Re: rebuilding my wheel

[U-Turn]

I'd still go with what I put down at the end of that thread:

'here' (http://tinyurl.com/lnjt).


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[evilewan]

thanks u-turn,
unfortunatly i`m realy fussy for details when i`m embarking on something
new.
so i`ve got a few more questions....

what you said was:
>We at the Ordinary Bike Shop just built two of these. Profile >hub,
Alex DX32 19" rim, 4-cross. The rim ERD was 376, the >spoke length was
about 185mm, spokes were 14g of type DT >Swiss.

was that spoke length exactly 185mm?

i ve never bought spokes before so i don`t know if they come in 1mm
increments or .5mm or whatever.

and did you use DT nipples?, i hear that these are a bit smaller than
normal. and require the spokes to be 5mm longer.

i ned to know all the details so i can walk into francophone bike shop
and walk out with the spokes and nipples and be sure they are the right
size.

thanks

i realy need to know


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[U-Turn]

I didn't order those spokes but I'll talk tomorrow to the fellow who did
and get right back to you.


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[Adrian]

186mm, by my calculations... assuming I've managed to find the correct
dimensions :)

Spokes for mountain bikes tend to come in 2mm increments. Presumably for
smaller wheels you get smaller increments...

I don't think you need to alter the spoke length due to the nipples, and
certainly not by as much as 5mm. I think the spokes should extend the
same distance regardless, i.e. protrude just into the rim.

Adrian.


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[evilewan]

i found a guide to wheelbuilding here:
http://tinyurl.com/lw58
somebody else might find it usefull too. its from a bmx site.

also, does anybody know anything about this "interlace under the third"
thing that he talks about
apparently to make the wheel more resistant to grinds,
if this works shurley it would be a good plan for trials wheels too.


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[U-Turn]

I don't see how that would make the wheel grind-resistant. Grabs and
grinds abrade the spokes and catch crossings; this technique increases
the number of crossings.

That last photo is pretty unconvincing, as far as whether the wheel is
built well or not. There are large kinks in some of the spokes and
there has been no spoke line correction at the nipples. There are huge
curves in some spokes between crossings. Although he states that this
is a finished wheel, it looks like a wheel that has not been tensioned
yet. I think I'll stick to the standard texts.


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[Max_Dingemans]

Ok, so with a alex dx32 3x profile 36º wheel, I used 176's. that's DT
straight gauge. not problems at all, I however havent really gotten to
test it yet. Just incase you havent figured it out yet, or for future
reference.


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[Adrian]

How true does a unicycle wheel actually have to be? Assuming you're not
running brakes.

I'd've thought you could get away with quite a lot, assuming you can get
the general tension approximately right, for strength purposes.


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[U-Turn]

Well we don't have the info (sorry), but I have never found Roger's
spoke calculator to be wrong, giving 186mm for a 4-cross. I personally
wouldn't hesitate to order spokes based on that information. I ignore
the nipple length thing.

A unicycle wheel for a uni without brakes can get away with more radial
and lateral wobble than one with brakes. However, in general, wheel
strength is a function of:

1. wheel geometry
2. rim geometry and quality
3. spoke quality
4. average wheel tension
5. max spoke tension
6. min spoke tension

If one assumes that (1) is good, and that (2) and (3) are valid, then
the wheel strength depends on average wheel tension (4)primarily, and
max spoke tension (5) and min spoke tension (6) secondarily. (5) is
important because if (4) is high, then the spoke with the highest
tension is the one most likely to fail due to overstress. (6) is
important because if (4) is too low, then the spoke with the lowest
tension is going to fret most and fail (at the spoke head) soonest.

So not only is average tension important, but also keeping the max and
min as close to the average as possible. Since by assumption (2) we
have a "perfect" rim, basically excursions from average will show up as
wobble.

Although this is a simplification, it is a useful one. Basically it
says that with a good wheel design and good components, all the spokes
should be nearly the same tension when the wheel is true. Conversely,
if the wheel is not true, then the spokes have variations in tension
that weaken the wheel.

At the rim joint there will almost always be tension excursions that are
unavoidable.


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[leow]

166 2 cross
174 3 cross
183 4 cross

I'd go with 3 cross - 4 cross wont work unless you re-drill the rim
holes at an angle.

Leo White


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[leow]

leow wrote:
> *I'd go with 3 cross - 4 cross wont work unless you re-drill the rim
> holes at an angle.
> *


Quoting myself...

You can see what I mean about 4 cross not being a good idea on a small
rim.

http://www.unicyclist.com/gallery/albun41/P1010017

The nip*les emerge at 90 deg but the spokes bend away towards the hub.

This makes it a pain to tension and introduces a weak spot.

If you use a larger flange hub like a suzue I'd use 2 cross.

Leo White


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[U-Turn]

leow wrote:
> *http://www.unicyclist.com/gallery/albun41/P1010017
>
> The nip*les emerge at 90 deg but the spokes bend away towards the
> hub.
>
> This makes it a pain to tension and introduces a weak spot.
>
> If you use a larger flange hub like a suzue I'd use 2 cross.
>
> Leo White *
These are my pics and are placed in the gallery precisely for the
opposite reason -- to show that 4x on a trials uni is practical. There
is not any additional work or trouble to tension this wheel. It does
involve spoke path correction, but that's normal for any wheel (you do
spoke path correction, don't you?). There is nothing weak about it;
this wheel has done at least 3 foot drops and tons of stairs with no
problem whatsoever -- no loss of trueness or damage of any sort.

If you read the literature you will see that the angles between nipple
and spoke are common and straightforward.

Redrilling the spoke holes would accomplish nothing because the seating
for the nipple flange would not change.

2 cross in a trials wheel is not a good idea, however; the minimum I'd
use is 3 cross.


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[U-Turn]

evilewan -- The Monty rim is notorious for pulling through the rim. The
Alex is not.

leow -- That's cool that you figured out how to relace a giraffe wheel
without unwelding. I'm expecting to build my first here soon. The
advice I currently have is to build the wheel, then attach the sprocket
and weld. Do you think it would be possible to build the wheel after
welding?


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[Max_Dingemans]

do you really have to weld it to the hub? what we always did was weld
the cog to a freewheel, weld the freewheel in place, and then loc-tite
the frozen freewheel to the hub. we've never had one spin off after
loc-tite and the apropiate drying time. however I think we've had a
couple cog's welds break on the freewheel... but those are easier to
replace. and if that makes any sense.


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[TonyMelton]

I had the same trouble that Ewan had - spokes erupting through my Monty
rim. My solution was to rebuild the wheel with a Profile hub and Alex
DX32.
I just picked up my rebuilt trials unicycle wheel 1/2hr ago. The
spoke calcuator on unicycle.uk.com was right on the money for spoke
length (177.47mm predicted for 3-cross; 177mm actually used.)
The guy who rebuilt my wheel said that reason spokes were pulling
through the rim was likely to be because of pedal grabs putting extra
stress on the wheel. Has anyone else experienced the spoke nipples
pulling thru their Monty rim problem -without- doing pedal grabs? If so
then we know that it's a problem with the Monty rim itself, rather than
how the rider treats it.


Tony Melton


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[U-Turn]

> *likely to be because of pedal grabs putting extra stress on the
> wheel. *
It seems to me a little thought shows that this is incorrect. What is a
pedal grab?

+ A hop
+ an unloaded 90 degree rotation to get pedal in place
+ landing on platform with weight on pedal
+ side-to-side unloaded balance motions
+ unloaded 90 degree rotation to get foot on other pedal
+ pull on seat and hop up to rubber
+ landing on platform after ~ 1 foot unloaded hop
+ subsequent micro-hops for balance.

See, there is nothing here to stress the wheel any more than riding
along the sidewalk or the height of the initial hop.

It seems to me that the Monty design is flawed. They should have used
either eyelets or thicker material around the spoke holes. Since the
Monty tire is infamous for not fitting the Monty rim well, we could
surmise that the design process in general was not up to, say, the Alex
design process in terms of quality.


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[evilewan]

i do loads of grabs on my unicycle, not to mention grinds and drops
while hopping on the wheel.

i suspect that in general its unicycle trials which put extra stress on
the wheel.
although grabs dont put extra stress on the wheel, i suspect that the
wheel dosent particularly like the sideways impacts it gets when you
grab onto uneven obstacles, or screw up. i`ve got plenty of scratches on
the braking surface to atest to it.
even so, im sure that the main stresses that my wheel gets are:
1. big drops badly
2. drops hopping on the wheel, this means that you always land witht the
wheel at an angle like this /


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