I attended the Welding and Light Metalwork course at the Hammersmith learning centre in late 2011; I can highly recommend this to anyone who has an interest in getting started with welding. I had been using a MIG welder for my previous projects since that was what was available to me, and because it's so easy to use; this course allowed me to experiment and learn a number of other welding techniques. It also allowed me the opportunity to start a new project; it had to be another bike frame really, didn't it?
At this point I had ended up buying a 29er hardtail frame; this was proving to be an excellent commute and XC bike and I decided that what I needed was a general "play bike" to suppliment this - something to take to the occasional DH course, something to hit the bigger trails on. An all-mountain bike, or maybe an "Enduro" bike, possibly a "Super D" bike, or if you're still in the last decade, a freeride bike.
With more than a little inspiration from the Orange bikes website (here) I resolved to make myself a version of the new Patriot bike that, at the time, was only a rumour. I have owned a couple of Orange Patriots in the past (one of the original 5" travel bikes, and one of the 7+ freeride bikes) and they always were great to ride - a wonderful balance of simplicity, great geometry, relative light weight, and effective suspension.
The design design I settled on was:
- 7" travel using the 222mm shock from the DH frames
- 65deg head angle with 7" travel forks
- 23" top tube (going with the trend for longer top tubes and shorter stems)
- clearance for a 3" tyre on a 26" wheel (outside diameter of 28")
- an eccentric bottom bracket to allow the BB height to be adjusted allowing the use of a wide tyre range without adversely affecting the ride height (also because I had an eccentric BB shell spare)
Unfortunately I only got time on the welding course to get part of the front-end of the frame constructed; this project is currently in limbo but certainly not forgotten. It is my intention to resurrect this frame design in the very near future as a 650b bike.
Why 650b?
Well I'm a sucker for trends! But also because the 650b wheel size will fit my existing design with almost no change (I might adjust the position of the rear drop-outs but it's not actually necessary since I designed the frame to fit huge tyres) and the 27.5" wheel size is perfect for what I want out of this bike - I want the grip, stability and confidence of larger wheels but this bike is all about having silly fun (something that feels a bit lost sometimes when riding 29" wheels).
Friday, 27 April 2012
29er trail bike
So I had made a rather sweet but flawed 29er downhill bike, and a very functional but less plush trail bike. The next step was to attempt to take the best of both worlds and create The One Bike.
Of course it's impossible for even the biggest, best and most innovative bike companies to make a bike that is perfect for everything.
But what do they know?
I decided that the solution to all my bike desires would be a 29er trail bike with 5" travel. With 5" travel my high-pivot design would require no chain routing so would hopefully be as reliable as my previous trail frame, and with the 29er wheels we'd hopefully have some of that amazing plushness that big wheels are famous for.
I invested in some proper chromoly bike tubing this time and set about making what I hoped would be a master-piece:
Again, I couldn't help but do a bit of colour coordination with the build:
Unfortunately I just didn't get this bike right. The rear drop-outs were not aligned well, the weight was still above what you would really want to drag around all day and the fit was wrong - the main problem being that the top-tube length was too short. This bike works but just was not the dream-bike that I had hoped it would be. It also seemed to be the wrong combination of the previous 2 builds - rather than having the solid build of the trail bike and the confidence inspiring feel of the 29er DH what it really felt like was numb, boring, not-that-plush, unmanouverable AND unstable. I simply hadn't designed or built this very well.
In order to address this I started reading every article about 29er design that I could find, and signed up for a welding course...
Of course it's impossible for even the biggest, best and most innovative bike companies to make a bike that is perfect for everything.
But what do they know?
I decided that the solution to all my bike desires would be a 29er trail bike with 5" travel. With 5" travel my high-pivot design would require no chain routing so would hopefully be as reliable as my previous trail frame, and with the 29er wheels we'd hopefully have some of that amazing plushness that big wheels are famous for.
I invested in some proper chromoly bike tubing this time and set about making what I hoped would be a master-piece:
Again, I couldn't help but do a bit of colour coordination with the build:
In order to address this I started reading every article about 29er design that I could find, and signed up for a welding course...
Trail bike
Annoyed with the constant series of chain problems on my designs so far I resoved to do my next frame with no fancy chain routing. Still sticking to the high-as-practical pivot point design with a simple swingarm I started work on a 26" wheeled trail bike with 5" travel:
I was pretty happy with how this frame came together, particularly the swingarm:
I don't think this bike looked quite as impressive as the 29er DH prototype but it wasn't a bad machine:
More to the point, this was my first build that really worked. I rode this at Cwm Carn (it survived the red DH course), at Swinley forrest (it was pretty handy over the jumps) and I even commuted on it. It pedalled well, it wasn't exactly light but was a perfectly usable weight and it was totally reliable; and with a short chainstay length and sensible head angle it was even quite fun to ride. The suspension action was pretty unimpressive but that probably had something to do with the £30 rear shock that I had fitted.
Not quite the perfect bike, but getting closer?
I was pretty happy with how this frame came together, particularly the swingarm:
I don't think this bike looked quite as impressive as the 29er DH prototype but it wasn't a bad machine:
More to the point, this was my first build that really worked. I rode this at Cwm Carn (it survived the red DH course), at Swinley forrest (it was pretty handy over the jumps) and I even commuted on it. It pedalled well, it wasn't exactly light but was a perfectly usable weight and it was totally reliable; and with a short chainstay length and sensible head angle it was even quite fun to ride. The suspension action was pretty unimpressive but that probably had something to do with the £30 rear shock that I had fitted.
Not quite the perfect bike, but getting closer?
The 29er downhill bike
After getting mixed-but-encouraging results with the attempt at making a downhill frame I was puzzling over where to take the design next.
And then I saw the Intense 2951 downhill 29er - it just looked so "right". At this point 29ers were just taking off in the US, virtually non-existant in the UK, and entirely dedicated to XC - the Intense 2951 might just have been a joke or mad experiment but the idea had me hooked. I had to try out the 29er idea on my next build.
In combination with the alterations to my DH frame design to route the chain just underneath the swingarm and pivot I got hold of some more cheap mild-steel tubing and set to work again:
Rather proud of my handiwork I couldn't help but paint up the bike and kit it out with colour-coordinated components; it wasn't as pretty as the Intense but to this day I'm still pretty happy with the way this came out:
I was a bit disappointed to find I still had problems with the chain - while I could pedal slightly further than the previous attempt this frame still had a habit of killing whatever was routing the chain. The bike also felt very weird under pedalling, the chain tension pulls the wheel down which is very efficient but does mean the rear feels like it's bobbing about all over the place. This chain tension also meant the suspension didn't feel as plush as the Tank however this bike did actually work - for breif periods of time anyway.
This bike, as pictured above saw a good day of uplift-assisted downhilling at Cwm Carn - it performed admirably. It ironed out the trail bumps like no other bike I've ridden, it gripped like crazy, it felt amazingly stable but also cornered just fine. It even jumped pretty well. What really impressed me was just how much confidence the bike gave me - when I rode the same tracks on a 26er I was all over the place, the 29er DH made the difficult track easy - I could focus entirely on carrying speed, what line I wanted to take and generally just enjoying the trail; on the 26er I spent the entire time hanging on for dear life, struggling to make the next corner. Despire the chain troubles it seemed like I was on to something here.
And then I saw the Intense 2951 downhill 29er - it just looked so "right". At this point 29ers were just taking off in the US, virtually non-existant in the UK, and entirely dedicated to XC - the Intense 2951 might just have been a joke or mad experiment but the idea had me hooked. I had to try out the 29er idea on my next build.
In combination with the alterations to my DH frame design to route the chain just underneath the swingarm and pivot I got hold of some more cheap mild-steel tubing and set to work again:
Rather proud of my handiwork I couldn't help but paint up the bike and kit it out with colour-coordinated components; it wasn't as pretty as the Intense but to this day I'm still pretty happy with the way this came out:
I was a bit disappointed to find I still had problems with the chain - while I could pedal slightly further than the previous attempt this frame still had a habit of killing whatever was routing the chain. The bike also felt very weird under pedalling, the chain tension pulls the wheel down which is very efficient but does mean the rear feels like it's bobbing about all over the place. This chain tension also meant the suspension didn't feel as plush as the Tank however this bike did actually work - for breif periods of time anyway.
This bike, as pictured above saw a good day of uplift-assisted downhilling at Cwm Carn - it performed admirably. It ironed out the trail bumps like no other bike I've ridden, it gripped like crazy, it felt amazingly stable but also cornered just fine. It even jumped pretty well. What really impressed me was just how much confidence the bike gave me - when I rode the same tracks on a 26er I was all over the place, the 29er DH made the difficult track easy - I could focus entirely on carrying speed, what line I wanted to take and generally just enjoying the trail; on the 26er I spent the entire time hanging on for dear life, struggling to make the next corner. Despire the chain troubles it seemed like I was on to something here.
2nd attempt - The Tank
Since I owned a good trail bike at the time my next attempt at building a frame was a downhill rig. The design I was attempting was a high-pivot point, but otherwise uncomplicated swingarm. The difficulty with a high pivot os chain routing though. My design called for the chain to be routed over the pivot, not realising how difficult this would be to get right I drew out the design onto a sheet of MDF, ordered a load of cheap mild steel tubing, confiscated my Dad's garage and tools for a weekend and came up with this:
It was designed around a 222mm shock (2.75" stroke) with a 2.5x shock leverage ratio giving approximately 7" travel. Fully built it looked pretty mean:
The first test was a resounding success: I could stand on it and it didn't fall apart!
The thing weighed an absolute ton, but it rolled over large curbs like they simply weren't there. I was so happy at this point I actually had tear in my eyes - I had managed to make a bike! It rode well, it felt right, it's suspension was far better than I could have hoped and it seemed as solid as a girder.
What this build could not do however was pedal. All my attempts at routing the chain over the pivot seemed to bend, break or disintegrate within a few pedal strokes. The high pivot point was brilliant for the suspension feel but was causing big problems for drive - my next attempt would try to fix this.
It was designed around a 222mm shock (2.75" stroke) with a 2.5x shock leverage ratio giving approximately 7" travel. Fully built it looked pretty mean:
The first test was a resounding success: I could stand on it and it didn't fall apart!
The thing weighed an absolute ton, but it rolled over large curbs like they simply weren't there. I was so happy at this point I actually had tear in my eyes - I had managed to make a bike! It rode well, it felt right, it's suspension was far better than I could have hoped and it seemed as solid as a girder.
What this build could not do however was pedal. All my attempts at routing the chain over the pivot seemed to bend, break or disintegrate within a few pedal strokes. The high pivot point was brilliant for the suspension feel but was causing big problems for drive - my next attempt would try to fix this.
1st attempt
My first attempt at a bike frame was to make a 5" travel trail bike out of fibreglass over balsa wood and aluminium.
The idea was to create a do-it-all bike that could be easily taken apart into parts to fit in a regular suit-case allowing you to take a bike on holiday without having to faff about with oversized baggage. It was also designed around 24" wheels (which I found could just about fit into a large suitcase).
At this point I had no access to welding equipment so I took the decision to attempt to use composites to make a frame. Obviously carbon fibre would be the ultimate material to use but for a first attempt I tried fibreglass.
The basic premise was to use aluminium tubing for the seat post and head tube, bottom bracket shells for the main BB and also for the swingarm pivot, and surly drop-outs (which combine the drop-outs, mech hanger and rear disk mount), glued to a balsa-wood frame core. This would make it very easy to make the basic layout of the frame using only hand tools. Aluminium sheet would then be glued over the top of the balsa wood core where serious strength is needed. Finally fibreglass goes over the top to bind everything together and provide structure.
This is what it looked like with the core and alu sheeting assembled:
And the finished article:
And what it looked like after I tried to ride it:
It seems my design had a bit of a flaw... In trying to design a swingarm that gave maximum crank clearance (and was as simple as possible to fabricate) I had made something that had about as much structural integrity as a dandilion. I went back to the drawing board...
The idea was to create a do-it-all bike that could be easily taken apart into parts to fit in a regular suit-case allowing you to take a bike on holiday without having to faff about with oversized baggage. It was also designed around 24" wheels (which I found could just about fit into a large suitcase).
At this point I had no access to welding equipment so I took the decision to attempt to use composites to make a frame. Obviously carbon fibre would be the ultimate material to use but for a first attempt I tried fibreglass.
The basic premise was to use aluminium tubing for the seat post and head tube, bottom bracket shells for the main BB and also for the swingarm pivot, and surly drop-outs (which combine the drop-outs, mech hanger and rear disk mount), glued to a balsa-wood frame core. This would make it very easy to make the basic layout of the frame using only hand tools. Aluminium sheet would then be glued over the top of the balsa wood core where serious strength is needed. Finally fibreglass goes over the top to bind everything together and provide structure.
This is what it looked like with the core and alu sheeting assembled:
And the finished article:
And what it looked like after I tried to ride it:
It seems my design had a bit of a flaw... In trying to design a swingarm that gave maximum crank clearance (and was as simple as possible to fabricate) I had made something that had about as much structural integrity as a dandilion. I went back to the drawing board...
Intro
This blog is an archive of my attempts to build bicycle frames from scratch.
I am starting this after several builds with varying levels of success...
I am starting this after several builds with varying levels of success...
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