Thanks so much for the tip! I just looked up threaded brass heat-sink inserts and did some reading. Very impressed! I'll absolutely have to have a go at that
Now that I had the frame and leg substructures assembled it was time to mount the legs to the frame!
In my R2D2 build I used shoulder bolts, however to get them in the length I needed for Chopper proved to be far too expensive, so I decided to make my own
As you can see below it consists of a quite standard M10 bolt. I then found an aluminium tube that fits perfectly to the bolts. It's not too tight and not loose, so I couldn't have asked for a better find! I then added in a couple washers and I'm pleased to say the bolt assembled very nicely.
Now that I had the bolts, I commenced with assembling the part for attaching the leg. This started with sliding the bolts through the openings in the legs as you can see below:
With the bolts in I slid on the first 3D printed part. This part is from the shoulder piece assembly, it may look odd currently, but it will make sense in a few posts time
Next was the shoulder connection hub that I modelled up that acts as a giant spacer between the aluminium frame and the leg assembly
And finally here you can see the leg attached and bolted on with nyloc nuts. you can also see a glimpse of how the 3D printed skin wraps around the frame and the legs connector hub
For the time being I won't be implementing motors as my R2D2 build is getting that attention. With that in mind I designed a simple drive design that can be modified and upgraded in the future should I decide to implement an RC drive system.
The current set up is very simple, it consists of 2 main wheels at the front followed by a locking castor wheel in the back.
With the outer feet sorted I worked on the mounting system for the centre foot/castor wheel.
The mounting plate of the castor wheel needs to mount onto the angled bottom surface of the frame, so I designed and angled adaptor that allowed me to mount the castor through the frame to a level surface with bolts.
Chopper now has all the parts for his first leg printed, which means I can show how I designed the parts for assembly.
I’ve put together a short video below for you all that shows it all and how all the parts fit together, and I have also posted photos of each step accompanied by a written description.
To start off with these are all the parts ready for assembly. This includes the aluminium leg that I showed earlier in the thread, all the 3D printed parts that sleeve around the Aluminium leg and then the custom shoulder bolts for mounting the leg to the frame.
First step is to sleeve this cylindrical piece down the leg. I designed this to have slots underneath that allow the printed part to have a spot on friction fit onto the 3mm aluminium plates that make up front and backside side of the aluminium leg.
Next up is the middle detail section, this simply slides down the leg and then sits neatly inside the cylindrical piece that's already seated at the bottom.
Now that these first two printed parts are on, it's time to insert the shoulder bolts.
Following the shoulder bolts, the backing plate for the top shoulder piece is inserted along with the shoulder to frame connection hub.
The next stage involves attaching the struts that run up either side of the leg. I've designed these to incorporate an aluminium rod the runs the length of the inside of the part for strength. This rod also protrudes from either end which allows for friction fitting it to the other parts.
As demonstrated below, the producing pins pop straight into the pre-existing mounting holes that are on the cylindrical bottom piece.
With all the parts above sorted it's time for sliding on the main shoulder piece.
I'm particular pleased with this as it has grooves so that it slides seamlessly past the shoulder bolts and around the backing plate on the other side.
As you can see here the shoulder pieces it designed to sleeve around the aluminium leg and the backing plate/connection hub perfectly.
The purpose is this is it allows the shoulder piece to be slid off at any time so I can quickly and easily access the shoulder bolts which is very handy!
And then of course, here's the assembled leg ready to be attached to the frame and the corresponding outer foot
I love modular designs. Makes updating, repairing, or replacing parts so much easier. The design of the leg looks great!
How thick is the shoulder piece that is between the leg and the body? I imagine that will undergo a good bit of compression when bolted down and deal with a fair bit of torque both rotationally and laterally during droid movement.
Thanks so much mate! I'm really pleased with how it's all come together.
And that's a fantastic question, I also had those concerns. With the specific 3D printed part that acts as the main coupler between the leg and the body I bumped up the infill percentage to help add some extra rigidity and see if that would do the trick. So far, it's working great and far better than I thought it would. It's a hefty chunk of plastic considering it was 3D printed, but that increased infill percentage is working wonders.
I'll keep the thread posted as to whether if it fails as I'm interested to see how it holds up! If it fails, I'll resort to a different material
The first big test assembly is complete! Chopper is coming together nicely now with only a few parts left to 3D print. I started this as a project to keep me busy during Covid self-isolating, so everything was 3D modelled, designed and built from scratch by me and after all that work I'm super excited to see him standing and rolling around now.
Next up is printing the feet, battery boxes, skirt and the trim for the bottom of the skins.
Nice. Even if the shoulder pieces ever have issues you can just print up another set with minor changes. Rapid prototyping and testing stuff in the field to make improvements is one of the best parts of having your own printers.
You're absolutely bang on Chris, makes stuff like this way easier to prototype and iterate.
And he is indeed quite light for the size which is a nice surprise. With the head off I can lift with one arm easily enough by the frame which is very handy!
Some more progress on chopper, he now has proper feet.
I was able to fit the entire part in as a single piece 3D print. This was the largest part individual I've printed so far on my printer and I was super impressed with the quality and minimal warping for the size.
In the first photo you can see it as it just finished printing with all the supports intact still:
Next comes some basic clean up, removing all raft with my scraper followed by the printing supports:
And then here's how the part looks! Very pleased with the result.
Only part left for the door shells is some small trim/detail pieces and the 'battery boxes' that connect to the sides.
Comments
I'll absolutely have to have a go at that
That water jet video is great. I want one!
/Chris
I have some more exciting progress to document
Chopper now has all the parts for his first leg printed, which means I can show how I designed the parts for assembly.
I’ve put together a short video below for you all that shows it all and how all the parts fit together, and I have also posted photos of each step accompanied by a written description.
To start off with these are all the parts ready for assembly. This includes the aluminium leg that I showed earlier in the thread, all the 3D printed parts that sleeve around the Aluminium leg and then the custom shoulder bolts for mounting the leg to the frame.
First step is to sleeve this cylindrical piece down the leg. I designed this to have slots underneath that allow the printed part to have a spot on friction fit onto the 3mm aluminium plates that make up front and backside side of the aluminium leg.
Next up is the middle detail section, this simply slides down the leg and then sits neatly inside the cylindrical piece that's already seated at the bottom.
Now that these first two printed parts are on, it's time to insert the shoulder bolts.
Following the shoulder bolts, the backing plate for the top shoulder piece is inserted along with the shoulder to frame connection hub.
The next stage involves attaching the struts that run up either side of the leg. I've designed these to incorporate an aluminium rod the runs the length of the inside of the part for strength. This rod also protrudes from either end which allows for friction fitting it to the other parts.
As demonstrated below, the producing pins pop straight into the pre-existing mounting holes that are on the cylindrical bottom piece.
With all the parts above sorted it's time for sliding on the main shoulder piece.
I'm particular pleased with this as it has grooves so that it slides seamlessly past the shoulder bolts and around the backing plate on the other side.
As you can see here the shoulder pieces it designed to sleeve around the aluminium leg and the backing plate/connection hub perfectly.
The purpose is this is it allows the shoulder piece to be slid off at any time so I can quickly and easily access the shoulder bolts which is very handy!
And then of course, here's the assembled leg ready to be attached to the frame and the corresponding outer foot
How thick is the shoulder piece that is between the leg and the body? I imagine that will undergo a good bit of compression when bolted down and deal with a fair bit of torque both rotationally and laterally during droid movement.
/Chris
Thanks so much mate! I'm really pleased with how it's all come together.
And that's a fantastic question, I also had those concerns.
With the specific 3D printed part that acts as the main coupler between the leg and the body I bumped up the infill percentage to help add some extra rigidity and see if that would do the trick. So far, it's working great and far better than I thought it would. It's a hefty chunk of plastic considering it was 3D printed, but that increased infill percentage is working wonders.
I'll keep the thread posted as to whether if it fails as I'm interested to see how it holds up! If it fails, I'll resort to a different material
And while I'm at it, here's a quick video of him in motion
I am pushing him around, but it's awesome to see Chopper properly rolling!
Based on how he's moving he looks nice and light!
/Chris
And he is indeed quite light for the size which is a nice surprise.
With the head off I can lift with one arm easily enough by the frame which is very handy!
Some more progress on chopper, he now has proper feet.
I was able to fit the entire part in as a single piece 3D print. This was the largest part individual I've printed so far on my printer and I was super impressed with the quality and minimal warping for the size.
In the first photo you can see it as it just finished printing with all the supports intact still:
Next comes some basic clean up, removing all raft with my scraper followed by the printing supports:
And then here's how the part looks! Very pleased with the result.
Only part left for the door shells is some small trim/detail pieces and the 'battery boxes' that connect to the sides.
/Chris