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I have come across a problem that for the life of me I can't seem to figure out. I'm sharing this here in the hopes that the amazing community here can help push me in the right direction.

The problem goes like this, in my project I require 4 High torque BLDC Motors each having an output torque of 105 N-m or approximately 1070 kg-cm. Due to size constraints we need to go with geared motors. The problem starts here, I have come across a 12 rpm planetary gear DC motor with encoder that has the stall torque of around 584 kg-cm with a gear ratio of 721:1. On further research I can't seem to be able to find a motor with a higher torque than this. I would love to get a guidance from experts regarding what should I do next?

Should I increase the gear ratio or order a custom DC motor more suited to my application.

N.B: Keep in mind this will be used in a vehicle with a load capacity of around 400-500kg. I have verified all calculations and need to source the DC motors now for this load capacity.

I look forward on hearing your views regarding this problem

DC Motor Link: 12V, 12RPM 8110.2oz-in HD Planetary Gearmotor

Edit Update: The project is a automated warehouse management system in which we are developing an AGV (Automated Guided Vehicle). 400-500 kg will be the weight on it after stacking bins on top. Just like shown in the link: daifuku-logisticssolutions.com/image.jsp?id=3767

We can't go lower than 10 rpm (velocity of 0.11 m/s) since we have to cover 100 m in 15 minutes max. I'm attaching a link for related to the custom build DC motor directindustry.com/prod/electric-motor-power-pty-ltd/…

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  • $\begingroup$ Could you put up a link with the BLDC motors that you have with 105Nm? $\endgroup$ – NMech Dec 26 '20 at 5:03
  • $\begingroup$ Well you can get this kind of gear ratios with a two stage strainwave reducers but seriously hget a bigger motor. Anyway what is your reduced inertia? $\endgroup$ – joojaa Dec 28 '20 at 20:30
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From the solutions you are suggesting:

  • increasing the gear ratio: the gear ratio is already too high. And even if you add another gearbox, in series, you would still get a respective drop in rpm

  • ordering a custom DC motor: to me that is the viable solution, although expensive.

Edit: after comment that might improve this answer.

  • As you noted you can't go below 10 rpm. Increasing the gear ratio to reach 1070kg cm would mean that you'd have to go below 6 rpm.

  • Additionally, although the motor you've found has quite a large torque (for its size) it uses a very high gear ratio (721:1), which means that its probably running around 10000rpm. Its max power output should be around 200W.

In comparison the motors at the link you provided, have a max output of 10000W. (50 times more).

The [motor with the Gearbox] you've found is usually used in robotic arms, because it offers high torque at low velocities, in a compact (some would describe it as a toy) form.

IMHO the motors with the gearboxes are toys compared, to the original motors (10kW).

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  • $\begingroup$ The project is a automated warehouse management system in which we are developing an AGV (Automated Guided Vehicle). 400-500 kg will be the weight on it after stacking bins on top. Just like shown in the link: daifuku-logisticssolutions.com/image.jsp?id=3767 We can't go lower than 10 rpm (velocity of 0.11 m/s) since we have to cover 100 m in 15 minutes max Also regarding your comment asking for a 105 Nm motor, i found a link related to it directindustry.com/prod/electric-motor-power-pty-ltd/… $\endgroup$ – Khuzaim Khan Dec 26 '20 at 7:02
  • $\begingroup$ Hi again. you can edit and update the question so that others may provide answers (and don't have to look to this comment). $\endgroup$ – NMech Dec 26 '20 at 7:30
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Contact motor vendors. They will be happy to recommend options. Their goal is to help you ultimately buy their offering for your product.

I've seen where they recommend one option, and if it doesn't perform well enough, provide others at no (or reasonable) cost to help you get the right combination. This at least is my experience in big industry.

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