brittle norton sprocket failiure

peter james owen

Joined
Apr 29, 2014
Messages
43
I bought an engine sprocket form a cumbrian norton supplier for my P11 22t,it failed after just 1,500 miles.I was thrown off the bike doing damage to me and the bike,then guess what the company say it was poorly fitted and the bike is not suited for their sprocket,they took my money quick enough.
So be aware that they sell not fit for use parts,and if they fail they do not want to know.
Has any one else had this problem ?
 
peter james owen said:
I bought an engine sprocket form a cumbrian norton supplier for my P11 22t,it failed after just 1,500 miles.I was thrown off the bike doing damage to me and the bike,then guess what the company say it was poorly fitted and the bike is not suited for their sprocket,they took my money quick enough.
So be aware that they sell not fit for use parts,and if they fail they do not want to know.
Has any one else had this problem ?
Click to expand...
Wow!
Without wishing to tempt fate here, I've never seen a sprocket fail like that!
A tad worrying, do you know for sure that the material was brittle, meaning, have you had it tested somehow?
It would be interesting to know as I'm guessing there's a few people on this forum with sprockets from said supplier, myself included.
 
Yes, if the sprocket physically tore apart then that can ONLY be a materials failure/ serious manufacturing defect.

If that is the caee, you need to speak to a good lawyer that specialises in such stuff, with sprocket bits in hand.
A friend had a bike-dealer-induced bike failure that threw him down the road, and after some serious legal rubbish,
they handed over wads of cash, and an apology. Their insurance should cover them for such things.....
It never replaces the bone that was ground away, however.

Show a pic of said sprocket here, that should get the ball rolling.... ??
 
Dam that hits us all hard to read about. Is the P11 sprocket 520 chain size like the Altas? P11 parts are pretty hard to come by and spinal after effect can take some time to show up with faster decay and mysterious dysfunctions. Legal fights are mental money emotions stressor too with lasting anxiety to ride again.
 
The company that made these sprockets must seriously have got either the hardness of the sprocket wrong, and should be covered by Small Business Public Liability Insurance;
http://www.bing.com/search?q=Small+Busi ... &form=QBRE
I am no legal expert, you should have cause for legal redress.
I would keep the original sprocket and get it hardness tested, and analysed by a qualified engineer.
 
peter james owen said:
I bought an engine sprocket form a cumbrian norton supplier for my P11 22t,it failed after just 1,500 miles.I was thrown off the bike doing damage to me and the bike,then guess what the company say it was poorly fitted and the bike is not suited for their sprocket,they took my money quick enough.
So be aware that they sell not fit for use parts,and if they fail they do not want to know.
Has any one else had this problem ?
Click to expand...

That'll be RGM? I've used them in the past but don't think I'll bother from now on. Blaming it on incorrect assembly is a typical get out clause. If the part's less than 12 months old from date of purchase it should be covered by their guarantee but if you're seeking damages I guess you'll need specialist advice. If the P11 uses the same gearbox as a Commando then they're on dodgy ground stating the sprocket is not suitable. The onus here is on you to prove the sprocket is not fit for purpose and you'll need to get an independent report by a metallurgist/engineer stating the metal composition of the sprocket, hardness and it's suitability as a sprocket and also why it failed.

I've been ripped off once before and started legal proceedings via the small claims process but gave up thinking I'd stand no chance of winning. With hind sight I wished I'd pursued it now having experienced as a witness the small claims procedure. You'd have to check what the max. limit is the small claims can award. Either way if you know you are in the right then go for it and good luck. Many business's get away with dodgy practice because people don't seek legal recourse, don't be afraid of the legal system - it's there to help you.
 
Yes I had the sprocket analysed it was done overnight The cumbrian supplier had not done this in three months,it was made in birmingham of 58 rockwell,ideally it should be EN24,but 58 rockwell is OK!!.
It had been well over hardened creating the brittleness.!! ,sombody left it in the vat too long. a lot of people I know in the motocycle world had ever seen anything like this,one a well respected bike racing tuner and manx GP winner,the other are the guys from supremes Earl shilton, another is an engineer at MIRA vehicle test facility near Nuneaton wark's,where I used to work.
The primary chain is 520,a lot different to a commando which is triplex,it was checked for alignment using a steel rule and was quite close,the clutch chain wheel does move a little bit but it was OK for me,it was checked for alignment as the P11 use a lot of spacers in the engine/gearbox to frame plates.[oh by the way anybody rebuilding a P11, put the oil tank in first,but check there are no leaks].
The broken sprocket sheared off starting at the woodruff key slot,there is a different boss to sprocket radii,looks a bit thinner than the three old original sprockets that i have,I bought a new sprocket 22T as I wanted to gear up for normal roadwork[I wished I had not done it now].
 
EN42 refers to a grade (alloy mix) of steel whereas Rockwell is one of the scales used to measure hardness so I'm a bit confused by your references. I don't know what is a suitable material for an engine sprocket or how hard it should be. I would have thought AndyChain would be able to help you here. Sprockets should cope with misalignment, although not ideal, but they certainly shouldn't fail. I misread your original post and thought it was the gearbox sprocket which had failed. Have RGM now admitted liability and compensated you? Must have been quite a bit of damage.
 
I also thought you were referring to a gearbox sprocket. I'm no solicitor, nor trader, but in my humble layman's opinion, the crank sprocket is an entirely different can of worms... For example...

Has the crank taper been ground incorrectly, altered, damaged? before you say "no" remember it is what, 50 years old, and has had how many previous owners?! Did you use a slightly incorrect key, too high, too sharp, too hard? Did you over tighten it? All these things would put stresses on the sprocket outside of its designed tolerance.

Plus, you say you aligned it with a rule and it was not bad, how bad is not bad? How bad does it have to be before it is too bad? Can you prove this?

My real point is this: if this goes to court, and the vendors insurance company uses its highly paid legal team, a team who specialise in NOTHING but trying to avoid or minimise payouts, they will have a field day opening this can of worms... at your expense.

Are you prepared to get into such a long, stressful, costly, legal battle?
 
so true Eddie, there are many things that could cause the eng sprocket to explode that would not happen on the gearbox sprocket and hardness or material may not be one of them, or it could be a combination of a lot of things. But certainly finding out if others have had the same problem may tell a different story and by mentioning it on this forum and elsewhere
may enlighten us. the dealer in question is held in high regard for quality parts and service.
 
Its under English court system so by selecting the Small Claims route the costs claimable are restricted but so also are the costs the defendant can pass back if you lose. A consumer friendly route that means the costs are effectively limited to how much you spend on your side on independent expert reports and additional representation but you can do that DIY if confident. If the defendant lawyers up and goes overboard on experts its their problem as they can only claim limited costs if you lose.
 
Fast Eddie said:
I also thought you were referring to a gearbox sprocket. I'm no solicitor, nor trader, but in my humble layman's opinion, the crank sprocket is an entirely different can of worms... For example...

Has the crank taper been ground incorrectly, altered, damaged? before you say "no" remember it is what, 50 years old, and has had how many previous owners?! Did you use a slightly incorrect key, too high, too sharp, too hard? Did you over tighten it? All these things would put stresses on the sprocket outside of its designed tolerance.

Plus, you say you aligned it with a rule and it was not bad, how bad is not bad? How bad does it have to be before it is too bad? Can you prove this?

My real point is this: if this goes to court, and the vendors insurance company uses its highly paid legal team, a team who specialise in NOTHING but trying to avoid or minimise payouts, they will have a field day opening this can of worms... at your expense.

Are you prepared to get into such a long, stressful, costly, legal battle?
Click to expand...

Sorry Eddie, but I disagree with most of your points. There isn't much difference between the jobs the two sprockets do. Also Peter has one or two old sprockets which worked without failing fitted to the same crank. The design tolerance of a sprocket is going to cope with gross misalignment (the chain would fail first) or overtightening.

Your scenario regarding legal proceedings is exactly what dodgy traders hope goes through the mind of anyone who is considering legal action. I'm also no legal expert but Peter needs to first get an independent report regarding the sprockets merchantable quality and whether it is fit for purpose. I imagine he is going to have to spend several hundred pounds, if not thousands, to rectify damage to the bike and engine alone. The cost of a technical report on the sprocket isn't going to add much to that bill win or lose. If the sprockets found to be defective then my next step would be https://www.gov.uk/make-court-claim-for ... g-to-court.

Back and forth, I sway with the wind
Resolution slips away again
Right through my fingers, back into my heart
Where it's out of reach and it's in the dark
Sometimes I think I'm blind
Or I may be just paralyzed
Because the plot thickens every day
And the pieces of my puzzle keep crumblin' away
But I know, there's a picture beneath
Indecision clouds my vision
No one listens...
Because I'm somewhere in between
My love and my agony
You see, I'm somewhere in between
My bike is falling to pieces
Somebody put it together

Faith No More (Falling to Pieces). It was on the radio as I was typing and it seemed very appropriate. I've added a couple of words.
 
he has been mentioned quite a number of times very recently on this forum as a very favorable and honest dealer
 
Al-otment said:
Fast Eddie said:
I also thought you were referring to a gearbox sprocket. I'm no solicitor, nor trader, but in my humble layman's opinion, the crank sprocket is an entirely different can of worms... For example...

Has the crank taper been ground incorrectly, altered, damaged? before you say "no" remember it is what, 50 years old, and has had how many previous owners?! Did you use a slightly incorrect key, too high, too sharp, too hard? Did you over tighten it? All these things would put stresses on the sprocket outside of its designed tolerance.

Plus, you say you aligned it with a rule and it was not bad, how bad is not bad? How bad does it have to be before it is too bad? Can you prove this?

My real point is this: if this goes to court, and the vendors insurance company uses its highly paid legal team, a team who specialise in NOTHING but trying to avoid or minimise payouts, they will have a field day opening this can of worms... at your expense.

Are you prepared to get into such a long, stressful, costly, legal battle?
Click to expand...

Sorry Eddie, but I disagree with most of your points. There isn't much difference between the jobs the two sprockets do. Also Peter has one or two old sprockets which worked without failing fitted to the same crank. The design tolerance of a sprocket is going to cope with gross misalignment (the chain would fail first) or overtightening.

Your scenario regarding legal proceedings is exactly what dodgy traders hope goes through the mind of anyone who is considering legal action. I'm also no legal expert but Peter needs to first get an independent report regarding the sprockets merchantable quality and whether it is fit for purpose. I imagine he is going to have to spend several hundred pounds, if not thousands, to rectify damage to the bike and engine alone. The cost of a technical report on the sprocket isn't going to add much to that bill win or lose. If the sprockets found to be defective then my next step would be https://www.gov.uk/make-court-claim-for ... g-to-court.

Back and forth, I sway with the wind
Resolution slips away again
Right through my fingers, back into my heart
Where it's out of reach and it's in the dark
Sometimes I think I'm blind
Or I may be just paralyzed
Because the plot thickens every day
And the pieces of my puzzle keep crumblin' away
But I know, there's a picture beneath
Indecision clouds my vision
No one listens...
Because I'm somewhere in between
My love and my agony
You see, I'm somewhere in between
My bike is falling to pieces
Somebody put it together

Faith No More (Falling to Pieces). It was on the radio as I was typing and it seemed very appropriate. I've added a couple of words.
Click to expand...

The main difference, to my mind, is not in its function, but is in how it is mounted, ie on a taper, rather than a spline. Therefore, the actual taper 'fit' plus any incorrect interference, high points, foreign bodies, etc and the amount of torque applied when tightening, will impact on how the stresses act on the sprocket.
When all such points are argued (by a pro) in court, it could well make proving any one thing as the cause, very difficult.
And I'm not saying he shouldn't argue the point and try and get some support from the trader BTW, and I fully agree on the comment about getting the sprocket properly analysed etc to build up the strongest possible argument.
I just wanted to provide some balance to the debate, going to court is not an automatic win!
Das ist alas!
 
If the little square section circlip fitted to the gearbox mainshaft can withstand being tightened to 70lbft an engine sprocket of much larger section will, even on a taper and with foreign bodies included should withstand considerably more than that. If an independent report states it failed due to unsuitable hardening or material then any argument stating it failed due to incorrect fitment is irrelevant. I never stated going to court is an automatic win - just that people should have confidence in the legal system, especially when they know they are not at fault. In a small claims court there is only one judge, they are not stupid people and are able to make a reasoned decision on the evidence put forward - they recognise bullshit.
 
madass140 said:
he has been mentioned quite a number of times very recently on this forum as a very favorable and honest dealer
Click to expand...

You not speaking from personal experience then.
 
I have bought goods from this supplier for as far back as I can remember 20 or 30 years with no bad experience.
Just because you personally had one gripe with them doesnt mean they are not of good standing, bad news travels fast and I've not heard to much bad about this company over the years
 
Well there you have it Peter, quite a bit of advice, seemingly covering most of the spectrum.

Whatever you do, the consensus seems clear that you should get the offending sprocket properly tested before doing much else.

IF it is proven to be faulty AND the fault is believed to be the cause of your failure, then you may well wish to speak to the supplier again. I would assume he'd be prepared to enter into dialogue then at least.

If he still isn't interested, and you feel confident that your case and evidence is sound and you've prepared yourself for the inevitable counter offensive from the defence, then you're as ready as you're gonna be I guess.

Whatever you decide to do, please do keep us all posted, we're involved now!

For what it's worth, I too have used this supplier a lot on my recent build and I've found them to be very good indeed. I've also found that the owner is very knowledgable and very generous with advice etc. so, to be honest, I'm surprised you've not had a more positive dialogue with him thus far.
 
madass140 said:
I have bought goods from this supplier for as far back as I can remember 20 or 30 years with no bad experience.
Just because you personally had one gripe with them doesnt mean they are not of good standing, bad news travels fast and I've not heard to much bad about this company over the years
Click to expand...

Why do you assume I've had 'just one gripe' with them? Never mentioned anything about gripes. They've been ok with me as in all the stuff I've sent back they've refunded, but I noticed the faults before they got used, no mention of postage refund though. The returned parts being 1) fork stanchions - pitted 2) close ratio gear cluster - sliding gears wouldn't slide (was advised to grind them with an abrasive stone?) 3) Mk3 chrome chainguard with no hole for extension piece - was advised to drill chrome chainguard. 4) Rear brake adaptor plate for lockheed caliper which positioned the caliper too high, not central or square to the disc. 5) Steering head bearings, manufacturer unknown. 6) Mushroom headed tappet adjusters one of which broke whilst tightening after adjusting tappets - still got those, lucky they didn't break in use and obviously were removed from the bike. I also removed an RGM floating disc when it started to float radially as well as axially after approx 35,000 miles, disc surface still had plenty of use in it but the method of retaining disc to the carrier is well dodgy. The disc side slider required 'relieving' too otherwise the bobbins would make contact as the wheel rotated.

So I think you should be able to understand my choice not to purchase from them anymore, of which I've done very little anyhow over the last 6 years, especially after the latest news. Or have I been unlucky?
 
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