Duragrouch

I don't NEED a frame currently, but would take a free one that could be repaired. But shipping is too expensive these days.

Maybe the 4xxx hinges were press fit and pinned? I don't think I have seen such a hinge.

My dahon speed was loose, EXACTLY as you describe. Thought it was a loose headset (you should check that; fold the stem, unscrew the clamp screws on the lower stem, tighten *just barely snug, overtightening will brinnell (dent) the balls into the headset cups* the big center allen bolt (10mm allen I think), that will take out any headset slack, retighten the outside clamp bolts, put the stem back up, then check frame wiggle again). But my slack turned out to be the frame folding joint, tightening the screw adjuster for a firmer clamp force, worked, but also, putting a small nut on that threaded part to lock the adjuster in place, it was slowly coming loose and needed to adjust monthly. Now, never. In other threads, have you seen my macgyvered "deltech" cable? That may improve things a lot. Let me know.

EDIT: See this thread, my post #24:
https://www.bikeforums.net/folding-b...danger-no.html

CrimsonEclipse

Nah, I just happened to be adjusting the headset and thought that too.
Sitting on the floor, holding the front brake and put my ear near the frame.
Center hinge. <explicative delete>

I remember that thread. Love the bailing wire and chewing gum...

So about the Dahon cable.
[deep breath]
I'm trying to not sound like a jerk.
But the cable is kind of a sign of a bad design in the first place.
Yes, I know that the cable can add strength and stiffness, etc etc, buuuuuut yikes.
How many frames need an after market cable installation?
I wonder how they plan on cable stretch over time?

I'll check the pin.

Thanks RG!

Duragrouch

You're good, no jerkiness taken.

The genuine Dahon Deltech (only OEM now, available as retrofit this summer they say), is set up just like the shrouds on a sailboat; Stainless steel cable with swaged end fittings with threads and nut to adjust.

The Dahon monotube frame with hinge, is "adequate" for the application. I have seen several express that "folding frames are not designed to last forever". Maybe, but I want at least a couple decades. The monobeam itself is plenty strong, but the hinge does not have a wide "spread" so is inherently weaker. Usually to get stronger, you can eliminate the hinge and have a swinging triangle like a Bike Friday, which also allows them to make the Diamond Llama instead of just a monobeam, super stout frame (the basis for their new All-Packa), but it's a messier fold IMO than the Dahon. The Deltech and my rigged improvised replacement, does the same thing, but does not impede folding. On a diamond frame, the lower downtube is loaded in tension and torsion. The cable doesn't improve torsion, but the big monobeam is plenty stiff. But the cable increases the "depth of section" in bending *enormously*, and further, places the hinge in compression and not bending, also a big plus. It may look like a kludge, but is entirely sound in theory. Having said that, the newish Dahon Launch uses what may be a better folding joint, once folded, there is no load on the hinge pin, that only exists to hold the two pieces together when folded. The hinge joint is interlocking teeth, looks good on paper, my only question is whether there will be tiny movement in said over time, resulting in unflat surfaces and non-tightness. We'll see. I think that design, if truly superior, should be implemented across the board. Look closely:






IIRC, Dahon is also claiming max load increase to 300 lbs with Deltech, up from 231 lbs. That's a big increase, which should also increase fatigue life of the frame greatly, at lower loads. Fatigue life is non-linear with respect to load and stress; IIRC, each 10% reduction in stress, doubles fatigue life (and that's a conservative estimate, often it's much more in high cycle fatigue).

CrimsonEclipse

If I may ask:
What would you consider a minimum ground clearance for a rear derailleur?

Duragrouch

For me, absolute minimum, above the tire bead, preferably a bit higher, both when cage vertical, and when on the big cog, even if swung forward, so if the chain drops, it won't be damaged (from a ground hit) when swinging back, or from a flat tire.

Provided the above swing is within tire bead radius, the next issue is chain clearance to tire when on the lowest gear, more of an issue with wider tires; Not a problem with my 1.75s, but crazyguyonabike blog, this was a big problem for him, with a fatter tire, and was running a triple crank on a Bike Friday NWT, a very common setup before wide-range doubles; The inner 'ring overlaps the bottom bracket on most cranks. He still couldn't get by with a wide double, as he needs an extra-low 15 gear inches for climbs on his tours. Notably, he varied his chain length (can't recall if shortened or lengthened) to get his long-cage derailleur out of the dirt on unpaved rides.

Ron Damon

The images that you have posted so far are inappropriate to gauge ground clearance for at least two reasons. One, the bike needs to be standing up with so we can see where exactly the tire contact contacts the ground, where the ground is. Two, it needs to show a gear position where the lower pulley is at its lowest position. This is at the point where the pulley cage is perpendicular to the ground. These images are inapt for the purpose of transparently and effectively showing minimum RD ground clearance. An honest, credible effort in that direction would require posting an image along the lines of this one.


Tire on the ground with pulley cage perpendicular to it, measuring stick for read out

It's not difficult to understand the pusyfooting with the images so far and the great reluctance (and likely embarrassment) to show the real, effective ground clearance of this "solution" several months after the fact and after promises of additional images.

Fentuz

this is what I get with 11-34 T and short cage

CrimsonEclipse

We embarrass you because of your consistent arrogance and rudeness.

Ron Damon

But wait, hadn't you sworn to ignore me? The only embarrassment is that grappling hook contraption, past and present.

CrimsonEclipse

Like clockwork.
At least you stayed calm this time.

Ron Damon

Ok, I take it then that you will not -- quite understandingly, mind you -- post a proper, transparent image of your solution for the channel to accurately gauge its ground clearance. Gotcha.

CrimsonEclipse

THERE'S the tantrum!

How's the bike sales going?

Trakhak

For paved-road riding and (probably) even gravel riding, reduced ground clearance for the rear derailleur is unlikely to be a problem. That said, I rode a Cannondale Beast of the East (26" front wheel, 24" rear wheel) for many years on Maryland single-track trails littered with branches and other debris, and I went through over a dozen rear derailleurs.

I wouldn't have thought that a couple of inches less ground clearance would be a big deal, but I definitely broke more rear derailleurs than any of the guys I rode with.

Duragrouch

Two things are amusing about this. And yes, you are correct.

Regarding derailleur height and threats to it, let me present an analogy; People think that a main battle tank makes one impervious to threats on a battlefield, but it doesn't, it just greatly reduces the number of threats, to only other main battle tanks (or these days, heavy anti-tank weapons). It improves the statistics. Likewise, a slightly lower derailleur increases the number of threats, because the statistical height distribution of said threats, is pyramid-shaped; A little lower, a lot more threats. Sorta like... there are a lot of people who are 6'4", but a whole lot less who are 6'5". Derailleur only a little lower, the numerical threats increase fast.

Second, I wonder about the thinking in designing the Beast of the East? To move the rear tire forward, more under the rider? I know zip about mountain bikes, but I designed off-road military vehicles, and a smaller diameter gives you a worse "cone index", it sinks in more in soft soils, which is a big deal in getting stuck, even a little more dirt piled up in front of the tire, needing to get pushed out of the way for rolling, can get you stuck that much easier. Which helps explain the move to larger tires on mountain bikes, like 29ers (silliest marketing ploy ever, it's just fatter and deeper section tires on 700c rims).

Ron Damon

While we wait for the OP to post transparent images of his enviable, skillfull long-cage RD with 20x1.75" tire solution, I am gonna share a vid that shows that the Shimano XT RD-M8000-GS medium-cage part, nominally rated for 46T max cog, will span a 51T cog or a 11-51T cogset. That's 11-speed so no need for a non-standard hub carrier.


By extension, the Shimano SLX RD-M7000-GS part, rated nominally too for 46T max cog but with even greater total capacity, can be expected to span an 11-speed, 11-51T cogset too. If these two parts sound familiar, that's because I brought them up at this start of this long discussion over a year ago, before the OP went down his regrettable path.

Coupled with a tall tire -- think 2.25" or 2.30" (no, there's no tire rub if you know what you are doing), this is the likely the best way to get 464% range or a 51T max cog on a 20" wheel with a 1x setup and acceptable RD ground clearance. Long-cage on 20" wheels was and still is ill-advised, particularly given that medium-cage solutions exist.

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Ron Damon

...And here's a vid showing, after finessing the chain length a few times, the Shimano RD-M6000-GS part spanning an 11-50T cogset.

Duragrouch

Appreciated. More info is always good.

I'm still nervous about any derailleur that hangs below the rim, even with plenty of clearance due to taller tires, lest the derailleur be damaged from a rear flat tire. However in one of your other posts about the Zee derailleur, I was very impressed, sufficient clearance on your 16" wheel (I don't know if 349 or 305), I only grokked that from the bit of frame color I saw and connected that to one of your bikes you have shown. Which means, on 20", there should be tons of clearance. However I don't recall the largest cog on that setup. The Zee derailleur, (it appears) spring-loading what was previously the B-screw adjustment pivot, is just brilliant, not a huge change but just evolutionary in design advance. The two videos you just posted, appear to have the same feature, the first referred to an "indirect mount", ah, I can see now that it adds an additional pivot point to the derailleur, or, it is using a "hanger extender"(?) to position the derailleur better. I'm still learning on this.

Ron Damon

305, Grouch.

Duragrouch

Yeah that's what I suspected, I know you've raved about the benefits of 305. I just don't like to assume. The bright aqua(?) dropout was easy to tie back to other pics you've posted of the whole bike. So yeah, Zee workable on your 305, it'll fly onto a 406.

Ron Damon

The official FnHon color name is "Blue Chameleon".

Here is the Zee on a 20" wheel with 42-406 tires.

Duragrouch

Oh, there's been on the market for a couple decades I think, some production cars with "chameleon" paint that changes color in sunlight based on the viewing angle, that's awesome if your bike is the same.

Oh yeah, Zee on 406, that's tons of room. It would be a tiny bit lower on mine, because I run 2X 50/34, so on the small cog/ring, the RD needs to be swung fully aft, so will be at its lowest when on a larger cog, but that'll still fit no problem. Thanks!

Ron Damon

The Zee RD-M640-SS doesn't do 2x. 1x only.

Duragrouch

Hmmm, I trust your judgment, but I'm wondering, how does the Zee know? I could see if it doesn't have the total *capacity* to do 2X (with a wide-range 1X cassette), but could not see any other reason. I mean, even with 1X, the chain is not perfectly aligned all the time, so with 2X, I couldn't see a problem with that. ***YEP, looking at Zee specs, 25 tooth capacity, dang, that's like 18 less than my Tourney GS I think; not only would that not work for 2X, it won't work for me on 1X; I need my 11T high so the largest cog I could go would be 36T. That's only 327% range, I need minimum 400%, and a little better would be great. I'm not needing to do any changes right now, but comes the time I do, I'm sure there is a GS-length indirect mount with spring, that can accommodate a bigger cog than max 34 with the Tourney. With a 52 1X ring, I'd need a 46 cog to equal my current low, while keeping my current high on the 11T cog.

As much as I've tried to design around (avoid) going 2X, 1X is a big lift to get 400% on 20"/406. (Unless you have a 9T high cog, then I'm pretty sure it can be done.)

"There ain't no such thing as a free lunch." - Robert Heinlein, The Moon Is a Harsh Mistress, 1966

Duragrouch

Yes, and that's just the tiniest bit closer in ground clearance *in the event of a flat tire* than I would want. Not knocking your setup, I just want a little more "robust" setup. (And by robust (an actual term used in engineering), I don't necessarily mean stronger; In this case, less likely to be a problem when a related part (tire/tube) fails. The design mantra is "no single-point failure".)*** UNLESS the above pic is on 16"? Then that would work on 406.*** (Sorry, you have so many bikes, it's hard to keep them all straight in my mind.) EDIT: Yes, that's the Volare 20", that's what I thought.

I was psyched about the Zee, but understand now why that won't work.

Listen, I'm lucky, I already have a 2X setup on my folder which I just love. If I heavy tour and need a lower-low than 21 gear inches, I will look at options then. I know I can do better than my current 11-30 (original) cassette. At least 34 is possible within the range of my RD, and others have said those ratings are conservative.

But your stuff rocks.

Ron Damon

Another vid with good info about the Shimano XT RD-M8000-GS and Shimano Deore RD-M6000-GS parts with 11-50T and 11-52T cogsets based on actual tests. Spoiler, the latter part is the better of the two.


IOW, the info on how to do this right, without a long-cage RD, was not only provided here, but also has been available elsewhere for years.

I note that the Shimano Deore RD-M6000-GS part costs under $45, less than, say, a Zee RD. Given the quality and versatility on offer, that's where the smart money is.
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