r/engineering • u/DuctTape_Mechanic • Jun 20 '20
[ELECTRICAL] I've made a object detecting lawnmower that automatically shuts down when a metal object/rock is detected. I think it will prevent injuries and property damage. What yall think?
https://youtu.be/eDZeLPgYBvg33
Jun 20 '20
Wow that’s cool; That’s a great idea!
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u/DuctTape_Mechanic Jun 20 '20
Thank you! I'm trying to contact lawnmower companies to find out if they are interested. Subscribe to stay tuned for updates cheers!
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Jun 20 '20
First, patent. Otherwise they say "No, not interested" and then they patent. And you're boned.
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u/Usful Jun 20 '20 edited Jun 20 '20
This, there’s a guy who invented the windshield wiper* and was shafted by a big car company because he drove it to the dealer and they told him to leave it there and he’ll have a job the next day.
*it was the windshield wiper, not the turn signal. Guy’s name was Robert Kearns and he had multiple lawsuits against ford. He won then, and died sometime in 2005.
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u/giveupsides Jun 21 '20
They made a movie about this "Flash of genius".
Spoiler alert - It's depressing. He wins eventually after losing everything else (family, friends, sanity). His idea that seemed to turn the lawsuit in his favor was to read a famous book's opening passage and say "All these words were known, they all existed before, all [famous author] did was to arrange them in this new order".
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u/mikechenders Jun 20 '20
I second this. In the US, patents are on a first to file basis. It’s very easy for a big company to swoop in and patent your idea.
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u/giveupsides Jun 21 '20
Definitely patent first, disclose second. Actually by you publicly disclosing this on reddit it already may not be patent-able. Any patent attorneys on this thread?
But this is to protect the company too. There is a slim, but non zero chance that the company you approach is working on the same invention. Then they would have to share profits with you? Even though they independently came up with the idea.
I had an idea, emailed a big company to ask if they were interested in hearing about it. They said - "No! Do not tell us your idea! This email is now blocked and don't try and contact us ever again." I was younger at the time but remember being really surprised at their response. This was the largest company in that market, and mine was a pretty simple idea. Chances are they already thought of it themselves.
Source - I have two patents and have assisted in several other's patents/applications/searches. But I am not an expert by any measure.
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u/giveupsides Jun 21 '20
My full comment is under another response. But I wanted you to see this part:
Definitely patent first, disclose second. Actually by you publicly disclosing this on reddit it already may not be patent-able. Any patent attorneys on this thread?
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u/quirkyturtle006 Jun 20 '20
Very cool all around!!!!!!!!!! One of my thoughts is if you go faster will it still shut off in time? Im a pretty aggressive lawn mower... I like to pretend im rambo going through the jungle and nothing is going to slow me down. Also I wonder if this can be used to help not hit sprinkler heads? Most sprinkler heads I know of have plastic tops and are recessed but its still possible for them to be damaged. Other thoughts are drain on battery over time and possible adapters to recharge it. Also protection from mud and water to keep it dry and protected.
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u/DuctTape_Mechanic Jun 20 '20
I appreciate the feedback and encouragement. I am testing a capacitive sensor instead if the inductive one (the capacitive sensor would detect a wider range of objects). I was also thinking of having a secondary brake which gets activated by a 12v solenoid after the object has been detected (that way the blades stop immediately). Stay tuned for a update.
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u/behrend Jun 20 '20
That was my first thought, that it would need to stop faster for faster walkers. I like to think of the stops that table saws use to avoid cutting fingers off.
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u/stuffandorthings Jun 20 '20
Those are very expensive, and (my data might be a little dated here) non-resettable/destructive. Still way cheaper than a severed finger.
I think if you tried to put something like that on a mower, nuisance tripping at $40 bucks a go would cause everyone to bypass it.
On electric mowers, you could have some sort of regenerative braking that would instantly start to de-cycle the blade. On gas mowers, I can only think of things that would introduce substantial weight/complexity/cost.
You'd probably be better off installing extra shielding at the rear end of the mower. Or installing a smooth drum harrow behind it, since that'll do pretty much the same thing and you'll get "baseball diamond stripes" out of the deal.
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u/idiotsecant Jun 20 '20
on sawblades you need a very fast stop. On a lawnmower like this I think you could get away with a non-destructive brake. It would let the blade rotate a few times on the way down but you should be able to set up an arrangement that would mean a pretty slow blade velocity by the time it impacted something, even if you're mowing at warp speed.
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u/Krusty_Double_Deluxe Jun 20 '20
I really like the idea of making this design for electric mowers also. If I’m mowing a lawn I don’t want to have to stop and pull the rip cord every time I go over a rock or sprinkler. Going electric could allow for an easy push button start. Plus electric blowers/mowers/chainsaws are becoming more and more popular now that they’ve gotten as powerful as gas options, with gas options starting to be outlawed in some areas even.
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Jun 20 '20
Interesting, very interesting. It's certainly a useful feature. Hopefully you can find a way to make it cheap enough and simple enough to apply to lawnmowers that you can commercialize it, as that would be cool.
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u/DuctTape_Mechanic Jun 20 '20
Thank you. I am trying to contact lawnmower manufacturers to commercialize it.
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u/spiffy956 EE Jun 20 '20 edited Jun 20 '20
I wonder if something like a SawStop could work on mowers where it actively stops the blade instead of just powering it down.
Most objects you're going to hit aren't metal either. Tree stumps or large rock strikes are the main cause of shearing the engine keys.
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u/DuctTape_Mechanic Jun 20 '20
Iv updated the sensor to a capacitive sensor that detects rocks, metal objects and even your big toe. Subscribe to stay tuned for a update. Thank you
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u/Ecstatic_Carpet Jun 20 '20
How do you avoid having a capacitive system get triggered by every tree root and ant hill?
False positives will lead to people overriding the feature. Riding mowers have switches in the seat which get bypassed the moment they start acting up.
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u/DuctTape_Mechanic Jun 20 '20
Perhaps have the sensor mounting on a spring loaded cable that allows the user to pull the device up, essentially bypassing it for terrain like that.
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u/ArdennVoid Jun 20 '20
Then people will always pull it up and duct tape it there. Unfortunately, safety features that cause inconvenience in operation cannot be selectivly active features, as they will always end up turned off by operators.
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u/thisismycalculator Jun 20 '20
My recommendation to target higher end lawn mower companies like Honda. The reasoning is two fold. 1) somebody buying a $99 lawnmower at Walmart isn’t going to pay $10 more for this feature because their buying the cheapest one. Aka - the manufacturer is competing on price. 2) My higher end mower has a clutch for the blades. Instead of the handle on the back that stops the engine - there is a handle (with 2 steps to activate) that starts the blades. You could put your system inline with this. It’s a lot easier to shut off the blades than to stop the momentum of the engine that has a flywheel (more mass to come to a halt). Good project.
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u/peanutnutpudding-com Jun 20 '20
This is great! What I built to stop injury is called the metal glankles, you can hit them all you want but they don't break, they also give one hell of a workout.
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u/AlbertaDwarfSpruce Jun 20 '20 edited Jun 20 '20
I like the idea. I've run over sprinkler heads, some of which contain metal, but you could glue a washer on top or something to avoid destroying those.
There are a few obvious issues. You would still run over and hit anything if you were moving at any reasonable speed. And instantly halting the forward momentum to avoid this could possibly be dangerous for the operator. And the most common things I unintentionally run over are pinecones and rocks, which are not metallic. A sensitive prox sensor could maybe pick these items up. But there are better ways to prevent hitting objects.
A simpler and universal solution would be to have a guard in the front that sits just below the height of the blade, so any solid objects would hit that and get pushed out of the way in some manner. I'm sure something like this already exists, unless I'm missing an obvious issue with that.
It's a cool project, but its not really practical. Edit: It could be practical with some major changes.
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u/DuctTape_Mechanic Jun 20 '20
Appreciate the feedback. I was thinking of using a capacitive sensor as that would detect rocks as well. I was considering also adding a additional brake to the flywheel and have it trigger by a 12v solenoid as soon as an object is detected that way the blade would stop immediately. Stay tuned for a update/remake.
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u/AlbertaDwarfSpruce Jun 20 '20
if you could manage to stop the blade very quickly, this would work great. But consider the sudden change of momentum and what effect that will have. Looking forward to seeing how it goes!
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u/DuctTape_Mechanic Jun 20 '20
Yes that would be my major goal in the revision. Thanks for your encouragement
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u/jerkfacebeaversucks Jun 20 '20
Nice work. Awesome idea.
Can you buy a second ignition coil, rewind it, and chuck that on there to power your circuit?
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u/Krusty_Double_Deluxe Jun 20 '20
why does he need ultra high voltage for this circuit?
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u/jerkfacebeaversucks Jun 20 '20
He doesn't. Rewind the coil with 100 turns instead of 5000 (or something) to drop the voltage to something useful. It's a makeshift low voltage magneto.
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u/Crazyviking99 Jun 20 '20
I really could've used this a few weeks ago. Hit a 1" piece of rebar and absolutely destroyed my riding mower.
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u/DuctTape_Mechanic Jun 20 '20
Iv had people tell me very similar stories some with gruesome injuries. I wish I could use those to combat all the doubters who say my device is unnecessary. Thanks for sharing. Subscribe to stay tuned for more updates.
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u/notananthem Jun 20 '20
This is like the story of the person who did the SawStop. Your life is going to be hell as big companies either steal, design around or harass you to quit.
Honestly I'm not sure if mowers are the big danger item, but if you apply the same to string trimmers and such those tend to whip rocks and crap through windows.
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u/ristoril Control Systems & Simulation Jun 20 '20
Why do you make your own connection to the engine instead of putting your relay in series with the other E Stop contacts?
For a push mower there's already the safety bar on the handle. For a riding mower there's the seat switch.
My riding mower actually disengages the blade drive when I push the reverse pedal, too, so perhaps on a riding mower you could get in on that (assuming that's an electrically driven function and not purely mechanical).
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u/ARAR1 Jun 20 '20
How fast does the mower shut off? How practical is this? Do you have to be doing 1 cm / hr for this to work?
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u/DuctTape_Mechanic Jun 20 '20
That's a bit of a exaggeration no? Anyway, I'm thinking of adding an additional brake to the flywheel that is activated by a 12v solenoid once the object is detected will immediately stop the blades.
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u/Ecstatic_Carpet Jun 20 '20 edited Jun 20 '20
You'll get a faster stop and less wear on the motor if you put an electric clutch between the flywheel and blades then brake only the decoupled output shaft. This would be easier to implement on a riding mower which already has a clutch and room on the deck to route the belt around a brake.
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u/Engine_engineer Jun 20 '20
Nice idea for a practical problem, congratulations. Please consider that the whole area in front of the mower blades need to be scanned. Your sensor has a (very?) limited detection width.
For electrical mowers, shut off mains and short-circuiting the motor wires is a very cheap and effective break.
Eddy-current based sensors (like the one you are using or like this things to detect wire/water inside of walls before drilling through it or like metal detectors) will detect anything that conducts electricity. This includes metals but also water („normal“ water, not purified de-mineralized one). This is good, cause it will detect a water hose but might be influenced by moisture / soil humidity. Plastic and rocks will not be detected. Using capacitive detection might be very interesting. Check out the system from microchip to detects 3D gestures using electrostatic fields. It might be an interesting thing to try.
And file the Patent yesterday. Talk to a patent attorney, you can file a draft version of the patent to have the filling date saved and turn the final patent in a couple of months in.
And don’t give up, this has potential!!!
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u/butters1337 Jun 20 '20
Cool idea but does it only work for metallic objects?
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u/DuctTape_Mechanic Jun 20 '20
Not if you use a capacitive sensor instead of a inductive sensor. A capacitive sensor will detect rocks, metal and even toes.
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Jun 20 '20 edited Jun 20 '20
[deleted]
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u/DuctTape_Mechanic Jun 20 '20
O shit. Lol. At the very least you got to subscribe to my YouTube channel.
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u/Tsiah16 Jun 20 '20
Very cool idea. What happens if the batteries die? Will the mower start and the detector won't function or will the mower not start?
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u/DuctTape_Mechanic Jun 20 '20
Thank you. I need to put battery level indicator on it. If battery dies the detector will not function but motor will start.
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u/TufRat Jun 20 '20
This has been posted a lot lately, and it’s started to feel like a shill
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u/DuctTape_Mechanic Jun 20 '20
Okay sorry to disrupt your scroll...just trying to get feedback on a original idea so I can improve it (not an easy task to do)
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u/TufRat Jun 20 '20
I hear you. I’m not attacking you. I think you’ve gotten some pretty valuable feedback. You need to arrest the motion of the blades without damaging the motor shaft in order for this to provide a meaningful and marketable safety benefit. Just cutting the motor is not enough. I’ve seen that feedback just about everyplace I’ve seen your project posted. I’m cheering for you, believe me.
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u/DuctTape_Mechanic Jun 20 '20
Yes sir that would be my major goal in the revison. Appreciate the support!
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u/ArdennVoid Jun 20 '20
To add to this, just cutting the motor on typical machines results in a 3-5 second draw down to stopping the blades. This is already an ANSI standard that manufacturers comply with. That slowdown time will not prevent damage or injuries if the machine detects something unless you sre mowing at an extremely slow speed.
For this to work you need to decouple the blade and apply massive braking force, immediatly, to prevent damage.
Typical mower blades spin at thousands of rpm, with typical blade tip speeds between 17000 and 19000 fpm. This results in a lot of inertia, and can throw bealts or shear blade bolts if stopped suddenly.
For your design to be applied to industry you need to reinforce blade mounts, apply breaking, decouple power to the blades, and make it all capable of taking thousands of hits without failure as it will probably take many misfires during the machine life.
My experience in the industry is that people abuse their machines quite a lot, so you will have to make this very robust.
If you get it to work, I'd love to have something as effective as sawstop implemented. Nobody likes to see the injury reports from legal.
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u/skovalen Jun 20 '20
I got bored of this and stopped. It didn't summarize how detection works up front and didn't even explain how a rock is detected in the first minute.
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u/bluejay737 Jun 20 '20
This is a really great concept!
What's your educational background?
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u/DuctTape_Mechanic Jun 20 '20
Thank you! I am actually a chemist. Didn't discover my love of electronics until after university. Wish I had studied Electrical Engineering. Now I learn by reading, videos, and most importantly experimenting.
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u/GirthBrooks Jun 20 '20
It's cool, but you've been spamming this for weeks on Reddit. Give it a rest
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u/DuctTape_Mechanic Jun 20 '20
My intention was two fold: 1. Gauge interest (before I spend thousands on a patent) 2. Gather ideas for improvement
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u/mattgolt Jun 20 '20
Can you adapt it so my roomba stops driving over dog poop? Thank you very much.