Agitating for Series 17 tubing
 

Comrades:

Gus' posting of a Nike-Nike-Smoke in another thread reminds me that another year has past without a vendor selling Series 17 tubing with 1.74" outer diameter and 1.70" inside diameter. This tubing would be great for the Smoke section on this rocket but would be absolutely perfect for a project near and dear to my heart: 1/10 Black Brant V.

A 1/10 Black Brant would have a 22.5 inch section of the new Series 17 with a section of Series 16/BT-60 at the bottom for the unusual reduced diameter section at the bottom of this Black Brant. Some fins, a 5.25" Series 17 bezier nose cone and Series 16/BT-60 engine mount hardware and you've got it; a rocket in present day use with ties to Canada and the United States. From here, you could do Black Brants VIII, IX, X and XII with various American boosters, with XII being a Talos-Honest John (M50)-Black Brant V with a Canadian Nihka fourth stage.

There are probably other rockets to use this tube for scale purposes but other than an Australian Jaribu, I can't think of any.

So if Semroc/eRockets or Apogee or Estes (call it BT-64 or something) wants to expand the product line, (or develop a new, non-military, scale kit) well, here you go.

Just curious why the number, ten, has significance enough to demand that some vendor get stuck with a load of oddball tubing?

Couldn't you get by with coupler stock from BMS? The coupler stock is listed there as having a 1.796" diameter.

Actually, 1/10 scale is a very handy uniform scale as Carl at Semroc discovered before his passing. He called it Deci-scale. In addition to the Semroc Nike-Tomahawk and Aerobee kits, its a good size to make everything from Sparrow to Pershing missiles. All the Nike-based sounding rockets, Terrier-based sounding rockets, Taurus (Honest John)-based sounding rockets, Talos- based sounding rockets, Sandhawk, WAC, Astrobee and others can be built in this scale with presently existing tubing. A check of eRockets indicates that Carl had designed most of the nose cones for these sounding rockets in this scale for a scratch builder. Of course, you could also build their missile brethern (before being beaten into plowshares) in this same scale as well. Nike-Hercules and Pershing kits already exist.

Semroc carries the various tubing sizes in increasing .10" increments. The Series 15 tubing was a relatively recent development. Semroc and others carried the other sizes. But there were two missing sizes: Series 14 (1.44" outer diameter) and Series 17 (1.74" outer diameter) The 14 would work for Hawk-based missiles and sounding rockets and as noted the 17 for all the various Black Brant-based rockets. 14 would also be the proper size for Shenzhou LRBs in 1/64 scale.

Frankly, there's nothing that would indicate that a manufacturer would be "stuck" with this size tubing any more than Estes was ever "stuck" with odd-ball sized BT-52 tubing or BT-65 or some of their other off-size tubing they have made over the years. The answer is make something out of it. Series 17 tubing would be a 1/70 scale Atlas or Titan or Falcon 9. With the right nose, they'd be constant scale with your Semroc Saturn 1B. No, it's not getting "stuck" with extra tubing, it's an opportunity for imagination.

Or you could just go a more "normal" route and use BT-60/ST-16 tubing and figure out the scale from there...it would probably be like 1:10.7 or something like that.
FAR simpler and FAR more likely you end up with a model.

I would tend to agree. There really seems to be little in the 1.7x OD range, and a few scale kits as you suggest would open that possibility up.

I recognize that in suggesting an ST-17 you'd be in keeping with the Centuri approach of 1.700" ID/1.740" OD, but that would technically render the Black Brant V model slightly larger than 1/10th size (the motor case had an OD of 17.26"), but hardly an issue for a sport scale model. I seem to recall that Taras Tataryn produced just such an airframe some years ago for his line of ARG 1/10th size Black Brant kits, so it has been done before. Producing the airframe for kits also makes life a lot easier for scratch builders, as you also point out.


The combination of airframe and tail can diameters is somewhat problematic for the BBVC, as they are so close - 17.26" for the motor casing, 16.20" for the tail can. It's hard finding a set of manufactured tubes that fit this ratio exactly. A few years ago I built a Black Brant VIII, and my approach was to use BT-70 for the BBVC airframe, and a piece of ST-20 for the tail can. The scale factor was set to the airframe, which returned a SF value of 1:7.79. That meant the tail can would need a wrap of 0.020" Styrene to build it out to the correct scale diameter. Sometimes there just aren't going to be the "right" tubes for a precise scale build, and so one adjusts, depending on the goal of the project.

I'd certainly welcome a 1.7x OD tube, and if it introduced some mainstream scale kits, so much the better.

This is weird yet wonderful--just this morning, I was brooding over the relative lack of sounding rocket scale kits, and of "mix-and-match" parts that would enable modelers to depict different rounds of various types of sounding rockets! I hope John Boren reads this thread and takes the suggestions of the posters here to heart! (1/10th Scale kits or scratch-built models of the various versions of the British Skylark sounding rocket--whose Raven, Gosling, and Cuckoo motors were the same diameter as the Black Brant I, II, IV [first stage], V, and Nihka rocket motors--could also be made using Series 17 tubing.) Also, regarding Black Brant models of Deci-Scale size:

In its early days (the 1970s), Semroc also made a 1/10th Scale Black Brant III (see: http://www.ninfinger.org/rockets/ca...70semroc14.html ), and Taras Tataryn's 1/10th Scale ARG (Advanced Rocketry Group) Black Brant III kit (which Sunward and then erockets took over, see: http://www.erockets.biz/advanced-ro...el-rocket-kits/ ) is/was the same size. With a first stage made of the Series 17 tubing, the 1/10th Scale Black Brant III would become (with a conical stabilizer/transition in place of its single-stage version's fins) the second stage of a 1/10th Scale Black Brant IV model. (Taras also had--and may still have--a full-scale [inert, of course] Black Brant IV version [called the Black Brant IVA or IVB; I forget which], which had three small delta fins on the second stage's conical stabilizer, for additional stability.)

I second that request.

It would fill a gap in my favorite upscale chart:

BT-5 0.544" -> 0.908" T-.908" (ST-8)
BT-20 0.736" -> 1.229" T-52H (29mm motor mount tube)
ST-8 0.908" -> 1.516" T-40 Quest
BT-50 0.976" -> 1.630" BT-60
ST-10 1.040" -> 1.737" ???
BT-55 1.325" -> 2.213" BT-70
BT-56 1.346" -> 2.248" T-70H
BT-60 1.637" -> 2.734" Semroc ST-27 or LT-275?
ST-20 2.042" -> 3.410" ??? Estes Mercury Atlas size
BT-70 2.217" -> 3.702" BT-100

Plus it is the right size for an Agena in 1/35 scale.


Bill

If some variant of 3D printing technology can be developed for producing spiral-wound and parallel-wound (BT-30 type) paper body tubes (custom-size mandrels would be easy enough to 3D print), Estes, Quest, or smaller model rocket companies could produce and sell custom-diameter (and wall thickness) tubes made to customers' specifications, much as Semroc--before Carl died--made custom-turned nose cones that customers could design using an online template. (Smaller companies, I'd conjecture, would be more interested in making such custom body tubes than would mass-marketers such as Estes and Quest.) Also:

Another possibility for making custom-size body tubes might be a variable-diameter mandrel made of thin-gauge, pre-stressed metal (like the Viking Landers' soil sampler arms [and the booms that JPL designed for the "square rigger" solar sail for their proposed Halley's Comet mission]), which unrolls like a steel tape measure, then rolls up ("width-wise") to form a cylinder. A small (numerically few, that is) series of such variable-diameter pre-stressed metal mandrels might enable the production of body tubes of any size.

If you really want it that badly
 

go to a local machine shop and have a piece of pipe turned down to the ID you need. Don't forget you could use plastic (PVC) pipe for a mold surface. Practice a little with laying up some brown butcher paper (or whatever type of material turns you on).

Dedicated scale modelers do it all the time.

30618 CM-8EA** $.60 4.180" 1.685" 1.785" 0.021" .368 6
30616 PST-65R $.55 5" 1.595" 1.641" 0.023" .368 7

http://www.ninfinger.org/rockets/cu...no_diagram.html

http://www.oldrocketforum.com/print...54&page=2&pp=10

http://www.oldrocketforum.com/print...54&page=4&pp=10

See Tubes:

http://www.oldrocketplans.com/centu...F-10Hustler.pdf

ID 1.75
OD 1.84

U.S. Rockets 54mm casting tube is 1.80 x 1.86. Close.

http://www.rocketmotorparts.com/54m...09_7781922.aspx