I have dealt with model rockets for years and thought I understood the Estes numbering system on their motors. I decided to make one of my 50mm ducted fan jets a rocket powered boost glider. Came time to select the motor and the
D11-P looked to fit the bill. Glider weighs right around 8 ounces all up with motor.They have discontinued that motor. I do not want an ejection charge. While at the hobby store I picked up the NEWEST ESTES catalog. It states that a xx-0 means that there is no delay and NO EJECTION charge. I always thought that xx-0 meant there was no delay in the ejection charge and this is what ignited the next stage on a multi-stage rocket. I picked up a pack of D12-0 motors. Will there be an ejection charge ? The catalog indicates it should not. The reason I do not want an ejection charge is that the motor housing is inside the exhaust tube where the EDF used to sit,and an ejection charge may catch the styrofoam on fire !!

Originally Posted by TipStalled

Will there be an ejection charge ?

There won't be an ejection charge, but hot gas will be coming out the top of the motor near the end of the burn. A "-P" motor is plugged to keep this from happening. WIthout some kind of protection in front of it, I don't recommend using a -0 motor.

After doing some research I came to the same conclusion...don't use the xx-0. I did come up with a work around. My motor tube can be used with a d-class or e-class motor. When using the d-class motor a hollow spacer tube is used. I have epoxied a gaming token to the spacer. It has the same od as the spacer. I will insert the spacer with the token-side down and then the dxx-0 motor . This should keep the gases from escaping into the glider!

Originally Posted by TipStalled

After doing some research I came to the same conclusion...don't use the xx-0. I did come up with a work around. My motor tube can be used with a d-class or e-class motor. When using the d-class motor a hollow spacer tube is used. I have epoxied a gaming token to the spacer. It has the same od as the spacer. I will insert the spacer with the token-side down and then the dxx-0 motor . This should keep the gases from escaping into the glider!

Man,was I wrong !! Launch went beautiful but at the end of the burn a VERY LOUD pop was heard. I had my hands full trimming the glider and got it down fine. Inspection revealed the spent motor casing and engine hook GONE !!I can only theorize that because the spacer just sat on top of the motor it at first held the seal and as the pressure lessened the spacer and motor got seperation(there is about 1/16 wiggle room),this allowed a sudden in rush of fresh oxygen and BOOM large ejection charge !! Next attempt...tape the spacer and motor together !

Try extending the motor tube and providing a safe direction for the gasses to vent. I suspect you over pressurized the tube and it's got to go somewhere....

The '0' in D12-0 means there is no delay charge and no ejection charge either. Its all propellant which when burning to the top simply blows out the top when it gets thin enough that it can't handle the pressure.

I sometimes cheat by removing the clay and the ejection charge from a D12-3 and pouring in a little epoxy over the delay grain. Thats a 'do at your own risk' solution but works as a D11P and E9P replacement.


Richard

Originally Posted by The Tellurian

The '0' in D12-0 means there is no delay charge and no ejection charge either. Its all propellant which when burning to the top simply blows out the top when it gets thin enough that it can't handle the pressure.

I sometimes cheat by removing the clay and the ejection charge from a D12-3 and pouring in a little epoxy over the delay grain. Thats a 'do at your own risk' solution but works as a D11P and E9P replacement.


Richard

That was suggested to me. Just plug the top of the D12-0 with some expoxy !

I personally prefer the motors with a delay grain because I know the delay will hold back the pressure of the motor but booster motors are easier/safer to do. Just test a few to make sure there is enough epoxy.


Richard

Got pic's of the jet/ motor set up?

I just use some epoxy as well. The delay version gives the addition of a bit of tracking smoke to help see it if it is up high....Someone in another forum said they had some fire issue using epoxy that ignited the top of a motor when it got hot as it set, but I don't see how a small bit of 5 minute epoxy could do that....

Frank

Originally Posted by burkefj

I just use some epoxy as well.

How much epoxy do you use?

Probably just about 1/8" deep or so....again I normally do this on a motor with the ejection cap and charge removed, I have not tried doing this on top of an ejection cap so don't know if it would hold that. I do know it will hold up to the ejection delay pressure without the ejection charge...Of course you have to realize you are modifying a motor and normal caveats apply to nar rules and guidelines etc....

Frank

Originally Posted by ccdengr

How much epoxy do you use?

I useed to fly an Estes Astro Blaster at the Dallas Area Rocket Society's old Allen launch site. Never liked the d11p, so i'd fly her with the old Aerotech E-15-W non-reloadables. I would do as described above, break out the clay and por out the ejection charge, but just tape over the end. Never had a problem..except the one time I loaded a complete, non modified motor in her. Looked like I took a SAM up the end, came in smoking, but no damage..
Cash