Posts Tagged ‘recovery’

 

Dual Deploy Nose Cone – Part 2

Rethink
After building the SSPPNC and thinking about the servicing problems I was facing, I came to the realization that this SSPPNC didnt really fit with our philosophy of a modular approach to water rocket construction. Rather than building a SSPPNC that could deploy both chutes we decided to leave the PPNC as it was and build a drogue chute module. The idea being that this module could be added or removed from the rocket based on the requirement of the launch.

Bottle Shrinking
One problem we have found when fitting and aligning the parts of the rocket was the fact that the diameter of the PPNC is smaller than the bottom section of the PET bottle, not by much but enough to have it not fit on straight and sometimes having to be realigned after taping.

We decided to use George’s method (http://www.aircommand.com) of shrinking the bottom of the bottle. This ensured the PPNC slides over the bottom of the bottle underneath it in the rocket. See Georges video about the 4:00 minute mark for how to shrink a bottle. We didnt quite have the water boiling but Im guessing around 80 degrees C. We immersed the bottom of the bottle a few times until we had it the size we wanted.

Here is a pic of 2 x 1.25L bottles. The bottle on the left is a standard bottle, the bottle on the right has had the bottom shrunk slightly.

Shrunken bottom of 1.25L bottle (right)

Shrunken bottom of 1.25L bottle (right)

Although they look very similar there is a big difference when connecting the modules together. This is best shown with a video. So here one is. In this video I am connecting the new drogue parachute module to one of the rockets pressure bottles. First connecting to one I have shrunk, then to an untouched bottle. You can see the difference.

Drogue Parachute Module
In part one of this article we showed the nosecone structure for the drogue deployment module. As we have now decided to make a drogue module that can be added or removed from a rocket, we needed an enclosure that would allow this. The obvious choice was to use the bottom section of a shrunken bottle.  This will allow the PPNC module to fit over the top of it, it also allows this module to fit over another module (a future payload module) or the bottom of the pressure bottles.

Drogue Chute Module

Drogue Chute Module

We have used bubble wrap as fill in the top section (its lighter than sponge), the size of the structure and door opening is smaller, to take smaller chutes, but the tomy timer configuration and air flap is the same as the PPNC module

Putting The Modules Together

The modular method we have used to shrink the bottom section of the bottles allows the modules to be easily put together to form the rocket combination we desire. Here is a video of the PPNC module, drogue module and out pressure bottle being assembled. For liftoff they are taped together. This method makes module alignment much easier.

I have weighed the modules and shown it here for those interested. You can always get to this from the Menu section of the site then under categories then weights.

Dual Deployment
Here is a test run of both chutes deploying, the modules are connected to H2. We will do a bit more testing prior to launching this configuration, however so far so good. The air flaps detect launch and will sit closer to the rocket body during acceleration

Posted by on October 7th, 2008 Comments Off

Dual Deploy Nose Cone – Part 1

The last week we have been busy building a PPNC nosecone that will deploy 2 parachutes using tomy timers. The idea is to have a smaller drogue chute deploy at apogee and the main chute when its closer to the ground.

Drogue Chutes
We have used some simulators to try to work out how big to make the drogue chute, but ended up with mixed results. So we decided to make 2 drogue chutes and see how they test. These were 10cm in diameter and 15cm in diameter respectively. We used the same procedure as we did when making the main chute except reduced the number of chute lines to 4 and 6.

Drogue Chutes

Drogue Chutes

On initial testing, the 10cm chute is just too small and doesn’t get enough air into it . The 15cm chute might be ok, but the hole in the middle is too big. We can just sew a patch over it and give it a further test. Worse case a 20cm one may be called for.

Longer PPNC Nosecone
The two chutes and release systems wont quite fit in a standard 1.25L body section we make the PPNC nosecones out of, so we have made a super sized PPNC (SSPPNC) by adding an additional 1.25L body section.

Super Sized PPNC Nosecone

Super Sized PPNC Nosecone

The bottom section was from a different 1.25L bottle manufacturer and is just used for the mockup, we will use a P&N bottle for the final nosecone.

There join is not perfect and the nosecone structure gets stuck a little. We will need to be more careful when fitting the final bottom bottle as we need to be able to get the nosecone structure in and out for servicing.

Nosecone Structure
The nosecone structure needs to have 2 elastic band powered pressure plates to push out the chutes. To accommodate this we have built another smaller structure as well as a section to join the two chute deployment sections. We needed this to have enough space between the two so they was less chance of lines being caught up.

Here is the drogue deployment structure (pressure plate not fitted yet)

Drogue chute deployment structure

Drogue chute deployment structure

You can see we use wire to join the sections together, this makes it very strong which allows for tighter elastic bands which help throw the chute away from the rocket body better, as well as having a better chance of survival during a crash.

Here is the structure how it will fit inside the super sized PPNC.

PPNC Dual Deploy Structure

PPNC Dual Deploy Structure

From the top down the pieces are

  • Pilot capsule – its main use is to ensure the main parachute deployment structure is below the curved section of the top of the nosecone. This helps the door close better if its flush against the side.
  • Main Parachute deployment section and pressure plate
  • Extension section – This is to position the drogue chute deployment structure down below the join of the two bottles in the nosecone. Having the door across the join is not a good idea
  • Drogue Chute deployment section (note the pressure plate is not fitted yet)

The two doors will be on opposite sides of the SSPPNC. The idea for putting the drogue lower than the main chute is so that when the drogue deploys it will be connected to a lower part of the rocket nearer the CP than the CG, the rocket will orient itself with the nosecone down position and drogue trailing behind. This gives a lot of room for the main to deploy and open being furthest away from the deployed drogue. The main chute will be connected close to the CG so that the main and drogue dont tangle .. well thats the theory anyway :)

Tomy Timers
We received our order of 5 tomy timers yesterday which is good. We also managed to destroy the one we had when glueing it to the structure, too much glue and we managed to glue up the gears … Lucky we ordered a couple of extras

The work for the rest of the week will be assembling the nosecone, testing the dual timer and getting some calibration numbers on the timers.

We will report part 2 later in the week

Posted by on October 1st, 2008 Comments Off

Nosecone Mk II

After our recent parachute deploy failure it was back to the drawing board for the ping pong nose cone (PPNC)  and side parachute deploy. Having built the first version there were a number of things I wanted to fix. These were

  • The placement on the nosecone of the timer
  • Want to use a single rubber band to not wind past the timer – this reduces the chance of being caught up on the timer itself.
  • The size of the door probably needs to be a little smaller and lower (dont want it near the pointier point of the nosecone, this makes the door not close properly
  • The vertical height of the nosecone support structure may be too high based on our parachute size.

The PPNC shell and support structure were largely based on our original design

Timer Placement
This is probably the most important thing for the new nosecone. We think the root cause of the parachute deploy failure was that the elastic band when it wrapped around the nosecone got caught up on the timer itself and wouldn’t allow the door to open. Nosecone Mk II has the timer located just before the door hinges. This gives the elastic band enough space to be stretched but not too much that it will wrap back past itself or the door. Hard to explain , so here is a pic.
Door hinge and timer location

Door hinge and timer location

The door has 2 wire hinges. The door is made out of the same diameter bottle, just put on backwards, so that the natural curve of the bottle will fling the door open by itself. The parachute deployment plate is just visible on the right with its two elastic bands that eject the parachute. The timer is to the left mounted on the side of the nosecone support structure. A hole is drilled in the side of the bottle to allow the handle of the timer to extend beyond the rockets diameter.

The little green guy is our fearless pilot. The tape is on the inside to ensure the nosecone structure doesn’t snag on the hinges when it is removed.

Nosecone Door

Nosecone Door

Above you can see the door in the open position, notice how it curves the opposite way when open, also the one elastic band on the door which is enough to keep it closed and connects to the timer.

We added an extra section at the top of the nosecone support structure, this was to keep the top of the door below the curve in the nosecone (although it doubles as a pilots cockpit), this will help keep the door closed properly as it will sit flatter against the side of the nosecone. The size also fits our parachute better, not too loose, not too tight.

New Timer

This nosecone had a proper Tomy timer, sent to me by Trevor in Cairns (thanks again). These are available from Toy stores. I will have to find them here in sydney. This is what the packaging looks like. They are about $3 each.

Tomy Timer Packaging - Front

Tomy Timer Packaging - Front

Tomy Tomer Packaging - Back

Tomy Timer Packaging - Back

The timer is much better than the previous fish swimmer in nosecone Mk I, as it has a built in regulator. This means that when you cut the wheels off you don’t need to put any weight back on it to stop it from just unwinding quickly.
Here is the timer ready to go into the nosecone. The wheel you can see on the front was cut off.
Tomy Timer ready for installation to nosecone
Tomy Timer ready for installation to nosecone
Ready to Fly
Here is the final configuration, parachute is packed, elastic band is connected to the timer (far left), the speed flap (launch detect) is attached and the nosecone is attached to the top of the pressure bottles.
Ready to Fly

Ready to Fly

Also our fearless pilot is strapped in and readyfor launch

Posted by on September 8th, 2008 Comments Off

Nosecone, Timer & Chute Side Deployment

Standardizing Bottles
We have decided that we need a parachute system for our water rockets now that we are getting higher apogee’s and looking to build multi-bottle rockets.

We will also look to standardize on the 1.25L soft drink type bottles instead of the 1.5 Liptons Tea bottles we have been using as we search for higher pressures. This seems to be the accepted norm as these bottles rupture at a much higher pressure. We are using bottles from a drink bottler called P&N Beverages here in Australia. They are available in Woolworths and Coles supermarkets. They have a range of 1.25L, 1.5L and 2.0L bottles.

P&N 1.5L bottles

P&N 1.5L bottles

Nosecone
The nosecone is based on a 1.25L bottle and follows the initial stages of George from Aircommand’s Parachute side deployment design, once again thanks George.

We used a 1.25L bottle and a half cut table tennis ball for the outer shell, we also constructed the internal support structure to hold our timer and ejection plate similar to Georges. The structure or holder was made from corrugated plastic, this was a donated real estate “For Sale” sign that had served its purpose.

Ccorrugated plastic Sheet

Corrugated plastic Sheet

The corrugated plastic we have is 3mm thick, we have a lot left over to make some fins for our next rocket as well as more nosecone structures.

Timer
Getting a timer was a bit more difficult than expected. After looking through many toy shops I came across these fish swimmers in a $2 shop .. for $1 .. go figure !

Wind Up swimmer

Wind Up swimmer

The wind up section is a coil of flat wire, some gears and a small output shaft. When it was in the swimmer winding it all the way up took 5-6 seconds to fully unwind. Enough for my initial requirements.

What I didnt expect was that once the load (tail) was taken off the timer it took less than half a second to unwind. This was due to the fact that there was no load against the spring.  A suggestion by Pat LeBlanc on the Yahoogroup water rocket group, was to put some load back by means of gluing a bolt or similar onto it. This was a little tricky but eventually I got it to stick and here is the result.

Timer in nosecone + weighted load

Timer in nosecone + weighted load

The pic shows the timer been mounted on a couple of small sections of corrugated plastic to the support structure in the nosecone,  in this picture its laying on its side (up down is left to right respectively).

Unfortunately the output shaft is offset to a small flat section which is about 3mm across which I imagine was deliberate to shake the fish around in the water. What it means is that it does shake around a bit, I will have to see how badly this effects things once I fly it.

Here is a pic in the upright position

timer in upright orientation

timer in upright orientation

You can see to the left the elastic bands and the ejection plate for the parachute, I put some sponge behind it to give it an extra push.

Speed Flap
I have included a speed flap to release the timer made from corrugated plastic (I only cut one side of it to make a hinge) The pin from the timer just pierces the plastic to hold it there. I was hoping blowing on it would be enough to release it but I may have to either make a bigger speed flap or put something on the launcher for it to hit as it launches to ensure this releases the timer. Im still working on getting this right.

Getting the small piece of metal to stay on the handle required me drilling some small holes in it and winding it around the handle, gluing it wasn’t strong enough when connected to the elastic band under load.

winder close up

winder close up and speed flap below

Deployment Door
The area around where the pressure plate for the chute deployment is located was cut out of the shell and a bigger door was cut from another bottle of the same type/diameter. To assist in the door opening it was pu ton in the opposite orientation to the bottle, ie: when released the curve in the bottle wanted to open the door.

This was initially glued in place but this wasnt strong enough, so where the door overlaps the nosecone 4 x bent pieces of wire were used to hold it in place.

Door wired on

Door wired on

The door is slightly bigger than the opening and has a flap with a hole drilled in it to attach the elastic bands. Seen below

Door and elastic band attachment

Door and elastic band attachment

The flap wraps around the bottle (missing the timer and the speed flap. Here is a picture of the door open and the pressure plate for the chute release visible.

Door open and pressure plate chute release visible

Door open and pressure plate chute release visible

Ive added some sponge to the space above the structure in case it doesnt deploy to try to mitigate some of the force of the crash down. Here is a pic of the door closed and the elastic band wrapped around the nosecone

Nosecone - Door closed

Nosecone - Door closed

Test Timer and Door

Here is a video testing the nosecone. I am in the process of making the parachute.

Posted by on August 15th, 2008 1 Comment