Saturday, May 30, 2009

Flight Testing and Launcher Construction Tutorial Part 10

Welcome back and a big "hello" to those of you who just discovered this journal! We're U.S. Water Rockets and we thank you for visiting. This week we have the latest in our ongoing series showing how to build a really nice cable tie launcher and we have another peek at some on-board video we took from our test flights last weekend.

On Saturday the weather was perfect, and we decided that it would be a great time to run some tests to collect some data for our secret "Project: 3000" Water Rocket. We wheeled out the launcher and the compressor and got everything set up by mid afternoon, and we were able to get out on the lake for the first time this year.

We had time to fly a total of three test flights using the new electronics and payload module we have been working on for Project: 3000. By the time we were set up the wind had picked up a bit, so we replaced our parachute with a small chute designed to get the rocket down faster before it has a chance to drift. This particular parachute has such a fast descent rate that it is not legal in the WRA2 Class A Rules, but since these were to be only test flights meant to test some new software we used low pressures and didn't bother to try to set any records.

Pictured below is a frame capture from the rocket take just before it reached an apogee of 1,000 feet (yes, the altimeter read 1,000 exactly!)
But enough talking about our test launches. We know the real reason you visit week after week, and it's not to read a bunch of boasting about some water rocket flights... we know you're really here to read the latest steps in our cable tie launcher construction tutorial! We shall not disappoint! Without further delay we will pick up where we left off last week and continue the build!

Our first task this week will be to mark the center line of the main base board along the end of the board so that we can properly center our legs. At this point we should still have the center line marking on the bottom of the board where we were measuring to locate the U-bolts. The easiest way to get the center onto the edges is to just continue that line with a ruler until we wrap around the edge of the board onto the ends. Mark both ends of the board now, using this technique. If you got anxious and started sanding your boards or erased the lines already because you were bored waiting for this installment then you will have to resort to measuring the halfway point along each end and marking it.

Once the center of the main base board is located and transcribed onto the ends of the main base board, you will do the same thing to locate the center of each leg board, marking along one of the narrow length edges just as you did before.

You can set the boards up with the center lines aligned and do a quick inspection to verify that everything lines up properly and there legs are evenly aligned. When you have verified your marks are in the correct place you can sand off the pencil lines on the flat faces of the boards and clean up the drilled areas with some sandpaper.
It's best to sand the base board now because the legs will be attached next and this will make sanding the board a lot harder. 
When you have finished cleaning up your boards and making them perfectly smooth and square, you will have three boards resembling the three boards we have pictured in the image below. Please make sure to leave the marks on the main base board's ends and the edges of the leg boards. We're not finished with those lines, so be sure you don't go crazy and sand them off.
Now we are ready to assemble the legs onto the main base board! There are countless methods of connecting these boards together. You can screw them together with wood screws, or you may choose to fasten them together with nails of some sort. These are the fastest and easiest methods, but we have found that they have problems. Nails and steel screws tend to rust, and that can leave a stain and look messy. Nails and screws are also prone to working loose under use.

Our preferred method of connecting the legs to the main base board is to use glue. Of course the best glue for all things water-rocket happens to be PL Premium Polyurethane! We put a small amount on each leg where it attaches, and put the main base board on top.

We assemble each of the legs onto the base the same way, using a clamp to hold the boards firmly together until the glue has cured. If you have clamps like ours with rubber pads to protect your work, you don't really need to take any special precautions. if, however, you have metal faced clamps then you will want to put some scraps of wood under each contact point to protect your wood from getting marred or dented by the clamps.
Before you fully tighten your clamps, make sure the center markings on each leg line up perfectly with the center line markings on the ends of the main base board. Also make sure to use a square or right angle of some form to check that the legs are at a perfect right angle to the main base board. Tap the wood with a block of wood or the palm of your hand until you have it perfectly lines up and tighten the clamp fully. Don't over-tighten!
After the glue has fully cured, you can remove the clamps and you will be nearly finished with this week's tasks. You may want to sand off the center lines and when you have finished beautifying your launcher you can then mount the plumbing loosely on the top of the launcher with the U-Bolts. You can sit back and admire your work and enjoy a job well done!
Come back next week. We hope to have some results of a new parachute test and some results from an effort we have been making to reduce the spinning our rocket has due to the high speed of it's ascent. If the weather holds out, we should have those results for you! In any case we will also put the finishing touches on the release mechanism for our launcher!

See you next week!

Saturday, May 23, 2009

Water Rocket Launcher Construction Tutorial: Part 9

Hello again, and welcome to the 9th part in our Water Rocket Launcher Build. This week we are going to star assembly of the PVC plumbing section of our water rocket launcher with the wood base. If you are just joining us, you should go back to part 1 of this tutorial and get caught up on the previous steps.

The first thing we need to do for this part of our project is to find the center line of the main body board of the base. The easiest way to do that is to measure the width of the board and divide by two and then mark this width near each end of the board and use a ruler or some other straight edge to draw a line the length of the board making the center line. This mark will insure that the launcher turns out perfectly symmetrical when finished. If you have a calibrated eyeball you can visually locate the center line of the board.
We will next need to find the center point of our main launcher body board, using the same method. We will measure the length of this board and then put a mark on the center line we just made at the point 1/2 of the length. This will give the exact center of the board and will insure the plumbing is mounted in a nice symmetric way.
We are now going to locate the U-Bolts which will hold the plumbing down onto the main body board. The location of these bolts is trivial math, because we too care in the earlier steps. Remember the length of the main PVC pipe at the bottom of the launcher? Well, we will be using that length now to precisely locate our U-Bolt holes.

Starting at the center point we marked on the base board, we will measure along the center line to locate the U-Bolt locations. The locations we want are exactly half the length of the PVC pipe which we recorded earlier. In our case we had an 8 inch long pipe, so we mark the board 4 inches from the center point on moth ends. We use our carpenter's square to make a line where each U-bolt will go. This line will be the center of the drilled holes for each U-Bolt, so we want to make the line as straight as possible and at a right angle to the board.
When finished making both locations for the U-Bolts, you can check your work by measuring the distance of each U-bolt from the end of the board closest to the spot. The two measurements should be equal. In out case our U-Bolts are each 3 inches from either end. If we were to place the 1/2"x3"x4' plank we want to use for the legs on either end of the board we can also test that the holes are not going to interfere with the mounting of the legs.
To locate the holes for the U-Bolts on the lines we just drew, we will simply measure the width of the U-Bolts and divide by 2. This will result in the distance from the Main body board center line we must mark out on each of the drill lines we just made.
We now can measure the distance for each side of the U-Bolt along the drill lines and mark the positions. These locations are the places where we will be drilling holes for our U-Bolts. Carefully mark each hole location on the drill line for each end of the board. This will produce the hole locations we need for the two U-Bolts.
Check your work by laying a U-Bolt on the board next to the drill marks we just made and verify that the drill marks really do line up with the tips of the threaded parts of the U-Bolt.
Now you are ready to drill out the holes for the U-bolts. Our U-Bolts have take 1/4" nuts, so we want to make sure we drill the holes that are large enough to accept the U-Bolts. We picked a 5/16" drill bit so that our holes will have 1/16" tolerance. If you think you will not be able to drill your holes with that much accuracy, you can pick a larger drill bit which will give you some additional tolerance.
Loosely install the U-Bolts in the holes, and make sure everything fits properly. It's a good idea to put everything together in this way to look for possible problems with clearance or alignment issues. If necessary, you can drill out the holes you just made a bit larger with the next larger size drill bit if you have overestimated the accuracy of your drilling skills.
That's all for this week! We're doing some test flights this weekend, so we have a lot of work to do preparing for the launches and analyzing the test data. We will be posting some launch results as well as a new build we have invented using an incredible new adhesive we discovered. We will also be finishing up the assembly of this launcher tutorial and showing how the design can be personalized. We have a lot of great things in store!

See you next week!

Saturday, May 16, 2009

Water Rocket Launcher Construction Tutorial: Part 8

Welcome Back, Water Rocket Enthusiasts!
In this installment of our Water Rocket launcher construction tutorial, we will begin the task of constructing a simple base for the launcher. There are many different materials we can use for the base and in this installment, we will be showing you how to make a basic wooden base for your launcher which closely resembles the now famous U.S. Water Rockets record setting L1 launcher.
To create this launcher, we will need to locate some wood and a few pieces of hardware. For our design, we chose to get some aspen planks from the local building supply box store. We chose aspen because it is low cost and reasonably hard. Plain pine can also be used, but we try to avoid it because it is a softer wood and therefore it can be more vulnerable to dings and scratches during use. Pine will be slightly less expensive, so the cost savings may be important, especially if you are building a large number of launchers for a scouting event.
Pictured below is the two aspen boards we purchased for this launcher. We purchased a 1/2"x3"x4' plank for the legs and an 1/2"x4"x3' plank for the body.
You can easily replace the aspen wood with some scrap building lumber if you wish, but you may have to compensate for different thickness lumber by using longer bolts or mounting hardware. If you wish, you can also substitute a hardwood like oak or maple in the design, which will be harder to work with but it will be much more resistant to damage while in use.
The next purchase needed for the launcher base is a pair of "U" Bolts which we will mount the PVC pipe launcher plumbing to the base with. We picked out a pair of U-bolts which are intended for use with 3/4" PVC pipe. The 3/4" pipe U-Bolts are just the right size to straddle the 1/2" PVC pipe fittings which we used on the launcher plumbing.
Tip: if you buy U-Bolts designed for 1/2" PVC pipe, they will only straddle the pipe itself and this will put the clamping force on the 1/2" PVC pipe which is somewhat flexible and will not hold as firmly as the rigid fittings. We recommend using the rigid fittings with the larger U-bolts to really clamp down the plumbing.
The first piece we will be making is the main body of the base. This piece will be the main structure which the other parts will attach. The length of the body must be created so that it is long enough to accommodate the legs of the launcher and still allow clearance for the mounting hardware. If you neglect to leave room for the hardware you will find yourself with a launcher you cannot assemble because the holes you made for the U-bolts are underneath the place the legs are attached.
The distance between the U-bolts is actually the same length as the PVC pipe at the bottom of the launcher plumbing. This length places the U-bolts right over the PVC fittings on either end of the pipe. In our case we have 8" for the distance. You can use any place on the fittings that places the U-bolts in a secure location and measure that distance to determine the U-bolt spacing. Make a note of the number.
We measured the width of our legs plus some extra spacing to allow for the nuts and mounting plate of the U-bolts. We simply set them in their rough positions and measured the space required. Since these dimensions are not critical, we rounded up to the nearest inch and came up with 3 inches of space required for each leg. We added the board length needed for 2 legs plus the length needed for the PVC tube which is 3"+3"+8", giving us 14" for our main body length. If this is too much detail work, you can just cut the legs to a reasonable size and then simply take the leg pieces and mock up the launcher in the final configuration and with the parts placed together like this you can make a mark on the main body board which will give a rough estimate of the correct length.
We marked out a 14" length of the 1/2"x4"x3' board for the main body of the base, and for our legs we used the 1/2"x3"x4' board. For the length of the legs, we picked an arbitrary length of 12". This length means one 4' board would yield four complete legs.
There is nothing special about the length of the legs. A rule of thumb would be to make sure it's not shorter than 50% of the main body length. This will insure the legs are wide enough to be stable.
Below, we mark out the 14" main body and 12" lengths of our leg boards and cut them.
Notice that we have used a small carpenter's square to insure that our lines are all at perfect 90 degree angles. We want to try and make our cuts as square as possible when we make them. This only serves to make the launcher look more professional and really isn't critical to the operation in any way. How hard you work on the cosmetics is entirely up to you. You may want to put the effort into making a neat cut now because we will be giving tips on how to customize and dress up the launcher in the future and a neat job here will pay off handsomely then.
We now have the two legs and the main body board cut and ready for more work. Bear in mind that these proportions and board sizes are not very critical, and we picked the dimensions we did for reasons of aesthetics as well as to try and optimize the number of launcher pieces we could make using standard board lengths found in our local store. Please feel free to tweak the sizes to whatever suits your needs.
Be sure and tune back in next week, where we begin the process of assembling the launcher base. The next steps will detail some nice shortcuts to getting a really professional and accurate looking final launcher.

Remember, the launcher is the one part of your water rocket arsenal which will usually be used for year after year. If you build it right, you will never have to replace it ever again. You will be able to spend your time building and flying rockets instead of constantly building new launchers. Look at the L1 launcher we use at U.S. Water Rockets... it's been in use since 2003! Most of it is unchanged since it was first used. We've made some upgrades and used steel pipe to hold more pressure, but it's the same launcher we first started with.

Another motivating point is that since this one piece of your equipment is going to be used for years and years, you should seriously consider making it as nice as you can because you're going to be using it for a long, long time.
See you next week!

Saturday, May 9, 2009

Water Rocket Launcher Construction Tutorial: Part 7

Welcome Water Rocket Enthusiasts!

In this part of our water rocket launcher construction tutorial, we will be showing you how to fabricate the cable tie clamp collar. This is one of the most important pieces of the launcher because the quality of this one piece will determine how easy or hard the rocket is to launch and how well the rocket will seal on the o-ring. Putting the extra effort into making this piece well will pay off handsomely in the long run. Do not cut corners on this part of the launcher and you will be glad you spent the time to get it right later.

The safety of the launcher depends heavily on this single part, so even if you don't care about the ease of use or the reliability of the o-ring seal, please put the effort into this piece to insure that your rocket is safe and secure on the launcher and will not launch by itself unexpectedly.

Step 1:
You will need to decide on the proper diameter for your clamp collar. It is important at this time that you sort out your rocket bottles and decide on a standard bottle to use with this launcher. If you examine your bottles closely, you will discover that some brands of soft-drinks use a different size flange on the neck of their bottles (see image below). The flange is used as the "handle" for the bottle, so it can be gripped by one hand and poured without slipping out of your grasp. Different bottling companies use different size flanges and you will need to decide which size you prefer to use because your launcher will be fitted for one size only.
Step 2:
The critical dimension for your clamp collar is the inside diameter. You will need to find a sturdy plastic tube with the appropriate diameter for your flange diameter. We found that a tube which is 1/8" to 1/10" larger than the flange diameter works extremely well. In our case we use the larger of our two bottle flanges and picked a 1.25" PVC pipe for the tube that will become the clamp collar for our launcher. If you see the image below, you can clearly discern that there is a 1/10" gap between the collar clamp and the flange. This gap will provide clearance for the cable ties to pass through but it is too narrow for the cable tie heads to pass through. This is the proper cable tie launcher setup.
Step 3:
We used a miter box to cut our PVC pipe to form our clamp collar. The length of the collar is not critical, so we arbitrarily chose a length of 1.5 inches purely for aesthetic reasons. The only real requirement to the length of the collar is to provide a bit of extension below the cable ties when the collar is mounted so that there is room to tie a cable to rope to remotely operate the launcher. The collar should be cut as square and straight as possible because it will seat against the rocket perfectly straight this way and that will make the collar slides smoothly when in use. A crooked collar can bind up and jam or move with more difficulty.
Step 4:
We will also take some time to clean up the edges of the collar with sandpaper. This makes it look more professional but really doesn't affect the operation of the launcher. In a later installment we will be showing how to personalize and dress up the launcher so we recommend cleaning up all the exposed edges now so you don't have to dismantle everything later and clean ut up.
In the image below, you can see the nice square edges of the clamp collar after we have finished sanding it. At this point we would like to mention that you may find that standard size pipes will not fit your particular nozzle size or flange size. This is particularly  true if you modify the bottles or add fairings or boat-tails. If you find you cannot use an off-the-shelf piece of PVC pipe, you may wish to check the supplier stock of PVC fittings. Sometimes you can find specialty fittings which have different inside diameter dimensions than the pipe itself. Female couplers are a good example of this, as their inside diameter is the outside diameter of the pipe itself. Some people use a section of FTC tube or a plastic pill bottle or film canister for the collar. Get creative and find out the best piece for your rocket!
Step 5:
You will next be adding some holes to the collar clamp so that a rope or cable can be attached and operated manually. Drill a hole completely through the collar at the exact center line of the tube. If the holes are not centered or uneven then the clamp will try and twist and could bind up during use. Make sure to drill holes sufficiently large enough to pass through the cable you will want to use.
Tip: If you are unsure of your ability to drill the holes straight on the first attempt, don't bother to sand the collar tube cut edges until after you have drilled the cable holes. This way if you screw up the holes, you haven't wasted time and effort sanding. Once you get the holes to your satisfaction you can then sand the collar. We simply sanded first because we have done this many times and have the experience for getting the holes straight on the first attempt.

Step 7:
Slide the collar down the top of the launch tube and over the cable ties. If necessary you can grip the ties with one hand and constrict them to allow the collar to pass over them. Slide of bottle down over the launch tube and push it down until it friction fits over the o-ring and seats against the washer on the base of the launch tube. If you have tightened the hose clamp on the bottom of the launcher you will want to loosen it up now so you can adjust it perfectly.
Step 8:
With the clamp loose you will move the group of cable ties as a unit up and down until they are overlapping the flange, Push the collar up so that it slides over the heads of the cable ties causing them to constrict around the flange. See the images below for reference and note how the heads of the cable ties overlap the flange and grab hold of it when the collar is pushed up. This is the secret how the launcher operates!
Step 9:
Press down on the bottle so that it is pressing firmly into the washer at the base of the launcher. The harder you press the better the secondary seal at the base washer will be. While keeping the pressure on the bottle, pull the cable ties assembly tightly down away from the flange as hard as you can pull and then tighten the hose clamp to secure the cable ties in this position. Be sure to leave enough room between the hose clamp and the bottom of the clamp collar so that it can move down all the way off the nozzle when it operates. The collar usually cannot pass over the clamp so you need to provide some distance for it to operate. You should try to get 0.75" to 1.0" between the top of the clamp collar and the bottom of the flange on the bottle when the clamp collar is fully retracted.
Step 10:
Practice operating the clamp a few times and see how it works. It should push all the way up against the rocket and sit neatly and squarely on the bottom of the bottle. It should slide easily down the cable ties and come to a stop against the hose clamp at the bottom with enough room for the cable ties to expand around the flange and allow the bottle to slide off the o-ring and up the launch tube. Push the rocket back onto the launch tube and allow the cable ties to surround the flange as the o-ring seals inside the neck. Push up firmly on the collar and notice the tension of the cable ties pulling taught against the flange causes the bottle to seat snugly against the washer at the base of the launch tube. That's perfect!
Next week we will begin detailing how to mount our launcher onto a portable base and give some tips and tricks how to create the base easily and inexpensively.

See you next week!

Saturday, May 2, 2009

Water Rocket Launcher Construction Tutorial: Part 6

Hello once again, water rocket enthusiasts! We're going to pick up where we left off last week and continue with the next phase of our water rocket launcher construction tutorial. When we left last time we have finished building the PVC plumbing for the launcher base and at this point we need to begin the assembly of the cable tie clamp mechanism.
The cable tie launcher design is a simple and inexpensive design which is attributed to a water rocket pioneer by the name of Ian Clark. We've taken idea and adapted it to our launcher design in a way which we describe below that should make it very easy for anyone to replicate.
The materials required for this installment of the launcher build tutorial are one roll of Duct Tape, a 1.5" diameter hose clamp, and a package of Cable Ties or Zip Ties.
 The first step is to unroll about 8 inches of Duct Tape and place it sticky side up on your work table. Duct Tape is also sometimes referred to as Gaffer's Tape, and frequently mistakenly referred to as "Duck" Tape. In fact, so many people have adopted this incorrect name that a tape manufacturer actually named themselves "Duck" so that they could have instant brand recognition. The Duct Tape pictured is actually Duck brand!
Start placing table ties on the sticky tape, making sure to keep their heads even and the spacing perfectly aligned so the ties are perfectly parallel. Be sure and place the ties onto the tape with the flat side down towards the glue on the tape.
Continue to place cable ties one after another until you have enough to wrap completely around the PVC 1/2" Female-Female coupler on the base tube of the launcher. We know from experience that 17 of the ties we use will make one perfectly even wrap around the PVC coupler. If you use larger or smaller cable ties then you may need to test fit and adjust the number of ties.
A good method is to put about 4 inches of ties onto the tape and then remove any extras when you go to mount them to the PVC pipes.
Here is a closeup of the ties laying flat side down. This is important because placing them the wrong way will cause the launcher to not work.
Slide a rocket or a bottle onto the launch tube and push it all the way down to the bottom where it will seat against the hose washer on the Female-Female coupler. Now, carefully take the Cable Tie mounted Duct Tape and place it on the Female-Female coupler as shown below. The heads of the cable ties should just overlap the bottle "grip" protruding from the neck of the bottle. Make sure to wrap the Duct Tape tightly and as evenly as possible.
Wrap the remaining tape around the cable ties and cut off the tape with a knife or scissors.
At this point, you should have a neatly wrapped group of cable ties. If you used a different size cable tie or a different diameter pipe for your launcher design, you can pull out any extra ties that you don't need, if there are more than the number on your tape to completely encircle the female-female coupler.
This is a good time to neaten up the alignment of the ties, if anything moved while you were assembling the tape to the launcher. A pair of pliars can be used to pull and twist the ties until they are back in perfect alignment.
We opened up an assortment of hose clamps and removed the one meant for 1.5" hose. This one will fit our cable ties perfectly without a not of excess clamp threads protruding. This is just a cosmetic issue and doesn't affect the operation of the launcher at all.
Put the hose clamp over the cable ties and temporarily tighten the clamp until the ties are secure and cannot move around. The cable ties should all be perfectly even now and securely held in place by the hose clamp.
The final step this week is to trim off the excess leads of the cable ties where they protrude from the bottom of the duct tape. This cleans up the look cosmetically, but also keeps the ends of the ties under control. If you leave the ties protruding, they can get tangled in the launcher pull string and create a problem at some point when you are launching.
Be sure and come back next week where we will show you how to use the cable ties to clamp the rocket to the launcher. We will explain how to size the launch collar and explain the pitfalls you may discover.

See you next week!