Linear motor references

1.  DIY tubular linear motor: https://hackaday.io/project/202245-diy-tubular-linear-motor
2. Kollmorgen iron less linear drive: https://www.kollmorgen.com/en-us/products/motors/direct-drive/direct-drive-linear
3. PCB linear motors: https://hackaday.com/2022/05/19/pcb-linear-motors-for-model-trains/
4. HP drive circuit details: https://archive.org/details/hp_journal_1979-02/page/n23/mode/2up
5. 2D planar actuator:https://hackaday.com/2018/05/22/smiling-robot-moves-without-wires/
6. 2D planar actuator 2014: https://hackaday.com/2014/04/23/micro-robots-are-scary-awesome/
7. Tolomatic, Irisdynamics
   
   
   

#12 Helicopter design

 

Hand drawing of the main hub of helicopter with integrated motor

Hand drawing of the main hub of helicopter with integrated motor

LHS46: Maxwell's four laws + 2 force equations

Force equation for Lorentz force left hand thumb rule 

is the force on a current carrying loop of fire in a magnetic field force is equal to NAB Omega sine Omega T where

Force equation considering reluctance force for a permanent magnet

F = B2A_sp/mu_0

Maxwell's first law

Gauss magnetic field law 

The net magnetic field over a closed surface, will be 0 because the magnetic poles exist only as a dipole

Maxwell's second law 

This law is called the Gauss electric field law

the net electric field over a closed surface need not be zero because electric monopoles exist. It will be a function of included electric charges inside the closed surface

Maxwell's 3rd law 

Faradays generator law

V = NAB omega sin omega T

Maxwell's 4th law 

this law is also called ampere circuit law 

it relates the Magnetic field intensity H around a conductor to the current flowing in the conductor and radius at which H is measured. 

Vibhatsu Technologies

1.  Could interact with one of the employees while going from Challaghatta to Murugeshpalaya
2. Vibhatsu is a Bangalore startup
3. Mainly bids on FPGA development
4. Deploys contract engineers to the "Certain agencies" directly for development in the client place itself.
5. Does not give transport for the contract engineers to return from the "Certain agencies" to Murugeshpalaya
6. Currently doing a 10G FTP offloader for "Certain agencies" 
7. Average contract value for a FPGA development is of the order of 50 Lakhs INR.

Bearing scheme for 30,000 RPM rotor: Guide lines

1. Radial deep groove ball bearings are commonly used in machineries
2.  Radial deep groove ball bearings contact angle is 8°. So it can take low axial load, compared to the radial load it can take. 
3. Radial deep groove ball bearings typically used with a separate thrust bearing.
4. Radial deep groove ball bearings  speeds are low as the balls are not in contact with both the races all the time. There is a clearance between outer race and balls.
5. Radial deep groove ball bearings  clearance between outer race and balls is given in the bearing number it self.
6. Fans, blowers, electric motors use Radial deep groove ball bearings 

 

1. Spindle bearing and angular contact ball bearings are the same. Two names of the same thing. So don't search radial spindle bearing.
2.  Spindle bearings have contact angle between 16-25°. So they can take higher axial load, in only one direction, compared to radial deep groove ball bearing. 
3. Spindle bearings need to be bought in pairs, to take load in both the directions, axially
4. Spindle bearing  are preloaded, so the balls are always in contact with both the races. So the speeds are higher compared to Radial deep groove ball bearings 
5.  cnc machine tool spindles and high speed rotors use angular contact ball bearing .

 

1.  If span between bearing is high and thermal expansion contraction are significant, one side bearing has to be fixed and other side has to be free for sliding. 
2. Fixed side bearing can be
1. Deep groove ball bearing
2. Matched pair or stack angular contact ball bearing
3. Double-row angular contact ball bearing
4. Self-aligning ball bearing
5. Cylindrical roller bearing with rib (NUP and NH types) 
3. Bearings which accommodate radial load only and whose inner and outer rings are separable are recommended as free side bearings.In general, if non-separable bearings are used on free side, clearance fit is provided between outer ring and housing to compensate for shaft movement through bearings. In some cases, clearance fit between shaft and inner ring is utilized.
4. Free side bearings can be:
1. Cylindrical roller bearing (NU and N types): Separable type
2. Needle roller bearing(NA type, etc.): Separable type
3. Deep groove ball bearing, clearance fit, Non-separable type
4. Matched pair angular contact ball bearing, Back-to-back arrangement, clearance fit, Non-separable type
5. Double-row angular contact ball bearing, clearance fit, Non-separable type

Optimum bearing arrangement for me is, back to back, angular contact type, example 13 in 

https://koyo.jtekt.co.jp/en/support/bearing-knowledge/4-0000.html

Shims are required on this type: "After mounting, the axial clearance is adjusted using nuts or shims. "

To avoid having shims, better to have a outer coaxial tube that with hold the outer race. This tube will transfer load from outer race to outer race axially. 

Clamp the outer coaxial non rotating tube on plummer blocks. Use lock nut with locking washer with a grove cut on the thread for the locking washer tab.

Similar arrangement is already there in page 31/70, https://www.cedengineering.com/userfiles/Ball%20Bearing%20Design%20and%20Applications%20R1.pdf

 

Timken clearly gives mounting arrangement: https://www.timken.com/resources/timken-angular-contact-ball-bearing-catalog_11193/

 

Similar arrangement with additional deep grove bearing on one side is also available as a standard product : https://in.misumi-ec.com/pdf/fa/2014/p1_985_001.pdf

 

For preloading details: see https://koyo.jtekt.co.jp/en/support/bearing-knowledge/11-2000.html

Decide between matched and universally matched bearings.