Mounting Fastener Clearance

[j0n5m1th]

Scenario:

• SystemCore mounted on a 1in dropped SDS chassis, provides ~0.625in ground clearance ignoring the belly pan & fasteners. (similar to the lowering kit)

Pain point:

• The raised body around the mounting holes is too close to support using a nylock nut on top of SystemCore with the screw head underneath.

Why:

• We typically like to mount things to the belly pan by using a button head screw (head underneath the belly pan) and a nylock nut on top to mitigate the risk of damaging the field / field elements / robot (even on standard chassis configurations).

Recommendation:

• Change the profile of the housing so teams can have the option (out of the box) to place a nut on top of the mounting holes.

Examples:

The nut just barely doesn't fit without pushing on the housing:

The profile of the # 8-32 nylock nut vs button head (button head pictured here is a # 10-32 so the expected # 8-32 would be less obtrusive):

Screw length is more important with the nut on the bottom to prevent accidental damage to the field.

• ex. A 0.125in thick belly pan should use a 0.875in screw to minimize exposing the threads. If the nut was on top, then a 1in screw could be used without concern for a belly pan of various thicknesses.

An example of a device that supports this is the REV PDH:

[brettbbonner]

We had the same observation. Use of a button head is highly desirable since the goal is always to minimize protrusions from the belly pan.

[bhjelstrom]

Great feedback @j0n5m1th and @brettbbonner. Are there any objections to simply removing the recesses?

[brettbbonner]

Are there any objections to simply removing the recesses?

Functionally I think that would be OK, but with weight ever more an issue, all the little things add up. Minimizing non-value-adding material is a good thing; I'd rather not have to use bolts that are ~twice as long to hold this device in place. (That said, it's only 4 bolts, so it's really not a big deal if this is the best way to avoid the issue.)

[j0n5m1th]

No objections here.
I would still prefer to keep the recesses if they are reasonable to modify, but removing the recesses would be a good change.

• Removing the recesses would let teams mount this to material up to 1/4in with a standard 1.5in screw & nylock without stressing field damage. Big win.
• Modifying the recesses would allow for the same thing, but for a 1in screw.

I printed a spacer to mock this up. Here's what it looks like with a 1.5in screw & nylock on a 0.125in belly pan.

The only downside I noticed is that people working with wires / ports might inadvertently run their fingers across raised screw threads or have to work around the mounting hardware.