Fast and Free

Check it out! Wheels!

2008-11-15T09:11:00.000-08:00

There's a red support post holding it up, because the wheels aren't attached yet. Attaching the wheels is going to be a delicate operation to keep everything lined up and balanced, but here is the trike (less the seat), it's first real appearance.

Clever Solutions to Stupid Mistakes

2008-11-15T09:03:00.000-08:00

#1 Rear Wheel Misalignment
Okay, this is not so much of a clever solution. It's more a stupid solution to a stupid mistake.

The rear wheel must, of course, be mounted with the gears on the correct side of the bike, so it lines up with the gears on the crank set.

Once I did that, my problem went away.

#2 Chinese Crap
This solution is more clever. It turns out that the biggest problem with the bearing set was that the parts had been tightened too much. Once I loosened appropriate nuts, the sensation of riding on a cog railway went away.

Okay, a better solution would be to throw the Chinese crap away and buy real bike parts. This is a poor man's clever solution.

Stupid Mistakes #2

2008-11-07T09:55:00.000-08:00

I did it! I bought the kid bikes from which I will harvest the front forks. Walmart kid bikes are much cheaper than buying the parts from even online bike shops, and who knows? I could even put the rear section together with the front wheel from the mountain bike and make a delta trike later.

I got what I paid for, which is Chinese crap. The steering and the axle turn like in place of ball bearings, they have twenty-sided dice. If you apply a little force, they go bump-bump-bump, about 3-4 bumps to go through an eighth of an arc. Swell.

Stupid Mistakes #1

2008-11-07T09:50:00.000-08:00

Dang!

Anyone else trying this, learn from my supid mistakes. When attaching the rear fork into the bike frame, do it with the wheel in the fork. I just put the wheel into the fork, and it's all but impossible to keep it from rubbing up against either the bamboo, the brake, or both.

Now I have to cut off the rear fork and put it back on again.

More Steering

2008-10-25T06:11:00.000-07:00

Now what I need to decide is how to mount the steering mechanism. Options:

The easy way, relatively speaking, is to cut out the steering system from the old bike and affix it under the seat. Unfortunately, the old bike's head is longer than the space where it needs to go, so this is out.
I could cut off the top of the old bike's head. This would allow me a solid steel cylinder to put the yoke into, and a system of bearings to make it turn easily. I would need to devise my own way to keep the yoke from pulling up out of the head, and I would lose some of the anti-wobble effect of the longer head. Not sure the impact of losing the bottom system of bearings, beyond these two. Also, the yoke is too long for the space, and would also have to be shortened.
A variation of # 2: I could cut out the middle of the head, and attach top and bottom together. Would give me the bottom bearings, but would make the head a weak-point. All I could do to join them would be to apply epoxy, and this might also compromise the free turn of the handlebars.
Find a smaller head. The main problem here is the hassle and cost.
I could attach the handlebars to a perpendicular pole, then put a simple pin through the pole, and be done with it. Say, use a short bolt, one of those quarter-inch ones that has a length without threads. There'd be more wobble than either of the above, and it wouldn't have the bearings to turn so nicely around, so precision, high-performance steering is out. But it's by far the simplest.

Steering

2008-10-21T12:11:00.000-07:00

There are two basic formats for steering that I can think of, illustrated in the diagram above. The green bar is the handlebar, the blue dots are joints, the red are steering bars. The triangle represents the stem of the yoke that turns the wheels, in black. The handlebar turns about its center, not marked.

The first thing I think about them is that the push-pull format seems to work best when the steering is significantly behind the wheels, although I have seen other designs that use the lateral design from behind, and use a bent bar (the long red one in my diagram) to reach the wheels.

I think the real difference is the travel, how far you turn the handles to turn the wheels. I think the push-pull method would make the wheels turn quickly with very little motion of the handlebar, not a good thing. In the lateral method, the shorter the little bar (red) that connects the handlebar with the long red bar, the longer the travel of the handlebars.

It's also the method I've seen on pro trikes.

A Place to Sit

2008-10-04T06:05:00.000-07:00

The crank is secure. Secure enough that I can sit on the bike, put my feet and the weight of my legs on the pedals, and pedal. The first of many tests.

Which brings me to the place of making a more comfortable place to sit. I have a fine plan to make the seat, two pairs of poles joined at an obtuse angle, and joined by two parallel poles perpendicularly, and a back and seat made of nylon. But the big questions are where to put it, and exactly how wide an angle, and how large must the seat and back be.

I answered the last question by measuring some chairs and the placement of my butt on them. I didn't want to make the seat too large, as I didn't want my pumping legs to chafe agaisnt a seat edge. I want it under by butt, not my legs. I answered the second question by sitting against a board and reclining it to a good angle, then replicating the angle.

I thought the last question would be the easiest, because I could simply put the seat on and secure it. But I find that the placement of the seat is dictated by the placement of the pedals and length of my legs, and I fear that the place dictated is so far forward as to make the bike front-heavy. Depending on the weight of the rear-mounted engine, during a hard stop it could try to do a nice face-plant on the pavement.

I was imagining the only solution would be to cut off the nose and shorten it, but while I was typing it occurred to me it would be far easier, and involve less threat of weakening the structure, to cut off the crossbar and move it forward. Problem solved, thanks for listening.

Splicing in the crank supports

2008-09-20T16:11:00.000-07:00

This is a close-up of the joint for the crank support poles. The one that joins to the lower pole is cut on the angle and butted together. A slot is cut in both poles, sufficient to accept a 3/16" ply, which is carefully cut to the precise angle required, making a long, skinny triangle. Epoxy is applied to the edges of the slot and the butt joint, it is assembled and bolted near the joint. A wooden pin (not shown) will be inserted near the points of the triangle. The wire wrapping is to prevent the bamboo from splitting at the cut.

If I do it again, I will cut a slot through both sides of each pole, and have the triangle pass all the way through. As it is, the ply can wiggle slightly inside the poles, and depends on the epoxy to prevent this.

The upper bracing pole is cut on a very careful angle (took me several tries to perfect), and rounded out a bit with the dremel for a firm fit. I also cut into the pole it connects to, so that it can butt up against a solid edge, but not so far as to open the cavity of the pole. I single bolt holds it very firmly, although I will probably add epoxy as an additional measure.

My God! It actually looks like something

2008-09-19T17:06:00.001-07:00

Top View

I know it's a little hard to see, with the stray bamboo pieces, and the 2x3 support the tail. It was hard to get a good view on it in the basement. But you can see the rear wheel fork and the crank in place.

Rear Wheel Fork

You can see here the bolts into the bottom side of the rear fork, that connects it to the hardwood dowel that is bolted to the bamboo. The gray line on the steel is epoxy that seals a cut I made when I though I could get the bamboo itself into the steel. Dumb idea. There's a half-circle cut-out in the top bamboo pole that should keep the rear side of the fork from shifting fore-and-aft, and a bolt that holds the fork firmly into the cut-out.

Crank

Not finished yet, there'll be a second support pole connecting to the second top pole of the frame, but here you can see the plan. The crank is sandwiched between curved cut-outs. The support poles cross, and when the last support pole is added I will pin them together, which will prevent them from spreading and releasing the crank. That and a generous amount of epoxy.

The crank is heavy, and reminds me how much weight I am saving using bamboo. I think the crank weighs more than all the bamboo in the frame!

Crank

2008-09-08T08:01:00.000-07:00

I cut the crank off of a mountain bike. I now have a cylinder with little metal tube remains pointing in three directions. My plan is to secure it between three short poles with a joint known as a "bird beak," where the poles cross and pinch the cylinder between them. Excellent idea, but execution is difficult, since the poles need to be positioned with some tension. I've tanken the first step:

I cut two slots in one of the poles, that precisely correspond to the edges of the widest tube. Then I epoxied the crank onto the pole. Next I'll attach this pole, then add the others. The epoxy will allow the "unpinched" crank to hang in the air from just one pole.

Metal-bamboo joints

2008-09-07T15:49:00.000-07:00

Well, I've finally done it. I've joined bamboo to metal. Someday maybe I'll tell the story of my adventures trying to drill hardened steel, and how I wound up with three 3/16" drill bits. But I slid one end of a 5/8" dowel into a bamboo pole, and the other into the tube of the bike, where it fit snuggly. Drilled twice through both ends. Took it apart, smeared the dowel with JB Weld (epoxy), put it back together and bolted it fast. It's permanently joined, now.

What I actually connected was the rear half of the rear bike triangle with the support poles.

Third Pole Photos

2008-09-07T10:30:00.000-07:00

Below I talk about how I added the third pole by making a triangle and insterting the point into a mortise in the third pole. Here are pictures.

hacksaw vindicated

2008-09-03T16:18:00.000-07:00

I tore apart another hacksaw blade. But, being the try-it-and-see sort of guy I am, I tried a third. A different hacksaw blade. And wouldn't you know, the problem was the cheap-a** blade that came with my cheap-a** saw. I've made three cuts with a better quality blade and no sign of dulling.

How much bike to use

2008-08-28T07:58:00.000-07:00

Today's question is: do I cut off the entire rear triangle of the salvage bike, or do I only use half of it? That steel is heavy! Moreover the connection into the main bike is tricky, since I foolishly did not leave a long tail on the lower pole, and the bracing poles interfere with connection parts.

I have long tails on the upper two bars. This is what I leaning toward: I will use half the lower bar of the triangle, connecting the cut-off ends to a bamboo fork I can splice into the main frame. I will use the entire rear bar of the triangle, to have the mounting space for brakes and other items. The tails of the upper bamboo can make nice lap joints with the rear triangle bar. The bamboo, with a little shaving, can fit into the cut ends of the lower bar. A little diagonal bracing and this should be a strong mount.

On the Other Hand

2008-08-28T07:50:00.000-07:00

Maybe a hacksaw is better. I'm always checking and trying things. Had a tight space where the 1" wide dremel cutting wheel didn't really fit. So I used the metal cutting blade on a keyhole saw and quite easily finished the cut. So for the next tube, I tried the hacksaw, and went faster with less dust.

Caveat: I didn't check the blade before I started, but it was ruined when I was done. 3" of teeth were worn away. If this holds true, I'm going to prefer to go through 2-3 dremel wheels (15c each) rather than 1 hacksaw blade.

The incomparable dremel

2008-08-26T09:16:00.000-07:00

I had assumed that I would have to use a hacksaw to cut up the bicycle, and was not relishing the thought of the time spent going ree-ree ree-ree on hardened steel. If a hacksaw could even cut hardened steel. I have a scroll saw with a metal blade, but that was a slow screaming terror when I tried to use it on aluminum.

Behold! The indefatigable dremel cuts through hardened steel using only its ordinary emery board cutter. The cutters wear out fast, but they are working!

Destruction!

2008-08-24T18:59:00.000-07:00

Part of my plan includes using bicycle parts. I plan to use the aft section of a bicycle to hold the rear wheel, and the steering hub and fork of two kiddie bikes to hold the fore wheels. I've got the adult bike, so today I started disassembling it. What fun. Had to break the chain to get it off, but I figure I'll have to link two-three chains to deal with the longer length, so, no big deal their. But getting off all the fancy new components (bicycles have changed a lot since I was a kid) was a treat.

Progress

2008-08-21T16:02:00.000-07:00

As you can see in the photo below I have added the supports for the third pole so I will have a strong, triple poled frame. I built these braces a little differently than the first, as you can see from the close-up below.
I cut each brace pole on a 30deg angle, and drilled their mortises at a similar angle around the main poles, so that they meet in the middle snuggly. Only one of them required any real trimming to make snug. Then I make three oval holes in the third pole, set it down over these braces, and secure with a single pin through both braces. This oval hole is on the large side. To keep it from getting too large, and weakening the pole, I notched the peak of the braces.

It all worked very nicely. I don't have pictures of the main frame assembled, yet, but it is almost done. Next will come building the support for the front wheels.

Tools

2008-08-14T15:43:00.000-07:00

These are all the tools I found I needed in my work. I'll try to keep this updated, and not include any tools needed for things I tried but didn't use.

Power Drill, inc. 1/2" speedbore bit
Dremel (rotary cutting tool), inc. cutting wheel, and large and small sanding drums
miter saw
wood chisel, 1/2" or so
mallet or hammer
coarse sandpaper
machine screws (bolts) with locking washers and nuts, 8/32, several 2", some 1", 1&1/2", and a couple 2&1/2"
screwdriver
wrench
hacksaw
keyhole saw with metal-cutting blade.

Bracing the frame

2008-08-09T05:14:00.000-07:00

I've been adding diagonal braces to the frame poles. It took some experimenting to determine the best way to do this, but this is where I settled:

I use a mitre saw or coping saw to cut two 45deg cuts opposing each other on the inside of the poles, at each end of each brace. These cuts go down only a 1/16th of an inch, not even enough to go through the bamboo wall.
I use a 1/2" chisel to cut out the opening.
I use a dremel or rotary cutting tool with the drum sander to shape one side to the shape of the brace pole. The other side, which takes the end of the brace, is kept flat.
When I have two good openings like this at the proper places on the two poles, I measure and cut the diagonal brace from 1/2" bamboo.
I firmly hold the brace in place, and drill through the frame and brace at a slight angle.
I insert a 2" machine screw (bolt) through the hole and bolt it together.

The use of bolts unfortunately adds a noticeable amount of weight, but appears required. I suppose I could mortise this joint as well, and secure with a pin, but drilling at a 45deg anle into the bamboo would be challenging, and there would be complications, such as the difficulty of getting the brace in between the poles, or of passing it through the poles.

The frame is started!

2008-08-05T19:35:00.000-07:00

I have constructed the first piece of the frame!

This is the two lower poles that for the main part of the frame, which will make a triangle-beam with a third pole. The 1" bamboo poles are joined by short lengths of 1/2" bamboo, mortised and pinned, as shown in this photo:

The wire is 18 gauge galvanized steel I wrapped around the bamboo to prevent/repair splitting when the snug crosspole is inserted (an issue). The pin is a 3/16" hardwood dowel that prevents the crosspole from coming out.

This entire construction has nothing to do with my plans, and indeed contradicts advice I gave elsewhere: a speedbore can be used successfully on bamboo, if the bamboo is prevented from vibrating with a firm parrallel clamp. I decided to go with this joinery option, thinking that I would use several half-inch bamboos for triangulation anyway. Other sites described this sort of motising as a strong joint, and it appeared to be the simplest and least fussy option. Here I go!

The Model

2008-08-05T19:22:00.000-07:00

I said I had made a model. Here are the photos. Note that I made a number of changes to the design after making this model. Which I will note after the pictures:

The most significant change I made was to invert the triangle formed by my three poles. That is to say, I put one pole on top and two along the bottom. Why?

It's hard to see in this photo, but the rear axle is at a noteworthy angle from perpendicular. Because there is no continuous bar from the main frame to the axle, there is a large amount of play, and a slight inaccuracy in the length of the poles or squareness of the joints easily become noticable errors in alignment. By using two poles along the bottom, these become straight by definition, and the number of variables is reduced.

Joinery Experiment

2008-07-31T08:42:00.000-07:00

I just tried both the methods listed below (Joinery 2 & 3). For the hanger-bolt joint (joinery 2), I omitted the epoxy, since I hoped to reuse the materials. For the mortise-and-tenon joint (joinery 3) I used a piece of 1/8" ply cut in a modified rectangle for the tenon and bamboo skewers for pins. The modification was essentially a tail, an extention of the rectangle at a width slightly less, so that it could slide inside the cavity of the crosspole, giving more pinning length while requiring the bamboo to be cut less.

Hanger-Bolt Joint
Joining caused splitting of the hardwood dowel, and subsequent stress and splitting of the crosspole. Joint was not square. No problems with compression of the bamboo from the bolt. There was minimal wiggling in the joint, but when I applied pressure the screw of the hanger-bolt pulled out of the dowel, due to its split.

The non-squareness of the joint was likely due to the difficulty I had centering the hole for the screw-side of the hanger-bolt, and making the hole perpendicular. Also, I did not perfect the curvature of the crosspole cut to fit the main pole. The splitting dowel was encouraged because of the difficulty getting a snug fit between the dowel and the bamboo cavity.

Also, screwing in the hanger-bolt is challenging.

Mortise and Tenon Joint
Fitting the mortise-and-tenon to each other was easily done with a dremel. Getting a tight fit was not difficult (the hanger bolt pulls the parts together in the other joint, in this joint this must be done manually). Pins held without glue. The resulting joint was square with minimal wiggling. However, when force was applied, the wiggling gradually increased. Eventually, pins cracked, one failed entirely, and the tenon tail split off.

Conclusions
I like the mortise-and-tenon joint, despite its failures. 1/4" ply and larger diameter pins (bamboo chopsticks? wood dowels?) will improve strength. Epoxy in the joint will not only give adhesion, put will also fill gaps and minimize the wiggling. Triangulating joints will also minimize wiggling. If wiggling can be eliminated, the progressive growth in wiggling should also disappear.

Most important, of course, was the ease with which I was able to get a good-looking joint. Precision is not a strength of mine, so any method that doesn't require me to hold my drill perfectly vertical is a better method.

Bamboo Joinery 3

2008-07-31T06:14:00.001-07:00

Here is an alternative joinery technique I just found on the web. It has a number of advantages over the technique I planned in the previous post:

It doesn't rely on glue anywhere
It doesn't use expensive hardware (hanger bolts, at 50¢ each, add quickly)
It doesn't compress the bamboo as a bolt does, something the literature says is not good for bamboo.
It doesn't require one to make a precise fit between a dowel and the bamboo interior.

On the other hand, it does require one to make a careful joining tenon, to drill the bamboo four times rather than one (which has proven tricky for me), and to fit pins precisely. Here it is:

Use a dremel cutting wheel or similar tool to cut a slot in the main pole, the dimensions of the tenon you will make. Make another cut in the end of the cross-pole the length of the tenon.
Make a tenon out of plywood the thickness of the slots (mortises) you have just cut. I show above a triangular tenon, which would give more support for bending of the cross-pole, but requires the slot on the main pole to be slightly longer than the joint, leaving it visible. A rectangular tenon, the width of cross-pole, would not have this defect. Insert this tenon into the two mortises and close the joint.
Drill four holes through the bamboo and the tenon, making sure that the joint is very tightly closed as you do so. Two holes lengthwise on the crosspole, and two lengthwise on the main pole.
Cut four pins and insert into the holes. You may use a weatherproof glue to hold the pins in place. This glue does not hold the joint: no force applied to the joint is resisted by the glue, but it does prevent the pins, that hold the joint, from working loose. What to use for the pins? Smaller-diameter bamboo is recommended. In some applications, bamboo skewers from grocery aisles are all that is needed, and have the advantage of being a consistent size. I think they are too small for my purposes, however.

I neglected to include in this illustration that you ought to first cut the crosspole end into the shape of the bamboo mainpole (see Bamboo Joinery 2, below).

Bamboo Joinery 2

2008-07-24T06:21:00.001-07:00

Making a T joint:

Cut the end of the side pole into a curve closely fitting the cross-pole, using a coping saw.
Take a 1" length of a hardwood dowel that fits snugly into the bamboo cavity, apply a strong, weatherproof glue such as Weldbond Outdoor wood glue, and insert into the end of the side pole.
Bore a hole into the dowel in the side pole (use a bit the diameter of the shank of your hanger bolt screw-side) and another through the side of the cross-pole (use a larger bit, the diameter of the threads of the hanger bolt bolt-side).
Drive the screw end of the hanger bolt into the dowel, and insert the bolt end into the cross-pole.
Secure the bolt with a washer and nut.

The Motor

2008-07-23T15:10:00.000-07:00

Many of you may be wondering about the motor:

That part is simple. I buy a wheel with a motor attached, put it on the bike, and I'm good to go. A number of good motors are made:

Bionx
Electric rider

I think I'm going for the Phoenix Cruiser from Electric rider, because it is fast (30mph), but has more power for hills (important in Vermont) than their faster Racer model.

The Bionx system has regenerative braking, which I like, but it also has a system to prevent the bike from exceeding 20mph, which is the legal maximum, yes, but... when's the last time you bought a car that couldn't go faster than 65?

Bamboo Joinery

2008-07-22T05:05:00.001-07:00

The official way I read about doing bamboo joinery is with bins and hooks and bolts. Say, to make a T-joint, you would put a pin through the stem of the T, bend one end of a threaded rod into a hook, insert the hook into the end of the stem and hook the pin, then put the other end of the threaded rod through a hole bored in the cross bar and secure with a nut.

The problem is, my bamboo is so narrow there is no hook can be inserted into the hollow.

My solution: cut 1" pieces of 1/2" dowel (or other size that fits snuggly inside the bamboo cavity. Glue one piece into each end of the bamboo with a strong, weather-proof adhesive, such as Weldbond's outdoor wood glue. Bore a hole into the butt end of the dowel, and insert a hanger bolt (one of those bolts with a screw on one end and the bolt on the other. Bore a hole through the piece you want to join to it, put the bolt through, and secure with a nut.

This method should be equal to the official in sheer or compression. If pulled apart, the joint is dependent on the strength of the glue. I think I might use an epoxy between the two part, such as JB Weld, to help. This would make two distinct glue joints which each support each other: this chain is as strong as its strongest link.

Simplify

2008-07-21T08:19:00.000-07:00

Okay, on second thought, the hole saw doesn't work. Spent $25 on a new hole saw the right size (1"), just rip the bamboo apart.

New approach: the coping saw. I use one of my successful hole saw bamboos as a template, trace it, and cut the next one out by hand. It goes really fast, doesn't require pre-drilling or extension cords, and NEVER splits the bamboo.

Working Bamboo

2008-07-19T16:10:00.000-07:00

This is my insightful discovery: bamboo is different than wood.

Bamboo is very strong in terms of bending and load bearing. But let something sharp strike it across the grain, and WATCH OUT!

Bamboo handles like a bundle of silk threads running the length of the pole. It is prone to splitting.

Don't use a speed bore on bamboo. The moment that spinning blade touches the bamboo, POW! split if not shatter.
Be careful using a large-bore (3/16"+) drill bit. A very gentle touch works, but push too hard and it splits.
Predrilling with small bore bits helps. Ironically, the spear point on a speed bore has never caused trouble for me, and I use it to pre-drill. Just have to stop before the blade touches.
Use small-tooth saws. I used a mitre saw.
I wouldn't dare nail it.

Don't know if this will work, or if I'm off on the wrong direction. We'll check in again.

Poles Poles Poles

2008-07-18T15:40:00.000-07:00

Just received my shipment of bamboo poles. I ordered 6'x1" tonkin poles. I'm really excited, but I have to say: cylindrical things always look a lot thinner than they measure. I'm wishing I'd order 1&1/4, or even 1&1/2.

On the upside, my daughter and I could sit together on two poles, and even wiggle a little, so I think it will work with my 3 pole design.

I ought to put three poles together and jump up and down on them, but I can't bring myself to try it.

Steering mechanism

2008-07-14T14:27:00.000-07:00

Another decision was how to rig the steering when your technical skills are limited. Most Tadpole Trikes (two front wheels) use a design where the crossbar of the frame heads out toward the axle, then has a hinge. This is clearly the superior design, but I don't know how to find such a hing. I don't think door hinges will work. So my thought was to take the front end of a pair of kid's bikes, and have the crossbar connect to the cylinder.

Use a bike with a small front tire, say 16", so your bike doesn't look like this:

The downside is this involves a bamboo-metal connection, but we'll deal with that in a bit.

Trike: one in front or one in back?

2008-07-14T06:48:00.000-07:00

I knew I wanted a trike so I felt safe on slippery roads, so it felt more car-ish. I bike is simpler but I wanted a trike. However, trikes do have a stability problem. The traditional trike design, called a "delta," with one wheel in front, can easily flip at high speeds. This illustration shows why:

A. Trike moving forward. Blue arrow indicates interia keeping it moving forward.

B. Front wheel is turned, creating a deflection force (pale blue) for the front of the trike.

C. The trike starts to turn. Inertia still wants the trike to move forward, the wheel is still deflecting the trike front to the right. Notice that inertia is now moving across the line between the front wheel and the rear left wheel. This line become a fulcrum for the bike to tip over. In a car, the weight of the car is shift to the front left wheel. In a delta trike, this wheel doesn't exist.

D. Inertia keeps the bike moving forward, by adding a simple torsion to the bike mass, known in highways safety lingo as a roll-over, or just a crash.

In a trike with one rear tire and two front tires (called a "tadpole"), the left front tire does exist, and the rollover is prevented.

Other factors, pro and con:

A delta trike requires a more complex power train, some sort of differential to allow the rear tires to spin at different rates in a turn, and or a single axle to transmit power to both tires.
A tadpole trike requires a more complex steering mechanism, so the front wheels turn in unison.
One poster has said that tadpoles are more inclined to fishtail.
The majority of trike designs available from more technically informed people are tadpoles.
Tadpoles look cool.

I'm gonna make a tadpole.

Frame Design

2008-07-13T18:13:00.000-07:00

I really know very little about bamboo as a building material. Exactly how thick a pole of what species do I need? My cursory research didn't reveal "how strong is bamboo" so I did what Idle Dads do, which is to get some and see. I need to keep costs down, but I figured that, depending on what I found, I could probably adapt the design. I ordered 1" dia. tonkin poles from http://bamboofencer.com/, which doesn't have surcharges for small orders and ships from nearby Massachussets.

Here are the three basic frame designs:

The Single Pole, or cross design, is what to use if the bamboo proves very strong and sufficiently rigid. In the picture above, the rear wheel is on the long end of the cross, the front wheels on the ends of the crossbars, and the crank and pedals on the bent tip (the crank needs to be above the seat, for various reasons).

The Double Pole design should be much stronger, and stiffer in the vertical dimension. Not shown in this sketch are short lengths of bamboo connecting the two principal poles. The weakness of this design is that there is no stiffening in the horizontal direction, nor from twisting. This means loss of some of the shock absorbency of bamboo, and some wiggle in steering. It is possible to put the two poles side-by-side instead of over-and-under, which would restore the shock absorbency and stiffen the steering, but the trade of would be loss of strength in the vertical direction. Since this is the direction of stress from a pothole hit at 30mph with 180lbs of Idle Dad aboard, it would seem to be the primary need for extra reinforcement.

The Triple Pole design is stronger in all directions. I can't imagine that it won't be strong enough. It loses some shock absorbency, and it is significantly more complex to build than the others, but is the assurance that my 1" poles will be adequate. The picture above may be tricky to see, but I am finishing a model that I will post soon.

Metal, Plastic, or Bamboo

2008-07-13T18:03:00.000-07:00

Everyone else makes them out of metal. But to do metal you need to weld or "braze" pipe together. Before I started this project I'd never even heard of "brazing." Another posibility is ABS pipe, like water pipes are made of nowadays. I decided against plastic for several reasons:

I don't like plastic
It gets brittle in cold weather and I live in Vermont
I've heard complaints about how it weathers

I wasn't sure if the bonding in plastic weld--adequate for carrying water--would be adequate for carrying 180# of Idle Dad 30 mph over potholes.

Bamboo suggests several advantages to me.

It looks cool
It's natural flexibility will provide shock absorbancy over frost heaves.
I read about how to do bamboo joinery and--unlike brazing--it sounds like something an Idle Dad can do.
It is a renewable resource and doesn't offgas solvent vapors
I've always liked bamboo

As you can see, my resources are all based in good engineering and sound logic

Do You Need Fast and Free?

2008-07-13T06:43:00.000-07:00

Is this you?

You can't afford a Prius
You can't afford gas
You aren't an engineer
You don't have the gumption to bike around town
You like to fiddle with things

If so, you're like me. And then maybe you, like me, are intrigued at the possibility of electrically-assisted bicycles. Vehicles that can travel 30 mph without any effort, even faster if you get exercise while you travel. They can have three wheels to be stable in slippery conditions, and even be enclosed to be dry in the rain. They don't burn a drop of gasoline.

There are a number of places to buy such things. Electricrider.com, exertrike.com. But I'm poor, and I like projects. So I decided to build one.