It uses the older rating system, this engine is 1/2A.8-4s.
This would be the equivalent of today's 1/2A6-4. The "S" stands for Short.
The manufacturer date code says RWU.
Does anybody know when it was made?
Check out the thickness of the casing!The nozzle bore is curved, not squared off like today's engines.
The loose ejection charge is held in by a creased card stock cap.
There is a small vent hole in the top. Often times these caps worked loose and you'd find some black powder granules in the mailing tubes.
These "S" engines were phased out in favor of the lighter 13mm "T" engines. They were introduced with the new Mini Brute line in the Fall of 1971. The "T" stands for Tiny.
MPC was the first to produce 13mm engines, Estes followed shortly thereafter.
Back then we just called them "half inch" diameter engines. The MPC 13mm engines were longer and available up to a B3-7m! The "M" designation stood for "Mini" or MiniJets.
After Estes got into mini engines, Centuri also produced the longer "B" 13mm engines.
After too many bad engines, the Centuri Mini's were shortened and only available in A power.
Mini engines were lighter and more efficient especially when used in BT-5 models. Many NAR records were broken when the 13mm engines were first produced.
This Series III engine was given to me by Lonnie Buchanon for some good blog fodder.
Thanks Lonnie!
UPDATE: According to this engine dating list: CLICK HERE
Doug Sams did the research and drew up the engine charts.
This 1/2A.8-4s engine was manufactured between 1964 - 1967.
Nozzle shape may be to help upper stage ignition ?...
ReplyDeleteHi Metalhead,
DeleteI don't know if the nozzle shape was to help two stage ignition.
I checked my stash of older engines, none of them as old as this one. The 1970s MPC engines have the curved nozzle bore. The Estes engines in the "diamond packages" have squared off nozzles.
I do remember being quite puzzled when I'd first seen these -- got a few packs of A5-2S as a birthday present from my parents. They weren't listed in any of the Estes catalogs I had (the oldest one I had was 1975 - after the S engines had been phased out). Was rather puzzled at the time as they were the same length and inner diameter as the 13mm, but outer diameter of that of an 18mm (with an extra-thick casing). Ended up cutting a piece of an expended 18mm motor casing to make up the length so that they could fit standard 18mm rockets.
ReplyDeleteHi Naoto,
DeleteI purchased a few of the "S" engines right before Estes was transitioning to the 13mm "T" engines. If I remember correctly we used a BT-20 coupler to fly the shorties in a standard 2 3/4" engine mount..