Gentlemen: On envious consideration of aesthetically pleasing and clearly ergonomically sound handlebar layout photographs that Bill, Dave and George have published (what do we say, Jags, we say, Class!), I've decided it would be silly to sprout a T-bar from my bike's handlebars, that the smart, tidy thing to do will be to integrate the two mounts. Examination of the Agu bike mount (not Altura as I first reported, sorry) shows that it would be a simple matter to attach a mounting for the pedelec computer on the handlebar bag-mounting's two screws for tightening the clamps to the handlebar. This piggyback mounting could be manufactured from thin aluminium (American aluminum) plate and would require only two further holes to take the computer without its detachable mount (the separate U-shape mounting being the component causing the problem). The flat plate could be bent for either stiffness or clearance if necessary, though clearance won't be a problem; I might bend it anyway for viewing angle. I in fact have a small sheet of 1.2mm ali on my desk permanently, because it is the sort of bracket often required in my other hobby, high voltage thermionic tube audio amplifiers; in case more stiffness is required I have 1/4in ali sheet too, and mild steel strap about half an inch wide. (I also use the ali for stiffening the leather jackets I make for my homemade sketchbooks.)
Additional considerations:
-- I've had a good look at a Minoura Spacebar I have already. This is a piece of sh1t whose designer never owned a bike and who was additionally asleep on the job: it tightens on the handbar by a thin user-bent strap and no-one I know with one ever managed to mount it securely. But the significant thing about it today is that mine is dented and the crossbar skewed on its mount. Whatever was mounted on it -- my iPhone which not only valuable in itself but which I don't want to lose because the newer ones are plastic rather than aluminium, and grotesquely larger -- could have been trashed when the T-bar was dented if it was firmly attached... (Actually my iPhone is so toughly encased that I sometimes throw it against the wall to demonstrate that the D30 in its leather case works as well for a phone as for the battle tanks for which it was first invented.) What trashed the Spacebar itself was a fall I took when on a very steep downhill at over 50kph the front tyre suddenly went flat and the front wheel folded in under me, throwing me over the bars. (It was such a spectacular accident that all three the motorists behind me stopped and came running. Not a mark on me except for mild bruising... Go figure.)
-- The pedelec computer in itself isn't valuable (about 65 dollars in China, call it a hundred euro landed) but if it is trashed my bike could be off the road for weeks while it arrives; my bike is a very valuable health and social resource to me. So the extra protection that the handlebar bag will provide by rising about the computer (easily arrange as the bag mount swivels vertically at two points) is worth having. (This has also thrown up the consideration that it might be smart to have a spare pedelec computer because it is already prewired and plugging it in and tiewrapping the wires is a ten munute job.)
-- Aesthetics are important to me as an artist, quite apart from the competitive aspect, or even just not embarrassing my friends on the forum or my local pedal pals.
-- There is no cycling-functional need for the handlebar bag; my longest ride these days is less than 25miles, round trip; it is rare for me to be as much as two hours from home, so there is no need for snacks or whatever tourers carry in their handlebar bag. The sequence for considering fitting the handlebar bag is that I bought a bigger motor, then a bigger battery which wouldn't fit on the downtube, then I fitted an old rack top bag into which the battery fits, then the handlebar bag I was using ripped and everything in it went into the side pockets of the racktop bag -- everything that is but the surplus wiring length of the pedelec control system. So the handlebar bag is required only to hide the surplus wires. No, I can't shorten the wires. I solder really well, but those wires are pretty fine and the main trunk is a complicated multicore. I don't fancy finding an induced current send false instructions in it, or sorting even a simple mistake. The surplus wires aren't even glaringly obvious, being hidden under the dry bag for my iPhone, which is also my heart rate monitor, so always on the bike when I'm there.
So, for the time being, I shall first do without the handlebar bag to see if I miss it, and if I do, I shall make a piggyback mount for the pedelec computer to sit on top of the handlebar mount.
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WHAT ABOUT THE WIRES THAT STILL NEED HIDING? WHERE DO THEY GO WITHOUT A HANDLEBAR BAG?
Simple. I'll just cut a cole in the head tube and stuff them in there. (Just testing if you're paying attention!)
It is actually simple. I'll cut a short piece of polytube, string the wires back and forth through there, and tie up the piece of polytube to the handlebar out of sight under the pedelec computer or the dry bag for the iPhone/heart rate monitor. Alternatively, I have some spiral ducting that I used to tidy the wiring on my Trek Smover (full-auto Di2); it's grey to suit the silver and blue Trek but I can paint it black to suit the other peripherals on my Kranich.
I'll post a photo when it is done, though it may take while to arrive there.
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BTW, anyone looking into handlebar brackets/T-bars, beware that you know what you're buying. Many of the brackets/T-bars have one end handlebar size and the other 22mm, which is not good if you want to mount one end to the handlebars and to the other end another handlebar-sized mount, as in the case of my handlebar bag mounting.
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Thanks you once more for your help, gentlemen. This sort of problem is solved so much faster with some brains on the job.