New baffle design. Want your ideas.

[CZ Brat]

Hey guys. I am a fan of baffles. I like the idea of using engineering to remove a manual step or consumable product. I know that baffles add more wieght to rockets than wadding, dog barf or chute protectors. But I also like the idea that I only have to design/build it right once, it will be right launch after launch, unlike the other methods that require me to do it right each launch. So with that said, here is my idea for a short 3" rocket with 29mm mount to use big F - baby H.

Here are the design pics to start


So the MMT is 1" longer than the longest motor I plan to use (Rouse Tech 29/180). At the top is a slot that is 1" long and 60 degrees wide (width between the plates). There are 6 plates, (1) 4" x .86" x 1/8" balsa and (5) 3" x .86" x 1/8" balsa. Distance between the CR and bulkhead is 4". The 4" plate is next to the slot in the MMT and the 3" plates alternate between touching the Bulkhead and the CR. The Bulkhead has a slot that is .86" (distance between MMT OD and BT ID), by 60 degrees. It is located next to the 4" plate on opposite side from the slot in the MMT.

Ejection gasses come up the MMT, hit the bulkhead and do a 180 going down between the MMT OD and BT ID with the 4" plate on one side and the 3" on the other side. 3" down it's path, the short plate stops. The gasses hit the CR and do a 180 and go up till they hit the bulkhead and get re-directed downward again. This continues till the gasses make their way back to the other side of the 4" plate. They are heading upward at this point. At the top, there is a cutout in the bulkhead which allows them to go upwards and push your chute out.

The gasses make 6 180s in their path. Their is a large volume of cool air they have to push ahead, and thus pressurize, before they leave the baffle system. Since most of the baffle is located lower than the end of the motor, this saves linear space, which is really important in shortys like what I am looking to build.

Soooooo.....

Think it will work?
Ever seen it before?
Ideas, suggestions, input?

 

[Estesbasher]

I think you've got a good Idea CZ. Now say it's a 3" rocket what if you moved this down into the fin can. Say ues a 2.65 tube and mount the fins to that then you could put the baffle inside of that with the motor mount. Would it work?

 

[CZ Brat]

I think you've got a good Idea CZ. Now say it's a 3" rocket what if you moved this down into the fin can. Say ues a 2.65 tube and mount the fins to that then you could put the baffle inside of that with the motor mount. Would it work?

I am planning on using fin tabs. How would that work? Also, since this design is onle 1.25" higher than the top of the biggest motor I plan to use, what would be the gain?

 

[Estesbasher]

I was just thinking instead of this sitting above the fins. Just move it down into the fin can. Guess you could always use the fin tabs for the baffle. For a short rocket.

 

[Handeman]

I wouldn't bother with 6 180º turns, one would do, of course with this design you have to have at least 2. I wouldn't use balsa either, unless you are going to coat it with epoxy, high temp paint or something to make it last longer under the heat. The face of the CR that the MMT is glued to will also have to have some kind of coating to prevent it from burning away.

Remember, it's not really the hot gases that you need to prevent from reaching the recovery, it's the burning particles of BP. A simple S turn in the path of the gases is usually all you really need. The more serpentine you make the baffle, the more back pressure you get that tries to blow your motor back out of the rocket. You could use three 1" slots in the MMT, six 1" plates from the top CR on either side of the slots, and then three notches in the CR so the gas turns back down, then back up and out. It would be lighter and just as effective. It would also make the baffle only 2" long and should put it above any fins that you might want to mount through the wall.

Just my :2:

 

[powderburner]

I wouldn't bother with 6 180º turns....[snip].....the baffle only 2" long and should put it above any fins that you might want to mount through the wall.

What he said

 

[thobin]

While your baffle is cool and will work, it is way over complicated I have found that ejection gas has to change directions only once or twice to cool it down enough to be safe on parachutes. I have spent the better part of the last year trying new baffle designs. Most of them have worked flawlessly and one worked it just didn't last long before some of the baffle tubes blew out. although it was used in a HPR situation, and it was not made to withstand the higher amount of BP that is usually associated with HPR, the same baffle works very well in all my LPR stuff.

The best configuration I have used is the half moon bulkhead, its the simplest and the most bullet proof I have tried. The coupler is only 3" long and you just alternate each of the half moon bulkheads. You just need to give the whole thing a good coat of epoxy on all the bulkheads and inside the coupler and its good to go. Sometimes can be added to a already completed rocket, I have inserted several of these in rockets that where already built. It makes a great place to anchor your shock cords to as well.


TA

 

[CZ Brat]

While your baffle is cool and will work, it is way over complicated I have found that ejection gas has to change directions only once or twice to cool it down enough to be safe on parachutes. I have spent the better part of the last year trying new baffle designs. Most of them have worked flawlessly and one worked it just didn't last long before some of the baffle tubes blew out. although it was used in a HPR situation, and it was not made to withstand the higher amount of BP that is usually associated with HPR, the same baffle works very well in all my LPR stuff.

The best configuration I have used is the half moon bulkhead, its the simplest and the most bullet proof I have tried. The coupler is only 3" long and you just alternate each of the half moon bulkheads. You just need to give the whole thing a good coat of epoxy on all the bulkheads and inside the coupler and its good to go. Sometimes can be added to a already completed rocket, I have inserted several of these in rockets that where already built. It makes a great place to anchor your shock cords to as well.


TA

Thanks.

Here is the one I put into my Leviathan. It was built into the coupler. The CR is not shown, but about .75" below the baffle tube. I haven't flown it yet, but am confident in the design. What do you think?

 

[thobin]

Simple and it will work. Looks great.

TA

 

[shrox]

A piece of something like Chore Boy metal scouring pads work well as a heat sink, but do not use steel wool. It burns.

 

[CarVac]

Hey guys. I am a fan of baffles. I like the idea of using engineering to remove a manual step or consumable product. I know that baffles add more wieght to rockets than wadding, dog barf or chute protectors. But I also like the idea that I only have to design/build it right once, it will be right launch after launch, unlike the other methods that require me to do it right each launch. So with that said, here is my idea for a short 3" rocket with 29mm mount to use big F - baby H.

Here are the design pics to start
View attachment 125306View attachment 125305

So the MMT is 1" longer than the longest motor I plan to use (Rouse Tech 29/180). At the top is a slot that is 1" long and 60 degrees wide (width between the plates). There are 6 plates, (1) 4" x .86" x 1/8" balsa and (5) 3" x .86" x 1/8" balsa. Distance between the CR and bulkhead is 4". The 4" plate is next to the slot in the MMT and the 3" plates alternate between touching the Bulkhead and the CR. The Bulkhead has a slot that is .86" (distance between MMT OD and BT ID), by 60 degrees. It is located next to the 4" plate on opposite side from the slot in the MMT.

Ejection gasses come up the MMT, hit the bulkhead and do a 180 going down between the MMT OD and BT ID with the 4" plate on one side and the 3" on the other side. 3" down it's path, the short plate stops. The gasses hit the CR and do a 180 and go up till they hit the bulkhead and get re-directed downward again. This continues till the gasses make their way back to the other side of the 4" plate. They are heading upward at this point. At the top, there is a cutout in the bulkhead which allows them to go upwards and push your chute out.

The gasses make 6 180s in their path. Their is a large volume of cool air they have to push ahead, and thus pressurize, before they leave the baffle system. Since most of the baffle is located lower than the end of the motor, this saves linear space, which is really important in shortys like what I am looking to build.

Soooooo.....

Think it will work?
Ever seen it before?
Ideas, suggestions, input?

Sounds shockingly like my L1 rocket, right up to the "only just barely fits a 29/180" part.

The only difference is that I only made the air do a single 180. Only two longitudinal baffles were necessary, and I never once scorched a chute.