An afternoon with Fast Boy

Yesterday I had the opportunity to hang out at Fast Boy Cycles shop in Harlem, and pick his brain on bike building, while he brazed together a fork.

A little back story: Fast Boy Cycles is one guy. Ezra Caldwell. I met him in the summer here, and his life took a turn for the strange shortly after, when he was diagnosed with cancer. He's got a blog about it HERE. Long story short, he's doing great, and working against his doctors orders amidst chemo treatment cycles.

It was really interesting to see him work, and discuss frame building techniques.

"The one thing I like about brazing, is... its just... so quiet." He said while flowing brass into the crown of the fork. His voice is scratchy from a cold, and its still easy to hear him over the torch. "Its just glorified soldering, really."

A bit about the fork. It was a 1" threaded steerer with Pacenti crown, straight blades, stainless dropouts AND a disc tab! I thought this was a strange combination at first and wondered if it was at the customer's request. Ezra assured me that the customer had given him free reign to do whatever he wanted with the frame. Must be nice to get to do whatever you want knowing that someone is looking forward to the end result.

I was most impressed with the choice of tooling Ezra had set up in his little space. Most of his fixtures were from Anvil, apart from a home made fender forming jig, and small milling machine. The Anvil stuff looks really user friendly, and probably makes his work a whole lot easier.


Here's the Anvil 'Phrunt Shui' disc tab fixture. Seeing that, along with the fork fixture gave me some good insight into how one would go about creating strange custom 5 piece forks.

At the end of my visit, the straight blade fork was complete, save for a touch of filing. I'm looking forward to seeing the finished bike on his Flickr.

I'm really glad I went to see Ezra work, as he is a pretty inspiring guy. He got me really stoked to work on my tallbike today over at les shop du WMD.

Thoughts on laser cut dropouts..

Recently, while visiting the Brooklyn Machine Works shop, I had a look at a variety of Laser cut dropouts. I can't get into detail about the the designs I saw there, because I don't have pictures to illustrate them, and there was just TOO much awesomeness going on there to be described in one post.

Laser Cutting is the general technology used to churn out dropout after dropout for the majority of today's track and BMX frames. Obvious exceptions to this are the forged and machined examples found on some high end bicycles. For the most part however, the single thickness dropouts found on your track bike, were cut with a CNC driven laser.

Plasma cutting is another viable option, and may have been used in the past. However, the width of beam is slightly larger than with a laser, and therefore accuracy is less. With the ever decreasing price of laser cutting technology, its almost easy for designers to get carried away.

(BMW actually doesn't do any laser cutting in house. They do their designs in AutoCAD and contract another metal shop to do that)


I'm not going to name names, but here we have excessive laser cutting. Its as though the designer wanted some swoopy crescents to dress up his dropouts. A napkin was marked up with a fine tipped sharpie, and sent overseas. The factory reviewed said napkin, said "Sure thing chief!" and away they went with the CAM program. Never mind that the actual crescent shapes have no flow, and subsequently do nothing to create an air of classiness. Now, I don't personally know how much this will affect the strength of the design. I just get this vibe that its a bad idea.

A city ridden bicycle is subject to stresses many times greater than the riders weight when road imperfections are encountered. The axle pushes UP on the dropout with ridiculous amounts of force. These stresses occur at high frequency, every ride. These are the sort of forces that (over time) lead to dropout weldment failures, or similarly seat stay/seat tube junction failures.

A stress riser is essentially where localized forces can overcome the shear strength of a material. And nothing localizes forces more than sharp angles. The stress concentration factor goes up exponentially as the radius of a cut approaches zero. The idea of adding 8 tiny-radius-acute-angle cuts to a small piece of metal that is undergoing high frequency shear forces from the axle just seems like its ASKING to test the elastic modulus of the steel being used.

Just looking at that picture is bothering me enough that I have to model it. I MUST know just how much these cuts affect the strength of the part!

Here I'm starting by importing the photo of the unnamed bicycle dropout into a modeling program, rotating it and scaling it correctly. Then I just draw the existing dropout shape in a 2D sketch:


Now, lets suppress the photo and extrude the basic dropout. Shall we assume it's 5mm thick?


Looks decent.

Okay, here I'm just copying the random swoopy crescent shaped cuts in our unnamed dropout. Looking closely, there is only one straight line. The absolute randomness of these cuts really makes my brow furrow.


...and the final cutout:


Looks horrible doesn't it?
Anyways, on to the testing.

The simplest way to do this, will be to anchor the two faces where the dropout meets the rest of the frame. Next I'm going to put a very slight axle groove in the top of the dropout so that the forces of the axle can REALLY be localized. (as opposed to applying force along the entire upper edge of the dropout) Remember, I'm trying to simulate an axle impacting this thing.


Okay, lets assume our Proj-B test rider weighs about 190lbs. If he hits an object (like a wheel swallowing pothole in the South Bronx) then the force on the axle is going to be several times his mass. We don't actually need to use any particular value here, because I'm going to use the same value to test the dropout with and without the fancy cutouts, but lets assume that the force is twice the rider's weight, thats 1690N being applied at the upper edge of the dropout

This program has a handy stress analysis tool that allows one to calculate the Factor of Safety (FOS) of a part. Simply put the FOS is the Material's yield strength divided by the equivalent stress at a point.

-An FOS less than 1.0 at a location indicates that the material at that location has yielded.
-An FOS of 1.0 at a location indicates that the material at that location has just started to yield.
-An FOS larger than 1.0 at a location indicates that the material at that location has not yielded.

So, for the Plain old dropout, and a 1690N force, we get a FOS of: 5.25102
No problem. I would ride this all day.

The Von Mises stress distribution on the model look like this:


Lets repeat that test for the Fancy Cutout version:


Here our FOS is 4.43389 That's 15% less strength!

These pictures show the model in a total deformed state, though thats not actually the case for these applied forces. The dropout will NOT deform under these conditions. The program just uses this to illustrate how the stresses are distributed.

So what can we tell from this?

Well, its certainly more colourful. You can see where the stress is concentrated in this last picture. That lower crescent and the little arrow head appear to be areas of concern. It seems the cutout dropout is only 85% as strong as the solid one. Whether or not that is 'strong enough' is entirely subjective. Much like my opinion of the aesthetic design of this particular dropout.

I started playing around, finding the maximum force before the material would actually deform. It seems the solid dropout could withstand a force of 9kN or 2020lbs before it would yield.. and even then, just barely:


When that same force is applied to the cutout version, we see a couple more areas of deformation. Most notably is that little pointy arrowhead tip again:



I guess today I've learned that fancy cutouts aren't really as bad as I thought they were. I've also learned how easy it is for me to get sidetracked into theoretical testing and hypothesizing simply by staring at a picture of a bicycle for too long.

If any of this bicycle's designers are reading, please don't feel too slighted by my words. (I didn't even touch upon your PBR bike!) I am only doing this because I wish i was doing what you are doing.

Mini Bike Winter IV

"What we're doing here, is having free fun. A lot of people don't like that. They'll tell you its dangerous." - Rev Phil

Zoobomb badass challenge, Start the games.

7 hours in a car will do strange things to a person.
It will make you want to ride your bike straight up a mountain in the middle of the night, in order to be the first to light an Olympic torch. It will make you get lost at the top of that mountain and ride around radio towers and cemeteries while yelling 'ZOOBOMB!?!?' into the cold air trying to find the torch lighting ceremony. Your lungs are burning, your legs are ripping apart. You see a familiar motorbike, you keep gaining altitude, through the fog. To the top.

Note that the end of the race is at the 5.8km mark.

At least I'm not the only Canadian to get lost on this mountain. Jeff managed to end up in Beaverton, and didn't get home until 5am, after checking every quadrant of Portland for his billet's house.

From the park at the top, we did a 'family bomb' with EVERYONE riding down at once. This was hilarious, as I was taken out by Simon's bike within the first 200m during a massive minibike pileup. I think he clipped Morgan's rear tryke wheel before going down. As soon as I hit the ground I went to fetal position and awaited the impending wheels. We all ended up with mini tire tracks all over our bodies. I'm not too badly rashed, but Simon took it in the face. I'm just glad he borrowed my helmet before the event.

Tired, and cold, we hit Voodoo Donuts where I had one that bore a striking resemblance to my last sprocket (hail Satan). Riding the sugar train late into the night, Shantastic led us over the Broadway drawbridge (no stopping or the Pepper will get ya) to Cap'n Fun's pad.

Roman Day

Organic Fair trade served in strange mugs and salsa containers met sleep filled eyes, under the North Portland sun. Bikes and chariots were tuned on Skidmore. A posse descended to the Undernook mostly via the bike routes, doing a quick mississippibomb along the way.

Slowly they came. The Dropouts, the Dead babies, the Sprockettes, the MC3, a film crew, and of course all of ZOOBOMB arrived at the undernook for breakfast. Dan managed the grille like he was a robot from Franz Bakery. He also had the smarts to bring case upon case of PBR to be sold. Let the games begin! A simulated Project-Bon's breakfast, consisting of speed-over eggs, hashbrown brickage, Avocrabo and PBR had me in the mood to get my hoon on. Morgman too. 540's and Project-Dorifto. The guy from Crankmychain took an interest in us, so that was fun. No Project interviews yet, mind you.

Drag races, in drag, dragging on cigarettes, and dragging a sled. Hilarious. Then the Chariot Whiplash. This made me cry I was laughing so hard. I didn't compete in these events, but had fun spectating, trying out Dead Baby bikes, and working on artistic cycling moves on minibikes. Sorry about crashing your Pink Pussy Rhiannon =D

After the events were over, we made a slow mass North along the waterfront through the Port-land. We hit a remote 7-11, and hundreds of bikers politely lined up to deplete their supply of alcohol. I got the last three sparks, but they were sugar free. The aspartame does make it taste kind of funny. Funnier than energy beer normally tastes.

Ahh, drunk in the sun. Where are we going?
After passing the Coast Guard property we hit a cul-de-sac where we were led down a path. I was at the front and inquired where this path led.

"Pirate town" someone said.

I guess the EPA lists this as a 'superfund' site due to the environmental damage from having industry here for so long. Derelict warehouses, obsolete piers, slippery ladders, holes in the ground. I started to feel bad about scoffing at the use of 'post apocalyptic' to describe the chariot battles earlier. This really fit the bill.

I did some exploring, skidded through the warehouses, and climbed the roof of what would soon become a violent battleground. Slowly I watched the convoy of deathcycles and chariots roll in. Cheers were shouted, horns were sounded. Tensions were high. No one knew quite what to expect. Before the battle I tried jumping the railroad tracks, and pinch flatted my back tire, denting the wheel too. I had brought a tube, but didn't feel like going through the hassle of removing the wheel/brake, and so I patched it and got the kittenchopper back together.

Out on the Pier, I met Cupcake, who wanted me to help him find wood to fashion a ramp to jump into the water. I declined his Cupcake challenge, unsure of what pilings and bacterial cultures awaited in the water 40' below.

The next half hour was a blurred roar. I've never seen such violence take place in the name of fun. Grown adults hitting each other with blunt objects. The crowd was screaming, empty beer cans were thrown at the gladiators. [As a side note, I don't think anyone was actually hurt during this event] When the dust settled, there was one gladiator left. Lost boy Jeff, who looked remarkably composed in his disheveled toga.

Cupcake then announced that he was starting his challenge. There’s a good shot of him flying towards the river on one of the flickr sites. As things wound down, someone mentioned that the Pepper were on their way down the road from the university [Possibly because Rabbit tried to jump on a passing train], so we mounted our steeds and started clearing out. We passed single occupant squad car after single occupant squad car. Must be a lonely job.

One would think that a simple roll out of the university would be okay after such an epic battle.. but no.
Someone went down on the bike lane. Our parties were split up and much confusion ensued. Who was hurt, who was waiting for who.. Where were Haley and Nick? I went back and found them, working on Haley's bike in the flashing lights of the fire truck. It seems her dropout had opened up due to the funky coaster brake washer setup. I BMX-tool'ed it back into shape on the curb, and got it rolling again, albeit without brakes. As well, Morgan flatted a tryke wheel, and was gangsta leanin to keep it movin.

Once the confusion was quelled, zoobomb Shawn directed us to a Mexican Restaurant out on Alberta and 20th. Pretty decent place, and the football match on the tele was in Espanola. Our next mission was to find Sparks, before the meetup to ride to the secret party spot. No problem. A corner store that had not been ransacked by bikers was found. I purchased Sparks Black, as I'm such a discerning Sparks connoisseur.

Thanks to Simon, we got to try the lower level bike path on the Steel Bridge, en route to the meetup spot. Pretty clever use of architecture if you ask me. Once we were there on the promenade, I let a few more Dead Babies try out my bike. It was then that I realized why my seat felt uncomfortable. Those heavyweights were bending my seat post!

Once again the Pepper showed up to monitor us (which everyone in Portland was completely used to), so we made our roll to the party spot. An emptied bike shop entitled 'The Recyclery'. If you were an animal, what kind would you be? A sleepy cat for sure. Curled up in a ball off stage. I've never really had a thing for furries, they're the deviants that even creep me out. Having said that, the animal themed fashion show was still pretty hot. Following that were performances by the Sprockettes and then Show me the Pink. I've got footage I should probably Youtube.

Riding home from the party was an adventure as well. Rhiannon and I found the Franz Bakery, where you can see the remarkable throughput of bread their machines are capable of, through large plate glass windows. We then met up with Turbo and his girlfriend, who led us back North under Lloyd centre, and up 14th to Gabe's.

Greek Day

Much slower. My hip hurts, my knees hurt, my calves hurt. I make the coffee and rouse the troops. We miss the Hostel brunch. Dang. Gabe and Shannon direct us to go eat on Belmont. I grab some Hookworms from Pol. We hit the Paradox.

We run into Cupcake on the bike route, and he asks us if we want to see something crazy. Coming from the guy who just jumped off a 40' high pier into questionable water, I couldn't resist. YES! We want to see something crazy. He walked us back to his and Dogeye’s place, where we saw the sweet Mad Maxx’d Ducati laid out in pieces on the ground. The steerer tube was sheared at the fork crown, but the frame looked okay. Sweet Cuppin Cakes then pointed at the gas tank.

"See that dent?"

"Oh Dear God."

Dogeye then leaned out the window and explained the accident. Upon impact with a car his junk was crammed into the gas tank. He provided the evidence. That image does not need to be documented to be remembered. I still want a motorcycle though.

We got to the games and I was already feeling beat. "I should have trained more on this sled" I thought, as I swapped the good tires on, to replace the bulging corded stroller tires I had been skidding through. This day is a bit hazy. I wasn't drunk or anything, but I just kind of zoned out and watched the action. I tried out the harness, and tested the sturdiness of the ramp.. but that’s about it. Then I went for coffee at Tiny's. There was about 5 bikes out front. 3 of which were ghetto single speeded. Is this what a Vancouver bike rack will look like in a year? Probably not.

I couldn't take the trip to Freegeek and more socializing, so I went back to Gabe's for a nap. Rhiannon gave me a wonderful massage that put me right out. I awoke with just enough time before the race to load up the car with the bikes.

Geared up and ready to roll, we waited at the Pile. I was nervous, I'll admit. Maxxed up for the first time, hanging my bike on a hook..

How many Zoobombers can you fit on the Max?

One more.

N+1

At the top Rev. Phil gave us a briefing, and then we headed to the road to start the race. The mini class was to go last, so I rode up the hill a bit to warm myself up. I lined up at the start, foot on crank, ready to push. A count down from ten, then we hit it. I blasted out from the gate in about 5th place, and quickly muscled my way up to third.

Getting up beside Gabe I gave him a quick 'Sup G fresh?!' greeting to let him know I was going to have fun with him on the way down. I turned on my front blinkie so he would see me flashing in his peripheral the whole way. This is where it got fast. I guess Gabe is used to spinning those short cranks, because they were a blur. I mimed his body language around each corner, snaking his line, and got my sprint on at the same times he did. His tuck style was tight though, and I couldn't compete with that lack of frontal area, even with my hands on the cross bar.

I was in second now. I just have to stick on him, then attack after the last sharp corner. Which one was it? Aren't we near the bottom?

We did the last big right hander and Gabe started to hammer. SHIT! that was the one! I was sprinting as fast as my 175s with BMX flats would allow, and had almost caught up by the time we hit the crosswalk.

Second place. Not bad for my second Bomb ever.
This was probably the happiest I had been all weekend, as I was just relieved to survive the race. The events of the weekend spun in my head over and over. Is this much free fun really possible?

We headed back up the Max to do the Kingston bomb.. which was the route I originally took up the mountain on Friday. That was a pleasant slow roll to Legoland. The site of the final Minibike games. We were all pretty faded, and had to accept the fact that we couldn't stay in Portland forever. It was best to roll out then.

The trip back was pretty good too. I drove until my eyes decided not to focus, then handed over driving duties to Morgan while I passed out in the back cuddling Haley. Rhiannon did a bang up job of not letting Morgan doze off, despite her babbling about hexidecimal notation.

"Oh.. flashing lights. Morgan is getting a ticket" I thought as I woke up.. Morgan was confident he wasn't speeding though. I think it may have had something to do with my winter tires being the wrong diameter, and knocking the speedo off a bit. Either way, the trooper just ran our tags and let us go off into the night..

..and before I knew it we were back in Canadia.
Back to life, back to reality.

I would like to thank EVERYONE who helped make this weekend possible. If you are ever in Vancouver, I will strive to show you the best time on two wheels I can.
Thank you so much, Zoobomb.

I didn't include many pictures or videos in this post, as there are already a billion of them floating about on the net.

Here are some handy links:

Gabe's Flickr

DennyT's Flickr

Butterbits' Flickr

Dumptruck's Flickr

Bikeportland's Flickr

Dontbecreepy's Flickr

Nag Mike's Flickr

Haley's Flickr

..and Simon's youtube footage:

I need a weekend off.
St Valentines race on the kittenchopper? Think I can place?