Crankshaft main bearing

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Crankshaft main bearing

Post  Watts&Son on Thu 29 Dec 2016, 5:02 pm

Hi all, hope you have had a good Christmas, I am doing a bit of winter maintenance on our engine, I want to remove the gear side main bearing as there is a slight up and down movement (I made a mistake when putting it together, instead of lapping it I shimmed it) so now I have to take out the shim. I have removed the gears but I have not been unable to remove the 3rd gear housing. I am sure someone has taken theirs off, so any help would be appreciated. Maybe a puller? I know on the full size they cut away part of the housing, but I don't know if it would be a good thing on a miniature. Many thanks for your help. David.

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Re: Crankshaft main bearing

Post  lynnr on Thu 29 Dec 2016, 6:00 pm

Hi

Yes I have removed my crank before it was modified as per the full size with the notch in the 3rd gear boss.

I actually removed the bearing housing with the crank still in it. Then I had it in the workmate and with heat and wooden drift I moved 3rd boss far enough to extract the bearing housing then drifted the boss off fully.





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Re: Crankshaft main bearing

Post  Mark the spark on Thu 29 Dec 2016, 7:01 pm

all the newer kits from STW have this cut away from the factory
mark

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Re: Crankshaft main bearing

Post  Robfishman on Fri 30 Dec 2016, 1:38 pm

I remember it was a right sod to get off and mine hasn't been run yet, like lynn I had to take the lot out and carefully work it off with a block.   I didn't have any pullers but think they may have made the job easier if you know anyone with some.

With the modification done I'm now finding the gear sticks slightly, and appears to lock on the gear slide, time will tell if it behaves itself.
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Re: Crankshaft main bearing

Post  Steve Traill on Fri 30 Dec 2016, 7:29 pm

Getting the third gear off the crank was very difficult, I had locktited mine on for good measure. I needed to take three of the shims on the top of the bearing and put them on the bottom as I was getting a whining noise in middle gear with the mesh being too close. In the end I drilled & tapped two M10 holes in the back of the gear & with some threaded bar & a bearing puller it came off really easily. It's difficult getting a straight pull any other way. By the way moving the shims cured the whining noise completely.
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Main bearing

Post  Watts&Son on Fri 30 Dec 2016, 7:49 pm

Thank you to everyone that replied, to my question. If possible I did not want to remove the crankshaft., because earlier this year the flywheel came loose, so I locktighted the key in which obviously makes it difficult to remove. So I was hoping to take the tops off the bearings and just lift the crankshaft. I will first try a puller (I will have a go at the weekend and keep you posted). Steve, my gears are a bit noisy probably through things settling down. Sounds like mine are meshing too deeply, how much clearance should there be? Thank you all once again for replying David.

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Re: Crankshaft main bearing

Post  Steve Traill on Sat 31 Dec 2016, 12:08 am

The mesh distance is pretty close, I don't know the distance only that if it makes a horrible noise when you are in that gear then it's probably too close. For me it was middle wheel, for others I heard of it was high wheel. I think that the preset distance of the parts supplied is spot on but that there will be some variation in the horn plates to boiler orinentation.
The shims I used were pretty thin (couple of thou) so it's not much. I had also added grub screws to the flywheel and used a dial gauge to set it up pretty true. The problem with the flywheel is that it could do with being a fraction tighter on the crank. It sits ok until you fit the key and that chucks it out of true. Putting three M5 threaded holes at each end of the flywheel boss helps set it up how you want (the inner holes are drilled at an angle from the outside as there isn't any meat on the inside). I then filled the holes up with thick grease. I don't use locktite for retaining the grubscrews, instead I use two grub screws to each hole with the second one locking the first. I found the bearing needed shimming to stop it being loose on an up & down plane, if I was doing it again I would put the shims on the bottom as that helps with the gear clearance.
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Main bearing

Post  Watts&Son on Thu 09 Feb 2017, 7:50 pm

At last I have sorted the main bearing. I cut away the 3rd gear housing in situ with an angle grinder with a very fine disc. I was then able to remove the crankshaft and sort out the bearing. Thank you for your help. I would like to sort the pump, it seems to pump too much water, a friend suggested reducing the intake so it can't pickup so much water, but I think reducing the offset of the eccentric which would be better. I just wondered if anyone has come across this on their engine and found a solution. Many thanks David.

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Re: Crankshaft main bearing

Post  lynnr on Fri 10 Feb 2017, 12:11 am

Feather the valve will reduce the mechanical pumping. I have mine so it will happily generate with the valve about 2/3 and the boiler level stays level. On full I can cruise along at 6 to 7mph and the level will stay as is without using the injector.

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Main bearing

Post  Watts&Son on Fri 10 Feb 2017, 9:50 pm

Thanks Lynn, I have had the valve 3/4 shut and it is fine but if my son is driving he may inadvertently shut the bypass which is a bit of a worry. maybe
I could put a stop so as it could not be fully closed. Many thanks, it is freezing here must be a lot colder where you are? Keep warm, regards David.

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Bearings

Post  Watts&Son on Sat 04 Mar 2017, 6:41 pm

Hi, everyone, I have steamed the engine today, the gears run a lot quieter I shimmed the bearings up a couple of thou so thanks Steve. At the moment there seems one thing after another, I still have a knocking. When the regulator is opened it knocks and also when I shut it. The big ends seem to be tight with no play I did use lapping compound on the live steam big end as well as the gear side main bearing. I have no means of measuring the internal size of the bearing but I have mic'ed the crank and this seems ok. The knock is definitely on the crank end, but it seems impossible to pinpoint it. Thanks David.

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Re: Crankshaft main bearing

Post  sonick45 on Sat 04 Mar 2017, 8:02 pm

Check the pump eccentric isn't catching on one of the other eccentrics.
I found this was causing a knock and took me ages to find it. Was only catching very slightly but the sound was carried and amplified over the other side of the crank.
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Re: Crankshaft main bearing

Post  Mark the spark on Sat 04 Mar 2017, 8:34 pm

If you go to ebay and get some "plastigauge"
It looks like a plastic thread you put a bit on your crank and bolt it up then unbolt and you use the gauge supplied and it tells you your gap in the bearing
mak

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crankshaft main bearing

Post  Watts&Son on Sun 12 Mar 2017, 10:04 pm

Hi all, thanks for the replies, I thought the knocking was coming from the pump, but it is not so, I have lifted the crank once again and re-assembled the bearings. using engineers blue they seem ok. I have not done this on the gear side main bearing. The big ends seem ok, but under steam when you open the regulator there is a knock or more of a thump, also when you close it when the engine is slowing down it is the same knock sounds. It seems the sound is coming from the crankshaft end but sound travels. It is at a point when the live steam big end is between bottom and top dead centre on the back stroke. The noise is quite loud so I would have thought it would be easy to find but not so, the main bearing on the gear side lifts slightly as though something is catching. I have tightened the bearing down tightly but the noise is still there. I am not sure where to go next, I can turn the engine over by hand and it is smooth but now quite a lot of resistance because the bearings are tight. Thanks, David.

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