extruding bristle pattern around cylinder

Hi

I am trying to create a cylinder with a simple extruded spike pattern on the outer surface of the cylinder.

Ive been trying to do this with the sheet metal tool, creating the extruded pattern on the unfolded cylinder. However when i fold the cylinder back up it does not keep any of the extruded spike i have made.

Not sure how else i can complete this.

Any suggestions would be greatly appreciated!

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