AT Astrobee Mods for a H motor

[jetra2]

Hi,

I am Starting to build an Astrobee D, and I want to Fly it on lower class H motors. I'm not really changing anything but doubling up the lower centering with a spare, and not putting in a thrust ring or engine hook. I am building it with epoxy, should i give the fins interior fillets or no? Anybody that has done this, please help me.

I'll post pics on my online photo album as the rocket is constructed.

Thanks,
Jason

 

[gothique_97]

The AT Astrobee is plenty stable for 29/180 reload motors [H128, H238, G75]. Leaving out the motor hook and thrust ring is a good idea, of course. Strengthening the fins with internal fillets would probably not be wasted time. I'm hesitant to tell you to double up the rear centering ring; if it were my project, I'd probably just put a THICK coat of epoxy on the ring once its in place.

I've built an AT Arcas for low-end H motors [and for Rocketflite Silver Streak motors], which meant leaving out the engine hook. I strengthened the fins just a little bit. Because the fins on the Arcas don't extend past the bottom of the body tube as they do with the Astrobee, they weren't nearly as prone to breaking off upon returning to Earth.

 

[n3tjm]

I left the motor hook in my bird. I ground down the forward tab to allow the longer motors passage in the motor tube.

 

[boatsandrockets]

I really doubt that internal fillets are needed, but they couldn't hurt

 

[TurboWS6]

I didnt do anything to mine except swap the coupler for a altimeter bay/coupler I made for dual deployment. launched it on a I-161 several times

 

[ibeblip]

I built mine "STOCK".
But after the first flight, I did apply small epoxy fillets on the root edges of the fins internally and externally.

 

[jetra2]

Hi all,

After plenty of procrastination, , I have finally started work on my AT Astrobee D. I am modifying for the H and low-I motors. I am also putting an altimeter bay in it. I'm gonna show you some pics right now, then ask a quick question down below.

Here is a pic of the fin can. I built it as a single unit.

Jason

 

[jetra2]

Man this fin can is heavy! I'm not sure if you can read it, but the scale says .661 pounds, or about 10.5 ounces....

Jason

 

[jetra2]

OK! Cool pics, huh?

Well, now here's my question. When I lengthened my fin slots to make room for the single piece fin can shown above, it significantly weakened the lower 6 inches or so of the bottom tube. See pic now. Do you see how it looks "weak" ?

Jason

 

[jetra2]

Now, here I am proposing my idea to change that. I am going to cut off a chunk of the coupler and epoxy it down in there, like so. More than just strengthening the bottom, it makes it look better by it being one piece. For now, the rest of the coupler tube is going to just hold it together. I am going to buy another coupler just for the purpose of a electronics bay. Does anyone know if LOC couplers are compatible with AT tubing, and does LOC sell a 2.56 electronics bay?

Thanks,
Jason

 

[Chilly]

I'm planning the same kind of project myself, and thought about the fin can approach but figured it might weaken the tube. I think a good strong LOC coupler would fix yours up fine. If they don't offer it in that size, you could cut out a section and "roll your own" to fit.

Here's what I'm planning on doing for my version:

-replace chutes with one 36".
-reinforce shock cord with kevlar sleeve.
-replace motor mount with 38mm 17" tube (and trim the fins down to size with a table saw).
-add a LOC baffle unit to the new motor mount.
-add plywood or G10 centering rings fore & aft of the MMT & use the fiber rings for support along the middle.
-two-part foam around the fins since the fin-locks won't be used.
-blind nuts & screen clips for motor retention.
-add a coupler to the aft end for strength.
-add a payload bay, and anything else for nose weight to counterbalance all the mods.

Just might use the leftover 29mm motor tube and baffle unit for my Saturn V! Will definitely use the leftover chutes for it.

Whaddaya think?

 

[jetra2]

Although I didn't get much done today, I did get the coupler cut to size. What I did is I inserted the coupler into the motor mount end of the tube and marked the length, then used some tape to give me a ridge to follow, and cut the coupler. Man, those things are HARD to cut thru...I'm glad it's paper and not phenolic!

On the other hand, this idea will work great! IMHO, it successfully accomplishes the original plan of strengthening the end of the tube. Check out the pic!

Jason

 

[sandman]

Jason,

I'm watching what you do very carfully.

I have one of those kist and I am looking for something in the Level 1 class to build.

I am level 1 after all!

Maybe for LDRS???

So I'm watching you!

sandman

 

[Stymye]

I did the exact same thing on my 29mm estes phoenix...It really keeps the fins from flexing at touchdown .nice work jason!

 

[Martin Vrstal]

I think your doing a fine job....keep up the good work.

I wish I had one of those kits to play with.

Now show me the money

 

[Chilly]

Looks like that'll do the trick. Who made the coupler?
I'm jealous, dude...

 

[jetra2]

HELP!!!! I need some advice on how to build an altimeter bay! I am likely going to use a Missile Works RRC2 X unit, mainly so I won't have to buy a special 8" coupler. See picture.

Ok, I am trying to make this as easy on myself as possible. The bay would be three pieces, two bulkplates and the coupler. The 8-32 threaded rod serves the purpose of holding the entire assembly together during flight and allows me to take it apart for prep. The ends of the rod have two nuts that tighten down on them and hold the thing together. The RRC2 X mounts on the rod side of the plywood plate and the battery on the opposite side. There will be a hole where the power wires will go. That is the plan for the interior of the coupler.

Now the outside. The two plywood plates will be copys of each other. I will mount a small CPVC cap on the left hand side. This will be able to hold about 1 gram of BP or whatever is readily available, along with a wadding plug and some tape. On the right side is the U bolt shock cord mount. These two are 180 degrees from each other. Then, perpendicular to these are the two holes for the threaded rod. My thinking is that the nut on the rod will be enough to protect the altimeter from the hot gases. Should I get a few small o-rings for a little extra safety?

Also, how should I attach the bay? I am thinking of having it be one total and separate piece that I can remove, but the ejection charge can not. How would y'all recommend me doing this?

Jason

 

[Ryan S.]

Ill IM you

 

[Ryan S.]

okay cracking the fingers...getting read for alot of typing.....okay go.

first thing to do...

1. If the coupler isnt strong enough glass the inside. If it is strong dont worry about it.

2. make 4 bulkheads. 2 need to fit in the coupler and 2 need to fit in the main BT.

3. glue the small bulkheads onto the big bulkheads...make sure they are centered. Now this should result in a big bulkead with a lip that fits smoothly into the coupler and into the BT.

4. Now drill your holes. 2 for the allthread, and at least one more for your recovery harness (2 more if your using a U-bolt).

5. now take your allthread (cut to size) and screw a bolt on there and epoxy it down. (do this for both peices)

6. Now slide a washer down the allthread and slide the althread up one of the bulkheads.

7. Next, slide a washer down each peice of allthread and a nut after these and tighten (this is being done on the side that does not yet have a nut)
this is the aft end of your Ebay.

8. Make your sled now. there are different ways to do this the only requirement being the launch lugs or tubes, fit the allthread and they are the right distance apart to slide down the althread.

9. Slide your sled down the allthread followed by a nut (on either peice of allthread) This is too keep your altimeter from bounceing around.

10. Do your switches etc however you see fit.

11. you want to make some holes in your coupler in an area near the top (3/4 of the way up is perfect) for T-nuts to be glued in. These are simply threaded on the inside and allow something for the screws to go into

12. Slide the coupler over the altimeter/allthread assembly now place the second bulkhead on this.

13. put some washers over the bulkhead and then wing nuts.

This is pretty much the hole Ebay.

You are also gonna want to drill holes in the BT that match up with those in the EBAY so you can screw it down.

ahhhhh finished

here is a pic

https://www.vahpr.com/s/s_ab1.jpg

todd harrison told me how to do it...just thought I should mention his name here

 

[n3tjm]

I like your design so far Jason. The only concern I see is how the rings fit on the tube coupler? Does the ring fit inside the coupler, or outside the coupler? If it fits on the outside, you need to glue on a smaller ring that fits inside the tube coupler that acts like a lip. If it fits on the inside, add a tube that fits inside the tube coupler so the plates have something to rest againts. The first choice is the best choice when dealing with a payload bay of that size.

For larger birds, I have grown fond of LOC's electronics bay. Here is a picture of what they do, maybe that will give you some ideas.

[Added] Ryan beat me to the punch, but I must say I like his design too. I seen it up close and personal. So many good ideas out there... you shouldn't have any problems figuring out what you want to do.

 

[Rocketman248]

I didn't use charge holders for my dual deployment rocket. I just had a small hole through each of the bulkheads. I fed an ematch through each hole and used a piece of a plastic bag to hold the charge. Just make a little cup with the plastic, pour in the black powder, stick in an ematch, and tape it up with masking tape.