DIY LATCH System Retrofit

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Introduction: DIY LATCH System Retrofit

Cars made after 2002 have a LATCH (Lower Anchors and Tethers for CHildren) system in place from the factory, but there aren't any kits available to retrofit older cars. My car, a 1960 Ford Fairlane 500, didn't even come with seat belts, so I decided to custom fabricate a LATCH system of my own to enable the safe transport of my daughter while avoiding the expense and hassle of getting seatbelts put in.

Step 1: Buy Hardware

Purchase:
2 x 1/2" thick, x 6" eye bolt w/nut zinc plated
2 x 1/2" nuts zinc plated
2 x Carabiners (locking ones are probably overkill, but get good quality ones that latch into a hook system when closed)
4 x 1/2" lock washers zinc plated
4 x 1/2" cut washers zinc plated


(image shows disassembled parts on left and assembled version on right. The washers will go on either side of the sheetmetal of the car.

Step 2: Make the Holes

Remove the lower seat cushion and check the floorpan for mounting locations. The bolts need to be accessible from between the upper and lower seat cushions. My floopan had a handy design stamped into it, marking a good spot to place the bolts, roughly 1/3 away from each other and the sides of the car.

With the upper seat cushion still in place, position the eyebolts so that they are flush against the bottom of the cushion and mark the area that the base touches.

Once the positions are marked, use a punch or drill to make a pair of holes about 1/2" in diameter. While this shouldn't be a problem in most cars, you should check to make sure there are no fuel lines, brake lines, or electrical wires located on the other side of the sheetmetal where you intend to place the hole.

Step 3: Secure the Bolts

Begin by placing the nut, lock washer and cut washer onto the eyebolt, and then place it into the hole. Using the nut, adjust the depth of the eyebolt so that it sits behind the upper cushion. You don't want to be able to see it without pushing on the cushion and you don't want it sticking out at all.

Once you have the depth set, climb under the car to place the remaining nuts and washers onto the opposite end of the eyebolt. Be sure to put the cut washer on first, followed by the lock washer and finally the nut.

Step 4: Modifying Car Seat LATCH Belt

Because the 1/2" eyebolt is significantly thicker than the bars used in factory LATCH systems, the existing latch connectors will not work. Simply slide a carabiner through the loop in the belt. Be sure to only use climbing or safety grade 'biners. I find that this step is a big improvement to the original system, and is more robust in addition to being easier to deal with.

Step 5: Install the Car Seat.

The final step is to install the car seat by hooking the LATCH system into your new retrofitted attachment points.

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    73 Discussions

    It's entirely possible to safely retrofit a latch anchor system into a vehicle that doesn't have a manufacturer kit, but this is not the way to do it. Floor plate washers are not a safe way to retain the hardware; you should be using welded in backing plates that are tied into the floor cross braces or are large enough to distribute the load (6x6" is the minimum generally), or are tied into the roll cage sandwich plates (I understand not applicable here). I understand you don't want to modify an older car like this, I am with you there.. but you're better off just refraining from taking the kids in the car till they're a little older rather than using sub par hardware for a false sense of safety.

    For mounting hardware to mount the seats to the proper floor plates (not fender washers!) you should be using either seat belt tabs and bolts from another vehicle (plenty in the junk yard) or from a shop that sells belt tabs and proper hardware for installing racing harnesses in race cars (those are intended to take high speed impact force and are more than sufficient for car seat anchoring). Eye bolts like this are not even welded closed and they WILL pull open in an accident. I have seen seat belts held in by eye bolts fail the eye bolt and people killed from it. Not even welded eye bolts are safe because they break at the threads when they bend there.

    I know this topic is like forever old, but I am just finding it.

    My professional experience (30 years) is in the auto industry. All of the people who are questioning the strength of this set up have never held the thin little manufacturer installed loop of wire metal car seat latch point in their hand.

    The factory stuff is so thin (remember he had to add a carabiner because the original hook wouldn't open far enough to latch) that if you took the two bolts out of the factory piece you can bend the hooks with your bare hands.

    I have used the same two eye hooks he used on my motorcycle trailer and they did not bend with a 600lb motorcycle pulling a side load during a impact.

    The washers used are plenty big enough.

    I think consumers believe the car makers use high grade titanium and carbon fiber to mount car seat latches in their vehicles. The reality is, they are doing their best to make it thin and light as possible to save weight and money. The factory hooks can probably hold double the weight needed.

    The set up he has here would hold 10x what he would need. Those old cars used REAL METAL when they were made, he wouldn't have any issues.

    Nice Job sir!

    4 replies

    You're using aluminum carabiners to haul a motorcycle on a trailer? Those carbiners were unable to properly retain my gear bag on a bumpy road! They're only rated for a few hundred pounds (when they're rated at all). They're a far shot weaker than even those weak looking stamped steel hooks that come on child seats. The steel hooks on a car seat are made from heat treated steel that's designed with a 10,000Lb maximum load... and even those have been known to break in severe accidents.

    Here are the two alternatives you have with an antique car that didn't come with any seat belts.: bolting in aftermarket seat belts or making a latch point for the car seat. The keychain carabiners pictured were placeholders so I could photograph the project. They were replaced with load rated carabiners for actual use.
    In the final analysis, antique cars are inherently dangerous, lacking even modest passenger safety consideration in their design. This addition enables these cars to transport car seat passengers with equal safety as the seat belted passengers. Which is to say, marginal at best. From the greater perspective of impact designed and tested autos.

    I have a third alternative, don't transport the child in this vehicle. Children have no say in these situations and it's our jobs as adults to make sure they are safe.
    Above all else (even though safety is #1), this is illegal. Possibly even child endangerment.

    It was not tested by either car seat companies or the car company, therefore will void any warranty on the car seat.

    I have never seen a seatbelt welded to a car frame. Replacement car seat lap belts are bolted through the chassis, with a big washer on the back side. The keychain carabiners in the photos are placeholders and listed as such. They were replaced with rated equipment.

    The safety concerns surrounding antique motoring are myriad. Was eventually involved in a t-bone accident in this car. These old cars simply crumple up like cans on impact.

    This is really great, I love how they sit down below the seat, can passengers in the rear feel them much when sitting on them? I found this looking for latches for my 2001 ford. I do overhead hoisting and rigging and I have several of those eyes in my tool box at work i will grab, the best part is even the True Value ones are graded so they are approved for a load such as this.

    So many of you are just so blindly negative, you dont seem to realize the load characteristics of this situation the system is as strong as the waskist link, a 300# test eyelet x2, but the 1" webbing on the child's seat is only about 125# also keep in mind that in a collision not only will the lets say 50# object not apply 100% force on those connections but the job of the webbing is to deform and absorb the pressure before it even gets to the eyelets. So lets say under speed that 50# becomes 500# (which is double the load of the belts the kid is in already) but the belts dont take 500# they stretch and slow the load.

    We can go in to some deep physics here but the point is with auto manufacturers is most of this is a "good enough" approach, do you think they really run load from each angle on each bolt in the car, they just bump it up a grade and good enough, these bolts if anything will be the only thing that hold up in an accident.

    This is still better than my original solution, So according to all of the folks who think the OEM components are infallible, I say in the 60's no belts means they designed the car to be safe without them right???

    I think a lot of people are forgetting that even if you installed seat belts into a classic car, your options for mounting the seat belts are about the same as what was shown here: Drill through sheet metal and hope for the best. Having said that, I would agree with some of the concern that this isn't as safe as possible. Were it up to me, I would make three considerable modifications to this system.

    First, I would install a mounting plate to the underside of the vehicle. This is the same thing that they did on old cars for seats (and later on, seat belts). Get a super heavy gauge piece of steel, and weld it to the spot you're going to anchor the bolts. The piece should be as large as will fit, so that the force of an impact is distributed over a lot of space.

    Second, I would use larger washers made of heavier duty steel. The Home Depot specials in this instructable just seem far too small to do any real good in the event of a catastrophic crash.

    Lastly, I would use high grade steel eyelets with the eye welded together. This would ensure that the eyelets aren't unbent and release the car seat.

    (I would also be sure that my carabiner is the heavy duty climbing grade. The one used in the photos looks more like the keychain grade ones I have lying around the house.)

    Now, given those changes, I would be more than comfortable with having this system in my own 1960 vehicle. Why? Because first, it's as safe as you can get in that kind of car. Even seatbelts would have to be a custom install like that. Also, if there's a wreck big enough to dismount that system and mom and dad were in the car, that kid's an orphan anyways. The cars of that era were tanks. Sheet metal was several times thicker than what you might have on your 2012 Kia. There are no crumple zones or collapsing steering columns. My point is that in an accident, if you're hitting a newer car, they're going to take the brunt of the impact as your sturdy heavy steel on a boilerplate thick frame vehicle plows through their tissue thin steel and plastic unibody car. Any accident resulting in enough force applied to dislodge this system had at least one fatality associated with it. I'd just about guarantee it.

    Over all though, this is a decent idea. With a little reworking, it could provide something that would at least allow the use of this car. I'm not saying that I'd drive the kids everywhere, every day in it, but it's a classic car. They get driven on Sunny Sundays and in parades.

    1 reply

    An interesting video of just the type of thing you mention in your post: a collision of a 1959 Chevy Bel Air into a 2009 Chevy Malibu. The Bel Air takes a bigger beating than I would have ever guessed:

    http://www.youtube.com/watch?v=cJrXViFfMGk

    torklugnutz, Brilliant, all the materials you used are more then adequate. The only thing I can think of to reinforce the base would be to use 10G plates approx 4"x4" between the body steel and the fender washers. This will give you better spread of force on impact if you were ever in an accident. It will also distribute the load shift much better and put less stress on the body steel. Don't forget to check the biners for wear every couple of weeks, so they are always in good repair. You could put some teflon spacers in to minimize the contact points. Thats my 2 cents.

    2 replies

    thinking of adding some latch points to the cargo area of my wagon. this is good info. def want to be safe, also want to be legal. thanks for the pointers.

    before I forget, truck supply stores have better anchor eyebolts that would be the only thing I'd do different.

    I did something similar to this on our Volvo 9 years ago. It came out a year or two before the latch system and I liked the idea of easy access. I used something like this - 1/2" Quick Link Chain Repair Link (see http://ep.yimg.com/ca/I/cvfsupplyco-store_2106_15067902) to attach a short lenght of chain, about 3 or 4 links, just enough to come out of the seat. I attached the repair link to the two inside seatbelt attachment points and then secured the seat to the chain. Once you ratchet the seat down, it did not move. I liked having my son in the center of the car, too.

    I commend the author of this subject for doing this. Many of you are under the impression that car makers use some type of special metal in their brackets that withstand a million pounds of force. Others bash the author for putting his childs life in danger. Interesting. Do you all have your children riding in the absolute safest car? Are your car seats made out of some type of industructable material? Do you really think the amount of force required to completely sever the eyebolts will not have an effect on the other components in the car seat? I have made my own latch and tether brackets for my daughters Recaro child seat out of 1/4 inch steel and used the factory mounting points and grade 8 bolts in my 1970 Buick. There is no aftermarket kit available for us classic car owners, so we must use our common sense to make the trip safer for our loved ones. The forces required to cause thick metal brackets and high strength hardware to fail would mean the actual accident is extremely severe and not survivable regardless of safety equipment used. I drive a 2009 Honda Civic and have inspected the LATCH system on this car. It is much thinner and less substantial than this authors design. Now, I would reinforce the bolt mounting point a little more, but do you really know what it would require to rip the bolts, nuts, and washers completely through the floor?
     
    The amount of technology in todays cars (crumple zones, SRS's, belt pretensioners, ABS systems, VSC systems, etc.) cannot be replicated and are much more of an issue in survivablity in a crash than this set-up will ever be. Loose and improperly installed car seats by parents far out weighs this type of modification. In 20 years we will wonder how we ever transported our loved ones in todays unsafe high tech cars and equipment.

    1 reply

    It's not a matter of the car seat failing or the hardware used to mount it failing. It's a matter of whether or not the points where the anchors are installed are fully reinforced metal, that will prevent the washer from deforming the metal and pulling right through the drilled hole.

    I would recommend more than just heavy duty washers. A 3" square of 1/8" thickness steel plate welded to the underside of the bodywork would be at least adequate to distribute the forces and prevent deformation of the anchor point holes in the event of a collision.

    (I'd consider it to be over-engineered, but my child's safety is worth over-engineering.)

    I like this project, I even thought of doing myself. But I have some concerns. I get the feeling that "curtisjoewalker.com" is single! LOL Is this Mom approved?

    Here are my concerns:
    1. Latch systems are tested. Is this? Any part of it?
    2. Look at those "eye bolts" notice how it is essentially a piece of metal bent to a circle. On impact would they bend out and release the car seat? How about at least getting them welded shut. Tie a cider block to it and drop it off a parking garage. Where does it fail?
    3. They make "body washers" for the bolts of the seat belt. They are huge washers meant to distribute force so the bolts won't rip out of the body of the car.
    4. It's just hard for me to take this seriously when you say something like this: "safe transport of my daughter while avoiding the expense and hassle of getting seatbelts put in." Seatbelts might be more expensive than your lag bolts, but they go in *just as easy* as the work you put in for this.
    5. Did you consider actually buying a *real* latch anchor and putting that in? At least that way you get a tested product, some some hardware store mish-mash.
    Sorry to sound harsh, as I said I thought about doing this myself. My wife, rightly, thought I was a moron. It's our kid we are talking about here.

    Ok OK that said I take my dog on my motorcycle. See, I *am* am moron, don't listen to me.

    4 replies

    1. No. The products all have a certain load rating on their packaging, but I didn't do any math or computer modeling to figure out the failure points.
    2. The eye bolts are quite thick, and while they aren't welded, I think the amount of force to distort them would probably turn a human baby into jello.
    3. Washers are a good point. I think mine are good enough and that's what they had on the shelf at Home Depot. Bigger wouldn't hurt.
    4. Hassle = damaging the period accuracy of the car interior. Expense is about $25 per seat plus installation. There are no such things as accurate rear belts for my car. They simply did not exist.
    5. I did look at getting a factory LATCH kit, but the dealers don't sell them. The best I got was the top latch anchor point retrofit kit, which isn't useful.

    PS. yes, it's mom approved, though she's not an engineer either.

    Bottom line, it's an antique car and this is the best way to put a car seat in it. Aftermarket seat belt kits would bolt in in virtually the same way and be ugly.

    Its not so much the child becoming jello as much as the child being the force that will make the eye bolts jello. Your talking the child's weight multiplying by powers depending on the impact.  example: a child at 10lbs would require 300lbs of force to restrain the child at 30 mph. So how heavy is your child and how sure are you about the strength of the eye bolt.

    You need to know more than the speed of the car and weight of a child to measure the force. You need to know the deceleration and what distance the deceleration it is over OR you need to know the number of Gs. Looks like you are assuming 30Gs which is probably about right for most accidents but they certainly get worse that 30Gs.

    Yes, but I am generalizing a point. The other thing one should note is that the bolts are in the sheet metal not the frame. Another factor for fail. Sorry, neat Idea but not worth the risk of my or anyones progeny.