DrinkSomeWater

Hello folks,

I've owned a Dahon Speed Uno for a couple of years and I ride it very casually... One problem that I noticed is that after riding it for 1, 2 hours, the hinge mechanism becomes noticeably looser. I can't notice anything while riding, but once I fold and unfold it again, it doesn't feel nowhere as 'snappy' as it originally was. So before each ride I make sure to adjust it properly (just like the manual suggests, or the dahon youtube videos), but that doesn't seem quite right to me.
Is there anything I can do to stabilize it a bit?
Thanks!

wesgreen

I would recommend you stop riding it, and take it to a shop that sells Dahon bikes.

seat_boy

I had to add some loctite to the adjuster on my Dahon to keep it from working loose.

tomtomtom123

Did you tighten the Phillips screw at the end of the adjustment nut? It can also serve as a kind of lock if it's tight, but light loctite between the nut and the main bolt will probably also help. Before adjusting, you're supposed to loosen the Phillips screw. After adjusting you're supposed to tighten the Phillips screw.

DrinkSomeWater

I see, I've never worked with loctite before. Should I pull everything apart before applying or just loosen it up a bit, apply, tighten it?

DrinkSomeWater

I tried, but the nut seems to rotate along with the Phillips screw, and if I tighten it too much it becomes really difficult to close the hinge. Should I try to spin both at the same time to see if they separate?

tomtomtom123

Well, if you're just spinning the screw without holding the nut, then they'll both spin together. You'll need to use a wrench to hold the nut while turning the screw with a screwdriver. You adjust the tightness of the hinge by first loosening the screw from the nut, turning the nut a little bit, hold the nut with a wrench to prevent the nut from spinning, then tighten the screw with a screwdriver.

If you allow the nut to spin with the screw while you're trying to tighten the screw, then of course you'll make the hinge tighter, because you're allowing the nut to tighten against the main latch bolt. Then you'll never get a reference point to precisely adjust the tightness of the hinge.

DrinkSomeWater

Right, I was a bit confused about how this mechanism works. I spent some time with it yesterday and now I have a better grasp of it.
I managed to adjust it to something that feels 'just right' but we'll have to see if that'll hold up after going up for a ride. If not, loctite it is... Thanks!

DrinkSomeWater

Hey folks, just wanted to follow up in case someone is having the same issue:

No matter how well I'd adjust it, it'll always come loose after a longer ride. So I pulled apart the adjustment screws, cleaned them up, applied some blue loctite on them and adjusted them until they felt firm but not too tight.
I've then taken the bike for a few rides and it stays firm. Sometimes it makes some noise while riding, which I imagine is the two ends of the fold rubbing each other. Probably unavoidable I guess...
Thanks everyone!

sweeks

Try rubbing some canning wax (paraffin) or a candle on the frame ends where they meet. I carry a small piece of paraffin wax with me for the occasional squeak. This assumes you have the frame latch correctly adjusted.

Fentuz

by the way when people say loctite, go for loctite 243 (or blue threadlocker) not superglue which is made under loctite brand by ankle. I prefer 243 to 242 because it is oil resistant.
270 will lock very but is difficult to undo
Avoid 648 which has to by burned to be removed

Also, depending of geography, you may find equivalent permabond product easier to source.

Fentuz

It sounds you get micromotion. do you get galling marks on the mating faces on the hinge where they come into compression?
You could try a grease like the parafin suggestion to see if it cures it. I did and it cured but it came back as the grease went. As a permanent fix, I stuck a piece of motorsport anti squeak shim (goes behind the ceramic brake pad and caliper piston). It's made by 3m (anti squeal shim on ebay).
The shim is on one face on the hinge and once under compression, it shapes itself in between the faces and absorb the micromotion.

sweeks

It's an "over-center" mechanism, which means that once clamped, any "push-back" from the clamped structure has the effect of tightening the clamping force rather than loosening it. Properly adjusted, it's very stable... a good thing for a frame latch. See Over-Center Mechanism for some images.
The hexagonal part ("rod") of the frame latch mechanism has a small threaded hole in one end near the front part of the frame joint, and a larger male threaded end which adjusts the clamping force by changing the effective length of the rod. The small phillips-headed screw serves only to hold the rod in place. It should *not* be tight enough to prevent the rod from turning. Ideally, it bottoms out in the hole and is tight, but is slightly loose on the pivot shaft in the frame, allowing the rod to turn freely. The rod's male end rotates in a pivot shaft in the latch lever. Rotating the rod adjusts the compressive load on the rod, which allows optimization of the clamping force. A little LokTite on the phillips screw helps to keep the screw from coming loose in the rod; LokTite on the male threaded end of the rod keeps the latch adjustment stable.
I hope this makes sense.

wesgreen

Sweeks, that is a beautiful explanation and description.

sweeks

Thanks! I've had enough experience with those latches, so it's good to be able to help others. :-)