[BW] GR-01 Build Diary

[GlenR]

The 3d printed ones were almost universally ruined after a fight with a spinner, I can't recall any being made from it in the last event we had, but then again its an enclosed arena so the robots don't shoot out after the first hit :P

Thats a sweet design too, Looking foward to seeing it running. The forks are especially cool!

[typhoon_driver]

Taulman may be ok but you need to watch what the orientation of the weak bonded layers is in relation to the most likely stress.

[Giles]

Thanks for the replies all! My shipment of filaments arrived today, so I'll be testing out the feasibility of it all over the next few days. In my experience with 3D printing, this stuff should be up to the job, but we'll see!

I just realised that since swapping the side panels from being aluminium to HDPE, I can no longer get them laser cut. Does anybody know of a good CNC service that can work with HDPE? Or perhaps another option?

[shakesc]

HDPE cuts nicely with standard woodworking tools - just have a steady hand
I use either a chop saw or a circular saw and fence

[RogueTwoRobots]

A jigsaw with a woodcutting blade works great for HDPE, especially in the smaller thicknesses. It will go through thinner stuff like a hot knife through butter though, which makes it quite easy to end up with wavy lines as opposed to nice clean straight ones, so if you do opt for that method, a steady hand as Chris mentioned, or even just taking it slowly, will prevent that.

[Giles]

Have just been speaking to Ellis about this and it definitely seems cutting it myself is the best option. I've got a table scroll saw which is great for cutting thin materials precisely (if a little slow). Going to print out some templates and simply cut around them!

Good to know that wood working blades work well!

[Giles]

This Taulman 910 is strong stuff! Just printed out a few bits to test.

The first thing I printed was a 20 x 20 x 5 box with 20 percent infill. This was extremely light and only had 0.8mm wall thickness. Despite its flimsy looks, it was very strong. The part couldn't be bent or squashed by hand, so I moved to the vice. The vice was able to squash the part with a lot of force, but upon removing the part, it just sprang back into (almost) its original strength.
After giving it a good squashing, I decided to test its impact resistance. I was expecting one hit with a hammer to destroy it, given the low infill of the part - this was not the case! I was smashing the heck out of that thing for multiple hits with the hammer until it eventually gave in and the top layers begun to give way.

I then printed out a longer 5mm thick strip with 100% infill. This was quite flexible, definitely don't want to use this stuff for a frame! But still very strong. The vice did nothing to it along the same axis as the print was made and the hammer didn't do anything, the part just flung itself around the garage. It cuts reasonably easy with a pair of wire cutters, but requires a lot more force than a beetle could deliver.

I also printed a part with some test holes, keeps its dimensions very well, with a 12mm hole fitting a 12mm bearing perfectly with a tight grip.

Impressed with this stuff for sure, I think it'll fit the bill nicely! I'll try to post a stress test video once I have some wheels printed out.

[Max]

HDPE does cut very nicely with a waterjet so that could be an option of the hand tools don't work out, from quotes I have got it can be relatively affordable

[Giles]

Printed out some idler wheels. The filament wasn't quite flowing correctly at the start, so the bottoms of them are a bit messy. Will reprint these once I've got more parts to work with. Bearings fit nicely though and they roll great Are the flanges required? Or would the belt run on them ok without?

[Ellis]

If it all tracks right and the idler is slightly wider than belt width + the maximum side-side movement of the belt then it shouldn't need them.

Looking good.

[Giles]

Boredom lead to me doing some renders... I'll get back to building at the weekend!

Drafts:



Close up:



Really really bored:

[overkill]

Is that the new Mars rover? Its looking great but I think you should either use longer nutstrips or split the existing lengths in two and move them closer to the wheels. Also, are you planning to use cap head screws as shown or countersunk screws on the outside panels? Raised screw heads are magnets for other spinners.

[suvv]

man i wish i was that good at 3d modeling

[Giles]

Thanks guys. Going to add more support to the front area soon. Probably a mixture of nutstrips and 3D printed supports again.

Here's the wedge design. They are flush with the frame when not in use and will slide along the ground when they are.

[Niels - Team K.a.L.M.]

2 problems with the prongs that I can see.

1: The angle of the upper prong will prevent movement of the lower prong, locking them up. Increasing the length will help here.
2: They feel thin, and will easily be swept sideways and bent. Bring spares for they will work against many a machine.