| ----- | |
| --- 2591466 | |
| I'm hoping there are one or two materials science austists here that can help me out. What sort of plastic has properties most closely aligned to the following: | |
| -very tough, specifically shock and abrasion resistance | |
| -good (at least decent) dimensional stability | |
| -fairly rigid/stiff, max rigidity while maintaining high impact resistance is preferred | |
| I'm considering UHMWPE, it's probably the toughest plastic out there, but it doesn't have great dimensional stability and is less rigid than i would prefer, although it's not too bad. | |
| Lexan is great right up until it shatters under higher energy impacts.. | |
| Nylon family stuff seems like a solid contender, it's stiffer than UHMWPE, but I wonder how shock/abrasion resistant it is. | |
| I've also been looking into delrin, various glass fiber impregnated stuff, givory, zytel and even micarta. | |
| The application will be the shell for a 3lb shell spinner combat "robot". | |
| Metal shells are far more common with this sort of design, but I was inspired to try something different by picrel, which uses UHMWPE I believe, but I can find almost no information on how well it preforms and holds up to abuse. | |
| Wall thickness would be around 6-8mm, and unlike the picture, the bottom edge will have a steel ring mounted to reduce flexing on impact. | |
| In theory, full height impactors/teeth should help protect the polymer while spinning. | |
| I'm not sure how well various plastics hold fastoners without stripping out. | |
| This will not be 3d printed, instead would either be machined from a solid puck if rigid enough to not twist at the mounting point, or a short section of large dia poly tube with either carbon fiber or 7 series aluminum top if the plastic isn't rigid enough. | |
| Please help me bros, i am out of my depth with so many options. | |
| --- 2591468 | |
| If you're not going to say what you're trying to do with it you're going to get half-baked answers. I'm also 72% sure you're retarded. | |
| --- 2591469 | |
| >>2591466 (OP) | |
| >-fairly rigid/stiff, max rigidity while maintaining high impact resistance is preferred | |
| OP is designing dildos. | |
| --- 2591470 | |
| >>2591468 | |
| he said it's for some gay robot shit | |
| --- 2591471 | |
| >>2591470 | |
| My bad, I got lost in the wall of womanly whining and missed it. Fuck you OP. | |
| --- 2591483 | |
| >>2591468 | |
| >>2591470 | |
| >>2591471 | |
| I bet when you guys sit down, you go YEEERRUUYYAAHHHhhhhhh. You're right though it was written like a needy pussy. | |
| --- 2591508 | |
| >>2591466 (OP) | |
| peek or glass / carbon filled nylon | |
| hope youre loaded op | |
| also | |
| >fasteners | |
| Look into threaded inserts, be it heat-set or stuff like helicoils | |
| --- 2591620 | |
| >>2591466 (OP) | |
| IN THE RED SQUARE... | |
| --- 2591625 | |
| >>2591466 (OP) | |
| You're gonna want some of these | |
| https://en.wikipedia.org/wiki/Belleville_washer | |
| --- 2591663 | |
| >>2591508 | |
| Noted and will do, thank you brother anon. | |
| >>2591625 | |
| I had no idea. | |
| --- 2591683 | |
| >>2591466 (OP) | |
| DELRIN | |
| E | |
| L | |
| R | |
| I | |
| N | |
| --- 2591690 | |
| >>2591466 (OP) | |
| Can’t say I understand the design but here’s some thoughts. | |
| Both Teflon and uhmpwe come to mind because they’re used in applications where they see a lot of impact abuse (trucks, plane cargo bays, warehouse logistics). | |
| > Wall thickness would be around 6-8mm | |
| That’s pretty thin if there’s no structural support on the inside. Wondering why you want it to be so rigid instead of a hard rubber though | |
| > I'm not sure how well various plastics hold fastoners without stripping out. | |
| Usually not amazing but there are many types of threaded inserts available depending on application. Some are press/form fit, others glued or thermally bonded depending on application | |
| --- 2591724 | |
| https://www.riobotz.com/riobotz-combot-tutorial | |
| Lots of information put together by some battlebots champions. | |
| Also friendly reminder that a torque wrench is to make sure fasteners aren't on too tight. | |
| People tend to tighten things up too much, one big hit and the bolts snap. | |
| --- 2593283 | |
| >>2591466 (OP) | |
| >-very tough, specifically shock and abrasion resistance | |
| >-good (at least decent) dimensional stability | |
| >-fairly rigid/stiff, max rigidity while maintaining high impact resistance is preferred | |
| In general, impact resistance is a direct tradeoff with rigidity. People love steel because it's an exception. Amongst plastics, CF-filled nylon is kind-of an exception, though nylon has its own weird drawbacks. For 'cheap/easy', racemic PLA is surprisingly good, and nearly as stiff by itself as CF nylon. | |
| >I'm considering UHMWPE, | |
| I can think of few things less dimensionally stable or stiff than UHMWPE. OTOH, if that's almost good enough for you, then your requirements aren't as strict as you think. | |
| >Lexan is great right up until it shatters under higher energy impacts. | |
| Yes, and it crazes/accumulates stress damage. | |
| >Nylon family stuff seems like a solid contender | |
| *very* shock/abrasion resistant. God-tier. OTOH, static stress will crack it over long periods, and it absorbs moisture (and swells) like a sponge. So.... not as dimensionally stable as many things, but it's probably not an issue for your use. | |
| >I've also been looking into delrin, various glass fiber impregnated stuff, givory, zytel and even micarta. | |
| Pricey. | |
| >The application will be the shell for a 3lb shell spinner combat "robot". | |
| In this application, *nothing* will perform better than steel. Even just mild steel. | |
| >In theory, full height impactors/teeth should help protect the polymer while spinning. | |
| >I'm not sure how well various plastics hold fastoners without stripping out. | |
| They hold fasteners well. They may not stand up to repeated insertion/removal, and very tight / stressed connections will cause most (not all) polymers to creep and loosen over time to a degree. But--- I wouldn't worry about the creep on your time scale. | |
| >carbon fiber or 7 series aluminum top if the plastic isn't rigid enough. | |
| CF is stiff. Most Al alloys you'd use really aren't. | |
| --- 2593284 | |
| >>2593283 | |
| Forgot to mention-- | |
| High stiffness urethane/polyurethane may be interesting. Very wear/shock resistant. *and* you can cast it easily for cheap. | |
| --- 2593505 | |
| I would say POM. | |
| There's a reason machine workshops love working with it. | |
| --- 2593739 | |
| Just melt down a bunch of milk jugs and cast it out of that. | |
| --- 2593752 | |
| >>2591466 (OP) | |
| The shell acts as a flywheel so metal is better and you have no reason to want plastic stop being retarded. More weight towards the rim is better than a thicc center. | |
| A healthy spindle (not a motor shaft) will avoid damage when smashing shit. Consider how front wheel drive spindles are built and copy that. | |
| Just machine the spinner on a large manual lathe or even turn down a car flywheel to suit. Art doesn't matter. Winning matters. | |
| --- 2594439 | |
| why don't we have a combat robotics general? | |
| --- 2594443 | |
| >>2593505 | |
| Based POM, King of plastics | |
| --- 2594447 | |
| >>2591466 (OP) | |
| >I'm not sure how well various plastics hold fastoners without stripping out. | |
| Use Chicago screws. | |
| --- 2594487 | |
| >>2591683 | |
| >burns, releasing poisonous formaldehyde gas | |
| learned this the hard way. dont use fucking delrin | |
| t. lung cancer | |
| --- 2595992 | |
| >>2593752 | |
| I bet a dead axel would do him better | |
| --- 2596015 | |
| >>2594487 | |
| >dont use fucking delrin | |
| More like don't burn delrin. The little bit of formaldehyde smell you get while machining it is just part of its charm. | |
| --- 2596805 | |
| >>2596015 | |
| Machines sweetly tho and ventilation is an option. | |
| --- 2596985 | |
| >>2591690 | |
| >That’s pretty thin if there’s no structural support on the inside. Wondering why you want it to be so rigid instead of a hard rubber though | |
| The bottom edge will be reenforced by a waterjet steel ring. I'm also throwing around the idea of using a short section of large diameter poly tube for the sidewall so I could use a stiffer material like 6061 or cf for the top | |
| If it's too soft/flexible, there will be twisting and out of plane forces at the mounting point upon impact. | |
| Thank you, I will read into Teflon. | |
| >>2591724 | |
| I have the robots tutorial, its a fantastic resource. | |
| Thanks for the reminder anon. | |
| >>2593283 | |
| Yes, for sure, that's the difficulty of finding one that's just right. | |
| I heard about Nylons affinity for water, will it slowly absorb humidity from the air? | |
| I appreciate the info. | |
| >>2593505 | |
| Will look into it, thanks. | |
| >>2593752 | |
| Heat treated steel shells are generally fine, grade 5 ti is probably the best metal, but 6061t6 Al can work as well. | |
| I want to try something different, and believe this could work passably well. Its also nice to keep machining and material cost down. | |
| I admire your klingon brutalist mindset, QA PLAH! | |
| >>2594447 | |
| Ive heard this before, I know they also make screws specificly for plastics. Will look into it, thanks. | |
| >>2594487 | |
| Thanks for the heads up, praying for you man. | |
| --- 2597269 | |
| >>2591466 (OP) | |
| Delrin. | |
| --- 2597272 | |
| >>2591466 (OP) | |
| uhmw is brittle. a softer plastic would be a better option it will be able to absorb much harder blows. built up ABS with kevlar mesh would be extremely strong | |
| --- 2597283 | |
| >>2596985 | |
| >Its also nice to keep machining and material cost down. | |
| That's a key reason for steel along with simplicity. Suitable "drops"/cut offs can be found at machine shops left over from jobs (the customer already paid for it) and are often for sale. Friday is a good time to visit. | |
| Car and truck flywheels are dirt cheap from salvage yards and are already drilled and bored for a central hub or shaft of your choice. You can turn them down and if you want to make a cup you can use sections of heavy wall pipe or cut up more flywheels. No need to buy the heavy parts new. | |
| Battlebots are supposed to be brutal. You just want to add production complexity for its own sake not actual performance which is fine but never lie to yourself. | |
| --- 2597326 | |
| >>2597272 | |
| >uhmw is brittle | |
| I made skateboard rails out of it. It is one of the few things tough enough to survive. What was your use case that destroyed it? | |
| --- 2597330 | |
| OP be sure to post here when you're on TV. | |
| Poor Chris Rose, by the way ... he used to co-host his own show on MLB Network, now he's giving the "play by play" on Beyblades battles. | |
| --- 2597548 | |
| >>2591471 | |
| There's no womanly whinibg in there. | |
| He simply lays out his considerations while you try to cover up your inability to read. | |
| --- 2598576 | |
| not a materials expert, but isn't "shock resistant" and "rigid" at odds with one-another? usually the more hard something is, the more brittle it is, you get better impact resistance if you use something that has a bit of flex | |
| i design mining equipment, and for material impact surfaces we use sheets of HDPE, now that's not to say that's the best for your case, weight isn't a concern for me, but cost is, so i don't use fancy materials, but i don't use a stiffer material because i want it to wear away slowly, and not just crack and disintegrate | |
| --- 2598594 | |
| >>2591483 | |
| kek | |
| --- 2598810 | |
| >>2598576 | |
| Well partially, but absolute strength also plays a part. A sheet of carbon fibre reinforced plastic is both more shock resistant and stiffer than a sheet of glass, but only because CFRP is so much stronger. | |
| --- 2599667 | |
| >>2597272 | |
| --- 2599719 | |
| >>2591620 | |
| fucking lol | |
| --- 2600132 | |
| >>2591466 (OP) | |
| Polycarbonate I'm using is meant for an 8mm thick panel. Incredibly tough and scratch resistant once coated. Jump on the thinner PC parts like a trampoline. Met up with a sales rep for Triton material, think Nalgene uses that now, seems pretty great and no Bisephenol A? | |
| --- 2600135 | |
| >>2598576 | |
| Milk jug PCR. The melt on that shit is like .3 compared to normal 5 or 8 melt consumer hdpe. Cheap as dirt too. | |
| --- 2600158 | |
| >>2600132 | |
| Is that the same as lexan? | |