Welding hardened steel crankshaft from go kart

admin

Hi,I am new to this forum so a little intro:I'm Rob, 15 and from the UK. I got into engines and welding at about 12, and have made a go kart and mini bike. My problem: my go kart clutch (a comet 40 series torque converter) uses a 1" shaft. The engine shaft was 20mm. I made an adapter. However the clutch and adapter fell off, taking half the keyway with it because the bolt in the end of the crank was loose.I have been running it damaged for a while now, but it seems to be getting worse, so I am going to remove the crank from the 6.5hp honda gx200 clone and fix it. I do not want to spend £40 on a replacement because the engine was £70.My setup: an arc welder with a capability of 180 amps. Its a farmers welder really.What I was going to do: build up the crank and keyway with weld, lathe it back down, mill a new keyway.My questions: will this work? If so what rod shall i use in my arc welder? I am guessin a high carbon one, but what type?I am on a go kart forum,and asked the same question, but i got told I would ruin the temper. Is there anyway i can re temper easily, or not ruin the temper/hardness in the first place? Thanks!Rob
Reply:I would have guessed the basic air-cooled engine would have a cast crank.  Steel/forged cranks are generally stronger, but I'd only expect to find them in a more expensive engine.  If this is a specialized racing engine then you may have a steel crank.If you already have a replacement crank from the gx200 clone and access to a lathe/mill, I would just make a proper adapter and be sure it's installed correctly.I'd also go ahead and try the repair.  The crank is already ruined.  This is a good opportunity to learn something.  However I wouldn't expect the result to be usable in an engine.  I'd probably try using a nickel based rod for the repair. Preheat the entire part and use some method to slow the cooling rate (oven, fireproof blankets, bucket of dry ashes)  I'm no expert in this area, so wait until someone else chimes in.  The only cast iron repairs I've done are brazing cracks in a boat's water cooled exhaust manifold that got frozen.  That had much less mechanical loading than your crankshaft will see.I don't think cast iron will harden or temper.  However, it will crack.  That's what the preheat and slow cool down are trying to prevent.  If the part isn't uniformly hot it will expand more in some areas and less in others.  This makes internal stresses and can cause cracks.Dynasty200DX w/coolmate1MM210MM VintageESAB miniarc161ltsLincoln AC225Victor O/A, Smith AW1ACutmaster 81IR 2475N7.5FPRage3Jancy USA1019" SBAEAD-200LE
Reply:I would not weld it.  You risk it getting brittle and breaking off.  It will also be too hard to machine.  Brazing is a good option. Here's one I did.http://weldingweb.com/vbb/showthread.php?t=38918My name's not Jim....
Reply:It is possible that the crank was cast and then put through a heat treating process to change it to "malleable" iron, but it also might be ordinary steel. If you have the broken-off part, you could slowly heat it to high redness, cool fairly quickly (not quench) and then test it. If it has reverted to being cast iron, it should break rather than deform when squeezed in a strong vise. If low carbon steel, it will deform 'easily' but if high carbon steel (unlikely), it will be hard but should not break. Do you have any scrap material of various kinds (cast, forged, rolled) you can apply these tests to and then practice on first?Once you think you know what material it is, then post what you have available to use; for example, is high nickle (Ni-99) rod available to you? Over here, most of the engines I've had turn Clockwise; is it true that over there, most go Cclockwise ('backwards')? Might require running beads from right to left if so. BTW,   ... My area once got invaded by british Beetles....
Reply:The crank is cast iron and NOT hard at all..This is a adaption I did for a diesel engine going into a snowblower and it worked out GREAT!!The diesel shaft was tapered and the original pulley is straight bore..Rather than try to match the angle this is the cure and this will work for what you are doing..Study the pics and seeing as you have a lathe and mill you should be able to do this also..This is from another site so I just copied and pasted the procedure..OK here we go..Pic 1 is the Crankshaft after turning the end..Finish size .691Pic 2 is the bushing finish inside size .687...OD left .030 over for finishing..Pic 3 is the bushing and crank ready for the heat/install..Pic 5 is the red hot bushing installed..I did not pin the bushing because the shaft size was so small and we don't need any weak spots..If you can turn the OD without it spinning then all is well.. clapNext post.....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:Pic 1 is the bushing ready for finishing in the lathe..Pic 2 is the finished bushing with a 1/4" keyway cut in it..Pic 3 is a Custom Key...010 smaller than the width..INSTALL MARKED SIDE UP!!!Pic 4 is the finished assy..Pulley is within .002 of the crank..This will work and it's not that difficult to do..Some of the pics are not in order but you should be able to figure this out..Sorry about that!...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:Wow! What a good forum!Replies:@ Andy A: This is pretty much a generator engine so it probably does have a cast crank. It has casting marks on the weighs, and the bit that fell off had a rough “cast” looking finish. I don’t know if this means anything.I could preheat and weld with a MIG at school because I do not have any good heating kit at home except from a little butane torch.I do not take failure as an option- this crank is being repaired! The motor is only worth £100 so if I needed a new crank I would probably just buy a new motor and sell the old one for parts (or the new one and keep the crank.)@Boostinjdm: Very nice job! However, unfortunately my crank is a little over .020 undersize- probably about .100 where it is damaged. Also I don’t have access to a tig. Do you think I could do similar with standard steel wire in a MIG?Is that a gx200 clone, or another clone? If so, you may know the answer to Oldiron2’s question.@Oldiron2: I don’t know what material it is. Maybe I should contact Honda? It was pretty brittle because it came off in little chunks. I will see if I can find any of the pieces. Oh and to answer your question, the motor spins CCW! However this engine runs the same way in every country- weird huh? @Zapster: Thanks for the pics- very informative! I like the idea. Would the sleeve just slide on, or would it need a press? Also, would it really not turn? Knowing my luck I could see the whole sleeve turning- Maybe I could put a small keyway in the turned down crankshaft and in the sleeve, to stop the possibility?  Also, how would I go about getting the finish on the crank shown in pic2?Another thought I have had is to machine down the crank until it is good, then put a keyway in and then put a sleeve from the crank size to 1”, and miss out my current sleeve. This poses two problems though-1. The crank may snap off from being such a small diameter.2. I could not re sell the motor for as high a value, if I needed to.Thanks for your awesome replies!RobLast edited by r_chez_08; 11-19-2011 at 12:58 PM.
Reply:Originally Posted by zapsterThe crank is cast iron and NOT hard at all..
Reply:Originally Posted by BoostinjdmYou are correct up until he tries to MIG it.  I attempted one about three days ago.  Where the weld meets the crank got harder than hell.  That's also right by the bearing where most of the stress is at.The crank in my thread is out of a 13hp clone.  You could braze it with a torch.
Reply:r-chez------ a picture would be worth a thousand posts then we all could see what your up againstmaybe a simple fix or more complexedWEEEEEE need pics  man  need pics lolidealarc 250/250 ac-dc tigidealarc 250/250 ac-dc tig #2 used for sticklincoln sp100hh125dual arbor grinder polisher30 yrs of hand tools52 pitch blocks 6p-26prake gauge -pitch gaugeG&D prop repair 918-207-6938Hulbert,okla 74441
Reply:I'm liking zap's approach for the ease of use and probability of success.The resale value on the motor will be better than in it's current state.The concern about the turned down shaft being weak is valid.  How far would to have to turn yours down to clean it up?If you size the sleeve correctly for an interference fit and then install it hot, it will not come off.  In fact you'll probably be cussing if ever wanted to take it off.Dynasty200DX w/coolmate1MM210MM VintageESAB miniarc161ltsLincoln AC225Victor O/A, Smith AW1ACutmaster 81IR 2475N7.5FPRage3Jancy USA1019" SBAEAD-200LE
Reply:Originally Posted by r_chez_08Wow! What a good forum!Replies:@Zapster: Thanks for the pics- very informative! I like the idea. Would the sleeve just slide on, or would it need a press? Also, would it really not turn? Knowing my luck I could see the whole sleeve turning- Maybe I could put a small keyway in the turned down crankshaft and in the sleeve, to stop the possibility?  Also, how would I go about getting the finish on the crank shown in pic2?Rob
Reply:Originally Posted by Oldiron2Over here, most of the engines I've had turn Clockwise; is it true that over there, most go Cclockwise ('backwards')? Might require running beads from right to left if so. BTW,   ... My area once got invaded by british Beetles....
Reply:Crap- what happened to my reply?The crankshaft would need to be around .500 in order to remove all the damage, and to allow for a full size keyway in the sleeve. However, there is a .315 tapped hole in the end of the crank to secure a clutch, which would leave around a .092 wall on the shaft. This sounds very weak!My other option is to make a sleeve .496 i/d and 1.030 o/d then machine it to 1". Would this be stronger?Otherwise I will probably crank up the arc welder and give it some...
Reply:Originally Posted by r_chez_08Crap- what happened to my reply?The crankshaft would need to be around .500 in order to remove all the damage, and to allow for a full size keyway in the sleeve. However, there is a .315 tapped hole in the end of the crank to secure a clutch, which would leave around a .092 wall on the shaft. This sounds very weak!.
Reply:Ok thanks. I will probably do this, i just need to decide whether to go 3/4" with an adapter or 1" without. Of course 1" would be stronger, but 3/4" is more versatile should the engine be use for something else in future.Argh. I can't decide!!!Would I want the sleeve .004 smaller internally than the crank like you did, or is there a formula? And also how did you get that finish on the crank?ThanksRobP.S. Failure is NEVER an option.
Reply:What runs off the snout of the crank? Or is it just a pulley? If theres no timing gears or anything why dont you just machine another keyway slot?HTP Invertig 201Lincoln Idealarc SP250Miller 180 AC StickBy farmall:They should have held the seagull closer to the work, squeezing evenly for best deposition.
Reply:Originally Posted by r_chez_08Hi,I am new to this forum so a little intro:I'm Rob, 15 and from the UK. I got into engines and welding at about 12, and have made a go kart and mini bike. My problem: my go kart clutch (a comet 40 series torque converter) uses a 1" shaft. The engine shaft was 20mm. I made an adapter. However the clutch and adapter fell off, taking half the keyway with it because the bolt in the end of the crank was loose.I have been running it damaged for a while now, but it seems to be getting worse, so I am going to remove the crank from the 6.5hp honda gx200 clone and fix it. I do not want to spend £40 on a replacement because the engine was £70.My setup: an arc welder with a capability of 180 amps. Its a farmers welder really.What I was going to do: build up the crank and keyway with weld, lathe it back down, mill a new keyway.My questions: will this work? If so what rod shall i use in my arc welder? I am guessin a high carbon one, but what type?I am on a go kart forum,and asked the same question, but i got told I would ruin the temper. Is there anyway i can re temper easily, or not ruin the temper/hardness in the first place? Thanks!Rob
Reply:Originally Posted by fordmanWhat runs off the snout of the crank? Or is it just a pulley? If theres no timing gears or anything why dont you just machine another keyway slot?
Reply:Mega waste of time. Buy a replacement crank and move on with life. They're usually about $70 online.Welding/Fab Pics: www.UtahWeld.com
Reply:Originally Posted by MikeGyverMega waste of time. Buy a replacement crank and move on with life. They're usually about $70 online.
Reply:Originally Posted by r_chez_08It is a variable pulley. I could machine a keyway in the other side, but it probably would be weaker, and while the crank is out, I would like to do a good job.Ok I will not weld. I will try and get pics, because they will help a lot. One question: I have access to liquid nitrogen. Would it be better to cool the shaft than to heat the sleeve? I may even be able to do both.Thanks
Reply:Awesome ok thanks. I will probably get round to doing this in a few weeks, if not I will do it in january.Oh and will an oxyacetaline torch be ok for heating? and will mild steel be ok for the sleeve, or should I use silver steel?Last edited by r_chez_08; 11-20-2011 at 09:20 AM.
Reply:That will be plenty..Just get the whole thing RED hot and all will be good....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:Awesome thanks  I will be back with pics when I start doing this.I'm impressed that a 15 year old is as knowledgable as you are, very cool.
Reply:I'm impressed that a 15 year old is as knowledgable as you are, very cool.
Reply:How deep is the threaded hole?...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:17mm according to honda, although it may be different. I need a way of removing the threaded bar...
Reply:Since welding this is a hit and miss and you have a machine shop background why not cut a new keyway opposite this one and re-key the clutch???  It won't be quite as strong but this time keep the bolt tight and maybe lok-tite the hub to the shaft.  You could maybe use a smaller keyway and use a tool bit for the key.  Still the crank will be weaker but it is a fix.Start looking/saving for a new crank.
Reply:Take the crank out of the engine then heat the shaft around the threaded piece red hot and the threaded piece will come out easily..The metal expands when heated and the rod will not get as hot as fast..As soon as the hole expands it should come out.....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:Ok, well I wont be taking the crank out for a week and a half, because I have mock GCSE examsnext week. I will try and save this crank. No harm in trying! Why wouldnt the heat shrink method be a permanent fix?
Reply:Found out my bearing is .9825 +/- .002Unfortunately this means that I have to have a 3/4" crank not a 1" crank. Would .500 be strong enough for the crank before I put the sleeve on?I was also considering putting a small (3/32 or so) key in holding the sleeve and shaft together. Is this neccesary? Or would it hold fine without?I would then put a 3/16" key in the sleeve and have a 3/4" to 1" adapter sleeve with 2 keyways (one for clutch, one for shaft.Edit: went to take some measurements. I got the threaded bar out- two nuts one backed up against the other.The hole is more like 1 1/4" deep.The shaft would have to be 13.5mm or under to remove all damage. However, I need 2.7mm for a keyway, so 19.05-2.7 -2.7 =13.65mm. Then I would need a little bit of material to stop the keyway going all the way through the sleeve, so lets say 12 -12.7mm for the shaft. Would this be enough? Thanks(sorry for the metric/imperial, I am use to working with both, bad habit!Last edited by r_chez_08; 11-20-2011 at 04:19 PM.
Reply:Spoke to the DT technition at school today. He said that zaps method would only hold up if the key was in the original crank as well as the sleeve, like Zap has done. However, my original key is damaged. Is there not any material that I could just fill the damaged crank in with, so Icancut a keyway on the other side? I thought JB weld, but then I realised how brittle it is.Could I not just braze the shaft or use another technique to fill the shaft in apart from welding?
Reply:That's what I was going to suggest. Just braze the shaft up and turn it back to size and cut a keyway 180 deg from the original.  You might consider cutting a smaller keyway on the shaft then make a special key to fit both the shaft and hub.
Reply:Would "normal" brazing be ok on the shaft, or do I need Si bronze?I would have far more trust in a key in the solid shaft than a key in a sleeve held on by friction.
Reply:Spoke to my DT technition today. He said that to braze you still need to get the shaft very hot. Why can you braze and not weld?ThanksRob
Reply:Originally Posted by r_chez_08Spoke to my DT technition today. He said that to braze you still need to get the shaft very hot. Why can you braze and not weld?ThanksRob
Reply:Ok that makes sense thanks. How does the braze adhere to the parent material then? And do I need the silicon bronze or would a brass rod be suitable?ThanksRob
Reply:I decided on the sleeve method. I removed the crank last weekend and I have turned the damaged part to .500 +/- .0005 i am currently making a sleeve .496 I/D
Reply:Thanks for all the help, especially Zap!I think it worked.I made the shaft .500 and the sleeve .495 +/- .001I heated it red hot and used a heavy hammer to thump it on- it only just went, I thought it had got stuck half way!!!Pics show crank with 30mm turned down, sleeve, red hot sleeve and the sleeve on the crankshaft.Oh and here is a before pictureAll I need to do now is turn it all to .750 and cut a keyway Thanks for saving me £35!Edit: sorry for the quality of the latter pictures, schools cameras are worse than my £25 samsung one! Attached Images
Reply:It will be OK...you'll see..Keep the pics coming!...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:.Looks Good!Regarding the camera, if you look at picture 3, you see that the can is in focus; the camera didn't and perhaps can't focus as closely as your part was. Most cameras have enough resolution at the highest setting to shoot from farther away, then crop it and enlarge the part you want before attaching it here.
Reply:Man, I am glad to see a 15 yo. doing something hands on besides a dam game controller.Good communication skills too.Tim Beeker.
Reply:Thanks for all the positive comments! I finished the crank today What I did:1. Lathed damaged section of the crank to .5002. made a sleeve .496 i/d x 20mm o/d3. heated the sleeve red hot. Smacked it bloody hard onto the crank4. filled in the key left on the crank with weld because it was damaged from the key rocking side to side5. spent the past week cussing the above- the mig welding wire I used was very hard! I used an angle grinder, tipped tool on a lathe, a file and a toolpost grinder to get the weld down to size.6. I now had a crank that was a fraction of a hair under 1"7. I used an end mill and an "X" block with a 3/16" cutter to cut a new keyway, on the opposite side from the old one.I am pleased with the end result. Aesthetically, it doesnt look that bad, and you can only just see the weld, and the edge of the sleeve. TBH though who gives a **** what it looks like, as long as it works! Only time will tell, but I think I may have saved my self £40.I have recieved a new gasket kit and a flat top piston for the motor. Unfortunately it is for a gx160 with a slightly longer (3-4mm) skirt. How would I go about shortening it? @Oldiron2: yeah you are right, my little camera doesnt especally like macro photos that much either. I usually take the pics from further away and zoom in.Oh and tnjind, I get bored of comuter games, when I know I can be making Here are the pics:http://diygokarts.com/vb/attachment....0&d=1323294697
Reply:sorry for the multiple posts, the edit button seems to have dissapeared on the above posts???
Reply:Originally Posted by r_chez_08sorry for the multiple posts, the edit button seems to have dissapeared on the above posts???
Reply:How about cutting off the excess skirt, then add some width with either aluminum spot welds at the skirt lips, or some of those cool nylon looking skirt buttons?  Gotta be some way to eliminate the piston slap at the skirts.Miller Syncrowave 350Millermatic 252/ 30A spoolgunMiller Bobcat 225g w/ 3545 spoolgunLincoln PowerArc4000Lincoln 175 Mig  Lincoln 135 Mig Everlast 250EX TigCentury ac/dc 230 amp stickVictor O/AHypertherm 1000 plasma
Reply:What a great tread. Not only a top result, it was done without any bitching.That must be a first
Reply:Spoke to some people on a kart forum. They know so much about this motor!Here is a link to the results, i cut the piston.http://karting.4cycle.com/showthread.php?t=409633