My Removable BT-20 Baffle System

mh9162013

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Here’s the write up I alluded to earlier today in this thread.

I’m currently working on BT-20 rockets, such as the Estes Yankee and Wizard. I’m also learning to really appreciate baffles. No, I don’t think they’re perfect and I still use 1 piece of disposable wadding as some charred bits occasionally get through the baffle and I want to do everything I can to avoid a melted parachute. This is particularly true when the ejection charge doesn’t fully blow through the clay disc and instead jets out from a tiny hole in the clay disc. But I know baffles suffer from some serious wear and tear during normal use. I also know that LPR rockets have certain weak points (whether or not a baffle is used). So I decided to create a baffle that would help protect the rocket’s main airframe in addition to being removable.

Why did I want it to be removable? Two reasons: the ability to inspect it easily and the ability to replace it. Most LPR baffles are permanently installed with glue. Depending on how they’re installed (such as with a coupler joining 2 main body tube pieces), they can be replaced without too much effort. But I wanted a baffle that was literally “pop out and pop in.”

Another objective for this baffle system was to make it using materials and tools that any LPR rocketeer is likely to already have with them. In other words, the only “cost” to this baffle system should be the builder’s time. I know, I know, baffles are cheap. But a dollar saved is a dollar earned. And more importantly, it feels great to take “junk” that’ll just get thrown out or stored away and put that junk too good use.

So, to summarize, this baffle system will:

1. Be removable for inspection and eventual replacement
2. Increase the durability of an existing rocket
3. Be capable of being made for almost nothing (money-wise)

The Baffle Itself

Let’s begin with some pictures:

Use 1.jpg
Use 2.jpg
Use 3.jpg
Use 5.jpg
Use 6.jpg

As you can see, it’s a tried-and-true half-moon design. My baffle uses 3 half-moon pieces. If you have at least 1 spent 18mm BP engine, everything else you need (besides glue) to make this baffle is included in an Estes Yankee or Wizard kit.

The coupler is the yellow engine spacer tube. The half-moon pieces come from the left over balsa from the fins (1/16” thickness, if I recall). The center support rod is just a sliver of balsa that’s about 33mm long and came from the left over balsa for the fins. And the thrust ring came from an old Estes 18mm BP engine. I reduced its diameter by peeling away a few layers of the outside and JB Welded it in to the bottom of the baffle (the part that touches the top of the engine).

To help protect the baffle from heat/flame as well as increase its structural strength, I papered both sides of the 3 half-moon pieces with regular 20lb copy paper and wood glue. I covered 1 side of the 3 half-moon pieces with JB Weld (the side that faces the ejection charge). I also used a little bit of white glue to coat the inside of the yellow engine spacer tube in the dead space area between the first thrust ring and the first half-moon piece. This dead space area is the area that should be at least one body tube diameter long and separate the top of the engine from the beginning of the baffle.

Here are the specs of this particular baffle system:

Diameter: 18mm
Length: 52mm (or 53mm?)
Weight: 3.5 grams (this is what it weighs after 8 test launches)

The total amount of dead space (the distance from the first thrust ring that touches the top of the engines) to the first half-moon baffle piece is about 20mm. Ideally, you want this as long as possible, but 20mm seems to work so far (at least with A8-3 engines…more on that later). The following drawing will help put things in perspective:

Use 7.jpg

The three half-moon pieces from end to end contribute to about 33mm in the total length of the baffle. Again, ideally you want a bit more space between these pieces to improve longevity of the baffle and increase the amount of cooling of gasses and particles, but this design works so far. And remember, this baffle is designed to be easily replaceable, so making the baffle smaller, yet reducing the life of the baffle is a worthy trade off in my opinion. The only question is, how much life do you need from your baffle?

What Makes the Baffle Removable?

Simple, you just glue a second thrust ring into the main body tube that the top of the baffle presses against and you don’t glue in the baffle. So you have the engine which presses against the bottom of the baffle (which has a thrust ring built into the bottom). The top of the baffle then presses up again the second thrust ring. You can then either tie your shock cord to the baffle itself (like with a typical baffle) or the second thrust ring (that’s what I did in my Wizard, which I used to test this baffle design). Here’s a picture to help illustrate:

Use 8.jpg

From left to right you have the engine, the baffle, the second thrust ring, the shock cord and finally the parachute. The friction-fitted engine keeps the baffle from falling out the back of the rocket. The second thrust ring towards the top/front of the rocket prevents the baffle (and engine) from shooting forward to the nose cone.

How Does it Perform?

I’ve done 8 ground tests so far, and it’s worked perfectly. Here are a few before and after pictures of the baffle as it progressed through the 8 tests. The pictures at the top are when the baffle was new and the pictures at the bottom are after 8 test launches. You can find a few more pictures in the “teaser” post I made earlier today and linked to at the beginning of this post.

Back and Front New through L8.jpg

Main New through L8.jpg

Based on what I see after 8 tests, I think the weakest point is the yellow spacer engine tube and the primary force affecting the life of the baffle is the heat/flame, not the pressure. You can see some brown spots forming on the outside and when you press on them, they feel a little weaker than the other parts of the baffle. Adding some extra JB Weld to coat the inside walls of the yellow engine spacer tube will probably help, but it will probably add about 1-2 grams of weight. Is it worth it? Well, this baffle is designed to be removable, so is it worth the performance cost of the added weight? Only you can answer that question.

As for the center support rod and half-moon pieces, they show no signs of weakening. I may try using a small brush and scrape away some of the built up “gunk.” I don’t want to remove too much as I feel they provide a protective coating to the baffle. But if there’s too much build up, it’ll hinder the gas flow through the baffle making it less effective.

More in the next post...
 

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mh9162013

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Advantages of This Removable Baffle System

1. It’s free with purchase of an Estes Yankee or Wizard (for most of us who build LPR rockets regularly)
2. It’s lightweight, at about 3.5 grams (remember, this weight includes the built in thrust ring and the additional materials to create the dead space added in front of the baffle itself).
3. It’s removable, so you can inspect it after every flight and replace it when you see signs of fatigue or potential failure.
4. It reinforces one of the weakest parts of the rocket: the main body tube just above the top of the engine, next to where the ejection charge originates.
5. You can make it out of many different materials. You could make it stronger (and heavier) by using a toothpick or metal tubing (like brass or aluminum) for the center baffle rod support, cardstock or plywood for the half-moon pieces and using epoxy to coat more of the inside of the baffle (such as the center baffle rod support and inside walls of the yellow spacer engine tube). This will add a lot of weight, though. My earlier design that’s been installed in the Yankee uses more JB Weld to coat everything inside the baffle, uses a brass center support rod and the half-moon pieces are made out of particle board you find at the back of picture frames. Is it much stronger? You betcha. Is it much heavier? You betcha, at almost double the weight of 6.5 or so grams.

Disadvantages of This Removable Baffle System

First, if your engine pops up during ejection (it wasn’t properly installed with masking tape or w/e other friction system you use), it’s possible for the baffle to fall out of the rocket while it’s descending after ejection. One way to prevent this is to add some tape or glue some paper shims to the side of the baffle so it is more likely to stay inside the body tube, yet can easily be pushed out with a small rod. If it does fall out during a flight, at least it was designed to be replaced and it’s really light (far lighter than a spent 18mm BP engine casing).

Second, it adds extra weight to the rocket in the form of a second thrust ring and the material needed to create the dead space (and reinforce the main body tube). It’s not much extra weight (maybe 1-2 grams), but for a rocket that originally weighs 15 or so grams, that’s not inconsequential.

Third, you’ll need to find a second thrust ring from somewhere. I used part of an old spent engine casing and just peeled away a few layers of paper on the outside. Alternatively, you could use some long strips of paper (maybe about 3-4 mm wide) and glue it to the inside rim/edge of the yellow motor spacer until sufficient thickness has been built up. You’ll also want to coat it with some wood glue or epoxy.

Fourth, the design (as of now) only works with minimum diameter rockets. A conventional MMT that’s glued into the main body tube would prevent the baffle from sliding out the bottom of the rocket. With a BT-50 or BT-60 main body tube, there might be away around this with all the extra space that’ll be available to create some sort of “twist and lock” mechanism.

Future Question(s)

All 8 of my tests were done with A8-3 engines. This means the ejection charge originates in the bottom half of the engine casing. If I used a C6-5 engine where the ejection charge occurs further up the engine case, would this particular baffle last as long? Probably not.

But how many fewer flights would I get? I’ll do some testing (and/or flying) and find out soon, as I don’t have any C engines right now. To compensate, I think lengthening and reinforcing the dead space would be a good idea. But in a rocket like the Yankee or Wizard, there’s not much additional space available (for me, it may be 5-10mm as I need space at the top of the rocket for my altimeter and/or payload bay). But if you don’t need space for a payload bay or altimeter, or you’re building a taller rocket than a stock Wizard or Yankee, then adding an extra 10+mm of dead space shouldn’t be an issue.
 

smstachwick

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The thought and work you put into this system is clearly the result of much thought. I consider it highly innovative and worth at least trying. Whether it will gain widespread acceptance remains to be seen, but I can see that it’s novel and has a great deal of potential.

I would be interested in seeing how well it works for rockets other than minimum diameter, Perhaps a rocket could incorporate this system in a lengthened motor mount tube, with both a motor and the baffle inserted similarly to the spacer arrangement that Estes uses to make some of their E12 rockets flyable on C11/D12 power.

If I end up ordering another MicroMaxx kit I may try it in that, but I also see no harm in trying it G-powered rockets or larger, so long as you’ve got at least one motor ejection.

(Minor edits)
 
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mh9162013

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I would be interested in seeing how well it works for rockets other than minimum diameter, Perhaps a rocket could incorporate this system in a lengthened motor mount tube, with both a motor and the baffle inserted similarly to the spacer arrangement that Estes to make some of their E12 rockets flyable on C11/D12 power.
That's a great point. The removable baffle system could potentially work in a rocket that uses those spacers, or a even a stuffer tube, like the Citation Patriot.

Hmmm, that's someting I can work on next...
 

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Thanks for sharing this idea. I built a different style baffle and wondered how it will hold up. Now I am going to incorporate your idea to put the baffle I want into a big bertha and I'll be able to see how it holds up after each launch.
 

mh9162013

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cool - how did the recovery system (streamer or parachute/shroud lines) fare with your static ground tests?
The parachute (made out of HDPE plastic from a shopping bag) fared just fine. In 7 of 8 tests, the parachute didn't even get warm and the disposable wadding probably wasn't necessary.

However, in test 3, there was a partial malfunction of the ejection charge of the A8-3 engine and the parachute partially melted (although the shroud lines and shock cord were fine). But this wasn't the fault of the baffle and I discuss what happened in test 3 here.
 

PieroAcme

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Here’s the write up I alluded to earlier today in this thread.

I’m currently working on BT-20 rockets, such as the Estes Yankee and Wizard. I’m also learning to really appreciate baffles. No, I don’t think they’re perfect and I still use 1 piece of disposable wadding as some charred bits occasionally get through the baffle and I want to do everything I can to avoid a melted parachute. This is particularly true when the ejection charge doesn’t fully blow through the clay disc and instead jets out from a tiny hole in the clay disc. But I know baffles suffer from some serious wear and tear during normal use. I also know that LPR rockets have certain weak points (whether or not a baffle is used). So I decided to create a baffle that would help protect the rocket’s main airframe in addition to being removable.

Why did I want it to be removable? Two reasons: the ability to inspect it easily and the ability to replace it. Most LPR baffles are permanently installed with glue. Depending on how they’re installed (such as with a coupler joining 2 main body tube pieces), they can be replaced without too much effort. But I wanted a baffle that was literally “pop out and pop in.”

Another objective for this baffle system was to make it using materials and tools that any LPR rocketeer is likely to already have with them. In other words, the only “cost” to this baffle system should be the builder’s time. I know, I know, baffles are cheap. But a dollar saved is a dollar earned. And more importantly, it feels great to take “junk” that’ll just get thrown out or stored away and put that junk too good use.

So, to summarize, this baffle system will:

1. Be removable for inspection and eventual replacement
2. Increase the durability of an existing rocket
3. Be capable of being made for almost nothing (money-wise)

The Baffle Itself

Let’s begin with some pictures:

View attachment 534322
View attachment 534323
View attachment 534324
View attachment 534325
View attachment 534326

As you can see, it’s a tried-and-true half-moon design. My baffle uses 3 half-moon pieces. If you have at least 1 spent 18mm BP engine, everything else you need (besides glue) to make this baffle is included in an Estes Yankee or Wizard kit.

The coupler is the yellow engine spacer tube. The half-moon pieces come from the left over balsa from the fins (1/16” thickness, if I recall). The center support rod is just a sliver of balsa that’s about 33mm long and came from the left over balsa for the fins. And the thrust ring came from an old Estes 18mm BP engine. I reduced its diameter by peeling away a few layers of the outside and JB Welded it in to the bottom of the baffle (the part that touches the top of the engine).

To help protect the baffle from heat/flame as well as increase its structural strength, I papered both sides of the 3 half-moon pieces with regular 20lb copy paper and wood glue. I covered 1 side of the 3 half-moon pieces with JB Weld (the side that faces the ejection charge). I also used a little bit of white glue to coat the inside of the yellow engine spacer tube in the dead space area between the first thrust ring and the first half-moon piece. This dead space area is the area that should be at least one body tube diameter long and separate the top of the engine from the beginning of the baffle.

Here are the specs of this particular baffle system:

Diameter: 18mm
Length: 52mm
Weight: 3.5 grams (this is what it weighs after 8 test launches)

The total amount of dead space (the distance from the first thrust ring that touches the top of the engines) to the first half-moon baffle piece is about 20mm. Ideally, you want this as long as possible, but 20mm seems to work so far (at least with A8-3 engines…more on that later). The following drawing will help put things in perspective:

View attachment 534327

The three half-moon pieces from end to end contribute to about 33mm in the total length of the baffle. Again, ideally you want a bit more space between these pieces to improve longevity of the baffle and increase the amount of cooling of gasses and particles, but this design works so far. And remember, this baffle is designed to be easily replaceable, so making the baffle smaller, yet reducing the life of the baffle is a worthy trade off in my opinion. The only question is, how much life do you need from your baffle?

What Makes the Baffle Removable?

Simple, you just glue a second thrust ring into the main body tube that the top of the baffle presses against and you don’t glue in the baffle. So you have the engine which presses against the bottom of the baffle (which has a thrust ring built into the bottom). The top of the baffle then presses up again the second thrust ring. You can then either tie your shock cord to the baffle itself (like with a typical baffle) or the second thrust ring (that’s what I did in my Wizard, which I used to test this baffle design). Here’s a picture to help illustrate:

View attachment 534328

From left to right you have the engine, the baffle, the second thrust ring, the shock cord and finally the parachute. The friction-fitted engine keeps the baffle from falling out the back of the rocket. The second thrust ring towards the top/front of the rocket prevents the baffle (and engine) from shooting forward to the nose cone.

How Does it Perform?

I’ve done 8 ground tests so far, and it’s worked perfectly. Here are a few before and after pictures of the baffle as it progressed through the 8 tests. The pictures at the top are when the baffle was new and the pictures at the bottom are after 8 test launches. You can find a few more pictures in the “teaser” post I made earlier today and linked to at the beginning of this post.

View attachment 534330

View attachment 534331

Based on what I see after 8 tests, I think the weakest point is the yellow spacer engine tube and the primary force affecting the life of the baffle is the heat/flame, not the pressure. You can see some brown spots forming on the outside and when you press on them, they feel a little weaker than the other parts of the baffle. Adding some extra JB Weld to coat the inside walls of the yellow engine spacer tube will probably help, but it will probably add about 1-2 grams of weight. Is it worth it? Well, this baffle is designed to be removable, so is it worth the performance cost of the added weight? Only you can answer that question.

As for the center support rod and half-moon pieces, they show no signs of weakening. I may try using a small brush and scrape away some of the built up “gunk.” I don’t want to remove too much as I feel they provide a protective coating to the baffle. But if there’s too much build up, it’ll hinder the gas flow through the baffle making it less effective.

More in the next post...
Great idea mh9 !
I love that solution. Just move ahead the engine thrust ring.
It is very smart. I'm familiar with half moon baffle systems, but to have the possibiliy to replace them it is totally new.
There is always something to learn in rocketry.
Thanks for sharing. :)
 

mh9162013

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Great idea mh9 !
I love that solution. Just move ahead the engine thrust ring.
It is very smart. I'm familiar with half moon baffle systems, but to have the possibiliy to replace them it is totally new.
There is always something to learn in rocketry.
Thanks for sharing. :)
Thank you!

And you're welcome!
 

Back_at_it

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That is absolutely genius for minimum diameter rockets. I have a few Wizards, Hi Fliers Etc. to play with. I need to try this out.

On a side note. I've been kicking around the idea of a removable baffle system for larger diameter tubes. I have the parts to rebuild my LOC Ultimate (4Inch) as a single motor rocket and have been thinking about a baffle that would be held in place with screws thread into the baffle plates. Once done, remove the screws and the baffle comes out. Would be nice to have a baffle to move between rockets.
 

mh9162013

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That is absolutely genius for minimum diameter rockets. I have a few Wizards, Hi Fliers Etc. to play with. I need to try this out.

On a side note. I've been kicking around the idea of a removable baffle system for larger diameter tubes. I have the parts to rebuild my LOC Ultimate (4Inch) as a single motor rocket and have been thinking about a baffle that would be held in place with screws thread into the baffle plates. Once done, remove the screws and the baffle comes out. Would be nice to have a baffle to move between rockets.
If you do try it out, please report back with your results. I plan on doing more testing and flying soon, but still want to hear how this removable baffle system is working for others.

Sounds like your idea could work. In a rocket that big, all that space (and payload capacity) gives a lot more flexibility in how to design a removable baffle system.

I think the only "hard part" in designing any removable baffle system is trying to decide how to balance the competing considerations of performance and longevity.
 

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Great idea. Could you replace the yellow spacer with a piece of rolled up aluminum can? Might solve your burn through problem, and you could make it a little bit longer to give a larger dead space before the gas and particles hit the first plate.

personally I do not think using aluminum can (metal) for this purpose is a violation of the low power model rocket safety code, as I do not think of this is a structural part (As opposed to a nose cone, body tube, or fins, and remember that re-usable motor cases contain far more and far heavier and stiffer metal) although there are those on this form that may disagree.

I also recognize that aluminum is a flammable metal, but generally in the form of a rolled up can while it certainly can ignite, so can a cardboard tube if you keep flame on it long enough which is why you’re getting burned through on your yellow tubes with multiple uses. I would expect the aluminum would last longer. I use it routinely for lining internal ejectable motor pods for rear Eject rockets when I downsize the ”chimney” of the pod, and have never had a problem.
 

mh9162013

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Could you replace the yellow spacer with a piece of rolled up aluminum can? Might solve your burn through problem, and you could make it a little bit longer to give a larger dead space before the gas and particles hit the first plate.

That's certainly an option, but I think I'm going to use a spent 18mm engine casing to replace the yellow engine spacer*.

I will sand/drill out some of the interior to save weight and because a full casing is overkill for a baffle. I've already drilled out a few casings, but it's a bit trickier than you might think, as it's a slow grinding process, then all of a sudden, the edge of the cardboard paper wrap catching the drill bit and the next thing you know, you have a smushed engine casing and a drill that's seized up/stalled with cardboard-paper wrapped around the drill bit.

However, I have ended up with two engine casings to try out. One is about 2.2 grams in weight. It will definitely be more durable than the yellow engine spacer, especially with JB Weld coated on the inside.

The other is about 7.2 grams and is so strong, I'm betting it's durable enough to last for 50+ launches, at least with using an A or B engine.

I'm thinking about coating both of them on the inside with JB Weld and testing them out with C engines. In addition to the different outer material for the baffle, I'm also going to use the entire length of the engine for the baffle. Of the extra 17mm in length, 15 will go to dead space and 2mm will go to the baffles themselves.

The plan with the 2.2 gram case is to get at least 10 launches before it must be replaced. The plan with the 7.2 gram case is to get at least 10 launches before it must be rebuilt. I imagine this would simply require me to drill and sand out the built-up crud inside the baffle, recoatwing the inner walls with JB Weld, then getting another toothpick or balsa sliver and 3 balsa/cardstock half moon pieces coated in JB weld reinstalled inside.

Either approach should still maintain the "free" benefit of the baffle in that it uses materials that most of us have laying around or things we throw away. The only difference is that after 10 launches, how much time we'll have to spend to replace the worn baffle, ie replacing versus rebuilding.

* I still think the yellow engine spacer will work (for at least 10 flights) for the removable baffle system, BUT, it must have its inner walls coated with JB Weld or some other heat resistant glue.
 

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I was just in the shop and I have some balsa machine services coupler stock that appears to be .042 wall which I believe is about twice as thick as the normal Estes tubes. I'm going to give it a try on a Hi Flier I've been wanting to build. Going to be a fun time burning through some A8-3 motors. :)

I typically coat the internals of my baffles with thinned wood glue for fire protection but in this case I might try thin CA and see how that holds up.
 

mh9162013

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Part Two

I just placed an order for a variety of C engines (C6-3, C6-5, C6-7 and C5-3). I will use 1 or 2 of these with a slightly modified version of the above-discussed baffle (we'll the original version, Baffle 1.0). We'll see how well this updated baffle can withstand the ejection charge of one or two C engines (probably a C6-3 and C6-5). But for proper documentation, here are pictures of the outside baffle before the C engine tests:

Combined Baffle 1P1.jpg

You'll note a slight change. That white part is a piece of index card I glued over the part of the baffle with the most severe wear and dark spots from burning bits. We'll call this Baffle 1.1. Besides the addition of this index card reinforcement, no other changes have been made to the baffle. It weighs 3.9 grams.

After I run a few tests with Baffle 1.1, I'll post some pictures and discuss my observations. I will also begin working on Baffle 2.0 where I use the 2.2 or 7.2 gram engine casing to create a more robust baffle (although heavier and longer).
 
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mh9162013

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Baffle 2.0 - Outer Casing

Here are a few pics of the newer version of the removable baffle. It comes from a used A8-3 engine casing and weighs 3.2 grams. The grey stuff inside is JB Weld. Before adding the JB Weld, it weighed 2.2 grams. After adding in the baffles and thrust ring, the total weight of Baffle 2.0 is 5.2 grams (pics will get uploaded later).

20220830_134122.jpg

20220830_134151.jpg

20220830_134159.jpg
 
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Back_at_it

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MH - I'm going your concept a try on a Hi-Flier I'm putting together. Mine will be made from a BT20 coupler sourced from BMS. The internals consist of three plywood plates and a BT5/20 centering ring that has been reduces down to fit inside the coupler.

The inside and outside of the coupler will be coated in thin CA for fire protection and to help it slide in and out of the tube.

1.jpg
 

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Great idea. Could you replace the yellow spacer with a piece of rolled up aluminum can? Might solve your burn through problem, and you could make it a little bit longer to give a larger dead space before the gas and particles hit the first plate.

personally I do not think using aluminum can (metal) for this purpose is a violation of the low power model rocket safety code, as I do not think of this is a structural part (As opposed to a nose cone, body tube, or fins, and remember that re-usable motor cases contain far more and far heavier and stiffer metal) although there are those on this form that may disagree.

I also recognize that aluminum is a flammable metal, but generally in the form of a rolled up can while it certainly can ignite, so can a cardboard tube if you keep flame on it long enough which is why you’re getting burned through on your yellow tubes with multiple uses. I would expect the aluminum would last longer. I use it routinely for lining internal ejectable motor pods for rear Eject rockets when I downsize the ”chimney” of the pod, and have never had a problem.
I placed an aluminum disk from an aluminum can as a "blast shield" on the motor-side of an ejection baffle, it seemed to work great until it came loose (I should have cleaned the aluminum disk glue-side with denatured alcohol, scrubbed with rough emery cloth then re-cleaned with denatured alcohol first before epoxy-ing it to the baffle) and now it just rattles around in the body tube between the engine mount and ejection baffle. But, it may actually help knock sooty debris loose to shake out easier. Next time I'll do better surface prep and use JB Weld instead of "regular" epoxy.
 

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Baffle 2.0 - Outer Casing

Here are a few pics of the newer version of the removable baffle. It comes from a used A8-3 engine casing and weighs 3.2 grams. The grey stuff inside is JB Weld. Before adding the JB Weld, it weighed 2.2 grams. After adding in the baffles and thrust ring, the total weight of Baffle 2.0 is 5.2 grams (pics will get uploaded later).

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wow! I am impressed By how cleanly you holllowed out the casing!
 

mh9162013

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That is a great idea. I think it work work really well with the 18mm Retainer Set from Estes if you wanted to have something besides friction fit.
Absolutely, especially when using the removable baffle in a BT-50 or larger rocket and installing the removable baffle in a MMT that's essentially a stuffer tube. I plan on testing this design out in a near future. Still deciding which rocket to do it in: Estes Patriot or a custom BT-50 rocket (like an Estes Alpha III with a longer main body tube).
 

BigMacDaddy

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This is a cool thread / effort. I have not used buffers but the idea of avoiding worrying about wadding / dog barf is so attractive.

These types of parts really call out to me to 3D design them -- BT-20 sized 25mm (1") tall. Line in middle is for Kevlar to go through but maybe needs to move to outside to avoid burning...Printed in ABS these would hold up fine. Ones on right just had the outer shell removed so you can see inside geometry.

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