BruceMetras

Even though I like my 2009 Dahon Mu Uno a lot, I can never just leave well enough alone.. the original platform is minimalist and highly functional.. single speed, coaster brake, no cables at all to the rear.. horizontal drop outs, narrower rear spacing than most Dahons at 120mm .. the bike is stiff, folds easily, folds narrow and rolls when folded if you want, as the rear wheels are almost parallel to each other when the magnets clamp down.. stock, the gearing is about 65".. this covers a surprising amount of territory..

So what options are out there if someone wants to tweak the drivetrain, while maintaining the integrity of the original platform .. a Schlumpf drive would work, but the 1.65:1 overdrive is a pretty large step (as seen on the 2 speed Stridas). Moulton have a new model (the 50) with a Sachs Duomatic kickback 2speed + a Schlumpf Speed Drive .. after working out the ratios and how I would need to shift to get them, I passed on that thought and was considering just the Duomatic.. after finding that Sachs produced a somewhat rare Automatic Duomatic with coaster brake, and that I could get a NOS unit from a German supplier, I decided that was the route I would try.. since the Automatics are NOS with really old grease from the 60's, the supplier insists that they should be disassembled, cleaned of old grease, and re-lubed.. so that's what I did.. since I like 451 wheels more than 406 on un-suspended bikes, I laced the Automatic into an ALEX R390 451.. and laced up a matching wheel for the front.

How's it work in practice? Well, in a word, terrific! .. the Automatic has the same 1.36:1 ratio as the kickback Duomatic, so I have a 54" low and a 74" high.. pretty much perfect.. I get up the hills that I couldn't with the stock Uno and my comfortable cruising speed is up a few mphs.. 100rpm gets me around 21mph.. the hub shifts by centrifugal force.. the shift point is adjustable by varying spring tension inside the hub .. as stock it shifted at around 8 to 9 mph.. too low for my project.. I changed the shift point to just over 13mph (at around 80 rpm cadence).. this works out great.. the shift up is positive and fast .. the harder you pedal, the faster the shift.. if you have pressure on the pedals and are below the shift point (as in standing going uphill) the Automatic will not downshift until you release the pressure.. I can't believe how good this hub is.. I hope it lasts a long time.. here's a couple of shots.

SesameCrunch

Bruce:

You are the Master! This looks like a fantastic setup! Simply elegant, yet much more functional. Looks like a million dollars with the sleek, uncluttered lines. The Auto Duo sounds fantastic (how much do they run?) The 451 wheels look great too.

Wow. Dahon ought to make a model like this. Bet they could get lots of money for it.

Dynocoaster 

Very nice.

HGR3inOK

I've been told that no bike is perfect. This must be as close as it gets.

Diode100

hi, this is exactly what i have been thinking about for some time. I rode the Moulton two speed a few years ago at Bradfordunpon Avon, very impressive, but it was about 2,000 pounds even then.

Any chance you could let me have the contact details of the German supplier for the hub?

chucky

I'm in love

brakemeister

oh .... my
thats were the spokes were for .... NICE

soooo the suplied front caliper brake works with the new sized wheels ?

Thor

BruceMetras

Thanks all for the interest.. this project really opened my eyes to how really well built some of the older hubs are, while still being fully contemporary .. I like the Duomatic kickback hubs also, but the advantage I see to the Automatic is never having to think about which gear you are in while braking (using coaster brake) ... and when powering up, you don't have to stop pedaling, kickback to another gear, and then press on.. you simply start pedaling harder and faster and the shift just happens, momentum isn't broken .. it'll even shift on the coast as you crest a hill, head down the other side and are at or above the shift point.. anyway, here's the site that I used to obtain a hub... the whole site is a treasure trove for hub gear lovers .. SRAM reportedly still have the Sachs machinery to build this hub.. perhaps a few emails nudging them in that direction could see brand new Automatics being available on the horizon..

https://hubstripping.wordpress.com/

BruceMetras

Haha... Yeah, that's why you were getting two emails a day for a week... "where are my custom cut spokes??" ..

Shameless plug for Thor.... the spokes used both front and rear are Sapiem stong and were not stock sizes and needed to be cut using Thor's Phil machine.. excellent source for custom spokes!

I had to change the Tektro long reach caliper for a Tektro short reach.. definately not enough adjustment available with the long reach units.

SesameCrunch

Wow. I still can't over this bike. Great job!

I'm thinking non-stop about the Automatic hub for my Moulton MK3 restoration. That would be a perfect match. It has an SA8 hub on it now, but a 2 speed coaster would bring it in line with the original design and clean up the looks of the bike.

I'll have to look into the specs of the hub.

Good job again, Bruce. Very innovative.

BruceMetras

Oh boy!! that would seem sensational for your MK3!! .. even better if it's a separable.. can't remember which one you have... the Automatics on the site are 36 hole.. I laced mine to a 24 hole Alex rim .. the spacing is 110mm, so if you have anything close, should work a treat!

Sixty Fiver

Sweet.

akcapbikeforums

Dahon... are you listening?

brakemeister

already send them the link...lol

thor

jdmitch

Wow... nice, nice, nice job.

That hub sounds awesome.

chagzuki

Looks beautiful. The wheels are really elegant. . . so you can't use a V brake with 451 rims?

SesameCrunch

I can see a Limited Edition of this bike by Dahon. They'd had to call it the BruceMetras Special, though.

SesameCrunch

Mine is not a separable. But I still like the clean lines with no brake and gear cables going to the back. Plus the rear triangle does not have braces for rear brake calipers, as the original MK3 used coaster brakes. So, this is perfect.

The rear spacing on the MK3 is 110. I currently have a 36 hole SA8 on a 28 hole rim. The Automatic hubs are 36 holes also, eh? I'll look on the website for the axle diameter in the new hub.

Thanks for the idea. I think I'm going for it!

BruceMetras

There aren't any V-Brake bosses front or rear on the Mu Uno .. originally, there was no front brake .. though once they started being delivered, one was offered as kind of an option in that Dahon includes one in a box, and you get to mount it if you want..

MnHPVA Guy

I don't think any of the production Mk IIIs were.
Not a coaster brake, a cable operated drum. However they were so pathetic I'm sure many were replaced with coasters.

The hub in question was an S3B and was such a total loser that Sturmey Sunrace wouldn't name the new 3 speed fixed gear the SB3 despite the clamor for it to be named after St. Sheldon.

The 3 speed hub itself might have been OK, though I never could get mine working quite right. But the brake was worthless. Raleigh insisted that it fit into a standard diameter shell so they wouldn't need 2 spoke lengths. To complicate it being too small the braking surface was chromed and the seals between the 3 speed and the drum leaked. I brazed V-Brake pivots on my Mk III swing arm and replaced the hub with S5 guts in an alloy AW shell.

It might be worth waiting for the new Sturmey S2C kickback 2 speed coaster. With expected sales of half a million a year I'd be surprised if there wasn't a 28h version for small wheeled bikes. Wonder if the 2nd gear is over or under 1:1.

LittlePixel

I love this - I'd not heard of these hubs before - very intriguing. I just fitted a SA 3 speed onto a fullsize bike with hub brakes (rear is a back-pedal too) and it's so nice for the looks not to have all the cables everywhere. It really suits 451s too - excellent work and nicely documented too...

chagzuki

I've not heard of this type of hub before, is the model you have heavy?

SesameCrunch

I have no shame. Based on this thread, I have ordered a Duo hub from Bruce's dealer for my restored 1970 Moulton MK3. It will be so right for so many reasons (excluding the pocket book).

With the Duo hub, the look will be so much cleaner and original. I will therefore also put the original (non-drop) handlebars back on the bike.

Now, the hardest part will be the 4 year wait for the part to arrive from Germany.

vmaniqui

are you serious about this long wait ? why 4 years ? that long to manufacture the part or that long to scrub all the used bike stores in germany to look for the part ? does the day starts counting now ?

Simple Simon

Well done Bruce, an excellent mod.
and thanks for the info on the gears, ratios and adjustments.