Estes Motor Evolution....

[Neutrodyne]

It appears from the catalogs I can find online that Estes engines changed in formulation and/or design around 1969 to 1970. While retaining many of the same or nearly the same designations, they went from 23 oz. of maximum thrust to 48 oz. of maximum thrust. The A8-3 for instance changed from a .92 sec burn to a .32 sec. burn. A few changed designations (the B3 became the B14 series...). The only engine retaining the 23 oz thrust was the 1/2A6. Was this a complete reformulation by Estes, different measuring systems or was it simply adopting the Centuri engine formula and design. I note that Centuri rated their engines on AVERAGE thrust, which eliminates a chart-to-chart comparison, but they didn't seem to change the standard A-B-C engines at the same time Estes changed theirs. I have also heard various stories that had Estes supplying just a few early Centuri A-B-C engines, or possibly suppling all of them all along?
I can see that the newer, faster burning engines helped a lot with heavier models. The old motors were lomited to about a 5 oz rocket, even the core burning B3. It seemed pretty clear that Damon wanted to keep Centuri and Estes separate lines with separate identities at that moment (though there were a LOT of competitors at that time - I'd think there were no anti-trust worries like Radio Shack had when they bought Allied....) - though they were homogenized under the Estes name not too many years later.. And then there's the Centuri B series Mini Engine to muddy the waters.....
Any old timers out there? I was only in grade school when all this neat intrigue was going on, so I'm looking back through a mist of roumors, recollections and scanned antique catalog pages.

 

[RoyGreen]

The changes occurred mostly in 1968. Until then casing walls were thicker and the grain diameter was closer to 3/8". The first change was to the B and C motors where the grain diameter was increased to 1/2". The second change came in the nozzles that were used for all motors. Until then they used a bell shape that looked cool and was probably easy to manufacture, but it was inefficient. They went to the straight throat and cone nozzle which was not only more efficient, but were shorter and probably let them squeeze in a bit more propellant.

Had they stayed with the English designations they would've called them B1.2 or something but they went metric and created the B6 (of course the B.8 remained in the line up as the B4, but that got redesigned with larger grain and larger nozzle area as they eventually standardized on the 1/2" grain diameter)

The A8 and 1/2A6 have been redesigned a couple of times over the years.

 

[Silverleaf]

Many thanks for the history lesson, nice to read where the hobby came from, and especially when Estes made changes. 8)

 

[Jacques]

Has Estes modified the delay grain formulation? Seems to me when I was flying rockets in the 1960's and 1970's the smoke pattern was much denser than it is now. If someone has still got a stock of old motors that they use, can they tell me if they notice a diference?

 

[ronhill]

During the last year, I've flown a number of Estes motors with 1974 or earlier dates. I can't tell a difference in the delay smoke trail between the older motors and today's motors. I started launching in 1962, but the memory grows a little hazy in comparing the engines of 40 years ago with today's engines. One way or the other, it was an exciting time.

BTW: For Estes engines, I've not had one failure with these old engines in at least 20 launches.

For old FSI engines, I've had only one CATO (I believe with a D18) out of 15 or so firings. But that's about the same failure rate that we saw 30 years ago. The FSI engines still put on a good show.

 

[shreadvector]

Yes, they have.

For a while in the 1970's the Centuri motors had much more smoke than the Estes motors during the delay. Then when all the Centuri motors were made at the Estes plant they were identical except for label.

A few years ago there was a great quality slip at Estes. Delay times were way short. Ejection charges were weak or missing on some motors (worst were the D12 motors from year A and B). Clay was changed from good clay to "Poopy Clay" (looked like white powder). Smoke disappeared from delays.

Then Quest showed up with their US and then their Geman motors. The German motors had super accurate delays and TONS of smoke in the delay. We spoke at great lenght about this on r.m.r. and within a few months Estes responded with improvements. They added smoke. They fixed the delay time and they switched to "Strong Like Ox" clay (looks multi-colored).

I'm not sure if the smoke is still all there in the most recent Estes motors (we've had clouds at recent launches and it masks smoke), but the clay is still "Strong Like Ox".

Originally posted by Jacques
Has Estes modified the delay grain formulation? Seems to me when I was flying rockets in the 1960's and 1970's the smoke pattern was much denser than it is now. If someone has still got a stock of old motors that they use, can they tell me if they notice a diference?

 

[powderburner]

Does anyone have any idea where thrust curves, etc, might be posted online for the old (out of production) motors from Estes and Centuri?
I think the NAR website only lists data for current production motors--

 

[shreadvector]

Catalog thrust curves would be on the websites with old catalogs archived.

NAR S&T thrust curves would not be online because there was no such thing as "online" several decades ago when those old thrust curves were generated on the chart recorder and pasted into a notebook.

Originally posted by powderburner
Does anyone have any idea where thrust curves, etc, might be posted online for the old (out of production) motors from Estes and Centuri?
I think the NAR website only lists data for current production motors--

 

[powderburner]

How did we LIVE without the internet?

Originally posted by shreadvector
NAR S&T thrust curves would not be online because there was no such thing as "online" several decades ago when those old thrust curves were generated on the chart recorder and pasted into a notebook.

So, I think you answered my qstn? This old data has never been posted on the web? (I'm not counting those dinky, online, poorly-digitized charts in the old Estes catalogs)