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#Post#: 647--------------------------------------------------
Oil feed to the crank...???
DIR By: Nitram
Date: April 10, 2015, 3:31 am
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I was reading the other day about the relatively simple
modification to improve oil feed to the big end (and being a
plain bearing, its probably a case of more-is-better) which
involves simply removing the bush that sits in the clutch cover
and that goes over the end of the crank, and replacing it with a
lipped seal. The bush, 'though in a blind hole, is pretty easy
to remove and is identical in size to the seal where the
gearshift shafe goes through the same cover: i.e. 24mmx14mm. So
its pretty simple to put the seal in, 'though I also planned to
put a thin steel retaining plate over it, screwed on with
countersunk screws etc, just to make sure it doesn't pop out
under oil pressure.
But it occurred to me to wonder the extent to which the bush is
designed to support the end of the crank, (which after all is
just outboad of the primary drive) rather than simply to
facilitate oil feed to the crank....... It'd be a shame to have
the crank snap some time when the clutch was dumped the mighty
NF's power was unleashed through an unsupported crank....... ;).
I guess lots of motorbike engines don't have any support for the
end of a crank , 'though some do. (I'm thinking here of Ducati
singles which from memory have the crank bush (and oil feed)
outboard of the OHC bevel drive gears- but my experience with
fourstrokes is minimal)
Has anyone come across this mod on a NF, and had the bike run
indefinitely afterwards without problems ? ???
Any thoughts on the subject ?
Cheers,
Nitram
#Post#: 649--------------------------------------------------
Re: Oil feed to the crank...???
DIR By: banquo
Date: April 10, 2015, 7:56 am
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Hi Nitram. Of course I don't have any experience of this, but
the function of the bush will be to support the outboard loads
on the crank (outboard of the main bearing that is), which in
this case effectively is the drive side. The primary drive will
attempt to bend the shaft, and its stiffness will be affected by
the fact it's now cantilevered instead of supported at both
ends.
That will result in about twice the bending stress if my memory
serves me right (and that's by no means guaranteed these days)
based on simply supported beams supported at one end
(cantilevered) compared with at both ends. Of course it's a lot
more complicated than that, as you have various different forces
applied at different parts of the shaft, but the principle
remains.
Needless to say, it wouldn't be recommended to modify anything
mechanical to the extent that stresses were increased, but if
the outboard crank is very over-engineered, with a factor of
safety far higher than needed, then it's perfectly possible for
it to work without any issues.
Only experience can answer that, and if there are many who have
performed the modification without problems, then that would
raise the comfort level.
I take it there's not enough depth to fit a shorter bush and a
seal, which might be the preferred solution?
#Post#: 651--------------------------------------------------
Re: Oil feed to the crank...???
DIR By: huub
Date: April 10, 2015, 11:23 am
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if he engine has done some miles , there will be enough play to
stop it from acting like a bearing.
and steel running in a alloy bush is a pretty bad bearing
combination anyway.
having said that , a oilseal should be held in place firmly to
stop it from popping under the 4 bar oil pressure available
with a extra metal plate to protect the oil seal, it is quite a
common modification
#Post#: 654--------------------------------------------------
Re: Oil feed to the crank...???
DIR By: Nitram
Date: April 10, 2015, 3:33 pm
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Thanks Banq and Huub.
The crank certainly is, like all things NF, very solid on the
drive side (i.e. probably over-engineered). And as Huub points
out, if there's wear in the original bush then it wasn't
contributing to supporting the crank anyway. Mine has about .5
mm wear (there must have been bugger-all oil pressure) so I'm
thinking........I'll give it a go. And the additional oil
pressure can only be a good thing for the big end.
Tony from UK says his is running fine with the mod, and if as
Huub says its a common mod then not too much
risk............hopefully.... ;)
Thanks again for your thoughts.
Nitram
#Post#: 655--------------------------------------------------
Re: Oil feed to the crank...???
DIR By: banquo
Date: April 11, 2015, 2:58 am
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No substitute for experience. It did occur to me that the wear
could have as much to do with run-out on the crank and
misalignment than anything else.
The crank won't be perfectly straight, and there will be at
least some run out when rotating, plus any whipping that may
occur. Also, how could they guarante that the bush in the clutch
cover aligns perfectly with the crank, when they are on separate
castings? Maybe I'm missing something.
Look forward to hearing how you get on with the conversion. Some
pix would be good too!
#Post#: 2199--------------------------------------------------
Re: Oil feed to the crank...???
DIR By: patentgeek
Date: October 22, 2017, 11:56 pm
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Reviving this thread as I'm in the process of replacing the
aluminum bushing in the right engine cover with a shaft seal.
To extract the aluminum bush, I used a tap (I think 9/16-20 was
closest) to thread the ID of the bushing. I then heated up the
engine cover around the bush with a MAP torch and threaded a
bolt through the threaded ID of the aluminum bush until the bolt
bottomed on the engine cover. Continuing to tighten the bolt
acted to extract the bushing.
I noticed the end of my crank (that will fit into the shaft
seal) is somewhat grooved, which isn't an ideal surface for a
shaft seal. Other than dressing down the surface, I'm not sure
what can be done about that. I'm sure the shaft seal will seal
better than the aluminum bush, and the modified Daytona oil pump
I'm installing should have almost double the pumping capacity of
the stock NF oil pump, so I'm not particularly concerned. It
might be possible to press a very thin sleeve onto the end of
the crank and use a larger ID shaft seal if the grooves are
problematic.
#Post#: 2201--------------------------------------------------
Re: Oil feed to the crank...???
DIR By: huub
Date: October 23, 2017, 2:22 am
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sounds like a perfect application for a speedi-sleeve.
#Post#: 2211--------------------------------------------------
Re: Oil feed to the crank...???
DIR By: Nitram
Date: October 30, 2017, 5:06 am
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In case anyone is considering this mod, I ended up putting the
crank in the lathe to tidy up the grooves and scoring, but
taking off the bare minimum to achieve a reasonable finish. The
seal, retained by a thin cover plate and some small allen screws
Loctited in has now been in place for about 6,000km without
problems. I don't have an oil pressure gague so I don't know how
much it helps but its got to be better than the sloppy bush that
was in there before.
Good luck !
Nitram. :)
#Post#: 2212--------------------------------------------------
Re: Oil feed to the crank...???
DIR By: banquo
Date: October 30, 2017, 7:37 am
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Sounds good Nitram; did you take any pix?
#Post#: 2218--------------------------------------------------
Re: Oil feed to the crank...???
DIR By: patentgeek
Date: November 24, 2017, 12:27 am
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Huub suggested an SKF Speedi-Sleeve to fit over the grooved end
of the shaft to provide better sealing. I believe SKF part
#99055 can be used for this application as the nominal shaft
diameter is 14mm. See the link below for technical
specifications:
HTML http://www.skf.com/us/products/seals/industrial-seals/power-transmission-seals/wear-seals-skf-speedi-sleeve/index.html?designation=99055
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