Body tube question.
 

Are BT-70 and ST-20 the same tube? —and is there a cross reference?

Thank you and Happy Easter!!

No they are not.
ST-20 is 2.04" diameter.
BT-70 is 2.217" diameter.
Not even close.

The first usage I'm aware of a Centuri tube used in an Estes kit was the main ET tube of the 1284 Space Shuttle. It is ST -20.

Hi Jeff,

The tubes aren't the same diameter, about .2" diameter difference.
Centuri ST-20 is 2.04" outside diameter
Estes BT-70 is 2.217" outside diameter.

body tubes
 

No, the st-20 is smaller dia, than the bt-70. The st was acenturi size tube, while bt was a estes tube. you can check specs of tubes being sold by erockets, old centuri and estes catalogs under body tube section on ninfinger site.

Everybody else here has given the dimensions so I won't repeat.
While the ST-20 is a Centuri sized tube, Estes uses it in the Mercury Redstone kits and since it's the same scale, the Mercury Atlas uses some, (I think) and the Mercury Little Joe.

There may be other Estes kits that use the ST-20 size but those three are the only ones I can think of.

The Eggspress and newer Scrambler #2072 were in the Enerjet Eggcrate lineage so have a short section of ST-20 as the payload airframe. The eggcone and the coupler are in the Estes website in a TARC parts assortment.

Don’t forget Estes tube guide

Happy Easter to you too, Jeffy!

Yep, what everyone else has said here about the tubes in which you inquire. They speak truth! The only thing I'll add is that the ST-20 may be somewhat thicker walled, too. Centuri tube specs tended to spell out thicker-walled tubes in general, though I have not compared the specs for these two tubes specifically.


Earl

The first Estes original kit to use the ST-20 was the full-stack 1284 Space Shuttle.
The Mercury Redstone that Estes has offered since the demise of their own K-41 was of Centuri design.

Here's are cross references of Estes, Centuri, and Quest body tube sizes and dimensions. I printed these out and use them all the time.
From the Ninfinger website:
http://www.ninfinger.org/rockets/body_tubes.html
http://www.ninfinger.org/rockets/bo...es.html#centuri
http://www.ninfinger.org/rockets/body_tubes.html#quest

From the old Semroc website:
http://www.semroc.com/Store/Products/BodyTubes.asp