You might remember Adrian’s radical prototype from a few months ago, where he set out to build a 29’er with the shortest possible chainstays – well, he’s back again with V2!
Adrian caught the frame design bug with his first bike and immediately started to think what he would do differently next time…
I love the way V1 works but what lets it down is heel clearance. When clipped in with small feet there’s no problem, but bigger feet and flats have an issue, so getting the rear end narrower was a goal. The bottom bracket flex was never a problem when riding, but I think it would be with a belt drive. There was no discernible side to side play but just a little rearward movement when standing on the pedals at very low cadence.
So on V2 the chain stays are lower and the down tube is up to 50mm diameter. There is virtually no rearward movement under pedaling load now.
Aesthetics played a big part in Adrian’s first design and he wanted to improve how the frame looked as well as how it rode with V2:
I went for it with trying to get more shape in the tubes, on the top tube I wanted a constant radius from head tube to dropout but also a taper. I had to push Porter quiet hard for this and even draw up the mitres around the seat tube to show him it would work.
The downtube is ovalised vertically to fit onto the tapered head tube and then again in the other direction to give the maximum weld area across the bottom bracket.
You can tell Adrian’s had great fun with tweaking his design. Deciding to run a single chainring means he could bring the chainstays closer to the bottom bracket for greater stiffness. Beefing up the downtube and running a tapered headtube will all help to keep things stiff which is important when you’re building an elevated chainstay bike.
Comparing the two side by side we can get an idea of what’s changed:
Compared with version one the second frame looks much more ‘together’. The curves and larger tubes give the frame a real presence plus the bottom bracket doesn’t look like it’s going to swing around under the frame! The stays and custom dropouts were deliberately overbuilt with the first design so Adrian was able to slim the back end down and tuck things in better with V2.
The built up weight of V2 is currently around 29lbs as you see it in the pictures, but that does include a rather sturdy Shimano Alfine hub and steel forks.
Future projects? Well first up could be a belt drive conversion, the raised stay design makes it easy to fit and it would be the ultimate test of how stiff the frame is. Adrian is pricing up the parts as I type…
I wouldn’t be surprised if there’s a version three on the cards too, perhaps focusing on refining the design further and taking some weight out. Tube sizes and wall thickness could be optimised and the dropouts created in aluminium instead of titanium.
But then again for something really off the wall, how about a hub-steer balance bike? Remember where you heard it first 😉
Have you had a frame made by XACD? If so I’d love to hear about it and maybe feature it in the Gallery so drop me a line via the contacts page.