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

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This entry was posted on Monday, September 8th, 2008 at 11:44 pm 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.

 
 

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