Jarvis – Body Building

Its high time my suspension and my wheels got connected to a chassis . We need a place to house all the electronics and general payload of the robot . I used Fusion360 to put together some rough designs that used 2020 extrusions and milled plates to build a chassis.

One of these days I’ll remember to screenshot at the time and not just take a picture on my phone.

The basic layout so far looks like this, with plates I am going to mill on the Shapeoko and then I will connect these plates with the extrusions. The suspension will mount to the middle sections with some 3d printed components.

I did not loke the finish on these plates, but I think it was more the wood I was using and the fact I used an upcut endmill than the machine’s fault. In hindsight a down cut would have been better. There is a good post here that explains the difference: How To Choose Solid Carbide Spiral Router Bits | Infinity Cutting Tools Blog (infinitytools.com)

It takes a lot of balls to play golf the way I do…

At this point a few things are starting to glare me in the face:

  1. this robot is wider than it is tall (doesn’t look cool)
  2. it has ground clearance challenges because the suspension protrudes lower than the hubs
  3. the plates don’t attach well to the extrusions, and there is a lot of flex

This badly shot video shows how well it scales over objects:

Not willing to stop doing a bad design to death I wanted to at least get some forward motion happening and try and learn all I could from this platform. I added back the steppers so I could try moving the robot

Here’s a look at the underside

and here’s a side profile

I am very proud of what I’ve made here, but it is not perfect. So I think I am in for some pondering. I need to decide where I go from here. I have some ideas, and I’ll reuse some of my parts here but I think my next post will have things starting to look a lot different.

Jarvis – Lets talk DriveTrain

I am very keen on having four wheel pairs that are powered by one motor each. So four Motors, 8 wheels. The next part of my design would be in trying out different approaches to achieve this. Being a 3d printing veteran I have many GT2 Pulleys and belts laying around and so my first thought is to grab some of those and see if I can make something work with what I have.

First draft of a two wheel, one motor ‘pinched belt’ drive

My first iteration was what you see above. I used pulleys to ‘pinch’ the belt around each wheel to maximize the contact surface and hopefully reduce slipping. I also added a slider (slot on the left) to add a tensioning pulley as well to make sure the arrangement stayed tight.

Iterate, Iterate Iterate, The more I play with the design, the more I wanted to change it, I found calculating the required belt lengths very difficult with the complex arrangement and the resulting trial and error quite difficult. I wanted to try and maintain the size of my design but making things fit was a squeeze.

In the end I found the arrangement above to work quite well – if I could stop the pulleys from toppling over before putting the top on. I was happy enough to live with it for the moment until the wheels arrived ….