Help with Dual Deployment

I need some advice about making a dual deployment system that can fit in a 38mm dia. rocket (LOC Legacy). I'm trying to see if it is possible in this size. I am using a PerfectFlite MAWD altimeter. I drew up a couple plans already but the main problem I am running into is having a vent hole so the altimeter can judge the altitude and preventing ejection gas from seeping in the altimeter bay. Some pictures or explanations of your own dual deployment systems would be greatly appreciated.

it's quite difficult to do, actually.

My recent build has been a 38mm Minimum diameter, minimum length rocket. ended up with a 30" x 1.5" tube with full dual deployment using a PICO Alt.

You would probably be able to scale down the allthread altimeter bay design using 4-40 or 8-32 hardware. Try to fit everything inside your coupler, believe me with the 38mm, it's much easier that way!

Its difficult, but not impossible. I've seen it done. Like DPatell said, you're going to have to re-think the hardware to hold the electronics bay together. I've had a similar idea with a LOC Legacy built mostly stock, but that would fly on H motors...

Thats one of the hardest things I've built so far in rocketry,Was just what your asking for rocketboy. The altimeter bay took longer Than the rest of the rocket. And the rocket turned out longer than I wanted it to. but it's been up 4times once on a I-300 That my wife flew it on. And 3times on G-motors. The prefect flite worked grate, And I used the little chrismass lights for the deploment charge. I'll get out there in the next day and pull it apart and post some picture on the bay for you.

I've got a cool little design that I've used on a 38mm minimum diameter and the MAWD. I don't have the pics here, but will try to post them this afternoon sometime. For starters though, the AB is about 15-17 cm long and is completely removable. It almost has to be for something this small. The AB is attached to the BTs with 6 mini screws and I simply use the wires as a switch. There's really no way use any other method.

I totally bashed an Estes Prowler kit to do mach flights. So far so good on the setup. I've haven't used a motor for mach yet, but smaller motors have performed fine.

Shane

This is currently my best design so far. It's a little sketchy but you should be able to get the jist of it.

rocketboyG80:

heres a .gif showing a dual deployment setup where both teh drogue/main are ejected out the top of the body tube/nose cone or it could be down towards the fin can too...

I'm working on a modifcation of this idea using 2 small "ejection" tubes within a larger tube, with 1 ejection tube holding the drogue and the other the main chute....

A variation on shockwaveriderz is to use a small (29-38mm) tube expoied directly to the inside of the airframe.
Mount your drogue chute in the small tube, and have it fit as flush to the end of the nose cone as possible.
Mount your remaining chute and charge in the "other space” and there is an easy, reliable 1-ended dual deploy.

I'm still trying to think up a way that you could use a super long motor ejection as a main back up. I.e.- if the drogue charge works and separates it will deploy the drogue chute and work like a normal 2 stage deployment. But if the rocket doesn't separate, then the long motor ejection charge would be able to deploy the name.. I have some ideas, but haven't tested them out.. Most involve rerouting ejection gasses, a tricky if possible proposition.


Nick

Here is a few pictures of a 38mm altimeter bay. That I made for the perfect flite. I would of never thought I could of got it all in there. But it just takes alittle time. (maybe alot of time.) But it works grate and I sure like how you can down load the flite on to the computer. The one thing I would of done diffrent is not use the I-bolts and just took the schock cord and epoxyed that inside of a couple and then installed the up inside the main and drogue compartments. if you want me to explain more. Let me know. The pictures are in the file marked. Whats on your table. https://photos.yahoo.com/rockets_r_us2 Hope this will help you out some.

The pictures you guys posted helped me to get a better idea of what I'm doing. Before I wasn't really sure if I was doing it right. But now I have another question, and that has too do with the types of ejection charges you used with your dual deployment systems. I am going to use a Pratt VWEC with Pyrodex P in it. I'm not too sure about the Pyrodex yet. I hear it is slightly harder to light than BP but it is safer due to that characteristic. I already bought a pound of it but I could take it back. Does anyone have any experience with smokeless powders?

I found this thread that might help


https://www.rocketryforum.com/showthread.php?s=&threadid=3344&highlight=Pyrodex

I have used pyrodex charges, the only "trick" is the charge must be contained to fully burn. The vwec will work just fine as long as you prep the charge properly.
Put in the amount of pyrodex you need, then fill to remainder of the tube with wadding (pack it in as tight as you can). Then use electrical tape to securely and tightly seal the tube. The electical tape will contain the charge long enough for all the pyrodex to burn instead of just blowing out the unburned particles.

Warning this is just an opinion - when your messing with DD I'm of the opinion that this is enough. One doesn't need to worry about the charges going off or not. The altimeter will provide you with enough nerve damage. Pyrodex, as mentioned, CAN work. BUT it has to be carefully tended too. Stick with BP as it has been proven over the years. Just remember the KISS method. If you want to complicate issues do a 2 stager or an air start or something.

Shane Heilman

BP substitutes such as pyrodex are every bit as reliable as BP provided you prep the charges properly. But I would strongly encourage people to test fire the charges a couple of times to make sure you are doing it right.
I have relied almost exclusively on electronic deployment since I certified L1. Even that flight was a dual deploy with a PML Mini-BBX. I have not had a single failure in almost 2 years worth of flights. I stick with quality ematches and fresh batteries, and feel no more nervous using pyrodex or cleanshot than I do using BP.

I am using a PerfectFlite MAWD altimeter.

Click to expand...

I know you are using the a PerfectFlite, but you might check out the Instruction Manual for the Missle Works RRC2:

https://www.missileworks.com/documents/RRC2_Manual_(revC).PDF

There is a description for a mounting system using a 38mm coupler tube.

I've finally posted the pictures of my min. diam altimeter bay that I promised last week. Sorry it took so long.


https://f1.pg.photos.yahoo.com/ph/m...&.view=t&.done=http://f1.pg.photos.yahoo.com/



Shane

Umm... is it just my computer or does it say that this file is inaccesible?

Working on it. Sorry.

Shane

S'okay. Just wanted to make sure it wasn't a computer problem. Also, I decided that I will return the Pyrodex P for FFFFg black powder just to keep things as simple as possible.

OK. OK. Here you go.

https://f1.pg.photos.yahoo.com/mshaner_climb

Shane

This is the final dual deployment system I decided on. It is only a litttle different than the one I posted before but it should work much better. Please tell me if you see any problems that I may have overlooked.

Looks good from here. Basically the same as those posted. I know mine works and this one should too.

Nice drawing, BTW.

Shane

Tomorrow is the big day. I plan to actually fly my dual deployment Legacy. It is stretched to 58" and weighs about 20oz. Although one change I made was that I has to remove the little pressure tube because during a ground test today the pressure tube blew apart. I think the problem was that it was made of a 1/2" cardboard lug, I really needed to use metal. I don't have time to fix it now so I am just going to fish the ejection canister down to the bottom of the tube so the rocket will deploy as if it were the motor's charge firing. I tested it twice so I know it works. I will use either an Ellis G35-10 or a F20-7 Econojet for it's first dual deployment flight. Ideally I would have wanted an F50-9 because the F20 will not boost it very high and the Ellis G35 is a little too much for a first flight. Does anyone have a recommendations?

After asking around a little at the launch on Sunday it seemed the Ellis G35 was the best choice. So the moment came when the lauch button was pressed and... just igniter smoke. I was using a Magnalite but even that wasn't enough. I then used the very reliable premade Quickburst Twiggy igniter. This time I got another puff of smoke, then another, then finally the motor came up to pressure. Those Ellis Mountain G35's sure are stubborn if this is normal for that motor. Anyway the 20oz Legacy roared skyward to what the altimeter reported as 2174 feet in 11.55 seconds. The drogue deployed right on cue. The rocket then came down quickly on the drogue streamer until it reached 500 feet when the main deployed, or should have. I did not have two 12 foot lenghts of tubular Kevlar for both the drogue and the main so I had to use a 6 foot lenght on the drogue which was way too short also I hink I used too much black powder. It seperated. The body and payload of the rocket crashed down in the far corner of the field as the nosecone, shockcord, and main chute drifted down slowly. I walked over to the wreckage to find that the seperated parts actually landed right near each other, but the altimeter was silent. Upon inspection of the line graph (that I transfered when I got home) I found that the battery disconnected when the main charge fired. This may have been due to the short shock cord but I also need to use a stronger mounting method for it next time. But when it loses power (I found out by asking PerfectFlite) it automatically reports an altitude of 20,000 feet on the beeper, but it still shows correct info on the graph up until the point where it lost power, which shows a spike of nonexistant altitude. To top this off I didn't use a big enough heatshield or I used too much BP or both for the main and it burnt the chute pretty badly.

So next time I know, use more shock cord, use more heatshield less BP, and mount the battery better.

Rocketboy, You mentioned the Magnalite ignitor in your post. What is the best/least expensive vendor to buy the kit from? Thanks