In the new Estes 2024 catalog, there are some new Mini models.
The Mini Alpha, Mini Arcas, Mini Bertha and aq reissue of the Mini Max kit from 2010.
These were referred to as Mini-Brutes in the Narcon manufacturers forum video.
In 1973, the original Mini-Brutes were designed for the new 13mm mini engines. To see them: CLICK HERE and page through the catalog.
The upcoming Mini Bertha and Mini Alpha are snap together. The Mini Max and Mini Arcas are traditional kits you build.
This blog build will be a clone of the Mini Bertha from 1973. I had a Mini Bertha then, it was a favorite.
The original Mini Brute kits had Kraft tubes with balsa fins and nose cone. Assembly is much like an 18mm motor kit, just smaller.
The descriptive copy on the Mini Bertha says a 8" chute is included, but a 10" parachute is in the instructions parts list.
The build starts tomorrow!
My parents got me some packs of motors as a birthday present. Amongst the packs there were a few that had me scratching my head -- these were A5-2S motors. As I had entered into the hobby in the mid-1970s -- several years since the short motor series had been phased out. From what I can find on the Ninfinger site, the last catalog that listed these motors was the 1973 catalog (the catalog I got in my starter set was from the following year -- 1974).
ReplyDeleteHI Naoto,
DeleteThe A5-2 and A5-2s (short) engines go back to the 1968 catalog. https://www.ninfinger.org/rockets/nostalgia/68estp48.html. I always wondered about uses for the 18mm 1/4A3-2 and 1/4A3-4.
From what I remember about the A5-2S that I had, aside from the shortness of the casing (same length as the 13mm motor), as well as how thick it was (inner diameter looked close to what was seen in 13mm motor).
DeleteI'm thinking that the S series was basically an evolutionary step -- by shortening the casing on the 18mm for the lower-power end, you might get a bit of performance gain due to reduced weight. And possibly inner diameter was reduced to try to address problems that may have occurred with the lower-power range -- in particular if you're trying to vary the power by reducing the length of the propellant grain, the shape of the propellant grain approaches a low flat cylinder shape (likened to a pill or tablet), which may be more apt to burst under pressure.
Hi Naoto,
DeleteI always thought the same thing - the S engines were shorter just to be a bit lighter. I also noticed the thicker casings. I wouldn't know about reducing the length of the propellant grain, interesting idea.
Hi Chris! This sounds like an interesting build! A mini Arcas build would be cool, too!
ReplyDeleteHi Jhall,
DeleteIf Estes sends me some Mini Arcas kits to build, they will be featured on the blog.
The completist in me will require building the new kit. Hopefully it is simple enough for our Scout Builds
ReplyDeleteHi Phil,
DeleteThe upcoming Mini Bertha should be an easy snap together build with plastic fins and nose cone. You'll probably need to attach the chute and tie on the shock cord.
At first glance the new Mini Alpha and Mini Bertha looked a bit "off" to me -- then noticed "snap together" bit and realized why. The twist-on motor retaining cap extends the body line past the trailing edge of the fins -- changing the appearance somewhat (the original Alpha, Bertha and built-up Mini Bertha have fins positioned with the trailing edge at the rear end of the body tube). Although using a motor clip or friction-fit could've been used to not change the look -- a twist-on retaining cap would be *much* easier to use (especially for beginners).
ReplyDeleteFrom the catalog image, it also looks like the new snap-together Mini Bertha might have three fins rather than four -- which could also make it look "off" to folks familiar with the older models.