Side Mission: Team Associated SC10 forward receiver box

[Spksh]

For reasons (TLDR: the servo I want to use doesn't have a long enough lead) I want to move the kit receiver box on my SC10 all the way to the front bulkhead.

Here's the kit layout. That's a lot of exposed () wiring.

There are two interesting constraints for the geometry I have to design. The first is that the battery strap throws its elbows out like this:

The second challenge is just the amount of geometry that meets at the front bulkhead. You've got a big sweeping curve of the chassis sidewall, you've got the battery strap post, and you've got the gull wing up angle of the chassis tub. There's also the height of the receiver to account for.

But I really want that receiver box up the front.

 

[Spksh]

I know I won't get this right the first (or 15th) time, and admitting that up front is going to help my normal "it must be perfect!" voice stay a slightly quieter. I have to start somewhere, so let's pick something that's easy to measure.

These angle gauges are stupid-cheap on all the usual sites, and they're really helpful when you're just trying to get close.

I don't have a photo of this, but I measured both the chassis tub wing and the bottom of the receiver box as 82.5 degrees.

Let's whip up a little test block and see how close we are, and then use that to start taking some more relative measurements.

At this point in the process, I'd convinced myself I need the receiver box to extend into the front right pocket in the chassis, just like the kit box does at the rear.

We're starting to look like a real thing.

 

[Spksh]

Alright, let's see if we can wrap around that battery strap post.

It fits... okay. I'm feeling the limitations of my measuring precision

What's the solution? Try a few more times with increasing tolerances!

 

[Spksh]

When I got close enough, I hollowed the shape out to get a feel for how much space I was working with. Easy to think you've got a ton of elbow room when you're deep in CAD, but reality says that this is tiny.

Let's cut off the front, because it's just useless space. But if I want the main compartment to be longer and wider, I'm going to have to deal with that chassis sidewall curve. What's a poor Spksh to do?

 

[WickedFog]

When I got close enough, I hollowed the shape out to get a feel for how much space I was working with. Easy to think you've got a ton of elbow room when you're deep in CAD, but reality says that this is tiny.
View attachment 265087

Let's cut off the front, because it's just useless space. But if I want the main compartment to be longer and wider, I'm going to have to deal with that chassis sidewall curve. What's a poor Spksh to do?

Reverse engineering at it's finest

 

[Doom!]

Carry on, that's what your going to do!

 

[Spksh]

Reverse engineering at it's finest

If this is what I do for fun, imagine what I do for work

 

[Spksh]

Carry on, that's what your going to do!

 

[Spksh]

While I was prototyping manually, this little cutie showed up on my local auction site for <25% of retail, with very little use. It's an Einscan SP v1, with phenomenal accuracy and precision. There's a v2 model out now, but really that's just a different USB socket on the back for slightly faster data transfer. So yeah, I bought it.

After figuring out some scanning spray (this was AE's Black Album era), this was my first scan:

It's hard to articulate how easy this was. Push button, receive point cloud.

And what was really cool to find out is that some of the key measurements I'd taken by hand were dead-on.

 

[WickedFog]

If this is what I do for fun, imagine what I do for work

I bet. We got to take military RC airplanes and destroy them to reverse engineer them. A little over a million dollars worth of carbon fiber RC airplanes - destroyed, ripped to shreds, cut in half, etc. It was such a sad day. I wish I was able to get pics of the engineering office. It looked like a carbon fiber RC airplane demolision derby had gone on there, and nothing survived. There were like 6 of them with about a 5' wingspan, and these smaller ones that had a 3' wingspan. Baddest RC's I've ever seen!

They had a laser scanner there accurate to with .0002" also. I drooled over that bad boy every time they brought it out. Man, the time I could have with that thing!

 

[Spksh]

They had a laser scanner there accurate to with .0002" also. I drooled over that bad boy every time they brought it out. Man, the time I could have with that thing!

Scan all the things!

 

[Spksh]

Now we can really start cooking! Getting the basic shape accurate is now pretty trivial. I even got uppity and added a sweet angle detail.

Look at that fit!

 

[Spksh]

Of course, we still need to deal with that battery strap (maybe I redesign that next? ). I'm pretty happy with the base now, and I've added some features to match the styling of the AE kit part, and started playing with screw locations.

 

[Spksh]

And this is where we ended up, where I'm happy with the major features.

Look at that sweet alignment!

 

[Spksh]

And our CAD model that will be the base for the details going forward.

We're on a boat!

 

[Spksh]

From here, I added a locator lip around the lid, and a receiver range extender detail.

Here's a side-by-side of the kit rear receiver box and my new front version.

And place in the chassis. Cable sleeving still TBD.

What about a weight comparison? Here's the kit part.

Here's the new one.

This has all been printed in PLA so far. The final version will be ASA, which is less dense. I'm expecting to drop a gram from where we're at now.

So, let's look at the first ASA print!

OK, now what do we do?

 

[Spksh]

Let's talk about supports and print orientation.

In my opinion, print orientation for FDM is the whole ballgame. You're balancing three things: layer adhesion, flat surface aesthetics, and necessary support structures. Ideally, you want to print so that layer adhesion isn't along the axis for force, with flat surfaces parallel to the bed, and with zero supports.

I find that most of the design time for my prints isn't in solving the geometry problem, it's solving for those three trade-offs. And with a complicated part like this, it's mostly about finding a way to print without overhangs, especially curved overhangs.

Just to get to this point, I've been using basic slicer tree supports for the inside of the lid. Not super pretty, but good enough.

But the base has more (and deeper) organic shapes, and more importantly the bottom surface is actually critical to fitment in the chassis. If the 82.5 degree slope is bumpy, it looks like ass in the chassis. So, I hand-built some supports in CAD, turning the bottom face from one flat plane (as far as the slicer is concerned) into a series of very small overhangs.

You can then snap the fins off and you're left with a rough but (most importantly) flat surface.

Overall, a pretty decent result. You can see the stair-step pattern from the overhangs on the bottom edge.

Now this all works for PLA because it's super forgiving to print. Bed adhesion is great on a heated PEI build plate, and overhands are really no problem at all. ASA is not forgiving at all in these exact circumstances. In fact, this is probably the perfect textbook example of the need to design for the filament you're intended to use.

But, we never surrender, right?

 

[WickedFog]

While I was prototyping manually, this little cutie showed up on my local auction site for <25% of retail, with very little use. It's an Einscan SP v1, with phenomenal accuracy and precision. There's a v2 model out now, but really that's just a different USB socket on the back for slightly faster data transfer. So yeah, I bought it.

View attachment 265100

After figuring out some scanning spray (this was AE's Black Album era), this was my first scan:
View attachment 265101

It's hard to articulate how easy this was. Push button, receive point cloud.

And what was really cool to find out is that some of the key measurements I'd taken by hand were dead-on.
View attachment 265102

Jealous man. I've been watching scanner prices. I don't need anything too crazy, so I started playing with the phone apps. They've actually gotten a lot better recently. I remember when they first came out and they were pretty horrible.

I've watched some pretty nice scanners sell for a few hundred. So one of these days I'll be snagging one.

 

[Spksh]

Jealous man. I've been watching scanner prices. I don't need anything too crazy, so I started playing with the phone apps. They've actually gotten a lot better recently. I remember when they first came out and they were pretty horrible.

I've watched some pretty nice scanners sell for a few hundred. So one of these days I'll be snagging one.

Yeah, and the OpenScan rigs for photogrammetry look like they get incredible results now too.

I was about to pull the trigger on a cheap hand-held bottom-end scanner, just to practice, and then this thing showed up. I was the only bidder!

 

[332_RC]

Jealous man. I've been watching scanner prices. I don't need anything too crazy, so I started playing with the phone apps. They've actually gotten a lot better recently. I remember when they first came out and they were pretty horrible.

I've watched some pretty nice scanners sell for a few hundred. So one of these days I'll be snagging one.

Revopoint 3d has the Inspire 2 scanner at $500 that will do indoor/outdoor at 0.05 to 0.1mm accuracy.