BT sizes

[sj_h1]

Does any know where the 20 in BT-20 comes from for that matter 50, 55, 60...
:confused2:

 

[Pantherjon]

Not really sure...Something in my noggin is tickling that I read somewhere(YORF?) that the numbers were pretty well just arbitrarily assigned to the tubes to organize the sizes..I am sure someone more knowledgeable on this will chime in and let us both know!

 

[MarkII]

Once upon a time, in a galaxy far, far, away...

...there was BT-1, BT-2 and BT-3.

BT-1 started out life with an ID of 0.75" and 0.84" OD in 1960, then it changed to 0.765" ID x 0.845" OD in 1961.

BT-2 had an ID of 0.72" (1960).

BT-3 had an ID of 0.725" and an OD of 0.765" (1961).

In 1963, all of Estes Industries' parts were recoded according to a new numbering scheme:

BT-2 eventually became BT-20.

BT-3 eventually became BT-30.

Because BT-1 was bigger than BT-30, it was given a new name: BT-40.

And the rest is history...

MarkII

 

[jadebox]

...there was BT-1, BT-2 and BT-3.

[...]

In 1963, all of Estes Industries' parts were recoded according to a new numbering scheme:

BT-2 eventually became BT-20.

BT-3 eventually became BT-30.

That reminds me of the first programs I wrote in Level I Basic .....

One of the Apogee newsletters has an article about the "History of Body Tubes" which may be of interest.

-- Roger

 

[sj_h1]

Actually that was very interesting information. I suspected they numbers were arbitrary but didn't know for sure. Seeing how all us rocket science people tend to be very logical in approaches, I thought there might be more to it that I didn't know.

 

[RoyAtl]

Once upon a time, in a galaxy far, far, away...

...there was BT-1, BT-2 and BT-3.

BT-1 started out life with an ID of 0.75" and 0.84" OD in 1960, then it changed to 0.765" ID x 0.845" OD in 1961.

BT-2 had an ID of 0.72" (1960).

BT-3 had an ID of 0.725" and an OD of 0.765" (1961).

In 1963, all of Estes Industries' parts were recoded according to a new numbering scheme:

BT-2 eventually became BT-20.

BT-3 eventually became BT-30.

Because BT-1 was bigger than BT-30, it was given a new name: BT-40.

And the rest is history...

MarkII

(McMahon)You are correct, sir. (/McMahon)
But also, by that time they had the mylar tube for the Streak, which was same ID as bt-2/bt-20 but smaller OD. And so they called it BT-10.
The BT-40 was discontinued eventually (since it was just remaining stock from Model Missiles Inc.)

Next to be introduced were BT-50 and BT-60.

Then BT-5 (because was smaller than BT-10) and BT-55 (because it was inbetween 50 and 60).

Then BT-70 (for the GT3/and the Sprite and the Starlight rings, and later for the Little Joe II and Saturn 1B service module).

Then BT-52 (for upper section of the Thor-Agena, since it was between 50 and 55)

Then BT-65 (for the payload section of the original Scrambler, as it was between 60 and 70)

Then a few new tubes for the Saturn 1B:
BT-3 (for the escape tower motor)
BT-51 (for the tank tubes, as it was between 50 and 52),
BT-100 (for the SIV-B) and the slightly larger BT-101 (for the engine skirt)
BT-63 (for the core where the tank tubes were mounted... it was later used in the Saturn V for the removable motor mount.)

Then the new tubes for the Saturn V in 1969:
BT-80 (for the SIV-B)
BT-58 (for the Service Module, as it was between 55 and 60)

They used that slate of tubes in a bunch of different rockets.

I think that pretty much did it, as new tubes after that just got a computer SKU number.

Then they started incorporating the Centuri tubes in some rockets like the Space Shuttle, the Astrocam, and the Challenger-II. I think the Space Shuttle tank tube (Centuri ST-20) was called BT-77. Don't remember what the ST-8 SRB tubes were called (BT-48 maybe?) The Centuri ST-13 parts were relabeled BT-56 (since it was slightly larger than BT-55).

Then new parts started appearing with the E2X line that eventually used a numbering based more-or-less on the part diameter. Hence you have the BT-1090 tubes used in the E2X kits the BT-1835 in the Terrier, and the BT-200 tube in the SpaceShipOne.

And then of course there were the North Coast tubes that were labeled BT-3.00, BT-4.00 and so forth.

 

[MarkII]

Actually that was very interesting information. I suspected they numbers were arbitrary but didn't know for sure. Seeing how all us rocket science people tend to be very logical in approaches, I thought there might be more to it that I didn't know.

Oh, you want to talk about logical?

Estes Industries BT-99 was 94mm in diameter.
Their BT-100 was 95mm in diameter.
Their BT-101 was 100mm in diameter.

How's that for a logical progression?

As Roy mentioned, they made BT-51, which had an OD of 1.011"
And they had BT-52, which had an OD of 1.014"
There was a difference of three one-thousands of an inch (0.003") in diameter. The difference between them in wall thickness was half that, or 1.5 mil (0.0015"). The average diameter of human hair is over 5x as thick as that. Which is more than enough reason to create a whole new series of paper tubing, don't you think?

Also, Estes BT-56 was not simply rebranded ST-13 from Centuri.
BT-56 = 1.346" diameter.
ST-13 = 1.340" diameter.
Totally different tubes, see? That 6 mil difference in diameter makes all the difference!

Just like these two are not the same:
Estes BT-60 = 1.637" OD
Centuri ST-16 = 1.64" OD

Also, Estes BT-48 (OD = 0.928") was not the same as Centuri ST-8 (OD = 0.908").

Another interesting system is the way that Flight Systems, Inc. named its body tubes:
RT-6 (OD = 0.759")
RT-8 (OD = 0.921")
RT-10 (OD = 1.17")
RT-12 (OD = 1.34")
RT-15 (OD = 1.64")
RT-17 (OD = 1.84")
RT-19 (OD = 2.04")
RT-225 (OD = 2.34")

Do you see how that progression worked?

MarkII

 

[bob jablonski]

And what dose Starlight do?
What "E" calls BT20 OD 0.736 we call BT7
BT50 OD 0.95 we call BT10
BT55 OD 1.325 we call BT13
BT60 OD 1.637 we call BT16
ect. They are the same tube.
Red Arrow, Loc, PML and a few others have a similar system.
Mr. Bob
starlight historian
www.starlightrocketry.com

 

[Micromeister]

BT-50 has on OD of .976", .95" is the ID

 

[nukemmcssret]

I always thought it was millimeters like BT-80 is 80 mm outside diameter.

 

[MarkII]

I always thought it was millimeters like BT-80 is 80 mm outside diameter.

BT-80 has an OD of 66mm.

BT-3 = 9.5 mm OD
BT-5 = 13.8 mm OD
BT-20 = 18.7 mm OD
BT-30 = 19.48 mm OD
BT-50 = 24.79 mm OD
BT-55 = 33.655 mm OD
BT-60 = 41.58 mm OD
BT-70 = 56.3 mm OD

Centuri ST-8 = 23 mm OD
ST-10 = 26.4 mm OD
ST-13 = 34 mm OD
ST-16 = 41.656 mm OD
ST-20 = 51.8 mm OD

Quest tubing does indicate the OD in the name:
T-15 = 15 mm OD (0.59")
T-20 = 20 mm OD (0.787")
T-25 = 25 mm OD (0.984")
T-30 = 30 mm OD (1.18")
T-35 = 35 mm OD (1.378")
T-40 = 40 mm OD (1.575")

So does Apogee, but with them, the name indicates either the inner or the outer diameter, or else it splits the difference (whichever yields the closest whole number, I guess ):
AT 13/18 = 13 mm ID (and 18" long. Talk about mixed units!!) (BT-5 equivalent)
AT 18/18 = 18 mm ID (BT-20 equiv.)
AT 24/18 = 24 mm ID (BT-50 equiv.)
AT 29/13 = 29 mm ID (motor tube)
AT 33/18 = 33 mm (BT-55 equiv) (Midway between the ID and OD )
AT 41/18 = 41 mm (BT-60 equiv.) (Again, midway between the ID and OD)
AT 56/18 = 56 mm OD (BT-70 equiv.)
AT 66/18 = 66 mm OD (BT-80 equiv.)

High power tubing from Aerotech, ARR, GLR, LOC/Precision, PML, RDS and others, is always named according to its ID (in inches).

MarkII