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@Brommers
The Brompton of Titaniuminess has been providing sterling service on my commute, the only real problem being its tendency to snap rear spokes. I think it's a combination of teeny rims, a rather chunky hub, the resulting spoke angle, and using CX-Rays in a rather challenging setting. They've all snapped at the nipple not at the J-bend, which suggests that it's the spoke angle where the spokes go into the rim which is the problem.
Naturally, the easiest way to solve this is to build a new wheel. And having decided that I definitely, absolutely had to have 5 gears to get me up and down the Cols and Massifs of London's famous London, the new one's fixed.
But there is a good reason for this, because it is a truth universally acknowledged* that every folding bike is deficient in not having a power meter. After all, if you didn't log it then it didn't happen, but if you don't have power data then it doesn't matter if it happened or not **.
So the new wheel is based on this:
a very reasonably priced 28h Powertap SL+ track hub I got off eBay. I've modified it to reduce the OLN from 120mm down to 112mm using custom end caps like this:
which is just some 19mm A/F stainless hex bar with an M14x1.5 thread down the middle and some machining on either end. Built up into a wheel with some 16" Velocity Aeroheat rims and some custom-length 13g Sapim Strong spokes (hopefully no more snapped spokes) it comes in at a relatively chunky 956g without rim tape:
However, that's lighter than the 5 speed hub by itself, so the bike is lighter than it was. Other than having to machine up a little ali top-hat to keep the chain tensioner in place, it all fitted together reasonably easily.
It works, but at the moment there's too much slack for the chain tensioner to take up when the bike's unfolded for it to work well fixed. However, I reckon that's fixable with some new parts. One of which will be a 14t sprocket to replace the 15t one that's fitted at the moment, because (not surprisingly) a 50/15 gear is a bit too spiny with 16" rims even just for pottering around town.
Once I get the new parts (new chain tensioner, pulley wheels, 14t sprocket and chain) I'll try and get it running better. But, like I said, it works...
/* this is not true
/** also not true