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Old 04-22-2005, 11:34 PM
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Thrustline 1 Thrustline 1 is offline
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Question K# 28 Thor Agena B Question

i am looking up some parts to reproduce this kit and I'm running into a snag. The BT-52S tube used I can't find anywhere. And, to make matters worse, if you go to the Ninfinger website, it shows the tube as being over 3 inches in diameter...No I know that ain't right.

Any help?
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  #2  
Old 04-23-2005, 01:45 PM
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Quote:
Originally Posted by Thrustline 1
i am looking up some parts to reproduce this kit and I'm running into a snag. The BT-52S tube used I can't find anywhere. And, to make matters worse, if you go to the Ninfinger website, it shows the tube as being over 3 inches in diameter...No I know that ain't right.

Any help?


You've just asked one of the $64,000 questions of model rocketry, you know that?

This is also a SPEV tube, IIRC...

One of the things we've pretty much concluded is, there's no easy answer. Here's an example:

In the Estes 741 parts list, the diameter for BT-52 is listed as 1.114" OD and 0.998" ID. However, BMS sells their Thor-Agena nose cone with 1.010" OD and 0.995" ID. Like the lyric in "Industrial Disease" goes, "Two men say they're Jesus... One of 'em must be wrong..."

I also think we've discovered several instances where even Estes used different thicknesses of BT in different kits, but called all of them "52"...

Here's a suggestion. If you're doing all of the turned balsa work yourself, why not make a slight compromise and just use a Centuri (SEMROC) ST-10 tube? This has an OD of 1.040", which falls between the original Estes spec [highly questioned figure anyway] and the BMS spec. If you compare with the Estes spec, the ID is only 0.002" larger with ST-10. It's going to be similar to Carl's "Retro-Repro" series -- close to the original, but brought up-to-date using more modern design philosophies...

You'll probably get the kit out the door faster this way, too...


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  #3  
Old 09-02-2005, 01:15 AM
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Quote:
Originally Posted by CPMcGraw
This is also a SPEV tube, IIRC...

One of the things we've pretty much concluded is, there's no easy answer. Here's an example:

In the Estes 741 parts list, the diameter for BT-52 is listed as 1.114" OD and 0.998" ID. However, BMS sells their Thor-Agena nose cone with 1.010" OD and 0.995" ID. Like the lyric in "Industrial Disease" goes, "Two men say they're Jesus... One of 'em must be wrong..."


I'm a few months late to the party, but I can say that BMS is correct. I purchased the balsa parts four years ago at NARAM 43, and purchased a BT-52 tube this year at NARAM 47. Everything fits and compares correctly to my SPEV. Essentially the whole upper portion of the SPEV kit (well, except for the BA-6070 adapter) is the Thor Agena kit. (The lower portion is essentially the tube and motor mount for the Estes Little Joe II kit. Both the LJII and Thor Agena had be out of production for two or three years, so the extra parts were made into the SPEV to be offered as a free premium kit. Hence the name, an acronym for Spare Parts Elimination Vehicle).

If I were "BMS Bill", I'd dump the parts in a bag and sell them like he does the Mars Snooper, Gyroc, and Cobra clones.

Roy
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Old 09-29-2005, 09:15 PM
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Quote:
Originally Posted by Royatl
I'm a few months late to the party, but I can say that BMS is correct. ...
Roy
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Roy, is the wall on this tube really just .0075" thick? (1.010" - .995" = .015 /2 = .0075") That is just a little over 1/2 the thickness of a BT-50 and about 1/3 the thickness of an ST-10.

I have wondered about it since I saw it on Bill's site and dismissed it as a typo.
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Old 09-30-2005, 01:06 AM
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Quote:
Originally Posted by Carl@Semroc
Roy, is the wall on this tube really just .0075" thick? (1.010" - .995" = .015 /2 = .0075") That is just a little over 1/2 the thickness of a BT-50 and about 1/3 the thickness of an ST-10.

I have wondered about it since I saw it on Bill's site and dismissed it as a typo.


Well... Hmm....

Just measured my SPEV from three points --- OD= approx 1.024" -- can't get wall thickness.
Measured the tube I got from BMS that was identfied as BT-52 -- OD= 1.044" wall=0.018"
Tube from Semroc Mark II -- OD= 1.045" wall=0.018"

So it looks like the tube that Bill advertised as BT-52 was actually ST-10. I said it fit the parts well, but they did fit easily, and not at all snug.
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  #6  
Old 10-01-2005, 10:15 PM
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Quote:
Originally Posted by CPMcGraw
You've just asked one of the $64,000 questions of model rocketry, you know that?



Craig [Needing to take his own advice] McGraw
---------------------------------
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I've spent some time chasing down the BT-52 dimension question, and I'll post here some findings that I made late last year. This content comes from a message I posted on the Old Rockets newsgroup, message #23393. Kits using BT-52 were addressed in Old Rockets Message #25814:

(Responding to J. Steven's question concerning the kits using BT-52):

- My Colonial viper (#1310) has BT-52S tubes that are clearly 0.013" thick, OD =
1.014", same as yours.

- The piece of BT-52AG in my Semi-Scale Saturn V (#1239) compares favorably to
this (I'm having to compare through the un-opened plastic bag)

- Check out the 1974 Parts Catalog, Page 9 (the nose cone list), and look for
the entry for nose cone No. 36. This is the BNC-52AG, the nose cone for the
Semi-Scale Saturn V. Lists the OD (Dimension #2) as 1.014".

All this means that the OD and wall thickness entries for the BT-52 tubes on the
Tube page are in error. The correct OD is 1.014" and the wall thickness is
0.013", the same as a BT-50 and a BT-51. It means the first jump to a thick wall
tube is the BT-55."


This, plus the measurements I made for Old Rockets message #25814, suggests some strong evidence for the "correct" original dimensions for the BT-52.

John
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  #7  
Old 10-02-2005, 12:23 AM
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Quote:
Originally Posted by John Brohm
All this means that the OD and wall thickness entries for the BT-52 tubes on the
Tube page are in error. The correct OD is 1.014" and the wall thickness is
0.013", the same as a BT-50 and a BT-51. It means the first jump to a thick wall
tube is the BT-55."

John



That sounds right to me, though it sounds like I have 0.005" thick paint on my SPEV, which sounds like a lot (I would've thought maybe 0.0025" at the most)
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