Minimum Diameter CF 2 stage build thread "Kobayashi Maru"

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andrewlathrop87 said:
What do you mean RF dorking deployment electronics? The altimeters are barometric pressure altimeters. How can a "signal" interfere with that? I have heard that sometime before but never had a issue? Can it work in the reverse? Can a barometric pressure altimeter interfere with the signal of the GPS?
Click to expand...

The more modern deployment devices are relatively immune to this phenomena and the Missileworks device works with the GPS tracker portion. There is an article in the NAR journal some years ago that recounts the conversion of 2 watt dog trackers and how
the trackers interfered with some deployment devices. The EggTimer products uses opto-isolators on both channels and is very resistant to Rf interference with my hacked testing. I held a 5watt handitalkie and APRS tracker
next to the altimeters being tested with contained ematches and nothing but the "ready to fly" beep. Don't pooh-pooh the phenomena as there are folks who have been burned by it in the past.
Most of the modern deployment devices are resistant to Rf.

Aside from what I reported, I witnessed a very large project with two Adept 22 deployment devices lock up with a Garmin dog tracker and go in ballistic. Ground testing in an identical situation after the mishap repeated the the lockup. Behavior that can be seen is shutdown and recycling while in flight after giving the "ready to go" beep, deployment on the pad, deployment on ascent or any combination thereof. The manual of the AIM2 USB deployment altimeter specifically states that it shouldn't be used with an Rf tracker. I've copied the extract from the manual here:----

2.4.2 RF interference
Please note that the AIM USB is sensitive to RF interference. If you do place a
tracking transmitter or any kind of telemetry device in close proximity to the AIM
USB, it will affect its performance and might even trigger a false launch.
Tests have indicated that a 100mW transmitter with a quarter-wave whip antenna
placed adjacent to the AIM will reset it and cause it to malfunction. This is a severe
case, but keep it in mind when designing you electronics bay. Other radio controlled
sources in the vicinity should not affect the AIM.

Again, since you are using the Missileworks GPS tracker and the RRC3 you should be fine, otherwise Jim Amos would not have a viable device to release in the first place.

You are going to be flying two different trackers on a staged complex flight. I'd say it behooves one to do some simple, easily performed ground testing to make certain the electronics play well together. Yeah, they're "supposed" to be better
than previous offerings but I've stood next to a rocket where the tracker cycled the deployment device. Ready to go beeping stopped, took me a second to realize this was an, "Oh (expletive deleted)" moment and stepped away just before I put the igniter in to see the apogee charge blow and then the main blow while the upper bay was on the ground. If this was a large staged project, I could'a got cooked.

If I was tackling this project, even though the electronics look good, are likely resistant to the effects of Rf and you will be all right, I'd do some battery cycling by letting everything stand with contained ematches for an hour.
If you still hear the "ready to go" beeping and your trackers are giving you good data you can be more assured you won't have any surprises when you make the attempt. If matches "pop" during your test, you hear your electronics
recycling or if they just stop working, it's better to have that occur during a safe controlled test situation than be out at a launch site. Plus, you have the potential of a large motor going off in your face. Test it first please.
Also your greatest resource would be Jim Hendricksen since he's already answered your thread. He has flown some very complex electronic installations with great success.
Kurt Savegnago (Don't mind me, I'm paranoid around large rocket motors)
 
Last edited:
ksaves2 said:
The more modern deployment devices are relatively immune to this phenomena and the Missileworks device works with the GPS tracker portion. There is an article in the NAR journal some years ago that recounts the conversion of 2 watt dog trackers and how
the trackers interfered with some deployment devices. The EggTimer products uses opto-isolators on both channels and is very resistant to Rf interference with my hacked testing. I held a 5watt handitalkie and APRS tracker
next to the altimeters being tested with contained ematches and nothing but the "ready to fly" beep. Don't pooh-pooh the phenomena as there are folks who have been burned by it in the past.
Most of the modern deployment devices are resistant to Rf.

Aside from what I reported, I witnessed a very large project with two Adept 22 deployment devices lock up with a Garmin dog tracker and go in ballistic. Ground testing in an identical situation after the mishap repeated the the lockup. Behavior that can be seen is shutdown and recycling while in flight after giving the "ready to go" beep, deployment on the pad, deployment on ascent or any combination thereof. The manual of the AIM2 USB deployment altimeter specifically states that it shouldn't be used with an Rf tracker. I've copied the extract from the manual here:----

2.4.2 RF interference
Please note that the AIM USB is sensitive to RF interference. If you do place a
tracking transmitter or any kind of telemetry device in close proximity to the AIM
USB, it will affect its performance and might even trigger a false launch.
Tests have indicated that a 100mW transmitter with a quarter-wave whip antenna
placed adjacent to the AIM will reset it and cause it to malfunction. This is a severe
case, but keep it in mind when designing you electronics bay. Other radio controlled
sources in the vicinity should not affect the AIM.

Again, since you are using the Missileworks GPS tracker and the RRC3 you should be fine, otherwise Jim Amos would not have a viable device to release in the first place.

You are going to be flying two different trackers on a staged complex flight. I'd say it behooves one to do some simple, easily performed ground testing to make certain the electronics play well together. Yeah, they're "supposed" to be better
than previous offerings but I've stood next to a rocket where the tracker cycled the deployment device. Ready to go beeping stopped, took me a second to realize this was an, "Oh (expletive deleted)" moment and stepped away just before I put the igniter in to see the apogee charge blow and then the main blow while the upper bay was on the ground. If this was a large staged project, I could'a got cooked.

If I was tackling this project, even though the electronics look good, are likely resistant to the effects of Rf and you will be all right, I'd do some battery cycling by letting everything stand with contained ematches for an hour.
If you still hear the "ready to go" beeping and your trackers are giving you good data you can be more assured you won't have any surprises when you make the attempt. If matches "pop" during your test, you hear your electronics
recycling or if they just stop working, it's better to have that occur during a safe controlled test situation than be out at a launch site. Plus, you have the potential of a large motor going off in your face. Test it first please.
Also your greatest resource would be Jim Hendricksen since he's already answered your thread. He has flown some very complex electronic installations with great success.
Kurt Savegnago (Don't mind me, I'm paranoid around large rocket motors)
Click to expand...

Thanks, Yea the RTX is in nose cone and RRC3 and RRC2+ will be in avbay, so in 2 different compartments. Those compartments are 2 feet away from each other.

In the booster the (2) strataloggerCF's and BRB900 will be right next to each other in interstage coupler. I need to speak with Greg at BRB to ask what he thinks. My BRB900 is from early 2012.

That is a good idea on setting whole stack up in the hard for an hr with everything on.
 
I've had no trouble with the low powered 70cm BLGPS tracker sitting next to a Raven altimeter. Again, the modern electronics are more resistant so you'll be ok but test to be sure. Bounce it off Greg he'll probably have some info of what has flown with what. When you go out to fly, you'll be more concerned with setting up and getting your tracking downlinks up and running, making sure the deployment charges are correct. Is that sustainer igniter secured and connected well so it doesn't get dislodged?
It's stuff like that you want to be concerned with and not getting the jitters about the electronics not being up to snuff. Should be quite a ride. The first major "sweat it out" moment will be sustainer ignition and the next one will be as it nears apogee and
data starts coming in. Waiting for data from apogee always seems to take forever. Oh, I forgot, you'll also be tense waiting to hear from the booster tracker too. I take it you'll have one person monitoring the booster and you'll be following the sustainer tracker.
The booster person can yell out when the positions start coming back in and give a direction to scan and see if the deployment events can be seen.

Two persons monitoring the tracking chores is great. A fellow pointed out to me one time that the Kenwood D72A I was using for APRS tracking can be selected to show the GPS altitude only. If two people show up with D72's one can have theirs plugged into a mapping GPS to plot the rocket flight and give positions so one knows where to look to get a visual. The second unit can scroll to the screen to monitor the GPS altitude and call out the altitudes to the expected main event.

The ultimate tracking program I've experienced, Xastir, unfortunately takes a linux laptop and will display a rocket icon with horizontal speed, direction, bearing and altitude right next to the rocket name/icon. It is a really classy setup that is hackable
to be useful with NMEA trackers. I suspect the Missileworks GPS tracker will work with Xastir as Jim Amos mentions it should work with the GPS Rocket Locator program. The BRB900 unfortunately won't work with GPS Rocket Locator as Greg mentioned he has tried but there might be something non-standard in the NMEA strings that interfere with decoding from the BRB.

If you have the RTX on hand Andrew and it has Bluetooth capability, get a hold of an Android device with onboard GPS receiver and download "GPS Rocket Locator". Pair your RTX to your Android device, fire up GPS Rocket Locator and make sure you go to the setup screen and choose the B/T device that's your receiver. After awhile, you'll see a blue dot that's your base position and a pink thumbtack that's the rocket tracker. I use a Nexus 7 2013 with 32Gb.
More memory, more maps can be stored. I put it in a flat black painted box to protect from the sun's glare otherwise I can't see the screen.
You can download the map zoom levels and store them on your device for off-internet use. The program can be quirky at times. Sometimes when downloading maps it locks up but I find after exiting out, no harm is done to already downloaded maps
and one can try again.

This is the easiest mapping, tracking program out there. Believe me, I've struggled for years with some of the Ham tracking software and it can be extremely hard to get some of this stuff to do what one wants it to do.
A rocket guy got Xastir (a generally APRS only package) to work with NMEA trackers and helped me with it by sending me a perl script. The APRSIS32 community showed me how I can get two instances of that program to display
a local position AND monitor an NMEA tracker. Again, this is ordinarily an APRS only program. I have it working on a tablet and it's bullet proof. The bread crumbing of the rocket positions has the GPS altitude stamped right next to the position! Screenshot (14).jpgScreenshot (3).jpg
The screens are from ARSIS32 and the one on the left is unfortunately a CATO and I didn't need the tracker. As you can see, didn't get very high!:lol:
The one on the right is a ballistic flight when stupidhead didn't put enough powder in to bust the shearpins! Long story that one. No positions at altitude which lends me to suspect there may be a problem with
a tracker in a high dynamic state. The one or two positions near the ground before it hit led me to the rocket. It was FG so I just dug it out and got a new tracker. It was completely sight unseen and I wouldn't have
found it without the "sacrificial" EggFinder. The black line is my position being recorded in real time walking out to the rocket. Real eye candy isn't it! All this is done live and not simply data transposed to a map afterwords.
It's doable in the field.

Honestly, you can't go wrong with giving GPS Rocket Locator a shot if you haven't tried it yet. It is so much easier than the other programs I mention above. Those programs above display more useful information live but are a real PITA to get going.
If you can see that your rocket looks like it came down near a road, might be better to drive to it than go in a straight line. That's more important to one who flies on farmland and not out west on the playa where one can just about drive anywhere once on the flats. Kurt
 
I have been brainstorming about this project. Nothing is assembled yet. I have had the thoughts to build this 2 stage with a min diameter sustainer. I planned on flying it with a 54mm L motor but heck I can build it with a 75mm min diameter baby L. I contacted Gary at Aerotech and he told me at one time rouse tech made a aft closure for this purpose. I asked Gary if the forward closure that comes with the 75mm adapter system could work and he said possibly not because it my not seal the aft end.

When it comes to min diameter booster what are you guys doing for your electronics bay in the booster since you do not have an interstage coupler. The motor of the sustainer sticks out of the sustainer to act as a coupler.

thanks
 
Last edited by a moderator:
andrewlathrop87 said:
When it comes to min diameter booster what are you guys doing for your electronics bay in the booster since you do not have an interstage coupler. The motor of the sustainer sticks out of the sustainer to act as a coupler.

thanks
Click to expand...

Assuming you are talking about an electronics bay in the booster for the purpose of booster deployment, I have done this two ways. One way is a single-piece upper airframe where the bay is pinned about in the middle of the tube. The bay slides in from the top of the tube, and this approach saves a tube break (i.e., the bay is not also serving as a coupler to hold two shorter sections of air frame together). Then, this upper air frame section is simply conventional dual deploy with the drogue section below and the main section above. The second way I have done this is with a single booster air frame tube where the bay sits on top of the motor and deployment is out the top only. In either case, the trick of the design is to position a bulkhead near the top of the booster air frame that covers the main chute. It might be located, for example, 4 inches down from the top of the booster tube. It functions as a nose cone for the main chute compartment and is blown out of the tube when the main is deployed. In this respect, it must be designed such that it can be ejected without binding in the top part of the tube. This bulkhead can be designed to support the motor if you want, and it can also be designed to allow a separation charge between it and the bottom of the motor. I have even designed this bulkhead with keys to prevent turning between the two air frames. This bulkhead is really the only thing that differentiates the booster as a two stage instead of a single stage rocket. Its proper design is obviously quite important.

Jim
 
JimJarvis50 said:
Assuming you are talking about an electronics bay in the booster for the purpose of booster deployment, I have done this two ways. One way is a single-piece upper airframe where the bay is pinned about in the middle of the tube. The bay slides in from the top of the tube, and this approach saves a tube break (i.e., the bay is not also serving as a coupler to hold two shorter sections of air frame together). Then, this upper air frame section is simply conventional dual deploy with the drogue section below and the main section above. The second way I have done this is with a single booster air frame tube where the bay sits on top of the motor and deployment is out the top only. In either case, the trick of the design is to position a bulkhead near the top of the booster air frame that covers the main chute. It might be located, for example, 4 inches down from the top of the booster tube. It functions as a nose cone for the main chute compartment and is blown out of the tube when the main is deployed. In this respect, it must be designed such that it can be ejected without binding in the top part of the tube. This bulkhead can be designed to support the motor if you want, and it can also be designed to allow a separation charge between it and the bottom of the motor. I have even designed this bulkhead with keys to prevent turning between the two air frames. This bulkhead is really the only thing that differentiates the booster as a two stage instead of a single stage rocket. Its proper design is obviously quite important.

Jim
Click to expand...

I think I understand. I like both ways. Hey Jim do you have a 3d diagram of this layout or pictures to show each way?
 
andrewlathrop87 said:
I think I understand. I like both ways. Hey Jim do you have a 3d diagram of this layout or pictures to show each way?
Click to expand...

I have previously posted this picture of one of the bulkheads that sits near the top of the booster air frame. This particular one sits on a coupler tube ring that is glued into the top of the air frame. It is shear-pinned into the top of the tube just as you would pin a nose cone. It has pins that key into the sustainer motor to keep the air frames from turning relative to each other along with a little well for the motor nozzle and the separation charge. The bulkhead can be turned in any orientation without getting stuck in the air frame, so that it doesn't get jammed into the upper part of the air frame when you want the main to deploy. Every bulkhead that I make is just a variation on the theme.

The electronics bay approaches are just conventional, except that the bays slide into the top of the tube. Often, electronics bays function as couplers holding two sections of air frame together, with or without a switch band. This means that there is a tube break or two tube breaks if there is a switch band. I instead slide the bay in from the top and pin it into position. This just avoids an unnecessary tube break, and I like to minimize those on multi-stage rockets.

I have one rocket with a bay that sits directly above the motor. It's about 2" long and actually sits on a short piece of coupler tubing glued into about the middle of the air frame. The all thread from the forward closure of the motor passes through the bay so that when you screw the eye bolt onto the top of the bay, it retains the motor and also keeps the lid on the top of the bay. It's a PITA to assemble, but it keeps things about as short as they can be.

Jim

Transition cap.jpg
 
blackjack2564 said:
My fins are 3/16th's carbon uni-plate. I have 4 fins also.....used approximately 3 sets of Hysol. Didn't use the needle twist mixing tips, just pumped into cups and mixed by hand. [those darn tip sets are expensive & single use]
I used a 1.5 in PVC pipe section to pull fillets, probably overkill size wise. Charlie used 1 in. section PVC on his.

View attachment 304139

So depending on your fillet size you may use much less. [you have 3 fins vs my 4]
There was some blush on mine, which came off easily with windex and dried with denatured alcohol. High humidity in North Carolina.
Click to expand...

Not only are the tips single use but they do waste a some amount of epoxy since they cant be cleaned out completely.
 
JimJarvis50 said:
I have previously posted this picture of one of the bulkheads that sits near the top of the booster air frame. This particular one sits on a coupler tube ring that is glued into the top of the air frame. It is shear-pinned into the top of the tube just as you would pin a nose cone. It has pins that key into the sustainer motor to keep the air frames from turning relative to each other along with a little well for the motor nozzle and the separation charge. The bulkhead can be turned in any orientation without getting stuck in the air frame, so that it doesn't get jammed into the upper part of the air frame when you want the main to deploy. Every bulkhead that I make is just a variation on the theme.

The electronics bay approaches are just conventional, except that the bays slide into the top of the tube. Often, electronics bays function as couplers holding two sections of air frame together, with or without a switch band. This means that there is a tube break or two tube breaks if there is a switch band. I instead slide the bay in from the top and pin it into position. This just avoids an unnecessary tube break, and I like to minimize those on multi-stage rockets.

I have one rocket with a bay that sits directly above the motor. It's about 2" long and actually sits on a short piece of coupler tubing glued into about the middle of the air frame. The all thread from the forward closure of the motor passes through the bay so that when you screw the eye bolt onto the top of the bay, it retains the motor and also keeps the lid on the top of the bay. It's a PITA to assemble, but it keeps things about as short as they can be.

Jim
Click to expand...

Hey Jim do you have picture it this in a rocket set up?
 
andrewlathrop87 said:
Hey Jim do you have picture it this in a rocket set up?
Click to expand...

No, I don't have anything that shows how the internal parts are configured. This rocket is the test rocket for my vertical stabilization system, which is currently prepped for a flight (which means I can't take it apart for a picture).

Jim
 
JimJarvis50 said:
No, I don't have anything that shows how the internal parts are configured. This rocket is the test rocket for my vertical stabilization system, which is currently prepped for a flight (which means I can't take it apart for a picture).

Jim
Click to expand...

ok thanks
 
I know there are many different ways to build an interstage coupler. Do you guys have some good ideas? I have everything that I need for it, but i know there are multiple ways to do it. I am not set on any particular design.
 
andrewlathrop87 said:
I came across the cable cutter method recently. Has anyone had success and or failures using this method. It seems to work more straight forward then a tender descender. https://ptrocketry.blogspot.com/p/cable-cutter.html
Click to expand...

I've used those many, many times with great success. I've only had one failure out of dozens of flights with them and I think that was because I used the powder from a CTI ejection charge. The rocket was small and landed without damage anyway. If it's a larger rocket, I'd use two for redundancy.
 
Last edited:
watheyak said:
I've used those many, many times with great success. I've only had one failure out of dozens of flights with them and I think that was because I used the powder from a CTI ejection charge. The rocket was small and landed without damage anyway. If it's a larger rocket, I'd use two for redundancy.
Click to expand...

Yea if I were to use it would use 2 on the same zip tie. They sell them in pairs.
 
andrewlathrop87 said:
I came across the cable cutter method recently. Has anyone had success and or failures using this method. It seems to work more straight forward then a tender descender. https://ptrocketry.blogspot.com/p/cable-cutter.html
Click to expand...

Check out the Rattworks ARRD. I use it and absolutely love it. Many flights and no failures. If you use it with a deployment bag for the main it works really well and you dramatically reduce the risk of tangling.
 
NateLowrie said:
Check out the Rattworks ARRD. I use it and absolutely love it. Many flights and no failures. If you use it with a deployment bag for the main it works really well and you dramatically reduce the risk of tangling.
Click to expand...

how does this work. Never heard of it.
 
andrewlathrop87 said:
how does this work. Never heard of it.
Click to expand...

Here are the links:

This design dates back 2005 when a now-defunct company BlackSky started making them. It is the 3rd generation of devices that they used for single compartment dual deploy. Rattworks licensed the design and is the manufacturer now. The design is very similar to commercial explosive bolt designs. The key advantage is how it holds the bolt. The tender descender holds both pieces together with a pin that gets blown out of the socket. That horizontal movement while the pin is being pulled up by the respective recovery line can lead to jamming or inadequate release. The ARRD holds the pin in with ball bearings that are in line with the pull of the system. Jamming is eliminated.

To see how a recovery system would be configured, see my level 3 documentation in the first post: https://www.rocketryforum.com/showt...Shortfall-(Formula-200)&p=1637546#post1637546

At MDRA, myself and Fred Wallace (one of the local TAPs) fly a ton of ARRD flights and we haven't had a failure in a while. I had one failure 8 years ago but that stemmed for user error and resulted in the rocket deploying the main at apogee.
 
NateLowrie said:
Here are the links:

This design dates back 2005 when a now-defunct company BlackSky started making them. It is the 3rd generation of devices that they used for single compartment dual deploy. Rattworks licensed the design and is the manufacturer now. The design is very similar to commercial explosive bolt designs. The key advantage is how it holds the bolt. The tender descender holds both pieces together with a pin that gets blown out of the socket. That horizontal movement while the pin is being pulled up by the respective recovery line can lead to jamming or inadequate release. The ARRD holds the pin in with ball bearings that are in line with the pull of the system. Jamming is eliminated.

To see how a recovery system would be configured, see my level 3 documentation in the first post: https://www.rocketryforum.com/showt...Shortfall-(Formula-200)&p=1637546#post1637546

At MDRA, myself and Fred Wallace (one of the local TAPs) fly a ton of ARRD flights and we haven't had a failure in a while. I had one failure 8 years ago but that stemmed for user error and resulted in the rocket deploying the main at apogee.
Click to expand...

I will be retaining motor with something similar to a min diameter aeropack retainer. The threaded forward closure will be in use. Can I still use the ARRD?
 
Regarding Jim's 'slide in' A/V bay. I've done this with several rockets and use Featherweight magnetic switches so I don't need any holes in the airframe for switches. It takes some getting used to working with the switches but so far they have performed great.


Tony
 
manixFan said:
Regarding Jim's 'slide in' A/V bay. I've done this with several rockets and use Featherweight magnetic switches so I don't need any holes in the airframe for switches. It takes some getting used to working with the switches but so far they have performed great.


Tony
Click to expand...

That doesn't make sense. If there are no holes for the avbay then how does the altimeters get samples of outside air?
 
The bay slides in, but there are access holes to switches mounted on the altimeter skid. Those are the only vent holes. I don't use mag switches because I haven't had much luck with their durability.

Jim
 
I got the Loctite Hysol 120 that Crazy Jim recommended from McMasterCarr. I got the 200ml tube since I have 6 fins to attach. I will be using CrazyJim's method of using a 1.5" diameter PVC 1" long to pull the
 

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