wheel building

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nigelnightmare
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wheel building

Postby nigelnightmare » 10 Mar 2019, 11:47pm

Why does the spoke's last crossing go under when lacing?

I.E.Three cross = over/over/under or outside/outside/inside.

drossall
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Location: North Hertfordshire

Re: wheel building

Postby drossall » 10 Mar 2019, 11:51pm

The spokes then bear on each other and support each other. In effect you have a reduced length of spoke to flex.

Brucey
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Re: wheel building

Postby Brucey » 11 Mar 2019, 12:27am

there are several reasons including

1) the spokes are less likely to resonate and make a noise as you ride
2) under some loading conditions (eg high torque) one spoke of each crossing pair can be going slack; when braced thusly the spokes are less likely to go completely slack and therefore it is less likely for the nipples to back out
3) it improves the angle of the spokes where they enter the flanges slightly (esp if the spokes are a slightly baggy fit in the flange drillings)
4) If a spoke goes completely slack and indeed sees a compressive force, it is more likely to buckle in a consistent fashion and therefore may be less likely to break

However it is possible to build perfectly acceptable wheels without bracing the crossings in many cases and indeed it is slightly faster and slightly easier to build a wheel unbraced.

cheers
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~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~

nigelnightmare
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Re: wheel building

Postby nigelnightmare » 11 Mar 2019, 1:00am

Thanks Brucey.
I've been building wheels for quite some time now and had never been able to find out why.
Most books just say "That's the (correct) way they're laced" without explaining the reason behind it.

tatanab
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Re: wheel building

Postby tatanab » 11 Mar 2019, 6:48am

Brucey wrote:However it is possible to build perfectly acceptable wheels without bracing the crossings in many cases and indeed it is slightly faster and slightly easier to build a wheel unbraced.
and is sometimes necessary when building a small diameter wheel or with larger diameter spokes, like 13 gauge or even 12 gauge.

Brucey
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Re: wheel building

Postby Brucey » 11 Mar 2019, 7:22am

If you get hold of a Raleigh from the 1950s, it is odds-on that the wheels will be built with the crossings unbraced. Their wheels often used 14G spokes in the rear and 15G in the front. To this day if you buy a Gazelle, the wheels are similarly likely to be built unbraced. Typically they use 14G front and 13G rear spoking. You can build those rear wheels with braced crossings, but they don't. Brompton and Moulton wheels are usually built unbraced.

cheers
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~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~

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531colin
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Re: wheel building

Postby 531colin » 11 Mar 2019, 8:30am

Tucking the last crossing under also gives you maybe a millimetre more clearance to the Rear mech. in bottom gear, and it all counts.

Samuel D
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Re: wheel building

Postby Samuel D » 11 Mar 2019, 9:28am

nigelnightmare wrote:Most books just say "That's the (correct) way they're laced" without explaining the reason behind it.

Get yourself a copy of The Bicycle Wheel by Jobst Brandt.

Brucey
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Re: wheel building

Postby Brucey » 11 Mar 2019, 1:28pm

531colin wrote:Tucking the last crossing under also gives you maybe a millimetre more clearance to the Rear mech. in bottom gear, and it all counts.


Yes indeed; I have even seen wheels where just one spoke has been replaced, without bracing the crossing, and that spoke has touched the RD. However there is a conflict here; some folk reckon that if you make the 'inside' spokes the 'pulling' (trailing) spokes on the DS flange then under high torque the braced crossing is likely to be pulled away from the RD. However the conventional way to lace a rear wheel -for strength- is to make the outside spokes the DS 'pulling' spokes. [For example that is how shimano recommend that you lace a rear wheel up.] In this case high torque may pull the braced crossings towards the RD. This is either a disaster in the making or an early warning of such disaster, depending on how you look at it; what think ye?

This (outside pulling) is how I have always built rear wheels, but there really is stuff-all clearance between the RD and the spokes with some modern systems; this has lead to a rash of RD-meets-rear-wheel incidents. Every spring cyclists bring their bikes out of the shed and ride them, but because they are not very fit yet, they are more likely to use bottom gear than normal. The result is that the RD stands an above average chance of going into the back wheel unless the adjustment has been checked recently; in one LBS near me there have been about five bikes with this kind of damage in the last week or ten days. The RDs in question have not shown any scars on the outside in most cases, leading one to suppose that the RD wasn't pushed inwards through the bike falling over beforehand.

cheers
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~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~

nigelnightmare
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Re: wheel building

Postby nigelnightmare » 13 Mar 2019, 11:09pm

Samuel D wrote:
nigelnightmare wrote:Most books just say "That's the (correct) way they're laced" without explaining the reason behind it.

Get yourself a copy of The Bicycle Wheel by Jobst Brandt.


I've already got it thanks.
*edit.*
Had it since 1993 (10th printing) second edition hard back.

Samuel D
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Location: Paris

Re: wheel building

Postby Samuel D » 14 Mar 2019, 7:10am

nigelnightmare wrote:
Samuel D wrote:
nigelnightmare wrote:Most books just say "That's the (correct) way they're laced" without explaining the reason behind it.

Get yourself a copy of The Bicycle Wheel by Jobst Brandt.


I've already got it thanks.
*edit.*
Had it since 1993 (10th printing) second edition hard back.

Page 68 in my 3rd edition has a section called Interlaced spokes. The next section, Identical and mirror image spoking, discusses the effects of interlacing too.

nigelnightmare
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Joined: 19 Sep 2016, 10:33pm

Re: wheel building

Postby nigelnightmare » 15 Mar 2019, 2:36am

Page 72 in mine.
It's funny I must have read that book a hundred times and this is the first time I recall seeing that bit. :oops:

Mind you I was more interested in Part 2 "Building and Repairing Wheels".

nigelnightmare
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Re: wheel building

Postby nigelnightmare » 15 Mar 2019, 2:51am

tatanab wrote:and is sometimes necessary when building a small diameter wheel or with larger diameter spokes, like 13 gauge or even 12 gauge.


Why?
Is it because you end up bending the spokes when interlacing them on 20" wheels as opposed to bowing them on 26" or 700c?

Brucey
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Re: wheel building

Postby Brucey » 15 Mar 2019, 3:34am

more or less, yes. It is a lot of work to brace the crossings in some wheels, plenty of spoke straightening afterwards! Mind you, if the spokes are short enough, it is incredibly difficult to build the wheel at all (braced or unbraced) without bending the spokes a bit.

IMHO Brandt's book is still the best wheelbuilding book without doubt. However I don't 100% agree with everything he says and some aspects would benefit from further comment and elaboration. I am sure that he had plenty more to say on a lot of the points that are addressed briefly in the book, but that had he included such, the end result might have been less manageable overall. However that is not to say that there isn't value in further comment and discussion; one of my mad ideas is that a set of companion notes could be produced which would serve to provide further comment where appropriate.

BTW folk often criticise Brandt's book, claiming that it is 'complicated' and 'it doesn't really tell you how to build wheels'. This sort of talk is symptomatic of someone who hasn't made it as far as section 2. If all you want to do is 'build wheels by rote' then section 2 is all you need. The rest of the book allows you to understand why wheels are built in certain ways and therefore to make better decisions about what kind of wheels to build.

cheers
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~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~