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.

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This entry was posted on Friday, August 15th, 2008 at 10:12 am and is filed under Development. You can follow any responses to this entry through the RSS 2.0 feed. Both comments and pings are currently closed.

 
 

One Response to “Nosecone, Timer & Chute Side Deployment”

  1. sandra407 Says:

    Hi! I was surfing and found your blog post… nice! I love your blog. :) Cheers! Sandra. R.