Dahon Handleposts-Who can explain the Hinge Clamp?
(Note: This is a repeat of a portion of my last post in the "Dahon chop shop (bars)" thread, which has not had any follow up since yesterday. The post dealt with a couple of issues but ended with several questions relating to the Dahon handlepost. I would like to understand this critical part of the Dahon folder, so I am starting a new thread on the subject.)
I have a late model Dahon Boardwalk with a "Revolve" (I think) handlepost. The handlepost is simply a long riser and stem. As all Dahon users would know, the handlepost has a large hinge just above where it attaches to the bike's fork. The hinge allows the post to be folded about 180 degrees, from a nearly straight up position to a nearly straight down position. Along with the main frame hinge, the folding handlepost is at the heart of what makes the Dahon a folding bike.
When the handlepost is in the "up" or riding position, it is held snuggly in place by a multipiece clamp device. For reasons I can't fully explain, I am not thrilled with the hinge clamp design. What bothers me, I guess, is that the clamp does not make use of a “positive” interlocking system, but, rather, as best as I can tell, a few small metal rods that effectively push the handlepost closed and hold it closed using compressive force (via the small rods). There is a plastic safety catch which prevents the clamp from opening, but the actual stresses are being borne, it seems to me, by some rather small parts.
Here are some questions: I’d love to hear from anyone who has some background knowledge on the subject.
- Are all of the current (say, 2004 and 2005) Dahon handlepost hinge clamps designed in essentially the same way?
- If not, does the clamp technology improve or become more robust on more expensive models?
- Can anyone list the different current models of handlepost?
- Does anyone know why the hinge clamp is designed this way? Would it not be better to have some sort of interlocking device, such as a claw or hook that grabs a notch or a bar, rather than a collection of small push rods?
- Finally, in order to reduce the reach of the bike (i.e., the horizontal distance between the handlebar and the saddle) by about 1 inch., I have loosened the main binder bolt, rotated the handlepost 180 degrees in the steerer tube and retightened the binder bolt. This means that the handlepost now folds forward to the right side of the bike, rather than back to the left side of the bike. Is this OK? Is stress raised on the hinge clamp?
(By the way, I have observed that some Dahon handlepost models allow for an adjustable stem height and use a fairly standard quick-release type clamp to tighten the stem. This part of the design is not the focus of my concern.)
Any thoughts or insight would be appreciated. Thanks.
ok let me give it a shot
the hinge relies on a couple things . namely the constant pressure against the teflon slider. The handlebar folding is essentially the same on all models. It has been improved over the last years, as it is much stiffer on newer models
No problem I know of to turn it around.
The two hinges are adustable and can withstand a lot of static load ( they dont hold the full weight ofg the handlebar, but pressure them onto a flat surface ...
notch would have a lot of wear and tear, and would become sloppy
Thanks to brakemeister and James H. for following up on my first post in this thread. I realize that this subject is a bit arcane when compared to the topics covered in the more popular threads, but, as I see it, if you are talking about folding bikes, you are talking about hinges and clamps. Moreover, unlike handlebar type, gearing, tire size and so on, it's quite literally a life-or-death topic.
Brakemeister's comments regarding wear and tear on a "hook" based hinge clamp were duly noted, and he seems to make a good point. But I went back and looked at the Dahon clamp and I am still amazed that a single steel rod, perhaps 3 to 5 mm in diameter (it varies), carries all of the stress of the handlepost at the hinge.
Regarding James' suggestion, I have never consulted the Dahon web site for technical information. Is it simply a question of sending an e-mail inquiry?
go to tech and post your question there, usually a dahon person ( like Josh , son of the founder Dr. Dahon ) will answer pretty quick ... he usually waits a little while and looks if somebody else can give a good reply. If its a bad reply or nothing happens he will chime in ...