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  #1  
Old 01-16-2017, 10:23 PM
Vanel Vanel is offline
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Default My fairly expensive, COTS motor test stand

Thought some may find this interesting - details here
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  #2  
Old 01-17-2017, 12:41 AM
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Thanks, Bill. I've often thought of trying to do something like this myself. I have the pieces of a full up Medusa Power Analyzer Pro setup including the "thrust cell", which is a scale that talks to their data analyzer. I may have to see if that can be adapted to do this. A bird in hand and all that.....
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Old 01-17-2017, 01:45 PM
yousah yousah is offline
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That's interesting- thanks for the details.

Our kids are doing SLI and already own the LabQuest interface. Just might buy the load cell to test it out. It's a neat unit, and the LB has a lot of sensors available for all sorts of uses. We're just hoping that it survives SLI
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Old 01-17-2017, 05:34 PM
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Bill,

Very cool!

For those less inclined to build their own I thought I'd share a link with a truly remarkable unit from Adrel Electronika in Poland (photos below). The U.S. Spacemodeling team has used this the last few years to verify the quality of motors we purchase at the Internats. It's a small unit designed just to test model rocket motors. Portable, touch screen operated, runs on a 9 volt battery, data downloadable to excel. Pricey, but phenomenally well designed and easy to use.

A number of different load cells are also available for purchase for the Adrel, from low to high power capable. Like you, Bill, I had to incorporate the load cell into a test stand. The Aerocon website gave very nice instructions how to build one.

Final note. No talk of model rocket motor test stands should be complete without a shout out to the late Art Rose, who for years produced the only commercially available hobby rocket motor test stands, which you can read about here. They were from an earlier, more cumbersome, era of electronics but they worked, and Art made them available to those of us with very limited technical knowledge. Just another of the many ways Art advanced our hobby.
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  #5  
Old 11-30-2017, 09:18 PM
Vanel Vanel is offline
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Measured the thrust of B14 and B8 motors this past Saturday. Puzzled why the B14 peak thrust was only 21 Newtons. Write-up here:

http://billsrockets.blogspot.com/20...it-of-past.html
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  #6  
Old 11-30-2017, 09:50 PM
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Quote:
Originally Posted by Vanel
Measured the thrust of B14 and B8 motors this past Saturday. Puzzled why the B14 peak thrust was only 21 Newtons.

How very interesting.
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Old 12-01-2017, 08:39 AM
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I read somewhere that late production B14's were actually B8's. Photos were shown with early B14, late B14, and B8 nozzles and the late B14 looked like the B8. Am I correct that this was a 1973 B14?

We do know that ISP varies from batch to batch of black powder, so maybe that had some affect on the test subject. Also, Estes/Centuri performance numbers have seldom matched the NAR test numbers. It will be interesting to see the second test, though it would be better to find a B14 that came from another BP batch, maybe one that's a year older or younger than the ones you have.
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Old 12-01-2017, 11:47 AM
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Quote:
Originally Posted by tbzep
I read somewhere that late production B14's were actually B8's. Photos were shown with early B14, late B14, and B8 nozzles and the late B14 looked like the B8.
I was wondering the same thing. In the attached pic, you can see that the 3rd-from-left B14 nozzle was smaller in diameter - it looked about the size of the B8 opening. But the depth measurement indicated it was deeper, 0.75" versus 0.6". However, other/later B14's may have been not been as deep, or maybe the shallower B8 (in the pic) can be attributed to pintle wear.

Either way, the B14 that's 3rd from left does not have nearly the aggressive bore that the two on the left do.

Doug

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  #9  
Old 12-01-2017, 01:17 PM
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+1 to what tbzep just said.
The so-called B14's that were produced from like '76 to '79 were not the deep drilled-core "real" B14's, they were actually pintile-pressed short-core B8's that were still labeled "B14".
~1980 Estes/Centuri started correctly designating them "B8" which is still a FAR better motor than any B6 or B4.
All B8's were produced on Estes machines, none actually produced by Centuri. Interestingly Centuri offered the B8-3 in their line in addition to the B8-5,7,0 that Estes offered under their label.
Why there were no Estes labeled B8-3's is a mystery.
The B8-5 was in Estes lineup for a LONG time.
The B8-0 lasted about 5 years, although it was in the catalog only 80 thru 81...I remember ordering some in '83 for sure.
The other B8's were in the Estes/Centuri lineup for 1980 thru 1981 only...a scant 2 years.
Centuri did not offer the B8 until 1981. In that year, you could get both B8's and B14's under the Centuri label. By 1982 in the Centuri catalog, the only high thrust B was the B8-5.
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  #10  
Old 12-01-2017, 06:02 PM
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I just measured the core depth of a 1975 Estes B14 and a 1990 B8 and found them to be within a hundreth of an inch of each other (0.68" from the casing edge, not the nozzle exit, though they appeared to be the same). The throat diameter of the B14 was 0.17" vs the B8's 0.145", so they were already de-tuning the B14 at that time.
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