April 2007 - Posts

A different way of measuring while bending tubing

Yesterday I made my second small front rack top and it was the second time that I had trouble with the measurements for bending tubing (using a lever-style bender).  While sitting down with a piece of scrap and the bender I figured out an alternative way to compute bends. 

Swagelok has a the best manual for lever benders that I've seen. The information is good for any brand of lever bender (I have two benders, neither is made by Swagelok).  Starting at page 13 there is a discussion on the gain calculations for figuring out where to place bends for making a polygon.

I've had problems with the Swagelok method of computing gain because a small mistake anywhere in the process can cause problems elsewhere.  Yesterday I made either a computation or measurement error and made one bend 1/2" earlier than I should have.  I ended up splicing two pieces together to recover.  Since the Swagelok method has you map out all bends before you start any small errors at end bend will compound. 

I figured out an alternative that is easier for me to use.  Instead of marking only the end of a bend I'm marking both the start and end of each bend and measuring the straight section of rack between the bends.  Using the bender radius I can compute the desired lengths of the straight sections.

In this example I make a roughly 5x7 rectangle (good for a handlebar rack) out of 1/4" tubing using the Ridgid 404 bender.  It has a 5/8 radius.

For a 5x7 rectange the long straight sections would be 7-(5/8)-(5/8) = 5.75" and the short sections would be5-(5/8)-(5/8)=3.75".  To make life a little easier I rounded these up to 6" and 4".  The rack will be 5 1/4" by 7 1/4", which is still a good size.

Using the radius of the bender I can compute the circumference of the bend that I'm making.  For a 90 degree bend it is (pi*2*r)/(360/90).  r is 5/8, so this gives me .98". 

The Process:

 

In this example I'm going to put the seam along in the center of one of the ~5" sections.  So I measure 2" from the end of the tubing and draw a line.  .98" from that line I draw a second line.  To bend I align the first line with the 0 point on the bender.  After a 90 degree bend the second line will mark the start of the new straight section.



I continue this process working around the rack.  This photo shows us at the halfway point.



At the final bend I do the same thing, but I also do something else to check my work.  Using a square aligned with the center of the first piece of tubing I draw a third line in between the two normal ones.  I put a S through it (square) making a $ sign.  You can just barely see this in this photo, but it is clear in the next one.

The $ line will line up with the 90 degree mark on the bender:

 

I cut the tube to 2" past the last line and bend:

 

Here is the final product:

 

It is about 5 1/4" across (center to center).  We used 4" straight sections and the bend radius is 5/8".  4" + 5/8 + 5/8 = 4 10/8" or 5 1/4".

You'll notice that I never had to measure any fractional numbers except for the bend circumference.  I set your calipers up to the bend circumference and locked them in place.  This let me use the ruler for the straight line measurements and the caliper for the bend marks.

The same technique should work for non-90 degree bends, you just need to figure out the circumference of the bent area.  The formula is simple: (pi*2*r)/(360/degrees).  So a 60 degree bend with a 5/8" bender would be (pi*2*(5/8))/(360/60) = .65 (or 21/32nds).  I'm going to be building some front lowrider racks with trapezoidal shapes next and will use this technique there.

Posted 30 April 2007 02:37 AM by AlexWetmore | 5 comment(s)
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Re-raking forks for low trail

On Sunday a group from Point83 got together at a local bikeshop and re-raked some forks.  Val Kleitz (used to own Bikesmith and bike mechanic extraordinaire) was there for a couple of hours to lend some advice. 

The goal of re-raking the forks was to add additional offset to decrease the bicycle's trail.  This improves the bike's handling when riding with a front load, even a small one like a handlebar bag.

I brought 4 forks to re-rake:

1) A Jamis fork that was supposed to be disposed of anyway.  It was built about 1.5cm too short and replaced under warranty.  I did this fork first because I didn't care what happened to it.

2) A 1986 Trek 400 fork.  I've been trying to sell this at the Seattle Bike Swap for $5 or $10 for the last 3 years with no interest.  I don't own the frame that it was on any longer.  It will have cantilever bosses installed for 650B and available as a low-trail demo fork to friends.  It is already too short for 28mm wide 700C tires with fenders.

3) A 1983 Trek 630 fork.  This fork has 25,000 miles on it and needs to be repainted.  I reraked it the least, changing the offset from 10mm to 20mm.

4) A 1994 Bridgestone RB-T fork.  This is from my RB-T, one of the ugliest in existance due to being touched up at random spots with purple nail polish by a previous owner.

Point83 and BOB list member Andre also brought a early Trek mountain bike that he was using as a load hauler with a large Wald basket.  He wanted to re-rake this bike's fork to have a trail of around 40mm for carrying heavy loads.

We primarily used two tools to re-rake the forks.  A Hammill fork blade bender was used to increase the offset in each fork's blade.  This bender has a radius of 10".  Using the fork leg bender does take the fork out of alignment, so we used a VAR fork alignment jig to realign the fork after getting to our target offset.

Val showed us a great trick for checking fork offset.  Draw a line on a sheet of paper and place the fork on the paper with the dropouts aligned along that line.  Use an angle finder (or bubble level) to hold the fork's steerer tube at 90 degrees.  Now look down the steerer tube of the fork and down a line on the paper along the center of the steerer.  This is easier and more accurate if one person holds the fork while the other looks through the steerer.  If you measure that to the reference line for the dropouts you'll get the fork offset.  I checked this with two forks that I knew (the published) offsets for and the results were accurate.  Andre drew this great drawing that shows how it works:

The bending worked for forks with no canti bosses or canti bosses set for 700C wheels.  When we tried to bend Andre's 26" MTB fork we found that the canti bosses were placed too low and ran into the mandrel of the bender.  This fork was re-raked using a Park leverage tool.

Even bending with a normal radius the fork height didn't change too much.  It was pretty easy for me to measure the Jamis fork (I had a reference wheel/tire which just barely fit before) and the dropout to fork crown changed by about 3-4mm when we increased the fork offset by 20mm (going from 45mm to 65mm).

This photo shows a stock (in grey) 1983 Trek 600-series sport touring fork and a re-raked one (in gold) which has had 10mm of offset added to it. 

With these two photos you can see that the tire clearance did not decrease too much when adding rake to the fork.  The tire is a 700x35 Panaracer Pasela, larger than what I'd use with these bikes.  Tom Matchak's article on re-raking gives you the math for figuring out how much the fork length will be reduced through re-raking.  Note that his measurement is along the steerer and overestimates the amount of clearance lost in most cases.

Posted 25 April 2007 04:04 AM by AlexWetmore | 2 comment(s)
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Office Chair Racing

Last night Christine and I went and watched a bunch of folks race Office Chairs down the hill behind the Seattle Times.

All photos here.  I learned about it from the point 83 forums.

Enough text -- here are the good photos:

(no cars were harmed in the making of this photograph -- oh well)

That is a Bakfiets from Clever Cycles.

 

Posted 21 April 2007 04:49 PM by AlexWetmore | no comments
Our experiment as a two car family is over...

It started in June 2002.  Christine and I needed a new car.  At the time I didn't know how to drive, so we sold her Honda Civic and bought a diesel VW Jetta Wagon.  That car was the most expensive item that I had ever purchased besides my house or education, so I thought I should learn how to drive it.

Learning how to drive gave me a new sense of freedom.  I know that is a common reaction, but I didn't think it would be my reaction.  I didn't care about using the car to get to work, but it gave me the option of going hiking (without Christine) or going to visit friends in Olympia or Missoula much more easily than I could in the past.  The two of us shared the single car for about 6 months before I bought my own car in Feb 2003.

The funny thing is that I rarely used my own car as intended.  Sure, I did drive out to Missoula or Olympia a number of times while owning it.  I don't think that I ever used it to go hiking (without Christine).  I did use it for a few bike rides.  Mostly it got used to get to work.

Yes, I drove to work.  For a year.  I did it so much that I actually sold the Jetta and bought the car that I really wanted, a VW Golf TDI.

After a year of driving to work (it was now Jan 2005) I looked back and realized that I didn't really like driving to work.  I had to deal with traffic.  Sometimes it was faster than taking the bus, but only if I left really early.  I missed talking to friends on the bus and having different routes every day.  I missed being on my bike every day.  In driving I learned a million ways to avoid SR520 (the highway between home and work) that I really didn't need to know.

So in Jan 2005 I decided that I'd only "allow" myself to drive at most once a month.  That was easy and it turned out that I drove to work about 10 times in 2005.  In 2006 the number was even lower.  I was getting tickets from the Seattle of City because my car never moved.  I started to think about selling the car.  It was a hard decision -- buying this car was complicated and involved a few sleepless nights and a cross-country drive in the middle of December.  It's hard to sell something that you were so invested in acquiring.  I also see the car is not being replacable -- used TDI prices are just too high right now for me to justify another one.

In the first 14 weeks of 2007 my car only drove 180 miles.  That is just over 10 miles per week.  When Christine and I looked at this number it was obvious that the car needed to go.  So last week the car went in for a detailing and was listed on craigslist.  TDIs are popular (and I knew this) and it instantly got a ton of interest.  The second looker was serious, had it inspected by a mechanic yesterday, and is buying it today.

I'm looking forward to going back to being a one car family.

Posted 17 April 2007 04:55 PM by AlexWetmore | 1 comment(s)
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Comments are fixed

I just discovered that people have left dozens of comments that I needed to moderate.  Sadly there were dozens of other bits of comment spam (there were 123 unmoderated comments total).

Anyway, the non-spammy comments are unleashed and I'm slowly going back and reading them.

I'll figure out how to get notified when new comments come in so that I don't sit on them forever.

Posted 17 April 2007 04:43 PM by AlexWetmore | no comments
A variety of ways to mount a headlight to a bicycle rack

I spent some time on Saturday experimenting with different headlight mounts on my bike racks.

This is the first attempt.  It is just a M5 eyelet on one of the rack stays.  Nitto uses something like this on the M12:

It's a basic but functional solution.  The small piece of flat stock gives one a lot of options for where to actually put the light.  It looks pretty ugly though.  The best part about the light mount on this rack are the three loops for managing the front cable.  No zipties here!  They are made from rollers pulled from a worn out bicycle chain.

On my convertable Porteur Rack I played with two different options.  The first (no light mounted to it in these photos) is a pretty basic design that is easy to make.  I just used some 5/16" tubing with a perpendicular piece at the end for the light's mounting bolt. 

I also need a mount on this bike which is farther back so that it doesn't interfere with the front wheel hook on a Sportworks bus-mounted bicycle rack.  I thought of a nicer and more simplistic option here.  I used the shaft from a nail (about 3mm in diameter) and put a 5mm eyelet on the end of it. Minimalistic and functional, I like it.

While I had the torch out I filled in all of the vent holes on my front rack with small nails and brass.  That was a lot of work, but now there is no way for water to get in:

Posted 16 April 2007 01:14 AM by AlexWetmore | no comments
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The environmental downsides to mail order

During the last few months I've been thinking a lot about my shopping habits.  I tend to do most of my shopping with local retailers, but I also do a fair amount of mail order.  Some of this mail order is for items which I can't get locally (for instance the item is rare and made in a remote location), but the vast majority of these items are either stocked locally or can be special ordered by a local retailer.

When people talk about shopping locally they usually cite the benefits to the local economy and the personalized service that one gets from smaller retails who are focused on a specific region.  These issues are big and have been the primary draw for my local shopping over the past few years.  For instance my wife and I buy most of our music from a small music store called The Landing.  It has a small number of employees and one of the two owners are often there.  The owners live in our neighborhood and so much of the money gets spend here again.  They know our musical tastes and make musical recommendations when we shop there and stock the types of music that we like.  We can listen to any CD that we'd like on their customer listening stations (a couple of CD players with high quality headphones).  All of these things make the shopping experience very enjoyable and are more important to me than price (although I think that their prices are competitive).  I have similar relationships with my video store, bike shop, grocery stores (although my primary grocery store is a national chain), farmer's market, and other places that I shop day to day.  These are the obvious benefits of local shopping and ones that are commonly discussed.

Another option for me to buy CDs would be shopping with Amazon.  Amazon also provides a reasonably nice shopping experience due to the reviews available on their website.  I can't listen to as much of the music as at my local record store, but I can listen to 30 second selections of most tracks.  When I buy from Amazon some of the money is going back into my greater community (but this is only true because both Amazon and I are located in Seattle), but it isn't going into my immediate community.  I don't get the personal attention from Amazon that I get from my local record store, although they do have software that tries to make it feel like I'm getting personal attention.  The prices are about the same because Amazon's prices are cheaper, but I have to pay shipping (or wait a long time).

One of the big differences in shopping with Amazon vs shopping at The Landing are how items are delivered.  They both have the same selection (because The Landing can special order items from the same distributors that supply Amazon).  However when I order a CD or two from Amazon they come direct to my house.  When The Landing orders a CD for me it comes in a box with dozens of other CDs to the store.

Shipping 25 CDs to a single store and having 25 people pick them up from the store has a smaller environmental footprint than shipping 25 CDs to individual houses.  The packaging per CD is much smaller when you pack 25 of them into one box than when you use 25 boxes, one per CD (especially with Amazon packaging which tends to use much larger boxes than necessary).  A UPS truck delivering 25 CDs to a business requires a single stop where delivering to 25 residences typically requires 25 stops.  If the shop is in a commercial area (as The Landing is) then it probably can make a single stop to deliver packages to multiple stores.  It is less common that multiple neighboring houses will receive packages on the same day.  A UPS truck may take a couple of hours (idling or running the whole time) to deliver packages to those 25 houses.

Some of this gets even more interesting when you look at purchasing more unique items from retailers that are far away.  In an extreme example I could decide to purchase Ortlieb bicycle panniers from an east coast shop (because they are slightly cheaper).  The distributor is located in Kent, WA (about 20 miles south of Seattle).  The panniers are made in Germany.  So if I purchased the panniers from an east coast shop they would travel from Germany to the distributor in Kent, then back to a shop on the east coast, and finally back to me in Seattle.  Those panniers would have travelled well over 10,000 miles before ever being used and 6,000 of them would be inside my own country to save a small amount of money.  In the greater scheme of things I think that it is more beneficial for myself and my community if I am less price conscious and more aware of the route that the item takes to get to me.

I'd love to have numbers on how much fuel is consumed in the shipment of a single package by ground across the country.  I'd also like to know what percentage of package deliveries are going to businesses vs homes.  It might be possible to estimate the extra fuel consumption for mail order packages using this data.

If anyone knows of any more detailed analysis in this area please let me know.  I'll follow-up here. 

Posted 11 April 2007 06:24 PM by admin | 10 comment(s)
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Critical Mass -- March 2007

 

This was my second Critical Mass ride.  The first was in July 2006, a month after illegal arrests on the June 2006 ride.  July 2006 was a huge ride with hundreds of riders (maybe 500) and a supportive police escort.  I knew that one wasn't typical so I thought I'd go again.

For years I've been anti-CM without having gone on a ride.  In July I learned that the rides are tons of fun.  Friday's ride was great fun too.  It's a massive celebration of bikes and bike culture.  All types of cyclists come out.  My favorites are the ones who do something extra to their bikes for the event:


Sebastian was pulled 15 miles or so in this trailer and provided refreshments to those in need.


Human powered music on a human powered ride.  Another group brought out a sound system and hauled it on a trailer behind a tandem.

The celebration is great and bigger than the ride itself.  We did ride (loop around downtown, Elliot/15th out to Ballard, ending at Gasworks), but the route isn't what was important.  I think that the public is startled, amused, and generally sees fun when they see a huge collection of folks riding down the road, playing music, talking, and having a good time on bikes.

I'm not as keen on the traffic blocking aspects.  I don't think it helps with the message that I want to send (bikes are fun and practical means of transportation) when CM blocks intersections and prevents other forms of traffic from getting through.  I like the idea of a mass and don't like seeing it break up, but I also like traffic controls and don't want to send the message that cyclists should ignore them.  Part of me would love to see a different type of CM where traffic laws are obeyed and the group naturally breaks up and rejoins at different places around the city.  Maybe it would work, maybe it wouldn't.  CM is well established and I like most of what it is about.  I'm going to embrace those aspects.

I'll be there next month for the party.  I hope to see you there too.

Many more photos.

Posted 01 April 2007 05:20 PM by AlexWetmore | 6 comment(s)
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