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  #51  
Old 01-17-2020, 02:08 PM
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The C5 used to have a 2.1 sec burn time with a large kick off the pad then a reduced thrust long burn.
Had as muck kick as the B8, with just double the propellant.

Now we can fly our old C5's again without filing under the "old motor test program"
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  #52  
Old 01-17-2020, 06:27 PM
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Quote:
Originally Posted by 5x7
Without a test stand it's conjecture.

It's not conjecture. NAR and FAI contest fliers have tested motors on test stands over the years, and that's where our anecdotal information comes from. But no one has published the data AFAIK.
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Last edited by astronwolf : 01-17-2020 at 06:30 PM. Reason: spelling
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  #53  
Old 01-17-2020, 07:38 PM
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Quote:
Originally Posted by ghrocketman
I also find not publishing the diameter of each rocket more than a bit perplexing.


The new kits are all posted on the Estes website now. The diameters are listed under Technical Specifications.

BTW, the Doorknob is 3" diameter.
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  #54  
Old 01-17-2020, 08:19 PM
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Quote:
Originally Posted by astronwolf
It's not conjecture. NAR and FAI contest fliers have tested motors on test stands over the years, and that's where our anecdotal information comes from. But no one has published the data AFAIK.


Iíll start a new thread but S&T maintains they basically donít publish because the data is within tolerances of the original published test. I asked for the data and like before even when prodded they donít answer the question.
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  #55  
Old 01-17-2020, 08:22 PM
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Quote:
Originally Posted by Initiator001
BTW, the Doorknob is 3" diameter.

People are going to want to buy two of these to build the two stage version!
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  #56  
Old 01-18-2020, 06:38 PM
Vanel Vanel is offline
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Quote:
Originally Posted by astronwolf
It's not conjecture. NAR and FAI contest fliers have tested motors on test stands over the years, and that's where our anecdotal information comes from. But no one has published the data AFAIK.


This is interesting - I have a test stand I put together using equipment from Vernier, and have used it to successfully test a few motors. So I went to my motor stash and pulled out the following B6-4's:

Date code Weight (grams)
8 12 69 16.59 (also has a greater nozzle diameter)
17F5 (5/17/75) 18.23
19K5 (5/19/80) 17.81
15W5 (5/15/92) 18.36
A052703 (5/27/03) 17.76
B180918 (9/18/18) 19.00

I have dug out the test equipment and hope to do the tests this coming weekend, weather permitting. I then will post the thrust curves for scrutiny.

The attached shows a nozzle comparison, with the 1969 B6-4 on the left.
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  #57  
Old 02-01-2020, 07:29 PM
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Finally found the time with good enough weather to make the measurements - the attached graph shows the results.

Basically, the B6-4 peak thrust has decreased over time and the burn time has increased. Impulse has stayed roughly the same at 4.3 +/- 0.3 N-sec.
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  #58  
Old 02-01-2020, 09:12 PM
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Quote:
Originally Posted by Vanel
Finally found the time with good enough weather to make the measurements - the attached graph shows the results.

Basically, the B6-4 peak thrust has decreased over time and the burn time has increased. Impulse has stayed roughly the same at 4.3 +/- 0.3 N-sec.


Thatís great, and very interesting. However there is no gaurantee a motor from 40 years ago performs today like it would 40 years ago.

Last edited by 5x7 : 02-02-2020 at 10:34 AM.
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  #59  
Old 02-10-2020, 03:22 PM
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My 2020 catalog came in the mail today--direct from Estes. Yay!
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  #60  
Old 02-10-2020, 03:44 PM
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Hmmm, I've got to get that Mars Longship! It reminds me of the spaceship on the Josie and the Pussycats in Outer Space cartoon.
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