Author Topic: Norton Crank Repair, (or how to stop a grown man crying)  (Read 10565 times)

Offline Ned Ludd

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Norton Crank Repair, (or how to stop a grown man crying)
« on: January 06, 2011, 06:12:17 PM »
Hi Guys,
After being a member of this forum for some time, I thought it was time I put something up myself, instead of commenting on others efforts.

Have you guys noticed that once it is known you have a workshop and some idea of how to use it, that people find "little jobs" for you to do for them. I don't mind when they do this as it often gives me chance to do things a little out of the ordinary. To cut a long story short, a mate of mine rang up to ask if I would look at a crank from a Manx Norton that belonged to a mate of his. Although my mate has a workshop of his own he did not feel able to fix the problem, hence the call. As with all such calls I said I would have a look but would not commit myself till I knew what the problem might be. So the story moves to the Norton owners house a few days later, and all was revealed. The problem was the end of the crankshaft had been beaten severely about its end with a club hammer. For those interested in why, well, the owner had fitted new main bearings and to over come slight wear on the shaft he had used Loctite, as recommended by the bearing suppliers. Only trouble they had recommended the wrong grade and supplied a permanent one, not a bearing fit one, now this would not have been too much of a problem had he put the cases back together quickly enough but he didn't. The outcome was that the cases would not close fully because the bearings were not where they should be and the Loctite had set. Said owner was almost in tears when he was explaining all this, how he had tried to get the crank out with a hammer and how the previous owner of the bike would be spinning in his grave at the way he was treating his old treasured classic.

Photo ! shows what a Manx crankshaft looks like.

Photo 2 shows what the damage looks like (not good). After sympathizing for a while, I could see a pathetic pleading look in face, so I said I would fix it for him and with luck he would not be able to see the damage.

Photo 3 shows the crank set up in the lathe. The timing side was held in a collet chuck and the drive side was first set in a centre, and the crank was checked to see if it was still true, which unbelievably it was despite the damage. I then set the fixed steady up to hold the crank while the repair was done. You can't see it in the photo but the con-rod is attached to the ceiling by two bungee cords, so it would not flap about while the lathe was turning.

That's all for now as the pixel limit is running out, and as "they" say always leave them wanting more.
Ned






I know enough to do what I do, but the more I know the more I can do!

Leafy suburbs of NW London

Offline John Stevenson

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Re: Norton Crank Repair, (or how to stop a grown man crying)
« Reply #1 on: January 06, 2011, 06:25:18 PM »
Ned, I have a set of two piece split dies for doing just this, you open the dies out fit over the damaged thread and tighten down and wind off, they are reverse cutting, do this a few times tightening down a bit at a time and you reclaim the thread 9 times out of 10.

John S.
John Stevenson

Offline Ned Ludd

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Re: Norton Crank Repair, (or how to stop a grown man crying)
« Reply #2 on: January 06, 2011, 07:00:08 PM »
Hi John,
Back in the old days I had a set of thread repair rollers that would also have worked but that was then.

To continue;
Photo 4 shows the end of the crank after turning to size and the signs of hammer damage cleaned away. I know that some would view the turning away of the belling to be "not best practice" but the end justifies the means. I had thought to swage the belling back where it should be but the thought of causing more harm than good might be done stopped me trying.

Photo 5 shows a threading tool aligned with the good part of the thread. The thread is 20tpi but my lathe is metric the nearest pitch to 20 is 1.25mm (actually the pitch is 1.27mm) and as I was only planing to cut a few threads I did not feel too concerned and I had a "cunning plan" to correct any errors.
The way to set up the thread is to start the machine, but with the tool clear of the work, and run the tool till you get to the good part then stop the lathe. I was not using the set over top slide method so all I had to do was to move the top slide till the tool could be put into the thread. From now on the half nuts would have to stay engaged, but his is no problem as my lathe reverses with ease. I am sure most of you know how to thread cut so all I will say is I cut the thread in the usual way but stopped before going to full depth.

Photo 6 shows the thread cut, doesn't look too bad but the nut didn't quite fit smoothly, so bring the cunning plan into action.
More to follow in the final thrilling instalment.
Ned

I know enough to do what I do, but the more I know the more I can do!

Leafy suburbs of NW London

Offline Bernd

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Re: Norton Crank Repair, (or how to stop a grown man crying)
« Reply #3 on: January 06, 2011, 07:29:37 PM »
Nedd,

Do you have any way of making your pics smaller, like 600 X 800. That's one of the reasons you ran out of space.

Bernd
You can't fix "STUPID".

Offline Ned Ludd

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Re: Norton Crank Repair, (or how to stop a grown man crying)
« Reply #4 on: January 06, 2011, 07:36:36 PM »
Photo 7 I did not cut the thread to full depth because I had it in mind to use a thread chaser to take off  the final shavings to give the final size and the correct thread profile. A few passes with the chaser and the result is Photo 8, the caption says it all. The English expression "sweet as a nut" seems apt.

So back it went to the owner who was pathetically grateful, and when he asked how much I said I did it for the fun of salvaging a piece of motorcycling heritage. This he did not accept, so I had to think of a price, which I did and he paid me three times the figure I suggested. I guess he was still feeling guilty of causing the damage! I got a phone call a few weeks later to say that the bike was back together and running better than ever, and to say thanks again. Sometimes a "thank you" is reward enough, but it is still nice to get petrol tokens, too.
I hope I have not bored you with this little tale of woe.
Ned
I know enough to do what I do, but the more I know the more I can do!

Leafy suburbs of NW London

Offline Ned Ludd

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Re: Norton Crank Repair, (or how to stop a grown man crying)
« Reply #5 on: January 06, 2011, 07:42:19 PM »
Hi Bernd,
I would love to but unfortunately Photoshop would not let me in, so I had to edit the photos in Microsoft's rather limited editing program. You should have seen them before I cropped them. All this digital stuff is a bit beyond me, but I will try harder next time.
Ned
I know enough to do what I do, but the more I know the more I can do!

Leafy suburbs of NW London

Offline Bernd

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Re: Norton Crank Repair, (or how to stop a grown man crying)
« Reply #6 on: January 06, 2011, 07:49:43 PM »
Ned,

Sounds good. Usally a program comes with the camera to allow you to modify the pictures. Just wondering.

Have you read Ralph's writeup on posting pics?

Just trying to help out here.

Bernd
You can't fix "STUPID".

Offline Ned Ludd

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Re: Norton Crank Repair, (or how to stop a grown man crying)
« Reply #7 on: January 06, 2011, 08:07:35 PM »
Hi Bernd,
Much appreciated but camera borrowed from my Son who borrowed it from his inamorata, so heaven knows where the original instructions are. I used to be able to work Photoshop 5, but as I said its having a bit of a tantrum.
Perhaps I should have used my mobile phone, instead of the Canon, I seem to recall the picture size is nearer to what is required for this site.
Ned
I know enough to do what I do, but the more I know the more I can do!

Leafy suburbs of NW London

Offline cidrontmg

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Re: Norton Crank Repair, (or how to stop a grown man crying)
« Reply #8 on: January 06, 2011, 09:36:08 PM »
That was an excellent repair you did, no wonder the owner was overjoyed.
As to making smaller photos, one very simple way is to use IrfanView. It's free, and shows just about any image format there is.
To adjust the image size, you go to menu item Image, Resize/Resample. There's lots of options how to do it, either giving some standard dimension, setting the new size in pixels, or as a percentage of the original. And then you can save the resized image as a new image, or overwrite the original. IrfanView also lets you crop the image (cut the interesting part of it), and save it as another image. And many other simple image manipulations. It's certainly not Photoshop, but for my purposes, it works actually better than PS. Small (1.44 Mb, instead of 1.2 Gb for Adobe PS...), quick, free and easy to use.  http://www.irfanview.com/index.htm
 :wave:
Olli
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Offline Stilldrillin

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Re: Norton Crank Repair, (or how to stop a grown man crying)
« Reply #9 on: January 07, 2011, 02:26:34 AM »
Ned.
Never mind quibbles about picture size. (I only ever look at the thumbnails).  ::)

That is a really great restoration, of some gorilla's butchery!  :clap: :thumbup:

David D
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Still modifying bits of metal... Occasionally, making an improvement!

Offline Bogstandard

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Re: Norton Crank Repair, (or how to stop a grown man crying)
« Reply #10 on: January 07, 2011, 04:03:11 AM »
I get jobs like that Ned.

http://madmodder.net/index.php?topic=1717.0

But in the end, he was crying.


Bogs
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MrFluffy

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Re: Norton Crank Repair, (or how to stop a grown man crying)
« Reply #11 on: January 07, 2011, 05:05:24 AM »
How much better the world would be if everyone knew that heating up the mating part to a dull red and then allowing the part to cool kills the loctite bond so things can just be turned or undone normally. Loctite should write on the back "Bond can be broken with heat cycling" or something similar. Of course it may have killed the bearings if they were 2rs spec, but better that than the crank thread. But Im preaching to the knowledgeable here already.
 
Nice save on the crank nut. Sometimes its nice to fix something nice just for the experience, and manx's are very nice indeed.

Offline Ned Ludd

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Re: Norton Crank Repair, (or how to stop a grown man crying)
« Reply #12 on: January 07, 2011, 01:19:49 PM »
Hi Guys,
Thanks for suggestions I will look into it.

I think I will come to the defence of the hammer merchant, well partly at least. He did use heat in the end, he put the crankcase in his kitchen oven for a few hours, but the reason he did not try it in the first place was because he was worried about setting alight to the cases. Some of you my know that pre-war Manx cases are not made from Aluminium but from Magnesium, and he thought they might immolate. Using a gas torch would not have worked either as the bearings are held the cases by plates held with 4 screws. So the oven and a long heat soak was the only way to get enough heat to the shaft where it met the bearing without risking over heating it. I would judge that he is, under normal circumstances, a fairly competent spanner monkey but everybody has an off day and his was a "peach". As someone, perhaps it was Bogs or someone replying to one of his posts, "if it can be repaired it wasn't broken in the first place". Let that be a guide to you all in your life of machining.

This is a special reply to Bogs, I have read your Bantam repair write up several times since you first posted it, I really do like your style, we think very much alike on such matters, but I bow to your greater experience. You and I seem to think that knowledge should be passed on to beginners and you use working examples in an exemplary way to highlight techniques, as opposed to the majority of books which leave quite a lot to be desired in these matters. I only posted the repair, following your lead, to the crank to show that all is not lost when such things happen.
Ned
I know enough to do what I do, but the more I know the more I can do!

Leafy suburbs of NW London

Offline Bogstandard

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Re: Norton Crank Repair, (or how to stop a grown man crying)
« Reply #13 on: January 07, 2011, 02:58:30 PM »
Ned,

Too much is given up for dead nowadays, when all it takes is a bit of thinking about and knowledge, and most mechanical things can be rescued.

I don't even try with wiggly amps and electric string, unless it is a screwdriver job.


Bogs
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Offline croz

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Re: Norton Crank Repair, (or how to stop a grown man crying)
« Reply #14 on: February 20, 2011, 02:35:05 PM »
Hi,
I am a "newbie" here!
Just to say nice work on the manx crank and that a couple of years ago i had to do similar to a couple of T140 Bonnie cranks, one was hammered not only on the drive side like the manx, but also the timing side ground oil feed nose too!!
Nice forum BTW
Croz

Offline Ned Ludd

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Re: Norton Crank Repair, (or how to stop a grown man crying)
« Reply #15 on: February 20, 2011, 03:05:22 PM »
Why thank you kind Sir.

The "newbie" tag can be a little misleading, can't it.
Ned
I know enough to do what I do, but the more I know the more I can do!

Leafy suburbs of NW London

Offline HS93

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Re: Norton Crank Repair, (or how to stop a grown man crying)
« Reply #16 on: February 21, 2011, 03:22:49 AM »
this is a great small FREE program to make pictures any size you want a lot of people use it on model boat Forums, works with all windows platformsand it does batches as well very easy to use.


http://bluefive.pair.com/pixresizer.htm


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