Author Topic: Tight Crankshaft Bushes  (Read 3892 times)

Samo

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Tight Crankshaft Bushes
« on: November 21, 2017, 11:41:08 AM »
Hey folks

So I've finally started the rebuild of my Lister 12/2 and hit an early snag getting the crankshaft bushes into the housing. One was a snug press fit with reasonable interference, the other is very tight.  I honed the housing, and applied heat, and it goes in a little, but I'm now wondering what the normal approach is for seating the crankshaft bush into the housing? Concerned if I hone it too much and it's not true I'll create other problems.

Advice appreciated.

thanks
Samo

Lister CS 12/2 & JKSON 10/1 Listeroid

dieselspanner

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Re: Tight Crankshaft Bushes
« Reply #1 on: November 21, 2017, 12:47:20 PM »
Hi Samo

Before changing to Taper Roller Bearings I fitted new bushes from India into genuine Lister carriers and they were bloody tight. I ended up with them between the door posts of my stone built barn and pushed them in with a 10 ton hydraulic jack working sideways.

I wasn't worried about the id shrinking a little, the crank shaft was well worn  and after I'd polished off the rust on the rest of the shaft they slid on lovely.

Sadly they were still too sloppy for my liking so I changed to TRB's fitted with liberal amounts of Loctite (610, I think) That seems to have done the trick, however the CS has yet to go into long time service

Cheers Stef
Tighten 'til it strips, weld nut to chassis, peen stud, adjust with angle grinder.

38ac

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Re: Tight Crankshaft Bushes
« Reply #2 on: November 21, 2017, 01:41:46 PM »
I have just recently run into that same issue with Indian main bushings also. They used to be very consistent and correct, but no more.  The bushing should be a light press fit in the housings, if you get too aggressive pushing an oversized bushing them in your going to have an I.D. problem to fix when your done or possibly a ruined bushing.  You have two choices, increase the bore size or reduce the bushing size. I reduced the bushing size so the next guy (with a correct size bushing at his disposal) wont have a problem to deal with.  I did this in the lathe, you could do it in a drill press with a wood mandrel, or you can order a couple more and hope you get one with the correct O.D.  In my last batch I had one of four that was wrong.
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Samo

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Re: Tight Crankshaft Bushes
« Reply #3 on: November 21, 2017, 07:23:48 PM »
In my case Stef the bushes are a nice fit on the crankshaft and I intend to keep it as original as possible. I have a big bottle jack and could press them in, but shrinking the ID would give me other problems...
 
Thanks for the advice, I'll reduce the bearing OD that makes sense.

Samo
Lister CS 12/2 & JKSON 10/1 Listeroid

Samo

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Re: Tight Crankshaft Bushes
« Reply #4 on: November 22, 2017, 10:51:26 AM »
Hey Butch,

  Your advice was spot on, I made up a cloth covered mandrel jig for my drill and used a mill file to reduce the bearing OD while it was spinning. Worked like a charm. Checked it regularly and eventually got a nice tight fit, that I had to press in about halfway in. Cleaned up, lubed up, installed the crank and Bob's your Auntie... spins nice and smooth..  Perfect!  Crank and Cam and lifters all installed tonight. Tomorrow night I'll time the Cam/Crank and install the idler gear.

So slow in the tear down & repair lead up and so fast to come together!

cheers,
Samo
Lister CS 12/2 & JKSON 10/1 Listeroid

carlb23

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Re: Tight Crankshaft Bushes
« Reply #5 on: November 22, 2017, 01:01:10 PM »
you could have tried freezing the bushing to shrink it a bit.

mike90045

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Re: Tight Crankshaft Bushes
« Reply #6 on: November 22, 2017, 06:24:46 PM »
you could have tried freezing the bushing to shrink it a bit.

But if it didn't expand enough (from being oversize) then the ID would be too tight ?

Samo

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Re: Tight Crankshaft Bushes
« Reply #7 on: November 22, 2017, 07:37:24 PM »
I did try freezing the bush and heating the carrier and it would have gone in with the press, however as Mike said I was concerned about bearing shrink. I learned that lesson with the little end bearings on the conrod, I pressed them in and then I couldn't get the pin in and they had to be honed.
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dieselspanner

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Re: Tight Crankshaft Bushes
« Reply #8 on: November 22, 2017, 08:06:59 PM »
Been there and done that to small end bearings.............

Cheers Stef
Tighten 'til it strips, weld nut to chassis, peen stud, adjust with angle grinder.

Samo

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Re: Tight Crankshaft Bushes
« Reply #9 on: November 23, 2017, 11:06:18 AM »
And on to tonight's challenge. The radius of the center main bearing doesn't fit the center main carrier, though comparing the radius of the old bearing it appears they are the same. I've checked the forum but there's no discussion I can find on this. So what's the normal procedure for installing  the center main bearing on a twin?

thanks
Samo
Lister CS 12/2 & JKSON 10/1 Listeroid

dieselgman

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Re: Tight Crankshaft Bushes
« Reply #10 on: November 23, 2017, 04:06:43 PM »
I did try freezing the bush and heating the carrier and it would have gone in with the press, however as Mike said I was concerned about bearing shrink. I learned that lesson with the little end bearings on the conrod, I pressed them in and then I couldn't get the pin in and they had to be honed.

That procedure is correct for the connecting rod bushings... press and hone to size. Main bearings are another thing though.

dieselgman
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Samo

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Re: Tight Crankshaft Bushes
« Reply #11 on: November 24, 2017, 03:46:41 AM »
The center main bearing fitted ok in the end... I cleaned everything, lubed it then put the lower shell into the carrier, and the lot into the vice. I slowly pullid it up and the bearing flexed the 1mm or so required to seat into the carrier. That 1mm at the sides translated into a 5mm gap between the bottom of the bearing and the carrier.  I've never had to seat a crankshaft bearing like that so it was a little unnerving first time around.... I was waiting for the metallic snap sound, but it didn't happen. Screwed the retaining thread into the center and the bearing is flush and tight. Tonight I'll see if it fits the crank.... 
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Samo

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Re: Tight Crankshaft Bushes
« Reply #12 on: November 25, 2017, 08:20:42 PM »
An update on the Twin,

Are they all like this? Of course the crank didn't fit properly.... with only the top center main bearing (CMB) shell fitted it won't budge. I pulled the crank, removed the new bearing, popped the old one in and re-assembled. Spins freely. Ok so what's the difference?

So on closer inspection both ends of new top CMB sit proud of the carrier even though its properly seated, and also the profile is quite different. The taper of the old and new bearing is completely different. If you haven't seen the CMB for a Twin, it tapers as it gets close to where the 2 shells join.

So this difference in taper and with being a bit longer, when the CMB is seated into the carrier the radius of the shell is  too narrow.
I don't have another bearing, and seeing I've got all Saturday to work on this I'm going to modify the bearing to fit. Worst case I buy a new set.

I put the top shell into the lower carrier and filed it flat. Took it out and rubbed it on 600 grade sandpaper sitting on a flat surface. Checked it in the top carrier and it's flush. Installed the crank but as soon as I fit the crank ends fully it won't turn. I put the crank handle on a turned it twice. Pulled it all down again and checked the bearing. Shiny spots where the taper is wrong.

I don't have the equipment or desire to work on the bearing surface, but I can change the amount of "squish" by reducing material from the back of the bearing. With the bearing in wood blocks in the vice, I filed the outside of the bearing, then sanded both shells smooth again using the sand paper on a flat surface. This takes a lot of time.... Checked the thickness with my calipers and sanded it again a couple of times until it was flat. Installed the bearing, crank and... hey it's not good but definitely better.

Rinse and repeat...... 3 hours later I've finally got a smooth spinning crank, with only the Top CMB shell installed. Looking on the bright side, I'm now a master at getting the crank in and out. Plus it's a massive arm workout, I'll be looking like Arnie in a few days.

Installed the bottom CMB carrier and pulled it tight. Crank won't spin. So I backed off the nuts a turn and it's nice and free again.
I cut some shims out of thin (0.3mm) aluminium sheet and tried again. With 1 it's better, with two it spins smoothly.


So I've spent all day to get to this point and the question is - is there some clearance tests I can make to see if it's OK or do I look for new bearings?

Comments appreciated.

Samo
















« Last Edit: November 25, 2017, 08:39:18 PM by Samo »
Lister CS 12/2 & JKSON 10/1 Listeroid

Samo

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Re: Tight Crankshaft Bushes
« Reply #13 on: November 26, 2017, 10:32:22 AM »
« Last Edit: November 27, 2017, 04:41:43 AM by Samo »
Lister CS 12/2 & JKSON 10/1 Listeroid