesting that the pin length for the smaller gear is 1-1/8" as opposed to 1-1/4" for my older deck but I imagine it was to make the pin easier to remove to take the gear case apart. Still don't think it can be done without grinding some of the roll pin away if the pin is not broken as there is not enough room to get the pin in far enough so the shaft can be removed to release the gear- at least in mine. I also ordered a new bearing and seal kit which I am hoping to install along with the updated gears. The teeth count on the new style gears will result in a little bit less reduction ration and affect the speed of the auger a bit as it will run about 1164 rpm versus 972 rpm with the older gear ratio at 3600 engine rpm's. Don't think it should affect things too much and if it does I can always drop the engine speed a bit or increase the number of teeth on the auger gear to offset the change in gear ratio. I got two new pins for the small gear but they are the split pin style rather than the spiral style so I may end up using the spiral style after reading the article yesterday since they are not supposed to damage the pin holes in the gear or shaft. Found my old receipt from when I purchased the new gears for the mower deck back in 2005 and at that time the original pin number of 1185348 was replaced with part number 715-0143 which was the spiral pin. See it still shows up on the MTD Canada web site but is now replaced by number 915-0143 and is still shown as a 1/4 x 1-1/4" spiral wound roll pin by the picture.
I may try drilling the old deck gear to see how hard it is as I may be able to create new pin holes and I have also been kicking the idea around that if the gear could be drilled and tapped then a flat could be made on the shaft and a set screw used to lock the gear to the shaft to help the roll pin maintain its integrity while driving the gear.
I still cannot fully grasp why it is always the pin that drives the the smaller gear that seems to shear regardless of whether the gear case is increasing or decreasing the rpms between the input and output shafts.
Edited by 29 Chev, February 19, 2021 - 11:38 AM.
- Bolens 1000, Dave in NY, Austen and 1 other said thanks
Posted February 18, 2021 - 08:27 PM
- 29 Chev said thank you
Posted February 18, 2021 - 08:39 PM
- 29 Chev said thank you
Posted February 19, 2021 - 11:36 AM
The hub on the smaller gear is a smaller diameter than the hub on the larger gear? Or is the hub the same diameter on both? I am trying to remember but can't picture it in my mind. Would a smaller hub diameter have something to do with the amount of torque being applied to the ends of the pin. Larger hub- more area on either side of the shafts diameter, longer pin, less distortion of the pin by the torque being applied. I don't know exactly how to attempt to explain it. Not an engineer, so maybe it makes no difference anyway. Just thoughts.
The hub on the smaller gear measures about 1-3/8" on the outside and the hub on the larger gear measures about 2" across. I am thinking you are right in that the larger diameter would keep the pin from distorting less at the outer parts that are compressed in the gear. Did an experiment yesterday with a 1/4" drill bit by inserting it (non fluted end first) into the new smaller gear with the gear mounted on the shaft so the bit passed all the way through the gear and the pin - very easy to push in by hand. Then I tried the same thing with the larger gear and found that I had to use a rag to hold the bit and rotate it to get it to slide all the way through the bigger gear and the shaft - pushed in fine until it went through the shaft and started to enter into the other side of the gear.
I do think that the wear on your old gears and shaft are the cause of the repeated pin failure, just as you have stated. It causes a stress point on the pin. Seems like the gears could have been keyed and held in place by a pin or snap rings maybe. The shear pin feature is already in place on the connecting collar between the output shaft of the gearbox and the driven shaft that has the drive sprocket. The Bolens engineers must have had some reason to do it the way they did. Maybe to keep production costs down?
I agree with you on the wear inside the gear and at the outer edges of the hole in the shaft - especially on the smaller diameter gear hub. Unfortunately the way the gear case is shaped there is not much room to accommodate a larger diameter hub as this would just make it more difficult to remove the roll pin to remove the shaft since there is not enough room in the gear case now with a 1-1/8" long roll pin and the pin has to be ground away to provide enough clearance for it to exit the shaft - at least that has been my experience. The use of the needle bearings would make keying the gear to the shaft virtually impossible since there would be no way to install a wood ruff key in the shaft once it was inserted through the needle bearing - no room to slide the gear to allow access to a keyway. Might do it with a long keyway in the shaft and a square key slid into the keyway sideways and then inside the gear - key would have to be secured somehow so it would not move. Might prove to be a nightmare to try and get the key to slide back out so the shaft could be slid out through the bearing. I am thinking that the Bolens engineers used the roll pins because under normal load the pins probably stayed intact and did not break. However once a pin did break on the smaller gear (since the pin does not have as much support at the outside in the smaller gear) the shaft would rotate inside the gear causing the remains of the broken pin to get ground into the shaft and gear in the process. Once this process occurred using a split style roll pin the damage was done and then next time would require slightly less force to break the pin again because of any gouging / distortion around the gear or pin holes. Once broken more than once or twice the wear at the holes would keep increasing leading to failure more often. Just speculation on my part but I will use this scenario to illustrate the larger hub diameter offering more support to the pin. If you look at the output shaft on the snow caster the shear pin that is located on the keyed coupling to drive the sprocket shaft is 1/4" or 5/16" diameter (depending on which hole is used) x 1-1/2 in length according to the parts list and appears to be a split pin design. Bolens must have designed it so that this pin was supposed to shear before the 1/4" diameter split pin inside the gear case would break. The keyed coupling driving the shaft inside it is virtually the same design as mounting a gear hub on a shaft so for this to shear before the pin in the gear the shaft and coupling would have to have a looser tolerance fit or the holes have recesses to make this a weak point so it would function as a shear point all the time. The shear pins could have been a slightly thinner material making them a bit weaker - don't have an original one to verify this. The other thing is that as attachments became larger and tube frame tractor horse power increased this style of gear case started to get tested by driving longer blades and larger augers. Probably worked well until the pin got broken once or twice when something got really jammed up and then started to wear and break more often - again just speculation on my part.
- KennyP and Dave in NY have said thanks
Posted February 19, 2021 - 12:16 PM
Posted February 19, 2021 - 12:23 PM
- KennyP said thank you
Posted February 19, 2021 - 12:31 PM
It was cool in the shop today but I went and dug out the matching larger gear from the mower deck to see the condition of the pin holes at the gear bore - they looked good so I doubt if the larger gear pin has ever sheared as it does not appear that the shaft has ever turned inside the larger gear. Measured the hub on the smaller gear and compared it to the hub on the larger gear - 1-3/8" versus 2" so I believe there is a relation to the pin breaking and less support that the smaller gear hub would offer the pin at the outer edges. Tried a 1/4" drill bit through the larger gear versus the smaller gear - would say the larger gear requires a bit more force to insert the drill bit through it and the shaft but it would push in without having to rotate the drill bit.
Was thinking about trying to bore the inside of the smaller gear out but wasn't sure how hard the hub would be since I imagine the gears were hardened for the application. Rather than try to mount the gear in the lathe in the cold shop I decided to try a less time consuming experiment. I marked a location at 90° to the roll pin holes and slightly closet to the gear teeth with the center punch to see how hard it would be to drill a hole in the hub. With the gear clamped in the drill press vise started with a 1/8" drill bit and used a bit of lubricant (WD40) and was surprised at how easily it drilled - wouldn't say the hub material was soft but not overly hard either - took my time and the bit cut well. Enlarged the hole to 13/64" with a larger bit - again taking my time and it cut fine as well. Mounted the gear in the bench wise and tapped a 1/4" - 20 (UNC) thread in the hole - took my time - the tap seemed to cut well and I soon had a threaded hole. I am thinking that the inner part of the gear could be bored out using the lathe and a new center bushing machined and welded inside the larger bore to repair the marked up pin holes and maybe make the gear a slightly tighter fit on the shaft to make a pin breaking less likely. With the threaded hole in the gear hub it would also be possible to drill a slight recess into the shaft at the hole location and then thread a long set screw into the recess to lock the gear tight on the shaft to help relieve the stress on a spiral style roll pin. Would want to loctite the set screw in place and / or add another short set screw on top to act as a jam screw to keep things in place and not throw the shaft / gear set up out of balance and still allow the shaft to be easily removed when necessary. Any marking on the shaft would be at the bottom of the recess hole and should not get hung up in the needle bearing. With the gear locked up on the shaft there should be less stress on the roll pin as there is now with the gear being able to twist sideways slightly as the shaft and gear speeds change. Again just my opinion.
- KennyP and Dave in NY have said thanks
Posted February 19, 2021 - 12:38 PM
I’m now wondering if I will shred the box on my 38” blower running it with a tractor that’s bumped up to 18hp. I haven’t pushed it hard. Been rather conservative with how much snow I try to stuff through it. Maybe I better not get too aggressive with it.
My thoughts are that if the pin has never sheared there is probably not much chance of it breaking as long as you are using a shear pin at the coupler and that the shaft inside the coupler is free and not seized. With 18 hp versus say 14 hp you may be able to make the PTO belts slip or actually move more snow since there would be less chance of loosing rpm's in heavy snow conditions. Under normal conditions and the way you probably use your blower with the hydro you will probably be good.
- Dave in NY said thank you
Posted February 19, 2021 - 01:43 PM
Reread the white paper on pinning a gear to a shaft and noticed one thing that is mentioned in the paper that does not jive with the smaller gear. The paper states that the minimum hub thickness should be 1.5 times the diameter of the pin that retains the gear to the shaft. For reference the shaft diameter is 3/4" (.750") , the pin diameter is 1/4" (.250") and the total outer diameter of the smaller gear hub is 1-3/8" (1.375"). Subtracting the bore of the gear 3/4" (.750") from 1-3/8" (1.375") leaves a total hub thickness of 5/8" (.625") and when this is divided by 2 the actual hub thickness is only 5/16" (.3125"). The pin diameter of 1/4" (.250") x 1.5 equals 3/8" (.375") which would be the recommended minimum hub thickness that should have been used. This would indicate that the gear hub thickness might be 1/16" (.0625") less than what should have been used. Also the parts lists for the older mower decks recommends a 1-1/4" long roll pin and the parts list for the snow caster recommends a 1-1/8" roll pin be used to pin the gear to the shaft which in both cases would make the amount of the pin engaged in the gear hub less than ideal. In the 1-1/4" pin situation only 1/4" length of the pin would be engaged with the hub and with a 1-1/8" pin there would only be 3/16" length of the pin engaged in the hub. I wonder if the secret to the pin not breaking might be to increase the length of the pin so that it engages all of the gear hub in which case a pin 1-3/8" length would be better. This would give the pin a 3/8" engaged length in the gear hub on both sides and 3/4" engaged in the shaft making the pin engaged equally between the shaft and the gear. The shorter length of the pin (1-1/4" or 1-1/8") would perhaps allow the outer ends of the pin flex and twist as the gear and shaft tried to maintain a constant speed from rest to full power under load. Again just speculation and thinking out loud but it does kind of make sense to me why it is always the pin in the smaller gear that breaks. I imagine that Bolens used the shorter length pins to try and keep cost down and also to try and make it as easy as possible to remove the pin for shaft removal if the pin was not broke.
- KennyP and Dave in NY have said thanks
Posted February 19, 2021 - 03:43 PM
Found this information on removing a spiral wound spring pin that I found interesting so I thought I would share - think the same information could probably be applied to a split style roll pin.
I also came across a few other sites that offered removal suggestions which I will mention.
If the pin is in a blind hole and no part of the pin extends out you may be able to remove it using some grease and a loose fitting punch. Using a grease needle (or a similar method) fill the hole inside the pin with grease. Then use a loose fitting punch, insert it a tiny bit inside the hole of the roll pin and then drive the punch into the hole with a hammer blow. The logic is that the sudden force will compress the grease quickly and since the grease has nowhere to go it will expand into the tiny cavity at the end of the roll pin and the bottom of the hole and begin to push the pin out of the hole.
If the pin is in a through hole where it can be driven with a punch you can drive it out that way. In the case (no pun intended) of a Bolens Tube Frame gear case there is not enough depth in the bottom of the gear case to allow the pin to clear the shaft before it engages with the inner face of the gear case. Once this happens it usually jams the shaft and gear from rotating and creates a dilemma as I can attest to! If you have not driven the pin too hard sometimes (if you are lucky) you can use a screwdriver to force the gear and shaft to rotate so that you can drive the roll pin back in so it clears. Once it turns freely you can rotate the shaft so the roll pin is sticking outwards and then you can grind the end of the pin to shorten it. Eventually with enough of the pin ground off it will be short enough to drive out of the shaft without catching on the gear case and then you can slice the shaft out of the gear and finish removing the now useless roll pin. The article I read suggested that you start the pin by driving it out as far as you can without it binding on the side of the gear case. Then rotate the shaft so that the end of the roll pin sticking out is facing you and find a round piece of steel that will just fit inside the hole inside the roll pin - perhaps a piece of welding rod, a smaller pin punch or a drill bit. Whatever you use it must be solid so that it will not compress. Once the steel piece is inserted the roll pin can then be clamped with a pair of vise grips so it is squeezed and tight on the steel piece. Since the steel piece removes any spring (or give) in the roll pin the vise grip jaws will clamp tightly on the outer surface of the pin and can then be pried on with a flat screwdriver to wedge the pin out of the hole. You may have to reposition the vise grips a couple of times depending on the length of the roll pin before it disengages from the shaft. Some people have even welded a nut onto the side of a pair of vise grips so they can thread a slide hammer arrangement into the nut and use the slide hammer momentum to pull the pin out of the hole.
I have not tried the methods suggested but thought I would share them. I have tried to clamp a roll pin using a pair of vise grips to try and pull it but did not have anything inside the roll pin hole - as a result the vise grips just slipped on the roll pin because the pin would spring smaller. Thinking I am going to try this again sometime with the pin hole filled and see if the vise grips slip or hold onto the pin surface.
- KennyP and Dave in NY have said thanks
Posted February 19, 2021 - 08:01 PM
Great advise on the pin removal ! I too made the blunder of driving a pin too far through the gear and then couldn't rotate it back around to get the pin out. It was my extreme good fortune that the box I was learning on was pretty much a junk one anyway, very rusty inside. I was just tearing it apart for whatever I could possibly salvage. I ended up forcing the shaft back around which bound the end of the pin against the inside of the case, finally broke the pin off near the surface of the gears hub. Made quite a gouge in the gearcase. Wasn't a big deal as the case was beat up on both snouts where the seals go and had a crack in it too. All the boxes I have recently taken apart I have done the "grind the end off" method till the pin is short enough to clear the hole in the shaft. This of course necessitates the complete disassembly of the box to clean out all the metal fragments from the grinding. I'm sure you've had a similar experience. I also had a devil of a time trying to pull the pin with the vise-grip approach. Ended up using end nipper type pliers to pull the pin out. I hadn't thought of putting something inside of the pin so it wouldn't collapse. That is so simple, why didn't I think of it? I also had a thought of drilling a hole in the case to allow the pin to be driven out of the gear and out through the side of the case to remove it. Would have to tap and put a plug in the hole to seal it. I wonder if that would weaken the case enough to cause an issue? I always just figure that the teardown of a box means I need 2 new pins. I have always used the regular duty split pins that I find at the local hardware. I believe that a couple of times the pins I used extended past the surface of the gears hubs by maybe a 1/16" on either side. I remember grinding a pin off a bit because it was longer than needed to fit the gear. The hardware was out of the one I wanted so had to buy the next longer size. I typically grind an extra bit of a bevel on the end that is going in first just to help get it started in the hole too. I thought that it might help align the holes of the shaft and hub if I was off just a smidge too. I'm not sure if having the split in the pin aligned in any particular position makes any difference or not. If you made the split aligned with the length of the shaft then it would be be solid against both surfaces of the gears hub in relation to its rotation. And vice-versa. If that makes any sense? Not exactly sure how to explain it. Probably makes no difference. I also wonder if a smaller diameter split pin could be driven through the one that keeps breaking. Or possibly a piece of some softer metal , a finish nail, a piece of heavy wire? The second pin would prevent the larger pin from distorting from the torque being applied on it. Would have to slather it up with Loc-Tite to make sure it didn't come loose. Maybe a bit of solder on either end? This goes back to the thought of inserting something inside the pin so it won't distort so you can grip it with the vise-grips. Just thoughts.
- 29 Chev said thank you