Hey Guys,

Following the success of our BigW "Giant Crayon", my wife and Son came home with a few (3) "Jumbo Crayons" from Sam's warehouse - they were half price ($5 each)... The Jumbo Crayon has the same diameter as the Giant Crayon, although 6" shorter. However, these can be joined together

Some images below of the "Giant Crayon"

G53-7FJ being assembled

Ready for launch & "Cleared the Tower"

Recovery


Some images below of the "Jumbo Crayon"

Normal use to store crayons !

I can see a Son & Father drag race looming....

Orange was key


Some design differences for the "Jumbo Crayon";
i) Intended for H128 and H180 motors. The Giant Crayon will goto a G64. Both will fly between 1,000 to 1,500 feet.
ii) Electronic deployment, the altimeter wil be mounted between Stages 2 and 3. I have since bought a 4th Jumbo Crayon as this will form the Avionics Bay and Joiner for stages 1 and 2.
iii) The rockets owner, backed by his Mum, insisted it be Painted orange - his favourite colour.
iv) Under $100 on the pad (less the motor and altimeter)

Will post a few pics through our build.

Regards,

Rob

Brilliant stuff guy's. Can't wait to see it all. Fantastic for our July public launch if you get it test launched by then !

Hi Ari,

The July launch could be a real possibility. I have a little travel coming up, although should have enough weekends to build this fellow.

We plan to gain our L1 Certification at the June launch and a H165R Redline in an orange "Jumbo Crayon" should give a good result.

We've had a late design change as Austin would like to have his own Avionics Bay ! I don't mind as this allows him to have more involvement in the pre-launch preparation rather than inserting a chute and motor and going. It also gives some differing configuration options, motor ejection, DD, etc.



To start, we'll use the MawD as the primary deployment controller, although with a 9" x 4" bay I have room to expand the Avionics suite

Hi Guys,

Well assembly began and were near completed, it's now time for the paint - Orange !

Here are a few build pics along the way;

Peeling of the paper off / Like an orange peel


Quick coat of Super Glue to give some surface hardness / 1 tube down, 3 to go


Avionics bay inner, outer and Joiner (this is the fourth Crayon) (ready to be reduced in diameter)


The 3 body tubes and the sectioned 4th


A few layers of fiberglass (Ash you’d be proud of us)


The finished product


Fin slots


All glued, awaiting the rear Centering ring


The lower body tube joiner


The completed Avionics bay


The three assembly’s (these are screwed together and become one -the nose cone is ejected for the chute)


Son, it is much taller !


The rocket will use one chute deployed via the MaWD. I opted to build this with a 38 MM MMT and Dual Deploy option if required - we'll see how it goes.

We wll keep you posted once we get started with the painting.

Hi Guys,

Little overdue for an update - work has been busy !

The rocket has moved into the "paint shop", decals are going on and a final coat of clear will see it done.

I have turned to the Avionics bay and now completed this, some images below.

Were on track for a 08 Aug launch. We plan to use either a H165R or H210R, according to Rocksim we should see an altituide of 760 or 1150 Ft respectively. I'll wait for the final weigh in though - Crayon's are heavy !

The Sled


I decided to go for an internal switch this time as it just lessens the 'loose' wires in an av-bay

Nice work!

Firstly very nice work and well documented, I've learnt a few things from reading this so thankyou.

Now if you excuse me i have what may seem like two stupid questions:

1. I'm assuming you use the old half C motor to put the BP from the reload in for the ejection charge then fire it with an ematch or similar. Question number 1 is how do you stop the BP coming out?

2. And on a related note, how do you stop damage from the motor burning out and up through where the ejection charge would sit normally, or is that not a problem

Thanks for your patience

Hi Knight,

Thanks for the feedback. No problems on the questions, don't worry, I pondered about these as well.

1. Very correct, this is half the length of a 'used' B or C motor. I use insulation wadding and tape to hold the E-Match and black powder in place. This system works very well for Dual Deployment where the lower charge is inverted for the launch so under maximum lift-off and gravitational force to seperate the E-Match and charge.

Here is an image showing the above;


Here is an image of a dis-charged ejection charge


2. Not a problem as I use the black powder that would normally sit on top of the delay (motor) in the ejection canister on top of the Av-Bay. The delay charge still burns as normal and provides good tracking smoke, although simply stops, as there is no Black power to ignite it does not burn through. In my other rocket where I use Elecronic deployment this has worked well and the top of the motor stays clean.

I do plan to purchase "plugged" fwd closures which are designed specifically for this purpose.

3. For info, we have another Crayon, the normal "Giant" size, and we launch it on G53 and G64. The weight of the Black powder supplied with these is approx 0.6 grams, we have found this is on the small side and on some deployments the Nose cone will pop and the chute will not be ejected, the drag of the Nose cone eventually does pull the chute out, although this gets the heart racing when your only 500 feet AGL. We have increased the charge size to 0.8 grams and found the chute is ejected each time.

I did a check on the 'volume' of the Giant Crayon chute bay and found that 0.6 gram is too light, 0.8 is also on the light side but works ok.

Hope it helps and regards,

Hi Rob, nice job

One thing that concerns me though is the limit switch you're using for the main power ie external pin pull power up.

Unless the spring preload is quite high, you may see a power loss during boost, but much more likely during the apogee ejection pulse.

Something to bear in mind.

CS

Ha Rob Its coming along nicely , look at all that room in the AV Bay makes life easy ha .... I do like that switch wont ever forget to turn the AV Bay on with it... let me know where you got it from.

Hey Strud,

Yeah the tension of the spring and mass of the swing arm concerned me. I considered these before hand and a few factors led me to believe for this application i'll be ok, these are;

1) The switch is mounted the way the images above depict so the initial launch force will be downward weighing the swing arm away from the micro and ensuring contact is not interrupted.

2) I haven't calculated decelleration velocity after motor burnout to Apogee, although don't believe these will be enough to force the swing arm up, contact the micro and de-power the altimeter.

3) I plan to make the first few launches on the Perfectflite MaWD which will be used for the main chute deployment only at apogee. The MaWD has a two (2) second "brownout" capability (loss of power protection) and reports all instances of powerloss when the altimeter is read.

Mitigating factors are I only require the MaWD to fire the main chute at Apogee, if the Apogee charge does impart a large force back into the rocket, at least the chute is out and i'll have the de-power event captured when I read the Altimeter.

4) The weight of the Nose Cone on this rocket is very light, so the Apogee charge should impart a limited (reduced) ejection force back into the rocket and the energy will be 'dis-chaged' out with the nosecone. As compared with a larger mass seperation such as a booster and Sustainer when I imagine both rocket components see a similar ejection force.

5) I plan to limit this rocket to H165R and H210R motors to start, so couple these with the lift-off weight of the rocket, should result in reasonably low launch forces.

6) Most importantly, I gave my Son one of those "Remove before flight" flags a little while ago, after seeing rockets over in Perth utilise these flags, he desperately wanted the Jumbo Crayon to have one....

If the above works ok, my next version will be less the swing arm to remove this as a potential failure source.

Regards,

Concerning the microswitch. Just making sure the microswitch is oriented correctly is not necessarily enough, speaking form personal experience.

I recently designed a spectrometer and had problems with the plasma not igniting during the startup sequence. After blaming many things I eventually (would have rather been working on other things!) found that the SOUND (!) of the plasma ignition was bouncing an interlock microswitch mechanism, causing contact bounce and the interlock to trip! Never would have believed it if I hadn't seen it myself. Going to a better (gold) microswitch and changes to the FPGA state machine has eliminated the problem (belt and braces approach). The original switch had all the appropriate approvals, so it wasn't a bargain switch to start with.

Maybe a cap across the contacts will help in your situation, or perhaps some other solution. Size depends on current draw and allowable dropout time, if there are dropouts with your setup.

Hi Over,

Thanks for your concern and feedback.

I even considered resonance from the motor setting up a potential harmonic through the lower body of the rocket into the Av-Bay. Additional, I was also worried about basic sturctural strength.

I extended the MMT upto and placed a centering ring in the center of the lower tube to provide some rigidity as well as a place for our drogue to sit if we go to dual deployment.

The Av-Bay, by design, I believe is rigid enough to withstand (to a degree) any vibration / resonance initiated from the motor burn. The H165R and H210R have a burn time of <1.5 Sec so any vibration / resonance from these should be contained.

As this micro does not have a steel roller on the end to add to the mass I am more comfortable with this configuration. We have a 'higher power' rocket and I plan to run two deployment systems, one of which we will revert back the trusty slide switch for redundancy.

Regards,

Your build looks great Rob. As to my comments on the microswitch I was extremely surprised to find it acting how it did. They key finding was it was the sound that caused the contact bounce (coupled to contacts via the body of the switch) and not due to the actuator type.

I hope it doesn't cause you the grief it caused me!

Hi Guys,

After re-consideration I've reverted back to a proven slide switch for the Deployment altimeter.

However, not to pass-up on the opportunity of trialling this switch configuration, I added a second altimeter to operate from this switch and will report back on our findings. Similar to the MawD, the Alt15K also has a 2 second 'brown out' feature and reporting function so I will know if the altimeter lost power at any stage through the flight.

The "Jumbo Crayon" has been painted, decals added and is ready to launch on the 12th Sept.