2021-12-02 Meeting Minutes - Drivetrain
Goals
- Discuss member commitment for Winter term?
- Discuss plan for manufacturing Drivetrain
- DFM tips/standards we want to agree on?
- Ordering plan (in more detail)
- Due dates
- When to have final CAD changes in:
- When to have final BOM ready: Dec. 13th
- Export to Excel from Solidworks → Ethan tutorial Wed.
- Will decide what we need to order ASAP
- When to have all drawings done: Jan 4th?
- Bonding update
Manufacturing Breakdown
Chassis
Demtool...
- Chassis plates → laser cut
- Potentially carbon fibre mounting tubes
- Middle connector block
- Lower priority: chassis connector blocks
In-house...
- Quarter mounting blocks
- Rocker top block
- Gimbal stand sheet metal plates and brackets
- Gimbal/antenna plate
- Suspension connectors
Notes...
- Compromise: make lightening pattern not as dense, room to add holes as we go
- Remember this doesn't have to be
Suspension
Wheel Hubs
3D Printing Sponsor...
- Wheel hubs
Demtool...
- Motor support piece
In-house...
- Wheel-carbon fibre connector
Differential
Demtool...
In-house...
- Eye joint mounts (x4) -> waterjet, then mill down faces, add PEMs to some
- Diff shaft mount (x1) -> waterjet
- Nylon blocks (x2) -> mill slot, then slice, do holes for heat set inserts, add heat set inserts
- Diff shaft -> cut, do retaining ring groove on lathe, drill and tap end
- Turn buckles -> cut, thread
- 3/8" bar (x1) -> or routed
- Chassis mount
Update & Action Items
| Member | Commitment for Winter | Update | Action Items |
|---|---|---|---|
| a4tersig@uwaterloo.ca (Unlicensed) (Chassis) | 6-10 hrs/week? | ||
| amillsem@uwaterloo.ca (Wheel connections) |
| ||
| Emily Adam (Differential bar) | 6-10 hrs/week? | ||
| mapitzgr@uwaterloo.ca (Frame/structure) | ? |
| |
| cchaikla@uwaterloo.ca |
........we need to recruit.............
- Karan?
- Elizabeth?
New Tasks
- Everyone: finish manufacturing CAD
- Create BOM after Ethan spheel
- Start making drawings!
General Notes
- Standard tolerances for machining are +/- 0.005"
- Inside bend radii should be equal to or larger than the material thickness being
used - The simplified formula dictating the shortest flange length is 4x the material
thickness from the bend line - When designing hole locations on sheet metal, use the above 4x material thickness
from bend line rule - Holes are best drawn at mid-tolerance. This means the mid point between the range of acceptable deviation
- Holes intended for tapping in up to 1/2” thick steel should be drawn at the exact tap drill size
- Protocase tips! → Note: they have tables outlining compatible tolerances, materials, etc. following up on all of these tips
- Self-sinching fasteners need to be harder than the material they are being inserted into
- Generally, 400-series stainless steel are good
- They have PEM nuts, standoffs, and studs :O
- The larger the internal radii, the faster the machine can cut
- Make internal radii as large as the design can allow, or reference Protocase's minimum radius table
- Chamfers > fillets for external corners/edges
- In general, don't make tight tolerance where not needed
- For tapped holes, drilled hole length will equal the desired thread depth + length of tap's taper + some additional thread allowance. Keep in mind.
- Going for a smaller thread depth decreases costs
- 6061 aluminum is best if the part needs to be machined. 5052 for sheet and plate metal as it is the strongest of the non-heat-treatable alloys
- To check out:
- Self-sinching fasteners need to be harder than the material they are being inserted into
- Other places with resources: Fictiv, Protolabs
- Tips from Mechanical peeps
- Four decimals for millimeters is pretty much impossible
- Austin's rule of thumbs (metric):
- Hole locations → 3 decimals
- Surfaces/shapes, less critical → 2 decimals
- For COTS, check if they have recommended ISO fits or housing fits
- Min. 3 thread engagement, but ideally more → 1.5x bolt diameter for threaded holes
- If we need a specific hole size on the waterjet, better to undercut and then drill it out
- Use relief notches to move the bend radius
- Specific numbers can be found from Protolabs, Protocase, etc.
- Specify ISO fits for critical dimensions. Can use ISO calculator and ISO preferred fits for personal reference
- Student machine shop mills have a bolt radius tool !!! And multiple datums
- M4/5 for basic mounting, M3 for small, M6/8 for big
- Flanged socket heads!!!!!
- Check out PEM nuts requirements on Penn Engineering website
- Preloading is what the clamping force comes from, preload above vibrational rating