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SmilinSam

Bd-d-d-d-bang-bang-POW-POW-clink clink!

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SmilinSam
MPH, Of course it had to be the pride of our fleet.................the Homelite T-15 which is in the Gallery on Simpletractors. Its the kids tractor now. Told him I'd show him what to do, BUT "YOU are going to fix it" Everyone has to learn somewhere, besides I'm up to my armpits in 4040 and 720 repairs at the moment..... I really didn't need this occurrance......... Kris, Unfortunately I have indeed heard that sound before. This time only only one bolt let go from one coupler before we shut it down. The input shaft bearing is prettty well wiped out, and I suppose the driveshaft is bent a little too. The last time was worse, one bolt let go at the gear box end and instantlt shredded the coupler letting the shaft spin free at 3600 rpm still attached to the engine. That was on a 700 series AC and it literally flattened the brackets on the lift shaft, jerked the wiring out, and broke a chunk out of the flywheel pullley. Not to mention twisting up the driveshaft like a pretzel. I think I got lucky this time by comparison. The worst part on the AC homelites is that you have to completely disassemble the upper end of the tractor to get to the engine end of the driveshaft....no fun. Also, Just sailed into the "super BIG mouth club", but last time I looked Dutch was on my heels. No hope of catching MPH though, but I do think MPH has a sporting chance of catching Kent. Whatta you think????

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powermax_paul
Sam, Kent's been kinda quiet lately. Apparently he's got his hands full (with good reason). I think MPH will eventually catch him. I've often wondered what would happen if my powermax drive shaft couplings let loose. Just seems like those flex discs are pretty light for 20 hp. Paul

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UCD
I have heard that sound a couple of times. I was lucky did not do any other damage just bent the shaft I now have 2 spares I straightend them to .001 run out. I checked a new one and it was at .003 This & $1.00 might get you a small Coffee Maynard aka/UCD

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SmilinSam
Dutch, I could have forgot to thoroughly tighten the one bolt but I doubt it. The 700 series escapade was a result of a grade two bolt breaking off at the base of the nut. I put that one back together without changing anything on the BGB. Could be the same thing here. The BGB on the Homelite seemed to be all right so If I had to guess, If anything I overtorqued a low grade bolt and cracked it. Purely speculation at this point. Im going to used at least grade 5 bolts from now on regardless.

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UCD
Sam You should stay with a good grade 3 bolt there. Granted you gain clamping strength with a higher grade bolt but you lose shear strength. Shear pins and shear bolts are grade 8. I broke a bolt in a drive shaft on another make tractor once and I thought I would fix that and put in a grade 8 bolt I was breaking them as fast as I could put them in. Then I put in a grade 5, I wasn't breaking them as fast but they broke over a short period of time. I went to a grade 3 and never broke another one. the original bolt broke because it was loose. If you want clamping strength on a part that will be pulling away from the other part use grade 5 or 8 on parts that twist against each other use grade 3. This & $1.00 might get you a small Coffee Maynard aka/UCD

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StinKy
HMMMMMMMM. Guess I'll go check some driveshaft couplings while it's fresh in my mind. Never checked the grade of bolts in them but I "think" they are Simplicity originals. I can now certify that old Briggs is turning 3600 since I got one of those Vibra-Tachs from Precise Engine. Previously I had the high rpm limit set by ear and was getting around 3000 rpm. Really a clever device.

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UCD
Mine did not break because of loose bolts. The fiber disks broke caused by coming to a quick stop. Throttle wide open and about half speed and the snow blower got caught on a side walk crack that the frost had raised and another time the lift rod stop collar fell off causing same problem. Running Ag tires loaded with wheel weights and 2 link ice chains didn't help in this case as wheels didn't spin just stopped dead. This & $1.00 might get you a small Coffee Maynard aka/UCD

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Woodydel
First I called bolt manufacturers and was told that grade 8 has higher shear strength that grade 2 or 5. I called 3 different manufacturers. That was not enough for me. Maybe this proposal to use grade 2 bolts in shear situations had merit and I wanted to "see" this first hand. I decided to do a simple test related to shearing bolts. I'm assuming that there is no such bolt rated grade 3 since I know of only 2,5 and 8 as grades. I used a simple bolt cutter as the shear testing device and a scale placed such as to allow the cutter arms to exert force against the scale placed on the floor. I used 1/4" grade 2 and grade 8 bolts from the same manufacturer to test. I ran my test many times and came up with this: grade 8 took 75# of force to cut and grade 2 took 55# to cut. Since my bolt cutter most likely won't match yours and the number of pounds force to cut through would be different than my results I was wondering if anyone else could try this out. I made sure the bolts were cut at the same relative points away from the threaded area and the bolts were placed in the cutter jaws at the same point each time. Why did UCD get his results? I have never had a drive shaft come loose and I don't intend upon that happening.

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UCD
Woody what are shear pins? they are hardened steel pins I can show you but to try to explain here i have a hard time. I am not that good of a writer. cutting bolts with a bolt cutter and shearing one in a piece of equipment with the bolt torque are two different things there are cheap hardware store bolts. A good quality un graded bolt grade 2 or 3 what ever you want to call them. Then there are hardened bolts grade 5 or 8. My tests come from experience and from master machinists that forget more every day than i will ever know. Plus i am not going to get into an argument over it This & $1.00 might get you a small Coffee Maynard aka/UCD

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SmilinSam
I'm beginning to wonder if there is a paranoia developing around here where people keep reading things between the lines..........when its not necesary......and maybe not even there........ I think most of the machines I get have Grade 2 bolts in the couplers, but cant be sure with all the changes previous owners have made to the ones I get.

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powermax_paul
Maynard & Woody Typically, the stronger a steel specimen is in tension, the stronger it is in shear. The key here may be in the materials' modulus of resilience and/or modulus of toughness. A hardened steel bolt with a higher ultimate tensile and shear ultimate strength will often have a lower modulus of toughness and will shear on sudden impact. This is likely the reasoning behind the use of hardened shear pins (although I've never studied shear pins). The modulus of resilience is the measure of the ability of a material to absorb energy without deforming. The modulus of toughness is the measure of the ability of a material to absorb energy without actually breaking. I agree that it would be better to use a more ductile bolt for these drive shaft couplings. However, if the shaft is not well balanced, a more ductile material can exibit problems with fatigue if there is sufficient number of load cycles. Normally, the way we treat our tractors, that's not a problem. So, actually guys, you're both right, Paul

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Woodydel
Before it becomes impossible to delete my reply please do so. Please make no references concerning me. It was my mistake for joining the discussion and I just want my reply to be removed.

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StanS
The one great drawback to communications in the good ole US of A is the fact that we use the North American version of the English language. Where a pair of shears - cuts and bolts cutters - shear. Assume a 3 foot long pair of scissors, when they're sharp they cut. File their cutting edges down until (in the place of the cutting edge) there is a 1/4 to 1/2 inch wide flat surface. There is no knife edge to perform cutting. Place a bolt in the business end and squeeze like the dickens. No sharp edge to perform a cutting action only two flat surfaces using blunt force to push the 2 halves of the bolt apart. In other words the bolt was broken apart. A harder metal has more tinsel strength, but as nature would have it, it is also more brittle. If it rains, the root cellar floods. If it don't rain, there ain't no food to put in the root cellar. My head hurts. Stan S

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dlcentral
It is a scary sound indeed! Only had 1 break and that was because the rear motor mounts were shot[on a diesel] I would think that with all the garden tractor pulling we do,it would ruin em ,,but so far [knock on my wooden head!] no,,,They have had 2500 plus lbs of weight on them at times quite remarkable indeed,,And most of that weight is a dead pull,not like the weenys,[lol] who use a weight transfer sled where the 1st 50 ft. is load free! ,,

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Dutch
I am of the belief that "shear bolts" are designed by engineers after calculating and measuring the range and type of safe working loads. "Shear bolts" may be made of various materials. Steel "shear bolts" can be grade #2, #5, or #8. Type and grade depends on the load and whether it is vertical, horizontal, or rotary. Here's a chart for adventurous "Do It Yourselfers ". http://www.ggmfg.com/catalog/63.htm Not to be confused with "shear bolts" are mechanical fasteners. In the case of fasteners, "shear strength" is only one consideration, and often that is unimportant. Some automotive engines use a flywheel bolt that actually stretches as it's torqued. Those are "one time" bolts that can never be used again. I believe Kohler also uses that type bolt in some engine rods. In the case of Simplicity driveshaft couplings, I have seen the special "round shoulder" washers installed backwards, or replaced by common "sharp" washers. That is inviting failure. I'm not smart enough to understand all the engineering stuff, therefore, to be safe, I use only genuine OEM hardware on critical components.

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BigSix
Dutch: Just to add to your smorgasboard of different types of shearpins/bolts...the auger (chain) drive "shearbolt" on my early 70's Yardman "Sno-bird" is a hex head bolt, grade unknown (to me) that is very hard to find now, but it is PRE-SCORED. It has two grooves, all the way around, perhaps 1/32" deep, that line up with the OD of the collar it goes through. When inhaling a big chuck of flagstone with the primary (slow-speed) auguer, I found out how that design worked...like a charm--sheared on the score lines, as they lined up perfectly with the OD of the collar on the auger drive, as they were designed to do. When forced to use a bolt that was 1/4" too short, but also prescored, and I swallowed a coblerock, the too short bolt sheared where the collar bit it, not on the score lines, which fell inside the collar's OD, because the bolt was too short. But this obviously took more force than it was designed to, as it was forced to shear the whole diameter of the bolt, not just the reduced diameter where the score lines are. It didn't harm the machine, but I'm sure such overstressing it did it no favors. I mention this just to add to the confusion...I trust it has. Peter

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jlasater
Makes me wonder if a pair of drive shaft hoops like they have on race cars wouldn't be a bad idea. Give 'em about 1" clearance around the drive shaft, and if anything came loose it wouldn't have much room to bang around.

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