heada
Well-Known Member
It goes on for 1.6x10^6 mm
The only sort of logic I recall was that BT-60 was so named because it could fit three BT-20s inside (in a cluster arrangement). That may be apocryphal, but it sounds about right.
The US never adopted the Imperial System. US Weights And Measures Commonly Used is based on the system used by the British in the 1770s. Imperial came along in 1824.Oh, logical stuff like 12 mm (really 12.7 so 1/2"), 19 mm (really 19.05 so 1/4"), 25 mm (really 25.4 so 1")...
Sort of Imperial disguised as Metric.
The timber industry is, in reality, about as metric as a pre-war English motorcycle.
I thought that a number of Estes very early designs had BT-50 main body tubes. If it wasn't minimum diameter (BT-20) then it was usually BT-50, I thought.They always seemed reasonably logical to me. When I started in rockets around 1964 I remembered BT-10, BT-20, BT-30 and BT-60. I wasn't aware of when BT-50 came out, I thought it was later.
The only sort of logic I recall was that BT-60 was so named because it could fit three BT-20s inside (in a cluster arrangement). That may be apocryphal, but it sounds about right.
As I was drawing up the first stage of my multi stage Saturn V on CAD, using a cluster of (5) D12 motors with BT-50 as the motor tubes, @neil_w 's post once again resonated in my mind.
BT-50: 0.976 O.D. x 3 = 2.928. Guess what the I.D. of a T-300 tube is? 2.930
So the likelihood of tube sizes being based on motor cluster capability seems more than just a coincidence.
Very instrucive, @neil_w. This is good to know.The only sort of logic I recall was that BT-60 was so named because it could fit three BT-20s inside (in a cluster arrangement). That may be apocryphal, but it sounds about right.
Hi @lakeroadster,
What a beautiful drawing you have in Post #95! What program did you use to make that?
Stanley
No, quite the opposite:I think the thread has rendered that apocryphal, but I hadn't realized the technical aspect of it was true. Just tried it, it does fit really nicely.
Bill Simon: The body tube designations were my fault. I really didn’t know anything about good practice in part numbering, so I just tried to use numbers that would let us add in-between sizes later on. BT-60, of course, accommodated 3 BT-20 tubes inside, and that was the entire basis for the system.
Thank you, @lakeroadster.Autodesk Inventor
Oof. That's what I get for spreading late-night reading across multiple nights.No, quite the opposite:
I remember calling kilometers "clicks" - porbably spelled "kliks", who knows - while training in the military back in the 70's... But I decided not to fix your fix!Fixed it for ya.
Nice history lesson.
So, I was, um - what's that word? - wrong! - That's the word, I was wrong.
If you're talking about kits- there weren't any BT-50 kits in the 1963 catalog, well there weren't very many kits of any size in that catalog. It appears that the only BT-50 kit in the 1964 catalog was the Farside. (I don't believe I've ever seen a Farside actually.) The next catalog I have is 1966 and it has a lot of kits including a lot of BT-50 kits.I thought that a number of Estes very early designs had BT-50 main body tubes. If it wasn't minimum diameter (BT-20) then it was usually BT-50, I thought.
If you’re talking about BT-55 nosecones, Estes once had a package of blow-molded blunt tip long ogive cones that fit a BT-56 and were just a hair too big for the BT55. But of course they don’t sell a BT-56 tube. I believe theses are holdovers from the old Centuri days. I have an old Estes Maniac that uses these tubes, nosecones and a molded fin can (great flier on a D engine, BTW). And Istill have a handful of those cones that I got in a 5/6-pack from Estes. If you think this may be what you have, search for “BT-56“ in the forums. eRockets still sells a Semroc ST-13 body tube, which is the same size as the mythical BT-56.I dug through some old nose cones I had looking for some to fit BT-50 and found a few that were just a tiny bit too big for BT-50
That is probably what I have.If you’re talking about BT-55 nosecones, Estes once had a package of blow-molded blunt tip long ogive cones that fit a BT-56 and were just a hair too big for the BT55. But of course they don’t sell a BT-56 tube. I believe theses are holdovers from the old Centuri days. I have an old Estes Maniac that uses these tubes, nosecones and a molded fin can (great flier on a D engine, BTW). And Istill have a handful of those cones that I got in a 5/6-pack from Estes. If you think this may be what you have, search for “BT-56“ in the forums. eRockets still sells a Semroc ST-13 body tube, which is the same size as the mythical BT-56.
If you’re talking about BT-55 nosecones, Estes once had a package of blow-molded blunt tip long ogive cones that fit a BT-56 and were just a hair too big for the BT55. But of course they don’t sell a BT-56 tube. I believe theses are holdovers from the old Centuri days. I have an old Estes Maniac that uses these tubes, nosecones and a molded fin can (great flier on a D engine, BTW). And Istill have a handful of those cones that I got in a 5/6-pack from Estes. If you think this may be what you have, search for “BT-56“ in the forums. eRockets still sells a Semroc ST-13 body tube, which is the same size as the mythical BT-56.
BT-30 was slightly bigger than the BT-20 but was parallel wound not spiral and was thicker walled...The US never adopted the Imperial System. US Weights And Measures Commonly Used is based on the system used by the British in the 1770s. Imperial came along in 1824.
I was living in Australia when we converted to Metric. When I moved to the US I had to learn to convert back to the not-quite-the-same measurements in use here. Mostly similar except for volume measurements. Yet another source of rounding and conversion errors.
Now back to our regular program, already in progress...
Wasn't the BT-30 the tube Estes used to ship engines, before they switched to the diamond packs?
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