Spokes?

Wayne van Wijk wrote:

I need new spokes for my penny farthing. Any ideas on who makes long
spokes (about 500 to 600 mm long)?

I make long spokes from 36" x 3/32" stainless steel welding rods.

I make an S hook for the hub end, cut and thread the rim end with a 3-56
die.

This results in a 13 gauge stainless steel spoke of the desired length.

It requires a nipple made for a 13 gauge spoke with 56 threads per inch.
___
Here's a profile of a spoke showing the S hook ( |___ ):
___
|_________________________________________________ ___________________

Spokes up to about 900mm long can be made this way.

Sincerely,

Ken Fuchs

Shocking!

You really shouldn't cut threads onto a spoke - it's a terrible idea. It
leaves a considerably weaker thread which can cause problems when
tensioning.

1. Talk to a bike shop and see if their longest custom length is long
enough

2. Buy welding rod of high grade stainless, make a spoke "hook" on one
end.(best done with a proper tool - can be home-made)
then get the threads rolled by bike shop

3. Find out where the Penny cyclists get theirs

4. Buy some from www.theoldbicycle.co.uk and wait for shipping

5. Buy an expensive thread roller and do the lot yourself.

may be worth speaking to these guys?
http://canberrabicyclemuseum.info/forsale.htm


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I agree with Joe - spoke threads should be rolled, not cut. Cutting
removes material and weakens the spoke.


Tony


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JoeRowing wrote:

You really shouldn't cut threads onto a spoke - it's a terrible idea. It
leaves a considerably weaker thread which can cause problems when
tensioning.

Can you please provide references to support this thesis? I know you
are correct that cut threads are weaker than rolled, but I've seen
nothing to suggest that cut threads are not adequate for most spoke
applications.

The nipples are made out of brass which is clearly weaker than the steel
spoke.

I use thread cutting oil and hand thread the spokes.

I've never had any failures due to spoke threads or nipple threads.

2. Buy welding rod of high grade stainless, make a spoke "hook" on one
end.(best done with a proper tool - can be home-made)
then get the threads rolled by bike shop

The 3/32" stainless steel welding rod might be too thick to be rolled.
Cutting the threads might be the only option with this size stock.

Thanks for your input, Joe.

Sincerely,

Ken Fuchs

In article ,
Ken Fuchs wrote:
)TonyMelton wrote:
)
)I agree with Joe - spoke threads should be rolled, not cut. Cutting
)removes material and weakens the spoke.
)
)Please explain or provide references supporting this thesis?

Jobst Brandt mentions that spoke threads are rolled in The Bicycle Wheel.
-Tom

TonyMelton wrote:

I agree with Joe - spoke threads should be rolled, not cut. Cutting
removes material and weakens the spoke.

On Thu, 4 Sep 2003 23:13:57 -0500, Ken Fuchs wrote:

Please explain or provide references supporting this thesis?

Ian Smith wrote:

What thesis? That cutting a thread removes material? That rolling
doesn't? That the spoke is thus weakened?

The thesis that spoke threads should be rolled and not cut. For
example, if the stock is too thick to have rolled threads, but the
threads can be cut, what is wrong with cutting the threads? I agree in
general that thread rolling may be better than thread cutting, but isn't
it possible that thread cutting is adequate for many applications?

The other issue with cut threads is that the thread profile is
generally less good - it typically has sharper teeth (particularly at
the base of the teeth) which introduce higher stress concentrations,
and is likely to have at least one local defect which is at risk of
propagating fatigue cracking.

Are there similar problems with thread rolling? Or is the thread
rolling process like making wire, it comes out stronger than other
processes. (A steel cable made of wires is stronger than a steel rod of
the same diameter.)

As to references, I'd expect most good machine / mechanical design to
talk about this, though it's one of those things that's so commonly
known that it's difficult to find a reference.

Let me play devil's advocate: Perhaps the lack of references regarding
the thesis is due to the thesis being false and most people blindly
accepting it as obvious. Only kidding.

Whether this is relevant to performance of spokes is an altogether
different matter. Furthermore, as the spoke becomes longer, such
detailing becomes even less critical, because longer and hence more
elastic spokes distribute load more readily, resulting in lower peak
stresses in any one spoke. Thus, it could easily be the case that
it's an adequate method for long spokes, even if it's not the
theoretical optimum.

Thank you Ian, for the above justification for thread cutting being
adequate for at least long spokes.

I might also point out that my 56" big wheel has a total of 80 spokes,
about double what small wheels (20-29") typically use plus the spokes
are 13 gauge [.092"] (larger than the often used 14 gauge [.080"]
spoke). The load is distributed over more and stronger spokes. This
application of spokes with cut threads has worked out great as well as
the about a dozen big wheels I built using spokes with cut threads.
I've never had a spoke failure related to spoke threads or nipple
threads.

Sincerely,

Ken Fuchs

On Fri, 5 Sep 2003 16:21:37 -0500, Ken Fuchs wrote:
Ian Smith wrote:

The other issue with cut threads is that the thread profile is
generally less good - it typically has sharper teeth (particularly at
the base of the teeth) which introduce higher stress concentrations,
and is likely to have at least one local defect which is at risk of
propagating fatigue cracking.

Are there similar problems with thread rolling? Or is the thread
rolling process like making wire, it comes out stronger than other
processes. (A steel cable made of wires is stronger than a steel rod of
the same diameter.)

Rolled threads have slightly rounded teeth profile (or very rounded,
depending on teh size of the thread) and don't have the same sort of
defects. In addition, the rolling process could strengthen the
material in the same sort of way as drawing wire (but I don't offhand
know how significant teh effect would be), so you win all ways with
rolling the threads.

regards, Ian SMith
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