RRC3 and PET2+ Dilemma

[joey]

Hey all,

New member looking for some advice on staging electronics. I have had considerable help from Wayco in another thread on RRC3. However, I am still looking for ways to use my PET2+, since my RRC3 was initially purchased for dual deployment and I do not have the aux modules at hand.

Here are my questions:
1. I understand it is dangerous to rely air start solely on timers, but is there anyway that I could still use my PET2+ for staging? After all, the unit is designed for staging.

2. Is there anyway that I could trick an altimeter like RRC3 to trigger the main chute on the way up? Essentially making an altitude dependent air start.

3. I am also trying to think of ways to test my electronics. I am using a vacuum pump to test my altimeter, but I am not sure if that is the best way. And for the PET2+ timer, it requires at least 2G acceleration to trigger and I don't have a good way of accomplishing it yet.

4. I am also trying to figure out the event timing for stage separation and second stage ignition. What is a good time for stage separation BP firing and when should the sustainer motor ignitor be lighted?

 

[Wayco]

Hey all,

New member looking for some advice on staging electronics. I have had considerable help from Wayco in another thread on RRC3. However, I am still looking for ways to use my PET2+, since my RRC3 was initially purchased for dual deployment and I do not have the aux modules at hand.

Here are my questions:
1. I understand it is dangerous to rely air start solely on timers, but is there anyway that I could still use my PET2+ for staging? After all, the unit is designed for staging.

2. Is there anyway that I could trick an altimeter like RRC3 to trigger the main chute on the way up? Essentially making an altitude dependent air start.

3. I am also trying to think of ways to test my electronics. I am using a vacuum pump to test my altimeter, but I am not sure if that is the best way. And for the PET2+ timer, it requires at least 2G acceleration to trigger and I don't have a good way of accomplishing it yet.

4. I am also trying to figure out the event timing for stage separation and second stage ignition. What is a good time for stage separation BP firing and when should the sustainer motor ignitor be lighted?

JOEY. Would you please go to Missleworks.com and read the operators manual on the RRC-3? You don't need an aux. module to do an airstart. There is an aux. output right on the altimeter.

The PET2 timer is designed for AIRSTARTS. Starting motors while the rocket is in the air is not the same as staging the sustainer motor on a two stage rocket.

You don't need to "trick" your RRC-3 to fire an ejection charge for the main on the way up, use your PET2 for that. That is assuming you are doing this for the booster main....

Stage separation should occur VERY shortly after the booster motor burns out. (MECO) You should also download the operating manual on the PET2, and program it accordingly.

Starting the sustainer motor should occur VERY shortly (no more than a second) after separation. When you get more experience with two stage sequencing, you can add time to this, but don't do it until you have a few good flights under your belt.

Jim Amos, the owner of Missleworks is a great source for help with programming your PET2 and RRC-3. I have had many conversations with him and he can be very helpful with programming his devices.

 

[blackjack2564]

Hey all,

New member looking for some advice on staging electronics. I have had considerable help from Wayco in another thread on RRC3. However, I am still looking for ways to use my PET2+, since my RRC3 was initially purchased for dual deployment and I do not have the aux modules at hand.

Here are my questions:
1. I understand it is dangerous to rely air start solely on timers, but is there anyway that I could still use my PET2+ for staging? After all, the unit is designed for staging.

2. Is there anyway that I could trick an altimeter like RRC3 to trigger the main chute on the way up? Essentially making an altitude dependent air start.

3. I am also trying to think of ways to test my electronics. I am using a vacuum pump to test my altimeter, but I am not sure if that is the best way. And for the PET2+ timer, it requires at least 2G acceleration to trigger and I don't have a good way of accomplishing it yet.

4. I am also trying to figure out the event timing for stage separation and second stage ignition. What is a good time for stage separation BP firing and when should the sustainer motor ignitor be lighted?

First you can program the RRC3# with the buttons and switches....I have the dongle which is by far the simplest method to do all this. Spring 25 bucks , download the free flight viewer program & get it over with, or call Jim Amos and he will tell you how to do it.The unit will do everything you are describing.

1. Yes it's dangerous, you just answered your own question, don't do it.
....if the booster doesn't fly straight, the timer will fire the sustainer no matter WHAT. It could be spinning around, pointed at a car, the flight line, people,the booster motor could burp on the rail, sustainer land on ground...it will still fire.There is NO way to stop [ most] timers, once triggered.

Simply put NO , YOU CANNOT USE A TIMER FOR STAGING...PERIOD. [at least at a Tripoli certified launch] against the rules.

Well no where Tripoli or I fly allows it.
I'm sure there is somewhere you can.
Yes years ago , timers were an acceptable method for staging.
Years ago there were no seat-belts.
Things change, safety develops.
It is no longer considered viable for staging.

2.No.
Blowing chute going up is so wrong, in too many ways.
Learn to use electronics properly. Read manual or CALL Jim Amos and let him explain how to use the features he has built into the unit for safe operation.

You CAN set the RRC3 to trigger the "altitude dependent" safety feature. You just set the comparator trigger: fire sustainer only if booster reaches "X" altitude. Like it must be at least 800ft or more for sustainer ignition. You can set that feature for any altitude. Rocket doesn't get that high, motor won't fire, but the rest [apogee and main] still function to bring baby home OK.
You can also make the firing velocity dependent.
Depending on what your flying, by the time rocket reaches 1800ft [my setting] it's either going up straight or close. If somethings going to make it fly wonky...it usually happens by then so you can safely trigger a motor ignition past that point.



3. Default setting of pyro 1 on PET 2 is to fire after motor burnout. Be sure you mount it correct end pointing at NC or it will not work. Best to test , for me,simply put in a rocket as ride along, with just one-match hooked up [no charge] See if it fires. There are other ways I'm sure. Usually placed in I/S and fires from below, staying with booster. This is easiest mounting.....there are other ways.

4.Stage seperation is usually done at motor burnout, why carry dead weight? There are a few exceptions [there always are...lol] But for simplicities sake , when learning use default setting and fire at burn out [booster]

When first starting, you should fire sustainer 1 second after burn out. You must learn through experience or sims, how to judge thrust to weight ratios, keeping the stack moving at high enough speed to be safe......At least 10-1 on calm days and around 20-1 when winds over 10...unless you REALLY know what you are doing.

You must weigh the whole stack with motors ready to fly & then be sure the booster motor can lift the stack with minimum 10-1 thrust.
2 stagers require a level of safety far beyond the norm, because what you are doing has SO many ways things can go south fast. It's up to the flier to watch out for everyone else. It's all on your shoulder.

Disclaimer: all the above is my opinion, take it as such.

Edit: If you show up at the RSO table and can't answer the above questions, you will not be able to fly.
Good luck have fun. Be safe.

 

[joey]

Thank you so much Jim for detailed reply!! You have answered my questions perfectly.

Clarifications on some of my silly questions:
I was asking if I can use PET2+ at all, because I did not believe that a staging timer should not have safety feature built-in at all. Especially since even on the manual it says it is designed for staging ignition.
And the question about triggering main on the way up. Well, I was gonna wire the staging ignitor to main's channel if that could've been done. I wasn't really gonna trigger a main chute that way.

Thank you again for the tips! I am still new to this community and I really appreciate all the help I got.

 

[joey]

Thank you Wayco!
Sorry to bother you with simple questions. But is there a difference between airstart and staging motor ignition? I thought they meant the same. :/
I thought I will need either LCD or USB interfaces to use AUX port to do airstart. So I was trying to think of alternatives such as firing motor through altitude-dependent main channel. And thus the silly question on tricking the altimeter.
I have read the manuals but am still bit unclear on the specifics of doing airstart with RRC3. But like you suggested, I have messaged Jim and hopefully I will be able to accomplish that soon.

Thank you so much for taking your time to reply to my posts, much appreciated!

 

[tim cubbedge]

Air start basically means a motor or motors are started after the rocket has left the pad. Typically air starts refer to clusters but a 2 stage rocket is in effect "air started" and Jim does use the term "air start" in his instructions when he is in fact referring to a 2 stage rocket.

 

[Titan II]

Staging is clearly identified in the manual regarding programming the aux channel.

 

[Sabrina]

A good way to learn about "complex" two stage rockets... Find somebody who is really experienced, and partner-up with them.

My mentor helped me learn a little about staging at MWP last year.

 

[SS/EA 6BBL 71 Cuda]

My mentor helped me learn a little about staging at MWP last year.

The best is yet too come...Mums the word.oint:

 

[Bobfly]

Hi Joey,

I just started my two stage adventure a couple of months ago. Missile Works makes great products. However there are better choices out there for firing the sustainer. The really safe altimeters for two stage rockets offer sensors that will not allow the sustainer motor to fire if the rocket is tilted from vertical more than a user setable number of degrees.

The Missle Works RRC-3's third channel can be set to fire the sustainer. While the third channel can be set not to fire below a certain altitude, it cannot be set not to fire if the rocket is too far off from vertical flight.

Good Luck,
Bob

 

[markkoelsch]

With the RRc3 I believe you need to sim the flight first to gather some information. What you are looking for is time to a certain altitude assuming a vertical or close to vertical flight. In other word s, if you rocket reaches a thousand feet in three second vertically then fire the sustainer. If it hits a thousand feet in four seconds it is too far off of vertical. This takes some sim work.