Need help with sprocket ratios?

**Captainleeward** · Mar 6, 2015, 04:57 PM

Need help with sprocket ratios?

I have a 12 volt dc motor that has a gear head on it and turns at 41 rpms . on the motor shaft i have put a 11 tooth gear and on the other shaft is a 60 tooth sprocket which gives me 5.5 rpm. I need 1 or 2 rpm at most what should I do?? can I put a 30 tooth sprocket on the motor will this give me the desired rpm or is the torque wrong.Should I get a gear head reducer and put it in line with the gears I have now. what is the best??
Thanks for looking. L@@KING.

**GlennR** · Mar 7, 2015, 10:31 PM

I've been using this for pulleys. Maybe it will help.

Pulley Calculator. RPM, Belt Length, Speed, Animated Diagrams

**Captainleeward** · Mar 7, 2015, 10:58 PM

I can't find a tooth reference to rpms :O( Nice of you to mention it thanks...:O)

**GlennR** · Mar 8, 2015, 08:30 AM

I reread your question. Since it's a DC motor, why not just add a speed control and adjust the speed by turning the knob down?

Variable speed is the beauty of DC motors, right?

Btw, here's a site for helping choose sprockets for motorcycles. I doubt it's useful for this, but might be handy sometime.

http://www.gearingcommander.com/

**Captainleeward** · Mar 8, 2015, 11:39 AM

I will check the specks for the motor and see if that is possible THANKS for your input.

I will let you know the out come....:O)

**Captainleeward** · Mar 8, 2015, 02:46 PM

Well that was a good idea but only starts at 41 rpm won't go down in rpm.

**DIYer** · Mar 9, 2015, 09:04 PM

Good, informative sites, GlennR. Although it didn't help the captain much, I'm sure it's going to be a useful reference for someone in the future.

**GlennR** · Mar 9, 2015, 10:05 PM

1 RPM is really slow. You didn't say the size of the motor, but I'm assuming it's not very large since it's 12V.

You might be better off shopping for a gear motor that's already mated & sized to work together. I used to shop at Surpluscenter.com a bit. Sometimes they'd have odd assemblies that sound like what you are looking for. Sometimes odd things like that are cheaper than trying to find good deals on the separate components.

What's a "stepper motor"? That sounds like a slow rpm motor, but I can't remember what they are for. Might be something to look at.

**Doc** · Mar 10, 2015, 03:29 PM

Stepper motors are often found in old printers or many of the cheap Chinese sites for a penny each. They are popular for use in DIY CNC machines, 3D printers or plotters and the like.

They might be perfect for the job.

Try here

Regards

Doc

**Captainleeward** · Mar 12, 2015, 07:00 AM

The size of the motor is 1/4 hp and is as big as a car starter you can see one on my bead roller here.
the easiest solution is to use a larger gear on the motor side. but I don't know if that would do the trick. vurently there is a 60 tooth sprocket on the shaft and a 11 tooth sprocket on the motor.
this gearing is 5.5 rpms.
Next best one is to put a reducer gear box on the shaft to reduce the ratio further.
this motor is 41 rpms I need 1 or 2 rpms. The shaft I'm turning is balanced and does not require much torque.