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Catalytic Converter Theft Deterrent

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(+8, -1)
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In my part of the US, and I imagine all over, we are having a rash of catalytic converter thefts due to the soaring value of precious metals. The theives target pickup trucks and SUVS because they are high enough to just slide underneath with a cordless saw and hack right through the exhaust pipes. It takes about two minutes, and they're getting so brazen as to do it in broad daylight. Here's my solution.

In posting this I am breaking somewhat with HB tradition, and I hope I will be forgiven. The reason is that I am currently baking this particular bun; what I need is to have it unbaked. I need all you devious deviants to tell me how you would go about defeating it.

What I am building is a simple framework that holds in place two lengths of 5/8" ID pipe, which run paralell to the exhaust pipe on either side. Inside the pipes are free-floating segments of 1/2" steel round-rod. The pipes are closed on the ends, and packed with grease so that they will not rattle. The framework holding them is attached to the U-bolts on each side of the cat, and cross-bolted with eight to ten bolts above the cat, just under the vehicle's floorboards, where a saw blade cannot reach, so that even if the U-bolts are cut, the assembly still must be removed manually in order to cut the exhaust tubing. If the theif attempts to cut directly through the device, the round-rod will simply spin inside the pipes.

I'm sorry I can't upload a diagram to make this clearer, but my dial-up service seems to be having a bout of indigestion. Anyway, have at it.

Alterother, May 06 2008

If you liked this one... cheap_20tricks
[ye_river_xiv, May 07 2008]

New catalytic converter package design http://www.flickr.c...7604179216722/show/
1st pic.: turbine screen for catalytic converter [rotary, May 08 2008]

Catclamp http://www.catclamp.com/catclamp.asp
Basically, a cage around it. [jutta, May 10 2008]


       Recently I've been wondering why the muffler etc. isn't under the bonnet; surely they'd last longer and be less prone to salt and speedbump damage.
FlyingToaster, May 06 2008

       "...I've been wondering why the muffler etc. isn't under the bonnet..."
So CO doesn't enter the passenger compartment.
phoenix, May 06 2008

       //So CO doesn't enter the passenger compartment//   

       I thought of that but the auto industry doesn't seem *that* protective of people that have already bought their vehicle.
FlyingToaster, May 06 2008

       I wonder whether you could rig up an SUV you didn't need any more in such a way that cutting through the exhaust pipe would sever a concealed, tensioned wire, causing a heavy section of the carefully prepared chassis to fall cleanly off on top of the cutter. Probably not.
pertinax, May 06 2008

       Get a round muffler or resonator that is larger than your cat. Cut it in half, remove the insides and then weld it around the cat. Then fabricate a "dummy" cat by taking 2 pieces of sheet metal and shaping it and putting the ridges in it to make it look like the real thing and weld it to another section of your exhaust pipe (top and bottom). Then when someone comes along to get the "prize", they will only steal your fabricated creation and an 18-24" section of your exhaust pipe.
Jscotty, May 06 2008

       I don't understand what holds the pipes in place. It sounds like the assembly that does is attached with bolts you can't get to, so I don't understand how you are getting it on unless the attachment is using bolts coming down from inside the truck. In any case I assume that a theif finding any covering will not stay and attempt to defeat it, but will just move to an easier target. Watch about covering the cat as you may cause heat issues or create a heat path to places that were previously insulated (carpets).
MisterQED, May 06 2008

       Concerned SUV owners should get pneumatic suspension installed on their vehicles so there is no room for anyone to crawl underneath it when parked. Pull into your parking spot, shut off the engine, and pssssshhh, your vehicle now sits so low you could barely roll a golf ball under the sucker.   

       Of course, resourceful CC thieves will then simply relocate their business to intersections having extremely long stoplights.   

       And by the way, sp: thief, thieves, parallel
Canuck, May 06 2008

       I like the pneumatic suspension idea, but I think rather than lowering when parked, it should be rigged such that when sawing is detected, it instantly depressurizes, lowering the car/truck so it sits on its new meaty support.
TIB, May 07 2008

       A pipe wrench would defeat this.
Voice, May 07 2008

       Buns away! I'm not entirely sure that all the steel rods would rotate. However, if you give them about an inch of play on the ends of their housing, they ought to roll, and slide along the length of the housing enough that cutting will take significantly longer. Various springs mounted to the ends would greatly enhance security, but might make the complexity of the device unnecessarily excessive. I would also suspect that in this application, even smaller steel rods, but in greater number, would be preferable. 1/8 inch is readily available, and should be able to pack in tighter than the 1/2 inch ones, making for more overall steel to cut through. Titanium welding rods might also be worth looking into, although they might prove to be a decent target in their own right.   

       Mixing the grease with some abraisive material might be worth considering as well. Doing so would eather make it into a cutting agent, and help the criminal, or wear down the saw blade, and ruin the criminal. I'm no chemist, but I suspect an easily prepared mix will damage the blade more than the rods.   

       I do suggest that you consider whether this idea will be properly proof against a plumber's hacksaw. Without a good look at a diagram, it's hard for me to tell in my imagination.
ye_river_xiv, May 07 2008

       // I'm wondering why the the muffler etc isn't under the bonnet //   

       Heat and packaging for one. I'm also wondering if it would be effective at noise reduction being so close to the engine.   

       And yes, [FT], we *are* that protective.
RayfordSteele, May 07 2008

       Claymore mines ?
8th of 7, May 07 2008

       Yes, but make it out of copper.
Ander, May 07 2008

       <Terry Thomas> "Have you seen my cat?. It fell orf the roof!". </TT>
gnomethang, May 07 2008

       Here in New Zealand by law all companies buying scrap metal need to ask for ID and address when they buying scrap metal from the public.
Pellepeloton, May 07 2008

       //Get a round muffler or resonator that is larger than your cat. Cut it in half, remove the insides and then weld it around the cat.//   

       Zombify your cat for catalytic converter protection! What would an undead cat say anyway? I would guess "Meoooooow! MEEEEOOOOWWW!" (translation: let me out of this blasted muffler!)   

       [+] for the anti-cutting rotating rods.
sninctown, May 08 2008

       Fi-Shock. 20,000 volts tends to make me keep my hands off. In fact, that renders your entire vehicle untouchable until the charger is defeated.
elhigh, May 09 2008

       grease? Are we forgetting how hot that baby gets?
WcW, May 10 2008

       I like this. A key aspect to such an antitheft device is that it should be subtle, which this might be - the saw just is not getting through (damn saw!) and the thief finally leaves in frustation. If the device were obvious or designed to hurt thief or damage saw, the angered thief might trash the car out of spite.   

       The rotating rod as an anticutter is neat also.   

       If I were a thief, after I ran into this a few times I would look for the rods parallel to the pipe, then remove a segment of each rod with my bolt cutter, making room for the saw. If they ran inside the exhaust pipe this would be more difficult.   

       It occurs to me that a boltcutter-like device, with a larger gape, might be devised for the express purpose of cutting through exhaust pipes - much quieter and quicker.
bungston, May 10 2008

       How about an exhaust pipe inside of a pipe while using concrete or epoxy mixed with rocks and sand to fill in the gap instead of grease?
Jscotty, May 10 2008

       just use your extra pipes to sheath a couple of cans of pepper spray.
pydor, May 11 2008

       Just a thin coating of strong epoxy should take care of your average hacksaw.
Spacecoyote, May 11 2008

       The catclamp looks good but it's somewhat expensive. How about just 1 or 2 parallel steel rod attached with about 100 pieces of regular safety wire? That would be sufficient to cause the thief to move on to an easier target and would be much cheaper than this idea or the catclamp.
bneal27, May 11 2008

       Spacecoyote, you and me are using different epoxy. I'm curious, therefore - what is this wonder epoxy of which you speak?
david_scothern, May 12 2008

       If scrap steal goes any higher they will start cutting at the collector and take the muffler too. If you strap other valuable metals to the object to be stolen don't you make it a more valuable target? Unless you plan to secure the entire system the thief will simply take more of the system. Might be better to secure the cat to the floor of the car making it very hard to remove even if you do cut the pipe.
WcW, May 12 2008

       Hacksaws get gummed up pretty easily, because they are made for cutting things that are hard enough to sharpen the blade.
Spacecoyote, May 13 2008

       For those questioning the postioning of the mounting bolts: they are in between the cat body and the vehicle floorboard, where you can get at them with a socket wrench and an extension. The redundancy of eight to ten bolts means it will take a long time to remove.   

       For those questioning the grease: I used lithium grease, very heat resistant.   

       I have built a prototype, which I have found impossible to cut with anything short of an acetylene torch. The inner rods, which I cut into 1" segments, spin very nicely against the blade of a recip saw or a grinder with a cutting disc. As per your suggestions, I went after it with a 36" bolt cutter and a 24" pipe wrench. Result: grease everywhere, tired arms and a broken bolt cutter. I am now building another to attach to my Jeep, which I have protected in the meantime by wrapping grade 80 chain around the tasty bits.
Alterother, May 15 2008

       [8th of 7], I also considered claymore mines, which are typically my first notion when confronting any sort of theft deterrent problem, but alas, the backblast was not very friendly to my neighbor's Bronco.
Alterother, May 15 2008

       Many apologies to irate halfbakers for posting this update seperately. Moved from original posting:   

       It works! I installed one on my Dad's GMC Sierra, which is frequently parked unattended in town (I live way out in the boonies, so my Jeep hasn't been preyed upon yet.) Anyhow, the device on his truck (we're calling it the "Cat-Jak) has picked up several fresh scars from a recip saw (we figure multiple attempts from a single attack). His exhaust components remain unscathed. In similar news from my neck of the woods, a cat-theif at our local Wal-Mart got hauled out from under an SUV by his ankles and promptly received a sound beating. Police took him to the ER, where he reportedly complained to them that the unknown assailants "stole his saw." Also, the owner of a machine shop pumped approximately 30 rounds of buckshot into the van of two men who were interrupted in the process of pinching nearly $4000 worth of scrap iron and aluminum from his yard.   

       And there was much rejoicing.
Alterother, Jun 13 2008


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