BP power trying to make estes E motors

[layedbackkustomz]

ah the estes i remember the days. i tryed to replicate it at first with 75/15/10 and it was a core burner and i learned real quick that it was to hot of a fuel. then i moved down to a 60/30/10 and i was golden. then i got cert. from tripoli and i made some motors but i sayed the hell with adding ejection charged and use a altimiter to pop a 1g bp ejection charge at 1000 ft. the peoblem with a E motor is you wull have to build the ejection charge into the motor like i had to do with my c motors. and instead of a end burner i think you should try doing a core burner and tweaking the delay comp. but thats just my 2 cents.

[stckmndn]

the NAR does not allow motor manufacture, however, tripoli rocket association does allow it...the catch is you have to be Lvl 2 certified (which means basically you are proficient enough to build and fly and recover a rocket under power of a J class motor safely. the Lvl 2 certification covers motors in the classes J, K, and L. once you have proved you are proficient with such motors, by passing the extensive written "exam" for the Lvl 2 certification, (it aint that easy unless you've been studying FWIW) you can then build and fly motors of any size up to L. and a Lvl 3 certification covers M class and above (the sky is truly the limit...no pun intended). you can then build motors in the M class, N, O, P, Q, R, S...etc...the largest amateur rocket motor IIRC was an S motor built by CSXT in their space shot. once you start putting together APCP or PBAN in those quantities, you've got yourself one hell of an expensive hobby.

 

a model rocket is a rocket which is designed to fly under thrust of a motor, and be recovered fully in-tact. although they use the same propulsion systems in design (mostly in regards to BP motors), the difference is that a "firework" is designed to produce some sort of pyrotechnic visual, or audible effect, where a model rocket is not.

 

2 or 3:1 is not a safe thrust:weight ratio. unless your rocket is supremely stable, an errant breeze, or rod whip, or just the weight of the backend of the rocket, will send it sideways and into undesirable paths of travel. you're looking for a 5:1 initial ratio. this can be achieved by lengthening the core of the motor. a core burning motor has a higher initial thrust than average thrust, so even if your average thrust is 2-3:1, that will work to "sustain" (hence the reason an upper stage in a multistage rocket is called a sustainer) the initial momentum gained by the initial thrust provided. your initial thrust could be 5:1, 6:1, 7:1...it's all in how you design it. there's a lot more to designing a functional motor *properly* than you think. although, given what we know about the ISP of black powder in general, you know what the potential for your motor is as soon as you weight the propellent. from there you can tailor it to burn extremely slow and produce very little thrust for a very long time, or a lot of thrust for a little time. most estes motors achieve a good middle ground. the thing to realize is that 60g of propellent is 60g of propellent. you could make it lift a light rocket and go extremely high in the sky, or you could make it lift a heavy rocket and go really low...it's all in how you design the core.

 

Wow. Thank you very much for that.

[WSM]

My greatest end-burn success came with a 4:1 ratio of tube ID to nozzle throat. I've used commercial meal powder with such a configuration to successfully duplicate model rocket engines. On a load cell they had a regular thrust curve identical to those of Estes engines. I believe Estes uses commercial powder (FFFFa if I'm not mistaken) and upon investigation of a "B" class engine taken apart I could see the impression of the grains in the nozzle clay when I broke the nozzle off the powder grain.

 

Try it and see.

 

WSM