Estes D/E's - CATO issues?

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Jun 5, 2009
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During my previous return to rocketry 10 years or so ago, as I recall at the time there were some significant problems with chronic CATOs in Estes D and E engines.

This was something of a surprise to me - in my original rocketry life back in the early 1970s, I don't think I ever remember a CATO - in fact, we didn't even have a word for it back then. It was just taken for granted that the engine was basically gonna work.

But, when I got back in the game in the early 1990s, I did start to launch some D's and Es, and sure enough, one of the E's blew out the casing and blew the guts out of a Goblin.

We were able to install a new motor mount and salvage the bird, but that definitely gave me pause on the idea of flying other models on those engines.

Following rocketry from a distance for the decade in between, I gathered there had been some problems with the D and E engines. How reliable are the D's and E's these days?
Flown a bunch of both, never had a problem. Did have a problem getting one to ignite once, but turns out it was a bad igniter.

Back in the early 70's Estes came out with the D-kaboom-13 motors (ok, maybe the editorialized "kaboom" was unneccesary, but... :) )

Their solution to that problem was to tone down the motor to a D12

Same with the E motors. In the timeframe you are talking about (early 90's), Estes was selling the E15 black powder motors and they were notorious for CATO's. Their solution is the E9 (much more reliable)

hope this helps
D12's are very reliable, I perfer to fly D clusters over AP motors ANY time. If stored and handled properly they and all bp motors, can last 40years and still work fine while being as reliable as your brand new BP motors. As Jim mentioned the E15 bp motors did have a problem remedied by reducing the pressure to come up wtih the E9 which has been doing very well. Don't be afraid of and occasional CATO, they are very infrequent unless you mishandle (mainly Heat cycle) our motors.

OBTW more D-E catos will be seen durning very cold winter launch weather than during the summer. but still very few and far between. Sorta like my "which came first Egg w/ Chicken" Odd-Roc flight attempt on a very cold Feburary day. Ended up with Scrambled Egg and Fired Chicken:D but flew again great later on a snow covered field.
I;ve found on those very cold launch days, if your motor(s) is/are very cold stick it/them in a pocket for awhile before installing in the model at the pad.
My guess at failure rates for Estes D and E motors would be somewhere down in the very small percentages (1-2%?)

Back in the late 60's and early 70's we had a few problems with D13s, but you never really knew for sure whether it was actually a motor failure or if one of your competitors (friends?!?) snuck into your range box and 'helped' the motor. Overall the D13s were still pretty reliable.

In my experience the 'modern' Estes D12 motors are very reliable, I think I have only seen a problem with one or two of those. Estes E9 motors have done very well for me, I don't remember any problems.
i had an E9 cato on me once, out of countless hundreds of flights with them. but i think it was due to mishandling, i dropped that package on my cellar floor accidently. maybe the grain cracked in that motor...regardless, shredded my scratch built rocket.
Only problem with D12's I've noticed is an overly agressive ejection charge. I've had zero problems with E9's.
yes, that D12 has an insane ejection charge. one time, someone flew a scratch rocket that was SUPER unstable, the thing tumbled through the air and then lawn darted about 2 feet from me, then the ejection charge went off, not only did the body and nose cone seperate, but the motor came screaming out the back end and hit a little girl in the leg, as it proceeded to the ground on fire. overkill? yeah, i'd say so....