Thread: $15 Grinder Project

Grinding with a coarse whetstone has got to be the world's most tedious activity, and I wasn't very far at all into my utility knife making project when I got tired of it and decided to build the fabulous feat of redneck engineering you see here. My original intention was to cut up the frame and arrange it so I can pedal with my feet, but it seems to work OK so far turning it by hand. Total cost; $15 for the bicycle at the thrift store.

The disc is a standard angle grinder disc, whose hole is the perfect size to accept a skateboard bearing. The spacer is a skateboard wheel bearing spacer, and the bolt is a 5/16" UNC bolt (standard skateboard axle size).

I cannibalized the sprocket off the rear hub of the bike. I used hot glue to secure both the wheel bearing and the sprocket, but the sprocket attachment didn't last, so I'm going to have to come up with something better.

Edit; for the record, I mean no disrespect to the rednecks, on the contrary, I admire their resourcefulness & their ability to do a lot with a little, as ought to be evident by my imitation.

You might be a redneck if...

Awesome contraption!

Awesome. I love it.

YeeHa~
respectfully
~Richard

This is a novel idea
And instead of the grinding disc, you could use a contact wheel or a drum, and make adecent belt sander. Bicycle frames + bearings are a dime a dozen (or rather, for free at the recycling center)

And perhaps an electro motor for the drive ...

I put the sprocket back on with plumber's epoxy & have been using the grinder. It's maddeningly slow due to the low RPMs. The right way to do this would be with a variable speed motor. A bicycle derailleur seems like an appealing way to get adjustable speed, but I'd be leery of working around a device where chains & sprockets are being driven by an electric motor. There have been quite a few finger amputations caused by fixed-gear bicycles.

Edit: in the end, I am forced to declare this a failure. The grinder definitely works, but when you put things together in this cheesy way (e.g. epoxy instead of screws) it works for a little while, then it breaks. My ability to build things is definitely being hampered by my inability to machine real parts.

The idea of a hand-crank grinder, however, is far from absurd. Even with the setup you see here, it's easy to overheat the metal. I'm tempted to try to build a hand-crank grinder where the wheel rotates in water, with no gearing at all. I'd have to find a local machine shop that can make the parts that I'm unable to make.

I dont know how old you are but if you have children flip the bike over. Make a brace, and have your kids power it for you. Child labor is the last of the untouched resources