29/40-120 Forward Closures

[kelltym88]

I'm looking to replace my forward closure for my AT 29/40-120, but I'm having the darndest time finding a place that has one. Maybe I'm just not loking in the right place. Thanx for your help.

 

[rocketsonly]

Are all Aerotech 29mm foward closures built the same? If so, I might be able to help. Email me at [email protected]

 

[Johnnie]

The Consumer use 29/40-120 motors are different from the HPR 29mm reloadables. These parts are not interchangeable between the two styles.

 

[BlueNinja]

Performance Hobbies might have them. I'll post back if they don't.

 

[kelltym88]

Thanx Blue_Ninja, Performance hobbies has it.

 

[lalligood]

I personally have never seen parts for the 29/40-120 casing sold separately...

Your best bet might be to try contacting AeroTech direct! They are very good about handling warrantee issues. I bet they'd sell a part like that too...

HTH,

 

[n3tjm]

Aerotech does sell them seperatly. They do that so people can replace a forward closure due to a blow bye. What happened to your forward closure? Glad you were able to find one

 

[kelltym88]

I loaded the delay element wrong. The spacer should have been between the delay and the composite, I turned it over and loaded it with the delay right up against the composite(it was a G64-4). The igniter is pushed up all the way up as far as it could go. It ignited and lifted off OK , but at the top of the launch rod the ejection charge went off and thru the rocket into a tumble. The motor shot out the back and hit the ground burning out of both ends and spinning like a twirly firework, after a short pause it shot off towards an umbrella and bounced off of it into the back of someones hatchback. See the 2.66 Photon Disruptor thread for all the details. Fortunately no one was hurt. After examining the casing I noticed that the intense heat had melted away the very top of the closure where the ejection charge is poured in .

I'm planning on flying it again at ROC Stock, which is also our TDD here in Ca.

 

[n3tjm]

Common mistake. I supervise the assemble of numerous reloadable motors, and for some reason, the spacer end seems to be attracted to the delay well first.... its like butter on toast is attracted to the floor... Of course, I correct their mistake before its to late .

 

[BlueNinja]

May I ask why that doesn't work?

 

[kelltym88]

I will try to explain blue:
Reloadable motors have a slit all along the grain. When assembling a reload the igniter is pushed thru this slit as far as it can go, thus making the igniter almost at the top of the motor. Unlike the normal BP motors which ignite from the bottom, APCP motors burn differently. By placing the delay element with out the spacer next to the grains, when the igniter ignites, it will also ignite the delay grains. The spacer is just small enough to prevent that from happening upon ignition. I hope I've explained that well enough. Go to Aerotech's website and watch their video on how to load a 29mm motor.

 

[BlueNinja]

I've built reloads before. I was just wondering why orientation of the delay would cause an early ejection.

 

[n3tjm]

Simple. Take a look at the attached drawing. The area in read is where the hot gasses of motor firing leak. Notice how above the delay grain, there is no way the hot gasses can bypass the o-ring. Will, if the delay grain is inserted backwards, the hot gasses can leak between the dealy grain and spacer. Those gasses are hot enough to ignite black power... and the amount of powder in that area would give conciderable force witch may contribnit to blowing the top off the closure. One the gas finds the breach - the delay grain is quickly, almost instantly, consumed by the pressueres - and results in the rocket being roasted.

 

[BlueNinja]

OK, I get it now.