Tig Si Bronze on crankshaft.

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I've got a small engine, it's a clone.  I want to use it on a go-kart/ buggy type of toy I've been tinkering with for a long time.  Anyways, the crankshaft is about .020 undersized where the clutch mounts.  I have to turn a shoulder down on it anyways, so I figured maybe I could weld up the shaft and  turn it back down to size when I cut the shoulder back.  That way I get a nice fit with the clutch.Pre-heating evenly is going to be a problem and filler for a mystery material confusing. So today I picked up some silicon bronze TIG filler thinking I would give that a shot.  Providing I don't damage the crank, the filler is more or less a permanent shim.  If ya get what I mean.Does this sound like a reasonable idea?  Any tips before I get dug in?  I've never used Silicon bronze before, so in that respect I'm a newb.My name's not Jim....
Reply:I assume this section projects from the engine and needs to be axially correct. Have you considered turning the shaft down slightly more, and heat-shrinking a collar on? It might be less work, about as strong, and keep things straighter too.Building up by spraying would also be nice, but requires equipment I assume you don't have access to.
Reply:Having no personal experience, I feel pretty confident saying your best bet is pre and post heating and using a nickel rod. Don't know how silicon bronze is going to work but whatever you do I would probably still pre and post heat the crank.
Reply:I would keep the welding part away from the crank..10 to 1 says the crank is cast iron..Why not turn the area down say 1/4" more on the O.D.and shrink on a sleeve with .005 press..Trust me it will not go anywhere.....zap!Last edited by zapster; 02-23-2010 at 06:01 PM.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:I vote for the sleeve also.
Reply:Posted by me above:Have you considered turning the shaft down slightly more, and heat-shrinking a collar on?
Reply:Sleeve..Collar....All the same to me..I did just that for a gentleman next door a few weeks back..http://weldfabzone.com/forum/index.php?topic=3084.0Sorry I did not read your post Oldiron or I would have quoted ya.....zap!Last edited by zapster; 02-23-2010 at 06:25 PM.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:Posted by the Esteemed Zapster!Sorry I did not read your post Oldiron or I would have quoted ya..
Reply:I could sleeve it, but it's got a full length keyway.  Maybe another route would be to counter bore the clutch for the shoulder and then just use shim stock to take up the .020".  I wouldn't even have to get into the engine then....My name's not Jim....
Reply:I have done a few of those, my brother had a small engine/lawn and garden shop. In the past I OA brazed shaft and turned to size. Now I use sil bronze tig. A word of warning, do NOT make a puddle then add filler. Resulting weld will be hard, too hard to machine properly. Lay rod on shaft and start arc on rod. This will melt ball which will only lay on top of shaft. Keep arc going, after a few secs it will flow out. Keep arc on bead and add filler as it flows out. Practice on a like shaft that is junk, use file to test hardness.I am assuming shaft is out and you have lathe.Peter
Reply:I could sleeve it, but it's got a full length keyway. Maybe another route would be to counter bore the clutch for the shoulder and then just use shim stock to take up the .020". I wouldn't even have to get into the engine then....
Reply:Originally Posted by castweldI have done a few of those, my brother had a small engine/lawn and garden shop. In the past I OA brazed shaft and turned to size. Now I use sil bronze tig. A word of warning, do NOT make a puddle then add filler. Resulting weld will be hard, too hard to machine properly. Lay rod on shaft and start arc on rod. This will melt ball which will only lay on top of shaft. Keep arc going, after a few secs it will flow out. Keep arc on bead and add filler as it flows out. Practice on a like shaft that is junk, use file to test hardness.I am assuming shaft is out and you have lathe.Peter
Reply:So Peter.....now that I know you have done what I am wanting to do.  Can you tell me how to setup for the sil bronze?  DC- or AC or what?  Like I said I am new to this.My name's not Jim....
Reply:Originally Posted by BoostinjdmSo Peter.....now that I know you have done what I am wanting to do.  Can you tell me how to setup for the sil bronze?  DC- or AC or what?  Like I said I am new to this.
Reply:Thanks again.  I'll see if I can get a bad crank to play with.  As far as the one I've got, it's mystery metal.  Like I said earlier, it's a clone.My name's not Jim....
Reply:Most crankshaft repairs are done by metal spray.  I would be weary of a sleeve because it weakens the crank.  Then again, .020" isn't much.  If you're going to go through the trouble of getting a bad crank, what about the trouble of getting a good crank?Do you ever plan to remove it?  Loctite retaining compound works well.  I've used 609 to attach things to undersized shafts in the past.  In fact, I've worked places that use it in place of interference fit of new parts during assembly to save money/time (shaft sleeves, mostly).  I can't remember what the gap filling properties of 609 are, it's either .005" or .010".  If it's .010", you're good to go.I have also seen driven components welded directly to the shaft (flywheels on air compressors), and shim stock wedged in the gap to take up clearance.  These bits of machinery have run for thousands of hours with these half-assed repairs.Last edited by 76GMC1500; 02-24-2010 at 02:15 AM.
Reply:silicone bronze is usually done DC, really it's very easy wire to work with.  as mentioned don't form a puddle on the base material, strike an arc and let the bronze wire melt.mystery crank is most likely cast iron.  Nickel rod can be used as well but Si Bronze is easier to work with. Make sure the base metal is cleaned very well
Reply:Sleeve it? Better have sharp tools, patients, time, and free machining material to fab a sleeve with a .020 wall. Then cut a key slot in it? You will have an open ended ,thin,flimsy bushing.Spray weld? Good choice but I don't think Boost has a spray rig?OA braze w/low fume bronze would probably be best choice.TIG braze would be great also but this will be his first job with this process. Easier to goof up than OA.Crank is either steel or nodular iron (cast).Boost if you are worried about brazing keyway- get plain carbon arc rod, with razor cut and peel copper off, use coarse sandpaper to sand to key shape and put in keyway. nothing will stick to it.Weld it!Chuck flywheel end, run opposite main in steady, machine welded end. This will true any runout from welding.Or box that baby up and shoot it my wayPeter
Reply:Not worried about the keyway, I can fix that with a file if I have too.  I was thinking that Tig brazing would put the least amount of heat into it.  I just don't want to weaken the shaft any because it and the clutch will be only inches away from me in my little buggy.  That clutch could do a lot of damage if it came loose or the shaft broke.I did price a replacement crank and it was cheaper than having this one welded and ground at a local shop, but who knows if it will be undersized or not.  This thing being a cheap clone was undersized right out of the box.  I figure if I can tig braze it myself and have a shop turn it down, it will be cheaper than a new crank and I know it will be the right size.  Only out of pocket cost is the tig wire and half an hour or so of machining.My name's not Jim....
Reply:Posted above by Castweld:Sleeve it? Better have sharp tools, patients, time, and free machining material to fab a sleeve with a .020 wall. Then cut a key slot in it? You will have an open ended ,thin,flimsy bushing.
Reply:Originally Posted by Oldiron2Boostin;Do we get pictures?[/CENTER]
Reply:Originally Posted by Oldiron2Peter, if he had his own lathe, he could just clean it up enough to silver solder on a piece which fits well but is oversize on the outside, then turn that down to whatever size he needs. It is easy to get a thinnnn sleeve that way, so long as the crank will take the solder well. The sleeve can be bored first and the crank turned second to get the exact solder  fit required. Re-cutting the keyway through the thin, finished sleeve can even be easily done with hand tools, if needed. Since he doesn't have a lathe,......the TIG brazing w/ Silicon Bronze should be fine. FWIW, I have gotten carbon to use for filling holes and keyways from  old DC motor brushes, or as sample EDM material from Industrial shows. Ground up charcoal (Charcoal isn't as temperature resistant as graphite, but does still work) mixed with a little Sodium Silicate, or maybe even some Elmer's Glue, and made into an extra-super thick paste/plastic mass can even be used; it needs to be dried before welding, of course. Mixing can be tedious though. Boostin;Do we get pictures?
Reply:Originally Posted by castweldAnd I want to see pics also.
Reply:OK, progress today.....Tear down engine, tig crank, machine crank, re-assemble engine with pulse port added for fuel pump, set valves, compression check, install clutch, take pics for those greedy bastards on WeldingWeb....Oh, and the shoulder machined like steel bar stock.  I was able to pull ribbons off of it instead of little chips like some of the cast stuff I have worked with.It took me a little while to do, but I got it done and spent $10 or less.  I think I'll chalk it up as a win.  Here's the pics.... Attached ImagesMy name's not Jim....
Reply:Great looking repair.Well there you go.Looks good.Peter