FAQ

General questions

 

Question:
I don´t have a Pay Pal account. How do I pay for the book?

Answer:
Just click the Buy now button. If you do not have a Pay Pal account, you will automatically be guided through the necessary steps in order to complete your purchase.

 

Questions regarding Build your own electric motor

 

Question:

I love your work! It is very inspirational. I have one question about motor theory. As you are not using a halbach array, would your motor benefit from a steel back plate for the magnets to complete the magnetic circuit? Or perhaps you use a steel back plate? How much stronger of a field between the gap do you think you might get with steel back plates? Thanks in advance!

Answer:

Steel back plate reduces rpm/V for a given version of the motor with about 20%, making it possible to build an even more efficient motor; it is all in the book!

Question:

I'm very interested in your DIY plans for an axial flux motor, however I would like to build one that could handle 20kW. Does your advanced design illustrated in your new developments do this?

Answer:

I have not tested the motor systematically in a laboratory, but rather in a real world application, namely as a traction motor in a electric motorcycle conversion. In this application the motor handles burst power of 20kW at approximately 1500 rpm. I would not expect the motor to handle 20kW at low rpm like this for longer periods of time. However, running the motor at higher rpm would make it possible to put more power through the motor without overheating it. This could be achieved in different ways, either by going for a higher voltage setup or by winding the coils towards a higher rpm/v. There is also, of course, the possibility to scale up the motor.

 

Question:
I would like to buy your book. Do you have a download version?

Answer:
For the time being the “build your own electric motor” is only available in paper form, which make more sense when using it in a work shop environment.
However the 500W brushless motor building instruction which also covers a simple speed controller can be purchased in a digital pdf version at http://store.payloadz.com/detail_html.asp?Id=823402.

 

Question:
OK, this is amazing. I have a mill, but no lathe. Is a lathe required?

Answer:
No, you do not have to use a lathe in this build. There are two details of the build that could be made in a lathe but it is not necessary in order to achieve a good final result.

 

Question:
I am interested in building my own electric motor for my electric utility vehicle. However, I have some specific motor values (torque and rpm) that I need to achieve. In general, this application requires a low speed high torque motor. Does your book provide the necessary information to determine the coil windings based on the target performance of the motor (Kt and Kv)? Nice work by the way......

Answer:
In the book you will find a rough way of calculating the right lengths of copper wire/coil to require a certain rpm/V. In general the book is a “hands on” building instruction and do not cover the underlying math. However, in the process of building electric motors I have gained a lot of practical experience which I have done my best to put into writing. While speaking of experience, an air core axial flux motor, without proper gearing, would not by my first choice for a low rpm high torque motor.