Bent Ply bike sketches

Concept 10 142

bentplysketchestempA few weeks ago I posted a bike, sent to me by a reader, which featured a frame partially constructed from laminated wood. Peter from Velo Vision recently sent me an email and identified the mystery bike as the work of James Coleman, a design student at Loughborough University in the UK. When I first saw the bent ply bike concept, it reminded me of a few thumbnail sketches that I did a couple years ago. The message from Peter reminded me again of the old sketches, so I decided that I would dig them up to share (it has been a while since I posted any of my own sketches on this blog unless you count the three bikes in the header).

I did these thumbnails one day while I was looking at Alvar Aalto chair designs from the 1920’s in a furniture book (and in that book is where I found the sketches). You have probably noticed that all of the classic bent ply chair designs take advantage of the flex that is inherent in the material. Laminated plywood is very strong, but it does flex in the direction perpendicular to the individual plys. As I browsed though the pages of chairs from Aalto, Charles and Ray Eames, and others, I wondered why so many bikes that I see designed from plywood have the material oriented in a way that it does not provide any suspension for the rider. The Jano bike and the Sandwich bike, both of which I have posted before are nice designs, but they are examples of bikes in which the orientation of the plywood would not provide any vertical compliance.

Anyway, my idea was to create a frame from two curved pieces of laminated hardwood so that the frame would have a natural suspension effect. It might even be possible to add a carbon ply in the middle as at least one skateboard manufacturer has done in recent years. As you can see, the sketches are rough and I haven’t given the idea much thought since the day I did them, but I think they could be possibly developed into something. There certainly would be several challenges to overcome in the design and development of a bike like this. The plywood “top tube” would need to be wide enough to provide the necessary strength, but at the same time it would need to be narrow enough that knee clearance would not be an issue. The same issue would apply to the Q factor at the bottom bracket and don’t even get me started on the chain and seat stays. There would be many other challenges as well, but it would be a fun idea to take further if I had the time. Of course, I probably wouldn’t be posting the idea here if I thought it was really worth pursuing (does the world really need another wooden urban bike?). Still, I think there would be a niche market for a bike like this. I could see this bike, with a natural birch ply frame and a Shimano Alfine grouppo, for sale in a furniture catalog like DWR. Maybe I will clean up the sketches and do a quick rendering to post one day; probably not though, so don’t hold your breath. Then again, maybe I should do the rendering just for the person who recently left the following anonymous comment; “great. another wood bike. i have news for you- wood is NOT a good material for bikes. enough already!” Yep, this post is just for you.

Update: See a quick Photoshop rendering of the concept below. Prototype to come later…maybe?

Bent plywood bicycle rendering by James Thomas

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10 Comments

  1. C February 7, 2008 at 2:57 pm -  Reply

    “wood is NOT a good material for bikes. enough already!”

    Whoever said that is clueless, pure and simple. I find the hubris of some people in the cycling world to be truly staggering. People will say wood or carbon fiber or aluminum isn’t strong enough for a bicycle and yet we have ships and airplanes made out of these materials. Do you seriously expect me to believe that you as a cyclist are going to put a bike through more stress than what an airplane wing, ship hull, or helicopter rotor sees? Are you serious? Get real. There have been thousands of wooden aircraft – including 300+mph fighter planes – that took more abuse than any bicycle will ever see. Ditto for alloy and composites. The fact that these materials have had issues when used in cycling applications has little to do with the material and lot to do with the incompetence of the designers and mechanics in the cycling industry. Little surprise that two of the best (and most durable) carbon bikes come from Craig Calfee and Bob Parlee both of whom entered cycling from other industries.

  2. Adam February 7, 2008 at 3:30 pm -  Reply

    Wood aside, I’m curious if you think the design has any merit in steel. Seems like there could be a similar spring effect, depending on the contours of the tubes.

  3. dolan February 7, 2008 at 3:40 pm -  Reply

    You might be able to make the top tube and seatstays thinner if you layered the plys and added some middle material to control the vertical pliance.

  4. Fritz February 8, 2008 at 1:05 am -  Reply

    I think you’re wooden bike posts are the best, James :-) Keep ‘em coming.

  5. Antti February 8, 2008 at 7:26 am -  Reply

    Plywood is good material for bikes.

    Check these wooden recumbent’s made by Saku Holma.

    http://www.flickr.com/photos/saholm/

    BTW. Saku lives in Alvar Aalto’s hometown.

  6. Mr. Beattie February 8, 2008 at 1:19 pm -  Reply

    There is at least one hard wood builder at this years Handmade Bicycle Show in Portland, on the BikePortland blog Maus interviewed Ken Wheeler from Reovo Hardwood Bicycles as part of his lead up to the NAHBS series. http://renovobikes.com/ Doesn’t have much up yet, but you should check out the bikes if you are in Portland for the show.

  7. bikesgonewild February 9, 2008 at 12:29 am -  Reply

    …i never tire of wooden bike designs & kudos to you for your drawings…

    …yes, the fact that you are utilizing an inherent capacity of plywood, especially in light of the bowed shapes you’ve conceived of, seems to be an intelligent direction to explore…

    …w/ the steaming & bending involved, you might consider doing a twist on the seat & chain stays right before the dropout…you would lose very little vertical compliance or lateral stiffness (there are those catch phrases we all joke about) & it might provide a stronger, less problematic dropout…

    …maybe we can get erik k to provide a link he has on his site for two more wonderful looking wood bikes…
    …one in plywood & one in walnut, i believe…

  8. Tirapop February 9, 2008 at 3:21 pm -  Reply

    Great thread. I sent James the pic of the mystery bike. I was disappointed with the responses to that thread. Lots of underinformed negativity. It’s great to discover, at long last, who made the mystery bike and to be introduced to a serious wooden bike like the Renovo.

    I like seeing the bent ply sketches. I’ve had an idea I’ve been kicking around for a long time, a wood monocoque bike frame.
    http://flickr.com/photos/tirapop/
    Laminated wood leaf springs suspend the saddle. The nonsense to the right is a woven basket/fairing with integrated headlight.

    My day job is analyzing the structure of airplanes. Looking at thin flat laminated top and down “tubes”, what jumps out at me is the challenge to provide enough torsional rigidity between the handlebars. I haven’t read any reviews of the Waldmeister. I don’t know if it’s excessively whippy when you’re cranking hard on the pedals. Its “down tube” isn’t particularly thin, which would help. You might go thick in the “down tube” and thinner in the other “tubes” and stays.

  9. James February 11, 2008 at 9:26 am -  Reply

    Thanks to all of you for the comments on this post. I have not had the time lately to follow up on comments, but I do greatly appreciate them.

    In addition to the wood bike links left here by Antti, Mr. Beattie, and Tirapop, I have received a few more links by email. Fritz, you will be glad to know that I will put all of those links into another wooden bike post when I get the chance. Keep the links coming.

    Oh yeah, thanks for the design suggestions too. I doubt I will take this idea past the thumbnail sketch stage, but I still like to hear ideas for doing so. That is what design is all about. Good discussion.

  10. bmike February 13, 2008 at 12:13 pm -  Reply

    “Still, I think there would be a niche market for a bike like this. I could see this bike, with a natural birch ply frame and a Shimano Alfine grouppo, for sale in a furniture catalog like DWR.”

    Bikes as accessories and furniture!
    More hipster chic for the conspicuous consumption loft apartment cycling scene. Be sure to make it in a FG though – more street cred – esp with an argyle top tube pad.

    ;)

    I don’t think wood / plywood by itself can do the work – a carbon / plywood / kevlar mix would help, much like in lightweight wooden kayak designs – or you have to go monocoque (sp?) construction like the Portland folks – which is a pretty interesting approach.

    Wood is not good in tension – (and can actually be quite horrible with catasrophic failure) – so you’d have to design the frame to the strengths and weaknesses of the materials – and be sure that any failure was one that happened slowly – snapping of anything would be a bad thing.

    To the ‘fighter plane’ comment – yes – as a cyclist you could possibly develop enough force locally (in proportion to member size of the loaded joint) that you compete with an airplane (think bottom bracket, fork over a bump on a high speed turn, standing and sprinting forces on the whole frame…) – planes and boats made out of wood typically have framework and exterior skins which help distribute the shear forces across the structure – so a comparison to a bike – where the frame is it – isn’t really apt – and many of these structures have redundancies within – structure backing up structure… a bike is pretty simple compared to this – the frame is it – not much cross bracing, wire tension ties, etc. etc.

    I’m all for new materials entering the bike world (and I work in the wood industry) – but plywood furniture isn’t exactly dynamically loaded 100’s of times a minute during a ride. I’d be curious to see how / if a plybike could be made to handle the stresses – but my guess is the laminate process – including kevlar, carbon, etc. etc. would play a role – and you’d still have to have plenty of metal bits – threads for the BB, mounts for brakes, bearings, etc. Calfee is essentially using bamboo to its strength – in tubular form. There’s probably a fair amount of epoxy, resin, etc. holding the joints together.

    The link to the wooden bents and trikes are pretty cool – looks like he’s taking cues from boat builders and creating shell like structures – something harder to do on a DF design… wonder why he didn’t make wooden fenders?

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