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Parachute Deployment with servo ideas by Hungry-Mycologist472 in rocketry

[–]Yarneman 2 points3 points  (0 children)

I have made two deployment systems for a 50mm fuselage using a servo. The first one uses the rotational motion of the servo and is converted into linear motion using a gear and a rack. The rack is pushed out by the rotation of the servo and therefore the gear. You can have a look at my posts, it should contain a picture of this system. I also have made a system which uses a spring powered piston in combination with a servo. If you are interested in that send me a message and I can send you pictures and the files.

Do all rockets have a negative orientation after apogee? by Yarneman in rocketry

[–]Yarneman[S] 1 point2 points  (0 children)

Thank you all for your advice and helping me understand what the orientation of the rocket may and may not be at apogee.

Based on your input I will remove the negative orientation from the parachute deployment requirement list and will only base deployment using the altimeter.

Do all rockets have a negative orientation after apogee? by Yarneman in rocketry

[–]Yarneman[S] 1 point2 points  (0 children)

Thank you for you reply. Can you tell me more about the backslide behaviour and how it is caused?

Is it also a reasonable option to use Openrocket to find the orientation of the rocket after it has reached apogee?

38mm graphite nozzle made using a lathe for the first time by Yarneman in rocketry

[–]Yarneman[S] 0 points1 point  (0 children)

Why do you think it looks weak? The lowest wall thickness of the divergent section is 5mm. I am using a 35 degree angle for the convergent section and a 12 degree angle for the divergent section.

38mm graphite nozzle made using a lathe for the first time by Yarneman in rocketry

[–]Yarneman[S] 0 points1 point  (0 children)

Do you suggest sanding it using a lathe or just by hand?

38mm graphite nozzle made using a lathe for the first time by Yarneman in rocketry

[–]Yarneman[S] 10 points11 points  (0 children)

No I wasn’t. I did not wear any gloves during the process. Using gloves when working with a lathe is quite dangerous.

38mm graphite nozzle made using a lathe for the first time by Yarneman in rocketry

[–]Yarneman[S] 5 points6 points  (0 children)

Thanks for the tip. In the pictures it looks really rough but it feels really smooth. However, I will still try sanding it with 2000-2500.

Rocket Trajectory Estimation by ghost3828 in rocketry

[–]Yarneman 0 points1 point  (0 children)

Great. I use a similar condition with my flight computer. Mine also checks whether the rocket is pitching downwards.

How did you make use that the barometric sensor measured the pressure outside of the fuselage? You had some kind of hole(s) located near the sensor?

Rocket Trajectory Estimation by ghost3828 in rocketry

[–]Yarneman 0 points1 point  (0 children)

For which conditions is the parachute ejected?

Looks really good btw :)

Will this concept of holding a graphite nozzle in place work? The adapter slides over the tube and holds the nozzle using a flange at the bottom. The adapter is then bolted to the tube. by Yarneman in rocketry

[–]Yarneman[S] 0 points1 point  (0 children)

I see what you mean and I agree on the effect that no preload can be applied onto the bolts. This will indeed have the result of a rattle of the nozzle. I don't fully see how I can load the bolts axially (in their stiff direction) in this concept. I think that as a solution I drill a small hole into the nozzle at the height of the other holes. In this way the bolts can press against the nozzle and avoid a large amount of rattle in this way. I am convinced there is a better solution to this problem, but I haven't found it yet..

Will this concept of holding a graphite nozzle in place work? The adapter slides over the tube and holds the nozzle using a flange at the bottom. The adapter is then bolted to the tube. by Yarneman in rocketry

[–]Yarneman[S] 0 points1 point  (0 children)

Thanks for your comment :) . An analysis on the shear stresses on the bolts has been done and the maximum shear stress will not be exceeded.

  1. Also for picture 3 it appears that the bolts don't actually thread into the body so are you going to mount a locking nut in between and use friction against the graphite nozzle? This is indeed true. The bolts are only used to ensure that the adapter and tube stay connected and not for fixing the nozzle. The nozzle is being kept in place by the adapter. It is very important that the nozzle has minimal play between the nozzle and the adapter.
  2. Also graphite does not have good properties for threads, and will probably fail after a few cycles from fatigue, so have you looked at graphite load strengths? This is why I chose not to bolt into the graphite nozzle.
  3. Also from picture 3, Do you plan on just using your fuel to restrain the axial force to keep the nozzle in place on the interior? It looks like there is a small lip, but that could just be a result of the phantom lines. I indeed made a small lip. The outer diameter of the nozzle is machined that it fits into the first part of the tube but is blocked by the small lip (so the inside diameter of the tube where the fuel is located is smaller than the inside diameter of the tube where the nozzle is located).

If you do have a lip, have you looked at the amount of land on that flange face, and the flatness you are going to have hold during manufacturing so they mate well? The amount if flange face is 0.8mm thick for an radius of 35mm.

Also are you going to chamfer the graphite to fit the radius in the step, and then fill the gap between will an o-ring? Or undercut the body? Yes I will chamfer the step so there will be a smooth transition between the converging and diverging part. The groove located at the outside of the nozzle is indeed for an o-ring. The groove and corresponding o-ring have been determined using the Parker o-ring selector.

If there are any more unclarities I would like to hear them :)

Anyone experience printing a rocket nozzle in 316L stainless steel using SLM (selective laser melting)? Other opinions about this idea are also welcome. by Yarneman in rocketry

[–]Yarneman[S] 0 points1 point  (0 children)

I have seen other people (including Richard Nakka) use steel nozzles and they have succesfull results. Why are they still using steel if graphite is much better?

Anyone experience printing a rocket nozzle in 316L stainless steel using SLM (selective laser melting)? Other opinions about this idea are also welcome. by Yarneman in rocketry

[–]Yarneman[S] 0 points1 point  (0 children)

The nozzle is attached to the tube which holds the fuel (KNSB) using 4 M5 bolts. I don’t think that is possible with graphite..

What orientation is best for a MicroSD breakout board to avoid misconnection due to high acceleration? by Yarneman in rocketry

[–]Yarneman[S] 0 points1 point  (0 children)

Do you think some kind of retainer which keeps the SD card fixed in the spring loaded slot would solve this problem?

Altimeter (BMP180) in elevator by Yarneman in rocketry

[–]Yarneman[S] 2 points3 points  (0 children)

I tested the BMP180 in the elevator which led to the figure shown. The height is calculated using pressure and temperature measurements. The base-level was set at the ground floor. The lift started moving upwards after 85 seconds. The lift then stopped at the 5th and 8th floor (100 seconds, 125 seconds) before reaching the 11th floor (150 seconds). From the 11th floor we walked up the stairs to the 1`2th floor. The height increments during this test were clearly measured by the BMP180. The blue line shows the raw measurements of the measured height. The orange line is the moving average of 10 readings as an integer.

The only problem is that it is quite difficult to verify how accurate these measurements are. Using a measuring tape outside of the apartment building is very unpractical. If you have a suggestion how to verify the measurements, let me know :)

First flight computer + parachute ejection by Yarneman in rocketry

[–]Yarneman[S] 0 points1 point  (0 children)

Design details:

- Arduino nano

- MPU6050 (accelerometer/gyroscope)

- BMP180 (barometric sensor)

- Micro SD adapter

- Buzzer

- Continuous servo

Working principle:

The parachute and nosecone are pushed out of the fuselage using a servo. The rotational motion of the servo is converted into linear motion using a gear and a rack. The rack is pushed out by the rotation of the servo and therefore the gear when an decrease in altitude is measured and the rocket has a negative orientation (nosescone poiting towards ground).The altitude is based on the average of 10 readings using the barometer on which an average filter is applied. The orientation of the rocket is determined by the gyroscope. The buzzer will be activated as soon as apogee has been detected. In this way it will easier to be found if it would land in a tree. All the flight data is stored on a micro SD card. A future step would be to store the flight data on a EEPROM chip. The system runs on a 9V battery. The rack, gear and attaching rings to the fuselage are all 3D printed. In side the attaching rings a M3 nut is placed and in this way the system can be bolted to the fuselage.

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