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Author
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Topic: Crankshaft journal polishing
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Miles
True Blue Posts: 119
From: Saskatchewan, Canada
Registered: Jun 2004
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posted October 02, 2007 18:30
   
Good Morning,One of my majors had a conrod bearing failure. The crank journal was not scored but has residual bearing material that needs to be removed. How do I remove the bearing material and polish so I can fit a new bearing? FYI - This is an already tired engine and plan a complete rebuild next year. Thanks in advance. IP: Logged |
tmac
True Blue Posts: 465
From: USA Washington state
Registered: Jul 2002
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posted October 03, 2007 04:42
Is it still in the tractor?? If so get what metal you can scraped off. Then polish with a wrap of crouces cloth ie very fine emery paper 800-1000 grit. You can also use an extra rod with a worn bearing shell and a lapping compound set. Just apply the compound to the bearing shell then close the rod cap and turn, a little back and forth going a little further each time with full rotations being completed. This can be done form under the engine with the pan off. I have fixed a few this way. You need to mic when finished to see if you can install a small under size bearing shell like .001 to .004. If these are not available shim with SS shim stock. This is a fix not a repair but will run long enough to put to rebuild. There used to be in block crank grinders too. You will have to ask around to see if anyone still does this service.
quote:
Originally posted by Miles:
Good Morning,One of my majors had a conrod bearing failure. The crank journal was not scored but has residual bearing material that needs to be removed. How do I remove the bearing material and polish so I can fit a new bearing? FYI - This is an already tired engine and plan a complete rebuild next year. Thanks in advance.
IP: Logged |
Miles
True Blue Posts: 119
From: Saskatchewan, Canada
Registered: Jun 2004
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posted October 04, 2007 05:28
tmac,Used your advice and it cleaned up nicely...I mic'd it at 2.490-2.492 so I purchased .010 under bearing from NH...But on assembly tonight it was just too tight at 55 lbs-ft on the cap bolts. I will have to buy another set of std size tomorrow and be happy with that. Where would you get the shims you are talking about? Is this an accepted "fix" practice? Regards IP: Logged |
tmac
True Blue Posts: 465
From: USA Washington state
Registered: Jul 2002
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posted October 04, 2007 09:34
.010 undersized or more by .010 sizes bearings are for regrinds only and rarely used for wear compensation. Wear compensated shells are rarely made in anything more than .004" under by .001" starting at .001" under. Shimming stock may be had at most machine shop supply store. Try MSC supply. But a local store even an auto parts store can supply with a cut of what you need. I have used both brass and steel the brass can be soldered to the back of the shell, this can be a touchy job though. I would use SS or steel then locktite to the shell. You will need to either mike this lashup before installation or use plastic gauge. Loose is is better than to tight. But within the OH limits specified. A full pass with the shim, meaning that both the upper and lower shell has shim, not to be installed under the retainer detent. You need to mike the crank journal for roundness and taper either one of these conditions will shorten life of you new install. But keeping that in mind when pulling power of the engine.
I had a Hercules diesel powered 6000 lb forklift one time that was lashed up all over the engine inside. I gave it a year, 10 years later I put in a new engine. Not bad for a totally worn out engine!  )Be sure and ask about their big book for free!
But when they say BIG BOOK they mean that so ask for it in 2 volumes!!! But not the disc without the book!
When they ask for your business name just tell them (insert a name)\Farms http://www1.mscdirect.com/
http://www1.mscdirect.com/CGI/GSDRVSM?PACACHE=000000030715955
quote:
Originally posted by Miles:
tmac,Used your advice and it cleaned up nicely...I mic'd it at 2.490-2.492 so I purchased .010 under bearing from NH...But on assembly tonight it was just too tight at 55 lbs-ft on the cap bolts. I will have to buy another set of std size tomorrow and be happy with that. Where would you get the shims you are talking about? Is this an accepted "fix" practice? Regards
[This message has been edited by tmac (edited October 04, 2007).] IP: Logged |
tmac
True Blue Posts: 465
From: USA Washington state
Registered: Jul 2002
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posted October 04, 2007 18:13
Hey you are almost .010 under I just looked in my manual. On these I would lap to the .010 under size. Use the spare rod method to lap it down. This would also round it up if any flat spots. If you are doing this lap post it here I will detail the method. Is it still in the tractor, or in the block out? Also If I remember right you do have machine tools? Like a lathe rite? If so I will post how to make a lap bushing.
quote:
Originally posted by Miles:
tmac,Used your advice and it cleaned up nicely...I mic'd it at 2.490-2.492 so I purchased .010 under bearing from NH...But on assembly tonight it was just too tight at 55 lbs-ft on the cap bolts. I will have to buy another set of std size tomorrow and be happy with that. Where would you get the shims you are talking about? Is this an accepted "fix" practice? Regards
IP: Logged |
Miles
True Blue Posts: 119
From: Saskatchewan, Canada
Registered: Jun 2004
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posted October 04, 2007 20:18
Crank is still in the tractor... and I have no machine tools....I have ordered Std bearing and will see how it fits... also my measurement could be a few thou off.. That said...I would be interested in how to make a lap bushing... Thanks for your help IP: Logged |
tmac
True Blue Posts: 465
From: USA Washington state
Registered: Jul 2002
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posted October 04, 2007 21:37
When you get the new insert, get some plastic gauge and use this to check the fit. This will accurately tell you the size of your crank pin if you place several spots around the crank pin you can tell if you have taper or flat spots.Ok without the machine tools here is how. You will need a spare old rod and a old insert that is not burned out. Place lapping compound in the shell evenly then close the rod gradually work as described prior, when it will work freely dismantle this then clean well, measure till it gets to the size you need and round, be careful not to go to far in. When finished make sure the oil hole is free from lapping compound. When finished make sure the oil hole is free from lapping compound. (repeated) The pin will be a nice matt gray color, not shiny dont worry this will not hurt. I have saved a lot of work doing this to several forklifts that only had a bad rod. Now those machines are a major headache to take the engines out. Even doing the job this way to them wasnt easy. ;(( quote:
Originally posted by Miles:
Crank is still in the tractor... and I have no machine tools....I have ordered Std bearing and will see how it fits... also my measurement could be a few thou off.. That said...I would be interested in how to make a lap bushing... Thanks for your help
IP: Logged |
ScottL
True Blue Posts: 104
From: Marengo, OH
Registered: May 2006
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posted October 05, 2007 02:04
tmac,I always enjoy your advice as I am sure the others do. How have you gained your knowledge throughout the years ?? Were you a mill wright or a tractor or truck mechanic ?? I read your posts talking about how to weld cast iron to what you are talking about now and they all amaze me on some of the stuff that you know about. Just wanted to say thanks for the great reading. Keep up the great advice, Scott P.S. If you ever pass through central Ohio shoot me a email and I will take you out for a cold beer. IP: Logged |
tmac
True Blue Posts: 465
From: USA Washington state
Registered: Jul 2002
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posted October 05, 2007 07:19
Well Thanks Scott for the encouragement and the offer of a cold beer in Ohio but I may not live long enough to get to Ohio ). When I think of them tips I may pass on a few others tricks )I have been know to some as a pretty good "jurry" rigger ) My most money saving lash up was a save on a Boeing 707. A inboard flap track hindge gave way on coming in for a landing at Istanbul. I was on the plane as an employee. This type of thing is why they put me on the planes and paid me the bucks;((. I did notice a vibration of the wing when coming down, but when we finally stopped at the terminal and went to check the plane over I was astounded to find the outboard end of the inboard flap which by plane standards are quite large, had dropped down by 2-3 feet. Yep it was broke off and just hanging there loose by one end. I went to the captain and told him. Well to say the least, him and the aircrew got ready to walk off the plane. Coarse without them we couldnt go back round trip you know. I told them to wait abit and hold off on the cancel. He said the crew had 5 hrs before they would time out. Well to say the least it was a big problem but I found 20 Turks that would stay in the shop over their shift for a carton of American cigs each. Well the Turks really didnt want to sign off on the job either. I told them that they follow my sketch drawings and I would sign off all work. Well the Turks ( Great sheetmetal guys) got it fixed as per drawings and on the plane in the 5 hrs. I pulled the cigs from the planes duty free purser handed them out to the Turks. Now I recommended to the airline that that flap be replaced on next D-check layup. That never happened 4 years later that same flapp was still in use. But the savings on that flight in 1978 was about $300,000 USD not a bad deal for about 25 cartons of Cigs Rite!! quote:
Originally posted by ScottL:
tmac,I always enjoy your advice as I am sure the others do. How have you gained your knowledge throughout the years ?? Were you a mill wright or a tractor or truck mechanic ?? I read your posts talking about how to weld cast iron to what you are talking about now and they all amaze me on some of the stuff that you know about. Just wanted to say thanks for the great reading. Keep up the great advice, Scott P.S. If you ever pass through central Ohio shoot me a email and I will take you out for a cold beer.
[This message has been edited by tmac (edited October 05, 2007).] IP: Logged |
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