Weed Grubber - made using an old strimmer and car alternator armature

**brianhw** · Jun 19, 2020, 02:34 PM

I always thought these alternator armatures would have some sort of use and now I've eventually found one ! I decided to modify half of one to use as a weed grubber head for my old strimmer and it worked exceedingly well, saving time and effort on hands and knees pulling weeds from my potato plot.

**VinnieL** · Jun 19, 2020, 07:22 PM

That's impressive!!

**Gergemall** · Jul 10, 2020, 09:48 PM

Very impressive. The machined square to hold it firmly was also genius. Thank you so much .

**TrickieDickie** · Jun 19, 2020, 07:42 PM

The armature will probably out last the trimmer.

**N00b Machinist** · Jun 28, 2020, 07:45 PM

Devil’s Advocate here: I imagine the string portion of a trimmer is to minimize damage to non-weed bystanders, e.g., stakes, mailbox posts, ankles, etc. What you’ve got there is a blunt pole saw. Useful, to be sure, but additional care, I expect, is necessary to avoid tearing up things you don’t want tore or launching stones or cans or other FOD at those nearby, including yourself. Also kickback - that’s going to kick back much harder than a string on a spinner.

In the right hands, a masterful tool. I can imagine myself f**king things up spectacularly in my own.

**brianhw** · Jul 11, 2020, 01:26 PM

Originally Posted by N00b Machinist

Devil’s Advocate here: I imagine the string portion of a trimmer is to minimize damage to non-weed bystanders, e.g., stakes, mailbox posts, ankles, etc. What you’ve got there is a blunt pole saw. Useful, to be sure, but additional care, I expect, is necessary to avoid tearing up things you don’t want tore or launching stones or cans or other FOD at those nearby, including yourself. Also kickback - that’s going to kick back much harder than a string on a spinner.

In the right hands, a masterful tool. I can imagine myself f**king things up spectacularly in my own.

Care is indeed essential,N00b Machinist. You have to concentrate to avoid nearby plants, just as you would with a (s)trimmer but surprisingly there's no kickback worthy of mention. My vegetable patch is pretty well stone free and any small ones encountered don't cause any problems.
Thanks for comments.

**hemmjo** · Jun 13, 2025, 05:15 PM

Originally Posted by N00b Machinist

Devil’s Advocate here: I imagine the string portion of a trimmer is to minimize damage to non-weed bystanders, e.g., stakes, mailbox posts, ankles, etc. What you’ve got there is a blunt pole saw. Useful, to be sure, but additional care, I expect, is necessary to avoid tearing up things you don’t want tore or launching stones or cans or other FOD at those nearby, including yourself. Also kickback - that’s going to kick back much harder than a string on a spinner.

In the right hands, a masterful tool. I can imagine myself f**king things up spectacularly in my own.

This is not really a correct assessment of the tool or a string trimmer.

First even the string trimmer is very destructive to all kind of things. The outer edge of a typical string trimmer, 16" diameter @ 7,000 RPM, exceeds 300 MPH. That is high cut through wood fence posts, debark trees, and launch rocks and stones in excess of 300 mph. In regard to kick-back, NO ONE is quick enough to react to a 300MPH force when the string unexpectedly grabs a hold of some immovable object.

Second the alternator rotor is much smaller in diameter, 5" diameter @ 7000 RPM, so only about 100 MPH. That is still very fast, BUT the outer circumference of the edge is much more smooth and not nearly as likely to grab something.

As with any tool, you have to use proper caution.

**hemmjo** · Jul 23, 2022, 05:20 AM

Looks like you have pretty good soil there. I have a couple of old alternators here, I am going to have to try that. My soil is not as friable as yours appears to be.