So this year we’ve had 3 mobile goals break on us (and counting). I’m not talking the tree coming loose, I’m talking full plastic *snap* *crackle* *pop* on the bottom:
I think this is due to the robots having an incredible amount of push power with 6 motor drive this year. Also, I’m not saying they were badly designed but… I do think some of this could have been prevented with a bit of extra thought when they were designed.
In lieu of ordering hundreds of dollars in replacement mogos here’s what I came up with as a fix:
- I opened up the VEX Tipping Point Field model and looked at the bottom of the Mogo. I realized we could design a bracket that slots inside. If we glued that in it should help give the whole structure extra strength. The shaft collar on the bottom would prevent it from coming up and the bracket would prevent it from going down. Even if the plastic base broke it would have nowhere to go.
- View Full Mogo Model with additions on Fusion Team
- View Bracket Model only
- Download .STL: MogoSupport_Insert.stl (1.5 MB)
- After figuring out the design in Fusion 360 I 3D printed the bracket.
[0.3 layer height] [10% infill quarter cubic] [PLA].
While printing, I took apart the mogo. Note: The bracket can be glued in without taking the whole mogo apart but I found it easier to apply the glue when it was fully apart.
IMPORTANT: I inserted the broken part back without gluing it before I glued the bracket in place. For now just sort-of let that piece dangle.
- Once the bracket was glued in, I inserted the broken piece back all the way. I hammered it down with a rubber mallet so that it sat flush and then glued it in place, applying glue only to the top and edges. You don’t need to glue the 3d printed part to the broken piece.
For glue I used a 5-10 sec Insta-Cure+ Cyanoacrylate glue which is a VERY strong adhesive. You could probably use any superglue off the shelf but be careful if you have never used superglue before!!! You might think its a joke, but it WILL glue your fingers together.
Put the tree “branch” back in and lock it down with a shaft collar. No glue needed for this step.
Re-assemble all the parts of the mogo.
On the top surface I added a sheet of ABS plastic because I noticed the entire base was starting to crack. As you can tell by now these “mods” are very much NOT legal but since we are only using them for practice from now on I don’t see a problem.
On the top I also added another shaft collar but it needs a washer in order to fit on the post.
MogoTree_Washer.stl (5.1 MB)
This is to help distribute any lateral force so that at least a portion of it is spread out along the base rather than going through the bottom and causing it to pop off. I tried one mogo without adding this washer and it broke again, but it could also be poorly glued.
- As a preventative measure, you could try just adding the top washer and shaft collar and locking it on REALLY TIGHT and even gluing it all together. That might be enough to stop it from breaking in the first place.