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diamond dust with k&b 7.5 prop question

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Old 10-27-2004, 05:17 PM
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edgreenlee
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Default diamond dust with k&b 7.5 prop question

i have a diamond dust with a ducted fan k &b 7.5 and pipe....what prop should i use to get around 22,000 rpms.......? any advice for this set up is appreciated

thanks
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Old 10-27-2004, 08:14 PM
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combatpigg
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Default RE: diamond dust with k&b 7.5 prop question

I don't have any first hand experience with the K&B7.5, but with the DD airframe you can get away with a 7.2-8.6 APC. A 8-8 APC is a safe bet too.
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Old 10-28-2004, 12:46 AM
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Razor-RCU
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Default RE: diamond dust with k&b 7.5 prop question

I remember Esten Spears saying he had his (then mine) K&B 7.5CC FIRE engine turning 19K on a Rev-Up 9x7 but that was on my Scat-Cat...

A 7.2x8.6 would scream, as long as the launch is alright...
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Old 10-28-2004, 10:04 AM
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HighPlains
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Default RE: diamond dust with k&b 7.5 prop question

You might want to limit the rpm (ground reading) to around 21,000. The 6.5 K&B have a metal band around the outside of the crank to decrease case volume. The band had a tendency to break at higher RPM, jamming the crank and causing the rod to snap then go through the side of the engine. I would expect the 7.5 were build about the same.
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Old 10-29-2004, 02:43 PM
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JeffH
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Default RE: diamond dust with k&b 7.5 prop question

i run an 8x8 on my 7.5 cc to get 21500 on the ground with 10% nitro. The crank on the RIRE, does not have a band around it. I have turned it as hard as 24500 with no adverse effects.
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