Pedal Box Validation
Calculators used:
Sohan’s complete brake calc: https://utexas.sharepoint.com/:x:/s/ENGR-LonghornRacing/EVxC8xs6ChlAsd5R1O0OeO4BtPIHEOnMeWev7deY4QZx8Q?e=RGLw2H
Advait’s Travel Calc: Master Cylinder Travel Calculator - Google Sheets
Data/Calcs Planning
neutral axes of bolts are not on the same x-z plane. (diff y val)
Assumed driver force acts perpendicular to pedal face
Line of action of driver force intersects “neutral line” so able to use for sum moments
Hand Calcs - Statics
Hand Calcs - Bearing, Tearout, and Hertzians
Shigley’s Notes:
Notes: use Left MC and Right MC results (second pic), as they:
Account for true x and true y, ANSYS will easily be able to recognize these forces
Account for brake bias
LEFT MC
Current F_mcx = 2318.5 N
Current F_mcy = 616.06 N
RIGHT MC
Current F_mcx = 1248.44 N
Current F_mcy = 331.7 N
Singularity function calcs (on quad/quint shear bolt)
Pedal Box Brake Pedal - Sim Setup
1 - Splitting 225 lbf driver applied force
See the above “Data/Calcs Planning” section
31.29 degrees from max compression (balance bar front face 0.57in away from mc rubber pad front face)
Sim setup
Pre-Mechanical setup
Set up the brake pedal at its “max compression” location in SOLIDWORKS
Export the brake pedal (pedal body and pedal face) as a step file to ANSYS
Add 6061 t6 as a material
Go into spaceclaim and make split lines between the pedal face and the pedal
Project the pedal face’s inner faces (where the body is inserted into the pedal face) onto the body
Can alternatively share these bodies. Will also automatically bond them in mechanical
Mechanical Setup
Make pedal body and face 6061 t6
Bonded contact the body and face together at the splits created in the previous setup section
Meshes:
Pedal Face: 2mm tet
Pedal Body: 2mm tet
Scope the pivot point as a body to ground revolute joint
Remote displacement (all DoF = 0) to balance bar hole
Apply driver force calculated in previous section to the entirety of the pedal face (i used 225lbf)
Pedal Box MC Bolt - Sim Setup
TRIAL 2 (1 was a crazy fail not worth putting here)
1 - Workbench Preparation
Can use anything for bolts, just make sure to check that the stress experienced isn’t greater than the 0.6*yield str of grade 8 bolts
6061 for baseplate and tabs
Ti for spherical bearings so you can actually apply a force
Setting a body as rigid doesn’t allow force application
2 - Geometry Prep (SolidWorks)
IMPORTANT: MAKE SURE YOU ARE READ ONLY OR ON A COPY OF THE ASM WHILE DOING THIS. DO NOT HAVE THE FILE CHECKED OUT.
Remove everything from the model, except for:
Baseplate
MC Bolt
MC Spherical Bearings
MC Tabs
threads on the bolt screw
Suppress them by “opening part in position”
This method will follow for all future suppresses done on read only files.
Tip: Shift click and ctrl select allow u to select multiple bodies and hide them at once
It should look smt like this:
3 - Feature Removal for Mesh Optimization (SolidWorks)
The following features should be removed:
holes EXCEPT for the leftmost and rightmost six bolt holes on baseplate so you can sweep hex-dom mesh it
Result:
Cuts in the hexnut
Result:
Unnecessary features on the bolt (like the grade 8 marking)
Result:
For Each L-Tab
Ideally, remove the holes that connect it to the baseplate. I couldn’t tho because suppressing/hiding those nonessential holes hid/removed essential geometry that was referenced off the holes.
Some holes can be removed by going into the sketch, like the second image under this section
Remove the fillets far from the bolt
Result:
Fully Prepared Model:
Make sure to pan/rotate all around the model to check and see if you missed any unnecessary features or parts
Export this as a AP203 stp file (parasolid is not working nowadays)
Make sure to press no when solidworks asks if you want suppressed/hidden bodies resolved
4 - Importing into ANSYS
Tips:
Whenever updating geometry (ex u missed smt small like a ball bearing) and go to replace the AP203 stp file, do NOT name the file the same thing and replace it.
ANSYS does not recognize that this new file is different
Instead, rename your file to “… _VX” (X being iteration number)
If storage space is a concern, delete the old iteration of the AP203 stp file
Reread upstream data whenever model gets updated AND you want those changes to be reflected
Upon opening Mechanical following an update to the geometry, scoping attachments will be lost.
Make sure to carefully check that any scoping attachments match (Joints, Contacts) how you wish, and remove the unnecessary ones.
5 - Material Assignment
The following should be 6061 Al
Baseplate
4 tabs (baseplate → mc)
The bolt and nut should be 4130 steel normalized
or another metal, as said in (0), this is to crosscheck with the YTS and UTS of grade 8 shear
The spherical bearings should be titanium alloy
They are a load transfer mechanism rather than a body we are actively analyzing for failure
Notes:
All materials listed can be found from Min Materials xml file
6 - Joints
Right click joints, insert joint.
Spherical Joints
Reference the bolt
Mobile the spherical bearing of the MC
7 - Contacts
For all, right click contacts, insert manual contact region.
Bonded:
flexnut backface to rightmost tab
flexnut interior hole to bolt
bottom side of bolt head to leftmost tab
Tabs to bottom of baseplate
Frictionless
Between bolt and hole of middle left and middle right tab
8 - Boundary Conditions
Compression Only Support
All bottom faces of the tabs
think about this as:
driver pressing down on the baseplate or the pedal
causing the pedal box to move downwards
and the belly pan thus provides a reactionary force
Fixed Support
This is the place the bolts go and lock down the baseplate to the 4130 plates under it, allowing for welding to the square frame tubes
9 - Force Application
Reference Hand Calcs in (0) for true x and true y on each spherical bearing
Make sure that when you insert the force, your “Define By” is set to components. Applying forces i’ve calc’d is easier this way.
IMPORTANT NOTES:
THE FORCES LISTED IN (0) ARE MAGNITUDES.
X dir is positive, y dir is negative
IN ANSYS, THE X GOES IN A DIFFERENT DIRECTION. USE Z DIRECTION INSTEAD.
Check little red arrow on your spherical bearings to make sure the force direction makes sense
10 - Meshing
Always right click “Mesh” → Show → Sweepable bodies. Sweepable bodies are cool bc they’re easy for ANSYS to create a quality mesh out of.
Make sure you are in units of mm, kg, s, N, … This will make your life so much easier, because we are not looking for meter-size meshes.
Your overall mesh size is controlled by the Mesh category in your feature tree. Change it to 1mm.
This will help with tetrahedron meshes
Select body mode should be on. You NEVER want to face mesh.
Sweeps
Baseplate - 2mm. Only sweepable body found that time around
Insert → Method
ANSYS should create an automatic method.
in it’s feature window (bottom left of screen), Method → sweep
And, Type → Element Size. Now set to 2mm.
Tetrahedrons
Insert → Method
It should create an automatic method.
in it’s feature window (bottom left of screen), Method → tetrahedrons
1mm size (its controlled by the overall mesh category so you should be fine)
Body Sizing
Element size, 2mm
All the tabs