Tam's Geometry Experiment - Hack Bike Derby 2016
The 2016 Hack Bike Derby is an invitational race weekend for frame builders to let off steam and race shonky bikes which would otherwise have no place in their workshop. Let me get a couple of things straight before we get into this:
1. I (Tam) never weld a production BTR
2. This bike build represents some of the ideas I have, not the standard to which I feel it is acceptable to build a bike.
3. I don't think the BTR workshop has ever been dirtier than it was during this build.
4. No animals (except for me!) were harmed in the making of this bike.
Organised by Andrew Denham of The Bicycle Academy, the first ever Hack Bike Derby kicked off on the 6 - 7th of February 2016. The event consisted of a dig day on Saturday, followed by a (badly) floodlit night dual slalom race that evening. On Sunday, there was a DH race, followed by a Le-Mans-style mass start fire-road race. All of which was to be raced on the one (generally) unsuitable bike of your own manufacture. The event winner was the rider with the best overall finishes in all three events.
![So you think you ve seen extreme geometry]()
So you think your bike has extreme geometry?...think again.
The bikes themselves had relatively few regulations; they were to be raced as klunkers, so that was a vague guideline which most followed, their bikes sporting extra top tubes, extra fork blades, crazy seat stays and wild handlebars - I think 900mm wide was the norm! The maximum build budget was recommended to be less than £300 all in, which seemed to be widely adhered to, though I did spot a set of brand new Shimano XT M8000 cranks! There were to be no gears, and brakes had to be rim (preferably not vee), drum, or coaster. I was let off with my disc brakes since I made every part of them except bolts, discs and cables. Bontrager stepped up to supply tyres for the event; all XR4 Team Issue, 26". I was pretty pleased about that; they're way above klunker spec! Oh, and you were obliged to allow any competitor to race on your bike if they requested. We really should have made better use of that rule!
Anyhow, with an almost completely blank canvas I couldn't help but let my mind run riot on the design - particularly the geometry; there was an idea that I'd been wanting to try out for ages, and it promised to result in a truly ridiculous bike. It was on! Two head tubes and linkage steering, coming right up! The next thing playing on my mind was brakes; I had every other component somewhere, but I had no rim brakes and all of my 26" wheels are disc only...I needed a plan. My initial thought was to make a vee-belt pulley that would mount to the disc flange of my wheels, and run the brake as a tensioner which pulled a fixed belt into the pulley...it sounded shady, and I wasn't convinced it would provide significant stopping power. I eventually settled on making my own cable operated disc brakes, and had a pair of used car handbrake cables to connect them up with. Bound to work!
![A brake caliper body nearing completion]()
![And the disc fits]()
![2 finished calipers]()
![Frame tubing scrap ERW a bit of T45 mild steel box section...]()
Now, under event rules I had to make the whole frame myself; dropouts and all. This presents a problem, since my welding is not up to scratch for working with any sort of decent frame tubing - I definitely can't TIG weld to save myself. Dirty old MIG welding it is then, and thick-as-you-like mild steel ERW tubing to save me from blowing holes everywhere (and to save the pocket a bit!). A scrabble through The Bicycle Academy's tubing rack and scrap bin yielded the necessary tube and box section...
![Most of the frame tubing cut to length]()
![The main frame taking shape in the Academy Tools jig]()
![Main mid traingle tubing notched and cleaned]()
Tam's hack bike middle (?) triangle tubes
![Main triangle welded up]()
![Multipass MIG weld]()
Man alive I need to get some welding practice in!
![Stay tubes complete...gnarly]()
![Notchy...]()
![Behold a frame So heavy so gnarly]()
Behold! A frame of epic mass!
How gnarly is that!?!? I have to admit though, I'm rather proud of it; it's the first frame I've ever welded entirely myself! At this point it felt like I was getting through it pretty quickly - it all seemed to be coming together. Onwards with the forks...
![My first fillet braze Fork crown to steerer tube]()
Fork crown/steerer assembly - my first fillet braze!
![Billet machined 20mm front dropouts]()
Billet machined 20mm front dropouts
![Machined 20mm front axle]()
Billet machined hollow 20mm front axle
![Front 20mm dropouts TIG welded into the fork blades]()
![Forks]()
Don't be fooled by that - there's no filler rod there at all; they're just fused on. Still plenty strong though, and looks half decent I reckon!
![Linkage steering]()
Steering linkage...on a bicycle
![Looks almost finished right]()
Looks almost functional and almost finished, but there was another solid day of work to get 'er done!
That was about 4am on Saturday. My newly revised plan was to finish it up in time for dual slalom racing that evening at 7...
...after three hours sleep, I crawled back to the workshop to try and get the brakes together. That's really all there was left! It seemed like a couple of hours of work, so I planned on taking four hours. Tiredness had taken its toll though, so progress was glacial and motivation was dwindling fast! I couldn't even face taking many photos now, I just wanted it finished...
![Integrated rear brake caliper...fancy]()
![Tapping the brake caliper arms]()
Still so much to do even now - brake pads (just little discs of aluminium), handbrake cable stops, complete brake levers, all sorts of brake adjusters, remount my shifter to a truly inconvenient place (shh, don't tell the commissaire!), etc, etc... Motivation was at zero so I just sat down...
![Finished at last]()
Finished at last...so epic, so heavy!
That was 8 pm on Saturday. I'd missed the start of racing, and there was no way I was going anywhere but my bed now!
![The seat works too]()
![Hack Bike Derby 2016]()
Hack Bike Derby 2016 'podium'
Now the important stuff; how does a bike with a 1225mm wheelbase and 75deg head angle ride? Honestly, it's hard to say yet. It's so heavy, the bars are so nasty, the brakes are horribly unergonomic and quite ineffective, and the trails were slop-fest or fire road. I'll figure out the necessary bits though and put in some time on it. It's a concept I'm keen to explore more, but don't worry; it's not scheduled for production any time soon!
Massive thanks to Andrew for putting the event together, and the team of people who made it all happen. Also to all the other builders, competitors, camera-folk and spectators. I'm also hugely grateful to everyone who encouraged me when I was totally ready to give up hope and go home before I'd finished my bike on Saturday afternoon! Finally, much respect to Break Fluid for awesome coffee, tea, and superlative granola...
![A 2CV in the woods Must be Break Fluid]()
A 2CV in the woods?? Big thanks to Break Fluid for keeping us all fueled for the weekend!
Healing vibes go out to those unlucky enough to break themselves, and the ground wherever Ted James hit it. Keep your eyes peeled for total media coverage premiering at Bespoked UKHBS in April - I can hardly wait!
Same time next year?? Go on then...
Tam
MENTIONS: @BTRfabrications
1. I (Tam) never weld a production BTR
2. This bike build represents some of the ideas I have, not the standard to which I feel it is acceptable to build a bike.
3. I don't think the BTR workshop has ever been dirtier than it was during this build.
4. No animals (except for me!) were harmed in the making of this bike.
Organised by Andrew Denham of The Bicycle Academy, the first ever Hack Bike Derby kicked off on the 6 - 7th of February 2016. The event consisted of a dig day on Saturday, followed by a (badly) floodlit night dual slalom race that evening. On Sunday, there was a DH race, followed by a Le-Mans-style mass start fire-road race. All of which was to be raced on the one (generally) unsuitable bike of your own manufacture. The event winner was the rider with the best overall finishes in all three events.
The bikes themselves had relatively few regulations; they were to be raced as klunkers, so that was a vague guideline which most followed, their bikes sporting extra top tubes, extra fork blades, crazy seat stays and wild handlebars - I think 900mm wide was the norm! The maximum build budget was recommended to be less than £300 all in, which seemed to be widely adhered to, though I did spot a set of brand new Shimano XT M8000 cranks! There were to be no gears, and brakes had to be rim (preferably not vee), drum, or coaster. I was let off with my disc brakes since I made every part of them except bolts, discs and cables. Bontrager stepped up to supply tyres for the event; all XR4 Team Issue, 26". I was pretty pleased about that; they're way above klunker spec! Oh, and you were obliged to allow any competitor to race on your bike if they requested. We really should have made better use of that rule!
Anyhow, with an almost completely blank canvas I couldn't help but let my mind run riot on the design - particularly the geometry; there was an idea that I'd been wanting to try out for ages, and it promised to result in a truly ridiculous bike. It was on! Two head tubes and linkage steering, coming right up! The next thing playing on my mind was brakes; I had every other component somewhere, but I had no rim brakes and all of my 26" wheels are disc only...I needed a plan. My initial thought was to make a vee-belt pulley that would mount to the disc flange of my wheels, and run the brake as a tensioner which pulled a fixed belt into the pulley...it sounded shady, and I wasn't convinced it would provide significant stopping power. I eventually settled on making my own cable operated disc brakes, and had a pair of used car handbrake cables to connect them up with. Bound to work!
First brake caliper body nearing completion
...and the disc fits! Bonus.
Two completed brake caliper bodies
Scraps, offcuts, ERW, and a very little T45 are the main components of Tam's frame
Now, under event rules I had to make the whole frame myself; dropouts and all. This presents a problem, since my welding is not up to scratch for working with any sort of decent frame tubing - I definitely can't TIG weld to save myself. Dirty old MIG welding it is then, and thick-as-you-like mild steel ERW tubing to save me from blowing holes everywhere (and to save the pocket a bit!). A scrabble through The Bicycle Academy's tubing rack and scrap bin yielded the necessary tube and box section...
Tam's Hack Bike Derby frame tubing looking a bit more rational than when it started
Tam's hack bike frame starting to come together
Mid/front triangle done!
Multipass MIG weld?
Man alive I need to get some welding practice in!
Tam's hack bike stays!
Chain stay notch...massive!
How gnarly is that!?!? I have to admit though, I'm rather proud of it; it's the first frame I've ever welded entirely myself! At this point it felt like I was getting through it pretty quickly - it all seemed to be coming together. Onwards with the forks...
20mm thru front dropouts TIG welded onto the fork 'blades'
Forks!
Don't be fooled by that - there's no filler rod there at all; they're just fused on. Still plenty strong though, and looks half decent I reckon!
That was about 4am on Saturday. My newly revised plan was to finish it up in time for dual slalom racing that evening at 7...
...after three hours sleep, I crawled back to the workshop to try and get the brakes together. That's really all there was left! It seemed like a couple of hours of work, so I planned on taking four hours. Tiredness had taken its toll though, so progress was glacial and motivation was dwindling fast! I couldn't even face taking many photos now, I just wanted it finished...
Integrated brake caliper anyone??
Brake caliper lever arms taking shape - big thanks to Matt Stitt for hacking these out for me!
Still so much to do even now - brake pads (just little discs of aluminium), handbrake cable stops, complete brake levers, all sorts of brake adjusters, remount my shifter to a truly inconvenient place (shh, don't tell the commissaire!), etc, etc... Motivation was at zero so I just sat down...
That was 8 pm on Saturday. I'd missed the start of racing, and there was no way I was going anywhere but my bed now!
Testing out the seat...seems to work - Roll on Sunday, LET'S GO RACING!! (on a horrendously heavy bike with bad brakes and the worst handlebars ever...)
Turns out that aluminium pads are actually pretty handy; the aluminium builds up on the disc, and generates a usable amount of friction! I could even do a skid**, which is much more important than it sounds!
I somehow managed to plough my way to 3rd place out of 18 in the DH race, I think mainly because I was scared that I would die if I crashed! In the mass start, I totally failed to utilise my selectable gears, and came stone last out of everyone who didn't stack. What a plonker!
Burf wrapped up the overall, having taken 1st in dual slalom, 4th in DH and 2nd (?) in the mass start. Tidy!
**using three fingers on the lever
Turns out that aluminium pads are actually pretty handy; the aluminium builds up on the disc, and generates a usable amount of friction! I could even do a skid**, which is much more important than it sounds!
I somehow managed to plough my way to 3rd place out of 18 in the DH race, I think mainly because I was scared that I would die if I crashed! In the mass start, I totally failed to utilise my selectable gears, and came stone last out of everyone who didn't stack. What a plonker!
Burf wrapped up the overall, having taken 1st in dual slalom, 4th in DH and 2nd (?) in the mass start. Tidy!
**using three fingers on the lever
Now the important stuff; how does a bike with a 1225mm wheelbase and 75deg head angle ride? Honestly, it's hard to say yet. It's so heavy, the bars are so nasty, the brakes are horribly unergonomic and quite ineffective, and the trails were slop-fest or fire road. I'll figure out the necessary bits though and put in some time on it. It's a concept I'm keen to explore more, but don't worry; it's not scheduled for production any time soon!
Massive thanks to Andrew for putting the event together, and the team of people who made it all happen. Also to all the other builders, competitors, camera-folk and spectators. I'm also hugely grateful to everyone who encouraged me when I was totally ready to give up hope and go home before I'd finished my bike on Saturday afternoon! Finally, much respect to Break Fluid for awesome coffee, tea, and superlative granola...
Healing vibes go out to those unlucky enough to break themselves, and the ground wherever Ted James hit it. Keep your eyes peeled for total media coverage premiering at Bespoked UKHBS in April - I can hardly wait!
Same time next year?? Go on then...
Tam
MENTIONS: @BTRfabrications
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*Immediately punched in the face*
The short rear centre could certainly contribute to the slacker feel of the bike.
Anyway, if you have the chance to test a Rallón, DO IT. It's an amazing bike, and it really shines on the downhills.
Very cool experiment by the way!
I can't take the suspense
by the way awesome idea