3-wheel tandem

I became interested in articulated 3-wheel (inline) tandems ever since
the days when I pulled my daughter on an Adams trailer bike. We kept it
up until she hit the Adams recommended weight limit of 100 lb. Most of
our riding was off-road, actually on very "technical" single track
trails. I came to appreciate the advantages of 3 wheels over 2 on a
tandem, at least for off-road cycling.

Since that time I have given a lot of thought to an "adult" sized
trailer bike approach to a tandem. I started fooling around a couple of
years ago, finally coming up with an approach that was ridable, but I
wasn't too happy with it. This year I made a change which improved
things dramatically and resulted in a bike that rides very well.

The basic approach (which many have tried) is to use 2 bikes, spreading
the front fork of the "trailer" bike to fit over the axle of the front
(tow) bike's rear wheel. I took a beefy steel 26" fork and spread the
legs, then bent the dropouts to vertical. I fitted a long axle to the
rear hub of the "tow" bike. Originally I used a (hollow) tandem axle,
but switched to a solid piece of threaded high strength rod, mostly to
get some extra length.

Each fork leg is locked to the axle by 4 (greased) washers. The washers
are 1" diameter which form an interference fit in the lawyer lips, 2
washers on each side of the fork dropout, so 8 washers in all. I use
track nuts to load the washers, with a jam nut outboard to prevent
loosening. I just tighten the track nuts until there is resistance to
vertical articulation in the fork then lock the jams against them. The
net result is that a universal joint is formed, one axis of rotation
around the axle (pitch), the other (yaw) around the headset.

On my first iteration last year, I left the trailer bike's original stem
and handlebars on. The resulting performance bothered me. After a lot of
thought and experimentation I realized that the problem was that the
coupling wasn't torsionally rigid enough and the system acted like 2
masses coupled with a torsion spring. In other words, once it started
oscillating, it was difficult to damp out. I convinced myself that the
lack of rigidity wasn't in the fork of the trailer bike but rather in
the rear triangle of the tow bike. I thought of various ways to stiffen
things, but everything I came up with seemed complicated and I was ready
to abandon the idea. Close, but no cigar. We rode it, but I wasn't happy
with it.

Over the winter, I had an idea that seems obvious in retrospect. I moved
the "stoker's" handlebars from the trailer bike to the seatpost of the
tow bike. Of course that's the common arrangement for conventional
tandems, but I hadn't thought about it with a trailer bike. The obvious
problem of interference while articulating was solved by using "ape
hanger" bars, which, with a standard size, allowed me to locate the rear
hand positions exactly where they had been.

This new configuration made a night and day difference in handling.
Essentially, the body of the stoker becomes an element of the linkage.
Any force the stoker applies to the bars (pedaling reaction force, etc.)
couples directly and rigidly to the tow bike, as it would in a
conventional tandem. Any torsional oscillation that develops is quickly
and naturally damped out by the stoker's upper body. While the assembly
was always stable at high speeds, now it became stable at low speeds, too.

We've got around 200 miles on the prototype so far. We haven't ridden
any "real" off-road (singletrack) yet, but we have done unpaved trails,
urban riding in traffic and narrow bike paths, including some pretty
steep climbs. My stoker was comfortable enough to ride out of the saddle
right away, and the bike(s) is stable enough that I didn't really even
notice. She's now frequently riding no hands and swiveling for the
scenery, and I'm not getting the upper body workout I was with rev. 1,
still not riding no hands myself, but one handed comfortably. The bikes
I used were some clunkers (particularly the trailer), so the total is
somewhat heavier than a tandem, but not too bad, considering.

I've paid careful attention to handling characteristics. I have a lot of
experience with trailer and trailer bikes, particularly in extreme
conditions. I was somewhat concerned that having the 2 articulation axes
offset might introduce some odd motion couplings (e.g. going over a bump
while in a hard turn). There's a little bit of that, but not enough to
be an issue. All in all, it handles predictably -- braking, turning and
going over large bumps. I hope to log some miles on real trails this summer.

Safety has been my first concern, My stoker (wife) is used to some
experimental risk, but I'd feel really bad if I crashed her. The fork
coupling seems a little home brew, but it has been secure, never
loosening between my frequent checks. Putting the stoker handlebar loads
on the tow seatpost takes most of the twisting load off the tow bike's
axle and rear triangle. The bracing angle of the (spread) fork legs
makes most of the load in tension or compression, the additional
(static) axle load is modest, perhaps 40% of stoker's weight. The axle
overhang is minimal. The moment on the stoker stem and bar combo is
large, and that is some concern, but I have it mounted low. I've been
taking test rides slowly at first, checking frequently for problems. So
far, so good.

The tow bike is also my utility bike, so for now I'm taking it in and
out of tandem mode fairly frequently. The good news is that it's a 5
minute operation. I left the rear brake on the trailer bike hooked up to
the stoker's bars. We did some long steep descents where we used that
brake as a drag brake to control speed and I used the other 2 brakes in
the corners. Again, similar to a common tandem set up, but with the
actual braking (friction) and thermal load spread over 3 wheels. Another
advantage is having independent cranks. Since neither of us are
experienced tandem riders, that made the learning curve substantially
shorter. Perhaps the biggest feature is the cost. Being exceptionally
large myself, and us well over average for a team weight (close to 400
lb), a conventional tandem would be somewhat pricey, even by tandem
standards. So far I have perhaps $100 in this vehicle.

Some (Flicker) pictures:

http://tinyurl.com/3624ujz
http://tinyurl.com/2w6xpsl

On Jul 26, 6:45*pm, Peter Cole wrote:
I became interested in articulated 3-wheel (inline) tandems ever since
the days when I pulled my daughter on an Adams trailer bike. We kept it
up until she hit the Adams recommended weight limit of 100 lb. Most of
our riding was off-road, actually on very "technical" single track
trails. I came to appreciate the advantages of 3 wheels over 2 on a
tandem, at least for off-road cycling.

Since that time I have given a lot of thought to an "adult" sized
trailer bike approach to a tandem. I started fooling around a couple of
years ago, finally coming up with an approach that was ridable, but I
wasn't too happy with it. This year I made a change which improved
things dramatically and resulted in a bike that rides very well.

The basic approach (which many have tried) is to use 2 bikes, spreading
the front fork of the "trailer" bike to fit over the axle of the front
(tow) bike's rear wheel. I took a beefy steel 26" fork and spread the
legs, then bent the dropouts to vertical. I fitted a long axle to the
rear hub of the "tow" bike. Originally I used a (hollow) tandem axle,
but switched to a solid piece of threaded high strength rod, mostly to
get some extra length.

Each fork leg is locked to the axle by 4 (greased) washers. The washers
are 1" diameter which form an interference fit in the lawyer lips, 2
washers on each side of the fork dropout, so 8 washers in all. I use
track nuts to load the washers, with a jam nut outboard to prevent
loosening. I just tighten the track nuts until there is resistance to
vertical articulation in the fork then lock the jams against them. The
net result is that a universal joint is formed, one axis of rotation
around the axle (pitch), the other (yaw) around the headset.

On my first iteration last year, I left the trailer bike's original stem
and handlebars on. The resulting performance bothered me. After a lot of
thought and experimentation I realized that the problem was that the
coupling wasn't torsionally rigid enough and the system acted like 2
masses coupled with a torsion spring. In other words, once it started
oscillating, it was difficult to damp out. I convinced myself that the
lack of rigidity wasn't in the fork of the trailer bike but rather in
the rear triangle of the tow bike. I thought of various ways to stiffen
things, but everything I came up with seemed complicated and I was ready
to abandon the idea. Close, but no cigar. We rode it, but I wasn't happy
with it.

Over the winter, I had an idea that seems obvious in retrospect. I moved
the "stoker's" handlebars from the trailer bike to the seatpost of the
tow bike. Of course that's the common arrangement for conventional
tandems, but I hadn't thought about it with a trailer bike. The obvious
problem of interference while articulating was solved by using "ape
hanger" bars, which, with a standard size, allowed me to locate the rear
hand positions exactly where they had been.

This new configuration made a night and day difference in handling.
Essentially, the body of the stoker becomes an element of the linkage.
Any force the stoker applies to the bars (pedaling reaction force, etc.)
couples directly and rigidly to the tow bike, as it would in a
conventional tandem. Any torsional oscillation that develops is quickly
and naturally damped out by the stoker's upper body. While the assembly
was always stable at high speeds, now it became stable at low speeds, too..

We've got around 200 miles on the prototype so far. We haven't ridden
any "real" off-road (singletrack) yet, but we have done unpaved trails,
urban riding in traffic and narrow bike paths, including some pretty
steep climbs. My stoker was comfortable enough to ride out of the saddle
right away, and the bike(s) is stable enough that I didn't really even
notice. She's now frequently riding no hands and swiveling for the
scenery, and I'm not getting the upper body workout I was with rev. 1,
still not riding no hands myself, but one handed comfortably. The bikes
I used were some clunkers (particularly the trailer), so the total is
somewhat heavier than a tandem, but not too bad, considering.

I've paid careful attention to handling characteristics. I have a lot of
experience with trailer and trailer bikes, particularly in extreme
conditions. I was somewhat concerned that having the 2 articulation axes
offset might introduce some odd motion couplings (e.g. going over a bump
while in a hard turn). There's a little bit of that, but not enough to
be an issue. All in all, it handles predictably -- braking, turning and
going over large bumps. I hope to log some miles on real trails this summer.

Safety has been my first concern, My stoker (wife) is used to some
experimental risk, but I'd feel really bad if I crashed her. The fork
coupling seems a little home brew, but it has been secure, never
loosening between my frequent checks. Putting the stoker handlebar loads
on the tow seatpost takes most of the twisting load off the tow bike's
axle and rear triangle. The bracing angle of the (spread) fork legs
makes most of the load in tension or compression, the additional
(static) axle load is modest, perhaps 40% of stoker's weight. The axle
overhang is minimal. The moment on the stoker stem and bar combo is
large, and that is some concern, but I have it mounted low. I've been
taking test rides slowly at first, checking frequently for problems. So
far, so good.

The tow bike is also my utility bike, so for now I'm taking it in and
out of tandem mode fairly frequently. The good news is that it's a 5
minute operation. I left the rear brake on the trailer bike hooked up to
the stoker's bars. We did some long steep descents where we used that
brake as a drag brake to control speed and I used the other 2 brakes in
the corners. Again, similar to a common tandem set up, but with the
actual braking (friction) and thermal load spread over 3 wheels. Another
advantage is having independent cranks. Since neither of us are
experienced tandem riders, that made the learning curve substantially
shorter. Perhaps the biggest feature is the cost. Being exceptionally
large myself, and us well over average for a team weight (close to 400
lb), a conventional tandem would be somewhat pricey, even by tandem
standards. So far I have perhaps $100 in this vehicle.

Some (Flicker) pictures:

http://tinyurl.com/3624ujzhttp://tinyurl.com/2w6xpsl

Hi there.

That setup sounds and looks interesting. It would be a great way to
take a weak rider on a longer ride and it has the added advantage of
storing compactly compared to a regular tandem. My only concern would
be the possibility of the trailer-bike jack-knifing if the captain hit
the brakes hard and the stoker didn't react fast enough.

That being said, I may just give such a conversion a try.

Thanks for the images and description.

Something I've been considering is mounting genuine ball mount onto
the rear triangle of a bicycle and then having a genuine trailer hitch
mounted to the upper section of a pair of forks that have had the fork
legs removed. The only issue I need to finishing working out is the
clearance of the trailer bike frame over the rear wheel.

Thanks and cheers from Peter

On Jul 27, 4:18*am, Sir Ridesalot wrote:
On Jul 26, 6:45*pm, Peter Cole wrote:





I became interested in articulated 3-wheel (inline) tandems ever since
the days when I pulled my daughter on an Adams trailer bike. We kept it
up until she hit the Adams recommended weight limit of 100 lb. Most of
our riding was off-road, actually on very "technical" single track
trails. I came to appreciate the advantages of 3 wheels over 2 on a
tandem, at least for off-road cycling.

Since that time I have given a lot of thought to an "adult" sized
trailer bike approach to a tandem. I started fooling around a couple of
years ago, finally coming up with an approach that was ridable, but I
wasn't too happy with it. This year I made a change which improved
things dramatically and resulted in a bike that rides very well.

The basic approach (which many have tried) is to use 2 bikes, spreading
the front fork of the "trailer" bike to fit over the axle of the front
(tow) bike's rear wheel. I took a beefy steel 26" fork and spread the
legs, then bent the dropouts to vertical. I fitted a long axle to the
rear hub of the "tow" bike. Originally I used a (hollow) tandem axle,
but switched to a solid piece of threaded high strength rod, mostly to
get some extra length.

Each fork leg is locked to the axle by 4 (greased) washers. The washers
are 1" diameter which form an interference fit in the lawyer lips, 2
washers on each side of the fork dropout, so 8 washers in all. I use
track nuts to load the washers, with a jam nut outboard to prevent
loosening. I just tighten the track nuts until there is resistance to
vertical articulation in the fork then lock the jams against them. The
net result is that a universal joint is formed, one axis of rotation
around the axle (pitch), the other (yaw) around the headset.

On my first iteration last year, I left the trailer bike's original stem
and handlebars on. The resulting performance bothered me. After a lot of
thought and experimentation I realized that the problem was that the
coupling wasn't torsionally rigid enough and the system acted like 2
masses coupled with a torsion spring. In other words, once it started
oscillating, it was difficult to damp out. I convinced myself that the
lack of rigidity wasn't in the fork of the trailer bike but rather in
the rear triangle of the tow bike. I thought of various ways to stiffen
things, but everything I came up with seemed complicated and I was ready
to abandon the idea. Close, but no cigar. We rode it, but I wasn't happy
with it.

Over the winter, I had an idea that seems obvious in retrospect. I moved
the "stoker's" handlebars from the trailer bike to the seatpost of the
tow bike. Of course that's the common arrangement for conventional
tandems, but I hadn't thought about it with a trailer bike. The obvious
problem of interference while articulating was solved by using "ape
hanger" bars, which, with a standard size, allowed me to locate the rear
hand positions exactly where they had been.

This new configuration made a night and day difference in handling.
Essentially, the body of the stoker becomes an element of the linkage.
Any force the stoker applies to the bars (pedaling reaction force, etc.)
couples directly and rigidly to the tow bike, as it would in a
conventional tandem. Any torsional oscillation that develops is quickly
and naturally damped out by the stoker's upper body. While the assembly
was always stable at high speeds, now it became stable at low speeds, too.

We've got around 200 miles on the prototype so far. We haven't ridden
any "real" off-road (singletrack) yet, but we have done unpaved trails,
urban riding in traffic and narrow bike paths, including some pretty
steep climbs. My stoker was comfortable enough to ride out of the saddle
right away, and the bike(s) is stable enough that I didn't really even
notice. She's now frequently riding no hands and swiveling for the
scenery, and I'm not getting the upper body workout I was with rev. 1,
still not riding no hands myself, but one handed comfortably. The bikes
I used were some clunkers (particularly the trailer), so the total is
somewhat heavier than a tandem, but not too bad, considering.

I've paid careful attention to handling characteristics. I have a lot of
experience with trailer and trailer bikes, particularly in extreme
conditions. I was somewhat concerned that having the 2 articulation axes
offset might introduce some odd motion couplings (e.g. going over a bump
while in a hard turn). There's a little bit of that, but not enough to
be an issue. All in all, it handles predictably -- braking, turning and
going over large bumps. I hope to log some miles on real trails this summer.

Safety has been my first concern, My stoker (wife) is used to some
experimental risk, but I'd feel really bad if I crashed her. The fork
coupling seems a little home brew, but it has been secure, never
loosening between my frequent checks. Putting the stoker handlebar loads
on the tow seatpost takes most of the twisting load off the tow bike's
axle and rear triangle. The bracing angle of the (spread) fork legs
makes most of the load in tension or compression, the additional
(static) axle load is modest, perhaps 40% of stoker's weight. The axle
overhang is minimal. The moment on the stoker stem and bar combo is
large, and that is some concern, but I have it mounted low. I've been
taking test rides slowly at first, checking frequently for problems. So
far, so good.

The tow bike is also my utility bike, so for now I'm taking it in and
out of tandem mode fairly frequently. The good news is that it's a 5
minute operation. I left the rear brake on the trailer bike hooked up to
the stoker's bars. We did some long steep descents where we used that
brake as a drag brake to control speed and I used the other 2 brakes in
the corners. Again, similar to a common tandem set up, but with the
actual braking (friction) and thermal load spread over 3 wheels. Another
advantage is having independent cranks. Since neither of us are
experienced tandem riders, that made the learning curve substantially
shorter. Perhaps the biggest feature is the cost. Being exceptionally
large myself, and us well over average for a team weight (close to 400
lb), a conventional tandem would be somewhat pricey, even by tandem
standards. So far I have perhaps $100 in this vehicle.

Some (Flicker) pictures:

http://tinyurl.com/3624ujzhttp://tinyurl.com/2w6xpsl

Hi there.

That setup sounds and looks interesting. It would be a great way to
take a weak rider on a longer ride and it has the added advantage of
storing compactly compared to a regular tandem. My only concern would
be the possibility of the trailer-bike jack-knifing if the captain hit
the brakes hard and the stoker didn't react fast enough.

That being said, I may just give such a conversion a try.

Thanks for the images and description.

Something I've been considering is mounting genuine ball mount onto
the rear triangle of a bicycle and then having a genuine trailer hitch
mounted to the upper section of a pair of forks that have had the fork
legs removed. The only issue I need to finishing working out is the
clearance of the trailer bike frame over the rear wheel.

Thanks and cheers from Peter

On the Continent a common trailer coupling fits on the rack. Tubus in
their Addit aluminium rack range makes a dedicated model for pulling a
trailer. I don't actually have one, but know about it because two
kinds of trailers and this rack are in the components programme of
Utopia, makers of my Kranich. But I tell you this merely for the
record.

I have substantial doubts about that rack-based coupling, or the rack,
surviving a season offroad with the large Coles or even their
presumably lighter kids on a homede tandem linked to it. My own
opinion is that, the moment Peter removed the torsional forces
directed through the handlebar from the axle of the middle wheel, his
kludge became a more attractive solution.

In addition to the hinging of the bike around the headset, I
especially like the way Peter's washer/loose tracknut/locknut assembly
gives juncture of the two "bikes" a degree of freedom. This is not
only a necessity to avoid pretzelled forks in cases of
misunderstandings between captain and stoker, and probably an irate
(or worse, hurt) wife after the inevitable crash, but is very
desirable for both the comfort and the security of the stoker, and of
course adds to the maneuverability of the bike over rough terrain
because too rigid a junction would be an auto-steering device.

Andre Jute
Get a bicycle. You will not regret it. If you live -- Mark Twain

Peter Cole wrote:

I became interested in articulated 3-wheel (inline) tandems ever since
the days when I pulled my daughter on an Adams trailer bike.

The basic approach (which many have tried) is to use 2 bikes, spreading
the front fork of the "trailer" bike to fit over the axle of the front
(tow) bike's rear wheel.

Some (Flicker) pictures:

http://tinyurl.com/3624ujz
http://tinyurl.com/2w6xpsl

Some years ago, when I met Portland's Zoo Bombers, I saw a clever
little mutant bike with three wheels and two cranks, which could be
ridden on any two or all three wheels and propelled with either
crank. It was one of a handful of bikes built from 12", 16", or 20"
wheeled kidbikes. Here is a picture of one:

http://everydayilive.com/slaughteram...erama3-052.jpg

What I have to say about that is... great minds think alike.

Chalo

Sir Ridesalot wrote:

Hi there.

That setup sounds and looks interesting. It would be a great way to
take a weak rider on a longer ride

Yes, that's the big advantage of both trailer bikes and tandems.
Tandemists often sing the praises of synchronized cranks, but I'm not
convinced. Independent crank tandems are available (Davinci) but
expensive. While lots of couples love tandem riding, I know several who
have tried it and didn't stick with it. I suspect synchronized cranks
and the issues they create may play a big part.

What I discovered from years of pulling a trailer bike was that I could
get a really good workout (as much as I wanted) pulling my daughter, and
she had the fun of going much faster than she could on her own. It took
all the frustration out of family rides.

and it has the added advantage of
storing compactly compared to a regular tandem.

Both storing and transporting on a regular bike rack.


My only concern would
be the possibility of the trailer-bike jack-knifing if the captain hit
the brakes hard and the stoker didn't react fast enough.

Jackknifing trailers is always a concern. I did a lot of riding on loose
surfaces and steep grades with the trailer bike and jackknifing wasn't a
particular problem, I learned to use the rear brake a little more. To
make up for that, trailer bikes are excellent "endo preventers". We
commonly descended steep ski trails (in the summer), and I found I could
go faster than solo.

With this design, because the stoker bars are attached to the tow bike
seatpost, much of the force decelerating the stoker follows that path.
It seems to be very resistant to jackknifing, although catching the
stoker off guard in a panic stop is still a concern.

That being said, I may just give such a conversion a try.

Thanks for the images and description.

Something I've been considering is mounting genuine ball mount onto
the rear triangle of a bicycle and then having a genuine trailer hitch
mounted to the upper section of a pair of forks that have had the fork
legs removed. The only issue I need to finishing working out is the
clearance of the trailer bike frame over the rear wheel.

I considered that, like the Burley Piccolo. The clearance is one issue,
which I guess you could solve by making a tongue extending from the
trailer bike head tube. It would also require a beefy frame to support
the ball, I'm not sure an available rack would be sufficient. Lastly,
you'd need a ball hitch, I'm not sure where you'd find one of
appropriate size.

If you look at a Piccolo, you see that the tongue has a big curve to
clear the tire when articulating (e.g. over a bump). To do something
similar with a conventional frame on the trailer bike I think you'd have
to increase the distance between the bikes, which is generally not a
good thing. Some pictures he
http://konstantin.shemyak.com/cycling/Tandem/ There's another design
shown there which mounts the joint at the end of the rack, looks a
little neater, but you've still got to keep the trailer bike back far
enough to clear the down tube generously.


The "spread fork" approach seems much simpler, keeps the bikes close
together without any constraint on articulation and doesn't require
unique components (I'm cheap and lazy, which are actually good
engineering attributes). With the fork approach, you can actually get
the bikes even closer by reversing the fork. I've tried that, and it has
no effect on handling. I don't know why I don't have the forks reversed
now, just looks strange, I guess -- hardly an issue with a set up like this.

As I said in my initial post, the real innovation in my design I think
is combining the trailer bike approach with the tandem style stoker bar
arrangement. This makes a huge difference in the handling and stability.
To make that work, you can't have too great a distance between captain
and stoker and you have to solve the articulation interference problem.
Conventional tandems often have cramped stoker cockpits to keep the
wheelbase length down. A 3-wheeler allows you to open that up some, but
the longer you go and the further back you couple the more you're asking
for jackknife and wobble problems.

For those who are reluctant (perhaps wisely) to spread a fork that much,
Surly makes a fork ("Pugsley") with 135 mm spacing ($70-90 here). I got
my threaded rod at McMaster-Carr online (~$20), but tandem axles may
work -- might be even better with QR's. I found 1" washers fit exactly
in the dropout lawyer lips, I'm not sure if all LL are the same
diameter. I used brass washers (0.125" thick, 3/8" hole). To make the
stoker bars, I used a conventional MTB (0 rise) stem, but flipped it so
the bars mount in the steer post clamp and the bar clamp goes over the
(tow) seat post. I did this because my seatpost is oversize (30.8). The
bars are cheap steel "ape hangers" shimmed in the clamp.

The problem of coupling 2 bikes is that you want freedom to articulate
in pitch and yaw, but stiffness in roll, so that the bikes lean in a
turn together. Since you've already got a yaw bearing in the headset, it
only remains to provide for pitch. I don't know of a more compact way
than using a fork, and I think compactness is important. The ball pivot
may work well enough, but it seems like a lot more work and I'm not sure
the end result would be superior in performance. In any case, I'd be
interested in hearing about any hacking you do in that direction.

Chalo wrote:
Peter Cole wrote:
I became interested in articulated 3-wheel (inline) tandems ever since
the days when I pulled my daughter on an Adams trailer bike.

The basic approach (which many have tried) is to use 2 bikes, spreading
the front fork of the "trailer" bike to fit over the axle of the front
(tow) bike's rear wheel.

Some (Flicker) pictures:

http://tinyurl.com/3624ujz
http://tinyurl.com/2w6xpsl

Some years ago, when I met Portland's Zoo Bombers, I saw a clever
little mutant bike with three wheels and two cranks, which could be
ridden on any two or all three wheels and propelled with either
crank. It was one of a handful of bikes built from 12", 16", or 20"
wheeled kidbikes. Here is a picture of one:

http://everydayilive.com/slaughteram...erama3-052.jpg

What I have to say about that is... great minds think alike.

Chalo

Nice bike, but I wouldn't ride it without a fez.

On Jul 27, 7:26*am, Jobst Brandt wrote:
Chalo Colina wrote:
I became interested in articulated 3-wheel (in-line) tandems ever
since the days when I pulled my daughter on an Adams trailer bike.
The basic approach (which many have tried) is to use 2 bikes,
spreading the front fork of the "trailer" bike to fit over the axle
of the front (tow) bike's rear wheel.
Some (Flicker) pictures:

*http://tinyurl.com/3624ujz
*http://tinyurl.com/2w6xpsl

Some years ago, when I met Portland's Zoo Bombers, I saw a clever
little mutant bike with three wheels and two cranks, which could be
ridden on any two or all three wheels and propelled with either
crank. *It was one of a handful of bikes built from 12", 16", or 20"
wheeled kidbikes. *Here is a picture of one:

*http://everydayilive.com/slaughteram...erama3-052.jpg

What I have to say about that is... great minds think alike.

What I am missing in this thread, is why this design is preferred to a
conventional two wheeled tandem bicycle, something that has been used
by many riders, locally and on long tours. *

As a coincidence, I recently designed a BB that can independently
measure power of each rider on a tandem or for single bicycles for
recreation or competition, the mechanism being identical but separate
for each rider. *It measures torque generated by right and left pedal
strokes, including pulling on upward strokes.

This ability has interested me for a long time, because tandem riders
should know how hard the other rider is working on a ride. *Of course,
in races, team managers would like to look at the power record.

Measuring and critiquing power out-put by the stoker is one of the
leading causes of divorce in America. -- Jay Beattie.

On Jul 27, 8:26*am, Jobst Brandt wrote:
As a coincidence, I recently designed a BB that can independently
measure power of each rider on a tandem or for single bicycles for
recreation or competition, the mechanism being identical but separate
for each rider. *It measures torque generated by right and left pedal
strokes, including pulling on upward strokes.

New power meter? Details?

Jobst Brandt wrote:

:Your meaning is unclear. Do you believe having a display of relative
ower input on tandems is a good or bad feature?

For people racing them, it's a good thing. For everyone else, it'll
be a source of friction. (No doubt it will be a source of friction
between racers, but it's stull useful data.)

--
sig 102

Jobst Brandt wrote:
Chalo Colina wrote:

I became interested in articulated 3-wheel (in-line) tandems ever
since the days when I pulled my daughter on an Adams trailer bike.

The basic approach (which many have tried) is to use 2 bikes,
spreading the front fork of the "trailer" bike to fit over the axle
of the front (tow) bike's rear wheel.

Some (Flicker) pictures:

http://tinyurl.com/3624ujz
http://tinyurl.com/2w6xpsl

Some years ago, when I met Portland's Zoo Bombers, I saw a clever
little mutant bike with three wheels and two cranks, which could be
ridden on any two or all three wheels and propelled with either
crank. It was one of a handful of bikes built from 12", 16", or 20"
wheeled kidbikes. Here is a picture of one:

http://everydayilive.com/slaughteram...erama3-052.jpg

What I have to say about that is... great minds think alike.

What I am missing in this thread, is why this design is preferred to a
conventional two wheeled tandem bicycle, something that has been used
by many riders, locally and on long tours.

To start with, I'd say that there doesn't need to be a specific reason
to experiment with bikes. Reading over the patents, there have been
several over the last 100 years for this kind of arrangement. I found it
an interesting problem, practical or not.

There has been a good market for children's trailer bikes. These are
much cheaper than conventional tandems and require no modifications as
they're kid-sized to begin with. They also disassemble quickly for
storage and transport. The one I bought was perhaps the best investment
I made for family cycling.

I used a trailer bike with my child for several years, mostly on
off-road trails. That type of terrain presents unique problems for
tandems. Synchronized cranks and long "keel tubes" can make riding over
very uneven terrain (e.g. logs) difficult. Despite its overall longer
wheelbase, I found that a trailer bike could track narrow twisting
trails well because of its articulation. Two driving and 3 braking
wheels helped in low traction situations (sand, gravel, leaf litter). I
became interested in an "adult-sized" trailer bike for off-road riding
just out of curiosity.

The main reason I didn't just go buy a new or used conventional tandem
(road or off-road) was primarily that I have unique requirements. My
wife is average sized (5'7"), but I'm not (6'10"). After some
exploration, I realized that finding a tandem that would fit us was
either going to be impossible or very expensive. I had the idea that
making a 3-wheeled tandem from odd and ends might be a whole lot cheaper
and better fitting.

Now that I have a prototype of this design made, I've been interested in
seeing how well it performs, especially relative to a conventional
tandem. This is somewhat complicated by the issue that I have no real
experience with a conventional tandem. I am not touting this as a
universal tandem replacement, but only posting the results of my
experiments in case others have an interest, for whatever reason. I have
discussed comparative characteristics with experienced tandem riders.
Some have found the approach interesting.

I don't really think there are any compelling advantages for this design
over a conventional tandem for touring or normal road riding, I don't
think there are any significant disadvantages, either. Perhaps the
biggest difference is independent vs. synchronized cranks. That's either
a bug or a feature depending on your outlook. What I have discovered,
that I didn't know initially, was that the low and high speed handling
characteristics are very good. It may be slightly heavier and have
slightly inferior aerodynamics, but being made from standard components,
it's much cheaper and storage and transport are easier. For off-road
riding I think the ability to articulate in pitch and yaw may make it
superior in some terrain. I plan to take some test rides to explore this
now that we have some miles under our belts under less challenging
conditions.


As a coincidence, I recently designed a BB that can independently
measure power of each rider on a tandem or for single bicycles for
recreation or competition, the mechanism being identical but separate
for each rider. It measures torque generated by right and left pedal
strokes, including pulling on upward strokes.

This ability has interested me for a long time, because tandem riders
should know how hard the other rider is working on a ride. Of course,
in races, team managers would like to look at the power record.

For competitive tandemists, sure. Real time power monitoring is the next
big thing, I guess. For recreational riding with your spouse I'm not so
sure. I don't particularly care how hard my wife is pedaling. I just
pedal as hard as I want to and assume she's doing the same. We get there
when we get there. With independent cranks, we can pick our preferred
cadence, coast or stand without a coordinated effort. Starts and stops
become a lot less complicated.

Another great feature of an "occasional" tandem that I hadn't
appreciated was the ability to ride it solo and go pick up my stoker. I
surprised my wife one day by meeting her at the train station -- she got
a huge kick out of that. I suppose I could sling bags over the top tube
and use it for a cargo trailer, too.