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ASSEMBLY OF MOTION

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ASSEMBLY OF MOTION Empty ASSEMBLY OF MOTION

Post  davidwatts Fri 30 Oct 2020, 4:57 pm

I just wondered if anyone has come across this problem. On the high pressure side the piston fits in the cylinder bore with a with a little resistance, which seems ok, the cross head is a good sliding fit in the trunk guide. I have fitted the gland. all seemed ok. When I screwed the piston rod into the cross head (which screwed in easy enough) the whole assembly is far too tight and I can hardly move it. The low pressure fits and slides perfectly, any ideas how to solve this problem would be much appreciated. Thanks David..

davidwatts

Number of posts : 9
Location : wiltshire
Registration date : 2019-08-04

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Post  Poderoso Sat 31 Oct 2020, 3:22 pm

Hi David
I had the same problem on trial assembly.
If you loosen your trunk guide bolts and give the trunk guide  a wriggle there should be enough movement to find a happy medium.  
Try tightening the bolts with the piston at end of stroke behind trunk guide.
I left my gland packing out until i had completely assembled the motion, it just makes it easier to detect any stiffness  or slight misalignment.
Hope this helps

Poderoso

Number of posts : 10
Location : Birch essex
Registration date : 2017-07-06

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Post  davidwatts Sat 31 Oct 2020, 5:43 pm

Many thanks for that I will give it a try. David.

davidwatts

Number of posts : 9
Location : wiltshire
Registration date : 2019-08-04

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Post  davidwatts Sat 07 Nov 2020, 6:25 pm

Today I was going to try to sort the problem with alignment of the high pressure piston rod and the crosshead as mentioned before but I seem to have another issue with the crankshaft. The crank webs and the trunk guides seem to be out of alignment. The crankshaft needs to move towards the gear side by about 1mm. I have already fitted the boiler into the chassis which fitted perfectly. The second, shaft and gears have been fitted and all seems a good fit, so I did not really want to pack the hornplate out. The bearing guide on the flywheel side is no problem to sort. If I have to pack the hornplate out I think fitting the boiler back into the chassis would be difficult with the extra packing. Any ideas thanks David. .

davidwatts

Number of posts : 9
Location : wiltshire
Registration date : 2019-08-04

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ASSEMBLY OF MOTION Empty Crank alignment

Post  Poderoso Wed 11 Nov 2020, 6:45 pm

Hi David
You should be able to move your crank over just by moving it on the main bearings and then realign your eccentrics.
If you have used retainer  then you will probably have to use some  heat and a puller to move/release the bearings and eccentrics, being careful not to damage the seals with too much heat.
On the subject of seals i also popped the seals off  all my bearings to check and add/replace grease as required, just as a precautionary measure as some of my bearings had only a minimal amount of grease in them.

Gary

Poderoso

Number of posts : 10
Location : Birch essex
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Post  davidwatts Sun 15 Nov 2020, 5:48 pm

Hi Gary thanks for the reply, having measured the position of the bearings, you are right, the gear side is about 4mm from the shoulder so it should move but it is reluctant, so I think I will block out the crank webs and get a bit more brutal with it. On the flywheel side there is no problem. Going back to the original problem, I have taken off the trunk guide and screwed the piston rod into the crosshead and it seizes solid, so I think I will have to get STW to sort it. Many thanks David.

davidwatts

Number of posts : 9
Location : wiltshire
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Post  davidwatts Thu 31 Dec 2020, 6:09 pm

Hi all, The problem with the trunk guide has been sorted by STW, it turned out to be a slightly bent piston rod. When I connect the high pressure connecting rod to the big end all turns over smoothly, but the the low pressure side is nearly 1mm off centre of the crank journal. I have re-centred the crankshaft on the low pressure side but it just transfers the the problem to the high pressure side. I could take 1/2 mm off one side of each of the bearings. I have used a sealant on the trunk guides not a gasket. If I used a gasket would I be able to take some of the mis-allignment out? Any help would be much appreciated. David.

davidwatts

Number of posts : 9
Location : wiltshire
Registration date : 2019-08-04

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Post  Poderoso Sun 03 Jan 2021, 9:14 pm

Hi David
That was another small hurdle i had to overcome!!
First  make sure your little end bushes are not protruding past the side of your connecting rods.
My problem (short version) was the machining on the cavity on one of the cross heads where the little end assembly enters was either slightly off centre or it could be it was not machined wide enough. So rather than send it back i simply rotated it 180 degrees which meant i just had to copy and drill the oil way on the opposite side which is the new top when in position to enable oil to feed to the little end.  
Or talk to Will  at STW but either way a simple fix.

Gary

Poderoso

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