Crankshaft alignment

The crankshaft studs I've used are from RGM and measure 0.310", The ones I origionally took out measure 0.312"!!!

" both tipping into the centre so I presume that the crankshaft cheeks aren't parallel - is this normal? "

Get a Bigger Hammer !

er , aligning a Vee Twin crank , a large mallet is the trick .
Seating , settling neutral ! , ' aligning ' seated ! is the lark .

Throwing the halves at each other , throwing in the bolits ,
and tourqing em up , Just aint goodenough . Perhaps .

a carefull sod would shuffle and ' centralise ' the assembly , at the just about nipped , stage . THEN getout the measuring gear .

But however , really cunning swine , setit up precambered . As a stock crank jiggles . We wont it when its at the extreme STRAIGHT .
It can get backward unloaded . Or backed off . But iffits under maximum duress aligned ( running ) more go's gunna gettout .

Cording to the theory of minimissing internal losses .

Wether we were just lucky ? was 2 1/2 thou. precamberd mainshafts . equalspaced , 4 at the end of the long one . Same if there opposite on the thread .

As the theory's 4 1/2 measured ( factory ) at the flywheel . This might cut it down to one thou runout full wellie . Not much'd argue with it , anyway .
Wernt machining marks on the flanks . Pecautionary touch with grinding paste on glass gave zero irregularity on flank machining witness . Therefore ? .



Id sayitwass tipping out , tho never checked crankpin alignisation . If they were parralel to mainshafts they were . opposite yours infact . seeing you asked .

Id stayed clear when Len'd got at it . but did witness the MALLET for a few blows . Was a ' dark art ' but as'ed built the L.S.R. record injun , figured E might know whateees uptoo . Like wot thisis peraps .
( I was wishing I was clear , on the " Hold this " Commando Frame Vs rubber Sledge Hammer , on the back lawn . Visualise a sculpture & granite . Theres a knack toit .

As food for fought , at least . Mon .

I think I tought he said ' within a half ' preferably . But you can getem beter than that . WITHIN ONE , anyway . Belive it was two hours for excellent , maybe ten for perfect .That was the problem with the kwackersaki KR tripeles , theyed throw out if less than straight , and take the rest withem .

So the tuners creed from experiance , wear , witness marks ( He was the H.R.D. Franciseee ) would havem STRAIGHT operating rather than static .

Nourish said:

OK, I've split the cases again and put the cranshaft up on V blocks via the main bearing inners. With the crank pins uppermost I've zero'd the DTI to the T/S crank pin outer side, then moved the clock across to the inner side and I'm getting a reading of -0.0001", across to the D/S inner I've got -0.0038" and the outer -0.0036".
Turning the crank over 90 deg using a vernier height guage in a balancing hole in the flywheel to keep it still. I measured again the height of the pins I zero'd on the T/S outer and measured +0.0003" on the inner side, -0.0054" D/S inner and -0.0050 on the D/S outer.
The journals were ground seperated from the flywheels and presume then that there is movement around the location dowel and the two locating studs?
Next step I suppose will be to strip the crank down again and investigate more!

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You next step is good, but if you have access to a lathe: Remove the main bearing inner races, split the crank, chuck each cheek of the crank (one at a time) and dial in the bearing race area. Then do your tests to the journals. If not dead straight, they were ground canted and must be reground correctly.

Fast Eddie said:

I was once told by Mick Hemmings that it was fairly common for Commando cylinders to be machined out of true and that this often lead, or at least contributed to ‘mysterious’ seizures.

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Interesting - that would not be hard to measure in this case since both pistons are tipping towards center.

P 287 / 288 here , gives you somebodys interpretation of some of the forces & parameters in steel cranks & alloy cases .


Crank Mainshaft Alignment was over 1/4 thou. missalignment unacceptable .
' Pulling one down ' in this case Pulling the Nuts Up ' on the Vin . ' a good one might go togeter in 40 mnutes .
Two Hours , thats with wipeing your hands & putting the Jug On . " long tea or short tea " ( Thats poured high , or poured low ! )

But , as stated , a ' aligned ' one , may be aligned OTHER THAN DEAD IN LINE . By Intent .

The cross / parralelity , of the MAINSHAFTS was stated ' 1/4 thou . " again . The Tigtening on fresh components pulling ,
so needed setting to pull into alignment , as tightening . BUt on a Commando / Parrallel Twin CRANK ;

A good ' fitter ' can Hand Lap faces , to align as required . the Center / Flywheel faces , want checking for parralelity / squareness etc ,
as theyre The BASE , that the throws seat upon . So carefull primary check / set up THERE FIRST , so if that were out , & you didnt ,
youd be barking up the wrong tree , for starters .

But Id craefull check the mainshafts ( Bearing Seats ) are not only parralell but concentric , at the inner bearing seat face . ( one shafts NOT kicked off sideways , laterally )

AsIsaid , 2 1/2 thou. of BOW - outward - measured equidistant - first on the short machined end : may see the piston thrust seeing it STRAIGHT upon the power stroke ,
which'd BE the max. load input thrust initiation ! .

Thus , in a PLANE through the throws and shafts , its all true . it's only pre cambered in the vertical plane . ( when at T or B D C )

Steel Blocks , a surface plate ( Plate glass cast off from window outfit ) and a feeler guage , sighting - with strong light behind . Not to mention engineers Blue , your in buisness .

A megatron osciliscopes not really neccesary . asin , seated & nipped , a mallet might ' fine tune ' minimalist eccentricity , so as to get it all true in the plane thru the centers .
checking as you go each stage , pulling the bolts down ! or start & finish , at least .

Nourish said:

I've assembled the crankshaft into the cases on my 850 engine - fresh grind, new mains, new shells, new AN conrods, N.O.S Hepolite pistons(std), new liners fitted. I noticed that the T/S piston wasn't level with the top of the Barrel. The barrel head face is parallel to its base. I've put a drop clock on the head face of the barrel and and zero'd the clock on the outer side of the D/S piston, Moving the clock across to the inner side of the same piston I got -0.004", inner side of T/S piston -0.0015 and outside of this piston +0.007". So the D/S piston is tipping over 0.004" and the T/S 0.0085" - both tipping into the centre so I presume that the crankshaft cheeks aren't parallel - is this normal?

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you're talking .0045" diff - that's not so bad with stock parts and not enough to worry about. My 750 with stock parts was out enough so that it was obvious to the eye.

Les Emery used to say that many cylinders were originally ( wrongly!) made with the top and bottom mating faces not quite parallel , 4 or 5 thou across the width?

When I bought my Commando new in 1974 in France , the dealer was used to dismantle the cylinders to check them about that and said to me that's why they made the 0.10 pistons to correct any misalignment , he was a real Triumph dealer but in 1974 he was obliged to deal with NVT and work on Norton so may be he was a bit biased , the same declined to work on my previous BSA unit A 50 .... a real Triumph guy!

Well I sent of and waited for a pair of crowsfeat adaptors - when eventually they arrived I realised I should of ordered 1/2" and not 9/16" So ordered and waited for the one 1/2" crowsfoot. I couldn't get my torque wrench in there using the 1/2" crowsfoot. Ok I'll make one. So I milled a bit of 1" square bar down for the 3/8" drive, drilled 19.5 mm hole 2 1/2" from the drive to file out the 3/8" square hole - couldn't fit it in using a 1/2" socket. So I ordered another 3/8" drive 1/2" socket to reduce its length but I grew impatient - F*ck it - I cut a cranked ring spanner in two and slotted a 3/8" drive socket to it - worked perfect!
So ignoring Mick Hemmings advice I torqued the crank together again in stages to 25lb/in and using Andover Nortons locating studs. I put the crank up on V blocks again and found that the journals are parallel and not tipping in . The drive side is 0.0037" down on the T/S and turning the crank over 90deg the D/S is some 0.004"down on the T/S. I've got to undo the studs again and to locktite and and fit the tab washers so I'll see if I can manpulate it to see if I can get it a bit closer.
Whilst on the subject is locktite enough or is it best to centre punch the threads on the studs - if so I presume then that tabs need to be bent over on the locktabs?
Cheers

Nourish said:

Well I sent of and waited for a pair of crowsfeat adaptors - when eventually they arrived I realised I should of ordered 1/2" and not 9/16" So ordered and waited for the one 1/2" crowsfoot. I couldn't get my torque wrench in there using the 1/2" crowsfoot. Ok I'll make one. So I milled a bit of 1" square bar down for the 3/8" drive, drilled 19.5 mm hole 2 1/2" from the drive to file out the 3/8" square hole - couldn't fit it in using a 1/2" socket. So I ordered another 3/8" drive 1/2" socket to reduce its length but I grew impatient - F*ck it - I cut a cranked ring spanner in two and slotted a 3/8" drive socket to it - worked perfect!
So ignoring Mick Hemmings advice I torqued the crank together again in stages to 25lb/in and using Andover Nortons locating studs. I put the crank up on V blocks again and found that the journals are parallel and not tipping in . The drive side is 0.0037" down on the T/S and turning the crank over 90deg the D/S is some 0.004"down on the T/S. I've got to undo the studs again and to locktite and and fit the tab washers so I'll see if I can manpulate it to see if I can get it a bit closer.
Whilst on the subject is locktite enough or is it best to centre punch the threads on the studs - if so I presume then that tabs need to be bent over on the locktabs?
Cheers

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If I understand you correctly, the crank is not (at least not now) involved with your initial problem but it is causing a slight timing issue for TDC - one piston getting there before the other.

On your questions, you'll get many opinions/thoughts, here are mine:
1) Once torqued, the nuts and bolts must not be reused. I follow this but am not sure I agree that it's true.
2) I never use Locktite on them and if I did, I would reduce the torque as any lubricant increases the actual torque. I make sure the threads are clean and oil free.
3) I bend the tabs because the workshop manual says to. Many disagree and insist that the factory didn't. I think the factory did and then stopped at some point.
4) Four positions require nothing special to torque. A right-angle adapter (NOT crows foot) makes the other two easy to do. I doubt that the factory worried about torque on those.
5) I do punch the threads but doubt that it is needed.

I can't imagine that 0.0037" would be a problem with the ignition timing.
Isn't the reason for not re using the flywheel nuts is that the thread is damaged undoing them from the 'punched' stud/bolts?
The 25lb/in torque quoted for the crank nuts - is that dry or lubed?

Nourish said:

I can't imagine that 0.0037" would be a problem with the ignition timing.
Isn't the reason for not re using the flywheel nuts is that the thread is damaged undoing them from the 'punched' stud/bolts?
The 25lb/in torque quoted for the crank nuts - is that dry or lubed?

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The torque is dry. If you haven't, look here: https://www.gregmarsh.com/MC/Norton/NortonTorque.aspx

As far as the ignition timing, I said slight. I hope the old brain is working today:
Stroke 3.503" so 3503 thousanths
You said the difference is .0037" so 3.7/3503 = .00106
360 * .00106 = .38 degrees so very slight.

I have no idea why the bolts/studs and nuts are not supposed to be reused. Certainly if staked both the nuts and bolts/studs are damaged. It may have to do with that, or it may have to do with stretch, or is may just be an urban legend.

The MK3 Workshop says Locktite and 30 ft lb.
The pre-MK3 says 25 ft lb.
Neither says staked
Neither says new bolts/studs and nuts.
Don't know where I read/heard to use new - sure would like a definitive answer - tired of paying for new sets!

Thanks Greg that's very handy - https://www.accessnorton.com/Norton...www.gregmarsh.com/MC/Norton/NortonTorque.aspx

In the Mick Hemmings video he recommends replacing the crank bolts/nuts/studs as he had seen one break and take out the conrod but nothing about replacing them once they'd been torqued. He didn't use Loctite but he did punch the top ones.
Punching the UNF studs isn't easy as with UN thread forms the first few threads are removed to the base diameter so you can't (well I couldn't!) get your centre punch into the thread form.