This one is easier - just a bit expensive.
1. Motor - 1750 rpm continuous duty 1/2 horse
2. Small pulley for motor
3. Larger pulley for drive shaft (the one in the picture is too large.. think a 5" or 6" would be better)
4. 6' of iron bar for roller shafts (I think these are 1/2")
5. 4 bearing blocks - which are quite expensive for what they are - but they simplify things quite a bit - they are articulated so slight mis-alignment doesn't hurt. They are also known as pillow blocks
6. Heater hose for the rollers
7. Drive belt that fits the pulley system (you can adjust the position of the motor to fit many sizes)
8. Four collars for the roller shafts.
9. Two small model wheels or rollers to act as stops on each end of the roller bars - this stops the jar from creeping to the end of the roller and binding on the wood (a problem with some of my
jars - the rollers aren't shown in this picture)
10. Some misc. hardware like washers, wood screws, etc
11. Wood or wood scraps to make a base. I used 1x2 for the bottom, covered
those with 5/8" ply and used 2/4 for the roller mounts (KISS!).
All the parts except for the motor can be purchased in an Ace Hardware store. You can get everything cheaper somewhere else - but you have to shop quite a bit. Harbor Freight has good deals on continuous duty capacitor start motors.
You can also rob a washing machine motor - go to Sears and look for junked
trade-ins.
I use a Thumler's Tumbler 15 pound drum on
this but it can use any number of homemade drums, too. The one thing this
version lacks is a handle to pick it up. I later added that and am
thinking about building an enclosure for it... it is soooooo
noisy!
An octagonal barrel (or a breaker bar glued inside a round
barrel) works fine for low speeds (Thumler's Tumbler Octagonal barrel is
an example). For higher speeds, the 'wave' of media works without the help
from the ramped edges. I have used both and have had satisfactory results
at both high and low speeds. I use homemade barrels now (Kyle's design
from Passfire) and I like them better than the commercial or Sponenburgh
versions. They are six inch round PVC with two breaker bars cemented
inside them. You can see how they are built by looking in the Passfire
archives. I made ends out of Formica covered shelving (seconds at the
lumber yard for $1 each). If you go this way, be sure to duct tape them
before each mill job to ensure dust doesn't leak out.
Media selection depends on what you want. Large media breaks stuff up
faster. Small media breaks it up finer. For a 4 inch barrel, 1/2 inch
media (45-54 cal. balls) seems about right. For 6 and 8 inch barrels,
3/4'' media (cylinders 3/4'' round and 1-1.5 inches long) works great. The
smaller media would still work in the larger barrels (if you had enough of
it). Round or cylindrical media is most used. Anything will work but it
might not be as efficient.
The charge on the barrel, if your motor can swing it, should be about
1/2 of the barrel full. For a six inch jar, that is about 30 pounds. Spin
it up to 60 or more RPM.
A Quiet
"In Shop" Mill
for small single chemical jobs
I wore out a Harbor Freight mill so I decided to salvage
what parts I could and make a 4" mill for doing 'quicky' jobs. The
larger mills are great but I often want to mill 100 grams of composition
and the large mills are not good for that. The following pictures show
what I came up with. The motor is a 1/6 hp quiet motor. The max size jar
that will fit is a 4" one but the large Sponenburgh type 4" jar
will work. However, the PVC is noisy! For milling single
chemicals around the shop, the quiet rubber jars that came in the Harbor
Freight mills are perfect. This cost about $49. I had to make some
brass bushings to hold the 8mm rollers onto the angle iron and a brass
shim to mate the 1/2" core pulley to the 8mm roller bar.
Parts list:
1. 1/6 hp motor from eBay, $23 plus
shipping (bought some other stuff with it so let's say $5)
2. Angle iron (scrap)
3. Well pump pulleys from Ace Hardware ($11)
4. Belt for pulleys ($5.98)
5. Nuts, bolts, washers, screws, cord pins from
scrounge box (maybe $3 if purchased)
6. 10" square of 1/2" 5 ply plywood from
stock (50 cents?)
7. A few pieces of scrap brass for bushings (could be
made with a hand drill if you are pure of heart)
|
What parts did I salvage from the old mill?
(Answer: The power cord, the rollers, the jar, and end caps for
the rollers - so... not much!)
|
A 4" PVC "Sponenburgh" jar will
work, too
|
|
Here is the bottom of the setup. The
belt is tightened by adding washers to the motor
mount.
|
A 32 Cue Firing Panel
And this one is easier and reasonably cheap. It is a fishing
tackle box with a wood shelf that has four grounds and eight connections. A
glorified nail board! Inside the box are the batteries, spare parts, and even
a single firing unit with its own cable roll. The cable for the main unit is
carried on a separate spool and enters the box through a hole cut in the side
. The cable is six sets of 18 gauge speaker wire that are bound with tape to
prevent fouling. The wire is color coded on the ends. Spade clips and
butterfly nuts are used to connect the cable to the box. Alligator clips are
used to connect to the e-matches on the firing line.
A 6 Cue Firing Panel -
Just Right for Backyard Displays and Rocket Launches
With a little effort, you can build a nice backyard firing
box. Here is a six cue with a test circuit. Click on the above picture to
see a test of the box.
Test Switch Diagram
The nine volt test circuit is isolated
from the main power and uses a 12 volt green LED in series with the firing
circuit. This limits the current to about 18 milliamps.
Primary Circuit Diagram
The internal power is 24 AA cells (36 volts).
The internal power will ignite a 2.5 ohm 1/8 watt resistor virtually instantly - it does not
flash the resistor like a CD firing box does - the result is a broader and longer
lasting flame that would not need a pyrogen for most applications. A provision
for external power up to 250 volts (like I'm going to hook 250 volts up to
it!) is installed and it uses both Cat 5 (RJ 45) connectors and speaker connectors.
The firing panel is made with a Radio Shack project box and
switches from eBay and Harbor Freight. The 'Fire' switch is momentary and the
'Arm' and Internal/External power switches are DPDT.
When the 'Arm' switch is thrown, the test circuit is taken off
line so higher voltage can be applied without conflicting with the test
voltage. The test voltage battery is used to light the 'Arm' light - the red
LED - when the test circuit is taken off line.
The cost of materials was about $40 - including batteries -
but I probably spent about $100 experimenting around until I got what I
wanted.
A Six Tube Rocket Loader
A little while back, I was making some wheels, each of which
required four end-burning drivers - it was taking quite a while to turn out the drivers in
any quantity so I was looking for a way to speed things up. While
reading Best of AFN III, a short article on how to use a railroad tie plate as
a base to make a multiple tube rocket loader caught my eye. See it yourself -
it is on page 38 and is called 'Informal 8 oz Rockets'. Loading six tubes on
the same stand seemed like it would be easier than loading one tube at a time.
I scrounged around an abandoned railroad line and found a tie plate that was
in a ditch. Then I made six nozzle bases for 5/8" rockets, drilled and
tapped them, and then threaded some 3/16" rod and ran through them. The
ends were fastened to the base plate by a stainless nut on the back side of
the plate. Four extra holes were drilled to mount the whole thing to a heavy
plank.
Just about any heavy plate will work - in fact, the railroad tie plate is
probably a marginal choice since it is not a flat piece of metal. It does the
job, though.
Static Test Stands for
Rocket Motors
Click on the image above to see a video of the stand firing
with a 3/8" nozzleless motor on it. The sound you hear after the initial
thrust is the delay mix - it doesn't generate much lift so there is no
indication on the scale.
The scale is a fisherman's scale, the bar is aluminum, the
scale is adjusted so it is at zero when the bar touches the stop on the
right. The adjustment is the turnbuckle on top of the scale. There is a
piece of rubber inner tube holding the bar from swinging out - you can
just see the tube behind the bar on top of the left column. It doesn't
want to swing out much anyway. The length of the bar is three feet.
The scale can be placed at one foot or at six inches from the fulcrum (the
column on the left). Right now, any readings are divided by 4 since the
scale is on the 6" mark from the fulcrum. The lever is two feet long.
The holder for the rocket motor (far right) is a piece of angle iron
with a wood pad on top. The pad can be removed and different size holders
can be inserted. Total cost was about $10 not counting the scrap bits that
I had hanging around.
The stand is meant to be used with a digital video camera.
The dial scale is filmed while the motor is running and then the film is
examined frame by frame to get the motor profile.
Here is another version that has a more sensitive scale
(6.6 lbs/3 Kg fully deflected). This is a Kitchen Chef stainless steel
scale with the bowl permanently mounted - the bowl acts like a deflection
shield and protects the scale in case of CATOs. This test stand is used
for smaller motors and tests are meant to be recorded using a digital
camera. Finding a kitchen scale that was robust, reasonably accurate, had
a zeroing capability, and with 5-6 pounds full deflection was hard
but I finally found one on eBay for less than $20.
Here is one that uses a Harbor Freight short bodied ram (5
ton) hooked to a 30 PSI dry gauge.
see: PtoF for a full story on how to make the
gauge setup.
The different holders on top will fit various size rocket
tubes. The pressure gauge can be moved along the
bottom to take advantage of the leverage of the motor arm. In practice,
the test burn is video taped and the
frames are then stepped through to get the thrust readings from the gauge.
