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This Instructable shows you how to make a fairing (enclosure) for your bicycle/trike/etc from a combination of sheet plastic and some plumbing items (PVC and some pipe for supports). It goes hand in hand with the wind powered bicycle project that I am working on (to be posted a little later), and represents a continuation of my work on Thinkcycle. The technique I explain here can be applied to a wide variety of different items: greenhouses, fairings for other objects, sculpture, boats, etc. For vehicular applications this also forms a perfect backplane for the attachment of solar cells, etc. I'll cover how to do that in subsequent instructables.
There are lots of reasons you might like to have an enclosure on your bike: they can improve your aerodynamics, help with thermal regulation, serve as structural attachment points (for hanging lights, cycle computers, etc), but in my opinion the biggest thing is that it can provide a solution to the thing I hate most about winter biking, which is rain. At least part of the reason I have pursued this work is that there were no good options for getting my hands on a nice fully faired HPV, and nothing spells freedom like being able to get where you want to go at any time.
The basic idea for how to build this thing is to decompose your ideal shape (for the example I use an elongated ellipsoid as per some of the photos in step 2) into crescent segments using a little math (don't worry, the attached spreadsheet does all that for you, at least for the simple shape used in this tutorial). Then you can cut sheet plastic (0.080" PETG or polycarbonate) into correctly-sized pieces and then tape the outsides of them together. If you're very careful about the outline of the segments you cut, you can generate a very good approximation to the large shape you want (similar to the way the almond-shaped segments of a football are stitched together to make that three dimensional shape). Once the segments are taped together, you can fill a turkey baster up with pipe glue and run a bead of ;pipe glue along the joint. You let it harden, clean it up with a Dremel tool, and use it! For the shape I'm building, I also show you how to attach it to your bike. This is accomplished by cutting PVC T-joints in half and then using pipe clamps to attach them to the bike. The mounts have proven to be kind of tricky to get right, however, and there's some room for improvement in this department.
The motivation for this work was that I wanted to be able to make big three dimensional shapes for a number of projects but was unhappy with the existing techniques. Either they required a big oven (necessary for most vacuum and blow forming techniques) or were messy and generated lots of extra stuff (ex: cutting foam molds for fiberglassing). If you still want to go those routes, the technique I show you here can be useful in building supporting structures for use in jigs and whatnot.
The one note that I should add is that for reasons I will detail in the wind powered bike instructable (I may also call it a "Side wind safe" bike) you have to be careful about the design of your fairing if you are using a front-steered only bike (whether upright or recumbent). Basically, large fairings are unstable in high winds (so you want to keep the cross section from the side low by adding openings or making it very compact) on a regular bike. In the wind powered bicycle project I show you how to build a bicycle that will get around these shortcomings (you have to steer the front and the back wheels), but you can also attach this to a tricycle (just keep the width of the vehicle as wide as possible and the center of mass low). The fairing I build in this example is a test piece and probably too large for everyday use (although you could try cutting holes in it).
There are lots of reasons you might like to have an enclosure on your bike: they can improve your aerodynamics, help with thermal regulation, serve as structural attachment points (for hanging lights, cycle computers, etc), but in my opinion the biggest thing is that it can provide a solution to the thing I hate most about winter biking, which is rain. At least part of the reason I have pursued this work is that there were no good options for getting my hands on a nice fully faired HPV, and nothing spells freedom like being able to get where you want to go at any time.
The basic idea for how to build this thing is to decompose your ideal shape (for the example I use an elongated ellipsoid as per some of the photos in step 2) into crescent segments using a little math (don't worry, the attached spreadsheet does all that for you, at least for the simple shape used in this tutorial). Then you can cut sheet plastic (0.080" PETG or polycarbonate) into correctly-sized pieces and then tape the outsides of them together. If you're very careful about the outline of the segments you cut, you can generate a very good approximation to the large shape you want (similar to the way the almond-shaped segments of a football are stitched together to make that three dimensional shape). Once the segments are taped together, you can fill a turkey baster up with pipe glue and run a bead of ;pipe glue along the joint. You let it harden, clean it up with a Dremel tool, and use it! For the shape I'm building, I also show you how to attach it to your bike. This is accomplished by cutting PVC T-joints in half and then using pipe clamps to attach them to the bike. The mounts have proven to be kind of tricky to get right, however, and there's some room for improvement in this department.
The motivation for this work was that I wanted to be able to make big three dimensional shapes for a number of projects but was unhappy with the existing techniques. Either they required a big oven (necessary for most vacuum and blow forming techniques) or were messy and generated lots of extra stuff (ex: cutting foam molds for fiberglassing). If you still want to go those routes, the technique I show you here can be useful in building supporting structures for use in jigs and whatnot.
The one note that I should add is that for reasons I will detail in the wind powered bike instructable (I may also call it a "Side wind safe" bike) you have to be careful about the design of your fairing if you are using a front-steered only bike (whether upright or recumbent). Basically, large fairings are unstable in high winds (so you want to keep the cross section from the side low by adding openings or making it very compact) on a regular bike. In the wind powered bicycle project I show you how to build a bicycle that will get around these shortcomings (you have to steer the front and the back wheels), but you can also attach this to a tricycle (just keep the width of the vehicle as wide as possible and the center of mass low). The fairing I build in this example is a test piece and probably too large for everyday use (although you could try cutting holes in it).
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Signing UpStep 1Things You will need (and some you'll just want)
Materials:
PETG or Polycarbonate Sheets (you can order them from the following places: MSC, Mcmaster-Carr, Tap Plastics, Aircraft Spruce & Specialty, wick's, and probably a lot of local suppliers as well). You want the 1/16" thick stuff, and I went with 4'x4' sheets ($~20/a piece). This is the only somewhat obscure material, you should be able to get everything else from your local hardware store.
Packing Tape
Some long strips of cardboard suitable for transferring patterns
Spray paint if you're planning on painting it (optional)
Tools:
Aircraft Tin Snips (or DREMEL, etc)
Sharpie or other means of marking cardboard
Ruler and/or measuring tape (nice to have both, however).
Protractor for making baffles
Hacksaw or bandsaw for cutting PVC pipe for the supports.
Drill plus some small bits for drilling mounting holes in fairing.
A small wood rasp for doing cleanup (unnecessary if you have a Dremel)
C clamps for holding parts (at least a couple little ones) together.
Vise for holding PVC pipe.
Two options for bonding: (you have to pick one and get everything mentioned for that case):
I). ABS Glue, a turkey baster, masking tape, small bottle of MEK (methyethlykeytone), lots of newspaper, a glass jar, gloves and googles for cleanup, I would also recommend a mask: be very sure you have good ventilation. This option is essentially "chemical welding".
or
II). plastic welder (hot air, conduction or ultrasonic, you may need an air compressor if you go the hot air route) plus welding rod plus skill. This option can be a lot more dicey with transparent materials because any sort of heat distortion will ruin the transparency, but it is possible with a fed-rod design to get nice joints with it.
I decided to go with option (I) for this instructable because of the heat distortion issues (which are probably addressable with a fed-rod welder, I just don't own one). Some additional notes: ABS is not your only option for the glue base: a better option would be to use a material designed for use with PETG: I just used it because everyone has access to it and I believe it will hold up pretty well. If you want to make your own, I have elsewhere detailed some experiments using a coffee grinder to grind up your PETG cast offs and some MEK to dissolve them. I do not recommend this route unless you are really concerned with having a clear fairing on 100% of the surface (not a bad goal at all, just has a cost to it).
Knowledge:
You are going to have to be (or get! you can do this!) comfortable working with PVC pipe: both cutting and gluing it. There are a ton of tutorials online (for instance, here), so I'm not going to repeat them here, but always remember that you can do test pieces on a smaller scate to get a feeling for things. I highly recommend doing so whenever possible, you will see that for my first build I did not mask things properly and lots of the resultant joints were messy.
Optional: Dremel tool or equivalent (any small high speed hand grinder) plus tungsten carbide cutting bits (there's a photo below of the kind I like) for doing cleanup, plumb bob (you can make your own), drill press, V blocks, PVC pipe cutter. All of these tools are worth having and will make the workflow go a lot faster, but it is possible to get by without them if you're motivated to save money.
PETG or Polycarbonate Sheets (you can order them from the following places: MSC, Mcmaster-Carr, Tap Plastics, Aircraft Spruce & Specialty, wick's, and probably a lot of local suppliers as well). You want the 1/16" thick stuff, and I went with 4'x4' sheets ($~20/a piece). This is the only somewhat obscure material, you should be able to get everything else from your local hardware store.
Packing Tape
Some long strips of cardboard suitable for transferring patterns
Spray paint if you're planning on painting it (optional)
Tools:
Aircraft Tin Snips (or DREMEL, etc)
Sharpie or other means of marking cardboard
Ruler and/or measuring tape (nice to have both, however).
Protractor for making baffles
Hacksaw or bandsaw for cutting PVC pipe for the supports.
Drill plus some small bits for drilling mounting holes in fairing.
A small wood rasp for doing cleanup (unnecessary if you have a Dremel)
C clamps for holding parts (at least a couple little ones) together.
Vise for holding PVC pipe.
Two options for bonding: (you have to pick one and get everything mentioned for that case):
I). ABS Glue, a turkey baster, masking tape, small bottle of MEK (methyethlykeytone), lots of newspaper, a glass jar, gloves and googles for cleanup, I would also recommend a mask: be very sure you have good ventilation. This option is essentially "chemical welding".
or
II). plastic welder (hot air, conduction or ultrasonic, you may need an air compressor if you go the hot air route) plus welding rod plus skill. This option can be a lot more dicey with transparent materials because any sort of heat distortion will ruin the transparency, but it is possible with a fed-rod design to get nice joints with it.
I decided to go with option (I) for this instructable because of the heat distortion issues (which are probably addressable with a fed-rod welder, I just don't own one). Some additional notes: ABS is not your only option for the glue base: a better option would be to use a material designed for use with PETG: I just used it because everyone has access to it and I believe it will hold up pretty well. If you want to make your own, I have elsewhere detailed some experiments using a coffee grinder to grind up your PETG cast offs and some MEK to dissolve them. I do not recommend this route unless you are really concerned with having a clear fairing on 100% of the surface (not a bad goal at all, just has a cost to it).
Knowledge:
You are going to have to be (or get! you can do this!) comfortable working with PVC pipe: both cutting and gluing it. There are a ton of tutorials online (for instance, here), so I'm not going to repeat them here, but always remember that you can do test pieces on a smaller scate to get a feeling for things. I highly recommend doing so whenever possible, you will see that for my first build I did not mask things properly and lots of the resultant joints were messy.
Optional: Dremel tool or equivalent (any small high speed hand grinder) plus tungsten carbide cutting bits (there's a photo below of the kind I like) for doing cleanup, plumb bob (you can make your own), drill press, V blocks, PVC pipe cutter. All of these tools are worth having and will make the workflow go a lot faster, but it is possible to get by without them if you're motivated to save money.
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Did you observe any improvement in aerodynamics? I doubt you took it to a wind tunnel, but does it at least feel more aero?
I Notice that you don't extend your fairing down to the ground. Why?
How heavy is your fairing, in total?
So the big picture is that I'm still involved in a bunch of mathematics relating to fairings (including some Navier-Stokes tie ins), but I have not solved what I need to solve yet because it is super nasty.
My fairing, sans the supports, weighs something like five pounds, and is probably ten pounds with all of the bracketry.
I should caution you that no fairing of this style does well in high winds (the problem I am working on solving), so be careful when you take it out. If you're looking for something that is okay in wind, I'd recommend leaving the side panels off (or at least cutting some holes in them), so that there's some place for the wind from the side to go.
The improvements in aerodynamics are pretty startling if you use the bike a lot, especially over flats.
I'll put up some of my simulation work at some point, I have to do all of this outside of work for patent reasons so it is going a little slow. I'd be happy to recommend some supports if you do go ahead and build it.
If you change the minor axis field that changes the width of the shape as a whole (the width of the ellipsoid you're modeling), you can set it to any number you want. I'm glad you made me look at this because I caught a bug: both of the axis fields in the spreadsheet at the moment represent half the width (this part is clear) of and half the length (I mistakenly have it as representing the whole length) of the finished "ellipsoid".
The curves that you generate are placed onto four sides for regular segments. For the elongated segments you just add the equivalent amount of the elongation to the distance between the cut edges (basically insert a rectangle with a width equal to the elongation and a length equal to half the fairing circumference).
You can also change the Number of Segments Field (right now it's set at 8, which is the number of rulings we're giving our ellipsoid), you get more segments without changing the size of the fairing.