Hummers

1. Fun little doo-dads that look best if the fuel has a metal (like RPH with titanium)..  inch or so long.  
2. Clay at both ends, center vent at tangent to inner wall of tube. 
3. Short and fast fuse.  The fuse in the example above is the fast Visco available from Skylighter. 
4. It has to be split and primed a bit before stuffing in a shell or mortar/mine. I leave them unsplit for storage. 
5. Put them in a rocket nose, mortar, or whatever.

 

Bottle Rocket Stand

Homemade Star Board

I probably spent more making this thing than it would have cost if I could have purchased one but I wanted a 3/8" version and couldn't find it.  I got the metal from onlinemetals.com and used my lathe and mill a bit. I really like these things since they make stars lickety split! If you have the equipment, it takes a couple of hours to make one - the pegs on this one are press fit into the peg holder. I fastened the two plates together with machine screws and then drilled both plates at the same time.  The holes on the peg holder do not go all the way through. The 'holey' plate was reamed to be a loose fit (1/64" oversize). Cutting those cotton-picking pegs was a pain. I have since made a 1/4" one - it was feistier than the 3/8" but it finally came together.

Homemade Star Roller

 

 

 

I like using the star board because it is fast. I like using the Star Roller because it makes stars that are great for shells and... well ... doggone it, it is fun! This one was made from an old wheel chair motor (a reject) and a large stainless steel bowl. The motor mount was Dexagon angle iron. Dexagon is general purpose metal that has a bazillion holes in it - sort of like a piece from a grown up Mechano or Erector set.  The only hard part was getting the shaft adaptor made and fitted. The motor has a short shaft and an odd keyway hole so I had to create a brass adaptor with a 3/8" thread on one end and a tube/key hole adaptor on the other.  



Click on the above picture to see the star roller in action with a couple of pounds of 3/8" stars.

The initial roller was a success, so I made some more for friends.

This is the back of the new design that shows all the important bits

 

I had several requests for the Bill of Materials for this so here is what I used on the latest ones I built (I used commercial wiper motors from AllElectronics that ran on 12 volts and used a 2 amp Wall Wart).  This is not exactly a BOM but should suffice.

The angle of the top is 45 degrees. You will find that, using a bowl, you must tilt the roller either in the back or in the front as the size of the stars grow. You can make standoffs out of pegs for this.  See the last two pictures above.

The base is a 2x4 8" long. The height of the upright (also a 2x4) is 6" at the highest. The sticks are 1 x 2 hardwood. I would cut the sticks about 10.5" long and let them run back 2" behind the roller so there is back support. The bracket used to mount the motor is a 4" piece of Dexagon angle. The long side of the angle iron goes against the wood, the short side will usually take two bolts from the motor mount without drilling. You may have to relieve the top of the angle iron to make room for the shaft coming out of the motor. Secure the angle iron to the wood using 1" lag bolts (big screws).

Predrill all holes to preclude splitting. I put a couple of coats of lacquer on the finished wood so it could be wiped down occasionally and not look terrible.

How you wire it is up to you. On the latest version, I ran a wall wart to a Radio Shack project box and put a switch on it. That was the cleanest solution. The easiest is to just directly connect it and turn it off/on by plugging it in or unplugging it.

World's Easiest Star Board

Here it is! Go to the lumber yard and get a recessed light cover. Trim it to the width and height you want. Squeegee in your composition. Let dry. Oh... be sure the composition shrinks when it dries. Most lampblack/carbon based star comps will. Several advantages here - besides the cheapness, ease of implementation, and availability of material,  the stars will have sharp edges and be easier to light. Burlhorse on UKRocketry forum suggested taking two pieces and stacking them so that the star size was 1/2" x 1/2". Use a roller and lightly roll xylene onto one side of a piece of the material. Take another piece the same size and match them up, put a weight on it and a few minutes later you have a starboard that has all 1/2" sides.

 

A Drying Cabinet

 

The idea for this cabinet was drawn from Kyle's cabinet on Passfire.com. Since I borrowed from him, I won't list any specifics. This is not the exact cabinet that Kyle described, though. It has a circulation duct that is mounted on top and it runs down the side (with a 6" computer fan in the top to push air into the duct), a 'personal' dehumidifier and a 100 watt light bulb at the bottom. The temperature, with the cabinet unloaded, gets over 100 degrees F and the humidity will drop to less than 25%. The junk inside the box is some extra light bulbs, AC adapter for the fan,  and the light  fixture and dehumidifier. I've since taken the extraneous junk out and added a light aluminum shield for the top of the light bulb (see right hand photo above). You can just see the duct going down the right side in the picture. It takes air from the inside top of the cabinet and dumps it to the inside bottom of the cabinet behind the dehumidifier.

 

A Ball Mill

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.

End Plugs

For a 3/4" end plug maker, use a hole just bigger than 3/4" and taper the entry a bit. This one is tapered about 20 degrees. You can make these from wood so don't let the metal work scare you.

Here is a chipboard blank cutter made from a sharpened bit of iron pipe - but, quite frankly, you can do just as well by cutting them out with scissors. For a 3/4" plug, use a 1 1/2" blank. You can also make paper circles by  sandwiching chipboard between two pieces of 1/4" plywood and drilling through the sandwich with a hole cutter. That makes nicely rounded blanks and you can make them a dozen or so at a time.

The plunger is a 3/4" stock that has been cut down at least 3/32". It should fall through the hole piece with about 1/16" at least on all sides. This allows the chipboard room to squish down. If you make it too tight, you will tear the chipboard.

Just push the plunger down and out the other end. It should be fairly tight going out the other end.

You can use the same ram to put the finished plugs into the tubes. Run a ring of white glue around the plug before you insert it or add some hot glue and you have a sealed end for your rocket!

 

To make other size end plugs, just follow the same idea as for the 3/4" version. Make the hole a bit larger and the plunger a bit smaller than the target tube. Taper the hole so the chipboard will push in without tearing.. it should be fairly tight with the ram in it though. You can see the rub marks from the ram on the plug in the picture above. Too tight and it tears and too loose and it looks a bit sloppy.

 

Time Fuse Punch

There are probably a million versions of time fuse punch thingies out there. The one in the picture will let you punch time fuse in a precise way. The screw in the back lets you precisely adjust the distance between the cross match holes.

The aluminum plug is a template. Once the first hole is punched, the plug is removed, the fuse is fed back into the device and a perfect 3 second fuse can be punched without adjusting or measuring anything. 

The hole for the fuse is 5/16" which allows a 1/4" time fuse a little leeway. The punch hole is 5/32 and the punch is 3/32 piano wire press fit into an aluminum sleeve. The screw feed is 1/4" threaded rod with a hex nut/split pin combo for easy adjustment.

Time Fuse Cutter

Here is a very simple and very accurate time fuse cutter. With this, you can cut to within the thread accuracy of the bolt attached to the tube. The cutter base is a Sears Handi-Cut which is also a very nice tool to have on your pyro bench.

Time Fuse Cutter

 

Dippers

An important addition to rocket or gerb making is a good dipper for compositions.  I like a dipper that consistently gives about 1/2 diameter pressings of the composition. 

The ones above have traveled a few miles but are very serviceable.  The larger ones are made from copper pipe caps - some sawn off shorter to get the right volume - and 45 (one cut down to give 1 gram loads) and 9 mm cartridge cases.  In general, a slightly longer handle is better than a shorter one. A couple of the above examples are shorties but I will probably replace the handles when it comes time to use them again. I like a length of about 6 to 6 1/2 inches so I don't get dirty dipping compositions. 

The handles are 5/32 brass for the cartridges with 3/8" hex stock on the end.  The brass is either soldered or screwed and epoxied into the ends. Epoxy or threads have to be used with the aluminum rods.   Epoxy works great so, if you are not a soldering type, you can still make a nice set with just a drill, hacksaw and file.  If you can't find hex stock without buying a lifetime supply, you can use 3/8" brass or aluminum rod - both of which are available at most local hobby centers.