Team Antiquarian - Work in Progress

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MySolderIsOlder
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Team Antiquarian - Work in Progress

Post by MySolderIsOlder »

Decided it was time to retire PolycarbonAnt and replace him with a more easily maintained and less scruffy version of the same basic 4wd parallelogram-sectioned / invertible pusher design. Might be a bit old-fashioned but being a lousy driver, I appreciate not having to think too hard when an ant's upside down!

So, the idea is to make something that can evolve over time to become as close to indestructible as possible; each time it gets into a fight with a spinner and a weakness is exposed, I'll try to refactor that weakness out. Hence the name (actually borrowed from a 'sculpture' by the surrealist artist Man Ray): "An Object to be Destroyed".

Initial plan was to 3d print a body frame and screw on polycarbonate plates top & bottom . Having played around with it in Fusion and printed some tests however, I realised this introduced too many weak-points, as well as making it harder to prepare a stock of spare parts. So eventually I decided to go fully printed - but to try using one of the tougher nylon+CF filaments for all the body-work.
Given the price of exotic filaments, I want to get the design as close to finished as possible first. To that end, I'm using some so-called "premium" but actually "really not very good" blue ABS that I bought dirt cheap from the HobbyKing bargain bin some time ago. Although I wouldn't dream of using it for a real robot, it's proving useful for prototyping. Here's the latest prototype for Object 2B Destroyed, shown with only one of the wheel protectors fitted (if weight allows, I'll make that a full-length side protector, so it's easy to replace after a spinner catches us broadside):

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Wheel diameter is 21mm and the body is about 13mm thich, so the whole thing sits pretty close to the ground. The row of holes at the ends are for bolting on a 1mm thick titanium sheet wedge and I'm planning to sandwich some 2mm thick neoprene foam between that and the plastic, to help absorb impact. Might even experiment with little wedgelets at one end for optimum acetate-busting - certainly got enough room to spare on the length. One big improvement already on most of my previous designs, is a separate battery compartment hatch, which means only 4 screws to undo to access the LiPO!

Next step was to print it up in something tougher. Options for Nylon + Carbon Fibre fil are currently a bit limited (without shipping it over from the States) but in the end I settled on something called "PA12 + CF5" from Fiberlogy, bought from 3d-Jake. Unfortunately. although the filament seems pretty good, the spool it came on is a nightmare; much too fat to fit in the air-tight spool holder that came with my Up 2 Mini printer. One thing one hears over and over again about nylon filaments is that they suck moisture out of the air like nobody's business and instantly become unusable... so the first job was to build a new spool container. Here's the result:
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It's just a "Lock & Lock" plastic food box, to which I've added a simple 3-d printed spool holder and a nozzle for the filament & bowden tube. Though I say so myself, it's actually a great improvement on the Tiertime original (that thing on the left) - takes a full sized 1KG spool, it's even more air-tight and just as easy to load. Did a couple of simple test prints earlier, using the default ABS settings (270c hot end, 90c bed) and seems fine so far. Separating the print from the top support layer was a faff but absolutely no issues with warping or layer separation. First attempt at the full body is now printing - so in a few hours I should know whether Object 2B Destroyed is going to be a thing!
Last edited by MySolderIsOlder on Mon Mar 29, 2021 10:33 am, edited 2 times in total.
Stuart (Anthony's dad)
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Re: Work in Progress preview: An(t) Object to be Destroyed

Post by MySolderIsOlder »

Arrrrrgggggh!!!
Ruined print. Major Y-axis offset about 4mm from the top layer. 7 hours printing time and 5 quids worth of filament wasted. :evil:

Oh well, try again tomorrow. On the plus side i got to practice removing from the support layer. All OK except that big flat expanse in the base. Even with the 'Easy peel' settings, that was welded on to the support. Might try putting a slightly rippled surface on the bottom to see if that helps...
Still one heck of a learning curve.
Stuart (Anthony's dad)
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MarkR
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Re: Work in Progress preview: An(t) Object to be Destroyed

Post by MarkR »

Good to see that you're still building!

I have noticed lots of fancy 3d filaments kicking around, but now I've just picked up some bargain-bin Nylon and it seems pretty good. At least, we'll try with the plain Nylon (Nylon 645) and see if that holds up better than the PLA which I used before (and two robots got trashed back in November, which seems ages ago) and didn't do too well against "Test Robot Please Ignore" or "Cosmic Burgervan"
Robots: Betsie - RaspberryPi controlled flipper bot with gyro stablisation - too clever for her own good?
Stacie - tidy flipper; 4wd driven by hair bands
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Re: Work in Progress preview: An(t) Object to be Destroyed

Post by MarkR »

Nice chamfer around the switch cut-out, makes it harder to get accidentally swiched off. Nice detail.
Robots: Betsie - RaspberryPi controlled flipper bot with gyro stablisation - too clever for her own good?
Stacie - tidy flipper; 4wd driven by hair bands
MySolderIsOlder
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Re: Work in Progress preview: An(t) Object to be Destroyed

Post by MySolderIsOlder »

Second-time lucky - reduced the printing speed and this time it worked fine.
Here it is with the N10 motors slotted into place.
Image

Next step is to print the two top-plates, then I'll sort out some electronics.

Pleasantly surprised at how well the CF Nylon takes a thread. Just as a test I tapped a couple of the screw holes with an M2 thread and it holds really well with the little M2 button heads I used on all my polycarbonate constructions. WIll have to do some stress tests before I decide between that option or self-tappers.
Stuart (Anthony's dad)
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Re: Work in Progress preview: An(t) Object to be Destroyed

Post by MySolderIsOlder »

All wired up and ready to go!

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Battery compartment is a little tighter than I'd like, but thanks to my practice of snipping off the discharge leads and only using the balance plug, it will just fit.

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Weight-wise, everything is fine - 111g with everything except the end wedge armour.

Talking of which, here's one end finished. IT's 1mm thick (allegedly) Gr5 Titanium, held on with M2 countersunk machine screws and nuts. There's a 2mm thick layer of neoprene rubber sandwiched between this and the body, to help absorb any impacts.
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Just done one end so far (need to order some more machine screws) but it only added 15g - so even when the other end is done I've got another 10g left to play with. Will probably use that to add some more side protection and maybe a thicker top plate, especially over the lipo.
Stuart (Anthony's dad)
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Re: Work in Progress preview: An(t) Object to be Destroyed

Post by MarkR »

Maybe a thin piece of Ti over the lipo, to make things a bit trickier for Shakey if you get drawn against "It's only a drill" ... ?

Mark
Robots: Betsie - RaspberryPi controlled flipper bot with gyro stablisation - too clever for her own good?
Stacie - tidy flipper; 4wd driven by hair bands
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Re: Work in Progress preview: An(t) Object to be Destroyed

Post by MySolderIsOlder »

You read my mind Mark!
Stuart (Anthony's dad)
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Re: Work in Progress preview: The Undertaker

Post by MySolderIsOlder »

Well, it's all been a bit quiet of late so I thought I'd do a Work in Progress update... Been having a nightmare for some time now with my previously oh-so-reliable Up Mini 2 Printer, which kept throwing the X-axis off by around 1cm randomly mid-way through big prints. Was convinced it was a slipping or sticking stepper motor or belt but despite repeated forensic examination and cleaning, I couldn't see a problem, though it got to the point where just about every print was bad. In desperation I upgraded to the latest V3.0 beta version of the Tiertime 'Up Studio' s/w - and magically the problem disappeared. I suspect it was accelerating too fast or something and getting dizzy. Just goes to show the importance of eliminating all variables when fault finding!

So anyway, now that things are back in action printer-wise, I can finally start playing with the assortment of 3rd-party weapons I treated myself to a while back. Even though it still feels a little like cheating, I just couldn't face any more hours of cutting and filing titanium blades. My finest Bahco's still haven't recovered from filing Recycler's last lot of teeth. Will probably get around to ordering my own watercut blades soon - just need to figure out where from. In the mean time, time to see what the ready-mades are like. First off the block is a 60mm Hardox 'Brawler' disk from Drizzlebots. Having given up on flails for now, I salvaged the electronics and motors off "Try Again Flail Again" and repurposed them into my first attempt at a horizontal/undercut spinner.

It's not quite finished yet - still got a few tweaks to do - but here's the first working draft of "The Undertaker", who will hopefully be joining Anthony's team, alongside a re-designed Recycler, ready for AWS62.
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First problem I had planning this new design was the lack of small 3s LiPOs. I do still have a pair of the 180mah Nanotechs, but those are reserved for 'Other Way Up'. The next size up from Turnigy are way too big and heavy so with some trepidation I took a chance on some random imports on ebay. They're 'Guonang' (I think) 3S 300mah packs, in a long thin rectangle package, which imposes certain design constraints. So that is why The Undertaker has such large wheels - I decided to fit the LiPO widthways underneath the motor cage. If nothing else I'm hoping it will help with weight balance / stability, even if the vulnerability of those cartwheels may necessitate the 'Sontaran defence' (always face the enemy)
On the plus side, these LiPOs are pretty light. With the discharge leads carefully snipped off (I use the balance plug for power as well as charging), I got the weight down to just under 24g, which is not much worse than the old Nanotechs.
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Filament is Fiberlogy's PA12-CF05 Nylon/Carbon mix, which is one of my current favourites, though I think it needs a visit to the oven before I reprint this body shell.

Total weight is currently 2g over but that's mainly because I made the tyres far too deep. Have now reprinted my tyre mould with more sensible dimensions and will cast some new ones over the weekend. First proper test spin will have to wait until I've built a new test box - the old one having been cannibalised for other jobs.

Other projects still on the drawing board (but some of which will hopefully be ready for AWS62) include an overhead saw bot (they seem to be this season's hot fashion), a vert called "The Rotovator" based around a pair of OwObotics AR400 46mm Destructor disks mounted in parallel, a low-slung 4wd flipper (provisionally referred to as "I can't believe it wasn't inspired by I can't believe it's not Stanley") and, most importantly, a much nastier 'mark 4' version of Recycler.

Hope everyone's keeping safe and look forward to catching up around an arena later in the year!
Stuart (Anthony's dad)
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Re: Work in Progress

Post by MySolderIsOlder »

Like I said, the tyres were too heavy, so I tweaked the core and sides of my tyre mould design and reprinted those bits. Here is the result, with the RTV silicone tube ready to come out of the mould
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Cutting a tube of silicone into calamari style rings by hand is a non-starter, so I pop the core onto a suitable bit and place in a pillar drill, then cut the tyres using my super-high tech precision cutting tool (a Stanley knife blade and a stack of plywood offcuts)
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here's the result - a new batch of tyres ready to go.:
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New tyres on - here's the belly of the beast:
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And as I hoped, the slimmer-profiled tyres have knocked about 2.5g off, bringing The Undertaker just within safe limits.
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Did a quick spin-up test, just to confirm everything was working and it looks very promising. Almost no vibration or drift, which is what was worrying me about an undercut design where one of the points of contact with the arena is the weapon itself. Looks like the simple nose-cone did the trick.
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Will do proper tests (including the obligatory tin-can abuse) and post vids once the Polycarb for a new test arena arrives.
Stuart (Anthony's dad)
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