Estes Ascender - Av Bay Addition

Looks awesome! The G74-9 economax is a good motor for this one without mods. I added about 2/3 OZ of nose weight via epoxy in the nose cone, but my bird has gone up 3 times with that motor. 9 seconds puts it just past apogee and about 2500-2700 feet. It is pretty quick off the pad though.

swatkat said:

Looks awesome! The G74-9 economax is a good motor for this one without mods. I added about 2/3 OZ of nose weight via epoxy in the nose cone, but my bird has gone up 3 times with that motor. 9 seconds puts it just past apogee and about 2500-2700 feet. It is pretty quick off the pad though.

Click to expand...

Thanks and nice! Did you add nose cone weight because of sim results or for another reason?

Greg

After getting the battery collar designed, I began working on how to mill it out since this would have operations on the top and bottom. The piece is milled from 1/2" birch plywood (actually it's about 0.478" thick). Here are the final results:



In the center, there is a tapped hole for a 6-32 screw, so the battery cap can be secured. The center metal piece is a 0.125" wide by 0.19" deep aluminum, epoxied in place, drilled & tapped, then surface milled.


Here is a pic of the battery collar in place to check for fit. It fit well at the location it was designed for with no interference on the sled or as it slid into the av bay coupler. I'm really happy about that last part, as there isn't much room for error.




I still need to mount the battery holders into the wells and figure out wiring paths, but that's for another day.

Greg

GregGleason said:

Thanks and nice! Did you add nose cone weight because of sim results or for another reason?

Greg

Click to expand...

I added it to be "safe" and to also limit the altitude a bit. We often fly with a 2500 foot ceiling.

swatkat said:

I added it to be "safe" and to also limit the altitude a bit. We often fly with a 2500 foot ceiling.

Click to expand...

Ahhh ... ok. Yep, that's a good strategy to give the altitude a haircut.

Greg

I trimmed the middle section of an "N"-size battery holder to accommodate the 3 x SR44 style batteries. I then placed it into one of the two wells in the battery collar. The friction fit is very cozy, so I may not need to glue it since once the battery cap is on things should move very little, if at all.



Speaking of the battery cap, here is a test fit. The middle hole is to accommodate the head of the 6-32 screw. it fits on this test with no problem.



Greg

I did a test of the battery pack. I put the batteries in backward, so I got a negative value for the volts. The good news is that it is the requisite 9V and enough current to run the MAWD.




Greg

Next on the agenda is to do a preliminary test of the circuitry. I went to a local Radio Shack and got a bulb and bulb socket to act as a test light for the circuit test.

The switch is from Mouser (653-SS-10) and is an SPDT pin plunger. In the desired configuration, when the plunger is depressed (pushed down by a brass pin), the circuit is open. When the pin is removed, the circuit is closed and current will flow to the electronics. Note in the pics below you can see the Energizer 357/303 silver oxide cells nestled inside the battery collar.

Test with the pin in (open circuit, light off):



Test with the pin out (closed circuit, light on):



Now I need to do some soldering and design a mount for the switch.

Greg

Here is the design for the switch mount.



Getting the location of the holes right was a chore, as the holes are pretty small and only take 2-56 sized screws.

Greg

Here is the resulting switch bracket. The good news is that the switch fits inside the bracket.



I still need to mill out the holes (and figure out how to do that).

Greg

The problem was how to put the requisite holes into the bracket. The solution was to make a fixture to hold the bracket in place. Sometimes you have to make parts to make parts. Being that I was using tiny 2-56 screws I was pretty nervous as there is really no room for error. I was pleasantly surprised and relieved that the holes were spot on and that there was minimal play when assembled.





The nice thing is that the switch hole should be very close to the future switch band port.

This was of the biggest areas of concern for the project, so I am glad I have achieved this level in the av bay project. Now I have to figure how to get the proper orientation on the sled when I epoxy it in place.

Greg

I made some more progress, in fact I am almost finished with the av bay.

I made a couple of e-match analogs for the MAWD's continuity check. I used JST's connectors to make the connections a bit easier for me.



I soldered the parts that needed it and while it is not pretty, it's good enough.



Best of all, it powered up fine and gave 3 strong beeps in this configuration. The second best thing is the assembly all fits inside the 4" av bay coupler and all of the orientation keys work as advertised. I feel pretty satisfied that nearly all of my theoretic design choices have lived up to the harsh reality of the real world. I'm sure that this is a much easier process when you have bigger rockets and the internal volume isn't as crowded. But it is nice to have come up with a winner. While it has yet to prove itself in flight, I have a lot of confidence because I believe I have put in the requisite "sweat equity" to make it all happen.

I still need to make a switch port for the switch band. The switch key (1/8" brass rod) needs to be cut and tapped so it can be assembled with the system in the "safe" position.

I'm hoping that it's all down hill from here.

Greg

Well, I am now in the home stretch.

Instead of having elegant screws to support the switch bracket on the sled, I opted for a "Soviet Style" solution: A blob of epoxy. This was because the brass pin guide (a hole) broke away and I had to epoxy it again, but it changed the angle of attack. So I had to discover the new orientation and let the switch bracket settle where it wanted to. Oh well, at least it works.

Since the av bay is essentially finished (I still need to do some odds and ends), it was time to do a dress rehearsal and fire it up for flight configuration (with "analog" e-matches and no added BP to the charge wells) and weigh it.

Below is the result.



At 156.5 grams (~5.5 oz), that's not too bad. The all-up flight configuration for my Ascender is 569 grams with an AT RMS E23-5T, so about 27.6% of the original rockets weight. The av bay would have weighed even more if I went with a standard 9 volt battery.

What's nice is that the system works and I can put it together in about a 1/4 of the time as it took for my first av bay. It just took a while to plan and think things out, then sketch it out in CAD to see if would first work in the virtual world. When it's all together it feels solid and I have a high confidence level that it will worked as advertised.

So now I need to do the odds and ends and get ready for ground testing.

Greg

Since I underestimated the BP required (I thought 0.7 g would work, but 0.9 is the minimum), I needed the lengthen the charge well.

Since I used K&S brass tubing, they made the solution easy for me. I read somewhere that the tubes are designed to fit inside each other, so I got the next size up and cut a 0.50" sleeve and an 0.25" extension. I then used 5-minute epoxy to bond the parts.



Greg

I hope to fly this in a couple of days. I still need to do some further ground testing tomorrow to dial in the charge amounts and the recovery system.

If this works, this will be my first successful dual deploy flight. This has been one of my rocketry goals since I purchased the MAWD a little over 9 years ago.

OpenRocket has some helpful suggestions for motors. My goal is to have a flight between 1K and 2K for the apogee.



Greg

Not sure how I missed it, but that is some fine work.

Tonimus said:

Not sure how I missed it, but that is some fine work.

Click to expand...

Thanks!

Since this is new territory for me the confirmation helps.

Greg

Launch report can be found here:

https://www.rocketryforum.com/showt...eport-First-Successful-Dual-Deployment-Flight

Greg