Rocket securement

[Steven88]

hello. What is the best way to secure my rocket for a ground test so that it doesn’t break a fin or do anything crazy when the powder fires? Do you lay it horizontally on your launch rail and brace the back end with pillows or simply just lay it out on the soft grass and go for it, or is there another preferred way? Rocket is made of plywood fins and 4” Loc paper tube with about 2 grams of charge in both caps for dual deploy. Thanks for the advice

 

[heada]

Ah! you want to ground test your dual deployment recovery setup! It wasn't clear at first to me. I test only 1 charge at a time. I do everything in the grass, not mounted on a rail. I aim it so that section of the rocket has a clear line of flight about 45 degrees off the ground. 2 grams should work just fine for a 4" rocket.

 

[Steve Shannon]

hello. What is the best way to secure my rocket for a ground test so that it doesn’t break a fin or do anything crazy when the powder fires? Do you lay it horizontally on your launch rail and brace the back end with pillows or simply just lay it out on the soft grass and go for it, or is there another preferred way? Rocket is made of plywood fins and 4” Loc paper tube with about 2 grams of charge in both caps for dual deploy. Thanks for the advice

In the air both halves move apart from each other at some relative velocity. If you block the bottom and prevent it from moving, the top will move faster relative to the earth than it would have if the bottom were unconstrained. That means it may be an imperfect representation of actual flight conditions. I doubt that’s too meaningful, but I know of one group of students whose rockets passed every ground test and had an almost perfect failure rate in the air. The only thing I can think of is that the difference was because the aft end was blocked.
Most people just lay the rocket on the ground on a blanket or tarp and let both halves move. If the fins cannot take that they probably won’t survive a landing.

 

[Bat-mite]

Most people just lay the rocket on the ground on a blanket or tarp and let both halves move. If the fins cannot take that they probably won’t survive a landing.

Agreed. Nothing in your ground tests should be stressing the construction more than a 20 fps landing under chute would.

 

[Steven88]

Ok thanks guys. Your advice is worth a million!

 

[grouch]

To effectively test it, you need to hang your rocket parallel to the ground from a string.

 

[Steven88]

Ok so balance it from a string? What is the advantage of that?

 

[grouch]

I'm kidding. Just providing more noise.

 

[David Schwantz]

I like to stick in the 6' feet of snow in my yard

 

[tfish]

here's some videos of how and how not to do it..

https://www.youtube.com/results?search_query=rocket+deployment+test

Tony

 

[tOD]

While we're on the subject of ground test I thought I'd pose a question of my own. I'm thinking of adjusting my charge sizes too compensate for different size chutes (larger). Is it possible to use a 6v Estes "Election Beam" launch controller direct wired to Pratt Hobbies ejection canisters to test? I was going to feed the canisters leads out through a vent hole in the e-bay, assemble the rocket for flight, and let 'er rip. Am I missing something? I tested the current charges using the vacuum cleaner method, which is somewhat of a PITA. The altimeter has worked fine on previous flights so I don't feel like I need to verify its function. Just trying to verify that the charge sizes are adequate.

 

[David Schwantz]

I just run the ematch leads out the vent hole and touch them to a AA battery.

 

[Bat-mite]

While we're on the subject of ground test I thought I'd pose a question of my own. I'm thinking of adjusting my charge sizes too compensate for different size chutes (larger). Is it possible to use a 6v Estes "Election Beam" launch controller direct wired to Pratt Hobbies ejection canisters to test? I was going to feed the canisters leads out through a vent hole in the e-bay, assemble the rocket for flight, and let 'er rip. Am I missing something? I tested the current charges using the vacuum cleaner method, which is somewhat of a PITA. The altimeter has worked fine on previous flights so I don't feel like I need to verify its function. Just trying to verify that the charge sizes are adequate.

I use Estes controllers with e-matches, but mine are the older ones. I don't think it takes much voltage to set off an e-match. In fact, with the Estes controllers, the continuity test lights the match.

 

[Nytrunner]

While we're on the subject of ground test I thought I'd pose a question of my own. I'm thinking of adjusting my charge sizes too compensate for different size chutes (larger). Is it possible to use a 6v Estes "Election Beam" launch controller direct wired to Pratt Hobbies ejection canisters to test? I was going to feed the canisters leads out through a vent hole in the e-bay, assemble the rocket for flight, and let 'er rip. Am I missing something? I tested the current charges using the vacuum cleaner method, which is somewhat of a PITA. The altimeter has worked fine on previous flights so I don't feel like I need to verify its function. Just trying to verify that the charge sizes are adequate.

I used to do vacuum testing, but switched over to manual initiation for the same reasons.

Good set of equipment testing:
- Vacuum test the altimeter with LEDs and resistor making sure they light in proper sequence. (optional for new altimeters that were tested by manufacturer, good idea for altimeters that survive a rough flight or event)
-Check resistance of ematch/initiator with meter
-Wire ematch to altimeter and listen for continuity check
-Manually test powder charges with ematch and launch controller

 

[tOD]

I used to do vacuum testing, but switched over to manual initiation for the same reasons.

Good set of equipment testing:
- Vacuum test the altimeter with LEDs and resistor making sure they light in proper sequence. (optional for new altimeters that were tested by manufacturer, good idea for altimeters that survive a rough flight or event)
-Check resistance of ematch/initiator with meter
-Wire ematch to altimeter and listen for continuity check
-Manually test powder charges with ematch and launch controller

That sounds like a good program. If I remember it's a 330 ohm resistor to limit current for an LED.
Weather looks good here tomorrow I'd like to check the charge size and continuity in the morning when I get home from work and hopefully fly on Sunday.

 

[tOD]

Ground test successful. Based on what I saw I'm increasing my charges 0.1g each. So it will be 1.7g drogue and 1.9g main in a 4" Super DX3.