Date: 28-03-24  Time: 09:37 am

Author Topic: output shaft viable repair ???  (Read 2719 times)

Disorderlypunk

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output shaft viable repair ???
« on: 21 June 2017, 10:06:57 am »
could do with an engineer to double check this out and let everyone know before this is tried was just an idea and i know there are some amazing lathe machinists out there
i keep reading about output shafts being stripped and i cringe when i hear the sprockets have been welded on (yeah it works but)
i will be stripping my engine down before long and i know my output shaft has seen better days so was wondering if it was viable to sleeve the threaded shaft after turning it down and having that re threaded
obviously there is litle rotational stress in that area so i thought by making the sleeve a little bit smaller and using heat and compresssion to get as much friction between the two and even welding through holes to add more joint strength just incase
then turning it down and re threading again
-what do you guys think cause there are only so many of these used output shafts around.
shaft repair?
shaft repair?
« Last Edit: 21 June 2017, 10:12:50 am by Disorderlypunk »

Disorderlypunk

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Re: output shaft viable repair ???
« Reply #1 on: 21 June 2017, 10:09:30 am »
please excuse the crap drawing
its been over ten years since i have done engineers drawings other than for a small spacer
not to mention i was laying in bed using a cd case as a ruler

BBROWN1664

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Re: output shaft viable repair ???
« Reply #2 on: 21 June 2017, 10:32:04 am »
No reason it wouldnt work. To achieve it though you would need to remove the shaft from the gearbox so may as well get a new one in there.
An alternative would be to just cut a new thread the next size down and save the agro of putting the sleve on there.
Another ex-Fazer rider that is a foccer again

Disorderlypunk

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Re: output shaft viable repair ???
« Reply #3 on: 21 June 2017, 10:43:13 am »
true but putting a new one in there how much would a brand spanking new gearbox shaft cost
if its second hand then it could still have the same problem
going down a size is viable but for the size of the nut and its importance i would rather keep that part oem
not to mention its a recessed nut so prob quite hard to get hold of
yes the engine needs stripped but im doing it anyhow during the frame redesign.

BBROWN1664

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Re: output shaft viable repair ???
« Reply #4 on: 21 June 2017, 11:44:34 am »
You can get big enough nuts from loads of places and a decent engineer with a lathe, turning down the shaft, could easily recess the nut too.
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slappy

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Re: output shaft viable repair ???
« Reply #5 on: 21 June 2017, 11:57:30 am »
How good a welder are you? Or do you know a good welder?
Reason I ask is forget the sleeve and do this:


Turn end of shaft to remove all existing old thread and then further machine it about 4mm in diameter smaller.
Build the shaft back up with weld to above the original thread outside diameter, done properly the weld will fuse into the existing metal.
Then turn the shaft to the correct outside diameter for the thread then recut a new thread. Then the correct nut will fit no problem.
I have cut threads at work using this method as it is a lot cheaper then having to buy new machine parts and it works!   

Fazerider

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Re: output shaft viable repair ???
« Reply #6 on: 21 June 2017, 12:02:28 pm »

It seems overly complicated to me, but I guess it’d work.
Rather than weld through holes in the sleeve, why not just weld around the end? Better yet, as already suggested, forget the sleeve and build the shaft back up with weld.
If I was going to the trouble of rethreading the shaft I’d choose a more sensible pitch, the Yamaha one is simply too fine for the torque required. If you have a lathe available then cutting a suitable recess into the nut wouldn’t be much trouble.

unfazed

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Re: output shaft viable repair ???
« Reply #7 on: 21 June 2017, 12:12:26 pm »

I cut a slot in the shaft for a circlip and drilled a hole and tapped it to take a 6 mm bolt at the end of the shaft to keep everything in place. Soft of belt and braces job. It has been like that for over 16000 miles. See the downloads section o n it


Disorderlypunk

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Re: output shaft viable repair ???
« Reply #8 on: 21 June 2017, 03:17:22 pm »
this was just a theoretical exercise not just for fazers but for other rare as hens teeth engines aswell
the build up weld option is definatly a considerable option aswell
once again i say theoretical as it would allow for engines to remain at completly stock dimensions /thread diameters etc
thanks for everyones input its always worth seeing other peoples alternatives

unfazed

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Re: output shaft viable repair ???
« Reply #9 on: 21 June 2017, 04:41:57 pm »
Not theoritical al all, common enough method of reprofileing cams and cranks that are no longer available in the vintage world..
It would require reharding, it is something that may have to be done on the old African Twins when shafts become difficult to source as they were stripping the locating teeth on the output shaft for the front sprocket.
A new shaft for the fazer is about £80 new and reprofiling would probably cost more that. When the shafts become unavailable then it may be worth doing.



Disorderlypunk

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Re: output shaft viable repair ???
« Reply #10 on: 21 June 2017, 05:56:28 pm »
thats the main thing 'once unavailable'
there are loads of engines out there that parts are hens teeth so it was more a wider usage
there could be someone reading this with and old francis barnet motor or something and i just gave them the way to fix what cant be bought
im going to be getting loads machined up and down during the streetfighter build so one more piece wont break the bank

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Re: output shaft viable repair ???
« Reply #11 on: 21 June 2017, 07:13:17 pm »
cut back weld  to standard size recut  thread that the proper way to  recondition parts that are no longer made your idea is ok but you are relying on 4 points of weld to hold a thin sleeve on that  you are going to cut threads into in my mind thats not going to be very strong as you are relying on the thickness of the sleeve to hold the nut , dont think it would take much to snap it off

Disorderlypunk

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Re: output shaft viable repair ???
« Reply #12 on: 21 June 2017, 09:27:02 pm »
yeah the welding way is definatly better - it was just something that went through my head so i like to see others opinions
i think the threads would be the point of failure not the weld through holes as it doesnt take a huge amount of force on there
(its not a huge rotational force like on the sprocket splines)
but the weld and remove way is definatly better

Bretty

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Re: output shaft viable repair ???
« Reply #13 on: 25 June 2017, 10:45:59 am »
Well if you're removing the shaft to get it machined you have loads of engineering options. Although in that instance I would (did) just put in a new one (from a knackered £80 donor engine).





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Disorderlypunk

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Re: output shaft viable repair ???
« Reply #14 on: 26 June 2017, 12:16:10 pm »
i have some engines that come through my hands that are completly goosed so it is for more than just fazers but im on here everyday so i thought i would ask opinions
to give you an idea of how strange the engines get - i just finished rebuilding a fiat x1/9 gearbox using 3 knackered ones which was interesting as all from different years and were all slightly different (reason for rebuild was it wouldnt go into fifth because some dick fitted a four speed box)

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Re: output shaft viable repair ???
« Reply #15 on: 26 June 2017, 05:33:12 pm »
their must be more force than you recon to destroy the threads and nuts in the first place as its seems common or is it just that people are not fitting them correctly ?

Disorderlypunk

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Re: output shaft viable repair ???
« Reply #16 on: 26 June 2017, 08:07:19 pm »
badly fitted / too fine a thread / not enough threads on the original part number
a bit of all of the above

unfazed

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Re: output shaft viable repair ???
« Reply #17 on: 26 June 2017, 11:15:36 pm »
On the FZS600 the problem relates to the shaft being undersize, then add a nut with insufficient threads and a low torque setting, this leads to nut fretting and since the shaft is harder than the nut vibration wears the threads in the nuts.
This results in the nut falling off and if you are really unllucky the sprocket falls onto the threads and flattens the threads exacerbating the problem.
Some shafts were less than 17.5mm thick at the threads with is outside the tolerance level for an M18 fine thread shaft.

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Re: output shaft viable repair ???
« Reply #18 on: 28 June 2017, 08:55:21 pm »
Some gearbox sprockets are held in place by a circlip, as there is relatively little sideways load, that may be a viable option, just get an appropriate groove machined into the output shaft.

Paul

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Re: output shaft viable repair ???
« Reply #19 on: 05 July 2017, 08:24:03 am »
Personal view
 
The sprocket nut is there to stop the sprocket sliding off the output shaft.
 
It doesn’t need to tighten flush with the sprocket to do this.
 
The output shaft is the fault on some of the fazers.  The grooves in some output shafts are cut slightly too wide.
 
This allows the sprocket to move backwards and forwards on the shaft when placed under load or off load.
 
Because the nut is tight against the sprocket it continually rotates slightly on the threads… wearing them out.
 
The answer in my opinion is grind down the flange on the sprocket nut so that when it tightens on the shaft it is simply flush with the sprocket but does not tighten against it…. And put some grease on the sprocket to further ease the junction between the nut and sprocket. 
 
Therefore there is insufficient ‘grip’ between the sprocket and the nut so it doesn't turn the nut.
 
In essence you want to tighten the nut up on the output shaft but not tighten it up against the sprocket.
« Last Edit: 05 July 2017, 08:25:59 am by Paul »

tommyardin

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Re: output shaft viable repair ???
« Reply #20 on: 05 July 2017, 08:42:51 am »
Personal view
 
The sprocket nut is there to stop the sprocket sliding off the output shaft.
 
It doesn’t need to tighten flush with the sprocket to do this.
 
The output shaft is the fault on some of the fazers.  The grooves in some output shafts are cut slightly too wide.
 
This allows the sprocket to move backwards and forwards on the shaft when placed under load or off load.
 
Because the nut is tight against the sprocket it continually rotates slightly on the threads… wearing them out.
 
The answer in my opinion is grind down the flange on the sprocket nut so that when it tightens on the shaft it is simply flush with the sprocket but does not tighten against it…. And put some grease on the sprocket to further ease the junction between the nut and sprocket. 
 
Therefore there is insufficient ‘grip’ between the sprocket and the nut so it doesn't turn the nut.
 
In essence you want to tighten the nut up on the output shaft but not tighten it up against the sprocket.


Hi Paul, Just a quickie would that not allow the sprocket to chatter on the shaft causing to to the same shaft wear problems on the splines.

Paul

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Re: output shaft viable repair ???
« Reply #21 on: 05 July 2017, 11:12:01 am »
To Tommy


Yes......  but from memory some of the old Hondas used to have a slightly similar method of securing the sprocket and they didn't give problems


But more to the point if the output shaft has the over-size splines issue, the sprocket would chatter anyway even when the nut is tightened up on the sprocket......  which is why it wears the threads out.   But it doesn't seem to wear the output shaft splines out.   

Fazerider

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Re: output shaft viable repair ???
« Reply #22 on: 05 July 2017, 12:06:32 pm »

Personal view
 
The sprocket nut is there to stop the sprocket sliding off the output shaft.
 
It doesn’t need to tighten flush with the sprocket to do this.
 
The output shaft is the fault on some of the fazers.  The grooves in some output shafts are cut slightly too wide.
 
This allows the sprocket to move backwards and forwards on the shaft when placed under load or off load.


This doesn’t tally with my experience. New sprockets have always been a tight fit to the shaft, quite difficult to get on in fact. I’ve often double checked the new sprocket actually has the right number of splines before trying again.




Because the nut is tight against the sprocket it continually rotates slightly on the threads… wearing them out.
 
The answer in my opinion is grind down the flange on the sprocket nut so that when it tightens on the shaft it is simply flush with the sprocket but does not tighten against it…. And put some grease on the sprocket to further ease the junction between the nut and sprocket. 
 
Therefore there is insufficient ‘grip’ between the sprocket and the nut so it doesn't turn the nut.
 
In essence you want to tighten the nut up on the output shaft but not tighten it up against the sprocket.


The trouble with that is that the nut will then have fewer turns mated with the shaft… albeit not to the extent of being as bad as the original 9mm nut.


Secondly, I’ve had nuts come loose where they are still unable to rotate because the tab washer is still working… the nut has been forced across the thread rather than coming undone. I suspect that giving the sprocket a longer run-up by not clamping against it might result in a slide-hammer effect and even earlier failure of the nut.


Thirdly, as Tommy points out,the spines will get worn if the sprocket is free to wander left and right rather than being clamped firmly.