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Tesla Model 3 rear seat lock

by jonco223 Jan 26, 2019
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A few of my friends have said that the Model 3 coming off of the factory now is coming out with shorter bolts. The bolt length is only about 5 to 7 mm long. Any idea what can be done with such a short bolt? The model 3 I have has a bolt that is about 15mm long.

Sure - just replace the short bolts with longer ones. My car uses 25mm long M8x1.25 bolts. The technical name for the bolt is: "Button Flanged Socket Head Cap Screw, M8-1.25, 25mm Length".

Can confirm, just took delivery of my Model 3 and the bolts are too short. These seem integral to the security of the center seat belt so I wouldn't skimp when choosing longer bolts. I have these on the way: https://www.mcmaster.com/92137a649

I have watched this creation of yours through some other Vlog months back before I was supposed to get my Model 3 living in Europe, Italy. I had already spotted a 3D printing shop and had it print the kit thanks to your files that you made freely available. Perfect job and many thanks for doing this. I feel somewhat a bit safer to have my valuables protected in my trunk. Rudy

Ok, installed one seat lock and it works great!

Had to glue up two more cylindrical pins on the other rocker arm cap. Once glued, that should take care of the weak spots. There is not a lot of torque on these pins once the parts are put together and bolted into the car.

As I was returning from the hardware store with springs, nuts and washers, I saw my neighbor getting the wing window on his Model S replaced. Seems all the cars that were parked outside last night along my neighbors street got jacked up. Got my lock in just in time.

Sentry mode should deter break-ins once it is universally deployed and the seat lock will stop anyone from entering the trunk space, if they still decide to break in. Not sure how to inform potential burglars that the trunk is locked, however. I wonder if signs in the rear wing windows, saying "rear seats locked" would help prevent the wing windows from being smashed?

I really like the design of this latching system, as it provides a clever way to lock the seats when not in the reclined position. I haven't tried the latch out in my car yet, that happens later today.

Last night I received 2 sets of the printed parts from, "Print a Thing", which is a 3D printing service that is offered on the Thingverse site. I ordered the parts as specified by Jon, except in black PVC and with the option to have the parts cleaned up a bit above the standard, not sure how the cleaning part works exactly. 2 sets of parts and shipping cost $66.30 USD.

The parts look like the ones in the photos. A little rough with some PVC filaments and odd pieces of PVC stuck to the parts. A little light sanding and sculpting with an razor blade took care of the rough areas.

I'm not sure Print a Thing had the exact MakerFarm printer that Jon used. This is the first time I have ordered anything printed by a 3D printer. As expected, the resolution of the printing is not that refined and the printing algorithm prints interesting patterns and shortcuts to reduce the amount of PVC required . The main problem with my parts is that they failed in several spots, due to lack of strong adhesion or fusing of the PVC.

The Rocker arm cap has three cylindrical tabs that fit into corresponding sleeves in the rocker arm linkage. The three tabs had to be sanded a bit to allow them to fit into the sleeves. When I attached the cap to the linkage, all three tabs sheared off cleanly at their bases. I was able to extract the tabs with a sheetrock screw and epoxied them back on. I reassembled the parts and they are holding so far.

I ordered the adjustable base and one of the bases split across the oval bolt hole. Again, this split happened along a horizontal printer plane. This was also easily glued back together. The only other failure so far is that one of the cylindrical tubes that allow the rocker arm to rotate also sheared off from its base.

Today I will get the springs and nuts and install in my car. Will see if the joints and parts can hold up while in use. Will report back.

I did find other 3D printing services around the country who said they could print these parts with better quality materials and printers. Print a Thing also had other material and quality options. I think these parts should probably be printed at a higher quality, and price, than provided by the MakerFarm printer to make the parts more durable.

Does, anyone else have experience with 3D printing who can suggest a printing service, material and quality level to use for these parts?

Sorry to hear about your troubles with the print quality. I had another user request a version that would use bolts/screws to assemble and so would be less sensitive to the print quality. Perhaps you would have better luck which that version. That remixed version is here: https://www.thingiverse.com/thing:3431139

Tesla Model 3 rear seat lock with bolts/screws

Hey, awesome design, it works amazingly well! I've got one suggestion that I'd really like to see (but am no good at 3D modeling myself). The spring points are the weakest part of the design - they constrain printing to PETG for heat integrity, and they're always the first thing to snap when building. I'd really like to just be able to use a long screw through a continuous hole there - it'd be indestructible that way! Just a long screw, hook one spring on the head side, use a nylon lock nut on the other side to hold the other spring. In the base could be screw holes as well to hold the spring there as well, but the base's side is stronger than the arm side so less important.

Aside from that, a brilliant design that works ridiculously well. The only challenge now is to get them to as many people as possible!

Jon, first of all, nice work! I was playing around with this, and it seems like if you made the rocker arm assembly like the attached photo, then there would be no need to maintain the two different models, and the extension arm bit would be completely optional. Mechanically, it seems to work.

You may want to consider using fillets at the base of the different posts to reduce stress. Just a thought.

I'm not sure what I'm doing wrong, but the tension of the springs pulls the whole thing apart.

I think the problem is that my springs have too much tension. They don't stretch like the ones in your video. I've bought about $9 worth of springs locally. If anyone has a link to springs that work, I would appreciate it.

If you have a Harbor Freight available, item 67562 has the springs I used. Amazon also sells similar spring assortments, like this one: https://www.amazon.com/Performance-Tool-W5200-Spring-Assortment/dp/B0002KO1X0/ref=sr_1_5?ie=UTF8&qid=1549335765&sr=8-5&keywords=spring+assortment

If you need more specifics to locate them at a local hardware store, the extension spring details are: 5/16" x 1-1/8" x 0.018"

I ordered the spring assortment from amazon that you linked. The spring tension seems much more appropriate compared to the springs I tried previously, but the rocker arms are still pull out a bit when the springs are attached. I think it will still work as the rocker arm cap doesn't pull away enough to pop out, but I may try a bit of glue to keep everything lined up. Thanks!

Nice work on this. It has a satisfying snap into each position. I mentioned it in a video here: https://youtu.be/V3VXjbR71_A and I've been getting comments and emails asking where people can buy it. I tried to point them to the Order This Printed function here, but it's just too much for people who aren't familiar with this stuff. Do you have any plans to sell a kit? If not, I have a few suggestions to make it a little more user-friendly.

1) Split this into two thingiverse posts, one for the long handle and one for the short handle, and link between them.
2) Give them some instructions on how they can get it printed and which material to choose.
3) Add links to the springs, nuts, and washers.
4) Maybe also do the same at shapeways with a link to there so you can get a commission if they want premium parts.

Thanks so much for this! Just installed a red pair on my friend’s red Model 3 (will print a blue pair for me when I have some blue filament installed).

On the driver's side latch, we had to shave the outside (door side) of the latch to get it to work. If a lot of people run into this, perhaps you could make the bolt holes a bit wider to allow some side-to-side adjustment. But this is really cool.

I appreciate the feedback. On my car both of the latches are biased towards the drivers side relative to the striker, hence the asymmetric design. I have about 2mm clearance where you had to trim the bolt piece to fit. Since there appears to be some variability between cars, I have updated the design of the base piece to allow for the side-to-side adjustment you suggested. Thanks.

Perfect! I urge everyone to print the new adjustable base - I don't see a downside.

Thanks again.

This is awesome & great to share this on Thinkingverse. My Model3 was broken into while having coffee with a friend - I was away from my car for <20 minutes. Trunk was empty, but replacing the window glass was a total pita & took a couple of weeks for the certified repair shop to receive a new piece of glass from Tesla (they are in high demand with all the break-ins). My shop said we were the 8th car of that week.

So I get how this device prevents the theft of items in the trunk, but I'm also interested in something visible to a thief to avoid the window breakage + repair. I'm thinking of something like a small, printed lock (maybe a Yakima or Thule looking type of lock) so the thief knows they can't get into the trunk (or view trunk contents) even if they break the window.

Another option I chose in the short term is a sticker on the window that says (Empty Trunk Always!), but I really doubt this will stop a future break-in.

Thank you so much for creating and sharing your Model 3 rear seat lock design here on Thingiverse! This looks like a far better and more robust solution than that lame (and easily defeated) "DropLock" that Tesla Raj is trying to make a profit off of. Kudos!! Will be printing and installing these ASAP.

Thank you for this, although we haven't had the model 3 released in the uk yet, this will be handy when we do :)
Excellent work

Hi Jon: It's really awesome of you to share your Tesla items for free with the community. I've followed you on YouTube for a while and I learned so much about how the systems work in my Model 3. I haven't seen much from you in quite a while, so I was really excited to see this product, because there have been so many Model 3 break-ins in the San Francisco Bay Area. I think that Tesla is coming out with a motion/tilt/and something else, add on to the alarm. It's available for the Model S now, $350.00 installed. Thieves have figured out, that in the Model 3, how easy it is to break the rear quarter panel window and fold down the seat. If there's something in the trunk, just quickly break in, set off the alarm and grab what's in the trunk.

Thank you for making this! I suppose it should be printed with PETG or ABS to withstand warm days in the car right?

Yes, I agree. I've heard of people having trouble with PLA printed parts in hot cars.

Great idea Jon and Ricky!