RC15-FlatSolenoid

Theory

January 25th, 2015 members of the Mechanical and Elecetrical team sat down in a classroom to talk about the solenoid development.

Mechanical constraints

In the beginning of the conversation, some mechanical constraints were applied, such as:

• A, Crossectional area of the armature. This area is set a bit smaller than the crossectional are of the solenoid, leaving as small of a gap between the walls and the armature.
• Solenoid dimensions were set earlier.

Models

Model #1

Model #1 is the first model considered to describe and analyze the solenoid behavoiur. The main problem of this model was that the armature was viewed only at the instant, when it is completely encompassed in the solenoid. This is a big flaw due to the fact that this model greately limits the travel distance of the armature.

Model #2

The main deviation from model #1 is that the armarture starts only partially inside of the solenoid (the initial guess was halfway through). A big assumption made in this model is that the magnetic field outside of the solenoid is negligeble in comparison to the magnetic field inside of the solenoid (in order words, the magnetic fields exists onlt insde of the solenoid). An important face noticed by from this model is that once a long (longer than the solenoid) armature fills the solenoid, it would stop moving.

Model #3

Model #3 is the most realistic model among the ones presented. The solenoid has a variating magnetic field inside of it and a decreasing magnetic field outside.

Model #4

The design was inspired by Mannheim's solenoid, which is very hard to machine using conventional methods. That is why 3D printing was chosen to manufacture this model. The part is structurally sturdy but lacks the smooth finish required to allow for minimal friction with the armature. Measurements were taken to compare the CAD model to the printed part for error analysis:

Measured location	CAD Model (mm)	Printed Part (mm)
Side plaque height	12.00	12.13
Outside body height	5.50	4.70
Inside body height	4.00	3.60
Plaque length	56.00	55.73
Cutout plaque length	47.80	47.85
Inside length	38.00	37.11
Body length	39.50	38.81
Total width	44.50	44.72

>>>>Important to notice that body area had more error than base plaque (due to warping or shrinkage).

Force Distribution

Using model #3 described above, the force distribuion from the solenoid is non-linear and very complicated. However, understanding this force distribution is very important in order to determine the characteristics needed for most efficiency. As it can be seen in the picture *, the magnetic field is distributed along the field lines; the density of the magnetic field is proportional to the force applied to a charge in that field.

Flat Solenoid armature speed without electrical steel shell (mm/s)

8859

8651

9122

9236

9584

9097

9304

9294

9682

9556

• Outliers underlined

Average Armature Speed (mm/s)

Average (with outliers)	Average (without outliers)
9359.375	9238.5

Flat Solenoid armature speed with electrical steel shell (mm/s)

9579

9410

9147

9363

9753

9471

9685

9646

9477

9134

• Outliers underlined

Average Armature Speed (mm/s)

Average (with outliers)	Average (without outliers)
9548	9466.5