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  1. #1
    Silverfish Supporting Vendor Concrete Kahuna Rich Nelson's Avatar
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    Default Single Rider Human Powered Vehicle: Bamboo Recumbent Bike w/ Full Aerodynamic Fairing

    Hey guys, many of you probably remember me from Nelson Longboards, I've been MIA lately due to focusing on finishing up college and very time consuming senior project. My senior project was to construct a human powered vehicle, my job specifically being the aerodynamic fairing (shell), then we went to a competition to race it. I used a ton of the knowledge that I gained from silverfish and from building longboards in all aspects of this project, and in the process learned a lot from the project. So, I figured I'd take you guys through the design/construction process.

    (sorry in advance for the extremely long post, I wrote a 24 page paper on my part of the project alone so I'm going to do this in the form of a photo journal to keep it as breif as possible)


    Someone riding a recumbent bike

    The idea behind the recumbent bike is to put the rider in a reclined position, by doing this you become naturally more aerodynamic because you decrease the area of your frontal profile. so the reclined position along with a full aerodynamic enclosure is used to reduce drag on the rider as much as possible on the rider.


    My teammates decided to make the frame out of bamboo, so some testing was done to determine structural properties of bamboo.


    Scale person used to determine seating position, wheel base, and position of the crank


    3-d view of frame design with roll bar load applied. (wheels not pictured). truss design was used to avoid any bending moments or torsional forces on the bamboo which may have caused it to split


    2-d fairing design to fully encompass the bike and the rider, designed to mimic a tear drop shape from top view, and to smooth airflow of the vehicle



    3-d model of fairing designs three designs all with their own advantages


    CFD (computational fluid dynamics) testing to determine the aerodynamic properties of each design. choice was made by considering this along with the manufacturability and other things.


    Final fairing design, with changes to accommodate some revisions of the frame


    Fairing design with scale rider, and rough window shape/position


    To determine the layup I did some materials testing. Above are 12 samples made with various combinations of carbon fiber, fiberglass, 1/8" & 1/4" divinycell foam, and coremat


    The samples were testing in a simply supported bending scenario, each sample to be compared based on strength, deflection, weight, and cost


    wooden cross sectional templates for fairing mold. wooden templates were used to shape foam sections for the mold


    Wooden templates being used to guide hot wire cutter to cut foam to shape


    Foam cut to shape, then added on to the rest of the mold


    mostly completed molds (left before sanding, right pic after sanding) the nose and tail pieces were created later without templates


    The layup was done in a large vacuum bag measuring roughly 10'x5'


    Each layup was done in 2 part, this being the first where 1 layer of FG was layed up and 1/8" divinycell core material was used for a large portion of the fairing, it was not conformable enough for the tighter contours of the fairing so coremat was used there


    Layups on both valves completed with the coremat used where the divinycell was not, and kevlar being used on the sides for abrasion resistance


    Halves being matched up and prepared to be joined
    Designed, Built, and Tested by Skaters, for Skaters.
    NelsonLongboards.com


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  3. #2
    Silverfish Supporting Vendor Concrete Kahuna Rich Nelson's Avatar
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    Default Re: Single Rider Human Powered Vehicle: Bamboo Recumbent Bike w/ Full Aerodynamic Fai

    Custom made parts for the bike


    Custom hub for 20" front wheel with mounting points for two disc brakes



    Aluminum part to attatch to bamboo frame, with slot for the front fork, and adjustable mount for the crank


    brackets for back dropouts, with 6 aluminum pieces machine to the inner diameter of the bamboo members


    Frame under construction, bamboo pieces machined to length and custom fit together


    Completed frame without drive train components carbon fiber wrapes used to secure bamboo members


    Completed bike, with custom seat, made of fiberglass and 1/8" divinycell foam. (can you spot the pink powerball?)


    Frame inside of half of the fairing


    Fairing primed and spackled, with the top hatch cut off. being attached to the frame.


    Picture of the fairing mounting points


    Complete paint job, and custom windows installed


    Team photo


    Action Shots







    Designed, Built, and Tested by Skaters, for Skaters.
    NelsonLongboards.com

  4. #3
    Silverfish Supporting Vendor Concrete Kahuna Rich Nelson's Avatar
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    Default Re: Single Rider Human Powered Vehicle: Bamboo Recumbent Bike w/ Full Aerodynamic Fai

    In the end I was very happy with how the project turned out, with ~25mph max speed with partial fairing and ~30mph max speed fully faired (tested on flat with a GPS watch to track speed). Also out of the 28 years that the competition has been running, ours was the first bamboo bike.

    If you guys have questions about any aspect of the project I would love to answer them, I have tons of data and information that is not included, to keep the post as brief as possible.
    Last edited by Rich Nelson; 05-16-2010 at 11:39 PM.
    Designed, Built, and Tested by Skaters, for Skaters.
    NelsonLongboards.com

  5. #4
    Concrete Kahuna Pleinair's Avatar
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    Default Re: Single Rider Human Powered Vehicle: Bamboo Recumbent Bike w/ Full Aerodynamic Fai

    Two questions

    How the hell did you manage to keep it from tipping over when you're at a standstill, and how would you get a start from a standstill by yourself?
    Cigs

  6. #5
    Concrete Kahuna virx67's Avatar
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    Default Re: Single Rider Human Powered Vehicle: Bamboo Recumbent Bike w/ Full Aerodynamic Fai

    Cool bike. One question: how is this related to longboard building?

  7. #6
    Concrete Kahuna CarlTheSmokingCrab's Avatar
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    Default Re: Single Rider Human Powered Vehicle: Bamboo Recumbent Bike w/ Full Aerodynamic Fai

    it's not. but look at the construction! look at what he had to do to make the fairing!
    good work sir, much respect to you.
    - generic
    motion boardshop, seattle washington 206.372.5268
    Team Stepdad. Cause you hate us, and we beat you.
    Quote Originally Posted by Justin K View Post
    All of you noobs are MEGA bitches. I never knew vaginas could get so sandy. All of you suck. People ride what they want, how they want, when they want. Get it through your noob ass head.

  8. #7
    Silverfish Supporting Vendor Concrete Kahuna Rich Nelson's Avatar
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    Default Re: Single Rider Human Powered Vehicle: Bamboo Recumbent Bike w/ Full Aerodynamic Fai

    Quote Originally Posted by Pleinair View Post
    Two questions

    How the hell did you manage to keep it from tipping over when you're at a standstill, and how would you get a start from a standstill by yourself?
    At first when the full fairing was attached we needed the help of team members to keep it balanced while you were stationary and starting to pedal. After the competition I cut out some foot holes so I could ride it around campus on my own (and got countless wtf looks from people while riding of course).

    Quote Originally Posted by virx67 View Post
    Cool bike. One question: how is this related to longboard building?
    A lot, the methods for making the foam mold are more or less the same as molds for longboards. I used the same materials that many builders use for foam core boards and composite boards in general, and the vacuum bag construction is the same as many use for building longboards as well.

    I wanted to post it here because I figured the people who frequent the building forums would get the most out of it. I wasn't just posting it as a 'hey look what I made', it was more to show the method behind the construction etc, so hopefully some people will learn a few things, or get some ideas that they could apply to their building.

    Quote Originally Posted by CarlTheSmokingCrab View Post
    it's not. but look at the construction! look at what he had to do to make the fairing!
    good work sir, much respect to you.
    Thanks man
    Designed, Built, and Tested by Skaters, for Skaters.
    NelsonLongboards.com

  9. #8
    Concrete Kahuna Pleinair's Avatar
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    Default Re: Single Rider Human Powered Vehicle: Bamboo Recumbent Bike w/ Full Aerodynamic Fai

    Ah, I see.

    That's hardcore as ****. I would totally buy one of those, if it came with air conditioning and a radio
    Cigs

  10. #9
    Concrete Kahuna xzyragon's Avatar
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    Default Re: Single Rider Human Powered Vehicle: Bamboo Recumbent Bike w/ Full Aerodynamic Fai

    only 25-30?

  11. #10
    Addicted Cruiser RSnider's Avatar
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    Default Re: Single Rider Human Powered Vehicle: Bamboo Recumbent Bike w/ Full Aerodynamic Fai

    Quote Originally Posted by xzyragon View Post
    only 25-30?
    Last time I checked, a sustained 25-30 mph on level ground is quite fast for anyone that doesn't train every day.

  12. #11
    Addicted Cruiser StickyVortex's Avatar
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    Default Re: Single Rider Human Powered Vehicle: Bamboo Recumbent Bike w/ Full Aerodynamic Fai

    Quote Originally Posted by xzyragon View Post
    only 25-30?
    Why don't you go pedal on the flats on your bicycle and tell us what you hit.

  13. #12
    Concrete Kahuna robert borek's Avatar
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    Default Re: Single Rider Human Powered Vehicle: Bamboo Recumbent Bike w/ Full Aerodynamic Fai

    RAD!

    thats very very very cool. nice one. i think the world record for a fully faired recumbant is 80mph. that was drafting a car though.

    ive seen some bikes like that which have retractable stabalisers like on a kiddy bike. so you can get in and start riding and then pull them up!
    www.vandem-mfg.com

  14. #13
    Silverfish Supporting Vendor Concrete Kahuna Rich Nelson's Avatar
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    Default Re: Single Rider Human Powered Vehicle: Bamboo Recumbent Bike w/ Full Aerodynamic Fai

    Quote Originally Posted by xzyragon View Post
    only 25-30?
    Yea, this was the first year that our school did the project, so theres quite a few things we could have done differently to get to a higher top speed.

    IMO the main inefficiently in our vehicle was the fact that we used the back wheel as the drive wheel, which meant we had to route the chain down and under the seat,


    we did this by machining channels out of delrin to guide the chain to the sprocket under the seat. this ended up causing a lot of inherent friction in the system even if you lifted up the back of the bike there was still significant resistance turning the pedals.

    Most of the more experienced teams at the competition used a front drive wheel, we had ruled this out early on since running a chain to the wheel that you steer with meant the chain would have to bend every time to turned, and also we have a two chain system with 27 gear combinations it would have been tough to fit it all up front.

    Besides that we over engineered the frame a bit since the material was somewhat unpredictable and unproven, our frame was a tub style meaning it surrounded the rider including being outside the riders shoulders, so a more traditional frame would have allowed us to shave 6-8in off the width of the vehicle greatly increasing its aerodynamics.

    Lastly no one on our team spent any real time training besides just practicing on the bike to get comfortable in the recumbent style.

    In the end, we didn't reach some of our performance goals, but I was very happy with how it came out.



    Quote Originally Posted by robert borek View Post
    RAD!

    thats very very very cool. nice one. i think the world record for a fully faired recumbant is 80mph. that was drafting a car though.

    ive seen some bikes like that which have retractable stabalisers like on a kiddy bike. so you can get in and start riding and then pull them up!
    Cool, that was the one thing that we really wanted to implement but we were to tight on time at the end. We basically had a set of training wheels what we wanted to rid up to some sort of lever system to make landing gear. I assumed that it must have been done before, and was pretty surprised when I didn't see anything of that nature at the competition.
    Last edited by Rich Nelson; 05-17-2010 at 08:10 AM.
    Designed, Built, and Tested by Skaters, for Skaters.
    NelsonLongboards.com

  15. #14
    Addicted Cruiser Death By Snu Snu.'s Avatar
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    Default Re: Single Rider Human Powered Vehicle: Bamboo Recumbent Bike w/ Full Aerodynamic Fai

    Love me some science and engineering!

    Great job!
    For your health!

  16. #15
    luke Addicted Cruiser kraffft's Avatar
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    Default Re: Single Rider Human Powered Vehicle: Bamboo Recumbent Bike w/ Full Aerodynamic Fai

    This rules, thanks for posting.

    Tons of questions..

    Here's a couple to start off.

    The down tubes look like the weakest point in the frame.. It doesn't look like a big problem with static loading, but say your front wheel hits a pothole, that translates to a ton of stress in the head tube area. No?

    Was there any actual weight savings with the bamboo? compared to say chromoly or aluminum?

    My primitive understanding of aerodynamics is that for minimal drag you want the rear cone of the shape to be four times longer than it is wide.. It looks like you have closer to a 1:1 ratio there.. do you have a rough idea what the theoretical difference in efficiency would be?

    and to others, top speed in something aerodynamic like that is all about the gearing.. throw an extra hub, chainring, chain, and derailleur in there and anyone in decent shape could go 50mph no problem.

    also, a tip for anyone posting tons of pics.. The silverfish site makes your browser do the work of resizing images to fit the screen, the large version is still getting downloaded and slow computers will get bogged down by all the rendering. So ideally resize em to around 600 pixels before posting.

  17. #16
    Addicted Cruiser RSnider's Avatar
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    Default Re: Single Rider Human Powered Vehicle: Bamboo Recumbent Bike w/ Full Aerodynamic Fai

    Quote Originally Posted by kraffft View Post
    also, a tip for anyone posting tons of pics.. The silverfish site makes your browser do the work of resizing images to fit the screen, the large version is still getting downloaded and slow computers will get bogged down by all the rendering. So ideally resize em to around 600 pixels before posting.
    +1 .

  18. #17
    Capo di Tutti Posto 8ftbed's Avatar
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    Default Re: Single Rider Human Powered Vehicle: Bamboo Recumbent Bike w/ Full Aerodynamic Fai

    Rich - congratulations! I enjoyed the walk through and final results. Anything worth doing is worth doing right and usually results in you seeing room for improvement if you do it again.


    The UNF's though... they're causing me problems.

    I've been getting asked from multiple sources if I wouldn't like to sell one of mine. uh... NO!
    I hope you kept that mold. It even made a fine appearance on an 8 mile push a week ago on some monster hawgs.

    Thank you sir for cranking those last ones out for me.

  19. #18
    Silverfish Supporting Vendor Concrete Kahuna Rich Nelson's Avatar
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    Default Re: Single Rider Human Powered Vehicle: Bamboo Recumbent Bike w/ Full Aerodynamic Fai

    Quote Originally Posted by kraffft View Post
    The down tubes look like the weakest point in the frame.. It doesn't look like a big problem with static loading, but say your front wheel hits a pothole, that translates to a ton of stress in the head tube area. No?
    this part worried me the most as well, especially since they're dealing with bending forces unlike most of the rest of the frame. To try to make it as sturdy as possible the aluminum rods were machined to the exact inner diameter of the specific bamboo members, then the aluminum surface was knurled and epoxied inside the bamboo (the bamboo.AL overlap was about 4-5"). then the outer surface of the bamboo was wrapped with carbon.




    The two members connecting to the aluminum were then supported by additional members (as far up as we could without limiting leg range of motion) shortening their effective length, and also a bamboo member between the critical members with the aim of distributing the stresses between the two and prevent any twisting.

    All in all it was very solid, dealing well with pot holes, cracks, etc. though there was a slightly noticeable deflection of the crank about 1cm to one side and the other while pedaling.



    Quote Originally Posted by kraffft View Post
    Was there any actual weight savings with the bamboo? compared to say chromoly or aluminum?
    The most common material used from what I've seen is chromolly. We did do a stress analysis and weight comparison using our frame design and comparing to standard sized chromoly tubing (the exact size escapes me now). and there was significantly lower stresses and weights with the bamboo. But this comparison wasn't realistic because the cromoly tubing wouldn't require such a robust structure.

    In the end our frame weight was 12lb, and 14lb including the aluminum parts. This is comparable to the weight of an average simplistic chromoly frame. We were purposefully conservative with the frame design being that we didn't have experience with bamboo and it's close to impossible to create an accurate stress analysis model being that it's a non-isotropic organic material. The frame was extremely sturdy with no noticeable flex, if we were to design a new bike we would probably design a less robust frame to take more advantage out of the weight benefits of the material.

    Quote Originally Posted by kraffft View Post
    My primitive understanding of aerodynamics is that for minimal drag you want the rear cone of the shape to be four times longer than it is wide.. It looks like you have closer to a 1:1 ratio there.. do you have a rough idea what the theoretical difference in efficiency would be?
    I've never hear of the rule of thumb but it seems pretty reasonable. In the fluid dynamics analysis at 40mph there was some flow separation toward the back of the fairing, though it didn't seem severe the design probably would have benefited from a somewhat longer tail section. During the CFD I was focusing more on comparing the designs, and I probably should have spent more time focusing on optimizing the selected design.

    As for the difference in efficiency, I'm not sure how significant it would have been, but minimizing the low pressure zone due to flow separation at the back would have definitely been a benefit, and the benefit would obviously be more significant as the speeds increased.

    Quote Originally Posted by 8ftbed View Post
    Rich - congratulations! I enjoyed the walk through and final results. Anything worth doing is worth doing right and usually results in you seeing room for improvement if you do it again.


    The UNF's though... they're causing me problems.

    I've been getting asked from multiple sources if I wouldn't like to sell one of mine. uh... NO!
    I hope you kept that mold. It even made a fine appearance on an 8 mile push a week ago on some monster hawgs.

    Thank you sir for cranking those last ones out for me.

    Thanks man, its good to know that the boards are treating you well. I'm definitely holding on to the mold, the concave is just too comfortable.
    Last edited by Rich Nelson; 05-17-2010 at 10:10 PM.
    Designed, Built, and Tested by Skaters, for Skaters.
    NelsonLongboards.com

  20. #19
    Concrete Kahuna sterlingc's Avatar
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    Default Re: Single Rider Human Powered Vehicle: Bamboo Recumbent Bike w/ Full Aerodynamic Fai

    this is so ******* ridiculous and awesome

  21. #20
    Concrete Kahuna xzyragon's Avatar
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    Default Re: Single Rider Human Powered Vehicle: Bamboo Recumbent Bike w/ Full Aerodynamic Fai

    Quote Originally Posted by StickyVortex View Post
    Why don't you go pedal on the flats on your bicycle and tell us what you hit.
    i ran cross country and cross trained with biking during highschool...

    i don't want to start a flame war, but i've seen recumbent bikes booking it...

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