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Ten Penny Motor Shafts — Parallax Forums

Ten Penny Motor Shafts

ercoerco Posts: 19,989
Is it just me, or do those two "shafts" look a lot like finishing nails in this overpriced motor/gear kit?


  • Must be using Common Core math, too. Now 3.8 cm = 1 inch!

    Hey, maybe this is a motor kit for wooden bots!
  • Yeah, nails aren't exactly round, either. ('Had considered them for clock gear shafts; went with dowel pins and drill blanks instead.)

  • GordonMcCombGordonMcComb Posts: 3,366
    edited 2016-03-25 01:31
    Yup, they're nails. Happily, not rusty, because then you'd need a tetanus booster just to play with electricity.

    But let's look more closely, my fuzzy friend: he's sold 62 so far. Someone is buying 'em, and with >$5 shipping, to boot. All this might make you think we're in the wrong business. Let's see: $1.25 for the parts, $1.25 for first class postage, $2.50 out of pocket, $8.50 with shipping, total profit $6.00. Multiply by the 62 sold so far, and you've got $372. He has another listing for a similar kit he sells for a little less, so make it about $700 profit.

    Let's do some more math. If each kit takes 10 minutes to package and mail, and he's sold about 140 kits total, that makes for around 23 hours; with $700 profit, that's $30 an hour -- equivalent to about a $60,000/year job. Not bad for selling nails.
  • Might the nails be for the Motor Mount?

    Mabuchi is a very reputable manufacturer but there might be so much play in the gearing that using a nail as a shaft might work.
  • ercoerco Posts: 19,989
    It might not even be a genuine Mabuchi. There are numerous Chinese clone motors, all cheaper and lower quality than Mabuchi, which use Mabuchi's naming conventions, ie RE140, RC260, etc.
  • ercoerco Posts: 19,989
    edited 2016-03-25 23:42
    erco wrote: »

  • ercoerco Posts: 19,989
    Seller's reply to: "Those 'shafts' look at lot like nails."

    You are correct. It is a 1-1/2" d4 "Extra strong steel resist bending" trim nail from Maze Nails.
    It fits the hole in the gears tight enough so it does not wobble and not so tight as to bind.
    The head is smooth and is a good outside stop.
    I have found nothing else that works.
    A customer shared this with me about 4 years ago and I have been including it in the kit ever since.

  • GordonMcCombGordonMcComb Posts: 3,366
    edited 2016-03-25 23:44
    Even if it's an official Mabuchi, they offer different sub-models with varying wholesale pricepoints and capabilities. Their less expensive models (the specs for the motor suggests this is one such motor) can be fairly inefficient, consuming several amps even at 1.5V. A real Mabuchi sold through retail will have a metalized label on it. Anything else is anyone's guess.

    Elsewhere on eBay you can get the RE-140RA for about 25 cents each, and this (by the 3-6V specs) is for the high efficiency model.
  • ercoerco Posts: 19,989
    edited 2016-03-25 23:52
    Yup, most Mabuchi motors are available with a variety of internal parts. Different windings (wire size & number of turns), brushes (economy metal versus carbon), magnets (standard vs oriented) and even different commutator timings and bushings. In many cases they look identical from the outside and it's impossible to ID the motor by visuals alone. Their catalog is online and fun to poke thru occasionally. Here's the RE140 page:

    BTW the winding number (ie 2270) indicates the wire size and number of turns, helpful info.
  • WhitWhit Posts: 4,181
    Using their kit - no matter how the project turns out - you can honestly say, "Nailed it!"

    To quote Carol Lynn Hazlett, "Somebody had to do it."
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