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Thoughts on crankshaft welding/ engine block welding


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  #1  
Old 04-12-2008, 10:40:55 PM
Mac Leod Mac Leod is offline
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Default Thoughts on crankshaft welding/ engine block welding

hi, I am working on a Tecumseh two stroke engine (model 1572). The crank shaft is damaged on the output side. there were threads on it for a clutch for a chainsaw, these have had a grinder taken to them <some one tried to adapt this engine to something else and did a poor job.> I would like to have the crank welded up and ground down. the crank rides on ball bearings and the rod is on needle bearings. I would like to have the shaft made to 5/8 inch (it is ground to about 1/2 inch or les in some spots.)---does any one see any troubles with having the crank built up this way? could weld be used to increase the length of the shaft (1/4-1/2 inch?)

The second part is the engine block, where the crank sticks out from the block, there are a a few chunks missing from the flange around the crank. the flange held a snap ring that held in a seal for the crank. the aluminum looks like it may be porous. any thoughts on having it welded

Thank you for your input

Mac Leod
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Old 04-12-2008, 11:07:32 PM
Kevin O. Pulver Kevin O. Pulver is offline
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Default Re: thoughts on crankshaft welding/ engine block welding

Mac,
Doubtless others will say it can't be done. A very skilled and knowledgeable welding shop could do it. But I doubt it's worth it. If you want to do it, go for it. Kevin
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Old 04-13-2008, 12:01:36 AM
Delco 32 Volt Delco 32 Volt is offline
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Lightbulb Re: thoughts on crankshaft welding/ engine block welding

I believe I would turn the crank shaft true (round) and make a shaft the length needed and bore to fit crank shaft then silver solder. Then turn and polish O.D. to 5/8" Steve
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Old 04-13-2008, 02:22:30 AM
bill chasser bill chasser is offline
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Default Re: thoughts on crankshaft welding/ engine block welding

Mac Leod

Regarding the crank. A good crank grinder can machine the pto shaft down and then bore and press a new peice of stock onto the remainder, weld the end of the new stock onto the existing crank and remachine the stub to any spec you need. I am currently doing this to save 7 Salsbury scooter cranks that had been modified for other uses. It is easier than you think and the result will be more than satisfactory. If you have further questions regarding this PM me.

Can you show pics of what you are working on and the damage in question. I can't visualize the block issue since I don't know what you have to work with. If it is aluminum a competent welder can Tig in material and the bore and snap ring groove can be remachined. Anything can be repaired if you have cubic dollars and the part is worth the repair when finished. Its all relative to your needs...

Bill
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Old 04-13-2008, 11:18:34 AM
Mac Leod Mac Leod is offline
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Default Re: Thoughts on crankshaft welding/ engine block welding

Heres a picture...how strong would the sleeve be if it is welded on (seems like where it is welded would be a good spot for the shaft to sheer)

I think welding it up and grinding down is the best option but I would like as much input as possible for both the crank and block

Thanks

Mac Leod
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Old 04-14-2008, 09:28:03 AM
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Craig DeShong Craig DeShong is offline
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Default Re: Thoughts on crankshaft welding/ engine block welding

Mac
I may be mistaken but the ball bearing is going to take all the crankshaft loading and the exterior flange appears to just hold an oil retention ring. If this is the case, a little locktite may hold the oil ring in place and you could probably build-up the flange with something like JB weld ? Am I completely off base with this ?

I can't talk about the crank but Bill Chasser is a Salsbury scooter guy who I believe has a lot of experience with these type of restorations so I would think his reccomendation would be at least one positive way to go.
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Old 04-14-2008, 09:39:20 AM
Mac Leod Mac Leod is offline
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Default Re: Thoughts on crankshaft welding/ engine block welding

Craig, you are correct, the oil seal has a retaining ring, even with all the metal missing, the retaining ring hold just fine. it is mostly a cosmetic repair. If the engine was going to be painted I would have used jb weld but the engine will be left raw aluminium, the jb weld will stand out way too much.
I am kind of afraid of what it is going to cost to have the crank and block fixed unfortunately I can not locate another crank shaft so the only option is to repair that one

Thanks

Mac Leod
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Old 04-14-2008, 03:25:50 PM
CJBennett CJBennett is offline
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Default Re: Thoughts on crankshaft welding/ engine block welding

I have a new shortblock for that motor with a 5/8 crank. Give you a deal on it. PM me and let me know. Its left over from a small engine class I use to teach at Ford. Those days are gone though. Ford got rid of the whole program last spring when the were making cut backs. Would be nice to see it go to a good use.
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Old 04-14-2008, 05:04:32 PM
bitsnpieces1 bitsnpieces1 is offline
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Default Re: thoughts on crankshaft welding/ engine block welding

[QUOTE=bill chasser;295872]Mac Leod

Regarding the crank. A good crank grinder can machine the pto shaft down and then bore and press a new peice of stock onto the remainder, weld the end of the new stock onto the existing crank and remachine the stub to any spec you need.

OR

Instead of welding, you could machine the shafts to the sizes needed to allow threading, say 1/2x?, (external on crank, internal on stub), with left-hand or right-hand threads so that the joint tightens when engine put under load. Need to be sure that mating surfaces are square and mate well to prevent mushrooming. I've seen this done on large electrically driven pumps where the water seal packing has worn away the shaft so much that the shaft has to be repaired. Real expensive buying a brand new 100+hp armature.

Les
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Old 04-14-2008, 08:58:43 PM
bill chasser bill chasser is offline
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Default Re: Thoughts on crankshaft welding/ engine block welding

Quote:
Originally Posted by Mac Leod View Post
Heres a picture...how strong would the sleeve be if it is welded on (seems like where it is welded would be a good spot for the shaft to sheer)

I think welding it up and grinding down is the best option but I would like as much input as possible for both the crank and block

Thanks

Mac Leod
The weld is used to to fill in at where the new stock will terminate on your existing pto once it is pressed on. the weld is exactly what will prevent the sheer from taking place. Although I don't under cut my cranks all the way back into the main bearing area you could just as easily do that and have the roller bearing with a zero tolerance fit cover the point of repair if you were worried about this. If your not trying to extend the shaft but only trying to bring it up to spec then you could have the existing pto welded up and turned down. I might have misunderstood what you were trying to do.

This kind of repair has been done to fix a crankshaft snout on a Top Alcohol Donovan Hemi that rpms @ 10k and there has been no failure yet. I doubt that your eng will ever have that kind of stress. I'm fixing my cranks this way to save them as they just no longer exist in quantities any longer. My pto side of the crank must carry a centrifugal clutch and variable speed belt pulley that weighs in at about 7 lbs and has a constant pull on the belt from opposing forces of the drive and driven pulleys. The crank is not supported on the pto side end.

I see CJBennett has offered up an engine for you so the issue is now rendered moot. But it is a means of repairing broken crank snouts.

Hope it works out... Bill

CJ

I wrote back to you regarding the lauson head on your pm but didn't get a second reply
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Old 04-14-2008, 10:46:02 PM
CJBennett CJBennett is offline
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Default Re: Thoughts on crankshaft welding/ engine block welding

Bill I have a head for you. PM me your address.
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