I'm currently designing a device and want to increase speed from 120 to 5,000 rpm. Device is lightweight, hand operated, free spinning, low torque in/out. Picture a cheap fertilizer spreader from Home Depot. They increase speed maybe 2 or 3:1, I'd like to up that to 40:1 or so.

I'm currently sketching a chain & sprocket, bevel gear set (need to redirect 90 degrees), and a spur set arrangement to achieve the increase, but wondering if there's a better/simpler way.

I'd like to use all off the shelf parts as I can't afford to custom design anything. I'd like to find an existing speed increaser, but and I've found are super heavy duty and will not work for my application.

This is a home project and I want to keep costs minimal, hence replacing gears with chain & sprocket to reduce cost. Interested to hear what ideas I may not be thinking of for this, thanks.

  • $\begingroup$ Planetary gear with a bevel input or output would be the most compact but probably not the cheapest. A series of chain and sprockets would be cheapest but take up the most space. What are your physical restrictions? $\endgroup$
    – jko
    Oct 8, 2020 at 17:08
  • 1
    $\begingroup$ That kind of speed increase is going to require much better balance and strength on the spinning components. I'd be surprised if it doesn't break up or shake itself apart at high speed. $\endgroup$
    – Transistor
    Oct 8, 2020 at 17:40
  • $\begingroup$ @jko Regarding space restrictions, 1' L 1'W 2'H, so not very restrictive. I'm more concerned about cost and reliability, & keeping it as simple as possible. I like the idea of chain/sprocket or belt/pulley, but it seems getting more than a 1:4 increase may be difficult. $\endgroup$ Oct 12, 2020 at 15:17
  • $\begingroup$ @ScottHartman you'd only need three 4:1 chain/sprockets or pulley/wheels to get that speed, you should be able to fit a configuration of those in that space. Your input torque is going to be very high though. $\endgroup$
    – jko
    Oct 12, 2020 at 17:24
  • $\begingroup$ I'm having trouble equating light duty device and spinning 5000rpm. $\endgroup$ Oct 16, 2020 at 21:39


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