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Sep 16, 2019, 10:35 AM
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Collet vs. Grub Screw adapters

Pardon my ignorance, but this is my first edf project.

Thoughts on collet type adapters? They don't seem to be very secure to me, but they seem to be the only one available that will match my fa to my motor. Any ways, of which you know, to assure a solid grip, if I use one?
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Sep 16, 2019, 04:20 PM
Big gov never Works
St. Martin's Avatar
The HET fans use a collet adapter. I never had much faith in them. First ones I used were for the 75mm KY fan of the 90's. They offered the collets adapters and alum spinner as an up grade. First run up, the rotor and adapter left the motor. I learned to rough up the motor shaft by running the motor and scoring it with 320. Never lost another rotor. Of course the adapters vary. Some may have some play, these will never run smooth. If any adapter does not fit snug, them balancing could be an issue. Regardless of type of adapter.

Sep 16, 2019, 04:56 PM
Arngeir Blakseth's Avatar
Collet works fine on 10kW 120mm fans for me, so I have no worries. Prefer them to set screws.
Sep 16, 2019, 05:35 PM
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flanker271's Avatar
Never been a fan of collet adapters. The concept is good -- they're supposed to provide true centering and eliminate potential load distribution inbalance during assembly. In reality I don't have much faith in them especially for high power applications.

I lost a Graupner EDF impeller ~11 years ago due to collector adapter loosening. I also had a lot of issue assembling HET 6904 fan units. I'm sure higher quality collet adapters work fine, such as in Schubeler units. I just don't have experience with them.

Getting a good quality adapter that runs true and has very tight hole tolerances is the single most important aspect in having a smooth running fan unit. WeMoTec adapters have never let me down.
Sep 16, 2019, 05:38 PM
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+1 on collets, especially if made of precision-ground steel...120mm rotor on an 8mm motor shaft running 6kW
Last edited by Fanflyer; Sep 16, 2019 at 06:38 PM.
Sep 16, 2019, 09:13 PM
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4stripes's Avatar
I have used both and find collet easier to make run true. Grub screw can have fit issues with the motor shaft but this can be fixed along with other issues like set screws coming loose on the motor shaft. The issue with all types is to get them very secure and as true as possible without any play. Collet type benefit from a slot ground into the end to allow a large flat blade screw driver to hold while tightening the fan nut. Some roughening of the motor shaft with a file and a little locktite (on the motor shaft) will keep the adapter secure. Do not use locktite on the fan nut!
I never trust any collet adapter installed by the "factory". They just are not as secure as my method.

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