This is the first baffle system I remember, introduced by Centuri in 1971. CLICK HERE
A coupler with two punched disks glued on either side.
Very simple and effective, far easier than the ejection system used in the Estes Bandit.
In the drawing, the engine would be down to the left of the lower flat plate. On the lower plate the holes are punched closer to the center.
To the right upper side, the plate has the holes punched to the outside edge.
Now that the JimZ site is back I was able to check the Centuri Long Tom instructions.It looks like the lower plate evolved into a centering ring with a single larger hole in the center. The smaller holes remain and circle the outside of the upper ring.
I'm wondering about the use of wadding with baffles. Is it still necessary? I've seen claims both ways. I use a little wadding with a baffle, "just in case". Any opinions?
ReplyDeleteHi BAR,
DeleteYou shouldn't need any wadding when a (correctly installed) baffle is used. I've used them without wadding and there is no melting or burns in the parachute. Many use a little wadding with a baffle for extra protection, just in case!
One annoying feature of the ejection ducting system in the Estes Bandit is its tendency to trap the particulates -- before long your rocket ends up sounding like maracas.
ReplyDeleteHi Naoto,
DeleteInteresting, I found the same thing in my Centurion. I never built the Estes Bandit. In the Centurion I could shake it and hear the crud still left inside.
An ejection baffle works very well in a rocket long enough for it to fit, like the Long Tom. My brother put a baffle in his Red Max in 1973. Unfortunately, the Max's body tube was so short he had to put it very close to the motor mount in order to still have room for the parachute. The 'chute still got singed and the bottom disc of the baffle eventually burned out. I tried a balsa version of a baffle in a short rocket long ago and it also burned through. Then I tried one in a long rocket and it worked perfectly.
ReplyDeleteHi Lonnie,
DeleteThat mistake has been made by quite a few. The baffle also has to be closer to the nose end for C/G reasons. I had a baffle in my Semroc Centurion. After 15 flights (and too many dings and repairs) I cut open the rocket to see the baffle. the bottom thick card stock plate (closer to the engine) had soot on it but no burns! The soot buildup actually insulated the punched ring from more damage.
I should say, I coated the punched disks with white glue to protect them. The instructions recommended to do that.
http://modelrocketbuilding.blogspot.com/2013/01/centurion-autopsy.html