What kind of Dahon hinge do I have?
 

I have a Dahon Mariner D8 40th Anniversary Edition. I am not sure if this is just a paint job or it's different in some way, being 40th anniversary edition.
My frame hinge has play. The hinge is with a latch. There is a screw underneath the latch, with which the latch can be adjusted. Until now, this has been the only way I ever adjusted the frame hinge, and it worked. I extend the screw, it pushes the latch, the latch latches tighter, the frame is sturdier. But now it no longer works. I don't see any other adjustments here.

I have not found a single manual, or even a picture when using google image search, of this specific hinge type. AI do es not know anything, and all of the websites either Dahon or resellers show this specific bike in this specific edition with a different hinge.

Can someone help me identify the hinge?
Or even further, point me to instructions how to adjust it?
There appears to be empty screw hole on the latch lever on the right, not sure what is it for or should it be empty.

https://cimg4.ibsrv.net/gimg/bikefor...ad5db7aecd.jpg
What us this hinge?

That's a very new Mariner, that's the latest version of their hinge, with the lever aft when closed. Earlier versions of that hinge have the lever forward, and that is my Dahon hinge, circa 2005 I think. So I don't know the internals on your hinge.

On mine, I did two things to improve the hinge.

1) The screw adjusting barrel had nothing to lock it in place; I added a thin nut on the male threaded portion, to lock the adjusting barrel in place. Otherwise I was adjusting monthly.

2) I improvised a Deltech style cable, this changes the forces at the hinge from bending, to compression shear, less stress on hinge, stays tighter longer. Does your Mariner have a Deltech cable? Dahon has been running hot and cold on Deltech, first on, then off.

Since the above improvements, I haven't needed to adjust my hinge in almost 3 years with a lot of riding, not a touch of looseness.

I'll look for feedback on the above, before more info.

Yes, you can see the deltc right there in the bottom right of the image.
I have generally not needed to adjust often. I have the bike for 1 year now.
But, I do remember it was only the screw underneath I adjusted, but this no longer works.

This now, coupled with other issues I had (having to adjust brakes and index speeds a couple of times, with like only 1500km, and chain being REALLY prone to rust), makes me feel I have been duped. My cheaper old chinese ebike did not require 10% of the maintenance :/

Would you be able to give more specific advice if I posted a photo from the inside?
Also, what is the name of the hinge? I imagine with a name I could maybe find a manual.

Typically, the side lever hinge for Dahon was called Vicegrip, because it uses compound leverage like Vicegrip locking pliers.

Dahon Launch D8 with bottom lever, used Jaws hinge (fine teeth visible from the sides when closed), and later New Jaws Hinge (larger tapered teeth, hidden inside hinge when closed).

A pic of hinge open would be good.

Yeah I thought that was a Deltech cable, but wasn't sure it wasn't a brake cable. With Deltech, properly adjusted, hinge adjustment should be infrequent, unless it's coming loose and needs a locknut like I put on mine.

That Deltech needs to be tight to work. Check manual for adjustment procedure.

Thank you!
I will take some photos later.

I was not even aware I need to adjust the deltech cable, I will make sure to do that as well. The bike was serviced in a bike shop recently, but I guess the guy only checked brakes and indexed the speeds, and did not bother with learning anything about Dahon peculiarities (which is understandable).

Yeah, Deltech needs to be tight when unfolded to do its job, however, too tight could also fatigue the cable mounts at the welds. Dahon was full-steam with Deltech going on everything, then suddenly gone from the aluminum bikes but still present on steel frames, and, a newer Deltec bike from Japan connected to a ring mount at the fork head, eliminating the forward weld mount; Both indicate to me that they had some weld fatigue issues, especially with aluminum, which is more prone to fatigue. They should have done it like the "Add-On Deltech" they advertised which never showed up, which is two outside ring mounts around the bottom head tube and bottom bracket shell.

Japan market pic:

https://cimg2.ibsrv.net/gimg/bikefor...fa7522645e.jpg

Or, like my bike, a loop of ultra-low-stretch line like Kevlar (aramid) or Spectra (UHMWPE); That skinny line below will lift my car. Before securing ends:

https://cimg4.ibsrv.net/gimg/bikefor...75c4bd3f05.jpg

I took a few photos.
This is the frame hinge from the inside:
https://cimg8.ibsrv.net/gimg/bikefor...9e29719864.png
Dahon Mariner D8 2024 frame hinge

An odd thing happened: while taking the photo, I randomly turned the screw, and the hinge is now seemingly.. Fine? I don't get it. Twice I turned the screw all the way one way, then tightened it in small increments, and at every point, the hinge had a gap when latch was clamped.
Now all of a sudden it works..

But also, just for future reference, posting images on how Deltec on this model is attached. I found these attachments odd from the very beginning, as the attachments points themselves are obviously weakest points.
So this is Dahon Mariner D8, but I have Shimano gears and derailleur, and my seat is sports seat and not the one usually depicted, and the tyres are not what is usually listed, and there is Deltec on this one, and the hinge is as you say newer. I have not been able to find this exact configurations anywhere. And I'm sure bikeshop swapped some parts. It might have been a returned bike or something, but they did not disclose this.

https://cimg4.ibsrv.net/gimg/bikefor...a3d64d548f.png
https://cimg5.ibsrv.net/gimg/bikefor...13fb216630.png

That hinge is nothing like their other hinges. The toggle linkage must be in the latch handle outside of photo view, I'd like to see that if you can take a pic of the handle. But basically, same concept, the latch goes "over center" when closing, peak force then slightly less as the handle goes against the frame. Unless not, unless they designed it so constantly increasing pressure, with a secondary latch to hold it closed. The latter might be better, as the over-center latches, to be tight, are then difficult to pull the lever to open, I pry mine open with plastic tent stake with a chisel point, easier than injuring my fingertips trying to pull the latch open by the small tab on the old style latch.

Notice: Nothing holding that latch adjustment bolt in place, that means it can move slowly over time. With the spring there, no room for a locking nut.

The New Jaws hinge seems to be an improvement, but haven't used one yet. Dahon USA showed specs for their Launch D8s in stock as having New Jaws hinge, which is wrong, they are the old original Jaws hinge. Just looked at their website, they still have that wrong, spec says new, bike shows old.

Little hole on the latch
 

I just got a D8 delivered and yeah, I'm a bit annoyed that the folding mech isn't described anywhere, not even in the user manual.
On my bike there's a tiny grub screw in that hole. It seems to control how much the latch can travel once it clicks onto the frame. Probably the ideal distance is zero, but if it's screwed in too much it won't click over the frame latch. I've done a fair bit of adjustment on this and on the big screw but I still need to carry a set of hex keys at all times. I'm a bit unhappy about all of this.

Interesting re-design.
Seems to have more surface area for contact. Tho it seems to only make contact on the right side.
Do you get any creaking yet?

I noticed that too. My engineering eye says... the vertical male/female mating ridge is further from the hinge pin than before, and longer contact length, thus will be able to resist torsional forces through the hinge better, and stay tighter, than their traditional side-hinge joint. Jaws, and then New Jaws, was supposed to be even better, as the hinge pin was only to hold the two frame halves together when folding, so when unfolded, all forces go through the tapered jaw teeth (external on Jaws and internal on New Jaws). I don't know if they have abandoned New Jaws, I think it's still on their premium models, but this new hinge on the Mariner appears from photos to be an improvement, but I don't know for sure. It's also aluminum, which is softer and wears faster than the steel hinge on my old Dahon Speed. Oh, but it also has a Deltech cable, that will reduce bending stress on the hinge and improve durability a bunch. My improvised deltech did so on my bike. Deltech does not, itself, take any torsional load, but by tightening the hinge (it does by loading in compression shear), it improves torsional stiffness there, rock solid when standing climbing.

No creaking so for. During the time I made the post, it's working fine.
Very stable, no flexing.