Center Assembly Lightening

Task Description

The center block and connectors are heavier than they need to be, duplicate the parts and modify them to remove excess material. Note that some of this has already been done, but there is more that can be done to lighten them without sacrificing the strength.

For the drawing tasks:

The center block part is found in COMP2024/X-Frame and is calledC24_X-FRAME_P021_LIGHTENED-CENTER-CONNECTOR, this part is to be made on the mill. You may use CC24_X-FRAME_P021_LIGHTENED-CENTER-CONNECTOR.SLDRW for reference (this is in COMP2024/X-Frame/Drawings which is where your drawing should go as well).

The arm connectors are 2 parts found in COMP2024/X-Frame and are C24_X-FRAME_P020_LIGHTENED-ARM-CONNECTOR and C24_X-FRAME_P022_LIGHTENED-ARM-CONNECTOR. Note these parts are similar but have the hole on the circular face located differently. You may use C24_X-FRAME_P002_ARM-CONNECTOR.SLDDRW and C24_X-FRAME_P006_ARM-CONNECTOR.SLDDRW for reference (these are in COMP2024/X-Frame/Drawings which is where your drawing should go as well).

Constraints

Assignees

Task Progression/Updates

Author: @Nathaniel Li Date: Jan 22, 2024

INITIAL CHANGES

Arm Connector

• Reduced wall thickness of connecting tube by 2mm (inner diameter increased to 15mm)

  • 15.3g → 12.65g while losing 2mm of wall thickness

• Reduced the outer edge square to 22mm x 22mm to match the carbon tube diameter

  • 12.65g → 12.16g

Center Connector

• Extended 4 corner M3 holes to through all

  • 99.81g → 98.24g

• Decreased wall thickness from 6mm to 5mm

  • 98.24g → 84.55g

• Added the opposite (diamond vs square configuration) set of M5 holes to all sides so instead of 4 connecting M5 holes, there are 8

  • 84.55g → 81.47g

Author: @Alison Thompson Date: Jan 22, 2024

CAD REVIEW 1

Arm Connector

• “Reduced wall thickness of connecting tube by 2mm (inner diameter increased to 15mm)”

  • I think these are good, I would like to check IRL what size we have drilled out the holes in the center. I think we may have drilled them out bigger than we did in CAD

• “Reduced the outer edge square to 22mm x 22mm to match the carbon tube diameter”

  • I think this is fine would like another opinion to verify that this won’t mess with structure too much

• Note that there are 2 arm connector parts because of the 2 hole patterns and we wanted the holes to mount the CF tubes to be accessible from the top and bottom of the drone, we will need a lightened version of C24_X-FRAME_P006_ARM-CONNECTOR lightened as well

Center Connector

• “Extended 4 corner M3 holes to through all”

  • need to double check IRL that a drill bit to do this exists, or it will be done as two separate holes in (hopefully) the same spot and connected

  • I think as features in SW it should be two tapped holes that go half way through since they’ll be tapped separately (tapping them separately may also be gross, I want Conall’s opinion on this)

• “Decreased wall thickness from 6mm to 5mm”

  • This is a good change, I don’t love the <1mm clearance for the top M3s, perhaps we go down a endmill size for the corner fillets? Not sure I love that from an actually making it standpoint (it will take a little longer) but I’d like at least ~3mm clearance on that (aka the diameter of the hole) if possible

• “Added the opposite (diamond vs square configuration) set of M5 holes”

  • Not sure how much I like this, the reason the hole pattern is different is to prevent the holes from intersecting

General

These look pretty good, I would like @Conall Kingshott to take a look at these changes as well and give any thoughts. (He has a better grasp on the physics implications of this stuff than I)

Author: @Conall Kingshott Date: Jan 23, 2024

Arm Connector

• “Reduced wall thickness of connecting tube by 2mm (inner diameter increased to 15mm)”

  • Agreed with Alison on checking with IRL

  • Maybe we go to 16mm instead

• “Reduced the outer edge square to 22mm x 22mm to match the carbon tube diameter”

  • Sounds good

• Note that there are 2 arm connector parts because of the 2 hole patterns and we wanted the holes to mount the CF tubes to be accessible from the top and bottom of the drone, we will need a lightened version of C24_X-FRAME_P006_ARM-CONNECTOR lightened as well

  • Agreed, we need to keep the off-set parts to stop the

Center Connector

• “Extended 4 corner M3 holes to through all”

  • We won’t be able to get a drill to do this, and the weight savings are negligible.

• “Decreased wall thickness from 6mm to 5mm”

  • I would like to go down to 4mm if we can, then add a feature to add material around the bolt holes

• “Added the opposite (diamond vs square configuration) set of M5 holes”

  • I would like to remove this

I would like chamfers on the outside edges of the center connector block, should save to decent weight at reasonably low effort.

In future, we should also have new part numbers for any new part. Using the same part # with a different description is not good practice.

Author: @Nathaniel Li Date: Jan 23, 2024

REVISION 1

Arm Connector

• Changed the ID of the connecting tube to 16mm but this needs to be confirmed with the IRL connector to see what size was drilled out.

• The other version of the arm connector (C24_X-FRAME_P006_ARM-CONNECTOR) can be modified to match the changes made once confirmed.

• Weight is down to 10.69g.

Center Connector

• Scrapped all the initial changes.

• Decreased the wall thickness from 6mm to 4mm and increased the radius on the fillet to 12.5mm to supplement the missing material for the corner M3 holes.

  • Note: The new clearance around the top M3s is ~2mm; if 3mm is a must then the radius on the fillet will need to increase to 15mm adding ~5g.

• Put a 5mm symmetric chamfer at 4 corners.

• Weight is down to 76.49g.

Author: @Alison Thompson Date: Jan 24, 2024

CAD REVIEW 2

Arm Connector

• Looks great, I’m happy with these

• Before we manufacture we have to look at the IRL one and find out what the center is drilled out to, it may be an imperial cutter that was bigger than the OG hole in CAD

• Fine by me to add these changes to the other version of the arm connector

Center Connector

• Also looks good!

• I think we should double-check what size long endmills the machine shop has, do you have time to go to the machine shop and show them what we’d like to do for the big cut-out and see what endmills we have access to?

• I’m okay with slightly less than the hole diameter around the 4 top holes, if the endmill for this exists I’m happy with it

• Chamfers look good, I would just add some 1 or 2mm fillets to the edges so it wont be sharp

Are you able to replace these parts in the main assembly so we can double-check for interferences? Since they’re “smaller” than the original they should be all good, I just would like to see them integrated before they’re manufactured.

You can also start working on drawings for these parts so we can begin that review process.

Author: @Conall Kingshott Date: ​Jan 28, 2024

Drawing review:

Open

This looks really good, well done! A few small notes:

• There is one dimension missing for the inside edge of the center cut-out

• It would be good to have the center of the interior rounded features reference dimensioned. This just means when you go to machine the part, you know where to actually put the end-mill and you don't need to do any math.

• I think we’ll probably want to make 2 of these eventually, but that’s super nitpicky.

Drawing Review 2

Open

• I think these just need center marks for the four corners and to have those dimensioned.

• I’m gonna go ahead and say that we can use only mm for these. Also please set them as reference dimensions.

Author: @Conall Kingshott Date: Jan 29, 2024

Arm Connection Drawing Review for @Evan Janakievski

• This is a design thing, not a drawing thing, but I think we should do tight fit on the M5s. You can do this from hole wizard in the part. @Evan Janakievski you can still modify the part.

• Jog on the section view should be a bit further off so you have a bit of a straight line going off the part.

Author: @Alison Thompson Date: ​Mar 6, 2024

Center block made, new weight 59g