I see a few question that stray from "Maintenance & Repair" on this site, but I am unsure how far that goes. What about DIY construction/Design?

Sorry about the multiple postings, I did not realise that the first question would not answer everything I needed to know before I posted it. Also, still unsure if this method of asking very generalised meta questions is better or worse than just asking is "Specific Question X Offtopic" or not.

Specifically, I want to figure out how I can have two parallel 1/2 in. shafts (1'-6" apart, more or less), where one powers the second but reverses rotation. Looking around, while sprockets are common and cheap, gears are not.

4 Answers 4


I have 3 things to say about this:

  • sometimes, you don't want to repair a broken vehicle, you want to repair a broken design. When repairing a broken design, sometimes, it's just easier to build your own completely from scratch.
  • sometimes, especially on older vehicles where parts are getting scarce, it's easier (because of availability) to "upgrade" a component rather than replace. So, where would we draw the line? We'll help you replace your hubs, calipers and rotors, but we won't help you convert your rear-end from drum brakes to discs? (That's not a theoretical situation: I needed to bleed my brakes and the bleeder screws for the rear drums were seized so hard they snapped. I just said F%&* it, I ain't drilling this out, I hate drum brakes to begin with, I just went to the junkyard and got me some rear hubs from a higher trim level that had rear discs and went to town by fitting larger calipers and rotors that were an option in Japan and Europe, just not in NA: my Sentra has Maxima calipers at the rear.)
  • whether on-topic or off-topic, most questions of this type fall within the range of knowledge and expertise that the collective membership of this SE has. If we don't answer these types of questions, just where's the OP supposed to go? Automotive Engineering School and take a 4-year degree just so they can do a weekend project without our help?
  • 3
    I like your idea of "... you want to repair a broken design ...". Commented Dec 17, 2016 at 16:40

I don't believe there would be any issue with this. If it has to do with engines and mechanical, whether to fix, design, or otherwise, I think you're golden.


I think that's what the engine-theory tag is for. We may want to consider other "theory" or "principle" tags. The best mechanics that I've known are the ones who have a deep understanding of the machines, the tools, and the people who use both work.


Some of the most popular (most viewed and upvoted) questions are to do with design. See SE data explorer.

There are loads more, and these are slightly design related questions. If we stopped these, we could potentially reduce some gems of questions, and they are within the scope of specific issues with motor vehicle maintenance or repair as on the Tour page.

Oh and I've spammed the tag with 17 questions, I don't want to have lots of off-topic questions! ;)

I think I even wrote the tag wiki for it, so no ulterior motives here, I promise!

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