Could Benefit from Input

[ThreeJsDad]

Hello Everyone, I am getting back into rocketry for a variety of reasons but one of the big ones is mental stimulation. Once upon a time I had my L2 and only flew completely scratch built stuff. I rolled or glassed my own tubes, turned my nose cones and laminated my fins and did all that crazy stuff.

I quit flying to design and build RC Sailplanes. This helped me develop some serious composite skills and add a curing oven, vacuum system and some very nice materials to my shop. I also developed some pretty solid soldering skills and some decent knowledge of Lipo batteries and charging systems for them.

Here is where I need some input. I am working on a parachute retention system for dual deployment. With a simply reliable system I can add DD to smaller rockets and move it from rocket to rocket in just a few minutes.

I have the mechanical part pretty well sorted due to some folks who worked on this before me. I simple canister that will slice through the retention band is very basic. I have considered using a servo based system but the tension I want to apply to my parachute package may be too much for the micro servos currently available.

I have a nice charging system worked out for a single cell Lipo where a simple plug in jack acts as the on and off switch. The cool thing is this is also a charging jack for the Lipo and it can be charged from a simple power bank via a micro USB cable.

The sticky bit is the altimeter. The only one I can find that will work well on a 1S Lipo is the Quark. If there are other options please let me know. If you have other thoughts please share as I have been out of rocketry for a while.

I do have a new bird almost done, it looks like it will be around 8oz before motor and it takes a 24mm motor, I think that will be fun.....

 

[tim cubbedge]

Altusmetrum & Raven altimeters all operate on 1S lipos.

 

[ThreeJsDad]

Thanks Tim, This is the help I need as I have been out of the loop for a while.

 

[PatD]

I have a nice charging system worked out for a single cell Lipo where a simple plug in jack acts as the on and off switch. The cool thing is this is also a charging jack for the Lipo and it can be charged from a simple power bank via a micro USB cable.

Welcome back to the zoo! Would you care to share the details on your charging system? I am putting together a Black Aero EggFinder case and am installing a charging plug for the lipo. I have a couple of thoughts but additional input is always welcome.
Thanks

 

[ebruce1361]

Sounds like we have similar projects in the works! I'm sure you have already heard of it, but if not there is a product that has been on the market for a while from Jolly Logic called the Chute Release. It's a mechanical clip mechanism that is activated by detecting barometric pressure increase during descent, and releases a rubber/elastic band that holds the parachute bundle closed until the Chute Release is opened. These go for about $120, and can fit into a BT60 airframe. Several of us have been tinkering with the idea of a cheaper home-brew chute release in this thread:

https://www.rocketryforum.com/threads/chute-release.154408/

The setup I am going for is an Eggtimer Quark activating an electronic cigarette lighter to burn an elastic band to release the parachute. If I can get the charging system worked out, this thing should be small enough to fit into a 24mm tube by itself.

Anyway, welcome back! We're glad to have you in the skies with us, and I await seeing what you come up with!

 

[ThreeJsDad]

You guys have definitely helped me so I will pitch some back. Space is a premium in my 1M sailplane so we went as far as soldering our servos right to the receiver.

For charging we use a tiny jack from Digikey. It is actually a tiny power jack like you might see on something that has batteries on board but can run on AC as well. When the plug is inserted the battery is connected directly to the plug. When the plug is removed the battery is connected to the object you want to power up. The jack has three contacts and the plug has two. I would not recommend trying the tiny head phone jack as some RC guys use. It is quite easy to ground things out when inserting the plug.

I will try to find the part numbers or I could even solder some up for folks who want them.

For a charger there is a small charger designed for 1S Lipos that uses a micro USB for a power source. The charger is roughly 1" square and .125" thick. I may have a couple left. I plug mine into an inexpensive power bank for charging.

I am aware of the commercial unit. I am not impressed for a couple of reasons.

It is too big in my opinion. I would like something that would work in a 24mm tube. Along this same vane I am designing mine so the control unit and the release mechanism are separate so I am not adding extra bulk to the chute. I plan to mount the control unit on the shock cord and run a set of wires to the release mechanism.

I am impressed though with how simple it is to set up and charging it is just as simple.

I am actually chatting with Chris about possibly using a servo based system. The servo would be right on the chute bundle with thin servo wires running to the altimeter.

My goal is re-usable, re-chargeable, stupid simple, reliable, and durable.

 

[ebruce1361]

You're wanting to fit a chute release device in a 24mm tube along with the parachute? Now, that's ambitious! Keep us posted on progress because I would love to see this setup work!

 

[ThreeJsDad]

That would be sweet for high flying MPR stuff but in reality even a 29mm system would be nice.

I took a look at the older thread on this subject and it has some great ideas. I want my system to run on 1S though for the ease of charging. A 2S battery requires a balancing charger.

I am going to play around with some servo driven release mechanisms. The key will be to be able to have high tension on the "package" but have low tension on the trigger mechanism.

 

[ThreeJsDad]

I looked a little closer and I am not sure 24mm is possible simply due to the size of the altimeters. If we did a transmitter initiated deployment 24mm is possible but I will be happy with 29mm for now.

 

[dhbarr]

Smallest 2-event altimeter I know is the Bear AltiDuo SMT.

Pic for scale:

View attachment 304645

 

[blackjack2564]

I run my stratlogger cf and RRC2 both with 1 cell lips. they cost about 50.00 for either