Rob’s Polo Bike Update

Rob’s bike is done, rushed through the final stages to get off to the World Hard­court Bike Polo Cham­pi­on­ship in Switzerland.

Alto­gether I’m pretty pleased with how this one turned out. The com­puter mod­el­ling to get the seat-tube curve con­cent­ric with the wheel worked out superbly. For the gear that Rob was run­ning, the chain­stay length could be cal­cu­lated and the centre of the curve placed at the centre of the axle. It wasn’t until the whole bike was built up and the chain ten­sioned that we were able to check how it looked.

The reason for the curved seat tube is to elim­in­ate toe over­lap. This bike shares very sim­ilar geo­metry to Vive’s bike, and all Whis­keys to date, with super quick and nimble hand­ling bal­anced with a meas­ure of sta­bil­ity. In this latest evol­u­tion, the curved seat tube simply moves the cranks back away from the front wheel. This is a no com­prom­ise bike. There is no space wasted and no curve that doesn’t need to be there. The down­tube is straight gauge tubing to improve crash tough­ness. You could basic­ally ride this thing straight into a wall and it will just bounce off. No amount of gus­set­ting or rein­for­cing of the headtube joint will give that same tough­ness. After see­ing forum pho­tos of polo bikes that had fol­ded at the end of the but­ted sec­tion it became clear that the small weight pen­alty was worthwhile.

With such short chain­stays, and fat tyres (will fit 26 x 2″), fit­ting chain­stays / tyre / chain­rings / cranks became an issue. That’s why the whole thing needed to be mod­elled in the com­puter first.

Here’s a pho­toshop mock up dur­ing work on the frame:

To recap:
Sand filled tube bent

BB scal­loped and brazed

Built (click for ani-gif)



Thanks for the lovely bottle of Whis­key Rob and good luck in Switzer­land and London!

Welding and Brewing

About a year ago I bought a second hand com­mer­cial TIG welder in an attempt to learn how to weld. Start­ing at the bot­tom of the learn­ing curve with weld­ing means join­ing com­par­at­ively thicker steel. Hap­pily, I’ve also been think­ing about rejoin­ing the ranks of homebrew­ers. This threw me the oppor­tun­ity for a few steel fab­ric­a­tion jobs

I wanted to start my brew­ing adven­tures with cider because deal­ing with apples seems to involve me more with lovely local pro­duce. Cider can also be brewed with wild yeasts and pro­duce some amaz­ing funky fruity com­plex fla­vours that get lost in the chem­istry like pro­cess of beer brew­ing. I was also inspired by a French work mate who, for his farewell party, pro­duced a bottle of his uncle’s secret-recipe brew to accom­pany the crepes and home-made rasp­berry jam. The cider was like noth­ing I’d ever had; cloudy and fruity, it tasted like sun­light on apple trees, it tasted like verd­ant countryside.

The first thing was to find cider apples. Clearly, Petty’s Orch­ard in Templestowe was the best option close to North­cote. Situ­ated on the banks of the Yarra and cov­er­ing 44 hec­tares, they grow many vari­et­ies of her­it­age apple and quite a few cider vari­et­ies too. There is also a Her­it­age Apple Soci­ety that col­lect and pre­serve hun­dreds of vari­et­ies of apple in a 2 acre plot on site. I spent an after­noon chat­ting to a friendly guy there about apples. In the end I ordered 40 kg of Stew­art Seed­ling apples from the guys at Petty’s.

The next step is to extract the juice from the apples. Hav­ing bought a few books about the pro­cess, I dis­covered that the best way to do this is chop them up to a pulp and then press the pulp to extract juice. I needed a pulper. There are many ways to do this of course, but I wanted a cheap, easy device that doesn’t take too much space. I saw a ver­sion online that is basic­ally a giant food pro­cessor, or if you want, a razor sharp heli­copter blade inside a food-grade bucket. A few web­sites in the UK sold them, but didn’t seem to ship to Aus­tralia, so I thought I’d weld one up myself! It’s essen­tially a steel tube with sup­ports to hold it ver­tical and it is held in the middle of the bucket by a hole in the lid. The blade and shaft are stain­less steel.

Chop­ping and press­ing is a pretty big under­tak­ing… Luck­ily I have an amaz­ing land­lord who makes his own wine and an eager helper with a bit of wine mak­ing exper­i­ence him­self, Mr Jack Dun­stan. It turns out that a wine press is not very good for press­ing apple purée (the purée squeezes out the gaps and you only extract about half of the juice), but it’s all a learn­ing process.

After fer­ment­ing for a few weeks, Jack came and helped me bottle the lot too, champion.

In the mean time, my friend Cristal wanted to upgrade the 3-tiered all-grain brew rig she got from a guy in South Aus­tralia. I helped her to weld in a drain port, an out­let, a sight gauge and thermo well into an old keg. Then a few weeks ago I went and brewed a batch with her.

Hot Liquor Tank — Wel­ded ports

Cristal in her Brew Shed — Sun­shine Brewery

Sun­shine Brew­ery Label

I also found a cheap way to con­trol the tem­per­at­ure of the brew as it fer­ments with a fant­astic little tem­per­at­ure con­trol­ler I got on eBay. Auto­mated con­trol sys­tems get me a little bit excited. Must be the engin­eer in me com­ing out.

Tem­per­at­ure con­trolled fermenter

In the end I’ve learnt a lot about brew­ing and my welding’s get­ting a lot bet­ter too. I even felt con­fid­ent enough to weld a disc tab onto Jol’s polo bike and did a really neat job. (Jol is the graphic designer who cre­ated my new logo.)

Rob’s Polo Bike

I’ve been slowly work­ing away at mak­ing Rob’s polo bike, it’s tak­ing an infuri­at­ingly long time to get this one together because we’re going for a curved seat tube.

Rob has rid­den a couple of my polo bikes and likes the hand­ling of the short wheel­base, but really can’t stand toe over­lap. By keep­ing the geo­metry sim­ilar in other regards, but mov­ing the BB away from the front wheel, it’s pos­sible to get the best of both worlds.

The first trick with design­ing this was over­com­ing the lim­it­a­tions of my exist­ing frame design soft­ware. The best way to visu­al­ise it was to draw the whole bike up from scratch in 3D CAD. With this model I can work out the clear­ances for such short stays. The Colum­bus S-bend chain stays help provide clear­ance, but work­ing out just where to put the curves can be tricky. Bet­ter still, I now have a lovely para­met­ric CAD model of a bike. This means that I can simply change a few num­bers and gen­er­ate dif­fer­ent bikes in the future. It’s a nice build­ing block to have worked out.

In the above image, the BB shell is clearly very close to the tyre. I plan to scal­lop the BB shell to achieve even clear­ance all around the tyre here.

The trouble is, I’ve never curved a seat-tube before. I’ve only read about how tricky it can be, and I cer­tainly don’t have the tool­ing for it… back to the draw­ing board.

I can use this man­drel with the exist­ing hard­ware I made for my tight radius fork bender, and I had hoped I could get a cab­inet maker friend to make the man­drel for me, but he quit his job. So I bough some hard­wood from a junk-yard, bor­rowed a router from a friend, bought the appro­pri­ate router bits, made a quick router guide and presto..

The first attempt at bend­ing res­ul­ted in a bent bolt and some slight crack­ing to the man­drel. I guess I’ll just have to keep rein­for­cing the thing until it works, or until some­thing breaks permanently.