Snapped off the rear triangle hinge bolt (Brompton)
08-15-19, 08:29 PM
#26
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And you are a brave and wise man by not doing so. The construction is as follows:
- the rear frame is sitting on this steel spindle, so the load goes onto that spindle, not onto the bolts.
- between the rear frame and the main frame there sit slim nylon shims on each side
- the bolts are just there to keep the rear frame on the spindle, very much like the nuts on a bike wheel's axle. They press from the side and do not get any vertical load. Those bolts are conical and they are glued in.
- the rear frame is sitting on this steel spindle, so the load goes onto that spindle, not onto the bolts.
- between the rear frame and the main frame there sit slim nylon shims on each side
- the bolts are just there to keep the rear frame on the spindle, very much like the nuts on a bike wheel's axle. They press from the side and do not get any vertical load. Those bolts are conical and they are glued in.
- The rear frame has no concave 'slot' to hold the spindle. It's FLAT. Nothing supports the spindle on the rear frame side.
- The bolts are NOT just there to keep the rear frame on. They should be tightened to make enough friction to support the load.
- If the bolts become loose, the spindle bolts have to carry 100% of the load. I call this a VERY bad design.
- Brompton prevents this by gluing the spindle bolts to the spindle, which makes the disassembly a major pain.
- Modern bikes since 1990's have pivots with replaceable sealed bearings, proper large diameter spindle and bolts.
