Sunday, 11 November 2012

Genesis Equilibrium Build Log Part 2: Drivetrain thoughts

In a previous post here, I described some ways of configuring single speed for a road bike conversion. The Equilibrium frame has vertical rear dropouts. These do not allow chain tension adjustment for single speed mode. You need to have some, because a slack chain is dangerous!

A common solution is to use a chain tensioner:

These normally screw into the rear mech boss and use a sprung lever to tension the chain, usually by an jockey wheel or similar, running against the chain. It's even possible to use an old rear mech as a chain tensioner (e.g. by running the chain round the lower jockey wheel only).

However, I don't like these ideas much, as the silent, simple, smooth, single speed feel can't be fully achieved when there's a wheel tensioning the chain.

One option is to forget about single speed, and use a cassette and rear derailleur. It so happens that I have some wheels that are nutted solid axle, the rear having a screw-on freewheel, and I have a suitable 6 speed block. The only thing that bothers me is the possibility that at extreme angles, the chain may drop off the chainwheel. A prevention mechanism for that is to use a chainset with inner and outer chain guards, but that may be hard to find at a reasonable price. Another option there is to fit an old front mech to act as a chainwheel chain keeper.

The concept for this build is to keep it simple, cheap, and that means re-using parts that I already have, so far as possible. It looks like I'm going to have to experiment quite a bit. As I said, this may end up a weird bike!

Autumn: time for Cyclocross, Overshoes,...

...falling leaves and nuts!

Wednesday, 7 November 2012

Genesis Equilibrium Build Log Part 1: The Frame

Genesis Bikes' Equilibrium frame has earned a great reputation. They struck a happy chord with this one, producing by all accounts a comfortable, rewarding and beautifully finished frameset. I had the good fortune to pick up a new example at a bargain price. My intention is to build it up as a commuter as cheaply as possible. That means using as many of my own bits and bobs that I have lying around. So there's a good chance it will end up a bit weird!
This is nominally a 56cm frame, but the Genesis website specifies seat tube (c-t) 550. It has a relatively short effective top tube of 558, suggesting it will have an upright riding position. Head tube is smallish 150, and the seat post is going to be long, given the sloping geometry of the frame. It's made from Reynolds 725 tubing as shown by the classic seat tube sticker (the description of 725 below is from the Reynolds website):

Using an industry standard alloy with mechanical properties similar to our famous 753 brand, Reynolds mandrel butt and heat-treat this alloy so that thinner walls can be used compared to non-heat-treated steels. 725 can be TIG welded and used within our "Designer Select" combinations including 853 and 631 tubes.
Why it works:
UTS: 1080-1280 MPa, density 7.78gm/cc
Based on a 0.3% carbon steel alloy which has been heat-treated and back-tempered for increased ductility. The chromium content promotes hardenability and resistance to oxidation. The molybdenum works in conjunction with the chrome to stabilize the alloy and maintain strength after heat-treatment and in use."
I believe the forks are carbon with alloy steerer (standard headset required, 1 1/8" size), dropouts and brake bushing. Certainly a magnet does not stick to them as it does to the tubing. DT cable guides already fitted, hmm, but am I going single speed? Mudguard eyes (and a paint scratch):
Neat welding and easy on the eye. Seeing the top tube cable ends - reminds me that I always forget to use frame protector cable grommets. Let's see if I remember this time.
BB shell is standard 68. A very sensibly engineered bridge between the chainstays, should make mudguard fitting much easier:
Quite a lot of dust on the frame - needs a spray of frame saver inside and a good clean outside before I start. Seat tube is 28.6 for front mech (if I'm having one, that is!).  
Below, you can see the straight stays and the geometry. Given the short head tube, I'll probably not cut the steerer, but let's see. 
The rear brake bridge (long drop 57) and seat clamp (29.8). Tseat post is 27.2 diameter - I have one of those in my bits box, but will it be long enough?
Stays are quite thin at the tips and the dropouts seem well made. 
Initially I thought that the kink on the inside of the drive side seat stay (below) was a show room dent, but then I looked closely and it's clear that it is deliberate shaping. Quite obvious that the paint was applied after the shaping. The shop told me that other people had queried it, and they'd already clarified with Genesis that this was a deliberate feature. Presumably it's for chain clearance, but some have commented that it is ugly and unnecessary. 
All in all a lovely frame, and I'm feeling quite excited to build her up, as I said, using what I have "in stock". I will need to buy long reach brake calipers though. After the satisfaction and simplicity of my last single speed build, I'm definitely keen to forget completely about gears... 
Well done Genesis. Can't wait to see your new 953 road racing frame for the Madison-Genesis cycling team, Roger Hammond and Co. He's a cyclocrosser too, so I'll be cheering for them!

Monday, 5 November 2012

Round 8 Wessex CX League - Oxonian at Harcourt Hill, Oxford Brookes

On Saturday it rained cats and dogs. On Sunday, the cyclocross frogs came out to play. The amphibians frolicked on a very wet course - and it was cold too. These photos were taken early in the day. The avenue in the woods (below) may look dry underfoot, but I assure you it was not! It soon transformed into a muddy brook. Seriously, the water was flowing (towards you in the photo below). Pedalling through the woods, was more like paddling up and down stream. A very unusual sensation.
The path below was waterlogged too, and quickly cut up into a boggy slush. I wish I had taken "after" photographs to demonstrate what I mean about the "rivers" through the woods. That sign should have read, "Care! Deep water and strong currents!" 
Here are the youngsters hard at it. The hooded spectators are riders perusing the course prior to their race. Everyone is wondering why they didn't stay tucked up under the duvet this morning...
Of course, the sun started to (threaten to) show itself just as the race was ending. Here's the chicaney bit leading into the finishing straight. A nice design feature that made for a few excellent sprint finishes. 
Below is the finish line and time-keeper's gazebo. All in all, a well thought out circuit. Other features included two open earth sections that you had to ride rather like sand. Tyres clagged up quickly, but the mud shed fast afterwards. One of these "flower bed" sections came just after a double barrier. And then of course, was the infamous ditch that marks the entrance to the flooded wooded section. You get to the ditch via a narrow opening in a hedge. The ditch itself was full of cold muddy water and a decent leap was required to cross it. There were also a few bobbly bumps, ramps and such, that may well have caught out an unwary rider. 
But the most significant feature today was the waterlogged ground. Heavy going and grunt work. Luvvly Jubbly!