If going from stock crank to billet one...

Looking at different threads about sludge trap and billet crank, I didn't find an answer to that question:

If going from stock crank to billet one, what about the oil path? And no more sludge trap?

The reason for no sludge trap in billet cranks is, i suspect, the effort and cost of including one ...Plus let us not forget Triumph shoved something up the centre of their cranks with a thread in one web and threads are stress raisers ..funny how I have over the decades seen a few failed Triumph cranks with cracks trhat started at the thread...... If memory is correct some 'brain' in mismanagement at Triumph once asked why the company was flogging so many new cranks to the U.S.A. and was told it was because people in the U.SA. raced the lumps and the cranks had to be changed on a regular basis otherwise they failed big time.... Bet all those ('hardly used sir') cranks later found they way into people road bikes rather than into the scrap bin where they belonged.....
Every time I pulled a std crank apart I would look at the collection of crap in that sludge trap and think of how it did not go through into the big ends etc although when you find them sludged up so it is partially blocking off the holes into the big ends I did tend to wonder if some people ever changed their oil. The sludge trap was a very sensible idea and cost nothing to include at the design stage and not much at the production stage. Of course had Norton had the capability to produce one piece cranks when Mr Hopwood and co designed the Dominator motor we would of had one piece cranks.(Ever read Mr Hopwoods book 'Whatever Happened to the British Motorcyucle Industry???) Bit late now, alas, to phone Mr Hopwood in his retrement at Torquay and ask how he would of included a sludge trap and for his thoughts on the subject.......Wonder where all his design note books ended up.....?? They would make interesting reading now......the one I read kept by Mr Jack Williams when developing the AJS 7R and E95s certainly was and friends have told me that both Mr Hele and Mr Hopwood wrote them up at the end of every working day..
Of course with a one piece crank and no sludge trap oil is going to get to the big ends a tad faster at engine start up....unless running it on rollers for a few seconds before turning the sparks on....
Decades ago the Crosslad Filters Chief Design Engineer suggested for racing we use a shorter version of their Norton filter but with its smaller area filter that to maintain MAXIMUM oil flow for racing we should change it every 200 racing miles or so. If memory is correct Crossland designed and manufactured the original Norton filter qand its Crossland number was 673 although why the hell I should remember such things..Now IU just have to look up an old letter......I was right...673 was ther Crossland number(79mm long) and the shorter version (59mm) was 2030.... letter dated June 1987.
No spell or grammer etc checks done...the wife doth call......

My 500cc Triumph engine was a 650 in which the billet crank had 63mm stroke and the barrels, pushrods and pushrod tubes had been shortened about 12mm. The crank had a 6mm hole up the middle where the sludge trap would have been. Crank wear was a problem, so I had the journals ground, hard chromed and reground and fitted Morris Mini - Cooper bearings which are a hard alloy of copper lead. The motor always had excellent oil pressure after that. I'd worry about using an oil filter in case it inhibits the oil flow, however if you look at the wire strainer and magnetic crankcase plug in a Triumph engine after it has been racing for a while, there are usually a few bits of metal there. Triumph and Norton motors are the older generation motors. If you own a 60s Honda twin racer, you will know about the necessity for regular oil changes. Quality is all about attention to detail. For a road bike, I'd use an oil filter however not for racing.

Good, if I understand well, in the billet crank there is an oil path to bring oil to both big ends without going threw any sludge trap and limiting a possible pressure drop?

If using a proper oil filter no sludge trap should be needed.

Matchless said:

If using a proper oil filter no sludge trap should be needed.

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+1

Good, thanks.

Do you know if somebody worked on putting an oil filter where it should be, between oil tank and engine?

NKN said:

Good, thanks.

Do you know if somebody worked on putting an oil filter where it should be, between oil tank and engine?

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I'm not aware of a kit for that, you can do it yourself, as I believe Jim Comstock has.

I am a believer that provided you have a filter anywhere in the system it will still perform its task as intended.

Putting it in the return, as per normal on a Norton, is perfectly fine IMHO and has the advantage of being very straight forward.

So... Are you using a billet crank? If so, who's is it? Do tell...

Well oil filter is already set on, with a magnet in the drain plug it should be OK.

And yes I would like to go with a billet one, still looking around and wondering about a lighter one with more stroke? Do you think it could be nice for a street bike?

NKN said:

Well oil filter is already set on, with a magnet in the drain plug it should be OK.

And yes I would like to go with a billet one, still looking around and wondering about a lighter one with more stroke? Do you think it could be nice for a street bike?

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Yes it would be nice IF you can find one.

Maney probably has one of his on the shelf ready to ship...

Jus' sayin'...

If I was about to buy a billet crank, I would be thinking long and hard about what stroke to use. Whatever I thought I might like, I'd try to find someone who is already using that stroke in a racer and pick their brains.

acotrel said:

If I was about to buy a billet crank, I would be thinking long and hard about what stroke to use. Whatever I thought I might like, I'd try to find someone who is already using that stroke in a racer and pick their brains.

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Hehe, that's just what I'm doing, so why not begin here?

If longer stroke gives more torque, why not go to 90 or 91mm?

Even if pistons moving more and getting also barrels worn faster.

Re oil to big ends. Norton Owners Club. Commando Service Notes.............
'The other reason that a pressure guage is not a good idea is really twofold. At high speed and high oil temperatures the pressure can drop to nothing on the guage because the pump can hardly keep up with the rate the stuff is flying out of the big ends. The centigugal force can keep the pressure at the big ends above the danger point, so there's no real panic- but the guage would inspire you with horror.........'
Later the writer, (Quality Manager and then Service Engineer at NVT 1970-74), suggests that anyone who fits a temperature guage into their oil tank should let him know what it reads as they drop into top gear along The Mountain Mile on about the 4th or 5th lap of a TT ......and states ....The latest Racing Nortons (we can't call them J.P. Nortons any more as they've stopped the bikes from smoking) had a new type of oil pump - I wonder if this is because the ordinary pump can't keep up?
Oh rats ......upon reading the above some owners are going to want bigger pumps for their Nortons and thus another FAD is born. Hope whoever makes them gives a free sticker so the posers can place it in their bike ......(One Triumph 3 owner had his ex chain case engraved BELT CASAE a few years ago.... according to the club mag!!)
Out of pure curiousity I have just phoned a Gentleman who has 'a bit' to do with new Norton oil pumps and we had a quick waffle. Easy way would be to use a wider feed gears and accomodate it by removing some meat from the centre of the pump body. (Isnt that what they did to increase the return flow at one point?) Yes every Commado owner needs a bigger oil pump........Wonder what they did to get all this extra oil to go back to the tank?? Wider return gears?? would you then have to increase the size of the pressure release system for whe the oil is cold?? Gosh, yet more RAMIFICATIONs................

Some years back I built a Commando engine for my road race bike using a 91 mm stroke Nourish crankshaft and 80.5 mm bore. I raced it for several years with no problems, using a 7000 rpm red line. I was using stock rods and had no problem with clearance in the crankcase. But you might find a need to grind the inside of the cases a bit for clearance for the con rod bolt heads with some aftermarket rods. I still have the crankshaft, and have considered using it in a street bike, but it was made for racing, and has no alternator shaft on the end. I'd have to weld on an extension, and then machine it for the alternator, and that was more work than I thought it was worth.

Picture of the crankshaft here

commando-crankshaft-porn-t8365.html?hilit=crankshaft

I don't see any reason a 91 mm crankshaft couldn't be used on a street bike to good effect.

Ken

If the stroke of that crank is 91mm, did you get it to that by grinding the big ends offset ? It is obviously not a billet crank.

acotrel said:

If the stroke of that crank is 91mm, did you get it to that by grinding the big ends offset ? It is obviously not a billet crank.

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Of course it is. It's a one-piece crankshaft made by Dave Nourish in 91 mm stroke with stock size rod journals. You are looking at the wrong post? Look down the page to the second post.

Ken

Centrifugal force affects the oil pressure - must be one clever pump to know the cranks rotating. If the crank is full of oil then the pressure in the centre of rotation would be what the pump is supplying, assuming no loss, then the weight of oil a the max radius of rotation would be affected by the centrifugal force and forced out quicker, so sludge trap or not the pressure could vary. The system would not know if it was an open ended pipe or rotating crank so a sludge trap where the oil is stationery and nowhere to escape would not cause lower pressure. Gosh! those boffins in those days at Norton really knew how baffle.

Does the oil pressure figure really matter as long as the bearings float and not pick up ? The crank in my short stroke Triton had chromed journals and bearings which were a hard grade of copper lead. At no time could you ever push the oil indicator button in while the motor was running. This was probably due to clearances - however probably un-necessary. Before I chromed the journals, the wear rate seemed high.

How many commandos have exploded due to seized big ends ? Perhaps we don't need to be paranoid ?

Exactly, I reckon the Commando oil pump will always provide enough volume of oil no matter how worn or it or the shells are. With some out there doing 40K a year with just routine maintenance sort of supports this theory. Irrespective of what crank you use in your Commando the pump will have no problem supplying sufficient oil.