southpier

all I can think of is "des-dromonic" but I know it isn't correct.

it's a rear derailleur, downtube shifting system with two cables. there is pull in the up & down shift, so it is probably required the rear derailleur be paired with it.

any help appreciated.

thumpism 

Sounds like one version of the Shimano Positron but they were all stem shifters, I believe.

Kuromori

There were a number of pull-pull twin cable systems, so there’s no specific name they go by.

Kuromori

Shimano did in fact make a downtube version of the early positron shifter, although it is rarer. They also had a twist shifter for the Lark-W.

T-Mar

The OP is thinking of desmodronic. It is most commonly used to describe an internal combustion engine whereby the valves are both opened and closed by the camshaft action, not relying on springs for the latter. In the early days, valve springs were unreliable, particularly at high RPM, so desmodronic valve systems were the choice in high performance engines. Bicycles shift systems whereby the cable(s) acts in a pull mode for both the up shift and down shift can also considered desmodronic, though dual cable or pull-pull is probably more common terminology.

qcpmsame 

Think Ducati, Best example of a desmodromic head I could come up with. Wikipedia uses the definition, (paraphrased) having controls to actuate a device in both directions of its action.

Bill

Kuromori

Calling that desmodromic seems like a real stretch to me, to make something commonplace sound exotic. Really the only place I’ve heard the term used is engine valves(and trying to make something pedestrian seem exotic). Would you really call window blinds desmodromic because there’s one cord to open then and another to close them?

edit: After doing a little more research French people really like the word desmodromique, it is not common in English language patents though. Nor does it seem to imply the Wikipedia definition at the top that says different controls for different directions. It just means no float or springs to prevent float.

southpier

yes; thank you. I first was exposed to this magic via The Golden Age of Handbuilt Bicycles

by Jan Heine. ( of course I don't have the page number!)

TenGrainBread 

You could say this about any technical/engineering term. The purpose of having a word for it is so that you don't have to say "A mechanical system actuated by a different controller for each state" every time you want to refer to it.

It's nice to be able to say "threadless headset" instead of "A steering bearing system that uses a compression cap and clamp to adjust bearing preload rather than a threaded nut".

Darth Lefty 

Not exotic, just not English. Sometimes someone else gets there first. Aviation is full of French words (fuselage, aileron). Maserati Quattroporte sounds fancy too, doesn’t it? Just feel lucky it didn’t come from German. It would be called a pushpull-lever-thing

Kuromori

Except in English it’s usually just known as pull-pull controls, desmodromic doesn’t actually seem to mean that and pull-pull is actually more specific.

Kuromori

That’s really not how desmodromique is used in historical patents. It’s not a thing or an invention, it’s an adjective describing not having an excess of degrees of freedom in the system (exact constraint)

Darth Lefty 

Yeah, in a Ducati it’s more push-push. I get the controlled both directions sense but can’t think of an equivalent English phrase off the top of my head

squirtdad

so you have dromedary camels and desmondronic llamas?

madpogue 

I'm tempted to open up a steeply-banked short track, and stage races going in both directions at the same time, and call it the "Desmodrome".

tricky 

The White Industries derailleur is also a pull pull derailleur. https://dirtragmag.com/articles/blas...ailleur-system

Dan Burkhart 

That's how the military would describe it if they were looking for tenders. Then they would end up paying $35,000.00 for a $35.00 part.

ksryder

Seems like the ship has sailed on the "bike parts should have names that make sense" boat. Bottom bracket -- not a bracket. Clipless pedals for a system that unmistakably involves clips? Your saddle is attached to a seat post? Ad infinitum.

scarlson 

Contemporary examples include Rohloff and NuVinci.

I have a twin-cable Le Cyclo rear derailleur on my Jack Taylor. It is uniquely finicky to set up, but works much better than I thought it was going to, when I was going through rebuilding it. Granted that's in a stand. The real world may have other things to say.

tricky 

You mentioning Rohloff reminded me of the Pinion Gear Box and made me wonder if it's a dual cable system. It is indeed. Not sure if it's pull-pull. https://pinion.eu/en/accessories-2018/#module-id-11

Kuromori

It's not so much that it's technically wrong, but I think the label of desmodromique is not historical, nor is is even a particularly more concise way expressing the specific mechanism in question. It's not the proper word, it's just a suitable suitable and to me, pointlessly exotic (gruppo) word. The usage appears to be modern and Ducati marketing really does play it up to be exotic. Even doing the patent search, it seems where desmodromic comes up a lot is Belgian (in French) patents, like someone once dodged a patent by including a desmodromic mechanism somewhere.

Darth Lefty 

My employer is one of the companies running up those tabs. True story, one of our suppliers told us SpaceX came to them and asked for the same kind of parts they sell us, except without all the testing and certification. Then SpaceX had a big embarrassing launch failure. Sometimes you trust but verify.

southpier

yuppers. and heaven forbid we have any references or influence from outside of our homeland.

now what's the word for . . . .xenophobic?

Kuromori

Demosdromic is pseudo-latin. It's not about xenophobia, it's about playing up Euro-flair, even without any obvious historical basis (say derailer vs derailleur), just like people who think Asian bikes bad, since you seem to be trying to imply something.

If you take a look at the old cyclo catalog it literally just says "single wire" and "double wire" but apparently me not attaching exotic sounding words to make things sound fancy in the modern day to things is being xenophobic. Maybe to be culturally sensitive, I should ignore the plain English name for STIs and start calling them "duarukontoroorurebaa" like they call them in Japanese or better yet, use a pseudo-Japanese name for them that was never officially used like "burifutaa" but someone used it somewhere because that's obviously less xenophobic.

T-Mar

Yes, I was going to mention Ducati but I wasn't sure if they still used the desmodromic valves or if the reference would be foreign to the membership. Back in the early 1980s I almost bought an early 1960s Ducati Diana (250cc single), Instead, I acquired a Cinelli of similar vintage and a relatively modern Mariposa. Both were nice bicycles but I disposed of them within about a year and I've always wondered if the Diana would have been a better acquisition.