Baffles in a BT-20?

[astronboy]

Hey gang, I have a design that really requires a baffle. The problem is that it has a BT-20 tube, and I have just never seen one that small. Cab I use a series of 1/2 plates? Any ideas if this will work or not?

Thanks!!

 

[Fore Check]

How about trying a piston arrangement, using a BT20 coupler and a blank plate?

EDIT: the piston would be attached to your recovery tether (kevlar/shock cord) and would be ejected from the body tube and dangling on the tether after recovery deployment (I hope that makes sense)

 

[astronboy]

Unfortunately, I must use a baffle.... This design will be rear-ejected recovery with the recovery syetem being deployed form another tube. Weight in the rear is an issue, so I was hoping to baffle the EJ charge near the nose of the rocket, and duct to the recovery tube.

 

[Stymye]

lots of pressure for a small tube, we know how vigorus those ejection charges can be , baffle with care.

 

[r1dermon]

go to michaels and grab some card stock...then cut out a plate out of some ply, glue it all together, attach your shock cord, and viola, you've got a baffle....you could also use a coupler in place of the card stock.

 

[rokitflite]

Astronboy,
Go get some stainless steel chore boy and make a 1 1/2" long insulating tube that will fit in a bt-20. Cut off a small portion of the chore boy and put it in the insulator tube about as tightly as you would recovery wadding. Place 2 small pins (from a new shirt or something) through the top & bottom of the insulator tube with the chore boy inside to hold it in place. Then trim off the ends of the pins. Slide this in as you would a regular baffle, it works great.

 

[JRThro]

Scott, have you done that in a BT-20-ish tube?

And Merry Christmas, btw.

 

[jflis]

I'd be interested in seeing the design first. If you have the motor in one tube an dthe recovery device in another, the ducting between tubes may be all you need. That is how the FarScape is done and it is more than enough protection from the heat of ejection.

 

[astronboy]

OK, Here is the plan... I was trying to keep it a secret, and just WOW! you guys with a finished rocket... but I guess that ain't gonna happen!!

The idea was to make a squat lander type rocket, that does not eject a forward nosecone. The body is a PNC-80 with most of he shoulder cut off, and a 3" piece of BT-80 as the BT.

My big idea was to have a piece of kevlar exit out the tip of the NC (secured inside by an epoxied in place screw eye) , and run down the side of the rocket to the rear ejected parachute. When deployed, the chute allows the lander to land upright, without the big hole in the top of the rocket normally left by an ejected nosecone.

here is the rocsim:

Phred

 

[rokitflite]

Hi John,
I have used that baffle system in a 13mm rocket before. It is truly amazing how well it takes the heat out of the ejection charge. When we were testing it for use in what became the Aerotech line of kits, we put an Estes D motor in a tube, slid a 1" ball of the stuff right down on top of the motor, pushed a pin through the tube through the middle of the chore boy, then balled up an Estes plastic chute and put it right up against the chore boy. We strapped this tube to a pole and fired it the ejection charge popped the chute without a single weld spot! I love the stuff and I read about it in a rather old book on rocketry.

 

[rokitflite]

Sounds cool Phred! Ironically I am watching the James Bond film "You Only Live Twice" On TNN and they have a craft that looks much like you describe yours... Do you think you will be able to make it open up and eat other space craft?

 

[Mister Rogers]

Originally posted by rokitflite
Sounds cool Phred! Ironically I am watching the James Bond film "You Only Live Twice" On TNN and they have a craft that looks much like you describe yours... Do you think you will be able to make it open up and eat other space craft?

hmmmm.....I wonder if you could make a rocket that opens to release another rocket, perhaps even launch it?

 

[DynaSoar]

Originally posted by rokitflite
Astronboy,
Go get some stainless steel chore boy and make a 1 1/2" long insulating tube that will fit in a bt-20. Cut off a small portion of the chore boy and put it in the insulator tube about as tightly as you would recovery wadding. Place 2 small pins (from a new shirt or something) through the top & bottom of the insulator tube with the chore boy inside to hold it in place. Then trim off the ends of the pins. Slide this in as you would a regular baffle, it works great.

I'd second that. But, I suggest copper coated instead of plain stainless (won't rust as fast), and only use enough to block off most light coming through, not enough so you can tell a difference in the air flow. Probably 1/4 of a pad is plenty. Too much can cushion the ejection shock.

 

[rokitflite]

Hi Dynasoar,
I did not think there was a copper "coated" variety. We used the copper stuff which was more wire like than the stainless steel which has a ribbon like quality and the copper degraded much quicker. I have not had a problem with stainless steel rusting. I will have to check that out.

 

[kelltym88]

Phred,
Why not just take a centering ring and some left over balsa, trace the CR and cut out 2 pieces. Glue one side to the CR, maybe add a little "chore boy" to the middle, glue the other balsa piece to the other side and viola!! Coat it with some epoxy,let it dry, drill it with a few holes using a 1/16" drill bit, or maybe 1/8" and now you've got a baffle. Maybe even glue 2 CR together to get a little more space.