Not Earth-shaking, but maybe useful for many different applications such as actuating hatches, deploying legs, recovery deployment, stabilization. I'm creating a low pressure (10 psi) miniature pneumatic system to retract and extend legs on a model-sized rocket. The 1/4" pneumatic actuator produces about 0.25 Kg force at 10 psi. Using inexpensive air solenoids that operate at 5 VDC. Here's a 5 minute video that shows my first try at developing a low mass system.
Low Pressure Pneumatics
- Thread starter Richard Dierking
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Nytrunner
Pop lugs, not drugs
That's neat!
If you're stuck at home, might as well innovate!
How is it triggered during flight, and how heavy is the power source/controller?
If you're stuck at home, might as well innovate!
How is it triggered during flight, and how heavy is the power source/controller?
Huntsville Alabama! Going OT here, but I was planning to go to Marshall SFC this year. Still doing it if possible. So, what's the tourist stuff like? Always good looking forward to fun trips.
I think I'll use a Adafruit Metro Mini and a simple vibration sensor. I know some basic programming for Arduino and the actuators are 5 volt 300 mA. I'll use a small capacity 2 cell LiPo and assure it's enough power during testing. Using the Metro, I'll be able to control the timing and length of time the actuators will be pressurized. For this first test, I used 2 position, 3 way solenoids and plugged the exhaust port. I ordered some normally open gas control solenoids for the next test, so just inlet and outlet. Cost $2 each. They are 16 grams. At 10 psi I'm overspec because the rating is 350 mmHg (6.8 psi). So, I'll have to see how they hold up.
This first rocket also will use the BPS Space TVC kit. I'm looking forward to an "interesting" flight.
I think I'll use a Adafruit Metro Mini and a simple vibration sensor. I know some basic programming for Arduino and the actuators are 5 volt 300 mA. I'll use a small capacity 2 cell LiPo and assure it's enough power during testing. Using the Metro, I'll be able to control the timing and length of time the actuators will be pressurized. For this first test, I used 2 position, 3 way solenoids and plugged the exhaust port. I ordered some normally open gas control solenoids for the next test, so just inlet and outlet. Cost $2 each. They are 16 grams. At 10 psi I'm overspec because the rating is 350 mmHg (6.8 psi). So, I'll have to see how they hold up.
This first rocket also will use the BPS Space TVC kit. I'm looking forward to an "interesting" flight.
Nytrunner
Pop lugs, not drugs
The US Space and Rocket Center is a must. Home of Space Camp, "Visitor center for Marshal Spaceflight Center", Von Braun helped found it, it's got TWO Saturn V's (fake one standing up, real one lying down split apart) and the Pathfinder boilerplate shuttlestack.
Marshall Spaceflight Center itself is trickier. It resides on Army Redstone Arsenal and you need to take the bus tour from the USSRC (above). The route changes depending on program activity on base, so ask when you're there.
There's a veteran's Memorial museum, Bridge Street Plaza, Big Spring park in downtown, oh and the Huntsville Havoc hockey team if you're there in season.
Monte Sano, Rainbow Mountain, and the Botanical gardens are nice outdoor places to go.
There's a drive through safari too I've heard
And if you're here on the night of the 1st Thursday of the month, stop by a HARA meeting and see rocket folks! (when coronavirus isn't in full bloom of course)
Thank you! I'll time my visit to attend the meeting.
I'm working on the 2nd version of the leg set up now and will post info in a couple days.
I'm working on the 2nd version of the leg set up now and will post info in a couple days.
Robart makes a restrictor for airlines.
https://robart.com/collections/air-systems-components-air-couplers/products/air-line-restrictors
These keep your cylinder from slamming open and closed.
https://robart.com/collections/air-systems-components-air-couplers/products/air-line-restrictors
These keep your cylinder from slamming open and closed.
Thank you David! I was considering making something like this myself. I tried to throttle a plastic aquarium valve and it didn't work. Obtaining these restrictors saves me some work. Ordered these and some quick disconnects.
I've been ordering tubing and fittings from US Plastics. Their prices are good.
Now, wish I could find an inexpensive low pressure solenoid that would go up to say 25 psi. I have the cheap ones I purchased through eBay and some ones that I obtained through my local recycler. These go up to about 100 psi and about the same mass but these would be expensive to purchase new. I would like to have good sources for everything I'm making so people could make their own set-up.
I've been ordering tubing and fittings from US Plastics. Their prices are good.
Now, wish I could find an inexpensive low pressure solenoid that would go up to say 25 psi. I have the cheap ones I purchased through eBay and some ones that I obtained through my local recycler. These go up to about 100 psi and about the same mass but these would be expensive to purchase new. I would like to have good sources for everything I'm making so people could make their own set-up.
There a lot of them that are used in the RC planes. Try BVM Jets, Dreamworks RC. They can be servo or electric controlled. Also Hobby King is a source. But they are cheap and sometimes you DO get what you pay for.
I dug out a couple of things so that you could get an idea of the size of them. Cylinders, valves, fill valves, multi connectors, gauge.
I dug out a couple of things so that you could get an idea of the size of them. Cylinders, valves, fill valves, multi connectors, gauge.
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Thanks again for the info David. I ordered some supplies manufactured by Robert that's usually for RC airplane landing gear. The small tank, air restrictor, and fill valve help with my project. I also ordered some small size pneumatic cylinders through eBay that haven't arrived yet. Just curious how well they will work.
With this 2nd version, I'm now ready to start making the 4 legs I'll need for the rocket. I still need to improve my pneumatic cylinder a bit to reduce leakage when it's pressurized. I'll probably add an additional o-ring.
Here's a video showing the operation of the 2nd version:
With this 2nd version, I'm now ready to start making the 4 legs I'll need for the rocket. I still need to improve my pneumatic cylinder a bit to reduce leakage when it's pressurized. I'll probably add an additional o-ring.
Here's a video showing the operation of the 2nd version:
An update from the last post a couple months ago. Version 2 had problems. I had made my own actuating cylinders and they leaked even after adding an o-ring. The system used a sliding strut which was difficult to adjust in the slotted track and keep clean. I used various lubricants and all accumulated some debris. I could imagine what would happen on a dusty lakebed or sand of the Mojave desert; just didn't have confidence in the system.
So, I switched to a commercial cylinder with 4 mm bore, 20 mm throw, and spring retract. Also, increased the supply pressure to 50 to 60 psi. I tested the air solenoids shown previously and didn't find any issues at the higher pressure. The cylinder became a strut that pivoted into place when extended. Since the cylinder is spring retract, I didn't have to add a spring to the system. However, the legs will now be normally retracted not extended. But, the air cylinders don't leak.
Version 3 is easier to create and a lot more reliable. The following video is just under 3 minutes. Once I get the TVC mount in the rocket validated, I'll test the pneumatic system in the rocket and continue with building the rocket with the legs.
I always appreciate comments and suggestions.
So, I switched to a commercial cylinder with 4 mm bore, 20 mm throw, and spring retract. Also, increased the supply pressure to 50 to 60 psi. I tested the air solenoids shown previously and didn't find any issues at the higher pressure. The cylinder became a strut that pivoted into place when extended. Since the cylinder is spring retract, I didn't have to add a spring to the system. However, the legs will now be normally retracted not extended. But, the air cylinders don't leak.
Thanks again David for letting me know about these materials. It helped a lot.
Version 3 is easier to create and a lot more reliable. The following video is just under 3 minutes. Once I get the TVC mount in the rocket validated, I'll test the pneumatic system in the rocket and continue with building the rocket with the legs.
I always appreciate comments and suggestions.
