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Restoring a hydro unit...By Michael Hackleman

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Restoring a hydro unit...By Michael Hackleman Powered By Docstoc
					     E NERGY W ORKS



 Restoring a hydro unit
      The alternator is the mainstay of wind and water
     power systems and homebuilt standby generators

[This is the second in a series of articles on     electricity-producing device in their
hydropower. Last issue, in Do-it-Yourself          own projects.
Hydro Survey (Jan/Feb 2001), I detailed how
to evaluate the potential to generate power          Donna D’Terra wanted to supple-
from the runoff or the seasonal or annual          ment the energy produced by her
flow of water across one’s land. This article      solar-electric modules at Motherland,
details alternator rebuilding and simple,          her homesite and retreat center locat-
practical control circuits for these systems,
including homebuilt ones. The hydro unit           ed in the mountains outside Willits,
restored in this article is part of an installa-   California. More specifically, she
tion in progress and will be the subject of an     wanted to cut back on the cost and
article in a future issue.}                        noise of a standby generator in the
                                                   winter when the waning sunlight           Michael Hackleman holds
        By Michael Hackleman                       reduced panel output.                     refurbished alternator parts.
                                                     A site survey established that she

T
        he alternator has replaced the
        generator as the preferred way             could take advantage of the energy of       The hydro unit appeared to be in
        to produce low-voltage dc for              several streams that flow seasonally.    good shape. I reached in with my
recharging the battery and powering                As well, I was able to confirm that a    hand to discover that the Pelton
lights, wipers, and other big loads in             used, Pelton-type hydro unit she had     impeller was both intact and virtually
today’s automobiles. The alternator                traded for work several years previ-     unworn. The impeller has twin rows
has found further application in pro-              ously would operate in this applica-     of tiny, spoon-shaped buckets distrib-
ducing electricity in wind and water               tion.                                    uted equally around the rim of a cen-
energy systems and standby genera-                   Using the hose-and-pressure gauge      ter-punched disk. The all-plastic part
tors, and is a favorite with manufac-              method of establishing head (see Do-     has 17 buckets to a row, or 34 buckets
turers and hobbyists alike. I was                  it-Yourself Hydro Survey, Jan/Feb        total. The resulting impeller is 5 inch-
recently asked to check out a used                 2001) and the pipe-and-bucket            es in diameter and 1¾ inches thick at
hydro-electric unit as part of a                   method of finding seasonal flow, I       its widest part.
planned water power installation. As               designed the system around a static        There was some resistance when I
most of the effort focused on restor-              head of 100 feet and a flow of 24        attempted to spin the impeller, so I
ing the alternator in this unit, I felt it         gpm. I identified the hydro unit as a    knew that I would need to check the
was a good opportunity to share the                Burkhardt turbine which was pro-         alternator’s bearings. Further inspec-
process with those interested in                   duced locally here in Mendocino          tion revealed that the impeller would
adapting or using such a universal                 County. This unit was reported to be     have to be removed for the alternator
                                                   operational when removed from serv-      to pull through the back of the salad-
                                                   ice. I was asked to check it out. A      bowl housing. A complete disassem-
                                                   control box (missing) would need to      bly of the unit was called for. This
                                                   be purchased or fabricated.              was okay. While I had no idea as to
                                                                                            how long the unit had been in service,
                                                   The hydro unit                           I did know that it would be used in its
                                                     The Burkhardt turbine consists of a    new application for six months at a
                                                   Delco alternator, a Pelton-type          time, 24 hours a day. Every compo-
                                                   impeller, an input nozzle assembly,      nent needed to be in top condition for
                                                   two aluminum spray shields, and a        this extreme duty cycle.
                                                   support framework for bolting the          The spray shield housing functions
                                                   unit down.                               as spray guard and drain guide. The
                                                                                            spray from a jet of water hitting an



48
                                                                          March/April 2001 Backwoods Home Magazine


impeller at high rpm is intense, so the   moment to examine the nozzle assem    -   covered in greater detail in the instal-
spray guard helps keep the surround-      bly. This consists of a casting that      lation article next issue.)
ings dry. The two halves of this hous-    bolts to the inner spray shield and has     With the spray shield halves sepa-
ing are aluminum salad bowls that         a threaded jet in one end (inside) and    rated, the nut that holds the impeller
were adapted to this application. As      a threaded receptacle for the 2-inch      onto the alternator shaft is exposed.
such, the outermost bowl is cut away      pipe at the other end (outside). The      The shaft has a hex-shaped hole
about 1½ inches wide along its rim        size of the jet is critical in matching   machined into its end so that a large
for about a third of its circumference    the head and rate of water flow with      Allen wrench can grip the shaft for
to help route waste water out of the      the turbine for best efficiency.          removing the nut. I didn’t have this
bottom of the unit.                       Selecting the correct size of jet (ori-   size of wrench handy so I contemplat-
  I removed the bolts that held the       fice) is part of the “tuning” process     ed my options.
two bowls together around the rim         once the hydro unit is in place and         Rather than risk breaking the
and separated the two halves. I took a    has water flowing to it. (This will be    impeller (a $100 item) by trying to
                                                                                    hang onto it to remove the nut, I
  1                                                         Burkhardt               elected to open the alternator casing
                                                                                    to get at the shaft. After scratching a
                                                             Turbine
                                                                                    line across the casing halves (for cor-
                                                      1. The Burkhardt tur-         rect alignment during reassembly), I
                                                      bine with inlet pipe          removed the four small bolts that held
                                                      and framework
                                                                                    the alternator case together and pulled
                                                      2. Water exits the tur-       off the rear alternator casing. This
                                                      bine through a slot in        exposed the alternator shaft with its
                                                      the outer bowl.
                                                                                    field coils. I was able to lock some
                                                      3. Removing the spray         vise-grips onto one of the solid iron
                                                      shield reveals the            jaws surrounding the field coils and,
                                                      impeller and
                                                      nozzle jet. The impeller      with a medium-sized crescent
                                                      nut can be loosened           wrench, was able to twist free the
                                                      with a crescent wrench        impeller nut at the other end of the
                                                      on the nut and an Allen
                                                      wrench on the shaft ...       shaft.
  2                                Inlet pipe                                         To complete the disassembly, I
                                                      4. ... or by grasping         removed the four bolts holding the
                                   Spray shield(s)    the field rotor with
                                                      vicegrips.                    framework and the rear bowl housing
                                                                                    to the alternator’s front casing and
                                   Nozzle Assembly 5. Case halves, field
                                                                                    this separated all the parts of the unit.
                                                   rotor, and impeller
                                   Nozzle Jet                                       Incidentally, the hydro unit weighs 17
                                                                                    pounds, with the bulk taken by the
                                   Crescent wrench                                  alternator (10 lbs).
                                   Vicegrips     4                                  The alternator
                                   Impeller                                           Opening up an alternator may seem
                                                                                    daunting the first time you do it, but
                                                                                    it’s really no big thing. In pulling the
   3                                                                                alternator’s rear casing off the rotor,

                                                                                5




                                                                                                                         49
March/April 2001 Backwoods Home Magazine



two brushes leap from their sockets.       are small brushes and they don’t work      and Hungarian bearings to higher
At this point, you may wonder how          very hard. The sliprings had a nice        quality ones for a cost of $17.
will you hold them in their guides         chocolate brown look to them, which
until you push the rotor back and the      is good. The brushes still had plenty      Checking the diodes
brushes are once again held against        of length (which decreases with              It was time to check the diodes. The
the rotor’s sliprings? If you look care-   wear), a smooth curvature to fit the       diodes in an alternator can be checked
fully, you’ll see that the manufacturer    sliprings themselves, and were not         with a standard multimeter but the
solved this by providing a hole in the     gouged, burned, or pitted. The brush       process is somewhat involved for the
rear housing. Professionals insert a       leads were neither frayed nor corrod-      novice (Sidebar A).
paper clip through it to temporarily       ed. Brushes are not expensive but new        My measurements resulted in some
hold the spring-tensioned brushes in       brushes must be “arced” to the             distinctly different readings between
their guides. Alternately, a thin wire     slipring curvature. This work is           some diodes, so I opted to take the
may be routed over the brushes and         unwarranted unless the brushes must        casing to a local alternator shop.
out another opening and twisted            be replaced for one of the aforemen-       Their test equipment, designed specif-
together. Once the rotor is back in        tioned reasons.                            ically for testing diodes, confirmed
place, the clip or wire is pulled out        I used a multimeter to test the field    the same borderline readings. Since
and the brushes will seat against the      winding’s resistance. With a test lead     these values can be influenced by a
sliprings.                                 held against each of the copper            high-resistance path across the diode
  Whenever opening something for           sliprings on the rotor, I observed a 4.2   surfaces (usually a result of corro-
the first time, it’s important to posi-    ohm reading. I did the math. Volts         sion), a shop worker bead-blasted the
tion the parts on the bench and simply     equals amps times ohms. Therefore,         entire rear casing and retested.
look at them. Troubleshooting starts       amps equals volts divided by ohms.         Everything checked good. In a split
with careful observation. What was I       12V divided by 4.2 ohms equals 2.85        second, the technician even popped in
looking for? Signs of arcing or burn-      amps. That’s close to the approxi-         a rear bearing. (Darn if it wasn’t the
ing or open-ended (disconnected)           mately 3 amps I knew the field would       same one I’d just bought.). Since I
wires are not good. If the unit shows      draw.                                      had brought the alternator in disas-
evidence of this kind of damage, deal        The front and rear bearings were my      sembled, I was only charged $5 for
with it first. Alternators are not that    next focus. The front one was a stan-      the 5 minutes of time this entire
expensive, new or re-manufactured,         dard ball bearing. The rear one was a      process took.
so anything beyond your ability to         much smaller, needle-roller type.
rectify easily or inexpensively is not     Both turned smoothly but slowly. I         Assembling the unit
worth it. As well, alternator shops can    pealed the plastic side off the front        I was now ready to reassemble the
do everything I did to this unit and       “sealed” bearing. The lubricant inside     hydro unit. I relied on photographs I
have the tools, parts, and experience      was dried and crusty. I felt tempted to    had taken of the unit before disassem-
to handle all alternator brands.           soak out the old lubricant and repack      bly to help orient everything correct-
  This unit passed the initial visual      the bearings with good grease.             ly.
inspection. The brushes (rear casing)      However, with no knowledge of the
and sliprings (rotor shaft) drew my        history of this unit, I opted for new
attention next. The brushes transfer       bearings. Toward this end, I removed
                                                                                           7
power to the field coils in the rotor      both bearings, using a socket and
through the sliprings. Since the field     shaft extension like a punch to drive
coil in a standard alternator only         them out. The local bearing distribu-
draws about 3 amps at 12 volts, these      tor was able to upgrade these Chinese
                                                     Stator coils          Front bearing
   6                                                 Brush assembly       Brush springs
                                                     Rotor slip rings     Impeller plate

                                                     6. The rear alternator casing
                                                     and field rotor.

                                                     7. The front bearing is packed
                                                     with grease. The backing plate
                                                     and impeller are ready to
                                                     install on the rotor shaft.



50
   E NERGY W ORKS                                                            March/April 2001 Backwoods Home Magazine


  Since I would need the grip on the       bearing to help keep out water. Next,     the inner spray shield to further
rotor to re-install the impeller nut, I    I slid the bushing onto the shaft of      waterproof the unit.
began by installing the new sealed         the alternator rotor and inserted the       Alternators have two mounting
ball bearing and its retaining plate in    shaft through the front bearing in the    holes, one larger than the other. The
the front alternator casing. Since this    alternator casing. I squeezed out a       hole for the smaller bolt is threaded,
bearing is within an inch of the           thin coating of Form-a-Gasket (non-       so its bolt is inserted from the inside
water-driven impeller, I packed plen-      hardening type) onto the front of the     of the bowl and is simply tightened
ty of Lubriplate on either side of the     alternator casing and mated it against    down. The larger bolt slips through

                                                                                                8. The nut is removed
Sidebar A: Alternator diodes                                      8                             from a stator terminal
                                                                                                to free two diode leads.
  Alternators have rotating      pressed into tight holes and
fields and stationary stator     are difficult to remove. To                                    9. A grocery tie holds
windings. As the name            test them in place, a diode                                    the brushes in place
implies, the field coils on      lead must be disconnected                                      before the rotor is re-
                                                                                                inserted in the casing.
the rotating core generate       so that each diode is essen-
an electromagnetic field.        tially “out of the circuit”
The stator (power) wind -        and not influenced by other                                    Diode in standoff plate (3)
ings are stationary and pro-     wiring or diodes.                                              Stator terminal (3)
duce electricity up to 35-45       The process of checking                                      Diode in rear casing (3)
amps at 12V as a result of       the diodes begins by locat-
rotation through the field.      ing the stator windings.         Third,      pay
The field coils receive          These are wound in a frame       attention to                                          9
power from B+, or the            that fits the inside curvature   detail. This
alternator’s output through      of the casing and they han-      ensures proper
graphite brushes in contact      dle all the power generated      reassembly,
with sliprings on the rotor.     in the alternator. Three         particularly in
The stators are wound to         wires from this array termi-     that nothing
produce 3-phase ac electric-     nate on three separate posts     shorts out or
ity which is converted into      on the rear plate, each wire     drags against
DC with diodes. Each             representing 1 phase of the      the rotating
phase needs two diodes,          generated 3-phase output.        parts. Finally,
each one of which are            The leads from two diodes        alternators are
ganged together at B+ or         also attach at each post. So,                                  Stator lead
                                                                  not all the same. Adapt my
ground.                          three windings (phases) =                                      Brush holder
                                                                  procedure to fit your alter-
  So, there are six diodes       three posts = six diode                                        Grocery tie for brushes
                                                                  nator.
mounted in the alternator—       leads.                             I used a small nut driver
three in the rear casing and       A few words of caution         to remove the nut from one standoff plate) in which the
three in a metal plate that is   before you tackle this. First,   of the posts where the stator diode is embedded. A conti-
electrically-isolated from       it’s a small space and the       windings meet the diode nuity tester will show cur-
the casing. Unless there is      stator wires are stiff. Be       leads. I used needlenose rent flow in one direction
reported trouble with the        gentle and don’t move any-       pliers to gently lift the only, so reverse the multi-
alternator’s output, the         thing more than you have         diode connectors off the meter leads, finding first
diodes are generally             to. Second, make a draw-         post, removing other leads continuity, then no continu-
assumed to be good and are       ing. At least, it’s a good       only if necessary to get at ity. This tells you if the
left alone. A diode in your      place to write down the          the diode leads. I figured diode is good or bad. I also
hand is easy to test with an     readings. It’s also a great      that working with one ter- tested these diodes with the
ohmmeter or a continuity         guide during assembly            minal post at a time would ohm function of the multi-
tester (both functions are       when you can no longer,          prevent any crossed wires.    meter, providing me with
found on inexpensive multi-      perhaps a few days later,           I touched one lead of the actual values of ohms (a
meters) to find out if it’s      remember which of several        multimeter to the diode lead measure of resistance) in
shorted or open. However,        possible ways something          I had just freed and the each direction for each
alternator diodes are            might go back together.          other to the metal case (or diode.



                                                                                                                          51
March/April 2001 Backwoods Home Magazine


the bowl and the alternator flange. At     lead on the F+ (Field positive) post        opted to fabricate a control box from
this point, I slipped the support frame    and the other at the B- (Battery            scratch, mostly copying the original
for the hydro unit over the exposed        minus, which is also F-) post. The          design.
threads and added nuts to each.            reading was the same as before: 4.2           I strayed from the original design of
  The impeller is held to the alternator   ohms. This one test confirmed a good        the control box in two ways: how the
shaft by a big brass nut and a large,      electrical contact through the termi-       field coils are energized and where
thick brass backing plate. I slid the      nals, brushes, sliprings, and field         the external shunt is located (Sidebar
plate onto the alternator shaft, pushed    coils.                                      B and Fig. 11). The first one simpli-
the impeller into place—ensuring that                                                  fies the circuitry and reduces the
its buckets are correctly oriented to      The control box                             amount of the output power that is
the nozzle—and added the nut. As             The control box for the Burkhardt         taxed to energize the field coils. The
with disassembly, the vice grips held      turbine was missing in this applica-        second increases the accuracy of
the alternator rotor while I tightened     tion. The circuitry requirements for an     monitoring power output from the
the nut against the impeller, being        alternator in a hydro unit are nearly       system and avoids running large wires
careful not to over-tighten it.            identical to those used in a windplant      through the control box.
  I was ready to install the field         or a standby generator—an ammeter,            I obtained a rheostat—rated at 28
brushes. This job requires some dex-       a diode, a rheostat, a fuse, a terminal     ohms (resistance) and 50 watts (heat
terity. I set the rear alternator casing   junction, and an enclosure (Fig. 10).       dissipation ability)—directly from
onto a towel on my workbench so that       The ammeter displays alternator out-        John Takes, who owned and operated
I had both hands free. I inserted a        put (current) in amps. The diode            Burkhardt Turbines for many years.
spring into the rear brush holder and      blocks battery voltage from powering        For a 12-volt system, a 12-ohm rheo-
held it in place with a screwdriver.       the field coils, which rely instead on      stat is generally more appropriate, but
With my free hand, I grabbed the           the residual magnetism in the rotor’s       I will try the 28-ohm one first. (This
brush with needlenose pliers and ori-      iron for excitation. The rheostat           will be tested when the hydro unit is
ented it over the spring, slipping out     (another name for a potentimeter or         installed and water is available to it.) I
the screwdriver as I pressed the brush     variable resistor) manually adjusts         purchased the fuse holder and fuse, a
into place. I inserted a grocery tie       field current, replacing the function of    pushbutton switch, terminal strip, and
(used for holding market vegetables        the voltage regulator used in automo-       enclosure from a local Radio Shack
together) through the hole in the rear     biles. The fuse protects the field from     for this circuit. I used terminals for
casing and across this brush to hold it    too much electric current. The termi-       multimeter test leads from my own
in place. I repeated this process for      nal strip helps with electrical connec-     parts’ stock.
the front brush, then routed the gro-      tions between the unit and the alterna-
cery tie out another hole so that I        tor and battery pack. Finally, the          Construction tips
could twist the two ends together out-     enclosure protects these components          After a careful inspection of the sys-
side the casing. This process is           from the environment.                      tem schematic, I recognized that the
tedious because the brush leads are          Since I had the tools and experience     control unit was basically handling
short and already anchored to their        to assemble such a simple circuit, I       field current circuitry and a small bit
terminals. Be patient or you’ll be                                                                 of metering. Its container
starting over a lot.                                                                               would mount the rheo-
  Since the rear needle-type bearing                                Rheostat                       stat, pushbutton switch,
                                            Alternator                               Fuse
was already installed in the rear alter-                                             (5A)          two meter terminals, a
nator casing, I was ready to join the           R     F                                            fuse, a terminal strip, and
alternator halves. I slipped the rear                                                              interconnecting wires.
                                               Grd    B+
casing over the rear of the rotor and                                                                Accordingly, I selected
aligned the scratch marks I’d made                                                                 a 5-inch long, 3-inch
(before disassembly) with those of the                                    A                        wide, and 2-inch deep
                                                                                     Diode
front casing. I inserted and tightened                               Ammeter                       plastic box for the control
the four case bolts.                                                                               unit. (It was a tight fit; a
  Once the alternator was assembled,                                                               novice might want to
I untwisted the grocery tie holding the           To                    Control Box                pick something larger.)
brushes in place and pulled it out. I        Battery Pack                                          Since the control unit is
again checked the field coil resistance                         Fig. 10: A basic control           attached to (or near) the
with my multimeter, placing one test                            circuit for an alternator          hydro unit itself, it is



52
    E NERGY W ORKS                                                             March/April 2001 Backwoods Home Magazine



exposed to a water environment and           ly embrittle it. I also rejected the use     pushbutton switch and the two meter
must be fairly waterproof. I initially       of a steel box, since it would require a     terminals. Other considerations in
considered using a Tupperware con-           grounding rod at the hydro site.             layout? Components should not inter-
tainer for this application because it         The rheostat is large and takes up         fere with each other. Wires take up
provides great access and seals so           most of the room, so I positioned this       space, so allow for them. Finally,
well. I rejected this idea only because      at one end of the box. The only other        position the exit hole in the end face
I thought the sunlight might eventual-       holes in this face of the box are the        of the box to permit easy hookup of

Sidebar B: Control box
                                                                                                                Rheostat
  The control box I built         age (and, therefore half the        Alternator
uses a field circuit modified     current) normally available                                       Fuse (5A)
from the standard field cir-      at the B+ terminal.
cuit and measures output            The control circuit that              R     F
current differently.              takes advantage of the R                                                   Push Switch
                                                                         Grd   B+
  1. Field connection.            terminal (Fig. 11) is radi -
While the diode (as shown         cally different than the one
in Fig. 10) provides a way        using a diode (Fig. 10). A
to supply field current to        critical component in this
                                                                                                    -        +
the alternator, it also assess-   setup is the momentary-                                           Test Points
es its own tax for this effort.   contact, pushbutton switch.
Common diodes dissipate           Without it, the field coils                                       Control Box
(as heat) as much as one          might not self-energize
watt per amp—a whopping           because of the lower volt-                             Shunt
35 watts for a 35-amp out-        age available from the R
put—due to their own inter-       terminal.       Fortunately,                               Fig. 11: An improved control
nal resistance. If you            hydro-electric units that               To                 circuit for an alternator
choose to use this circuit,       employ the Pelton-wheel            Battery Pack            in a hydro-electric system
use a Schottky diode. While       are “tuned” for a specific
more expensive, it will           head and flow of water. As        a built-in shunt. While this    gage wires may then be run
reduce this loss by half.         such, the reduced current to      is nicely packaged, this        to meters or terminals that
  However, there is a way         the field coils is part of this   type of meter offers poor       accept the test leads from a
to avoid the use of a diode       tuning process. Once              resolution for anything         multimeter. In this applica-
altogether which works            adjusted, the hydro unit          except mid-scale readings,      tion, I wanted to mount the
especially well with hydro-       may be energized by the           must be waterproofed, and       shunt near the battery pack
electric units and standby        owner via the pushbutton          limits output readings to the   where it would pull double
generators. (Sorry, it won’t      switch and, thereafter, left      immediate vicinity of the       duty, monitoring the output
work well with homebuilt          unattended.                       hydro unit.                     of the existing solar mod-
windplants.) This method            Two cautions. First,              I elected instead to use a    ules. From there, I could
relies on the use of the R        momentary means momen-            standard meter shunt. This      run small wires to test
(rotor) terminal on Delco         tary, i.e. less than a second.    calibrated gizmo offers         points in the control box at
alternators (or the similar       Any longer and there is risk      accurate readings to within     the hydro site.
spade terminal of other           of blowing a diode or the         1/10th of an amp of current       A side benefit of this
alternator brands) to supply      fuse. Second, don’t miswire       across the range of amper-      arrangement was that I did
field current. The R termi-       the circuit, or you can add       age measured when used in       not need to mount the shunt
nal actually taps one rotor       heat and fire to the symp-        conjunction with even a         inside the control unit,
phase in the alternator           toms listed above. If you         cheap ($20) digital multi-      thereby avoiding having to
while the output leg (B+)         can’t get it to work, go back     meter. The advantage of the     route large-gage (power)
represents three phases.          to the circuit shown in Fig.      shunt is that it may be         wires through the control
The difference? The R ter-        10.                               mounted anywhere in the         box itself.
minal is connected to one           2. Meter shunt. The orig-       line between the control
stator and produces ac (not       inal design of control box        box and its connection with
dc) with about half the volt-     used a stock ammeter with         the battery pack. Small-



                                                                                                                             53
March/April 2001 Backwoods Home Magazine



                                           Fig. 12: Components for the con-         heat up, catch fire, and melt. Too
                                    12     trol box are based on the circuit        large and they are harder to work
                                           illustrated in Fig. 11.                  with. From the schematic, I readily
                                                                                    knew that the control unit is only
                                           Fig. 13: Draw a wiring diagram and       handling field current (3 amps) and a
                                           check it against the schematic           metering circuit (0.1 amps). Stranded
                                           before you start construction.           #12 wire is more than adequate for
                                                                                    the field current and stranded #18 (or
                                                                             13     smaller gage) wire works for the
                                                                                    meter circuit. (Stranded wires con-
                                                                                    duct dc current better than a similar
                                                                                    gage of solid wire, like that used in
                                                                                    Romex for ac wiring in homes.)
                                                                                      Wires of different color help you
                                                                                    keep things straight as you hook
                                                                                    things up. More significantly, they
                                                                                    will aid the eye in tracing one wire
                                                                                    through the maze of other wires.
the external wires to the terminal                                                  While this is very helpful in trou-
strip.                                                                              bleshooting, it has a more immediate
  If you’re fabricating something                                                   benefit: checking your work before
yourself, a wiring diagram is impor-                                                you hook it up and apply power to it
tant, so make one. At least, it mini-                                               for the first time.
mizes confusion, which usually leads                                                  In ac circuits, black is power, white
to mistakes. Better yet, it helps you                                               is common, and green is ground. In
figure out the best way to hook                                                     dc circuits, red is positive (power)
something up. The easiest way is not                                                and black is negative (common).
always the best way. For example, it                                                Since I was limited in the color wire
would have been easier to avoid            The layout will help you decide their    available to me in this construction
using a terminal strip. I could much       length. While the shortest distance      and the circuits weren’t really power
more easily route all of the wires         between two points is a straight line,   circuits, I followed neither of these
straight out of the box directly from      it’s not always practical. My work       conventions. However, I did maintain
their connections with the compo-          with communications and radar            the same color on each side of the
nents.                                     equipment when I                                             terminal strip, so
  I used the terminal strip for three      served in the U.S. Navy                                14 that the colors of
reasons. First, it makes it easy to dis-   taught me the virtue of                                      the external wires
connect and remove the control unit        routing wires in a neat                                      had a corresponding
from the hydro system and, then, re-       and orderly fashion.
install it without disturbing the bulk     Basically, you want
of the internal wiring. Second, the        them out of the way.
wires can’t be easily ripped from the      More importantly, you
unit since the terminal strip won’t fit    want to be able to                                          Field rheostat knob
through the exit hole for the wires.       remove components
Finally, a terminal strip makes for        later without having to                                     Pushbutton switch
easier troubleshooting by minimizing       undo wires just to get at                                   for field excitation
the possibility of inadvertent shorts      or extract them.
when probing through wiring to               What about wire size                                        Test points to
reach test points. I believe that any-     and color? It’s a good                                      measure alternator
thing I can do to help anyone who          rule of thumb not to use                                      output current
might later work on the unit is worth      wires any smaller o r
the extra effort it takes.                 larger than they need to                                   Fig. 14: The
  The components inside this control       be. Too small, they may                                    completed hydro
box are interconnected with wires.                                                                    unit’s control box



54
    E NERGY W ORKS                                                             March/April 2001 Backwoods Home Magazine


color match in wires from the inter-           There is wisdom in the notion of        shunt)—and use silicone sealant to
nal components.                             minimizing the number of exposed           weatherproof the exit. Accordingly, I
  One tricky job is wiring up the           connections in electrical circuits, so I   drilled a ¼-inch hole and fed through
rheostat correctly. Most military,          purchased a bag of heat-shrink tub-        the first three wires. Their ends were
industrial, and commercial electric         ing of mixed sizes. When exposed to        stripped, shaped, and tightened under
and electronics devices are built with      the heat from the tip of the soldering     screws on the terminal strip. I cut
a common understanding that clock-          gun, a match, or a butane lighter, this    these wires to equal lengths, about 18
wise rotation increases something,          stuff will shrink to about 60% of its      inches long, which should easily
i.e., more volume on a stereo,              original size, forming a snug fit over     reach the end of the alternator from
brighter light with a dimmer, etc.          the joint. As needed, I selected the       the mounting position on the frame-
Since the rheostat’s job is to limit        correct size (50% bigger than the          work. I soldered a ring-connector to
current to the field, it was wired so       wire itself) of tubing, cut it to a        the wire that goes to B+, and added
that turning the knob clockwise (cw)        length that would overlap the joint,       push-on connectors to the ends of the
increases the field current by              and slipped it over the wire before I      other two, for connection to the F+
decreasing the in-line resistance.          physically secured the wire to the         and R terminals on the alternator.
Thus, counterclockwise (ccw) limits         terminal with needlenose pliers.           Once the control box is installed on
the field current by increasing resist-     Adding a little flux, I was ready to       the hydro unit, the two wires from
ance. Since the rheostat is wired           solder the connection. If you’re           the remote meter shunt will be fed
from the back side, it’s easy to get        holding any part of the joint (i.e., the   into it, and also connected to the ter-
confused and wire it backward.              wire itself), hold it still for a full     minal strip. Afterwards, I will use sil-
Doublecheck it. Did you do it back-         three seconds after removing the heat      icon sealant on the inside and outside
ward? Simply swap the wire from the         of the soldering iron or gun.              of the exit hole to effectively seal this
outside terminal on one side of the         Otherwise, the molten joint may not        opening against the elements and
rheostat to the other side to reverse it.   set, resulting in a cold-solder joint      insect life.
  There’s a protocol to getting good        and a weak electrical connection.            I like to add schematics and/or
electrical connections. The first rule      After waiting 15 seconds for the sol-      wiring diagrams to black boxes, so I
of a good connection is to make it          dered joint to cool, I slipped the         embarked on this final task. The
physically strong, such as a wire           shrink-tubing over the joint. Just the     resulting diagram is a mix of a
under a bolt, a wire lug under a bolt,      radiant heat from a soldering gun          schematic and wiring diagram, with
etc. The second rule is maximum             will shrink the tubing. With practice,     particular emphasis on the terminal
surface area of contact, best accom     -   the result has a professional look to      strip and the colors of the different
plished by soldering. Over time, the        it.                                        wires. I reduced this image to a size
weak link in wiring between compo-             Once the control box was wired          smaller than the back plastic cover.
nents is usually a connector, i.e., a       internally, I performed a visual           Once positioned, I used fiberglass
plug, a receptacle, or a joint. I resist    check, tracing the wires to their          tape in overlapping strips to secure
using spade (slide-on) connectors for       respective terminals and components.       and seal this artwork against the
this reason. Consequently, I soldered       I followed this up with an electrical      cover inside this cover, and used the
wires to a number of components in          check, using my multimeter. Most of        four screws to secure the cover to the
this box. If your skills are less devel-    this is a simple continuity check—         control box. Once the hydro system
oped, purchase these spade connec-          does this connect with that?—but I         is installed, I will add a tiny bead of
tors from a local hardware or Radio         used the ohms scale on the multime-        Lubriplate or similar compound
Shack. Also purchase the special            ter to confirm the full resistance of      around the perimeter of the cover
crimping tool for these connectors          the rheostat (28 ohms) and to con-         plate (before screwing it on) to fur-
and learn to use it correctly.              firm that this value decreased as I        ther seal it against weather.
(Crimping is the process of squeez-         turned it clockwise.                        (Michael Hackleman, P.O. Box 327,
ing the soft metal of the connector            The next job was to drill the exit      Willits, CA 95490. E-mail: mhackleman
around an exposed end of a copper or        hole for the wires that run to the         @saber.net]) ∆
aluminum wire.) Using crimpers              alternator terminals and meter shunt.
avoids the bad crimps that result           I figured to size this hole just large         To read more of Michael
from misapplying needlenose or reg-         enough for the wires—two #12 wires           Hackleman’s energy articles,
ular pliers or diagonal cutters for the     (rotor and field), a #14 wire (B+),            visit BHM’s webside at
job.                                        and two #22 wires (+ and -, meter            www.backwoodshome.com.




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