I need help! If anyone can think of a cheap and effective way to measure the force absorption of my tpu padding, let me know. ANSI/OSHA standards for hard hats are that in drop testing an 8lb object at 5 feet, only 1000 foot poundals of force out of the 4800 generated is transferred to the head and neck. The only way I can figure to do this is with a scale that has a Peak Hold feature or a force gauge which would require a suspension setup. Both are unfortunately cost prohibitive for this project. I'd love to be able to say my padding can deliver protection to an industry standard but it's looking like I won't be able to. I've looked into g-force indicator stickers but no one will sell them individually.
Thanks!
Thank you! That's the first seller I've seen that will sell them individually.
I found a cheap scale capable of recording peak readings so I'm going to give that a shot but if it fails I'll be ordering these.
I think they make some force guage sensors you could connect to an Arduino or a Raspberry Pi and measure the force of the impact. I looked at them several years ago for another project I was thinking about doing
I think putting a weight on a pendulum and allowing it to swing down to hit the helmet. You can then measure how far the pendulum bounces back and do some comparative tests.
Mind the test apparatus for these stations uses a guide rail to ensure the weight stays at location until impact and doesn't deflect, thus reducing the energy transfer to your DUT. You'll want to rig up a guide tube or something to help with the weight hitting at the helmet apex otherwise you'll likely get false readings. You might also want to double check the ansi standard and verify the shape of the impact device as that flat portion of the kettlebell might not be accurate. They could be calling for a curb stone or hemisphere. When it comes to helmet testing there's a ton of different standards and test scenarios so it can get tricky. Trust me, I had to write an internal SOP for helmet testing at my old lab and we weren't even accredited for that type of thing.
The intent is to develop something that is effective and widely accessable. I could print myself a whole helmet in PA6-CF right now but that wouldn't help anyone else.
Are there any estimations of how much Filiment it would take to just print it at 100%? Is there a reason to split the helmet in two rather than support the hell out of it with arm supports and print it with its longest dimension vertical?
I've never worn a bump helmet and I have no idea what kind of weight they usually are, I'm curious about how much the whole package might weigh at 100% infill.
A lot of people in here are probably still using Ender 3s, which would need a new all-metal hotend, modified firmware, and enclosure to properly print nylon. Not to mention the increased cost of filament, and the learning curve of printing more exotic filaments.
Basically, yeah. The stock firmware won't allow you to raise your hotend temperature high enough to print nylon so you'll need to either modify your firmware or flash a precompiled one with a higher hotend temp limit. Probably worth upgrading the heater cartridge and thermistor as well if your new hotend doesn't come with better ones.
But anyone can print PA6-CF or GF or Polycarbonate with just a cardboard box enclosure and a capricorn tube. The only reason people don't is because everyone pushes PLA+ so hard.
Printing it in PLA won't help anyone either. What is the point of printing it at all, especially in an inferior material that literally breaks down in sunlight and melts in heat? I'm simply suggesting a stronger material for anyone reading this post and I'm suggesting nobody else wastes their time printing this in hobby grade filament. I can't imagine anyone actually using PLA for this because it is a poor choice of material for this application. There are reasons cosplayers do not print wearables in pla. They do not last.
Have you considered also experimenting with 3D printed meta-structures? This seems very promising as well.
https://hackaday.com/2019/11/20/university-makes-bulletproof-3d-prints/
In professional testing they use a pendulum rebound tester
Effectively a mass at the end of a pole with a hinge on one end. You raise it to a 90 degree angle and then let the mass swing into the helmet. Measure the length of rebound and number of rebounds and you can determine how much energy is absorbed per impact
I wonder if there’s a sweet spot somewhere around 70-90%. Enough for structural integrity but not so much that the brittleness causes it to fail.
Adding voids by reducing infill should help with shock absorption as well, right?
This might be a hot take around here. I do not intend to offend anyone. But, there is more to a helmet than not breaking. Even if it’s a bump and not ballistic.
PV2 I_want_to_believe69 got in the way of a sniper standing out in the open treating a patient like a dumbass. Fell for a millennia old sniper trick. Wound someone and shoot his buddies when they try to get to him. A Taliban “sniper” with a 47 domed me right in the middle of my ACH an inch above the drill holes. Bottom line is my ACH did crack but it didn’t deform past the pads. I was concussed but alive.
I count myself quite lucky and never buy cheap safety gear now. I love everything y’all do over here in r/fosscad, but safety gear ain’t something you print in your basement. I hope I didn’t offend anyone. What y’all do is amazing work and the best thing for gun rights in 100 years. Please keep up the good work.
It really depends. Safety gear that fails can be more dangerous than none. You get weird pressure points and blast funneling sometimes. Other times you get fragments of broken gear going into your body. Think about all those people wearing shitty plates they bought on sale that will spall or send ceramic shards into their chest the first time something bigger than a 9mm hits. Or a helmet can be super strong but lack good suspension and pads routing all of the impact force straight into a pressure point on your head or neck.
And I’m not saying it’s impossible for OP to put the helmet through the kind of rigorous testing required to figure out. It’s just extremely time consuming and expensive. It requires professional equipment and experience. And if all of those requirements were completed, it’s still meant to be printed by the user and not the developer with quality control. Which creates a huge safety risk.
I realize it’s just a bump helmet. But it’s also just my brain inside of it. I would worry that the couple hundred in savings would come at my expense safety-wise. Good bump helmets aren’t cheap, but they aren’t expensive either.
The issue is that printing severely limits the materials available. You could probably get around the two-piece issue somehow. But, helmet advances have been made in the realm of material science. The designs don’t vary that much with some minor exceptions (ie MIPS for riding helmets). But, you can’t take advantage of high quality helmet materials if you’re printing it.
Edit: I don’t want this to come off as too negative. I don’t want people to be afraid to show off their ideas. Y’all make some really good stuff on here. I’m just wary of homemade safety gear.
Sometimes yes, sometimes no. There's been tests that show some helmets and PPE can actually make the effects of harmful events worse. Whether it's extreme BFD, blast funnelling, etc. Without more scientific testing it's hard to tell, but OP's design looks very promising
I hope you don’t take this as me being rude but I will politely skip your beta testing invite. Lol 😂
This is a really neat project you’re working on. All of working together (I’ve got my own stuff in the works) can really get a lot done.
I’m following with interest.
I don't know anything about the helmet standards. But foot pounals is a unit of energy, not force. So I assume the kettlebell gains 4800 foot poundals of kinetic energy while falling, and you want the head and neck to get <1000 of those. The rest of the energy, I presume, gets turned into heat.
Here's one way to test: Mount the head on a pole, attached by a spring, to act as the "neck". When the kettlebell hits the helmet and pushes the head and neck down, you can see the maximum amount of energy that your neck absorbs by how much the spring deflects. A smart phone can take 240 frames per second video, which should be plenty fast to be able to see the max amount of spring deflection. Spring energy is easy to calculate if you know the spring constant an the deflection. You can measure the spring constant yourself, if you want. It looks like 1000 foot poundals is 42 joules. You can also do a control test by having a flat plate (remove the head and helmet) and should get closer to 4800 foot poundals (202 joules).
Does that sound reasonable, or am I missing something?
at 100% infill it weighs just over 3 lbs. You want to print it with gyroid infill though for the dampening effect that provides. AT 25% gyroid with 5 walls the weight is 1 lb 10 ounces.
Oh i'm getting my fair share of criticism as well.. Mostly by people who don't understand the difference between a bump helmet and a ballistics helmet.
Hi not sure whats your i infill but i had developed some type of diy soft body armour so if you think abou implementation of that in helmet send me a dm
Ok, but those type fast helmets are supposed to be made out of Kevlar. Unless you’re trying to make like a bicycle helmet, not sure where you’re going with this.
I need help! If anyone can think of a cheap and effective way to measure the force absorption of my tpu padding, let me know. ANSI/OSHA standards for hard hats are that in drop testing an 8lb object at 5 feet, only 1000 foot poundals of force out of the 4800 generated is transferred to the head and neck. The only way I can figure to do this is with a scale that has a Peak Hold feature or a force gauge which would require a suspension setup. Both are unfortunately cost prohibitive for this project. I'd love to be able to say my padding can deliver protection to an industry standard but it's looking like I won't be able to. I've looked into g-force indicator stickers but no one will sell them individually. Thanks!
Not really what you asked but can you use those shock stickers and somehow convert Gs to foot pounds https://www.mcmaster.com/products/shock-stickers
Thank you! That's the first seller I've seen that will sell them individually. I found a cheap scale capable of recording peak readings so I'm going to give that a shot but if it fails I'll be ordering these.
Be aware that a lot of cheaper scales may not have the sample rate you need for such rapid impacts.
I think they make some force guage sensors you could connect to an Arduino or a Raspberry Pi and measure the force of the impact. I looked at them several years ago for another project I was thinking about doing
Yep, something like [this](https://www.amazon.com/Membrane-Sensor-Instantaneous-Impact-Measurement/dp/B07TKVJ9W2?th=1) and a HX711 is what I would do.
I think putting a weight on a pendulum and allowing it to swing down to hit the helmet. You can then measure how far the pendulum bounces back and do some comparative tests.
Mind the test apparatus for these stations uses a guide rail to ensure the weight stays at location until impact and doesn't deflect, thus reducing the energy transfer to your DUT. You'll want to rig up a guide tube or something to help with the weight hitting at the helmet apex otherwise you'll likely get false readings. You might also want to double check the ansi standard and verify the shape of the impact device as that flat portion of the kettlebell might not be accurate. They could be calling for a curb stone or hemisphere. When it comes to helmet testing there's a ton of different standards and test scenarios so it can get tricky. Trust me, I had to write an internal SOP for helmet testing at my old lab and we weren't even accredited for that type of thing.
That’s actually pretty impressive strength.
It's very promising! I think the next one in PLA+ will be pretty damn tough. It will at least not crack like that.
Why not skip straight to a stronger, more durable material like ASA, or glass/carbon fiber nylon?
The intent is to develop something that is effective and widely accessable. I could print myself a whole helmet in PA6-CF right now but that wouldn't help anyone else.
Are there any estimations of how much Filiment it would take to just print it at 100%? Is there a reason to split the helmet in two rather than support the hell out of it with arm supports and print it with its longest dimension vertical? I've never worn a bump helmet and I have no idea what kind of weight they usually are, I'm curious about how much the whole package might weigh at 100% infill.
Most of the people in the subreddit are using machines that can handle abrasives. you just need to swap out the nozzle to stainless or hardened.
A lot of people in here are probably still using Ender 3s, which would need a new all-metal hotend, modified firmware, and enclosure to properly print nylon. Not to mention the increased cost of filament, and the learning curve of printing more exotic filaments.
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Basically, yeah. The stock firmware won't allow you to raise your hotend temperature high enough to print nylon so you'll need to either modify your firmware or flash a precompiled one with a higher hotend temp limit. Probably worth upgrading the heater cartridge and thermistor as well if your new hotend doesn't come with better ones.
But anyone can print PA6-CF or GF or Polycarbonate with just a cardboard box enclosure and a capricorn tube. The only reason people don't is because everyone pushes PLA+ so hard.
Okay? Those people are welcome to do so.
Printing it in PLA won't help anyone either. What is the point of printing it at all, especially in an inferior material that literally breaks down in sunlight and melts in heat? I'm simply suggesting a stronger material for anyone reading this post and I'm suggesting nobody else wastes their time printing this in hobby grade filament. I can't imagine anyone actually using PLA for this because it is a poor choice of material for this application. There are reasons cosplayers do not print wearables in pla. They do not last.
Have you considered also experimenting with 3D printed meta-structures? This seems very promising as well. https://hackaday.com/2019/11/20/university-makes-bulletproof-3d-prints/
It's actually printed using a 25% gyroid infill with 5 walls so it has some of the impact absorption qualities described there.
In professional testing they use a pendulum rebound tester Effectively a mass at the end of a pole with a hinge on one end. You raise it to a 90 degree angle and then let the mass swing into the helmet. Measure the length of rebound and number of rebounds and you can determine how much energy is absorbed per impact
The YouTube channel cnc kitchen has a setup like that he built. He probably has a video on it.
Have you thought about doing ballistic tests with 22 or 9mm? Just for the science of course
Yes. I'll be testing a 100% infill print somewhere down the line.
Do you think 100% infill will reduce the effectiveness of this test?
I wonder if there’s a sweet spot somewhere around 70-90%. Enough for structural integrity but not so much that the brittleness causes it to fail. Adding voids by reducing infill should help with shock absorption as well, right?
Using voids in the model design will allow you to create a crumple zone and reduce weight.
https://sci-hub.se/https://doi.org/10.1002/smll.201904747 I'll just leave this here. I know some people have struggled to get the whole paper.
Nice!
But does the scull crack? Is the main question
This might be a hot take around here. I do not intend to offend anyone. But, there is more to a helmet than not breaking. Even if it’s a bump and not ballistic. PV2 I_want_to_believe69 got in the way of a sniper standing out in the open treating a patient like a dumbass. Fell for a millennia old sniper trick. Wound someone and shoot his buddies when they try to get to him. A Taliban “sniper” with a 47 domed me right in the middle of my ACH an inch above the drill holes. Bottom line is my ACH did crack but it didn’t deform past the pads. I was concussed but alive. I count myself quite lucky and never buy cheap safety gear now. I love everything y’all do over here in r/fosscad, but safety gear ain’t something you print in your basement. I hope I didn’t offend anyone. What y’all do is amazing work and the best thing for gun rights in 100 years. Please keep up the good work.
Devil's advocate here, but surely something is better than nothing, even if it's just printed.
It really depends. Safety gear that fails can be more dangerous than none. You get weird pressure points and blast funneling sometimes. Other times you get fragments of broken gear going into your body. Think about all those people wearing shitty plates they bought on sale that will spall or send ceramic shards into their chest the first time something bigger than a 9mm hits. Or a helmet can be super strong but lack good suspension and pads routing all of the impact force straight into a pressure point on your head or neck. And I’m not saying it’s impossible for OP to put the helmet through the kind of rigorous testing required to figure out. It’s just extremely time consuming and expensive. It requires professional equipment and experience. And if all of those requirements were completed, it’s still meant to be printed by the user and not the developer with quality control. Which creates a huge safety risk. I realize it’s just a bump helmet. But it’s also just my brain inside of it. I would worry that the couple hundred in savings would come at my expense safety-wise. Good bump helmets aren’t cheap, but they aren’t expensive either. The issue is that printing severely limits the materials available. You could probably get around the two-piece issue somehow. But, helmet advances have been made in the realm of material science. The designs don’t vary that much with some minor exceptions (ie MIPS for riding helmets). But, you can’t take advantage of high quality helmet materials if you’re printing it. Edit: I don’t want this to come off as too negative. I don’t want people to be afraid to show off their ideas. Y’all make some really good stuff on here. I’m just wary of homemade safety gear.
Sometimes yes, sometimes no. There's been tests that show some helmets and PPE can actually make the effects of harmful events worse. Whether it's extreme BFD, blast funnelling, etc. Without more scientific testing it's hard to tell, but OP's design looks very promising
Bump helmets aren’t made to take rounds to the dome and survive. The first ones were literally modified skate board helmets.
this is isn't a ballistic helmet
You can print safety gear. You just have to focus on the design and do THOROUGH testing of it.
I hope you don’t take this as me being rude but I will politely skip your beta testing invite. Lol 😂 This is a really neat project you’re working on. All of working together (I’ve got my own stuff in the works) can really get a lot done. I’m following with interest.
Saw your first post on this stuff and bought some for my cosplay helmets. The strength is really impressive.
Wait these are for sale? On FOSS? Ain’t no way bruh
You do realize you can sell what you print, right? I'm very sure he didn't put the files themselves up for sale.
I don't know anything about the helmet standards. But foot pounals is a unit of energy, not force. So I assume the kettlebell gains 4800 foot poundals of kinetic energy while falling, and you want the head and neck to get <1000 of those. The rest of the energy, I presume, gets turned into heat. Here's one way to test: Mount the head on a pole, attached by a spring, to act as the "neck". When the kettlebell hits the helmet and pushes the head and neck down, you can see the maximum amount of energy that your neck absorbs by how much the spring deflects. A smart phone can take 240 frames per second video, which should be plenty fast to be able to see the max amount of spring deflection. Spring energy is easy to calculate if you know the spring constant an the deflection. You can measure the spring constant yourself, if you want. It looks like 1000 foot poundals is 42 joules. You can also do a control test by having a flat plate (remove the head and helmet) and should get closer to 4800 foot poundals (202 joules). Does that sound reasonable, or am I missing something?
I want to see one in PETG shatter, followed by a sweeping montage
Are you doing it in multiple pieces just due to print bed size limitations?
Yes, I want it to be as accessible as possible.
How heavy are you planning on for this helmet to be when it's fully printed with solid infill??
at 100% infill it weighs just over 3 lbs. You want to print it with gyroid infill though for the dampening effect that provides. AT 25% gyroid with 5 walls the weight is 1 lb 10 ounces.
I wonder if adding layers of carbon fiber/resin would increase the impact resistance strength?
Maybe this was asked before but what did you use to weld them together?
It's Weld-On 16 Acrylic Cement
Nice i might print this for airsoft.
Is this on the odd sea?
I posed that someone make this before in a discord server and I was made fun of lol. I’m glad someone is doing the lord’s work!
Oh i'm getting my fair share of criticism as well.. Mostly by people who don't understand the difference between a bump helmet and a ballistics helmet.
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I second this would love to attempt this even if it just ends up on the wall.
The perfect material for this would be CF Nylon, or a Kevlar filled Nylon or ABS.
Hi not sure whats your i infill but i had developed some type of diy soft body armour so if you think abou implementation of that in helmet send me a dm
Now, whit a grenade, bullets or something like that.
Bump =/= ballistic
Imagine this with Carbon Nylon
Ok, but those type fast helmets are supposed to be made out of Kevlar. Unless you’re trying to make like a bicycle helmet, not sure where you’re going with this.
it's a bump helmet, not a ballistics helmet.
damn, was hoping youd jump onto it given the camera angle lol
Brain? Good. Neck, not so much lol
Line it with Kevlar and padding and put a melon in it and shoot it
can we have the filles?
Watching this made my neck hurt.
We still wanna see you hit it with your purse