check your cranks everyone..valve gear assembly

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check your cranks everyone..valve gear assembly

Post  northburrell on Fri 13 Feb 2009, 8:43 pm

Hi

copy from the cleading post..

I found some lumps on the shaft were the big end fits.. these have come from were the bar or shaft that is pressed into the two bell parts of the crank and has been squashed together too much, this has forced the metal out meaning the big end bush wont fit in the gap between the two bells and even if it did it would be turning on these lumps created... I havent spoken to STW yet as it saterday but i'm a little annoyed it's turned out like this... it just made me wonder if these parts are checked together with the bearings... so check your cranks.. if your big end bush wont fit on the crank...check it out...you might have to file some off your bronze's and the lumps off the crank pin..


UPDATE:

Spoke with Steve and he says they are pressed together on the crank pin but not with that much pressure.. but I think even a little too much pressure will be enough to bulge the metal of the crank pin... He said it's fine to be filing down the bronze bushes to fit inbetween the bell cranks onto the crank pin... He did say to make sure the surface finish on the pin was good... i used engineers blue for this and all is now fine..

Thanks Steve..


Last edited by northburrell on Tue 17 Feb 2009, 8:37 pm; edited 5 times in total

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Re: check your cranks everyone..valve gear assembly

Post  northburrell on Sun 15 Feb 2009, 12:27 pm

an update on my crank.. looking at the lumps above I decided to use a needle file to take them off as i have no lathe or mill.. I filed the big end bronze's down width wise so it would fit in beteen the two bells of the crank and fit the shaft, this took a very long time to do and get right. i used the strap and the wedge to hold the two bushes together to keep then nice and flat and in line, placed it on a wide medium file and filed away...for about 3 hours!! I wish i had a milling maching!! i took my time and got it spot on...I use 14 inch wide small file and started on the crank pin again i took my time and went round the lumps on the crank i used engineers blue and fitted the bush, strap and wedge then turn it round, it was a little tight at first so i took of the bush and looked at the engineers blue this showed me that no part of the bush was touching the crank pine apart from the edges were the lumps on the pin are, this ment the lumps were still there so more filing was needed.. it took me about 4 hours to get it spot on and now turns free and smooth with no high spots..nice..

the bushes for the lifting link dont need pressing in with a vice i just popped in the bush turned it upside down on then bench then pushed,,pop pop pop and that was it job done..

my eccentric straps have quite bad cutter marks were the eccentric flange runs.. when tightening up the strap the eccentric stuck solid. these cutter marks need removing.. i cut some small strips of wet and dry that fitted round the eccentric and in the groove of the strap, i did up the strap finger tight and started to turn.. it did this to each one three times each with new paper.. one was still a bit tight so i use some tin foil as a shime.. this is about 1 tho thick and was just enough to space out the strap to get a good free turning eccentric.That's my crank and valve gear pretty much done.


I'll upload a photo later..

Jo

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Rocky spot

Post  Big Al on Sun 05 Apr 2009, 7:49 am

Just fitted the crankshaft and connected it to the piston. goes round fine until it reaches a few degrees before the changeover spot on the back stroke when it goes tight and seems to want to get to the BDC then seems to be reluctant to go passed BDC and back up and over. There is an easy bit of about 10 degrees either side of BDC before it hits the tightish spot again the its free again.

I thought at first the stroke was too long on the back stroke and the piston was reluctant to travel back any further in the cylinder but after removing the rear cylinder cover, cross head guide brackets I see there is still plenty of room

When I connected the piston rod to the con rod, without the crossheads guides or the rear cylinder cover plate it was all free wuth no problem. The problem re-occurred when I bolted the cylinder rear cover on tight. It would appear that the centre of the rear cover is out of line with the centre of the piston and thus the piston rod binds to the cover the nearer the piston gets to the rear cover. Using the flywheel to turn the crankshaft round over causes this tight spot to show up and on the apex of the backstroke. I cannot see how to overcome this as there is no way to adjust the rear cylinder cover and running it with it as it is will cause wear.

I will contact Dean on Monday but in the meantime has anyone else encountered this or got any ideas?

Alan


Last edited by Big Al on Sun 05 Apr 2009, 9:23 am; edited 1 time in total (Reason for editing : found the proper reason)

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Re: check your cranks everyone..valve gear assembly

Post  BUNGLE on Sun 05 Apr 2009, 12:33 pm

HI AL,
YOU DIDN'T SAY IF YOU REFITTED THE SLIDE BARS WHEN YOU REFITTED THE REAR COVER. WE FOUND THAT THE LOWER SLIDE WAS 'HIGH' IN THE WEIGHT SHAFT BRACKET YOU OURS, THUS 'PINCHING' THE CROSSHEAD BETWEEN THE UPPER AND LOWER SLIDES, AT THE POINT WERE YOURS IS GOING TIGHT, WE MILLED A RECESS IN THE LOWER SLIDE WERE IT FITS TO THE BRACKET - A LITTLE DEEPER THAN WE FELT IT NEEDED, SO WE COULD SHIM IT 'BACK' A TAD, IF NEEDED. YOU COULD OF COURSE CAREFULLY FILE THE RECESS.

(A TAD IS SLIGHTLY BIGGER THAN A GNATS D*CK !!!!!!!!) Laughing

HOPE THAT MAY HELP.

REGARDS
BUNGLE

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Re Tight Crank

Post  Big Al on Sun 05 Apr 2009, 1:05 pm

Bungle

It became tight as soon as I fitted the cylinder back plate, didn't get as far as the slide bars

Alan

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Re: check your cranks everyone..valve gear assembly

Post  northburrell on Sun 05 Apr 2009, 1:11 pm

Hi Big al

I have a similar problem. The rear cover gland hole needs to be a lttle bit bigger than the piston rod size. you could enlarge the hole a vey small amount and let the gland packing do the work of sealing as thats what i's there for really. I found way back when i fitted the piston that when screwing the piston on it went round the threads wonkie and not square to the rod. when done up as it should be square to the rod i found that it wouldn't get more than half way down the cylinder before jamming solid, this was with the rear cover gland packing and gland fitted. I took it all apart to have a look. My thread was a little dirty and badly cut (blunt tools) The piston was not sqare to the rod and on when spining the rod round (lathe woul be good) I could see it wobbling, i cleaned the threads through with a tap and die. It went on allot better until it met the face it buts upto on the rod. this was also cut at a funny angle left by the die used to cut the tread on the rod. the face was not finished of nice and square. I very carefully filed it round square minding the thread and taping it up to stop damage and slips. put it all back and re-tryed it in the bore. all was fine and it was able to move all the way through. I did find that it got a bit tight at BDC with the rear cover added so I enlarged the hole a little in the rear cover and hay presto it's fixed. I cant remember off the top of my head what drill i used but it really was just a slither of metal removed. once you have the glad packing in, tighten it up with the fly wheel and everything on and try to move it, when it's pretty much locked release the glad by a small amount. this will be how you set the glads for running. it maybe very stiff to turn over but once some nice wet steam with some steam oil mixed in gets in there it will free up pretty quickly.

also try rotating your piston in the bore a bit at a time and push it in and out on each turn with the rear cover and glad on, if you find that at some spots it's feeer then that were you want to try and get the piston set to. I had to very slightly and slowly counter sank my crosshead to get it to tighten up and be square to were I marked my piston to running very free in the bore. I then locked it with the grub screw..

Hope this helps it should sort it out.. unless you have been unlucky to get a duff piston with off drilling.

Jo

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Re: check your cranks everyone..valve gear assembly

Post  BUNGLE on Sun 05 Apr 2009, 1:33 pm

HI AL,
SORRY THAT WAS NOT YOUR PROB, THINKING BACK, AS JO SAID, THE FIRST PISTON ROD THAT MW SENT US WAS BADLY THREADED AND THE CROSS HEAD WENT ON PISSED. SENT IT BACK AND GOT A BETTER ONE.

BUNGLE

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Re : Tight Piston

Post  Big Al on Tue 07 Apr 2009, 5:47 am

Update

Contacted Steve and he suggested that the piston rod hole in the back plate should be oopened up as suggested. Did this and also needed to open up the hole in the gland bush. Used a felt tip pen to mark the piston rod to find the tight spot (haven't got any engineers blue!). When I put the piston rod in the bench drill to check alignment I could see the problem straight away, The piston rod is off center to the piston by about 1 mm which was enough to make it bind at BDC.

Problem now solved, turns over lovely and smooth

Now to check the eccentrics tonight.

I have only put a bolt in either side of the front spectacle plate so I can remove it easily to put the reach rod in. I dont fancy taking the right hand bearing mount off as, like Bruce, mine was sprayed with it in place.

Alan

PS Did we get a grub screw with a kit to put in the side of the crosshead to lock it to the piston rod 'cos I ain't got one and cant remember ever having seen it?

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Re: check your cranks everyone..valve gear assembly

Post  northburrell on Wed 08 Apr 2009, 4:59 am

Yes we did get a grub screw for the crosshead I think it came with the piston kit. it's so small you might have never even seen it...

Glad it's all sorted out for you now.. mine was the same and enlarging the hole and findind the piston Free running spot made all the diffrence..

just mak sure you setup your slide bars properly as these will also make it go stiff if not right..

all the best..

J

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Re: check your cranks everyone..valve gear assembly

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