Clutch Slippage; part (enter your number here)

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Re: Clutch Slippage; part (e1nter your number here)

J. M. Leadbeater said:
I am amazed at the total LACK of knowledge of the owners posting on this subject. Did non of you learn in 1st year Mechanical Engineering classes how to calculate clutch torque capacity requirements along with in theory actual clutch torque capacity ??? Clearly not if the posts are any indication because if you did you would be fully aware that Commando clutches like all Norton clutches(!9s..Mod 50. ES2. 77. 88. 99. 650. SS. Atlas from the mid 1930s on were DESIGNED to be employed dry with no oil or oil mist on the friction interfaces.
Do any of you know the Coefficient of Friction values of the various friction materials employed on Commando friction plates??? Clearly not. A rule of thumb for friction materials is that the dry value is 3 to 4 times greater than it is with oil mist or oil on them thus any clutch designed to be employed DRY will with oil mist / oil on the friction interfaces slip when oil reaches the friction interfaces ASSUMING the rider applies a tad of torque to the clutch..
EXAMPLE..Original 750 Commando clutch . Some back of fag packet quicky calculations
1 The required clutch torque capacity if it is not to slip when MAX crank torque is put through it. Max crank torque is shown as 48 ft lb. The primary sprockets are 26t - 57t thus MAX torque at the clutch = 48 x 57/26 = 105 ft lb. To this a clutch designer applies a safety / service factor and a rue of thumb one for clutches is to use x 2. Thus the clutch requires a torque capacity of 210 ft lb.
2 The in theory torque capacity of the clutch. It employed 4 friction plates giving 8 friction interfaces. The effective radius of the friction interfaces was approx 0.205 feet (ft). The friction material employed was Ferodo MS6 for which Ferodo list the Coefficient of Friction values to be employed for design purposes as Dry 0.34. Oil mist 0.1 - 0.12, In oil 0.09. The ORIGINAL diaphragm spring employed was 0.075 +/- 0.0015 inch thick and CORRECTLY set up applied approx 380 pounds force (lbf) clamp load to the friction interfaces. Thus the in theory torque capacity of the clutch was.....
DRY..........8 x 0.205 x 0.34 x 380 = 212 ft lb.
OIL MIST. ....8 x 0.205 x 0.1 - 0.12 x 380 = 62 ft lb - 75 ft lb.
IN OIL........8 x 0.205 x 0.09 x 380 = 56 ft lb.
GOSH with a required torque capacity of 210 ft lb and an in theory DRY clutch torque capacity it was clearly a very well designed (torque capacity wise) designed to be employed DRY clutch.

For that vastly even more overweight unbalanced gearbox breaking flywheel Norton called 'the clutch ' on later models the Diaphragm spring had been changed for the THIRD time in thickness to give a greater clamp load in a totally failed effort to solve the serious clutch slip problem and the spring thickness was now 0.084 +/- 0.0015 inch and gave a clamp load when correctly set up of approx 550 lbf. The rule of thumb Coefficients of Friction for sintered bronze are DRY 0.3 and WET 0.06 -0.08 and the Chief Clutch Designer of Laycock Engineering who designed the original Starmaker diaphragm spring clutches and diaphragm springs along with all the 4 different springs employed in Commando clutches along with a further different spring employed for rotary Norton clutches used 0.06 for ALL his with oil sintered bronze friction material clutch designs stating to me that the use of 0.08 was being optimistic.......
I will leave you to play with the calculations for that bronze plated LUMP but would remind you that the qualities a motor cycle gearbox mounted multi plate friction clutch is SUPPOSSED to possess are that it should .....
1 NOT slip when fully engaged, even when hot.
2 Free off nstantly without drag when ever required by the user, even when hot.
3 Be EASILY operated by the user at all times.
4 Possess the LIGHTEST rotating weight reasonably possible.

Clearly on 4 alone the lumps fitted as standard by AMC / NVT are NOT clutches!! A clutch being the lump fitted to every car I have owned or driven.
3
Click to expand...

DILLIGAF?
 
bill said:
looks like our beloved beltdrive man is back :lol:
Click to expand...

Oh dear, have I responded to a surreptitious marketing/sales pitch?
Ta. :cry: :x
 
Re: Clutch Slippage; part (e1nter your number here)

J. M. Leadbeater said:
I am amazed at the total LACK of knowledge of the owners posting on this subject. Did non of you learn in 1st year Mechanical Engineering classes how to calculate clutch torque capacity requirements along with in theory actual clutch torque capacity ??? Clearly not if the posts are any indication because if you did you would be fully aware that Commando clutches like all Norton clutches(!9s..Mod 50. ES2. 77. 88. 99. 650. SS. Atlas from the mid 1930s on were DESIGNED to be employed dry with no oil or oil mist on the friction interfaces.
Do any of you know the Coefficient of Friction values of the various friction materials employed on Commando friction plates??? Clearly not. A rule of thumb for friction materials is that the dry value is 3 to 4 times greater than it is with oil mist or oil on them thus any clutch designed to be employed DRY will with oil mist / oil on the friction interfaces slip when oil reaches the friction interfaces ASSUMING the rider applies a tad of torque to the clutch..
EXAMPLE..Original 750 Commando clutch . Some back of fag packet quicky calculations
1 The required clutch torque capacity if it is not to slip when MAX crank torque is put through it. Max crank torque is shown as 48 ft lb. The primary sprockets are 26t - 57t thus MAX torque at the clutch = 48 x 57/26 = 105 ft lb. To this a clutch designer applies a safety / service factor and a rue of thumb one for clutches is to use x 2. Thus the clutch requires a torque capacity of 210 ft lb.
2 The in theory torque capacity of the clutch. It employed 4 friction plates giving 8 friction interfaces. The effective radius of the friction interfaces was approx 0.205 feet (ft). The friction material employed was Ferodo MS6 for which Ferodo list the Coefficient of Friction values to be employed for design purposes as Dry 0.34. Oil mist 0.1 - 0.12, In oil 0.09. The ORIGINAL diaphragm spring employed was 0.075 +/- 0.0015 inch thick and CORRECTLY set up applied approx 380 pounds force (lbf) clamp load to the friction interfaces. Thus the in theory torque capacity of the clutch was.....
DRY..........8 x 0.205 x 0.34 x 380 = 212 ft lb.
OIL MIST. ....8 x 0.205 x 0.1 - 0.12 x 380 = 62 ft lb - 75 ft lb.
IN OIL........8 x 0.205 x 0.09 x 380 = 56 ft lb.
GOSH with a required torque capacity of 210 ft lb and an in theory DRY clutch torque capacity it was clearly a very well designed (torque capacity wise) designed to be employed DRY clutch.

For that vastly even more overweight unbalanced gearbox breaking flywheel Norton called 'the clutch ' on later models the Diaphragm spring had been changed for the THIRD time in thickness to give a greater clamp load in a totally failed effort to solve the serious clutch slip problem and the spring thickness was now 0.084 +/- 0.0015 inch and gave a clamp load when correctly set up of approx 550 lbf. The rule of thumb Coefficients of Friction for sintered bronze are DRY 0.3 and WET 0.06 -0.08 and the Chief Clutch Designer of Laycock Engineering who designed the original Starmaker diaphragm spring clutches and diaphragm springs along with all the 4 different springs employed in Commando clutches along with a further different spring employed for rotary Norton clutches used 0.06 for ALL his with oil sintered bronze friction material clutch designs stating to me that the use of 0.08 was being optimistic.......
I will leave you to play with the calculations for that bronze plated LUMP but would remind you that the qualities a motor cycle gearbox mounted multi plate friction clutch is SUPPOSSED to possess are that it should .....
1 NOT slip when fully engaged, even when hot.
2 Free off nstantly without drag when ever required by the user, even when hot.
3 Be EASILY operated by the user at all times.
4 Possess the LIGHTEST rotating weight reasonably possible.

Clearly on 4 alone the lumps fitted as standard by AMC / NVT are NOT clutches!! A clutch being the lump fitted to every car I have owned or driven.
3
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Clutch Slippage; part (enter your number here)


Norton clutch design and be damned, the laws of physics refuse to bend for anyone. Chains need lube. Bearings need lube. Wet clutches work splendidly. It appears the Commando 850 clutch is sufficiently designed for wet use with fibre plates. The much ballyhooed and vaunted "just a smattering of oil on the primary" level plug is so much bs. JMWO :mrgreen:
 
Re: Clutch Slippage; part (e1nter your number here)

J. M. Leadbeater said:
I am amazed at the total LACK of knowledge of the owners posting on this subject.
Click to expand...
Thank you!
Your posts may be long but rich with content.
That being said, a sense of deja vu is a bit overwelming.
 
Just when the forum was going through a quiet patch !

Please keep posting Mr JMB, for entertainment value if nothing else.

And please do accept most sincere apologies on behalf of all the half wits like me who failed to realise there was a specific degree required before being allowed to own a Norton !
 
J. M. Leadbeater said:
I am amazed at the total LACK of knowledge of the owners ...
...A clutch being the lump fitted to every car I have owned or driven.
3
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Blah-blah-blah. What are you trying to say? I see no summation, other than the Norton clutch is a lump. That's very helpful input! Y'know, Honda made a couple of models in the Seventies with a torque converter. Maybe one of those would be more to your liking.

Now, where were we? Oh, yes; After putting about fifty town miles on the new Barnetts, I was able to run her out in my favorite stretch of road this morning. NO SLIPPAGE! We were blasting through 90 when "reason" came into play, but that was enough to tell that the new plates are working fine. Now, it'll just take some miles to determine how well the center dogs wear, as this is a concern expressed by other members. Updates to follow.

Nathan
 
Being rude to Mr Leadbeater is all well and good, but would it be fair of me to point out that this thread started with a complaint about a Norton clutch's chronic slipping problems?
 
Triton Thrasher said:
Being rude to Mr Leadbeater is all well and good, but would it be fair of me to point out that this thread started with a complaint about a Norton clutch's chronic slipping problems?
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I think that's fair TT. And JMB posted some very relevant and interesting info, so I for one do hope he continues to post.

And I'm sure that he knows all too well, that being provocative is likely to provoke !!
 
All I know is mine slipped when it hit the fat part of the power band with the bronze plates and doesn't slip with the Barnett fiber plates. It's not rocket science, it's an old motorcycle. The only thing lacking is space in Mr. Meat Beater's mind for any experience other than his own. I have a couple of ex-friends who are exactly like that. Ritalin is a helluva drug.
 
On a slightly different slant, (and I'm afraid, just a leetle bit about oil :roll: in the primary) We who have MK3's can't get away with ATF as it's too thin to properly allow the hydraulic chain tensioner to work. Same as in my engine, I use 20w50 Mobile 1 V twin. Original handbook spec'd the same weight oil for engine and primary and that's what is working for me. Original bronze plates still fine at 50k. I had been plagued with yearly sticking (not so much slipping) clutches and cleaning would bring back good performance for a while. This was when using GTX 20w50. Switching to bike oil has given me 3 seasons with out having to monkey with the clutch and the primary is quiet and presumably happy too.
 
What I am saying is that Norton clutches were DESIGNED to be run dry. If oil enters the clutch and owners shove some real torque through it they will suffer from slip problems plus the oil results in stiction and you end up having to free off the clutch before firing up the engine. This clutch freeing off before starting the motor was recommended by Triumph in their manuals. See the Triumph Workshop Instruction Manual for models from 1945 to 1955 page 20 which states.....'Lift the clutch lever and depress the kickstarter two or three times to separate the clutch plates' . If you had to free off the clutch every time before starting your car you would soon realise what a pain it is and even more of a pain when having to strip out the clutch to free it off as was often the case in my younger motor cycling days. At Triumph a certain Manager told me workers would park their bikes leaning against walls so the clutch lever was pushed back to the bar and give the kickstarter a few jabs to ensure the plates were freed off and would still be freed off when their shift ended and they went home. At BSA the 'younger ' employees had a competition to see who could ride their bike the furthest before the clutch freed off on its own..so a friend who served his time there and was one of the very last to go after he helped machine and build the last batch of B50 motors.
When in the 1930s Norton EVENTUALLY decided to incorporate a primary oil bath chain case so as to give the chain a better form of lubrication than mud, water, stones and on the odd occasion human flesh and bone one of the Gentlemen tasked with designing it was Mr Phil Heath and MANY years ago he told me the history of how it was quicker and cheaper to simply basically shove ta dry clutch within the new very clever oil bath chain case. To stop oil or oil mist from entering the clutch they placed the oil level plug very low down such that oil at the CORRECT level just touched the bottom of the chain in service creating an oil mist for chain lubrication and placed around the basket a band refereed to in the parts books as an OIL EXCLUDING BAND. If you read the Gold Star History book you will read that the CORRECT primary oil level is till oil can just be seen to be touching the bottom of the chain and on page 130 in the copy of the B31 Gold Star publicity bumph sheet it states that the clutch is a 'BSA multi dry plate clutch'. PLUS the frictionmaterial employed for several years before Ferodo MS6 was developed the Gold Star clutch employed Ferodo MZ41 friction material and its data sheet only lists a DRY Coeff. of Friction value for design as 0.41 also stating that it is unsuitable for use with oil.....Of course the whole idea of shoving any clutch within an oil bath chain case is correctly described by the staff of The Motor Cycle in their book 'Speed and How to Obtain It' as and I quote 'FRANKLY A COMPROMISE' with the suggestion made that 'A MUCH BETTER IDEA' is to employ the chain within the oil bath chain case along with lots of oil to lubricate AND COOL the chain but to employ the clutch externally beneath a cover so it can be run DRY. This of course is how Ariel did it but it would of required Norton to redesign lots of components to do so at a time of major recession when there was little or no money around or time available to do it when bike sales were low due to them having a very old road model range.
At NVT I understand from various friends who worked there that Mr John Hudson as Service Manager became so annoyed with customers complaining of clutch slip that he took a Commando and cutting up a chain case outer and inserting some perspex took a good look to see exactly what was happening which led to the instruction given at the end of Section K8 in my workshop manuals ' Note, under no circumstances allow more than 7 fl oz ( 200cc ) of oil in primary case'. Of course the idiots at NVT failed to change section K9 as they added the amendment and section K8 and section K9 which tells owners to fill till oil escapes through the oil level plug and on the Commando I measured with oil to the level plug it contained approx 290cc of oil. Plus of course owners use oils containing friction inhibitors which is exactly what you do not need on the friction interfaces!! Not that many if any have thought about this.
Just for a laugh now that you should know how to calculate the in theory torque capacity of an original 750 Commando clutch go play and calculate how many friction plates it would of required if it were designed to work correctly with oil mist or oil on the friction interfaces. Now ask yourself how with so many friction interfaces each requiring approx 0.005 inch separation if they are to free off correctly you would ever get such a lift without a VERY expensive redesign of the lift mechanism for a motor cycle that was only to be a stop gap model for two years production while new models were designed developed tested and put into production...... Then do the calculation again using 4 friction plates (8 friction interfaces) and calculate the clamp load required if the clutch were designed to be run with oil and remember that the last diaphragm spring employed ( 0.084 +/-0.0015 inch thick)applied approx 550 lbf clamp load and resulted in wrist and hand ache for owners (IF the diaphragm spring is set up as it was designed to be set up with the clutch fully engaged)so how the hell would you ever free off the clutch with the clamp load required!! the answer is that you would not do so unless you redesigned the lift mechanism to hydraulic operation costing time and money and delays to production.
Personally in my very olde age I find it incredible at the lack of Engineering knowledge among owners. It really is not hard to learn. Tis no wonder that the U.N. found the UK to be 22nd for literacy and numeracy in the World with America 23rd. Mind you with Engineering not even being considered a worthwhile occupation for so many years is it any wonder the UK and the USA are owned by every one else!! 'Become a poxy accountant or banker son and screw the World and making lots of money '...or evn a bloody useless politician!! Tee Hee.
The whole beauty of employing a belt instead of a chain on a Dommy or Commando T140 / A65 etc is that it allows any owner to obtain a CORRECTLY working clutch IF the belt system is CORRECTLY designed manufactured and fitted and there in laysa problem which is why I DO NOT make and sell diaphragm spring clutch belt systems to the general public and I have 'designed and made them for Tiger Cub road, race and trials bikes , All the unit BSA single range Commandos Triumph twins A65s etc etc over the years BUT ONLY for friends who seriously twist my arm till I do so. As one Motor Cycle magazine wrote for the belt primary system put together for a friends 6T being tested...'it was a revelation' No slip, no drag, very easy two finger operation no oil leaks less vibration and noise levels along with greater efficiency(as testing in the 1980s clearly demonstrated.
Personally my olde 59 ES2 chain primary gave no problems apart from a periodic maintenance ONCE i realised the olde seal was so old it was a lot thinner than it should be resulting in leaks nut a new thicker seal INSTANTLY cured that problem. Tis amaxing how much thinner the old seal was.......
 
J. M. Leadbeater said:
Plus of course owners use oils containing friction inhibitors which is exactly what you do not need on the friction interfaces!! Not that many if any have thought about this.
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Actually, I think you'll find a lot of us have thought about this. Just look at the number of threads that make mention of F-type ATF for the primary drive, and to not run anything with mileage enhancers/friction inhibitors in them.

My '72 T150 had a separate, sealed clutch housing that contained, of all things, a SINGLE plate dry clutch! And, no, it never slipped. Since the clutch is torque-limited, why not run it on the end of the crank? Most people's first reaction is something along the lines of "Horrors! How could you put something that large/heavy on the end of the crankshaft?" Well, the clutch could be substantially smaller/lighter than it currently is, since it wouldn't have to be fighting against the torque multiplication afforded by the primary gear reduction (chain). And you now remove the horrendous mass from the input shaft of the tranny by running a skeletonized sprocket only. Hodaka did this very effectively in their dirt bikes during the Seventies.

Now with over two hundred miles on the clock, and still loving the Barnetts!

Nathan
 
My bronze plates slip the first time I thrash it but for the rest of the ride it will then run perfect, this is with some Malaysian cheap oil designed for Japanese motorcycles with wet clutches. I bought as it was available at the time, far cheaper than ATF and would be used in the XL250 I had. I know some other motorcycles use a conversion that use a smaller clutch surface with the same spring tension, would wear quicker I assume.
I did laugh when I saw the comment on the torque converter, I once saw a MG Convert at the MOT station, the owner said, though heavy, it was actually nice to ride. My preference would be the VW DSG with selectable tip system if it could be miniaturised for use on motorcycles, but then again the engines in some tourers and cruisers are larger than my Fabia DSG.
 
J. M. Leadbeater said:
At NVT I understand from various friends who worked there that Mr John Hudson as Service Manager became so annoyed with customers complaining of clutch slip that he took a Commando and cutting up a chain case outer and inserting some perspex took a good look to see exactly what was happening which led to the instruction given at the end of Section K8 in my workshop manuals ' Note, under no circumstances allow more than 7 fl oz ( 200cc ) of oil in primary case'.
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It was Mr John Nelson according to last month's version?
primary-oil-level-t22141-15.html#p290054
 
Ugh, I have had enough clutch oil contamination on P!! and 2 Combats before switching to ATF to know oiled plates tend to stick together on first starts not slip. The only clutch slip I experienced was on 74 850 in 3rd and helped by cleaning plates but did not complete solve. When chain is set properly loose enough the lube should only touch mid way into the links, or just fill as much as can and ride till reaching its innate level not to flood clutch, weep out anywhere further.
 
J. M. Leadbeater said:
...plus the oil results in stiction and you end up having to free off the clutch before firing up the engine...
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'Same for my BSA B50 MX, which ran engine oil through the primary. HOWEVER, the Norton has never suffered this, assumedly due to the ATF that's always resided in her primary drive. It's funny that my start-up routine still incorporates freeing the clutch, even though it doesn't need it. Old habits die hard... :roll:

Nathan
 
Mr Leadbeater,

Most Norton riders on this forum just enjoy riding. They don't have engineering degrees. If you are nice to them they will be nice to you.

Your calculations were spot on. You stayed awake in engineering school. I will translate. It appears Norton knew about the clutch slip problem and just put many band aids fixes on it. To not slip your clutch must be set up perfectly. This means cleaning and rough up of steel plates.

You want the most plates (5). You want the highest force (thickest) diaphragm spring. You want the least amout of oil on your plates you can get away with. ATF Type F is less slippery than motor oil. Friction force barely holds everything together under normal operation and something like a little gear oil seeping in will cause slippage.

Hopefully Nathan will have continued success with his Barnett plates.

Baldy
 
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