EXP Motor Design Issue

[MrWare]

Hi, I just wanted to post this here to get as many eyes on the issue as possible.
I submitted this to [email protected]

Hello

I just wanted to submit some feedback concerning the 5.5W EXP Motors.

I am having a lot of motors being damaged due to improper installation.
If the motors are mistakenly mounted using the 1.5in screws (I have actually removed all 1.5in screws from my kits because this was happening so often)
Or if you mount the motor with the 1in screw & don’t put the bearing flat under the motor.
Damage will occur

The screw goes all the way through the threaded portion of the motor and hits the small circuit board inside the motor.

This isn’t so much a defect with the motors as much as a design suggestion.

The following would be my suggestion

Include a built in bearing flat on the motor.
Change the threaded portion of the motor to one with a capped end on the inside (Currently the thread go all the way through)
Reinforce the inside of the motor to protect the board

Demonstration images show what happens if the bearing flat is not used with a 1in screw.

I understand that this isn’t completely VEX’s fault, but we are working with teenagers afterall.
No matter how many times you tell them not to do something, or explain an issue, they are still gonna inevitably do it.

[jpearman]

Wow.

so students have screwed in a screw. met resistance and kept on going until it broke through the plastic inside cover, which is quite hard to do.

[MrWare]

Yes

But this is also my fault as well, in an attempt to make building easier I invested in some low speed electric screwdrivers. Nothing too powerful & I glued the torq settings in place in an attempt to mitigate overtightening, but some of the torq rings on the screwdrivers have broken free.

Lesson learned the hard way.

[bkahl]

Thanks for sharing here as well. We were made aware of this issue a bit ago, now.

A running change was instituted on the motor cap to include ribbing where the screws were able to potentially punch through that plastic. This ribbing helps to prevent the exact failure you have shown in the attached pictures. Our testing showed this made it significantly more challenging for the plastic part to fail in the way you have shown.

Obviously this will still be something to watch out for on 5.5W motors that are already existing, and teams will want to check on any new motors as they receive them (it will take us a bit to clear out of all stock that uses the revision of the motor cap shown above) for the near future. Eventually, any new 5.5W motor teams order will have a more reinforced cap to help prevent this.