Use of Baffles and cleaning

[Orestes Mayo]

Hello. I am looking at the use of baffles as a new thing. I have a few things I am not sure about. First and foremost, if your baffle is inside your BT well down inside, and what I have seen is pople place a brillo inside to take the burn; how do we clean the residue? After some usage it needs to be cleaned and if used long enough, replaced. Is there a tool or method?

Thanks.

 

[T-Rex]

A hook of some sort. There really isn't anything commercially made for the purpose, so you are on your own. A piece of coat hanger wire with a hook in the end long enough to reach the stainless wool works if it isn't too tightly crammed in the holder.

Personally if I am going to use a baffle, it is generally the 2/3 moon style (mount 2/3 bulk heads with the opening alternating, with a minimum of 1/2 inch between them a minimum of 2" from the end of the motor.) Don't have a photo available. Sorry. My circle cutter has a 1/4" center drill, so I use a 1/4" dowel to glue the stack of "discs" together then install it as a unit. Most build with 3 discs, but I usually use 4. (If 3 is good, 4 must be better, that's just me.)

 

[Orestes Mayo]

A hook of some sort. There really isn't anything commercially made for the purpose, so you are on your own. A piece of coat hanger wire with a hook in the end long enough to reach the stainless wool works if it isn't too tightly crammed in the holder.

Personally if I am going to use a baffle, it is generally the 2/3 moon style (mount 2/3 bulk heads with the opening alternating, with a minimum of 1/2 inch between them a minimum of 2" from the end of the motor.) Don't have a photo available. Sorry. My circle cutter has a 1/4" center drill, so I use a 1/4" dowel to glue the stack of "discs" together then install it as a unit. Most build with 3 discs, but I usually use 4. (If 3 is good, 4 must be better, that's just me.)

Thank you. I will look at that one too.

 

[SolarYellow]

One thing I'm kind of surprised I haven't seen much/any of is baffles with serviceable or replaceable elements.

For example, if one was to put a baffle at the top of a stuffer tube, it would be pretty straightforward to use something like an Estes threaded motor retainer on the front of the stuffer tube and make the baffle element a cartridge, so it could be replaced or taken out for cleaning as needed just by unscrewing the retainer cap.

 

[jmasterj]

One thing I'm kind of surprised I haven't seen much/any of is baffles with serviceable or replaceable elements.

For example, if one was to put a baffle at the top of a stuffer tube, it would be pretty straightforward to use something like an Estes threaded motor retainer on the front of the stuffer tube and make the baffle element a cartridge, so it could be replaced or taken out for cleaning as needed just by unscrewing the retainer cap.

You'd have to be able to reach the retainer cap with something. I imagine most baffles don't need any work before the rocket is lost or retired due to damage.

 

[mh9162013]

One thing I'm kind of surprised I haven't seen much/any of is baffles with serviceable or replaceable elements.

For example, if one was to put a baffle at the top of a stuffer tube, it would be pretty straightforward to use something like an Estes threaded motor retainer on the front of the stuffer tube and make the baffle element a cartridge, so it could be replaced or taken out for cleaning as needed just by unscrewing the retainer cap.

Baffles can be made to be removable:
https://www.rocketryforum.com/threads/my-removable-bt-20-baffle-system.174561/

@Orestes Mayo: what size of motors are you using?

 

[mh9162013]

You'd have to be able to reach the retainer cap with something. I imagine most baffles don't need any work before the rocket is lost or retired due to damage.

That's probably it. You can make them to be removable, sometimes fairly easily. But for most people flying LPR/MPR rockets, it may not be worth the added effort. Still fun to do if the rocket's structure allows for it.

 

[KennB]

Also, don't use steel wool in the baffle; it will burn and damage your rocket.
Find the stainless steel scrubbers made from flat ribbons. Even with this, you should test it for flammability.

 

[Dane Ronnow]

I took an Apogee BT-80 baffle and added two short tube sections inside—BT-70 on the upper plate (left in the photos), and BT-55 on the lower plate (right in the photos), attached with J-B Weld. The idea is to restrict the hot ejection particles to the baffle interior while still allowing the free flow of ejection gas/pressure. The BT-55 chokes the flow of particles so they enter the BT-70, where they are blocked by the center of the upper plate.



As far as cleaning, it's a simple matter of inverting the body tube after recovery, and shaking the trapped particles out the top. I doubt the build up of soot on the walls of the baffle would be a problem before this rocket hits the end of its life, so I don't worry about that.

The baffle also serves as a tube coupler. This is a BT-80, single-stage rocket using motor ejection for single deployment.

 

[Buckeye]

I took an Apogee BT-80 baffle and added two short tube sections inside—BT-70 on the upper plate (left in the photos), and BT-55 on the lower plate (right in the photos), attached with J-B Weld. The idea is to restrict the hot ejection particles to the baffle interior while still allowing the free flow of ejection gas/pressure. The BT-55 chokes the flow of particles so they enter the BT-70, where they are blocked by the center of the upper plate.

View attachment 635261 View attachment 635262 View attachment 635263 View attachment 635264 View attachment 635266 View attachment 635267

As far as cleaning, it's a simple matter of inverting the body tube after recovery, and shaking the trapped particles out the top. I doubt the build up of soot on the walls of the baffle would be a problem before this rocket hits the end of its life, so I don't worry about that.

The baffle also serves as a tube coupler. This is a BT-80, single-stage rocket using motor ejection for single deployment.

I like this idea. It is kinda like the baffles with 2 parallel tubes forming a Z-shaped air path, but this is easier to construct.

 

[Rocketholic]

There are some great ideas for baffles here! Thanks everyone.

I recently rebuilt a rocket using BT-55 tubes. The original had more of a payload fence than a baffle about halfway up the tubes (~11" tubes not including the plastic motor can and the nose cone).
In similar fashion, I made a payload fence/baffle out of a tube coupler and a piece of 1/8" ply I had in the "not ready to throw this away yet" bin. After I drilled and sanded/filed the edges I made sure it fit well enough in the coupler. Before gluing it in the coupler, I coated both sides with a thin layer of 5 or 15 min epoxy to help the wood resist combustion from the motor ejection charge. (Plus, If I feel like it, it should be easier to clean with a swab on the end of a stick.) Once the epoxy was dry, I glued it in the coupler and assembled the tubes per my design. It was easy enough to run the thin Kevlar cord through the baffle and down to the motor mount where it was permanently affixed.
I did something similar in my BT-80 tubed MPR. The fence/baffle is just a 29mm centering ring with some extra holes drilled in it and some bamboo skewers across the 29mm hole. Works great! You can see the foil tape lined section that is beneath the baffle to help prevent the cardboard from burning due to the pyrotechnic deployment charge. The foil tape works as designed and very well at that (It is for metal duct-work sealing).
Having experienced the benefits of the payload fence/baffle I will have one in every rocket from now on - if possible.