DIY LATCH System Retrofit
Intro: 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.
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.
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.
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.
69 Comments
amora1731 1 year ago
hammer9876 14 years ago
I suppose this is better than no car seat - or seat belt - at all, but there are good carabiners used by climbers who bet their lives on the things and there are cheap carabines sold at big box stores which are to be used on nothing heavier than keys.
mjzraz 2 years ago
derek244 13 years ago
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.
mjzraz 2 years ago
Stickytack 13 years ago
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.)
jjackson64 7 years ago
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!
mjzraz 2 years ago
destrux 6 years ago
destrux 6 years ago
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.
cyrusz 11 years ago
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???
jclements6 12 years ago
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.
total-lightweight 11 years ago
http://www.youtube.com/watch?v=cJrXViFfMGk
mackamitsu 15 years ago
abudanger 12 years ago
mackamitsu 15 years ago
Darrin McNeice 12 years ago
swissarmychainsaw 14 years ago
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.
torklugnutz 14 years ago
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.
Splaxx 14 years ago