Build a Dynamo 36-hole Front Wheel

Build a Dynamo 36-hole Front Wheel
Part I. Lacing the Wheel © 2012 by Frederick Su
I don’t bicycle at night, but I do bicycle through dark, rainy Northwest winter days. A front light would be a useful safety feature.
So, why not have a light where electricity is generated through my
own muscle power? Thus, the idea of building a front wheel with a
hub dynamo was born. I had never built a wheel before. Now, I
believe a front wheel build (easier than rear) is within the realm of
expertise of the average home bicycle mechanic. Afterwards, you
can say, “Wow! I built a wheel that generates electricity!”
I chose the SON28 2012 (www.longleafbicycles.com and
www.peterwhitecycles.com) since it is the best hub dynamo (Peter White has loads of information on dynamos and lights) and the Velocity Dyad because I wanted a touring rim.
Helpful references include The Bicycle Wheel, 3rd Edition, by Jobst Brandt,
http://sheldonbrown.com/wheelbuild.html, and http://sheldonbrown.com/rinard/spocalc.htm
for Damon Rinard’s spreadsheet for calculating correct spoke lengths.
This is a 36-spoke wheel, built in 4 sets of nine spokes each. The first 2 sets are radial and
inbound (defined later). The last 2 sets cross in a 3X pattern and are outbound. The spokes are
DT Swiss stainless steel straight spokes, 2.0 mm in diameter, and 286 mm in length (calculated
from Rinard’s spoke calculator.) Spoke length is critical and depends on effective rim diameter
and hub dimensions. Unsure about the length? Ask a bicycle mechanic. Get the length correct!
Caution! Wear safety glasses when building a wheel! Spokes have pierced eyeballs.
V
electrical
terminals
1. (Skip if you use presta.) Many rims, including the
Velocity Dyad, come with 6-mm diameter presta
valve holes. If you use Schrader tubes like I do, you
must ream this hole to 8 mm. (Harbor Freight sells
a cheap well-made reamer.) Use tape to mark the
8-mm diameter depth on the reamer so you don’t
over-enlarge the valve hole V. Smooth the edges of
the hole down with a small, fine round file.
2. This is the SON28 2012 hub dynamo manufactured by Schmidt Engineering in Germany. It costs
$285. It has the least drag of any dynamo out
there. It puts out ~3 watts, enough to power an
LED front headlight and LED rear light. You can also
hook up a charger, such as the E-WERK, to charge
batteries for your electronic devices while riding.
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3. You need a nipple driver to start the (usually) brass nipple onto the spoke threads. I suggest using an expanding
slot blade screwdriver where the bifurcated blade can be
expanded to fill the slot of the screw to hold it by friction.
If you drop the nipple into the “black hole” of space
between the top and bottom of the rim, you will have a
difficult time retrieving it. Remember, it can’t be picked up
by a magnet.
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V
R
electrical
terminals
4. First Set. Inserting the key spoke. Mark the valve hole by putting a piece of tape above it.
This is your reference mark, both as to where along the circumference of the rim you are and
also which side of the wheel you currently have up. 1, V, and R in the photo refer to the key
spoke, valve hole, and view of right side of the rim, respectively. Hold the hub in your hand
with one side of the rim on your lap and the other side on a table or chair. Drop 9 spokes into
every other hole in the top flange. (Be sure to grease the threads of the spoke before inserting
into the nipple.) Take one spoke (henceforth referred to as the key spoke) and connect it to a
nipple pushed through the first hole left of the valve hole. This left hole should be offset
upward toward the upper flange (see next step). Screw the spoke into the nipple so that about
1/2 of the threads are showing. (I start the nipple onto the spoke with the bifurcated screwdriver of step 3 and then switch over to a regular medium-size screwdriver for ease of turning.)
I chose to have the electrical connectors from the dynamo on the right side of the wheel. (It
really doesn’t matter, because when done, I could just flip the wheel and have the electrical
terminals on the left. The caveat is which way the tire treads run.)
2
R
key spoke hole
V
5. Most modern rims have an offset for the spoke holes so that the nipples are slanted
toward the correct flange in the hub. Note that the spoke hole to the left of the valve
hole V is offset upward and it is through this hole that the key spoke is threaded to the
nipple and hung to the upper flange of the hub per step 4. Brandt writes that if there
is no offset for the spoke holes in the rim, just use the first spoke hole to the left of
the valve hole. Do you see that the spoke holes alternate offset upward, then down,
then up, etc.? (Did you also observe that if you flipped the rim over and set it up per
above, the spoke hole to the left of the valve hole would still be offset upward?)
1
V
R
6. Remember to grease the threads of all subsequent spokes! And screw nipples until ~1/2
of spoke threads are showing.
Insert spokes into every fourth hole of the rim
(there are 3 empty holes between spokes)
and secure with nipples until all 9 spokes are
hung, as shown. The spokes of this first set are
referred to as “inbound” spokes because their
lengths lie along the inside of the hub flange.
1
L
7. Second Set. Flip the wheel over (left side
up) and insert one spoke through the left
flange of the hub as shown so that this spoke
is to the right of the key spoke 1. Note that
the holes in the left flange of the hub are offset from those on the right side. Thus, the
new spoke aligns ~1/2 way between the key
spoke and its adjacent open hole (to the right)
in the opposite flange.
3
V
8. Insert this first spoke (2) of the second set
into the hole adjacent and to the right of the
key spoke 1. (V and L in the photo refer to the
valve hole and view of left side of rim,
respectively.)
2
1
L
2
V1 2
L
L
9. Now drop 8 more spokes of this second set
into every other hole in the upper (left) flange
as shown, starting from the #2 spoke. Then
connect each spoke to a nipple through the
hole on the rim to the immediate right of the
spokes of the first set. On the rim, there
should be two spokes and two holes, repeating all the way around. All the spokes should
be radial with no crossing. There should be a
spoke in every other hole in both flanges.
Note that spokes of this second set are also
inbound spokes.
10. This is the photo after the second set of
spokes has been connected, showing the rim
from the left side and the alignment of V, 1,
and 2. Note that all the spokes are radial, with
no crossings. The spokes are uniformly loose,
threaded ~1/2 way down the greased spoke
threads, and are inbound.
4
L
11. The third set of spokes will be crossing
spokes and outbound (i.e., their lengths will lie
on the outside of the hub flange). With the left
side of the wheel still up, facing you, insert
spokes into the remaining holes of the bottom
(right) flange so they hang as shown.
12. Hold onto the hanging spokes firmly and
flip the wheel over as shown, so that the right
side is now up. Fan the spokes out so that
they lie flat (see below).
R
1
V
R
5
13. Now, the right side of
the rim is up and the 3rd set
of spokes fanned out. Grab a
spoke as shown (I chose a
spoke to the immediate
right of the key spoke) and
rotate the hub counterclockwise. That is, you are pulling
the spoke away from the
valve hole, V. You may also
use your other hand to help
twist the hub counterclockwise. If you have not
overtightened the spokes,
the hub should not be difficult to twist.
un
dt
outbound spoke of interest
hi r
ds
po
d fir
st sp
ou n
r in
ove
bo
ove
r i nb
sec
de
r in
nd
b ou
un
V
oke
sp
on d
oke
R
1
ke
14. With the hub rotated, start the crossing pattern thus for the first outbound spoke of interest (all referenced spokes are in the same flange): go left over the inbound first spoke, over the
inbound second spoke, and then under the inbound third spoke, and secure with nipple into
the first reachable empty hole in the rim. (You may have to bend the spoke of interest slightly
to get it under the third spoke.) Do this 3X crossing pattern for the remaining 8 spokes of this
set and secure with nipples. (Notice that the first spoke crossed here was the key spoke.) You
should not have problems screwing the nipples onto the spokes if your spoke calculations
were correct!
1V
15. The wheel, right side showing, with 3
sets of spokes connected.
R
6
inserting
spoke
R
L
1
V
16. The fourth set. With the right side of the
wheel up, start inserting the last set of spokes
into remaining holes of the lower flange, as
shown. These will be outbound crossing
spokes.
17. Hang the spokes down as shown in step
11, then flip the wheel over and fan out the
spokes as shown here. Now, the left side of
the rim is up. Do 3X crossing as in step 14.
R
18. This is the wheel all laced up, but not
tensioned. The right side is showing, the valve
hole V is at top, and the #1 spoke is to the left
of the valve hole. All the spokes are uniformly
loose. The valve hole is located between two
nearly parallel spokes. The spokes are offset
to their correct side hub flange.
7
R
B
A
1
V
D
C
19. Also, in this uniformly loosely spoked wheel, each pair of midcrossed spokes (circle
A) from the same-side flange occupies every other hole in the rim. See circle A and
sample spokes C and D above. Circle B shows where the outer crossed spokes are, and
these outer crossings should be about the same distance from the hub. All nipples are
screwed down so that approximately 1/2 of the spoke threads are showing.
Next, Part II,the wheel has to be
tensioned, stress relieved, radial
trued, lateral trued, and dished.
........Part.II.coming.up.in.April.2012........
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