Crankcase compatibility
- Thread starter ILLF8ED
- Start date
- Status
- Joined
- Jun 30, 2012
- Messages
- 14,087
As far as main bearing alignment is concerned it depends on how much the bearings are able to self-align. If you are using plain roller bearings getting the bores in line is critical. If the cases are bolted together and the camshaft still turns easily, then you probably won't need to fit new bushes and ream them in line. The top gasket face of the cases might need resurfacing to get them level.
gidday Alan For information purposes mate..acotrel said:
the bearing makers, The good ones FAG, SKF, publish much data about their bearings. speeds, lube, housing and journal tolerances etc. this includes angular misalignment for most types. as far as the self aligning bearings goes, I have been told by those who know much more about this than me, the spherical roller is not really the best choice and is inappropriate for our use.
getting the bores in line is critical, is not really an engineering expression. what matters is the amount of deviation.
I will look up the reference, do the math, and report back how far in thou the allowable offset is. still it wont be much.
Wont be on this thread though. I will make another thread. This one has run its natural course for me mate.
this will probably take me a couple of days, so if anyone wants to do this quicker than me please do and report back. Remember Alan, the main bearings are CYLINDRICAL ROLLERS. Parallel, not spherical. not much capacity at all for angular misalignment
thanks Alan for prompting me to actually calculate this. Aussie bradley
- Joined
- Oct 19, 2005
- Messages
- 18,978
There are Spherical contoured race within a race bearing that can take up some moving swinging misalignments from shaft & ends bending, as our cranks do at hi rpm but not out of line bearing bores. The bearing clearances tight to loose are to take up expected thermal expansion not out of line faults.
lcrken
VIP MEMBER
- Joined
- Mar 15, 2009
- Messages
- 5,038
hobot said:
??? As far as I know, the 750 and 850 cranks are the same width, except for the MK3, which is significantly wider (longer), and won't fit in anything but MK3 cases. Is that what you meant, or do you have some info on regular 850 cranks being wider than 750 cranks?
Ken
- Joined
- Oct 19, 2005
- Messages
- 18,978
Ok Ken that clarifies MK3 cranks as another case of its mis fit to avoid. Maney used to sell just DS case but not no more so maybe mis fits too common. What would you do?
A Zen student asks his Master if its true nothing last forever so don't become attached to the impermanent. Master says. Yes. Student, Good, someone dropped that old cup you inherited...
A Zen student asks his Master if its true nothing last forever so don't become attached to the impermanent. Master says. Yes. Student, Good, someone dropped that old cup you inherited...
lcrken
VIP MEMBER
- Joined
- Mar 15, 2009
- Messages
- 5,038
hobot said:
Steve Maney originally just made drive side case halves, because that was usually the side that broke. He didn't sell the half by itself. You had to send him your timing side case, and he would machine the drive side to fit, so no problems with mismatch. I don't think there were any problems with them, but when he progressed to making complete cases, there wasn't much reason for him to offer the drive side only conversion.
Other than the MK3, you can put 750 cranks in 850 cases, and vice versa. In fitting 850 cranks to early 750 cases, you would have to bore out the case mouth if you wanted to use the 850 cylinders. Because the MK3 crankshaft is significantly wider between the cheek faces, you can't fit it to other cases, but you can fit non-MK3 cranks to MK3 cases by using spacers behind the main bearings. The spacers are usually .050" - .055" thick per side.
Ken
I didn't work for Norton but I did serve an apprenticeship as a machinist in the '70s and I would be more than a bit shocked if those cases were either line bored or machined on a CNC machining centre.
They would almost certainly have been machined on accurate jigs/fixtures that had been made on a jig borer in a tool room. That was the standard practice for manufacture of this type of component during the relevant period of time but unfortunately it was the same practice as had been used for decades before and it needed investment in new machine tools.
Line boring isn't the correct application for boring crankcases and CNC machining centres just weren't in common use back then.
A good read is the series of 5 books by Richard Skelton which are mainly about the '70s but they cover the steady decline leading to the final closure of British motorcycle manufacturing. The title of the books is motorcycling in the 1970s and they're dirt cheap on Kindle.
They would almost certainly have been machined on accurate jigs/fixtures that had been made on a jig borer in a tool room. That was the standard practice for manufacture of this type of component during the relevant period of time but unfortunately it was the same practice as had been used for decades before and it needed investment in new machine tools.
Line boring isn't the correct application for boring crankcases and CNC machining centres just weren't in common use back then.
A good read is the series of 5 books by Richard Skelton which are mainly about the '70s but they cover the steady decline leading to the final closure of British motorcycle manufacturing. The title of the books is motorcycling in the 1970s and they're dirt cheap on Kindle.
- Joined
- Oct 19, 2005
- Messages
- 18,978
Ok with Andy's review of the era's machining and Ken's report of Maney machining its seems all Norton cases [but MK3 cranks] should fit as good as any from factyory or be made to match with normal shop equipment. Implies it could-should be cost effective to replace one side but for some reason its still very rare or advised against.
- Joined
- Dec 10, 2008
- Messages
- 7,253
I wouldn't be worried about fitting unmatched cases that were made in the same time frame. They were only matched as close as the jig that they were bored in.
I would worry about trying to match cases that were built years apart. Adjustment can change over years and who even knows if they were bored on the same jig. A few thousandths can make a big difference in bearing life. Jim
I would worry about trying to match cases that were built years apart. Adjustment can change over years and who even knows if they were bored on the same jig. A few thousandths can make a big difference in bearing life. Jim
Even coming from the same time frame wouldn't really guarantee too much because the numbers produced each year suggest that they were knocking out more engines than one machine could machine the casings for every year and the jigs will have gone back to the tool room for refurbishment a couple of times a year so one made in a recently refurbished jig might be out a couple of thou compared to one that was just short of being withdrawn from use.
The overall tolerances should have been capable of allowing for these discrepancies but we need to remember that the pubs next door to factories in the UK at that time were usually full at lunchtimes and 3 or 4 beers might be enough to make the operator lose interest in what they were doing when they went back after lunch. If the casing didn't fit properly on the jig first time then given the choice between hitting it with a big old hide hammer or taking it off to check what the problem was which way would they go?
The overall tolerances should have been capable of allowing for these discrepancies but we need to remember that the pubs next door to factories in the UK at that time were usually full at lunchtimes and 3 or 4 beers might be enough to make the operator lose interest in what they were doing when they went back after lunch. If the casing didn't fit properly on the jig first time then given the choice between hitting it with a big old hide hammer or taking it off to check what the problem was which way would they go?
- Joined
- Oct 19, 2005
- Messages
- 18,978
I would of thought jigs would of compensated for workers returning from happy hour. Generally on routine tasks a bit of a buzz just helps become one with the machine. So anyone know of someone that knew someone that replaced just one side, if not what a nice efficient mythical idea to rid of permanently.
gidday Steve.hobot said:
i thought we had covered all this. I have given an example of where I have done this twice. it is not a mythical idea. read this entire thread again, slowly. and inwardly digest. other posters also support the proposition.
read also the post about maney only supplying one side. What more does it take. or do you suggest we all are telling porkies?..
And the notion that a buzz helps become one with the machine.
As for the proposition that consumption of mind altering substances in a machine shop will improve performance, !!!##@%%&** BULLSHIT. In operating machine tools this is a very dangerous proposition and DEAD WRONG. I know it has happened and still does, that does not make it right.
if you trying to wind me up, well it worked. Some things should not even be joked about. this is one of them.
Steve, have you ever worked in a machine Shop.
these days, one of the first things that happen after a workplace accident, is testing for substance abuse. if you got rubbish in your system, no compensation. You may also find yourself facing charges.
I know you may be in jest, but is does not send a good message to the younger machinists here. Aussie bradley
A
Anonymous
Guest
Ta.
- Joined
- Oct 19, 2005
- Messages
- 18,978
Cool thy jets, I didn't say intoxication is safe for workers or equipment only that I thought jigs and auto control mill machines main purpose was removing human error and easing flow no matter state of health-mind. Machine maintenance is another issue. Had dangerous jobs big stuff, tight stuff upside down stuff deep in under hi on top stuff lightening level voltage, spinning stuff flapping belts molten metal pours in rain big city water plant and construction crew putting valve in under canals. So never wear metal anything, hair short [mental hospital rule] and clothes controlled. So my chronic dis=liking being a mechanic. Nothing was as dangerous as just motorcycles except ultralite powered kites. So do we know yet if its reasonable or unreasonable to shop for one side or not?
I think you are spot on Brad an my years in the British engineering have shown me how things are at the dirty end an the bull that management tell the customer about what goes off. If they know what they are talking about which they usualy don't. All the time honoured practices are still alive and well to this day.
Also you must factor in that some machinists are less bothered than other about what they make or just less capable. On old worn out machines this is often the biggest problem with getting it to make a part correct to the spec.
Also you must factor in that some machinists are less bothered than other about what they make or just less capable. On old worn out machines this is often the biggest problem with getting it to make a part correct to the spec.
I suppose the most important question is one that I certainly can't answer and that is how old was the machinery the work was carried out on? Given that one of the biggest complaints about British motorcycle manufacture was lack of investment I'd say it was probably steam age 
- Joined
- Oct 19, 2005
- Messages
- 18,978
I'd suspect that factory mangeagment getting comfortably numb may of been more injurous to Norton than some of the work forces breaking rules. Still un-known unanswered - is it reasonable or not to try 1/2 case replacement.
case-the-welded-case-t21273.html
case-the-welded-case-t21273.html
As LAB has mentioned, Norton used to suggest (back at least as far as the 1930s) that if one half was to be replaced, the other should be returned to the factory and with the single-cylinder models, this was extended to include the timing cover (cams on these models run on bushes in crankcase and cover).
However, I have fitted an NOS timing cover to my 16H without any alignment problems which suggests that repeatability was fairly good, even then.
I think on a Commando that I would replace cam bushes and if crank and cam spin easily, and top face are in order then for street use, I'd be quite happy to use the resulting unit. I suspect that what Norton were worried about is that parts would be used together without being checked. Provided basic checks are carried out then it should be quite possible and frequently has been done in the past....although it's more often the numbered drive side case which is damaged.
However, I have fitted an NOS timing cover to my 16H without any alignment problems which suggests that repeatability was fairly good, even then.
I think on a Commando that I would replace cam bushes and if crank and cam spin easily, and top face are in order then for street use, I'd be quite happy to use the resulting unit. I suspect that what Norton were worried about is that parts would be used together without being checked. Provided basic checks are carried out then it should be quite possible and frequently has been done in the past....although it's more often the numbered drive side case which is damaged.
- Joined
- Sep 18, 2012
- Messages
- 46
I just finished rebuilding my engine with a 72 primary side case and an 850 TS case. As mentioned in previous post the oil pickup hole has to be drilled in the primary side case as the two do not match up. I plugged all the extra holes in the TS and used the CNW valve on the primary side. Will see have things work out with this setup. The bike was bought from a previous owner with the two cases mated but the new oil hole was not drilled. Just have to put the engine back in the frame now.
- Status
Similar threads
