I recently had to buy a set of scrapers to relieve the corner of one of the main Babbit bearings in my Riley engine. The new crank has more of a radius on the journal so needed to chamfer the corner of the bearing a little more. That was easy enough but it is interesting that the set of scrapers I bought were just like the ones shown in this film. Is this the standard set for scrapers? A lot of old manuals/articles talk about scraping but I have not actually seen a good description of the process as shown in this film. I was just wondering how good a demonstration this is?
The crank and rods I am using in the Riley engine (Arrows) are more modern design and use shells (so I will run an oil filter) so I don't actually need to scrape anything this time round but it looks like a useful skill to have. I always wonder though in modern engines with shells they always say check the clearances with plastigauge but then never say what the hell you're meant to do if it is wrong! With a new precision machined crank and modern precision shells what are you supposed to do if the clearance isn't right? Send the crank or rods back and complain?
Simon
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There's at least one career marine engineer and at least one career engine rebuilder on here (not to mention some skilled amateurs) who will probably evaluate the scraping technique!
I have a boxed set of Moore & Wright scrapers, they're quite small (150 long), there is a triangular, a flat and a curved one in the set, but the curved one is more gradual in the curve compared to the one in the film clip.
I've never used them on bearings, they're mostly been used for chamfering cylinder bores and reducing burrs on surfaces.
The instruction to check modern engine bearing clearances with plastigage [and checking 'nip' and 'crush'] is more a last minute check to make sure one's engine reconditioner of choice has supplied the correct undersize bearings, and also the o.d. of the shells matches the main bearing and conrod big end bores. Ford, for one, could oversize them which could cause problems for the unwary further down the track.
Your supposition of sending them back and complaining is exactly right, an added expletive-laden tirade would also be in order
Edit: There's one of the engine reconditioners, how do you rate the technique Colin?
The crank and rods I am using in the Riley engine (Arrows) are more modern design and use shells (so I will run an oil filter) so I don't actually need to scrape anything this time round but it looks like a useful skill to have. I always wonder though in modern engines with shells they always say check the clearances with plastigauge but then never say what the hell you're meant to do if it is wrong! With a new precision machined crank and modern precision shells what are you supposed to do if the clearance isn't right? Send the crank or rods back and complain?
Simon
[/quote]
There's at least one career marine engineer and at least one career engine rebuilder on here (not to mention some skilled amateurs) who will probably evaluate the scraping technique!
I have a boxed set of Moore & Wright scrapers, they're quite small (150 long), there is a triangular, a flat and a curved one in the set, but the curved one is more gradual in the curve compared to the one in the film clip.
I've never used them on bearings, they're mostly been used for chamfering cylinder bores and reducing burrs on surfaces.
The instruction to check modern engine bearing clearances with plastigage [and checking 'nip' and 'crush'] is more a last minute check to make sure one's engine reconditioner of choice has supplied the correct undersize bearings, and also the o.d. of the shells matches the main bearing and conrod big end bores. Ford, for one, could oversize them which could cause problems for the unwary further down the track.
Your supposition of sending them back and complaining is exactly right, an added expletive-laden tirade would also be in order
Edit: There's one of the engine reconditioners, how do you rate the technique Colin?