Yesterday I took a Sunday ride on the bakfiets, up to a regional Upper Valley/New Hampshire/Vermont Sierra Club meeting in Hanover. It was sunny with cool air and fair weather clouds, and the meeting was from 1-5 pm, so the meeting was a great excuse for my first longer ride of this year. I thought the trip stats from the Cycle Analyst data logger would be interesting to others:
Distance: 40.75 miles
Elapsed time: 2 hours, 30 min, 5 sec
Average speed: 16.2 mph
Maximum speed: 42.7 mph
Volts, start: 41.6 (this is a 36 volt system)
Volts, end: 39.4
Volts, min: 35.9
Amps, min: -0.02
Amps, max: 17.08
Energy used: 509.58 Watt hours (13.63 Amp hours)
Watt hours per mile: 12.5 (equivalent to 2640 mpg)
A few notes to help interpret the numbers:
-The Cycle Analyst measures any time the wheels are turning.
-The route was mostly two main roads (Rte 5 and Rte 10), with 6 notable hills that are about 0.6 to 0.75 mile long. I haven't measured the grade on them like I did for my road, but they could roughly be considered "San Francisco" hills. My speed is 12-14 mph up the hills, and the maximum speed of 42.7 mph is coasting down one of the hills.
-The CA also lists Amp hours forward (13.646), and Amp hours regen (0.0105). This bike has a gear drive motor with a slip clutch and cannot do regen, the small amount of back current is from the collapsing magnetic fields in the motor coils when the throttle is turned off. The longtail being built right now has a direct drive motor and can do regen, and I'm looking forward to comparing the numbers.
-I use the EPA standard of 33 kWh per gallon of gas for conversion to mpg.
-13.64 Amp hours is 68% of battery capacity (20 Ah), so the range works out to 59.8 miles, not counting the solar generation.
Solar contribution:
This is not directly measured yet, and has to be calculated. I have some shunts to put in the solar wiring, but haven't had the time to install them and go through the process of checking the calibration and then the scaling. However from testing I know that the plug in battery charger is about 85% efficient, and thus the 509.58 Watt hours recorded by the CA should have taken 599.5 Watt hours to recharge. But when I plugged in the battery after the trip my Kill A Watt meter recorded only 470 Watt hours during charging. The difference of 129.5 Watt hours would have been provided by the solar panels, which is 25.4% of propulsion energy, or 21.6% of total energy counting battery charger efficiency losses.
The regen is measured by the CA because it feeds back to the battery through the motor wiring, but the solar generation is a separate set of wires and not measured. The solar 129.5 Watt hours would have been good for another 10.4 miles of range, but since I didn't travel the extra distance it shows up as a fuller battery at the end of the trip.
All in all it was a fun ride, traffic was very nice, the weather was great. I've been riding only short 15 mile trips to the center of town once in a while, so the electric assist was a big help. I wore regular street clothes for the meeting, and my legs are 99% normal after the longer ride. I'd do it again.
-----------------
Unrelated to the statistics from the trip, here is an interesting video. Jack Kerouac (author of On the Road) wrote a letter to his first wife, Edie Parker, about 10 years after their marriage had been annulled, while he was discovering Buddhism. Film director Sergi Castella and film maker Hector Ferreno made the letter into a short video for Dosnoventa Bikes- We were never born:
WE WERE NEVER BORN from Dosnoventa on Vimeo.
Monday, June 23, 2014
Tuesday, June 17, 2014
Bicycle safety, Round 2
I thought that my earlier blog post about Helmets and Safety would cover bike safety for the purposes of building and testing a few bikes, but safety keeps coming up while I'm out with the cargo bike talking with people, and is proving to be a major issue. This isn't logical- we associate biking with young kids, but then feel it isn't safe for mature adults. Safety is turning out to be a long row to hoe, so it seems like I should write down some of the things I've had conversations about.
First, a graph:
Bekka Wright of Bikeyface.com echoes what I tried to make clear in the Helmet blog post. Helmets don't have magical powers, and there is much, much, more that is more important than a helmet in staying safe on a bike. You don't put a helmet on inside a car and then expect to be safe if you drive badly. People who are concerned about biking safety (and pedestrian, child, senior, handicap, and neighborhood safety too) should spend their energy on driver training, awareness, and infrastructure. Safety is an action that all of us have to put there.
Roads have been a commons through out most of human history, and only in the last 100 years have they become subservient to the automobile. Cars, light trucks, and buses probably reached 1 billion globally in late 2010 (http://wardsauto.com/ar/world_vehicle_population_110815), but bikes had reached 1 billion globally somewhere a bit before 2000 (http://www.worldometers.info/bicycles/). The gap has only gotten wider, as car and bike annual production was about equal up to 1965, but in the last 3 decades there have been twice as many bikes produced as cars, and the trend seems to be growing, (World Watch Earth Policy Institute, see my earlier Helmet and Safety post for a fuller discussion). Bikes by all rights should be getting more infrastructure dollars, but for most countries this has led to public policy arguments and political funding fights instead.
BIKES vs CARS TRAILER from WG Film by Fredrik Gertten. (http://www.bikes-vs-cars.com/)
"This is not a war. It's a city. We should live together in peace."
At an International Transportation Forum in Berlin on June 6, 2011, B.K. Chaturvedi, member of India's Planning Commission told the 800 delegates: "We in India need to provide more roads and rail. Cycling is a miniscule thing. That's not the future." Asian countries expressed the same sentiment for their developing economies, (http://www.ipsnews.net/2011/06/bike-vs-car-on-a-hot-planet/).
The Oregon Department of Transportation has released a good study of the effectiveness of bike lanes, Lessons from the Green Lanes: Evaluating Protected Bike Lanes in the U.S. and they find them to be very good for safety and perceived safety (i.e. convincing more people to bike). This is a good report, and I love the graphics.
Here is a series of 4 very brief videos about changing infrastructure, speed limits, numbers, and the overall health benefits from cycling being 20 times greater than the risk from accidents and air pollution:
There isn't enough money to extend infrastructure to all the roads in Vermont and it is a slow process, so I think I have to work with the roads we have. I do think the infrastructure that we have in urban areas does indirectly benefit rural roads, because auto drivers get reminded there are bikes on the road. However if VT AOT could fund more bike infrastructure that would be great.
My last option is making bikes work better on existing roads. I admit I am a bit biased towards the bikes I am building, because their capabilities enable me to mesh with traffic flow better than a typical sporting bike. This can be good (easy for me), or bad (it enables a transportation system built for only cars, and it doesn't do a thing for other bikes).
Did I mention helmets?
Last week my friend Charis posted the question: "Does anyone have favorite stats / readings / sources about bike safety?". A few of the replies were:
http://massbike.org/resourcesnew/bicycle-statistics/
http://www.mrmoneymustache.com/2013/06/13/bicycling-the-safest-form-of-transportation/
http://nhts.ornl.gov/
http://nwurban.wordpress.com/2010/12/20/cyclings-impact-on-life-expectancy/
http://bicyclesafe.com
One of the most insightful replies was posted by Adonia Lugo related to her transportation equality study, Planning for Diverse Use/rs: Ethnographic Research on Bikes, Bodies, and Public Space in LA:
"Bicycling is legal on city streets in the United States. No laws keep motorists in their cars. This is not a situation where people's everyday practices have been disrupted by state apparatuses that govern through direct force, such as military police or an invading national power. And yet, an estimated 33,885 people died while using streets in the United States in 2009, according to the National Highway Traffic Safety Administration (2010). Of that number, 4,280 were pedestrians and 618 were cyclists, which means the vast majority of that estimate refers to dead motorists and their passengers. In the same year, an estimated 2,239,000 people were injured while using surface streets and highways. Bike advocates frame these injuries and fatalities as a design issue- with street infrastructure designed specifically for cycling in place, fewer people would drive. Instead of taking the built environment's role for granted, I chose to consider that this might be a case of discipline, the 'internalization of standards that are then enacted through bodily compliance.' (Foucault, 1977)"
I just spent a day as part of the Strolling of the Heifers parade in Brattleboro, and the following (cargo bikes) Bicycle Petting Zoo. I'm planning on writing a post about the event, but want to mention here that while I was talking to people about bikes during the afternoon, bicycle road safety was the third most common topic, after questions about first- the solar electric cargo bike I was standing next to, and second- the unusual concept of using a bike for work purposes. (The timing of this post is mainly because of those conversations.) We are a very car centered culture, and even for those who are willing to try, it is hard to see an option different than cars. There is a fair amount of uninformed fear, and also overprotective helicopter parent syndrome. The simplest change I'd make about the safety question is to reframe it as the chance of being injured in a car or on a bike, not solely about being injured on a bike, to acknowledge that you can and often do get hurt very badly in a car. But there are many other larger questions for me about the trade offs we make to be in a car. There are two other negative habitual internalizations beyond Adonia's "standards that become bodily compliance". First, we all use our childhood as a reference for the state of the world, so we do not easily see the cumulative changes that cars have done to us, our society, and our environment over a hundred years. Second, we internalize the power of a car as our own power. We deny the reality of our bodies, and expect super human capacity to be normal. Our relationship with our surroundings has become abnormal. It is part of our psyche to use tools, but it seems like it is time to question our all consuming dependancy on the auto.
After the Bicycle Petting Zoo I had to ride to the other side of Brattleboro, and the best route was through the center (1.4 miles) on downtown roads with continuous parked cars. With the electric assist on the bakfiets I was able to travel as fast as the cars (25 mph), with the cars accelerating away at the stop lights and then I'd catch up in a couple of hundred feet. I rode in the regular travel lanes like a motorcycle. (To some extent bikes like this make the need for bike lanes superfluous, but the catch is still taking care of all the other bikes that can't travel this fast.) The only problem was climbing the uphill out of the center with a one foot wide shoulder before the curbing. I stayed as far right as I could, but a small sedan behind me at the light just had to pass. It was pitiful, as he had the accelerator floored and wasn't traveling much faster than me, and then I had to stop and wait for him to turn at the next stop sign. He had a large error from his car centered view of the world but could not see it, and I had to deal with it.
Cars were truly amazing inventions of human creativity when I was a kid in the 1960's, and I still think some car driving is very special. But with increasing Vehicle Miles Driven per capita, I have watched them become an appliance, a unit in traffic. (You are not stuck in traffic, you are traffic.) I would argue that they have moved beyond the obesity, diabetes, heart disease, pollution, asthma, sprawl and environmental degradation linked to car use, and have now become a retreat from connection with the world around us and our thoughts. This should be enough reasons to use a car less, but most people will not be able to make a change.
What is risk? Is the limitation of risk such as envisioned by conservative financial investors and military advisers really applicable to bicycle riding? Is not walling off part of life a sign of decline? I'd like to end this post with a bit of philosophy. As Martha Nussman states about Euripedes' play Hecuba in the second half of this discussion with Bill Moyers, a life without openness, without trust, without risk, is not a human life:
"This says something very important about the human condition and ethical life, that it is based on a trust in the uncertain and a willingness to be exposed; it's based on being more like a plant than a jewel, something rather fragile, but whose very particular beauty is inseparable from that fragility." Wrapping ourselves in a 3000 pound steel cocoon and telling ourselves that we are safe is a deception. Driving a 40 mile commute everyday at 65 mph is a distortion of reality. The everyday actions that we take- often just to get by- are what actually creates our world. How deeply do we wish to live?
First, a graph:
(Click on images to enlarge.)
At the beginning of April, Greg Raisman of the Portland (Oregon) Transportation Department gave a talk for Boston Health Associates about the effect of speed on the severity of accidents. (The second speaker Barry Keppard, Manager of the Boston Metropolitan Area Planning Commission, Public Health Division, talked about the effects of lowering traffic speed, which parallels the efforts of bike advocates in NYC to reduce speed limits on side streets to 20 mph.) Greg showed a most excellent graph (above) on Fatality Risk versus Collision Speed. I had struggled with these statistics while writing my Helmet blog post, because I knew that an electric bike was faster, but the best data for estimating the increased risk that I could find were simple bar graphs with only two or three bars- not very good for communicating to others who are thinking about traveling faster on an electric work bike. Greg's graph is from a presentation that P. Wramborg gave at a road safety conference in Warsaw in 2005. Looking at the "Pedestrian or Cyclist" curve on the left, the (unprotected) human body does a really good job of surviving a crash up to about running speed (12-15 mph), and then from 20-25 mph the curve becomes a threshold, above which the risk of dying increases very quickly. When I started this bike project a couple of years ago I had been thinking of 40 mph speeds between towns to make using a bicycle more feasible for errands, but after a year of measuring elapsed times I've realized that the average speed matters as much as top speed. My car may top out at 50 mph for several miles of my trip to White River, but most of the trip is at slower speeds with stops, and the car's average speed is actually only 26 mph. A consistent 20 mph on an electric bike would be significant. I now think these are feasible design speeds for future bikes:
-50 mph- is over the top and becoming a moped
-40 mph- upper limit, since I already reach 42 mph coasting downhill on the bakfiets
-30 mph- electric motor plus strong pedaling, (note that you cannot do this with a pedelec system which turns the motor off above 20 mph.)
-25 mph- I often reach 22-25 mph with moderate pedaling on the bakfiets.
-20 mph- the federal speed limit for bicycle motor assist "when powered solely by a motor, of less than 750 watts (1 h.p.), on a paved level surface with a 170 pound rider" (HR 727 Consumer Product Safety Act, Section 1).
-5 to 15 mph- standard Oma (upright) commuter bike speed, and the speed I ride my bakfiets in closer quarters.
I now like a design goal of 30 mph for the intermittent open stretches of the trip (and downhills) to raise the average speed and increase bike use feasibility, with a 750 watt motor for my steepest hills that I can't ride up right now with 500 watts. The usual traveling speeds should end up below the greatly increased chance of injury, and it will be legal (remember I hand these bikes off to other people). FYI- you'll note from the other two curves in the graph that being in a car increases the speed you can survive by about 12 mph for a side impact, and another 12 mph for a head on collision, which is not a lot considering all the safety equipment in a car.
Update added on July 21, 2014: California does not allow electric assist above 20 mph:
Item 3 of California V C Section 406 states: "Is incapable of further increasing the speed of the device when human power is used to propel the motorized bicycle faster than 20 miles per hour."
A second safety item was a great drawing by Bikeyface:
Roads have been a commons through out most of human history, and only in the last 100 years have they become subservient to the automobile. Cars, light trucks, and buses probably reached 1 billion globally in late 2010 (http://wardsauto.com/ar/world_vehicle_population_110815), but bikes had reached 1 billion globally somewhere a bit before 2000 (http://www.worldometers.info/bicycles/). The gap has only gotten wider, as car and bike annual production was about equal up to 1965, but in the last 3 decades there have been twice as many bikes produced as cars, and the trend seems to be growing, (World Watch Earth Policy Institute, see my earlier Helmet and Safety post for a fuller discussion). Bikes by all rights should be getting more infrastructure dollars, but for most countries this has led to public policy arguments and political funding fights instead.
BIKES vs CARS TRAILER from WG Film by Fredrik Gertten. (http://www.bikes-vs-cars.com/)
"This is not a war. It's a city. We should live together in peace."
At an International Transportation Forum in Berlin on June 6, 2011, B.K. Chaturvedi, member of India's Planning Commission told the 800 delegates: "We in India need to provide more roads and rail. Cycling is a miniscule thing. That's not the future." Asian countries expressed the same sentiment for their developing economies, (http://www.ipsnews.net/2011/06/bike-vs-car-on-a-hot-planet/).
Photo credit unknown, probably in Oregon at a festival.
China is accelerating development of Electric Vehicles, but this is still bad news for resource use, congestion, and making real connections. To me increasing the number of cars is pretty much Planet Down the Tubes material. This is too big to be my fight, so I'm looking for what I can do here and now.The Oregon Department of Transportation has released a good study of the effectiveness of bike lanes, Lessons from the Green Lanes: Evaluating Protected Bike Lanes in the U.S. and they find them to be very good for safety and perceived safety (i.e. convincing more people to bike). This is a good report, and I love the graphics.
Here is a series of 4 very brief videos about changing infrastructure, speed limits, numbers, and the overall health benefits from cycling being 20 times greater than the risk from accidents and air pollution:
"The benefits of cycling outweigh the risks by 20 to 1."
From the Cycling, Health, and Safety working group report
There isn't enough money to extend infrastructure to all the roads in Vermont and it is a slow process, so I think I have to work with the roads we have. I do think the infrastructure that we have in urban areas does indirectly benefit rural roads, because auto drivers get reminded there are bikes on the road. However if VT AOT could fund more bike infrastructure that would be great.
The three foot minimum passing distance rule. Photo credit: Kent Schram
Education (and repetition, repetition, repetition of it in an engaging way) are needed for all road users about how to interact with each other. I'm learning about riding for myself, and hope that agencies will spread information to other road users.My last option is making bikes work better on existing roads. I admit I am a bit biased towards the bikes I am building, because their capabilities enable me to mesh with traffic flow better than a typical sporting bike. This can be good (easy for me), or bad (it enables a transportation system built for only cars, and it doesn't do a thing for other bikes).
Did I mention helmets?
A bicycle helmet cannot do this, but it doesn't have to either.
Bicycle speeds are much slower. Photo credit: unknown
Commuting on a work bicycle is not the same thing as racing on a high power motorcycle.
This is what commuter biking looks like. Tram, pedestrians, bikes, and cars.
Photo credit: Unknown (location probably northern Germany)
More of what bicycling looks like. Photo credit unknown.
Bicyclists in Europe lined up at a intersection stop. Photo credit unknown.
Bicycling Without Ages Program, Seniors on a ride, Oslo, Norway.
Dutch biking ad. Photo credit www.stuffdutchpeoplelikebook.com
Oops sorry, wrong photo. This is not commuter or work biking.
Photo credit Steven Lloyd Photography
Lane separation using just speed bumps, Germany. Photo credit unknown.
Regional Director for Mercedes in Ukraine on Bike to Work Day. Photo credit unknown.
Can you spot the difference between racing and commuting?
Photo credit: unknown
Children Cycling to School, Graph credit: European Cyclists Federation
Why is it that the countries that are most obsessed with bike helmets,
(USA, Canada, Australia, UK), have the least experience with biking?
http://massbike.org/resourcesnew/bicycle-statistics/
http://www.mrmoneymustache.com/2013/06/13/bicycling-the-safest-form-of-transportation/
http://nhts.ornl.gov/
http://nwurban.wordpress.com/2010/12/20/cyclings-impact-on-life-expectancy/
http://bicyclesafe.com
One of the most insightful replies was posted by Adonia Lugo related to her transportation equality study, Planning for Diverse Use/rs: Ethnographic Research on Bikes, Bodies, and Public Space in LA:
"Bicycling is legal on city streets in the United States. No laws keep motorists in their cars. This is not a situation where people's everyday practices have been disrupted by state apparatuses that govern through direct force, such as military police or an invading national power. And yet, an estimated 33,885 people died while using streets in the United States in 2009, according to the National Highway Traffic Safety Administration (2010). Of that number, 4,280 were pedestrians and 618 were cyclists, which means the vast majority of that estimate refers to dead motorists and their passengers. In the same year, an estimated 2,239,000 people were injured while using surface streets and highways. Bike advocates frame these injuries and fatalities as a design issue- with street infrastructure designed specifically for cycling in place, fewer people would drive. Instead of taking the built environment's role for granted, I chose to consider that this might be a case of discipline, the 'internalization of standards that are then enacted through bodily compliance.' (Foucault, 1977)"
After the Bicycle Petting Zoo I had to ride to the other side of Brattleboro, and the best route was through the center (1.4 miles) on downtown roads with continuous parked cars. With the electric assist on the bakfiets I was able to travel as fast as the cars (25 mph), with the cars accelerating away at the stop lights and then I'd catch up in a couple of hundred feet. I rode in the regular travel lanes like a motorcycle. (To some extent bikes like this make the need for bike lanes superfluous, but the catch is still taking care of all the other bikes that can't travel this fast.) The only problem was climbing the uphill out of the center with a one foot wide shoulder before the curbing. I stayed as far right as I could, but a small sedan behind me at the light just had to pass. It was pitiful, as he had the accelerator floored and wasn't traveling much faster than me, and then I had to stop and wait for him to turn at the next stop sign. He had a large error from his car centered view of the world but could not see it, and I had to deal with it.
Cars were truly amazing inventions of human creativity when I was a kid in the 1960's, and I still think some car driving is very special. But with increasing Vehicle Miles Driven per capita, I have watched them become an appliance, a unit in traffic. (You are not stuck in traffic, you are traffic.) I would argue that they have moved beyond the obesity, diabetes, heart disease, pollution, asthma, sprawl and environmental degradation linked to car use, and have now become a retreat from connection with the world around us and our thoughts. This should be enough reasons to use a car less, but most people will not be able to make a change.
What is risk? Is the limitation of risk such as envisioned by conservative financial investors and military advisers really applicable to bicycle riding? Is not walling off part of life a sign of decline? I'd like to end this post with a bit of philosophy. As Martha Nussman states about Euripedes' play Hecuba in the second half of this discussion with Bill Moyers, a life without openness, without trust, without risk, is not a human life:
Martha Nussmann, The Fragility of Goodness, interview with Bill Moyers, 1988
"This says something very important about the human condition and ethical life, that it is based on a trust in the uncertain and a willingness to be exposed; it's based on being more like a plant than a jewel, something rather fragile, but whose very particular beauty is inseparable from that fragility." Wrapping ourselves in a 3000 pound steel cocoon and telling ourselves that we are safe is a deception. Driving a 40 mile commute everyday at 65 mph is a distortion of reality. The everyday actions that we take- often just to get by- are what actually creates our world. How deeply do we wish to live?
Monday, June 9, 2014
Longtail construction (1/3) chain stays and battery box support
With the battery box finished, I could measure how long the frame needed to be extended and how high the rack had to be. Starting at the base of the frame the first pieces were the chain stays.
(Click on images to enlarge)
I made a jig to hold all the chain stay extension pieces in alignment. Starting with a 44" long scrap piece of plywood, I drew a center line and laid out the locations of the supports with a square. Trimmed blocks (I have a pile of little pieces from other projects) at the right thickness prop the pieces up and locate them side to side and front to back, and then I put some woodworkers glue on them, pressed them in place, and left them overnight to dry. In this jig the bottom bracket fits in the blocks on the left, a long bolt substitutes for an axle in the slots on the right blocks, and the new extension tube junction is propped up in the center.
I forgot to take a picture of the pieces at this stage, so this is an out of sequence later photo to show how the frame fit in the jig.
This is what actually came out of the jig, at this point it is tack welded together using a MIG welder, anything more would burn the jig up and reduce the accuracy. I routinely work to 1/32" (0.030"), and often lean cuts in one direction or another that brings accuracy to 1/64" (0.015"). Tighter accuracy than that is problematic as the scales on standard carpenter's measuring tapes vary in size along the tape, so you have to use other methods. However within assemblies such as the chain stay extension above, it is easy to get to 0.005 - 0.010 simply by holding the pieces up and comparing or scribing them. Wooden jigs also introduce an error, because wood moves with changes in temperature and humidity. On a small jig like this for a short interval of a few days it isn't a problem, but if I were to build a series of bikes I would make a large jig where a whole frame would lay on it's side, and the jig would noticeably move. Using a composite material such as MDF helps, but still requires some adjustments on different days. (Or spend a lot more money and time to make a metal jig.) At any rate this jig is more accurate than the factory was, where the bottom bracket was 3/32" to the left side, the rear wheel tipped 5 degrees to the right, and the bend in the rear seat stays 1/4" different.
If you'd like to read a bit more about handwork and accuracy, David Pye wrote a couple of excellent books a few years back- "The Nature and Art of Workmanship", and "The Nature and Aesthetics of Design". He built a semi automatic skorp to explore the interaction of humans and machines in guiding tools, and made some beautiful carved dishes to illustrate his thesis.
I lined up the template center line with a line drawn on the (level and flat) floor, and then lined up the front frame section and forks with the floor line. This lines up the bottom, and to keep the top straight at this stage I used a level on the downtubes, (watch out for tubes of different sizes), and a string from inside the rear dropouts to the head tube. There isn't much frame at this stage to measure, but it will save a lot of trouble later on if you get this part right.
I use a very fine string. In another life when I was doing woodworking, Japan Woodworker was selling ink string lines that had a very fine line, (in contrast to the usual carpenter chalk line), and I started using that line with chalk. Braided fishing line is an acceptable substitute, and for applications like this where I'm measuring and not putting down a line, I've dyed the line a bright color to make it more visible.
Both sides of the seat tube should have the same distance to the strings. For safety I should mention here that if you cut up your old tape measures for use as high visibility rulers, YOU MUST NIP THE CORNERS OF THE PIECES! to blunt them. They are VERY sharp, and will eventually give you a very nasty cut.
The frame needs some triangulation to make it rigid. Unfortunately the battery box is in the way, so I was able to put only one tube under the box to reduce vertical flexing. I propped up the pieces and marked out a tube location with some clearance to the front edge of the battery box.
This tube ties the seat tube and the new chain stay junction together to stop upward movement of the new chain stay extensions. If this tube were all there was I would not be happy- I think eventually heavy loads on the cargo bike would bend the seat tube. However the rack and a few other stays further back will share the load to help increase strength, and should make the bike stiff enough to handle decently.
Propping the bike up next to the battery box again, I measured for supports for the battery box, and cut out tabs to put on the brace tube.
Across the top of the tabs is a heavier piece of sheet metal, so that the weight of the battery doesn't deform the floor of the thinner battery box. After welding this piece on, I was able to finally set the battery box in the frame, check clearances, and mark out holes for the mounting screws. The two screw mounts in the frame tube are actually bottle holder mounts from when the tube was previously a down tube. I put them to the side for possible use in mounting a chain guard, or maybe an idler sprocket if the chain droop turns out to be too large.
Subscribe to:
Posts (Atom)