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Contemplating a Birch Folding Bike Purchase: Wise Investment or Regrettable Decision?

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Contemplating a Birch Folding Bike Purchase: Wise Investment or Regrettable Decision?

Old 02-17-24, 03:40 AM
  #126  
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Originally Posted by Jipe
The steerer tube is short, not longer than the one of a classic fork (it goes only till the folding hinge) and its a one piece machined item with thick walls that integrate the lower part of the stem hinge (the hinge is not soldered on a tube like for many folding bike stems) same for the upper part of the stem, also one piece machined item stem hinge+stem tube.

The design is identical to a Aheadset fork with two thick clamp bolt (on the side of the fork near the fork folding release lever) and one bolt in the classic Aheadset cap to adjust the bearing preload.

There was never any failure reported on the Birdy stem.

The Aheadset type of fork+stem mounting is the most used nowadays in the bicycle industry.
I don't think any folding stems have the tube soldered to the base. My old tapered steel one is welded to the base (and a very nice weld I might add), the newer aluminum Dahon stems, if I recall, are forged one-piece, a nice design, though it takes serious tooling to do that.

If the steering tube has no issues with breaking, R&M should not make people replace them after a couple years, to have the full warranty. Yes? I mean, if no actual problem, believe me that this unnecessarily dings their reputation. Just doesn't make sense.

"Machined" tube, if lathe-turned on the outside, that can contribute to premature fatigue failure, even tiny circumferential grooves. A drawn tube there or very fine finish, is called for a tube under bending. Depends on the notch-sensitivity of the material.

The Aheadset design was a big advance, in my opinion, so much easier to adjust headset, without danger of brinelling the cups, so easy to do on older designs with 32mm(?) wrench.

Last edited by Duragrouch; 02-17-24 at 03:46 AM.
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Old 02-17-24, 04:34 AM
  #127  
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Its a forged one piece with the steerer and lower part of the hinge for the lower part of the stem, also forged one piece for the upper part of the hinge + stem tube.

On the not height adjustable, the forget one piece top part of the stem integrate the handlebar clamp, on the height adjustable, there is another smaller diameter piece that slides into the upper part of the stem.
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Old 02-17-24, 04:39 AM
  #128  
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Originally Posted by Jipe
Its a forged one piece with the steerer and lower part of the hinge for the lower part of the stem, also forged one piece for the upper part of the hinge + stem tube.

On the not height adjustable, the forget one piece top part of the stem integrate the handlebar clamp, on the height adjustable, there is another smaller diameter piece that slides into the upper part of the stem.
Forged is good! (if truly forged, and not cast) Excellent metal grain structure, residual compressive stresses on surface. Forging will often allow use of a less expensive raw material. I accomplished the same thing with swaging/drawing on one of my professional designs.
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