As mentioned in the Grumble thread I'm looking at fitting an electric motor to my Dahon Glide to make my commute a little quicker and/or easier. I'm trying to take the quiet early train into work and cycle home to avoid the busier afternoon trains at the moment. Which is
okay for now as I'm luckily only in the office two/three days a week but once that ramps up I'm not going to find the 27 mile ony-way trip sustainable.
Whilst the Dahon isn't the best bike for that sort of distance I can keep it behind my office door and not trust it to the easily accessible bike sheds.
I was happily looking at front wheel kits when I learnt that the Dahon has a narrow 74mm oln front fork and the majority of kits are for a conventional 100mm fork. But a folding bike kit with a narrow hub won't work as they are geared for 16-20" wheels and I'm running on 24". Simply re-rimming out to 24" is a
bad idea or so I'm told. Unfortunately, a middrive kit won't work either due to the frame geometry around the bottom bracket.
Whilst searching around I did find aftermarket Dahon forks built to 100mm but
of course they only seem to exist for their 20" models and not the 24".
So the current (ha!) plan is to get a fork that will take a 100mm hub and I've a few possible ways I could go about it that I'd like some advice with please. However I go about it I don't want a front end that'll collapse under me!:
- I was thinking I could get the steel version of my current fork and cold set it wider. I've read of this being done on road bikes but usually only from 90/95 mm out to 100. Would going up from 74 to 100mm be too far? It feels too far. (As an aside I actually checked earlier and turns out I actually have a steel fork and not alloy like wot the Dahon site says.)
- I've read of someone using a Tern fork and handlebar post on a Dahon bike, albeit a smaller wheeled model. Blogspot Link
- I have found a Tern bike model that takes 24" wheels and a 100mm hub but the one place I've found the fork won't ship to the UK. And I think I'd need to buy the Tern handlepost to go with as well which is more expense.
- The other route to go is getting a 24" fork and making it fit the Dahon headset arrangment - I've found a Schwinn childs fork new on eBay for £15. I guess my first question is is a childs fork going to be strong enough? I know kids are lighter and strain forks less but surely they're built to take some punishment? The Dahon forks have an internal thread with a copper washer and large bolt to preload the headset bearing with the base of the handlebar post clamping round the steerer like a conventional ahead stem. I've got two options here, either way I'll need to cut the steerer tube down but that's not too painful.
- I need to double check my measurements (there are four different sizes of headset bolt out there) but I could get a tap and cut an internal thread in the Schwinn fork. I think I’m looking at a 1”x26tpi – does a normal fork have enough meat to do this?
- The Tern fork uses a standard topcap and starnut to preload its headset, I’ve had a look and I can fit a topcap in and still close the handlebar hinge on my post provided I omit the washer. Would a starnut provide enough hold? I’m sure I’ve read that a standard ahead stem, once the stem is clamped up, can have the topcap removed entirely – my workmate seemed to think that the bolt on the Dahon helps to hold the fork in but it looks to me like it’s acting like a very odd shaped ahead stem. The only difference being that the length of steerer it clamps to is only about 15-20mm with a single pinch bolt. The Tern arrangement on the other hand is a longer section of steerer and a double pinchbolt. If I could get away with using a starnut though it saves a whole step of thread cutting and it’s one less tool to buy.
A few photos of the headset arrangement to show what I'm on about:
I know converting this bike is a bit of a compromise but I got the bike for free, if I bought an electic bike I'd have to go through the faff of selling this one. The cheaper new folding bikes tend to be limited on range and pretty much all have derailleur gears, this has an internal geared hub and a partial chaincase which should help protect it from the winter skog. They also tend to have smaller wheels and having borrowed a Brompton for a week I definitely feel like larger wheels roll better and some of my route isn't wonderfully surfaced.
I mean in an ideal world I'd just go out and get a Tern Vektron but it's £3500 and I think I can do this for <£600 all up.
ETA: For what it's worth the plan is to mount the frame frame battery to the headtube luggage mount sticking out the front there in the first photo. I figure that keeps more of the wiring confined to the front end and away from the hinge fold
and it should balance the weight of the rear hub and luggage at the back. I tend to lift the bike unfolded for the stairs down from the train station as it's actually easier to carry that way than it is in its folded state.