LOC-IV BASIC avionics for basic dual deploy recommendations

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Lt72884

Lt72884

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Ok, for my second L2 flight i would really really like to learn the bare basic setup for a dual deploy. I have never done this so i have no idea what electronics to get for my rocket or how to set it up.
I may have messed up during construction of the LOC-IV. I glued the coupler to the upper airframe (probably should not have done that), BUT i did not glue the nosecone in. Its held in with some screws so i can access the upper airframe tube. This leads to my questions:

1. Do i need another coupler to make the bay? If so, would a 3d printed one work?
2. What are some good easy basic starting electronic kits i can buy with good documentation for a dual deploy? or what electronics in general should i get?
3. Im on a small budget so not to fancy is nice. I do not need GPS since this will be a J270 or lower launch
4. Anyway to remove the epoxy on the coupler or whats the best way to re-add an e-bay?
5. Since im using aj270, or so. im guessing the ejection charge will pop the drogue and the av bay will pop the main?
6. Are the av bays friction fit or are they held in with screws, removable rivots and or shear pins?

Below is my upper airframe. I removed the nosecone to make sure my bag of powdered sugar was still intact after the first launch haha... yes, its powdered sugar, 358 grams to be exact. It is sitting on top of the epoxied bulkhead.
I am looking for some guidance and recommendations. I have never setup electronics before like this before, and any help and complete guidance is much appreciated.

thank you much for any help:)
This will be for my first L2 electronic flight


1679357197523.png
1679357435154.png
The last photo is how it currently is setup for single deployment
1679357474397.png
 
Last edited:
Lt72884 said:
Ok, for my second L2 flight i would really really like to learn the bare basic setup for a dual deploy. I have never done this so i have no idea what electronics to get for my rocket or how to set it up.
I may have messed up during construction of the LOC-IV. I glued the coupler to the upper airframe (probably should not have done that), BUT i did not glue the nosecone in. Its held in with some screws so i can access the upper airframe tube. This leads to my questions:

1. Do i need another coupler to make the bay? If so, would a 3d printed one work?
2. What are some good easy basic starting electronic kits i can buy with good documentation for a dual deploy? or what electronics in general should i get?
3. Im on a small budget so not to fancy is nice. I do not need GPS since this will be a J270 or lower launch
4. Anyway to remove the epoxy on the coupler or whats the best way to re-add an e-bay?
5. Since im using aj270, or so. im guessing the ejection charge will pop the drogue and the av bay will pop the main?
6. Are the av bays friction fit or are they held in with screws, removable rivots and or shear pins?

Below is my upper airframe. I removed the nosecone to make sure my bag of powdered sugar was still intact after the first launch haha... yes, its powdered sugar, 358 grams to be exact. It is sitting on top of the epoxied bulkhead.
I am looking for some guidance and recommendations. I have never setup electronics before like this before, and any help and complete guidance is much appreciated.

thank you much for any help:)
This will be for my first L2 electronic flight
Click to expand...
My first question is, what other motors do you intend to fly after the j270? Are you going to move up to a K motor? If so, you should build with that in mind or you'll be building all over again for the next flight.

1. No, you don't need a coupler to build an av-bay. There are several threads on hear that document av-bays in various configurations. Personally I wouldn't trust the outer part and caps of an av-bay that is 3D printed. Depending on the configuration, it may need to withstand the forces on the shock cord for both deployments and everything between the nose cone and the fin can.

2. Any of the basic DD altimeters will work. It doesn't need to be the top end units with 4+ pyro channels, or GPS, or accelerometers. The Altus Metrum EasyMini, MissleWorks RRC2, Perfectflite Stratologger CF, or the Eggtimer Quark if you want to build the board yourself, are all good, simple, starting altimeters.

3. Understood about not thinking you need GPS, but what about the next flight, even if it's in a bigger, different rocket? You can always get a tracking system later, but consider getting one now if it's included in the altimeter, just for possible future use. I've seen several L1 flights with light rockets and baby H motors that drifted off and weren't found. I think there is a higher probability of that with L2 flights. Just losing sight on a "regular" flight can result in losing it all if nobody sees the main open down range.

4. Not sure how you take the old coupler out to use a new one for an av-bay. I would peel the old one from the inside and sand the BT. Or just get a new BT when you get the coupler and bulkheads for the new av-bay and use the old coupler/payload if you want to fly it on motor eject and a smaller motor and JLCR on the windy days.

5. you can use the motor ejection for apogee deployment, but that kind of defeats the purpose of dual deployment. The altimeter is going to be much more accurate with the apogee deployment than what you can get drilling a delay charge. In 16 years of DD, I've never used motor deployment as an apogee charge, or even as a backup for that matter. I just don't see the point since the electronics are more accurate and more dependable.

6. yes, yes, and no. The most common DD configuration is to have the av-bay attached to the bottom of the payload BT. That can be screws, removeable rivets, or other removable attachments. You can use your current glued in coupler, but the forward bulkhead would be difficult to install and connect and charge preparation and connection would be problematic. Shear pins are used to keep the nose cone on when the apogee charge goes off so the main chute doesn't deploy at apogee. They are almost never used to attach the av-bay to the payload tube.

There are lots of build threads that include av-bay construction along with threads just about av-bays on here. Search is your friend.

Good luck.
 
Last edited:
Handeman said:
My first question is, what other motors do you intend to fly after the j270? Are you going to move up to a K motor? If so, you should build with that in mind or you'll be building all over again for the next flight.

1. No, you don't need a coupler to build an av-bay. There are several threads on hear that document av-bays in various configurations. Personally I wouldn't trust the outer part and caps of an av-bay that is 3D printed. Depending on the configuration, it may need to withstand the forces on the shock cord for both deployments and everything between the nose cone and the fin can.

2. Any of the basic DD altimeters will work. It doesn't need to be the top end units with 4+ pyro channels, or GPS, or accelerometers. The Altus Metrum EasyMini, MissleWorks RRC2, Perfectflite Stratologger CF, or the Eggtimer Quark if you want to build the board yourself, are all good, simple, starting altimeters.

3. Understood about not thinking you need GPS, but what about the next flight, even if it's in a bigger, different rocket? You can always get a tracking system later, but consider getting one now if it's included in the altimeter, just for possible future use. I've seen several L1 flights with light rockets and baby H motors that drifted off and weren't found. I think there is a higher probability of that with L2 flights. Just losing sight on a "regular" flight can result in losing it all if nobody sees the main open down range.

4. Not sure how you take the old coupler out to use a new one for an av-bay. I would peel the old one from the inside and sand the BT. Or just get a new BT when you get the coupler and bulkheads for the new av-bay and use the old coupler/payload if you want to fly it on motor eject and a smaller motor and JLCR on the windy days.

5. you can use the motor ejection for apogee deployment, but that kind of defeats the purpose of dual deployment. The altimeter is going to be much more accurate with the apogee deployment than what you can get drilling a delay charge. In 16 years of DD, I've never used motor deployment as an apogee charge, or even as a backup for that matter. I just don't see the point since the electronics are more accurate and more dependable.

6. yes, yes, and no. The most common DD configuration is to have the av-bay attached to the bottom of the payload BT. That can be screws, removeable rivets, or other removable attachments. You can use your current glued in coupler, but the forward bulkhead would be difficult to install and connect and charge preparation and connection would be problematic. Shear pins are used to keep the nose cone on when the apogee charge goes off so the main chute doesn't deploy at apogee. They are almost never used to attach the av-bay to the payload tube.

There are lots of build threads that include av-bay construction along with threads just about av-bays on here. Search is your friend.

Good luck.
Click to expand...
To answer your question, no other motors will go in this rocket. J will be the highest. If i am going to do a K motor, i will rebuild an entirely differnt 58mm rocket for that.
ill reply to the rest once home and off the train : ) thanks for the recommendations. This is all new to me and i might as well learn the correct way
 
Handeman said:
My first question is, what other motors do you intend to fly after the j270? Are you going to move up to a K motor? If so, you should build with that in mind or you'll be building all over again for the next flight.

1. No, you don't need a coupler to build an av-bay. There are several threads on hear that document av-bays in various configurations. Personally I wouldn't trust the outer part and caps of an av-bay that is 3D printed. Depending on the configuration, it may need to withstand the forces on the shock cord for both deployments and everything between the nose cone and the fin can.

2. Any of the basic DD altimeters will work. It doesn't need to be the top end units with 4+ pyro channels, or GPS, or accelerometers. The Altus Metrum EasyMini, MissleWorks RRC2, Perfectflite Stratologger CF, or the Eggtimer Quark if you want to build the board yourself, are all good, simple, starting altimeters.

3. Understood about not thinking you need GPS, but what about the next flight, even if it's in a bigger, different rocket? You can always get a tracking system later, but consider getting one now if it's included in the altimeter, just for possible future use. I've seen several L1 flights with light rockets and baby H motors that drifted off and weren't found. I think there is a higher probability of that with L2 flights. Just losing sight on a "regular" flight can result in losing it all if nobody sees the main open down range.

4. Not sure how you take the old coupler out to use a new one for an av-bay. I would peel the old one from the inside and sand the BT. Or just get a new BT when you get the coupler and bulkheads for the new av-bay and use the old coupler/payload if you want to fly it on motor eject and a smaller motor and JLCR on the windy days.

5. you can use the motor ejection for apogee deployment, but that kind of defeats the purpose of dual deployment. The altimeter is going to be much more accurate with the apogee deployment than what you can get drilling a delay charge. In 16 years of DD, I've never used motor deployment as an apogee charge, or even as a backup for that matter. I just don't see the point since the electronics are more accurate and more dependable.

6. yes, yes, and no. The most common DD configuration is to have the av-bay attached to the bottom of the payload BT. That can be screws, removeable rivets, or other removable attachments. You can use your current glued in coupler, but the forward bulkhead would be difficult to install and connect and charge preparation and connection would be problematic. Shear pins are used to keep the nose cone on when the apogee charge goes off so the main chute doesn't deploy at apogee. They are almost never used to attach the av-bay to the payload tube.

There are lots of build threads that include av-bay construction along with threads just about av-bays on here. Search is your friend.

Good luck.
Click to expand...
Since this is only going to be my 3rd flight, i keep forgetting that the ejection charge is NOT built into the motor like the smaller model rocket motors are. Im still used to the auto ejct rather than the "bore a hole, and put the BP in" like i did with teh H550 and other J270.

Awe yes, some one PM'd me 2 or 3 weeks ago showing me a nose cone avionics and i spaced that. Thats my bad. Ill search for some more ideas and once i have that planned. Then ill be asking for help on how to set everything up.

I think ill pick a brand, email them and see if i can get a complete set through them. Just keep it easy.

I have a main chute already, maybe ill just make a drogue chute from simular material or buy one from somewhere.

Thanks
 
Lt72884 said:
5. Since im using aj270, or so. im guessing the ejection charge will pop the drogue and the av bay will pop the main?
6. Are the av bays friction fit or are they held in with screws, removable rivots and or shear pins?
Click to expand...
You can use normal electronic dual deployment for both drogue and main and use the motor ejection for drogue backup. If you do this, make sure you stagger the electronic drogue ejection and motor ejection by a second or two. If possible, get the J270 with the 14 second delay so you have the opportunity to drill it to whatever delay you wish.

There are several ways to configure DD. I typically use shear pins on the aft avbay coupling to the booster section. The upper body section is secured by screws or plastic rivets to the forward avbay coupler with the nosecone secured with shear pins.
 
Here is how I would approach it. It’s not ideal, but we left ideal in the dust a little ways back when you glued in the coupler. 😀 I mean no criticism here—I had to do the second option to add electronic deployment to my L1 rocket after I glued in the coupler.

If the upper body tube is short enough that you can reach all the way down to the bottom, build an AV bay into a smaller tube than the body tube. 2.6” would be fairly easy to lay out. You’ll need to move the recovery eye bolt off to the side of the bulkhead, and you can use the existing hole on centerline to secure the AV bay. You’ll need another hole or some kind of connector to lead the ematches through the bulkhead. This option could be done with a 3D printed bay since it won’t be taking the entire recovery load.

If you can’t reach all the way down, I’d just build an AV bay into a new coupler that slides down and rests on the existing one. You’ll have to get creative about how to transfer the recovery loads, maybe by using extra long threaded rods that can reach through the existing bulkhead.

Either way, you’ll need an upper recovery harness, shear pins to hold the nose cone on, and brass strips to help the cardboard tube cut the shear pins.

If I was in your spot with a student budget, I would just use one altimeter and motor eject as a drogue backup. Leave space in your AV bay to add another altimeter or tracking later. Since you’ve used Eggtimer equipment for your school project, if use a Quark or a Quantum. A Quantum will be easier to set up since it doesn’t need a separate switch, and it might not be much more expensive. Either way, set the drogue charge for apogee and still the motor delay a couple of seconds long so it doesn’t go off at the same time as the altimeter charge.
 
boatgeek said:
Here is how I would approach it. It’s not ideal, but we left ideal in the dust a little ways back when you glued in the coupler. 😀 I mean no criticism here—I had to do the second option to add electronic deployment to my L1 rocket after I glued in the coupler.

If the upper body tube is short enough that you can reach all the way down to the bottom, build an AV bay into a smaller tube than the body tube. 2.6” would be fairly easy to lay out. You’ll need to move the recovery eye bolt off to the side of the bulkhead, and you can use the existing hole on centerline to secure the AV bay. You’ll need another hole or some kind of connector to lead the ematches through the bulkhead. This option could be done with a 3D printed bay since it won’t be taking the entire recovery load.

If you can’t reach all the way down, I’d just build an AV bay into a new coupler that slides down and rests on the existing one. You’ll have to get creative about how to transfer the recovery loads, maybe by using extra long threaded rods that can reach through the existing bulkhead.

Either way, you’ll need an upper recovery harness, shear pins to hold the nose cone on, and brass strips to help the cardboard tube cut the shear pins.

If I was in your spot with a student budget, I would just use one altimeter and motor eject as a drogue backup. Leave space in your AV bay to add another altimeter or tracking later. Since you’ve used Eggtimer equipment for your school project, if use a Quark or a Quantum. A Quantum will be easier to set up since it doesn’t need a separate switch, and it might not be much more expensive. Either way, set the drogue charge for apogee and still the motor delay a couple of seconds long so it doesn’t go off at the same time as the altimeter charge.
Click to expand...
Thanks for the reply and information. This will help me out with my goals as well as personal achievement. When i started a few months back, i knew nothing of rockets. I have only flown the model rockets, many times as a young kid, but never got involved with teh science or engineering of them.

Luckily the upper body tube is short enough for me to reach down into. Plus i can cut the bottom of the nosecone section out if i need to stuff the AV in there or at least have the nose cone section available to do so.

Since i can reach my arm down to the bulkhead, if i drill 2 quarter inch holes for all thread, i just slide the AV sled onto the threaded rod and tighten down the nuts correct? Technically i wouldnt need a hole for an e-match since i would be using the motor ejection, but if i did need a hole, i can drill another in the bulkhead that is small enough for the wire correct?

If i did choose to use a smaller coupler to hold the electronics, what holds the coupler to the airframe so its not just sitting loose? do any of the bulkheads get glued in? or is it all friction fit? I think that part confuses me. I see so many pictures of AV bays with bulkheads and threaded rod OUT of the coupler, that im not sure if one bulkhead gets glued in and you just undo the nuts on oneside and slide out the sled?

When you say "you’ll have to get creative about how to transfer the recovery loads, maybe by using extra long threaded rods that can reach through the existing bulkhead." What is ment by recovery loads? are those the plastic cap things that set on the ends of the threaded rod that hold the e-match and powder?

lets say i go with the simplest option at the moment which is to use the motor ejection as one of the charges to deploy a device. With this current rocket, should i keep the main chute exactly where it is in the lower airframe above the motor? and then have a smaller chute in the nose cone area that deploys at apogee? IE, hit apogee, eggtimer goes off to eject nose-cone chute, then 2 seconds or maybe even 3 seconds later, motor ejection deploys main in the lower airframe?



Miracle option #3 professor decides to buy me another LOC-IV for testing... i wont count on this one haha
 
Last edited:
Voyager1 said:
You can use normal electronic dual deployment for both drogue and main and use the motor ejection for drogue backup. If you do this, make sure you stagger the electronic drogue ejection and motor ejection by a second or two. If possible, get the J270 with the 14 second delay so you have the opportunity to drill it to whatever delay you wish.

There are several ways to configure DD. I typically use shear pins on the aft avbay coupling to the booster section. The upper body section is secured by screws or plastic rivets to the forward avbay coupler with the nosecone secured with shear pins.
Click to expand...
if i understand you correctly, i would have 2 drogue ejections then? one with the electronics and then a second with the motor? and then the main would be a 3rd deployment using electronics as well?

thanks
 
Lt72884 said:
When you say "you’ll have to get creative about how to transfer the recovery loads, maybe by using extra long threaded rods that can reach through the existing bulkhead." What is ment by recovery loads? are those the plastic cap things that set on the ends of the threaded rod that hold the e-match and powder?

lets say i go with the simplest option at the moment which is to use the motor ejection as one of the charges to deploy a device. With this current rocket, should i keep the main chute exactly where it is in the lower airframe above the motor? and then have a smaller chute in the nose cone area that deploys at apogee? IE, hit apogee, eggtimer goes off to eject nose-cone chute, then 2 seconds or maybe even 3 seconds later, motor ejection deploys main in the lower airframe?

Miracle option #3 professor decides to buy me another LOC-IV for testing... i wont count on this one haha
Click to expand...
"Recovery loads" in that context are likely the forces being exerted on the bulkheads by either the recovery harnesses pulling on the eyebolts at the time of airframe separation, or the force being applied against the bulkhead from the ejection charges (assuming ejection charge cannisters affixed to the bulkheads) at the time they are fired by the altimeter.

An even simpler option which is still considered dual-deploy is not to use an altimeter to separate your airframe at apogee and then again at a pre-set altitude for main deployment, but rather to use the motor ejection to deploy the main chute at apogee (deployment event #1), but have the main secured by a Jolly Logic Chute Release (JLCR). The bundled up main serves as something of a drogue to stabilize the rocket during descent, and then when the lower pre-set altitude is reached the JLCR releases the main chute, allowing it to open (deployment event #2).

If you do intend to use an altimeter for your deployment events, firing black powder charges for drogue and main, then fliers who rely upon the motor ejection for backup to the initial altimeter-initiated drogue deployment typically set the motor delay duration for 2 - 3 seconds past the calculated time to apogee. If the altimeter has already set off the drogue charge, then the motor ejection is only firing into an empty body tube. If the altimeter drogue charge failed to fire, then the motor ejection charge will at least get the airframe separated and the drogue chute (if used) out of the airframe.

Search the forum and you will find that the majority of modelers recommend putting the drogue in the lower body tube, and the main goes in the payload space above the avionics bay. When the altimeter fires the main ejection charge the nose cone is pushed off, pulling the main chute with it.

LOC offers both payload tubes and avionics bay assemblies. Since your Loc IV is currently built with the coupler glued into the payload tube provided with the kit initially, you may want to consider purchasing an avionics bay kit for 4" diameter models, and then a new longer payload tube which can house your main chute. That way the avionics bay can be secured to the payload tube with removable screws or rivets, making access to your altimeter to charge/change batteries, affix eMatch leads, manage your deployment charges much easier. It will also have bulkheads designed to deal with the "recovery loads".

As others have noted, spend some time with the search function and in the Recovery sub-forum; lots of information about dual deployment, how to configure avionics bays, etc. Plus there is also John Coker's site (http://jcrocket.com/electronic-recovery.shtml), the HPR Primer as authored by member "mtnmanak" (https://www.mountainmanrockets.com/index.php/hpr-primer/), and a host of others.
 
Lt72884 said:
Thanks for the reply and information. This will help me out with my goals as well as personal achievement. When i started a few months back, i knew nothing of rockets. I have only flown the model rockets, many times as a young kid, but never got involved with teh science or engineering of them.

Luckily the upper body tube is short enough for me to reach down into. Plus i can cut the bottom of the nosecone section out if i need to stuff the AV in there or at least have the nose cone section available to do so.
Click to expand...
While you can do a nose cone AV bay, it's a little more of an expert-level move. It's fairly common on minimum diameter rockets (search head end deployment), but I don't think it makes as much sense on a larger diameter rocket like yours.
Lt72884 said:
Since i can reach my arm down to the bulkhead, if i drill 2 quarter inch holes for all thread, i just slide the AV sled onto the threaded rod and tighten down the nuts correct? Technically i wouldnt need a hole for an e-match since i would be using the motor ejection, but if i did need a hole, i can drill another in the bulkhead that is small enough for the wire correct?
Click to expand...
If you do the smaller AV bay nested in your coupler, I would build it in a 2.6" coupler that slides down next to your recovery harness that's moved off to the side. The AV bay would just bolt to the bulkhead, likely with one bolt. See below for a discussion of ejection charges.
Lt72884 said:
If i did choose to use a smaller coupler to hold the electronics, what holds the coupler to the airframe so its not just sitting loose? do any of the bulkheads get glued in? or is it all friction fit? I think that part confuses me. I see so many pictures of AV bays with bulkheads and threaded rod OUT of the coupler, that im not sure if one bulkhead gets glued in and you just undo the nuts on oneside and slide out the sled?
Click to expand...
I've always built them with no glue. There are caps on each end that are held on to the coupler by the threaded rod(s). That makes it a little easier to wire up since you can connect wires with no caps on and then later put everything together. It wouldn't be wrong to glue one end in, but it's not the way most people do it.
Lt72884 said:
When you say "you’ll have to get creative about how to transfer the recovery loads, maybe by using extra long threaded rods that can reach through the existing bulkhead." What is ment by recovery loads? are those the plastic cap things that set on the ends of the threaded rod that hold the e-match and powder?
Click to expand...
There are some loads that the ejection charge puts on the bulkheads. However, what I meant was the shock loads from the recovery harness coming tight and the chute opening. Those shock loads shouldn't be super-high if your harness is long enough, but it's good to design for worst case (like 50-100x heaviest individual weight connected to the harness). There's lots of thread here about selecting and sizing a recovery harness and selecting and installing shear pins for the nose cone.
Lt72884 said:
lets say i go with the simplest option at the moment which is to use the motor ejection as one of the charges to deploy a device. With this current rocket, should i keep the main chute exactly where it is in the lower airframe above the motor? and then have a smaller chute in the nose cone area that deploys at apogee? IE, hit apogee, eggtimer goes off to eject nose-cone chute, then 2 seconds or maybe even 3 seconds later, motor ejection deploys main in the lower airframe?
Click to expand...
My opinion is that if you're not using the altimeter for both main and drogue, you're not really practicing dual deploy for when your big rocket needs it. The normal approach is to have the drogue in the lower section and the main in the upper section. You can do the opposite, but (a) it doesn't really work with motor eject and (b) there's some good reasons for breaking the rocket in the middle at apogee. You can do some research here and find out all about it.

The normal order of events is:
Apogee
Primary drogue charge at or near apogee
Backup drogue charge (~1s after primary, ~20% larger than primary charge)
Motor eject (~2 seconds after last ejection charge)
Rocket falls quickly under drogue, at maybe 80-100 ft/s to minimize drift
At specified altitude (typically 700-1000 feet), primary main charge
At 100-200 feet lower, backup main charge, ~20% larger than primary charge

Backup charges are only fitted if you have a 3- or 4-output altimeter or a redundant backup altimeter

This gives you the least drift while still giving you a soft landing. If you're flying with a single altimeter and motor eject, it gives you redundancy on the most critical ejection event, the drogue. If the main charge fails, you might pop a fin on a hard landing under drogue only, but you're unlikely to seriously damage the rocket. If the drogue charge(s) fail, you'll have the rocket coming in ballistic until it reaches the main ejection charge altitude. At that speed, it will likely zipper, may destroy the chute, and will likely still hit the ground hard enough to pop a fin.
Lt72884 said:
Miracle option #3 professor decides to buy me another LOC-IV for testing... i wont count on this one haha
Click to expand...
Seems unlikely, but you can always hope! :D
 
One other note. You don't have to use shear pins. Friction fit will work just fine. Make sure you can pick up the rocket by the nose cone and give is a slight shake. It shouldn't come apart, even if a joint or two opens up slightly. Just don't overdo the apogee charge.
Shear pins are simple in fiberglass. They are more complicated to install and get working correct in cardboard and plastic.
 
boatgeek said:
While you can do a nose cone AV bay, it's a little more of an expert-level move. It's fairly common on minimum diameter rockets (search head end deployment), but I don't think it makes as much sense on a larger diameter rocket like yours.

If you do the smaller AV bay nested in your coupler, I would build it in a 2.6" coupler that slides down next to your recovery harness that's moved off to the side. The AV bay would just bolt to the bulkhead, likely with one bolt. See below for a discussion of ejection charges.

I've always built them with no glue. There are caps on each end that are held on to the coupler by the threaded rod(s). That makes it a little easier to wire up since you can connect wires with no caps on and then later put everything together. It wouldn't be wrong to glue one end in, but it's not the way most people do it.

There are some loads that the ejection charge puts on the bulkheads. However, what I meant was the shock loads from the recovery harness coming tight and the chute opening. Those shock loads shouldn't be super-high if your harness is long enough, but it's good to design for worst case (like 50-100x heaviest individual weight connected to the harness). There's lots of thread here about selecting and sizing a recovery harness and selecting and installing shear pins for the nose cone.

My opinion is that if you're not using the altimeter for both main and drogue, you're not really practicing dual deploy for when your big rocket needs it. The normal approach is to have the drogue in the lower section and the main in the upper section. You can do the opposite, but (a) it doesn't really work with motor eject and (b) there's some good reasons for breaking the rocket in the middle at apogee. You can do some research here and find out all about it.

The normal order of events is:
Apogee
Primary drogue charge at or near apogee
Backup drogue charge (~1s after primary, ~20% larger than primary charge)
Motor eject (~2 seconds after last ejection charge)
Rocket falls quickly under drogue, at maybe 80-100 ft/s to minimize drift
At specified altitude (typically 700-1000 feet), primary main charge
At 100-200 feet lower, backup main charge, ~20% larger than primary charge

Backup charges are only fitted if you have a 3- or 4-output altimeter or a redundant backup altimeter

This gives you the least drift while still giving you a soft landing. If you're flying with a single altimeter and motor eject, it gives you redundancy on the most critical ejection event, the drogue. If the main charge fails, you might pop a fin on a hard landing under drogue only, but you're unlikely to seriously damage the rocket. If the drogue charge(s) fail, you'll have the rocket coming in ballistic until it reaches the main ejection charge altitude. At that speed, it will likely zipper, may destroy the chute, and will likely still hit the ground hard enough to pop a fin.

Seems unlikely, but you can always hope! :D
Click to expand...
The eye-bolt, i epoxied to the bulk head as per the instructions of a build video. I dont think its going to move, or move easily. I had forgotten that i did that until i opened it up about 20 minutes ago to get a visual of your explanation.. Im sorry, i done goofed by gluing everything together haha.

I do want to learn the correct way and use altimeters to cause the ejection. I feel that learning it this way is going to be more of a benefit to me and others

I supplied some images of a cad model i made, would this idea work?

1679425054542.png
1679425164656.png
The bay 1/4th inch wooden bulkhead could rest on top of the inside nut of the upper tube as shown below
1679427135535.png

1679427161848.png
1679427279193.png
the threaded rod would use a nylock nut at the bottom by the eyering, and at top as well. i would just remove the nuts at the top and pull the whole sled out.

Could this work?
 
Lt72884 said:
The eye-bolt, i epoxied to the bulk head as per the instructions of a build video. I dont think its going to move, or move easily. I had forgotten that i did that until i opened it up about 20 minutes ago to get a visual of your explanation.. Im sorry, i done goofed by gluing everything together haha.

I do want to learn the correct way and use altimeters to cause the ejection. I feel that learning it this way is going to be more of a benefit to me and others

I supplied some images of a cad model i made, would this idea work?

View attachment 570162
View attachment 570164
The bay 1/4th inch wooden bulkhead could rest on top of the inside nut of the upper tube as shown below
View attachment 570168

View attachment 570169
View attachment 570170
the threaded rod would use a nylock nut at the bottom by the eyering, and at top as well. i would just remove the nuts at the top and pull the whole sled out.

Could this work?
Click to expand...
That should work--it's more or less Option 2 above. You could probably get rid of the extra bottom plywood bulkhead--just notch the sled for and keep your electronics clear of the eyebolt in the middle.
 
boatgeek said:
That should work--it's more or less Option 2 above. You could probably get rid of the extra bottom plywood bulkhead--just notch the sled for and keep your electronics clear of the eyebolt in the middle.
Click to expand...
Awesome. ill see if i want to laser cut some 1/4 inch ply i have with my cutter or 3d print a sled..
Ill start researching electronics as well.
Thanks for all the help on this as well to others who are helping out. i do not want to just be done and use it on a resume`, i want to learn and continue to learn
 
Lt72884 said:
Awesome. ill see if i want to laser cut some 1/4 inch ply i have with my cutter or 3d print a sled..
Ill start researching electronics as well.
Thanks for all the help on this as well to others who are helping out. i do not want to just be done and use it on a resume`, i want to learn and continue to learn
Click to expand...
That's a great attitude to have.

I'm guessing that it will be about 1000 times easier to get the threaded rods into the glued in bulkhead if they have nuts on both sides of the loose bulkhead. The sled doesn't need to be 1/4"--save some space if you have the stock and use 1/8".
 
Just remember the forward bulkhead has to attach the shock cord between it and the nosecone and be able to handle those loads when the nose cone hits the end and the main chute snaps open and the weight of the rest of the rocket hits the end of the apogee cord. You might want to stick with the 1/4" bulkhead.
 
Handeman said:
Just remember the forward bulkhead has to attach the shock cord between it and the nosecone and be able to handle those loads when the nose cone hits the end and the main chute snaps open and the weight of the rest of the rocket hits the end of the apogee cord. You might want to stick with the 1/4" bulkhead.
Click to expand...
The bulkhead should be 1/4". I was intending the sled only at 1/8".
 
Lt72884 said:
if i understand you correctly, i would have 2 drogue ejections then? one with the electronics and then a second with the motor? and then the main would be a 3rd deployment using electronics as well?

thanks
Click to expand...
Correct!
The drogue electronic ejection would typically be at apogee and the motor ejection would hopefully be timed to occur a second or two later. This might be tricky to achieve if your motor ejection delay can’t be timed to occur after the electronic ejection. You don’t really want the motor ejection to occur prior to apogee in this case. However, if it does, then the electronic ejection will become the backup event.
The main ejection will be the third event and will occur at the appropriate altitude on descent. Obviously the main won’t have a backup event in this case.
This leads into the use of redundant altimeters for backup drogue and main ejection events.
 
Voyager1 said:
Correct!
The drogue electronic ejection would typically be at apogee and the motor ejection would hopefully be timed to occur a second or two later. This might be tricky to achieve if your motor ejection delay can’t be timed to occur after the electronic ejection. You don’t really want the motor ejection to occur prior to apogee in this case. However, if it does, then the electronic ejection will become the backup event.
The main ejection will be the third event and will occur at the appropriate altitude on descent. Obviously the main won’t have a backup event in this case.
This leads into the use of redundant altimeters for backup drogue and main ejection events.
Click to expand...
i get what you are saying, ill have 3 events but only 2 physical chutes. IE the drogue goes out at apogee, and then the motor ejection charge goes off in an empty tube IF the electronic deploy was successful.
 
boatgeek said:
That's a great attitude to have.

I'm guessing that it will be about 1000 times easier to get the threaded rods into the glued in bulkhead if they have nuts on both sides of the loose bulkhead. The sled doesn't need to be 1/4"--save some space if you have the stock and use 1/8".
Click to expand...
Great! ill go with a 1/8th inch sled then. I have some 3mm ply i can laser cut or even just 3d print as well.

thank you : ) Im trying to re-learn the correct way and focus on taking it at the correct pace. I even volunteered to help the new freshman
students coming into their first year of engineering to do a lvl 1 build and flight. I will be teaching them open rocket (what i do know of it ), and having them read sections of Steins book as well as read up on the barrowman equations. I can at least help with what i do know for level 1 stuff.
 
Lt72884 said:
I will be teaching them open rocket (what i do know of it ), and having them read sections of Steins book as well as read up on the barrowman equations.
Click to expand...

When I first started in HPR I read "Modern High-Power Rocketry" cover to cover, twice. It's a bit dated, but IMO, it's an excellent way to jump start your HPR journey with lots of practical advice.

https://www.amazon.com/Modern-High-...9313&sprefix=modern+high+poer,aps,1178&sr=8-1
A newer book that's also focused on the practical is "Make: High-Power Rockets: Construction and Certification for Thousands of Feet and Beyond"

https://www.amazon.com/Make-High-Po...db-a437-a52b5d38a7f8&pd_rd_i=1457182971&psc=1
 
kalsow said:
When I first started in HPR I read "Modern High-Power Rocketry" cover to cover, twice. It's a bit dated, but IMO, it's an excellent way to jump start your HPR journey with lots of practical advice.

https://www.amazon.com/Modern-High-...9313&sprefix=modern+high+poer,aps,1178&sr=8-1
A newer book that's also focused on the practical is "Make: High-Power Rockets: Construction and Certification for Thousands of Feet and Beyond"

https://www.amazon.com/Make-High-Po...db-a437-a52b5d38a7f8&pd_rd_i=1457182971&psc=1
Click to expand...
I purchased this book along with Gary steins book. But i have only started garys book. In fact, i purchased 2 copies and gave one to my schools committee for rockets haha
 
One of the easiest ways to start with DD is to get an Apogee-only altimeter like an Eggtimer Apogee, and use a Jolly Logic Chute Release to bind your chute so that it stays reefed until it hits the target altitude. Chances are you could do this with a rocket that you already have... there's a nose-cone mount for the Apogee that only requires drilling a 1" hole in the base of the nose cone, I have done this with 3" diameter plastic nose cones. It's a good way to get your feet wet with electronic deployment without having to build the rocket around the electronics, and you should be easily able to do this with your LOC-IV.
 
cerving said:
One of the easiest ways to start with DD is to get an Apogee-only altimeter like an Eggtimer Apogee, and use a Jolly Logic Chute Release to bind your chute so that it stays reefed until it hits the target altitude. Chances are you could do this with a rocket that you already have... there's a nose-cone mount for the Apogee that only requires drilling a 1" hole in the base of the nose cone, I have done this with 3" diameter plastic nose cones. It's a good way to get your feet wet with electronic deployment without having to build the rocket around the electronics, and you should be easily able to do this with your LOC-IV.
Click to expand...
Which altimeter is a good priced one for a student on a tight budget? also the joly logic, is there a specific place to buy it from? or is amazon ok?(if they have it)
 

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