Crank Bearings.. your thoughts please

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Crank Bearings.. your thoughts please

Post  highpressure on Tue 09 Aug 2011, 11:29 am

Below is a couple of shots of the bearing dry fitted to the crank. Having read Tonys " spins real easy" comment I wanted some input from anyone else who has got to the crank fitting stage and may have encountered this. I cant even get the crank near the housing!!

I dont want to file something wrong or make any comments which might make me even less popular

The rule is there to give a straight edge and the bearing is held tight with tape.








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bearing

Post  lynnr on Tue 09 Aug 2011, 11:59 am

Hi

Have you increased the round off on the brass as that is what I had to do to get each 1/3 to fit onto the crank.
I took each part. held it to the crank with a skim of oil. rotate it on the shaft and observe. At first it was not removing the oil in an even roll as the shell was not against the machined shaft but sitting proud on the fillets. it did not take much to go from your images to a closed up fit. No work needed on the main bearing surface JUST the fillet.


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Re: Crank Bearings.. your thoughts please

Post  Rickster on Wed 10 Aug 2011, 12:24 pm

I used a permanent marker pen and covered the bearing surfaces and the radius on the edges then trial fitted by turining the bearing on the crank to see where it rubbed off then set to with a half round needle file on the edge chamfers and then emery cloth until I could turn the bearing without it feeling like it wanted to bind up. I had to do this about a dozen times to continually check the fit. I also had to emery off the sides of the bearing on both sides. I got a piece of steel surface ground that I'd used for the valve faces and again just keep trial fitting until I got a smooth feeling with no binding.

This took me a a fair few hours each for three evenings.

I then had difficulty putting the bearing into the housing without the adjustment piece stopping the adjustable part from jamming on the ledge of the corresponding part in the bearing housing itself. After speaking to Steve, I put a 45% chamfer on the bearing housing step to the bearing part itself would slip past and locate correctly.

I didn't have to do much to the outside of the bearing to allow it to slide down into the housing.
The bearing fitting was very time consuming but on the isntructions it says don't worry about getting it to spin easily as it will all need lining up again later when we fit the conrods/wayshfaft/cyclinder components.

I found the left hand bearing housing needed adjusting complelety. I undid all the adjustment from when done with the crankshaft alignment tool supplied with the boiler kit. This is where I got a good "stiff but smooth" crank rotation. I can turn the crank almost a full revolution with one quick flick of the wrist (the crankshaft, the crankshaft!).

The oil hole has also been drilled in the wrong place on my engine but it's a simple job to spot the bearing with the cap in place through the oiler tube and then drill it out.

I know there has been a lot of fettling work needed but I am still thorough enjoying the build and the way I look at it is if I was building from scratch, there would be far more problems to deal with than we have encountered.

Hope this helps anyone a bit.

cheers

Rick

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Cranking around

Post  lynnr on Wed 10 Aug 2011, 12:29 pm

Hi All

Yes I am the same as Rickster. Crank is smooth but a bit stiff. Not doing anything else with it until I have more hardware attachable. Still not got my Cylinder yet Crying or Very sad

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Re: Crank Bearings.. your thoughts please

Post  craig@STW on Wed 10 Aug 2011, 11:52 pm

yes these bearings need a lot of "fitting".

don't forget, the hole in the square bearing is off set. because of this the 3 parts of the bearing will only go together ONE WAY.

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Re: Crank Bearings.. your thoughts please

Post  highpressure on Sat 27 Aug 2011, 8:52 am

Spent time over the last week attacking the bearings and got them to close up when on the crank on the bench but the back of the pressure plate was proud by at least 1mm. This causes the crank to jam completely when installed so today I got around to fitting in the housing and had several more goes at reducing the radius etc but eventually resorted to taking a file to the rear of the plate to reduce its depth. It all fits now but is still very tight to the point where it needs two hands and some force to turn the crank. Did anyone else have to do this to get the bits in the housing? And those that have a reasonably free rotating crank did they take anything of the inside of the bearing.

I am happy that I havent overdone this or screwed up the bearing as it all fits snuggly round the crank insitu and the slightest adjustment of the pressure plate hex bolt locks it all up so there is no "slack" . I just feel its still too tight and wonder wether to keep on now or wait for more bits which will make this more difficult to get too.

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Re: Crank Bearings.. your thoughts please

Post  Graeme81 on Sat 27 Aug 2011, 3:20 pm

its a bit much to have to resort to filing crank bearings....these are precision made kits!

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Re: Crank Bearings.. your thoughts please

Post  highpressure on Sun 28 Aug 2011, 1:28 am

The instruction say they need to be "adjusted" I dont know of any other way of removing metal without a file. Someone lent me a bearing scraper but it only takes off a few thou with each scrape and I want to be in steam before 2020!! Also the information from others seems to be offering tihs solution too.

The bearings are very well made as are all the components but only need to be out by a few thou to stop things moving easily. Also us builders are all different types and levels of "engineers" some know methods and how to do things properly or gently and some dont. We all have to make our way through this build in whatever way we can or take it to someone else and say "Can you do this for me or show me how this is done? " and dont have that opportunity open to us.

Perhaps someone else can shead some light on how they acheived a good fit. If you read through the above replies they say " they needed a lot of adjusting " but they dont reveal how that is made.

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Lots of fitting

Post  lynnr on Sun 28 Aug 2011, 2:35 am

Hi

My bearings needed alot of finessing. The highlights being

1. Made sure the outside machined faces had nice square edges there they mate with the casting. On the edges there is a chamfer already there but this needed extending to the edges as it sort of tapered off to a sharp edge and this would have held the shells up if the angle in the bottom of the bearing casting had any radius at all.

2. Slowely worked the thrust faces of the bearings with the bearing shells in the casting without the crank to get a nice flat fit. After each small file checking the shells on the crank to get each part to fit into the crank bearing recess without slop.

This point I started to do the check rotation phase.

3. Rounding further off the pre rounded chamfer on the bearing faces to cheeks. These chamfers required about 1 hour to get each bearing shell part to slide round the crank bearing face without "lifting" off. Also needed to check the crank had no burr on the rounded fillet used for stress relief. I checked this fit with a small amount of "dark" oil and checked that each part of the bearing shell removed the oil in a nice sausage roll effect at the edge of the shell portion and leaving as little oil as possible on the crank. N.B. The checking is done with each 1/3 of the bearing against the crank held in hand.

4. Check all 3 parts of the shell fit round the crank held in hand with a bit of tape or bungie round them. They at this point should be touching each other and produce no wabble when they are rotated round the crank. 2 strips of masking tape worked well for me here as it showed stretch marks if the segments wandered.

5. Insert the bottom segment into the housing making sure by measurment that it is completly down and solidly against the bearing cast. I had to file a small chamfer on the cast bearing to accomplish this.

6. Insert the shall segment against its adjuster and make sure the adjuster is not holding the segment away from the casting. Visually check the joint with the bottom segment and that the bearing segment is flush with the casting at the top. Check the joint also with the best roughness checker you have. "extend index finger" works well.

7. Insert the final segment and do the same. Check there is no gaps between each segment and the gaps feel smooth.

8. Now we can Insert the crank. Not yet.

9. I and others by various methods have had to file a 45deg chamfer on the bottom outer edge of the bearing shell to allow insertion past the step in the bearing casting for the adjustable segment. I myself done a small chamfer on the bearing shell.

10. With the lefthand bearing OUT. try fitting the complete assembly. With the geometry of the bottom 2 portions of the bearing you will get a good idea of fit as soon as these parts are in place around the crank. As these two parts actually hold the crank but only rotate the crank top over to the front otherwise it will pick up the small segment and try to jam.

11. Once happy apply the left bearing and as they say try try again until it is a firm free movement. Mine needs one hand to turn, it is tight but we have been told this is fine until the final alignment with the block is accomplished then at that point we redo all the above to get a "sweet" movement.

All the above took me about 10 hours. I have oiled my crank bearings and I turn the crank one eighty every other day.

Hope this helps. If anyone has anything to add or adjust please let me know and I will edit.



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Re: Crank Bearings.. your thoughts please

Post  highpressure on Sun 28 Aug 2011, 8:38 am

Thanks Lynn,

Thats about exactly as I have done, except that I put one half of the left hand shell in the base of the housing just to save constant lifting and fiddling with both sides. Throughout your report you have used the word "file" which is just as I have done. I have been to a small "do" today with a couple of other builders and betwen us we have got to the point where the crank now turns quite stiffly but everthing in the housing is done up tight. Both the other guys have built engines from STW and have also used similar methods you describe. Glad to find I havent been making a balls up of it. Might just do a tiny bit more fettling to free it up just a shade more but otherswise as you say may wait until other stuff is also needing to be "fitted"

Thanks Kev.

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