welding on crankshaft

admin

a year or so ago i built a longtail mud motor.  since then i have rebuilt just aboiut everything on it, and theres really only one thing left wrong with it.  the engine i bought is a tecumseh 11 horse with a tapered crankshaft.  i currently have the u-joint bolted onto the crank, but the bolt snaps after about 10 minutes of use, not even in water.  im thinking about welding the crank and u-joint together.  i wont haver a problem when i have to replace seals on the driveshaft or anything.  my biggest concern about welding it isA) vibrationB) i REALLY dont wanna take the motor apart, is there anyway to weld on the crank w/o burning the rear main seal?
Reply:You won't want to weld to the crank anyway..It's cast not steel.....zap!I am not completely insane..Some parts are missing Professional Driver on a closed course....Do not attempt.Just because I'm a  dumbass don't mean that you can be too.So DON'T try any of this **** l do at home.
Reply:OH gee... why did i not think about that... (not being sarcastic)soo.. any suggestions?
Reply:Posted by fishon91:  soo.. any suggestions?
Reply:No doubt you're talking about this one http://weldingweb.com/vbb/showthread.php?t=33997.You could get a yoke with no hole (or smaller hole than needed) and have a tapered bore cut to fit the crank if one with the proper taper isn't available (would likely have to be ordered).You said you didn't want to take the motor apart but if you did, you could have the crank snout turned down to a straight round but I suspect that would weaken it to the point it would fail due to the side forces of the excessive joint operating angle I pointed out in your other thread.You could have an adapter made (tapered ID and straight OD).  ??MM200 w/Spoolmatic 1Syncrowave 180SDBobcat 225G Plus - LP/NGMUTT Suitcase WirefeederWC-1S/Spoolmatic 1HF-251D-1PakMaster 100XL '68 Red Face Code #6633 projectStar Jet 21-110Save Second Base!
Reply:I'm all over duane's advice re; angle on the u-joint. At small motor speed there are real problems from the output shaft going thru 4 accell/decell's per rotation. I would pretty much look to keep the angle less than 12 degrees for one joint and 15 is a deal killer.The vibration in a very short time is going to fatigue everything around it.Matt
Reply:Originally Posted by fishon91 tecumseh 11 horse with a tapered crankshaft.  i currently have the u-joint bolted onto the crank, but the bolt snaps after about 10 minutes of use
Reply:u-joints need to have a second u-joint on the shaft or use a constant velocity joint to get rid of vibration.
Reply:Originally Posted by boatbuoyu-joints need to have a second u-joint on the shaft or use a constant velocity joint to get rid of vibration.
Reply:Originally Posted by duaneb55No doubt you're talking about this one http://weldingweb.com/vbb/showthread.php?t=33997.You could get a yoke with no hole (or smaller hole than needed) and have a tapered bore cut to fit the crank if one with the proper taper isn't available (would likely have to be ordered).You said you didn't want to take the motor apart but if you did, you could have the crank snout turned down to a straight round but I suspect that would weaken it to the point it would fail due to the side forces of the excessive joint operating angle I pointed out in your other thread.You could have an adapter made (tapered ID and straight OD).  ??
Reply:I don't think you need to worry about keeping the engine level. I have an old troy bilt horse tiller and when I have it sunk in the ground all the way the B&S engine is at a heck of an angle. I'm talking the output end of the crank pointing down at a very steep angle. It doesn't seem to bother it and I've read on other forums of guys mounting the chinese clone engines on these same tillers and they seem to work fine. I think you could just get rid of the u-joint, have an adapter made and go for it.                                               JMHO,                                                            MikeOl' Stonebreaker  "Experience is the name everyone gives to their mistakes"Hobart G-213 portableMiller 175 migMiller thunderbolt ac/dc stick Victor O/A setupMakita chop saw
Reply:thats the best pic i got of it right now.  ive got a separate gas tank and a whole new shaft.  the shaft is doen the same way, but right...(er).  and the throttle setup works a LOT better.  if i woulda known i could get a tapered yoke i wouldaq definitely done that, but i cut the taper off of the crank so it'd fit.  im atry this turbocad out some to see if i can get a good illustration of what exactly i got goin on.  i may replace the motor next summer, but right now i need something to make it last till then.
Reply:this is how it is now, and with the bolt being too weak
Reply:It needs to be a very close fit with a key.  You will also need the prop shaft to move in and out a little.  IF it is fixed with no play then it will shear the bolt more quickly.  The U-joint pushes and pulls the shaft in and out as it rotates.You can't just slap some parts together.  This stuff can be turning at 3500 rpm and needs to be precise.My name's not Jim....
Reply:ive ,made calls to some local machine shops a while back and i'd have to tear the motor down to get a keyway cut.
Reply:If you have all the gaskets handy, pulling the crank out is a piece of cake.  Look up the torque specs for the side cover, rod, and flywheel nut ahead of time and make sure you have the correct tools.My name's not Jim....
Reply:How did you cut the taper off the crank?My name's not Jim....
Reply:bandsaw, nothing machined, just cut it. but i figure if everything else is balanced, that little bit shouldnt hurt anything
Reply:Oh jeez....  Was there a straight portion of the crank before the taper?My name's not Jim....
Reply:Was it like this one? http://www.smallenginewarehouse.com/...OH318EA-221712My name's not Jim....
Reply:yup, almost exactly
Reply:I suspect you are going to be fighting this thing all along.  There are several ways you could go, but the cost is going to start adding up.  Might be easiest to find a replacement crank.  One that is at least 1" in diameter.  1 1/8" or 1 1/4" would be even better.  The larger it is, the less likely the key will get sheared off.  If you don't like that idea then I suppose you could look into taper lock hubs and having a keyway cut in your current crankshaft.  I seem to remember the taper lock hubs costing over $50 per half though and you would still have to adapt the yoke to it.My name's not Jim....
Reply:Yup you deff need a CV style shaft. Look and see if maybe you can adapt a front drive shaft out of a jeep cherokee or grand cherokee. --Gol'
Reply:I think a companion flange solution would be the quickest. You can buy the flanges from someone like these folks with a straight bore; http://www.pssupply.com/compflange.htmlThe flange can be machined for a slight interference fit for the crank end and a driving key can be done with a dowel inserted in a hole drilled and reamed from the crank end after assembly. The hole is drilled along the bore/shaft line, the dowel cannot be the hardened type or the split spring pin type. This can be done by hand if carefull, a drill will follow the split line between the bore and shaft pretty well. It's nowhere near as good as a woodruff key would be though.You will need a set screw over the round key and usually another set screw is placed at 90-120 degrees from the key.Companion flange yokes are pretty common for automotive use, a simple one below;Matt Attached Images
Reply:i think i get what youre sayin, pretty much just use a small peice of round stock for a key instead of square. if thats the case then i could do that to the setup i got now. if thats the case then i got 2 more questions:1) should i have to worry about the hole through the crankshaft that i already got?  it definitely weakens that crank but with the hole not being filled with a bolt should it throw off balance too badly?2) would it be ok to put two round keys in opposite of eachother? just to make it stronger and maybe better balanced?i suppose set screws can go through the u-joint, one is already drilled and tapped, just need one on the other side (if i was to put two keys in it).FishOn - I'd suggest that you definitely should at least start with a Taper-Lock hub on the shaft, but I can't grasp enough of the rest of the details to make a further suggestion.Good Luck
Reply:denrep, if ya look at post #13 of this thread, that is how i have it set up now. ive looked online, and ill keep looking, but im not quite sure what a taper-lock hub is. sounds like something i woulda used before the taper was cut off, but now the crank has no taper. hope that helps.btw, thank yall lots for your help, sorry if I dont understand everything, I"ve taken this project on without too much mechanical knowledge and there hasd been lots of lessons learned along the way.  I just knew what about I wanted to do and started doing it, I can start to see it becomin a fully reliable motor one day and yall have sure helpes lots with that.  Building things like this is a major passion of mine and I've always had great respect for people that do that.  thanks again yall.
Reply:Originally Posted by fishon91i think i get what youre sayin, pretty much just use a small peice of round stock for a key instead of square. if thats the case then i could do that to the setup i got now. if thats the case then i got 2 more questions:1) should i have to worry about the hole through the crankshaft that i already got?  it definitely weakens that crank but with the hole not being filled with a bolt should it throw off balance too badly?2) would it be ok to put two round keys in opposite of eachother? just to make it stronger and maybe better balanced?i suppose set screws can go through the u-joint, one is already drilled and tapped, just need one on the other side (if i was to put two keys in it).
Reply:A Taper -Lock fitting has a partially split inner ring having a cylindrical inside to fit over the shaft and having a tapered outside surface. A  'solid' ring with a tapered inside fits over the inner ring and the two are pulled together (moving in the direction of the shaft axis) by bolts which thread though the outer collar and into the inner ring, again parallel to the shaft. This provides a tight compression fit of the unit on the shaft. The inner ring has a keyway  to align with a key in the shaft keyway, this providing resistance to the fitting creeping on the shaft while under load.A Google search should be able to find a diagram of one, but I don't have the time right now.
Reply:so i understand now most of how the taper-lock works. but if i was to get a taper-lock i still have to get a keyway cut on the crankshaft.if i get a keyway cut then i can use the same setup i have now, without all that taperlock stuff.  im tryin to stay out of gettin a keyway so i dont have to tear the motor down. im in college in a rent home and tools are spread out between here and my parents. i only have very basic handtools, a drill, drill bits, and most of a racheting wrench set.
Reply:Taper-Lock doesn't drive against the key. The key is used locating and as a stop should the hub begin to  "walk" for whatever reason, as OI2 mentioned. This assembly would go together and drive fine without a key.  If it begins to walk, there are ways to deal with that without a key.The problem with a non-locking slip-on coupler is that with one or two more times running  loose the crank will probably be history.Once a Taper-Lock type is selected, that will open up many options for the rest of the coupling.God Luck
Reply:alright now just a matter of finding one to fit and adapt to the yoke