Universal Motor: Armature and Field vs. Skeleton Frame

February 19, 2013

When your application calls for a motor with a high-speed requirement, high starting torque, or high power density, a universal motor is often a good choice.

What is a skeleton motor and what is the difference between a skeleton motor and a parts set? The differences lie in the universal motor housing and frame construction

If you are looking for a universal motor you will notice that many manufacturers offer different options for different frame sizes and lengths. You will also notice that with some of the frame size options, skeleton motor designs are available. So, what is a skeleton motor and what is the difference between a skeleton motor and a parts set?

Parts Set

A parts set is simply an armature and a field. When a customer purchases a parts set, they must build their own motor housing or mounting. Parts sets are popular options for universal motors because they allow the customer to integrate the motor into their end product in a more efficient way than a standard motor bracket would allow. Groschopp can change the stack length, motor performance, as well as make nearly any type of custom shaft to allow for flexibility to fit inside a custom housing or mounting.

Skeleton Frame

For customers who need a motor to run without building their own housing or integrating the motor mounting into their end product, Groschopp offers skeleton motor options. The so-called skeleton motor is most simply a universal motor parts set held in place by two “U” shaped brackets. The bracket on the commutator end of the motor holds the brush holders which allow for replaceable brushes. The drive end bracket has a mounting face and pilot with custom mounting configurations available. The use of brackets allows the stack length to change, so the entire range of stack lengths are available with the skeleton motor. Like the universal motor parts set, nearly any output shaft configuration is possible.

>> Questions? Learn how to check a motor armature for damaged windings

How to use the Motor Search Tool

Narrow your search by selecting motor type, gearbox, voltage, and phase options for your desired motor.

Select a dominant variable: choose one of the three parameters to narrow your search. The selected variable determines which slider bar you will be able to manually move.

Use the slider corresponding to your dominant variable to further narrow your motor selection. The other sliders will automatically move to show available ranges based on the range of your selected variable.

Results will upload as your search criteria changes. If you have any questions regarding your results or how to use the search tool, you can chat with us using the green tab on the left-hand side of your screen.


Note: Groschopp Universal motors are custom built to fit your application so no additional options are available to narrow the search. Selecting the Universal motor type will prompt a message taking you to the Universal product page.

Not sure what you need?

One of our team members would be happy to help. Contact us at 800-829-4135 or by email at sales@groschopp.com. You can also chat with us using the green tab on the left side of your screen.

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Universal Motors

Groschopp Universal motors are custom built to fit your application so no additional options are available to narrow the search. Standard frame sizes and motor features can be found on the Universal page.

go to Universal page