Wood You Build IT?

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There have been a few posts recently regarding wooden trikes and velomobiles. Having followed them, and viewed a few video links here and there, an idea came to me. This is always a dangerous thing as it inevitably leads to thoughts of another project. Anyway, here follows what might be a whole new idea.

Trikes are usually built with two main aims that are speed (light), or utility (as light or as heavy as it ends up).DIY velomobiles are usually built as trikes with a body later attached. Bodies generally consist of coreflute (coroplast by another name) for lightness, fibreglass or carbon fibre for strength, or even wood. Each of these provides different levels of difficulty for DIY.

What about this approach for utility purposes? First, construct a strong wooden body, from plywood or whatever, internally braced where necessary to accommodate forces, and attach the wheel, steering, pedalling modules, etc. These could be minimal, individual modules bolted to the body wherever required, saving a little in steel weight – and welding. This would at least save the steel mass of the front wheels cross bar, the central boom, and maybe the rear triangle. Such mounting things could be part of the internal body bracing.

There’s the idea and the floodgates have been opened for comments.
 

SirJoey

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I'm not much of a "designer" per se. I'm much better at taking existing designs,
and (sometimes) improving them, or at least altering them to what SEEMS
to be an improvement, but it seems to me you may be onto something,
although it also seems like it would be a little heavy, IDK.

***
 
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The Mosquito fighter-bomber was a wooden frame with all the metal bits bolted-on/in.
It was incredibly versatile and easy to repair and was mostly plywood and bracing (a bit like engineered joists of today).
Built by piano makers in factories all over wartime Britain. :D

Stu in Berlin built a wood & hemp/string/resin trike and as far as I know it hasn't yet fallen to bits.
 
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I am all for the 'Homemade/DIY' projects.

Example my 'experiment' with building a PVC pipe pedal car.
I completed the project far enough to have a working chassis.
I did not do any calculations regarding weight, as it pertained to the mechanics of pedal power.
As a result the project was abandoned, due to being much to heavy, to be practicable.

Might I suggest this.


First: define what you mean by ..utility purposes'?
Second: Decide what the body will actually be made of....."from plywood or whatever" (It will be hard to find the weight of whatever):)
Third : Decide what the bracing material will be...metal, wood, nuts and bolts, screws, nails, glue, fiberglass resin, etc.
Forth : Draw out your idea, including how you visualize the 'internally braced' items.
Fifth: Will your design be doable, in regards to setting and maintaining the accuracy of the angles necessary for, the steering, chain drive, brakes, etc.
Example, if you use the body to hold these and other components, and the body flexes, so may your components.

Just a rough drawing is all that is really needed, so you will have a plan going forward, of how your project will be built...piece by piece.
With that knowledge, you should be able to determine, (with online calculators and info) the approximate weight of your project, vs the approximate weight of one of Brads plans. Example: 1.5" x 1.5 " x .065 square tube is, +/- 1.26 lbs per foot. (Sourced from online)

I think only after the weights of the two methods of construction are calculated, and the resulting difference,
can the design and effort be determined, as worth it.

Alternatively, go ahead a build it, as you see it, and learn from that experience. Nothing is wasted, if the journey is enjoyable.
My experience in building something unorthodox, (my PVC T Bucket), could be viewed by some as a waste of time and effort,
but I gained experience and knowledge, that I use to this day. But I enjoyed the process....well most of it. ;)

Good luck with your build, which ever way it may evolve.
 
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I suspect that calculating stresses and weights on what is essentially a monocoque is going to be quite difficult. Steel frames are well understood with countless examples about. I also suspect that failure of a monocoque is likely to be substantially harder to repair. Changes mid-build to work around issues are also going to be that much more difficult.
 
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I only mentioned it as a discussion piece. At the moment, I don't intend to build but, as I said, thinking can be dangerous. There appear to be many pros and cons and depends on which outweigh the others. Having experienced some hang-a-plywood-body-on-a-trike woes, and discovering rapidly escalating weight leading to abandonment, I think it would be a doable alternative and an idea for the plywood body people. Trying to manipulate plywood to fit a trike and provide an enclosed body is a lot of work. Might be some further benefits in first making the body just big enough and then seeing how three wheels might be attached. Might result in another trike design.

My interpretation of "utility" is something used for more than just riding from one place to another. It has to be able to carry something. Factotum might be a better word borrowed from FIAT tractor ads of 50 years ago. Having something of an inventive mind, I quickly get bored just riding. I ride off-road and, other than my local small town of maybe 600 folks, I have 21km one way and 31km the other just to get to another town. Plenty of time for thinking and talking to the same old trees. Maybe there is a problem with what they are saying to me.
 
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Commercial velomobiles are monocoque or semi-monocoque. Here is the subframe of my Alleweder velomobile during construction:





The parts are CNC-machined aluminium (a lightweight corrosion-resistant metal found in former British colonies; similar properties to aluminum :)). They are bolted together so no ali-welding is required ... but you would need a tap and die set. At this stage of construction the frame would not support a rider's weight; the outer skin is also structural.

With plywood you could mimic CNC machining by laminating two layers of plywood together - one layer of 3mm for the main shape and another layer perhaps 6-9mm thick for the webbing.

Suspension adds to the complexity but reduces the impact forces on the structure.

Longfellow (my planned tandem velomobile) is still deciding whether to be a steel-framed bike or a plywood and aluminium monocoque. I am currently experimenting intermittently with a front transaxle (to make it four wheel drive); if this works out then it will be a monocoque, with the existing half-complete steel frame serving as a development buck to determine component locations.

I suspect it would be almost impossible to build the perfect monocoque in the first attempt - not enough material and it will break; too much and you are hauling around more weight than necessary. Unfortunately only practical experience or some fiendishly complicated finite element analysis will produce the ideal answer!
 
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1/4" thick plywood is about the same weight as 1/16" thick aluminum
Steel is about 3x the weight of aluminum therefore
3/4" thick plywood is the same weight as 1/16" steel.
so if you have a 1.5" SQUARE tube 16 gauge you could use a
1.5"x3" piece of lumber and it would be the same weight
or 1"x4.5 piece of plywood.
 
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of course weight of wood varies depending on type
a 4x8' 16 gauge steel sheet is 80 lbs.

Standard Plywood Dimensions
Weight of 4′ x 8′ sheets of various types and thicknesses of plywood measured in pounds.
Plywood TypePlywood Thickness
1/4″3/8″1/2″5/8″3/4″1-1/8″
Softwood Plywood22 lbs28.5 lbs40.5 lbs48 lbs61 lbs84.5 lbs
Hardwood Plywood24.5 lbs31.5 lbs45 lbs53 lbs67.5 lbs94 lbs
Marine Plywood27 lbs35 lbs50 lbs59 lbs75 lbs104 lbs
Baltic Birch26 lbs33.5 lbs48 lbs56.5 lbs71.5 lbs99.5 lbs
Particle Board33 lbs43 lbs61 lbs72 lbs91 lbs127 lbs
MDF36 lbs46.5 lbs66.7 lbs78.5 lbs99.5 lbs138.5 lbs
MDO20 lbs26 lbs37.5 lbs44 lbs56 lbs77.5 lbs
OSB25.5 lbs33 lbs47 lbs55.5 lbs70.5 lbs98 lbs
 
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once you start thinking about weight and looking up what things actually weight, you will findout quickly that a wood build can weight about the same as a steel one if done correctly. Best way to keep weight of wood down is to use aluminum connectors in the right spots to connect panels and other items together.
 
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All interesting comments. There will be tradeoffs between the mass of a wooden body with bits attached and a steel trike with a wooden body attached to it and one might not know what they are until one does it.

A method of saving wood mass would be to construct a body using plywood sheets with non-structural, and therefore unnecessary, areas removed, leaving a strong skeleton where it matters. Interior bulkheads, etc., can be used for additional strengthening struts where steel bits (wheels, etc.) are attached and skin the whole with your choice of other, lighter, materials, Dacron, Coroplast, or some of that whatever that was earlier mentioned.

The desire to have a go is building.
 
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You mean like this ?

Plywood Velomobile



I came across it when in Holland and had a test ride in it :-



Sadly site is lacking in details on how to build it ...
 
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Not quite what I was thinking, although it would probably suit the cloth/coroplast exterior skin type construction quite well and that shape would be more suitable for speed. At the time I was thinking more in terms of the commercial Elf, Ecovelo, Twike, etc., and T.A Hustvedt's aluminium and plywood DIY creation but, hey, if the cap fits, wear it. Doing a Google on those names will bring up images.
 
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Since starting this thread, I have been vacillating between "Should I change direction and modify my eLecTricks build to incorporate a monocoque body?" or "Should I continue as planned and complete that which I started?" I can always make another. I would very much like to change direction but that would slow the project way down and it has been slowed way too much already. When I was typing that previous sentence, I thought I had decided to continue, working on a monocoque design in the background, but I think a monocoque body will be much easier to build. I said that thinking was dangerous.

Looks like the current build is stopped while I look at coming up with a usable body design that will make the decision for me. It won't be all downtime as there are a couple of things I need to do, regardless.
 
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Someone on the old forum built this :



Lynx

Sounds like what you want to build ?
 
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The builder of the Lynx was the T.A. Hustvedt that I mentioned and is also close to what I was talking about. The body consisted of two layers of ply - a "skeleton" internal layer and an outer skin layer. He did have the benefit of milled aluminium to keep the weight down but it still must have been quite heavy. His last posts on the forum indicated that he was making its successor, but he seems to have gone very quiet since. The incentive it gave me led to my earlier plywood experimentation that became far too heavy - and I used only a single layer of 3-ply.

Using ply only for the skeleton and skinning it with something else whould be much lighter but I will have to come up with a close design first to consider it. I have to weigh up (no pun intended) skeleton ply against saved chassis steel and coreflute/coroplast mounting brackets, as well as ease of building. It might be possible to imagine a plastic skin, or outer, with plywood strengthening or struts where necessary. The plastic will need framing of some sort but it is starting to look like just using plywood instead of steel. Much to think about.

I am now at a standstill with eLecTricks until I resolve the situation. Fortunately, the weather is now too damn hot to consider any building anyway, so time to spend doing something else.
 
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This test mule does not have a traditional steel chassis ?



from here

I assume you are aware plywood can be bought down to 1/16th thickness ? [ actually less I have seen small pieces @ 1/64th but possible not as useful ? ]
 
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