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Old 11-04-2017, 11:58 AM
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Default Centuri Mini-Motor Revision

Several years ago I was able to buy an old hobby store's supply of Centuri 1/2A 4-5M mini motors. A couple months ago we used them to fly a really fun, NAR approved, old-motor-event with my local club (JMRC). I was cleaning up today and ran across two partial boxes of the motors and as I went to consolidate them I realized they were both the long and short Centuri mini-motors. Enclosed in the box of the newer "shorties" was a notice about the "Important Revision" to the motors. I thought it might be of interest to some of you so I am posting it here, along with some photos of the motors.

Enjoy,

Steve
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Old 11-04-2017, 01:54 PM
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They used to have blue tube.
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Old 11-04-2017, 07:23 PM
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Quote:
Originally Posted by Gus
Several years ago I was able to buy an old hobby store's supply of Centuri 1/2A 4-5M mini motors. A couple months ago we used them to fly a really fun, NAR approved, old-motor-event with my local club (JMRC). I was cleaning up today and ran across two partial boxes of the motors and as I went to consolidate them I realized they were both the long and short Centuri mini-motors. Enclosed in the box of the newer "shorties" was a notice about the "Important Revision" to the motors. I thought it might be of interest to some of you so I am posting it here, along with some photos of the motors.

Enjoy,

Steve



I think the "Important Revision" excuse of casing supplier replacement was marketing BS to mask the fact that they had closed down the motor manufacturing in Phoenix and once again were getting motors from Penrose.
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Old 11-05-2017, 07:14 AM
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There was a period when Estes sued Ball Paper to continue making convolute virgin tube for them as a sole supplier.

Jerry
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Old 11-05-2017, 10:42 AM
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Quote:
Originally Posted by Jerry Irvine
There was a period when Estes sued Ball Paper to continue making convolute virgin tube for them as a sole supplier.

Jerry


I don't doubt they had a beef with their supplier (A few apparently experimental examples of Estes mini motors made with glassine covered spiral wound tubes got into stock and out on the market and I have a couple of them). I just wonder if that's the real reason Centuri went to the shorter motor.
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Old 11-05-2017, 03:38 PM
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Quote:
Originally Posted by Royatl
I just wonder if that's the real reason Centuri went to the shorter motor.

I see only three reasons for the change:
1. Estes began making their motors again and didn't want to fool with tooling for one of the Mabels.
2. Shortened them to the "industry standard", i.e. Estes' length to be compatible with other models.
3. Decided to discontue "B" motors and shorter casings would be cheaper.

I'm with you on thinking it coincided with them outsourcing again.



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Old 11-05-2017, 04:30 PM
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Quote:
Originally Posted by Royatl
I don't doubt they had a beef with their supplier (A few apparently experimental examples of Estes mini motors made with glassine covered spiral wound tubes got into stock and out on the market and I have a couple of them). I just wonder if that's the real reason Centuri went to the shorter motor.

Pictures or they don't exist!
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Old 11-05-2017, 04:39 PM
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Originally Posted by Ltvscout
Pictures or they don't exist!


I've probably posted them here or at TRF at one point or another, but I'll dig around.
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Old 11-05-2017, 04:57 PM
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Found it faster than I thought. New photos.

the date stamp says "6M171" These may have been unrelated to the casing supplier problem, but may have been when they were developing the motors in early 1971. I asked Ed Brown to confirm that they were made, but I failed to ask *when* they were made.

Of course, I don't remember how these came to me. There's a part of my memory that's trying to tell me that these were from the free packs given out at NARAM 13, but I doubt they would give out booster motors when I don't think they had a two stager in their initial kit lineup (they would convert the shorty Beta and Midget kits a few months afterward, as I recall).

The third picture shows the inner spiral gap. I only have two of these, so I must've flown the other two from the pack at some point.
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Old 11-05-2017, 05:26 PM
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Quote:
Originally Posted by tbzep
I see only three reasons for the change:
1. Estes began making their motors again and didn't want to fool with tooling for one of the Mabels.
2. Shortened them to the "industry standard", i.e. Estes' length to be compatible with other models.
3. Decided to discontue "B" motors and shorter casings would be cheaper.

4. B motor version MIGHT have had a much higher cato rate?

Not saying they did, but that is another possible reason.

IIRC the MPC B size 13mm Mini-Jets had a significantly higher cato rate than the smaller ones. Though it may have been one nororious bad batch and they didn't make that many batches of B's (or the others) before MPC bailed.
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