I think the BT-40 was an "adopted" tube size, from leftover MMI (Model Missiles, Inc.) body tubes for their Aerobee-Hi and Arcon kits that Estes acquired when MMI went bust. Estes also sold the vinyl MMI Aerobee-Hi/Arcon nose cones at that time.

__________________
Black Shire--Draft horse in human form, model rocketeer, occasional mystic, and writer, see:
http://www.lulu.com/content/paperba...an-form/8075185
http://www.lulu.com/product/cd/what...of-2%29/6122050
http://www.lulu.com/product/cd/what...of-2%29/6126511
All of my book proceeds go to the Northcote Heavy Horse Centre www.northcotehorses.com.
NAR #54895 SR

I have one of those long vinyl nose cones, and the one that I have fits a BT30.

Here is a 1965 Estes Free Plan for an Aerobee-Hi that used BT-40 (see: http://www.spacemodeling.org/JimZ/eirp_32.htm ). It used a vinyl nose cone whose designation was PNC-40G. I wonder if your nose cone might be one of the leftover firework missile parts that Estes Industries sold in the early days (Vern Estes was in the fireworks business before he founded Estes Industries)?

__________________
Black Shire--Draft horse in human form, model rocketeer, occasional mystic, and writer, see:
http://www.lulu.com/content/paperba...an-form/8075185
http://www.lulu.com/product/cd/what...of-2%29/6122050
http://www.lulu.com/product/cd/what...of-2%29/6126511
All of my book proceeds go to the Northcote Heavy Horse Centre www.northcotehorses.com.
NAR #54895 SR

Though I've heard from good sources that over the past few years the Hi-Flyer is the big seller.

__________________
Roy
nar12605

Note that prior to 1968 and the metric conversion, the NAR Total Impulse chart was a bit different.

It didn't nicely double over the whole range.

1/4A 0 - .175 lb-sec
1/2A .176 - .350 lb-sec
A .351 - .700 lb-sec
B .701 - 1.200 lb-sec Whoops!
C 1.201 - 2.00 lb-sec Whoops! again!
D 2.01 - 4.00 lb -sec ah, back to doubling
E 4.01 - 8.00 lb-sec
F 8.01 - 16.00 lb-sec

__________________
Roy
nar12605

Due to its large fin area and Center of Pressure/Center of Gravity relationship, the Hi-Flyer can be (like the Estes Phoenix missile scale kit) one of Estes' more...exciting rockets to fly, especially on the heavier "C" motors that move the CG more rearward--"No two flights the same!" :-)

__________________
Black Shire--Draft horse in human form, model rocketeer, occasional mystic, and writer, see:
http://www.lulu.com/content/paperba...an-form/8075185
http://www.lulu.com/product/cd/what...of-2%29/6122050
http://www.lulu.com/product/cd/what...of-2%29/6126511
All of my book proceeds go to the Northcote Heavy Horse Centre www.northcotehorses.com.
NAR #54895 SR

I will say that I have purchased a large number of Hi-Flyers myself. I've only built one as a Hi-Flyer, and that one was built with a 13mm motor mount. Why did I buy so many of them (and continue to do so)? Two reasons - it is cheaper than any other BT-20 based rocket ($6-7 as opposed to $8-9 for a Wizard or Viking) and the body tube is a bit longer than that in the Wizard or Viking. Thus, the Hi-Flyer is really good for kit bashing into various types of contest models (18mm boost glider pods, egg-on-a-stick boosters, quick and dirty streamer duration models, etc.). Because of the price, that sucker's just a kitbasher's dream!

Greg

Could it have instead been an Estes motor shipping tube? These were usually light blue, and should have been about the right size for the FSI motor.

Doug

.

__________________
YORF member #11

The Quest D5 motors are 20mm in diameter (0.787"), FSI's A4, B3, C4, D4 and E5 motors were 21mm in diameter (0.827"). Their E60, F7 and F100 motors were 27mm in diameter (1.063") and their A6, B6 and C6 motors were 18mm (0.709") in diameter. When I was thinking about the possibility of using BT-40 for motor tube, I was extrapolating from the fact that I use it for the 20mm Quest D5 motors. But I was incorrect because the FSI motors wouldn't have fit. The best fit in existing tubing would have been in Centuri ST-8, which had an ID of 0.865" and an OD of 0.908". This was a commonly-available tube and is probably what you used. I never had any FSI motors so I have no experience with adapting them to fit into a motor mount.

FSI themselves used RT-8 as a motor tube for their 21mm motors. This had an ID of 0.885" and an OD of 0.921". Throughout most of their catalogs, the company incorrectly labeled RT-8 as "0.903" tubing." I have no idea how they derived that number, but it doesn't match any dimension of RT-8.

Did you mean to say that 0.945" was the outside diameter of your old tube? If so, it matches the OD of Semroc Series 085 tubing. It would have been a perfect fit inside 24mm motor mount tubing, such as Estes BT-50.

__________________
SAM # 0011

From what I have read, Estes motor shipping tubes were just a smidgen larger on the inside than the diameter of the 18mm motors. I would think that it would have been too small to accommodate a 21mm FSI motor.

__________________
SAM # 0011