Originally Posted by Royatl

I think they meant the "new" B size as at that time, the B was only 50% more power than A . They did make a C motor by '64, but it was a booster only, because of the small bore of the casings of the time. It put out only about 6 ns. They could only put a delay and ejection charge in them once they built the second generation Mabels that used the 1/2" bore casings.

The A motors of the time were about 10-20% more powerful than our A's. The B's were a bit punchier too. The NAR power categories were adjusted once the metric system was adopted in 1968.

Originally Posted by ghrocketman

I remember the BT-40 was the Estes Engine mailing tube and that the NC-40 cones fit those so you could make rockets from those tubes using commercial parts.

Originally Posted by 5x7

I have a rubber (possibly vinyl) bt-40 nosecone part no. 631-PNC-40H listed in the 1963 Estes Catalog, it may be from model missiles, see nosecone F here: Ninfinger 63Estes Nosecones.

I noticed Gus had one in this post:https://www.oldrocketforum.com/show...058&postcount=5

I think Estes bought out the remaining items from Model Missiles thus the BT-40 nosecones. As far as I know MM never made a rocket for this one so it is a mystery. There is a little slip of paper rolled up inside with directions about how to make a shockcord mount by punching holes in the shoulder and looping a string through. Does anyone have any additional information?

Originally Posted by 5x7

I wonder where I can get one of those spin units...

Originally Posted by 5x7

I wonder where I can get one of those spin units...

Originally Posted by 5x7

Please me know if you are willing to sell it and maybe we can work something out.

Originally Posted by stefanj

I would love to be able to get my hands on those old parts. Build me some Dirty Birds and such.