Sayber OSG Forum

The electric motor is the heart of any grinder build. Unfortunately, there many different types and sizes or motors, mechanical and electrical properties. Everything from, drip proof to totally enclosed, pump and compressor motors to DC motors found in treadmills. Dozens of physical and electrical properties can make choosing a motor for your grinder difficult. Luckily NEMA (National Electrical Manufacturers Association) has come up with standards to ensure that manufacturers offer motors that can be interchanged. The properties such as the mounting pattern and shaft diameter are defined by NEMA. This number increases with the physical size of the motor. For example a NEMA 42 frame is smaller than a NEMA 56 frame and both of these are smaller than a NEMA 143 frame. The frame number does not specify the horsepower, however, higher horsepower motors do require larger frames. In addition to the number, there is often a letter associated with the frame type. The letter C means the motor is capable of being "face mounted" versus the foot mounted version without the C. The letter J indicates a threaded shaft and so on.

As mentioned, the letter C means the motor can be face or flange mounted. There are holes in the end of the motor where the shaft comes out that allow the motor to be bolted directly to something, rather than mounted via the motor's foot mounts.

The DC1 uses a NEMA 56C motor. Why NEMA 56C?

NEMA 56C motors are popular in small equipment and generally range from 1/2 horsepower to 3 horsepower. This is a great range for use in a belt grinder. The C face motor has a couple of advantages when designing a belt grinder. It eliminates having to adjust the motor on two dimensions (up and down and front and back). This greatly reduces alignment and tracking issues. It also reduces vibration issues as the motor is directly connected to the mass of the grinder frame.

One problem with a NEMA standard is that it doe not define the diameter or length of the motor. Each manufacturer can make the diameter and length of the motors they wish as long as it mounts as per the standard. I have seen 56C motors that are 9.5" long and some that are almost 12" long.

This is why it's really important to know the motor you are using before getting the metalwork for the grinder frame cut.

Regards,

Dan

Hi Dan

Is NEMA an American standard as I can't seem to find any nema 56c motors in the UK?

Thanks
Craig

Yes, NEMA is commonly used in North America. You're probably seeing a lot of IEC (International Electrotechnical Commission) motors. These can be used, but the "metric" version of the OSG will have to get sorted out first. Some kind folks in Australia were willing to convert the files. Hopefully we can have something metric up soon.

Dan

Hi Dan

I had a look at some motors at my work and comparing the nema 56c with an IEC motor the issue I see is the junction box is too close to the motor flange to be able to mount properly with the current design I will have a mess around with the cad file and see if I can alter it to make it fit

Thanks
Craig

Hi Dan

I have started converting the cad drawing to suit an IEC 80 B14 motor could you have a wee look at the file when you get a minute and see if you think it will work thank you

Craig

Thanks Craig,

It looks good. I took some dims from Baldor's specs and checked the B14 face. 100 mm diameter bolt pattern (check). 2H is 160 mm and you've got some room there with 170 mm (check). Do you have some ideas on the M fasteners you want to use? I could check then as well as the tap holes.

Thanks so much for doing this. Wonderful!

Dan

For reference:
http://www.baldor.com/~/media/files/bra ... cover.ashx

Dan