Monotubes vs Triangulation

Alan Mushnick said:

Isn't there an inherent structural advantage of triangulated frames
over monotubes? This seemed to be a big part of the discussion of the
Easy Racer vs. Rans V2 debate.

Both the Easy Racers Tour Easy/Gold Rush Replica/TiRush and the RANS
Velocity Squared/Formula have triangulated frames.

RANS Force 5 versus the Bacchetta Strada and Corsa would be a more apt
comparison.

I do not know what a "Rans" is, so I can not comment on it.

--
Tom Sherman – Quad Cities (Illinois Side)

Tom,
"Rans"
is the company that denies the seat problems ,once this is resolved it will
again become "RANS" 🙂
Ben fox

"Tom Sherman" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

Alan Mushnick said:

Isn't there an inherent structural advantage of triangulated frames
over monotubes? This seemed to be a big part of the discussion of the
Easy Racer vs. Rans V2 debate.

Both the Easy Racers Tour Easy/Gold Rush Replica/TiRush and the RANS
Velocity Squared/Formula have triangulated frames.

RANS Force 5 versus the Bacchetta Strada and Corsa would be a more apt
comparison.

I do not know what a "Rans" is, so I can not comment on it.

--
Tom Sherman – Quad Cities (Illinois Side)

Ben Fox said:

Tom, "Rans" is the company that denies the seat problems ,once this is
resolved it will again become "RANS" 🙂 Ben fox
"Tom Sherman" <[email hidden]> wrote in message news:[email hidden]:c5kort$2ttms$1@ID-
81487.news.uni- berlin.de...

Quoted message said:

Alan Mushnick said:

Isn't there an inherent structural advantage of triangulated frames
over monotubes? This seemed to be a big part of the discussion of
the Easy Racer vs. Rans V2 debate.

Both the Easy Racers Tour Easy/Gold Rush Replica/TiRush and the RANS
Velocity Squared/Formula have triangulated frames.

RANS Force 5 versus the Bacchetta Strada and Corsa would be a more apt
comparison.

I do not know what a "Rans" is, so I can not comment on
it.

--
Tom Sherman – Quad Cities (Illinois Side)

The links of a triangulated frame form a structure known as a truss. As
a triangle is unusual in that it has a unique shape and set of angles
for given set of side lengths, it is very stable and rigid when used as
a structure *ever notice the trusses in bridges). It can provide a rigid
frame avoiding power-robbing frame flex and avoid the squirrelly
handling of too much frame flex. For a light metal prone to failure if
flexed such as aluminum, this structure is generally the preferred bent
approach. Carbon fiber frames also needs some frame rigidity built into
the design to avoid failure so a truss can supply this as well.

A monotube is lighter weight since only a single tube is involved and it
is more flexible giving a built in suspension. But it lacks the support
available from a triangulated truss. For a strong heavy flexible metal
such as chromoly steel this is often the best bent frame structure since
it saves weight and lets the steel flex.

A lightweight flexible metal such as titanium can work as a monotube but
with its already light weight it doesn’t significantly save a lot of
weight over triangulated frames so it fails to avail itself of the chief
benefit of monotubes. Neither approach has such a huge advantage over
the other for Ti bents so as to overwhelmingly predominate.

--

"Alan Mushnick" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

Isn't there an inherent structural advantage of triangulated frames
over monotubes?

I think there is typically a weight penalty to make the monotube as strong
and stiff as a triangulated or "space" frame. The Lightning P 38 and
Phantom would be a good example of this. My guess is that the Phantom
monotube frame is about 10% to 15% heavier than the
P 38 frame with the same geometry and size.

skip

Tom Sherman said:

I do not know what a "Rans" is, so I can not comment on it

Bald-headed guy in cartoon series. Flies on dinosaurs, I think.
Something like that.

Curtis L. Russell
Odenton, MD (USA)
Just someone on two wheels...

All the comments so far have been dead on. It's best to think of this
in terms of compromise. Triangulation gives you the best stiffness and
strength for the amount of material that you use. You can flip that
around and use more material to make a monotube frame every bit as
stiff and strong, but it will weigh a lot more. (The old "if black
boxes always survive the airplane crash, then why aren't airplanes
built like black boxes?" thing.)

This is why the Catrike frames are triangulated...it lets us build a
much lighter frame without sacrificing strength or stiffness. Frames
that are not triangulated must by definition be heavier in order to
carry the required loads and not be too flexible. This is the biggest
reason why non-triangulated trikes weigh so much more.

Note that tubing shape and size also come into play. The greater the
diameter of the tube, the stiffer it is. Look at the the fat-tube
Cannondale DFs... the fat tubes are necessary because aluminum is not
as inherently stiff as steel, so you need to compensate by using
fatter, somewhat heavier tubes...more compromise. Bacchetta's
egg-shaped tube is stiffer in the vertical direction than it is
laterally. This lets them get the stiffness of a much larger tube in
the direction where the most loading is, without using the larger
tube. So, a little bit of weight is saved.

Box sections are stiffer than round tubes when it comes to bending,
but not as resistant to torsional (twisting) forces. This is why
George Reynolds gave the early Wishbones a box shape. I had a Wishbone
Classic and it was incredibly stiff. (He made it out of folded sheet
CrMo, not heavy drawn tubing...so it was also quite light.)

Note also that a typical triangulated bike frame like the Easy Racers
is triangulated in only one plane (the vertical one). Laterally, it's
just a collection of tubes laid down next to one another. It will be
enormously stiff and strong in that vertical plane, but not nearly as
stiff or strong in the lateral direction. I'd bet that the V2 frame is
actually stiffer and stronger laterally than the Easy Racers frame,
because the main tube is larger (therefore stiffer in all directions)
and the brace tubes are offset from the centerline, which gives it
triangulation in three dimensions.

Andy Douglas
Catrike

Andrew Douglas said:

Note also that a typical triangulated bike frame like the Easy Racers
is triangulated in only one plane (the vertical one).

Not quite. The lower tube on the Tour Easy and Gold Rush bikes is
actually two tubes side by side, about 1cm apart, all the way from the
bottom bracket to the rear wheel. That makes it very stiff laterally.

TY for pointing that out so I didn't have to 🙂

Gabe

"Joao de Souza" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

Andrew Douglas said:

Note also that a typical triangulated bike frame like the Easy Racers
is triangulated in only one plane (the vertical one).

Not quite. The lower tube on the Tour Easy and Gold Rush bikes is
actually two tubes side by side, about 1cm apart, all the way from the
bottom bracket to the rear wheel. That makes it very stiff laterally.

[email hidden] (Andrew Douglas) wrote in message news:<[email hidden]>...

Quoted message said:

All the comments so far have been dead on. It's best to think of this
in terms of compromise. Triangulation gives you the best stiffness and
strength for the amount of material that you use. You can flip that
around and use more material to make a monotube frame every bit as
stiff and strong, but it will weigh a lot more. (The old "if black
boxes always survive the airplane crash, then why aren't airplanes
built like black boxes?" thing.)

This is why the Catrike frames are triangulated...it lets us build a
much lighter frame

Are you really serious here? A trike as a speed bike compared to a
bike like the Bacchetta Aero?
My Aero is 22 lbs. Pretty light for a 'bent.
And The flex thing is not a big deal for a person who can spin.
I weigh in at 155 lbs and am probably not the typical recumbent rider.
I find that the Aero Monotube design is both simple and stiff enough
and a great bike for all day rides.
Lets see RANS sponsor some riders like Bacchetta does and let them
come to places like Monkey Island or some of the other race venues!
More 'bent [censored] and it never seems to end.
Come on Randy Schlitter sponsor some fast riders or shut the [censored] up!
And, Trikes are a joke as far as speed machines go and I know the fat
old guys will jump on this one!
Don't get me wrong trikes are cool and I like some of the neat designs
out there but don't go telling people that they are the cutting edge
in bent speed design.
The fastest unfaired bikes only have two wheels. Sorry to burst the
FOG's bubble.

"Gabriel DeVault" <[email hidden]> wrote in message news:<[email hidden]>...

Quoted message said:

TY for pointing that out so I didn't have to 🙂

Sorry about that...I remembered that fact right after I hit the "post"
button.

Just to clarify, I didn't mean to imply that the TE frame (or any
other conventional safety bicycle-type frame) is weak laterally...far
from it. Only that plane trusses are very stiff and strong in the
direction in which they're triangulated, but less so at right angles
to that plane. Even with the pair of side-by-side lower tubes, the TE
frame is going to be stiffer and stronger in one plane than it is in
the other. To make a bicycle frame as stiff and strong laterally as it
is vertically, you'd have to build a space frame as wide as it is
tall.

The basic design of the diamond-frame bicycle (which the TE is an
extension of) has proven itself to be very robust over many, many
years. It's a really elegant way of solving the design problem...much
more efficient in terms of use of materials than a plain monotube. So
relative differences in strength and stiffness in one plane vs. the
other are really academic: the thing is plenty strong enough.

The TE's side-by-side lower tubes are (please correct me if I'm
wrong...I don't own one) literally side-by-side and not separated,
which if I understand the forces involved would make them behave
approximately like a single oval tube of similar dimension to the two
together...stiffer in the direction of the major axis than it is in
the direction of the minor axis.

I believe (not entirely sure about this) that the overall dimensions
of the truss directly impact its stiffness and strength. So, for
example, a wide truss (TE frame) will be stronger and stiffer in the
vertical dimension than a narrow truss (V2 frame) if all else is equal
(similar tube sizes and materials). RANS uses a fat main tube, so that
changes things, making the narrow truss stronger and stiffer (and
heavier) than it would otherwise be. The V2's lower tubes are
separated and braced, which adds to the lateral stiffness.

Of course, I may be completely out of my skull. Wouldn't be the first
time. ;-)

Please feel free to correct me if I'm wrong.

Andy Douglas
Catrike

"meb" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

A monotube is lighter weight since only a single tube is involved and it
is more flexible giving a built in suspension. But it lacks the support
available from a triangulated truss. For a strong heavy flexible metal
such as chromoly steel this is often the best bent frame structure since
it saves weight and lets the steel flex.

The triangulated Rans Force5 frame is noticeably lighter than the steel
monotube hiracer frames on the market.

"nogoslow" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

Are you really serious here? A trike as a speed bike compared to a
bike like the Bacchetta Aero?
My Aero is 22 lbs. Pretty light for a 'bent.
And The flex thing is not a big deal for a person who can spin.
I weigh in at 155 lbs and am probably not the typical recumbent rider.
I find that the Aero Monotube design is both simple and stiff enough
and a great bike for all day rides.
Lets see RANS sponsor some riders like Bacchetta does and let them
come to places like Monkey Island or some of the other race venues!
More 'bent [censored] and it never seems to end.
Come on Randy Schlitter sponsor some fast riders or shut the [censored] up!

Randy designed a triangulated steel hiracer frame that is much lighter than
the Strada/Corsa frame.

I don't get your insistence on "sponsoring riders". We can all ride and
compare bents at our nearest dealers.

Alan Mushnick wrote;

Quoted message said:

Isn't there an inherent structural advantage of triangulated frames
over monotubes? This seemed to be a big part of the discussion of the
Easy Racer vs. Rans V2 debate.

Hi Alan

Designers make choices all the time about how to balance the sometimes
conflicting goals of weight, stiffness, aerodynamics etc. of frames.

Many times frame geometry and material, or the style of bike (or trike) and
wheelbase make the designers choices easy.

Two entirely different stiffness issues are involved here, those against
pedaling forces (fairly important IMO) and vertical stiffness. I have ridden
truss frames out there that are very vertically stiff, but have
wagging/twisting bottom brackets from a lack of horizontal stiffness. Pedaling
forces act on frames in both the horizontal and vertical plane.

Vertical stiffness is not always a good thing on bicycles, you have to
consider that you have a human engine on board, and bumpy roads to contend
with. If a frames stiffness against pedaling forces also makes the frame a
jackhammer vertically, you only have the tires and the seat cushioning to act
as springs between you and the road.

Also, making a frame lighter by triangulation can make a bike slower by
increasing the frontal area of tubes under the rider, and also by requiring
lower pressure (generally wider, heavier, lower performance) tires for
equivalent rider comfort. A bikes frontal area and the tires rolling
resistance are the two dominant factors in efficiency on most courses.

Weight undoubtedly sells bikes- but improved aerodynamics and lower
rolling resistance makes them more efficient on the road.

As far as triangulation always yielding lighter frames... the bare
titanium Bacchetta Aero frame weighs 3.5 lbs and has what I feel are the ideal
tradeoffs of weight, low frame frontal area under the rider, and some passive
suspension vertically...but still stiff enough against pedaling forces for high
transmission efficiency.

Our steel frames weigh about 3 lbs more and are stiffer vertically, but
still have a good amount of passive suspension to augment the tires and seat
cushioning's road shock absorbtion...VERY important to our bikes performance!

That's what is great about the world of recumbents today, everyone can
make a different choice about what is most important to them, and choose bikes
with greatly different characteristics and abilities!

Rich Pinto
Bacchetta Bicycles

Andrew Douglas said:

The TE's side-by-side lower tubes are (please correct me if I'm
wrong...I don't own one) literally side-by-side and not separated,

I'm not 100% sure about the TE, but on the GRR they are separated. Its
two tubes, about 1cm in diameter each and with a 1cm gap between them.
They are joined at the bottom bracket, and have a few supporting beams
welded to it along the way.

Great post Rich,
You always do a great job of explaining your position. Obviously you prefer
Bacchetta bikes but you state that in such a way you don't trash your
competitors.

"RCPINTO" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

Alan Mushnick wrote;

Quoted message said:

Isn't there an inherent structural advantage of triangulated frames
over monotubes? This seemed to be a big part of the discussion of the
Easy Racer vs. Rans V2 debate.

Hi Alan

Designers make choices all the time about how to balance the sometimes
conflicting goals of weight, stiffness, aerodynamics etc. of frames.

Many times frame geometry and material, or the style of bike (or

trike) and

Quoted message said:

wheelbase make the designers choices easy.

Two entirely different stiffness issues are involved here, those

against

Quoted message said:

pedaling forces (fairly important IMO) and vertical stiffness. I have

ridden

Quoted message said:

truss frames out there that are very vertically stiff, but have
wagging/twisting bottom brackets from a lack of horizontal stiffness.

Pedaling

Quoted message said:

forces act on frames in both the horizontal and vertical plane.

Vertical stiffness is not always a good thing on bicycles, you have

to

Quoted message said:

consider that you have a human engine on board, and bumpy roads to contend
with. If a frames stiffness against pedaling forces also makes the frame

a

Quoted message said:

jackhammer vertically, you only have the tires and the seat cushioning to

act

Quoted message said:

as springs between you and the road.

Also, making a frame lighter by triangulation can make a bike slower

by

Quoted message said:

increasing the frontal area of tubes under the rider, and also by

requiring

Quoted message said:

lower pressure (generally wider, heavier, lower performance) tires for
equivalent rider comfort. A bikes frontal area and the tires rolling
resistance are the two dominant factors in efficiency on most courses.

Weight undoubtedly sells bikes- but improved aerodynamics and lower
rolling resistance makes them more efficient on the road.

As far as triangulation always yielding lighter frames... the bare
titanium Bacchetta Aero frame weighs 3.5 lbs and has what I feel are the

ideal

Quoted message said:

tradeoffs of weight, low frame frontal area under the rider, and some

passive

Quoted message said:

suspension vertically...but still stiff enough against pedaling forces for

high

Quoted message said:

transmission efficiency.

Our steel frames weigh about 3 lbs more and are stiffer vertically,

but

Quoted message said:

still have a good amount of passive suspension to augment the tires and

seat

Quoted message said:

cushioning's road shock absorbtion...VERY important to our bikes

performance!

Quoted message said:

That's what is great about the world of recumbents today, everyone

can

Quoted message said:

make a different choice about what is most important to them, and choose

bikes

Quoted message said:

with greatly different characteristics and abilities!

Rich Pinto
Bacchetta Bicycles

Ted said:

Great post Rich,
You always do a great job of explaining your position. Obviously you prefer
Bacchetta bikes but you state that in such a way you don't trash your
competitors.

I agree. A clear explanation of what he perceives to be the best
choice among several alternatives, and all without coming across as
simply biased and against the designs of the other bikes. The
combination results in a great deal of credibility, not to mention
cravings for the bikes in question!
--
Larry Varney
Cold Spring, KY
http://home.fuse.net/larryvarney

(nogoslow) said:

Are you really serious here? A trike as a speed bike compared to a
bike like the Bacchetta Aero?
...
Don't get me wrong trikes are cool and I like some of the neat designs
out there but don't go telling people that they are the cutting edge
in bent speed design.

Huh? I neither said nor implied any such thing!!! Did you even read
the post? I didn't say the Catrikes are "cutting edge in bent speed
design," nor did I compare its speed with any bicycle. For that matter
I said nothing about the speed of anything. Just where did you get
that idea?

All I said was that trangulated structures are stiffer and stronger
for the amount of material used than monotube structures. That goes
for bridges and buildings and radio towers and the Eiffel Tower as
well as bicycles. Regarding the Catrike reference, ALL I said was that
we can use lighter/less material to get the required degree of
stiffness and strength because it's triangulated. If we built a
non-braced frame, we'd have to build it heavier to get the same
properties. That doesn't mean we couldn't make it just as strong and
just as stiff...we'd just have to trade weight in order to do that.
The same goes for any other manufacturer of any design. We're not
special.

I also said NOTHING WHATSOEVER about monotube structures not being
strong enough. Of course they are strong enough if designed properly!

But if you take the same mass of titanium that's in your Aero and
build a triangulated truss out of it, it will be stiffer and stronger
than the monotube is. That's NOT THE SAME THING as saying that the
Aero isn't stiff enough and strong enough to begin with. It also does
not mean that a triangulated structure will necessarily achieve the
intended design goals. As Rich pointed out, when you start hanging all
those tubes out in the breeze you have other things to think about
(aerodynamics, etc.).

Triangulation is simply another way of solving the design question.
It's not inherently "better" or "worse." It's DIFFERENT. It's a design
tool, nothing more.

I'll gladly retract any incorrect statements I make, but geez, PLEASE
don't go putting words in my mouth!

Andy Douglas
Catrike

TimH said:

The triangulated Rans Force5 frame is noticeably lighter than the steel
monotube hiracer frames on the market.

You must have some data to support this. So what are the frame weights ?

Timh said:

The triangulated Rans Force5 frame is noticeably lighter than the steel
monotube hiracer frames on the market.

Volae Sport 27.5 vs. Force 5 LE 28.0-28.4 Volae Club 26 (No intermediate
Force 5 model) Volae Team 24 vs. Force 5 XP 25.6-25.9

Are you suggesting the Volae models save weight with much lighter
componetry?

--