Go Back   DIY Go Kart Forum > Building Plans And Advice > Go Kart Discussion

Notices

Reply
 
Thread Tools Display Modes
  #1  
Old 03-24-2018, 02:37 PM
Functional Artist's Avatar
Functional Artist Functional Artist is offline
Senior Member
 
Join Date: Jul 2016
Location: Toledo, Ohio
Posts: 1,997
Thanks: 767
Thanked 753 Times in 598 Posts
Default Torsk (Backbone Chassis) Kart

Doin research, looking for something interesting & different

Looking thru old threads for ideas, I came across this kool idea
"Hotwinged" that 'sid was workin' on back in 2014
http://www.diygokarts.com/vb/showthread.php?t=25361
...wonder what ever became of it?

I also came across this neat concept (a backbone chassis)
Frederic's Backbone kart from way back in 2009
http://www.diygokarts.com/vb/showthread.php?t=4634
...wonder what ever become of it?


Here is some info on chassis design/construction

http://autozine.org/technical_school...ch_chassis.htm

Ladder Chassis
This is the earliest kind of chassis. From the earliest cars until the early 60s, nearly all cars in the world used it as standard. Even in today, most SUVs still employ it. Its construction, indicated by its name, looks like a ladder - two longitudinal rails interconnected by several lateral and cross braces. The longitude members are the main stress member. They deal with the load and also the longitudinal forces caused by acceleration and braking. The lateral and cross members provide resistance to lateral forces and further increase torsional rigidity.

Tubular Space Frame
As ladder chassis is not strong enough, motor racing engineers developed a 3 dimensional design - Tubular space frame. One of the earliest examples was the post-war Maserati Tipo 61 "Birdcage" racing car. Tubular space frame chassis employs dozens of circular-section tubes (some may use square-section tubes for easier connection to the body panels, though circular section provides the maximum strength), position in different directions to provide mechanical strength against forces from anywhere. These tubes are welded together and forms a very complex structure, as you can see in the above pictures. For higher strength required by high performance sports cars, tubular space frame chassis usually incorporate a strong structure under both doors (see the picture of Lamborghini Countach), hence result in unusually high door sill and difficult access to the cabin. In the early 50s, Mercedes-Benz created a racing car 300SLR using tubular space frame. This also brought the world the first tubular space frame road car, 300SL Gullwing. Since the sill dramatically reduced the accessibility of carbin, Mercedes had to extend the doors to the roof so that created the "Gullwings".
Since the mid 60s, many high-end sports cars also adopted tubular space frame to enhance the rigidity / weight ratio. However, many of them actually used space frames for the front and rear structure and made the cabin out of monocoque to cut cost.

Monocoque
Today, 99% cars produced in this planet are made of steel monocoque chassis, thanks to its low production cost and suitability to robotised production.
Monocoque is a one-piece structure which defines the overall shape of the car. While ladder, tubular space frame and backbone chassis provides only the stress members and need to build the body around them, monocoque chassis is already incoporated with the body in a single piece, as you can see in the above picture showing a Volvo V70.

In fact, the "one-piece" chassis is actually made by welding several pieces together. The floorpan, which is the largest piece, and other pieces are press-made by big stamping machines. They are spot welded together by robot arms (some even use laser welding) in a stream production line. The whole process just takes minutes. After that, some accessories like doors, bonnet, boot lid, side panels and roof are added.

Monocoque chassis also benefit crash protection. Because it uses a lot of metal, crumple zone can be built into the structure.

Another advantage is space efficiency. The whole structure is actually an outer shell, unlike other kinds of chassis, therefore there is no large transmission tunnel, high door sills, large roll over bar etc. Obviously, this is very attractive to mass production cars.

There are many disadvantages as well. It's very heavy, thanks to the amount of metal used. As the shell is shaped to benefit space efficiency rather than strength, and the pressed sheet metal is not as strong as metal tubes or extruded metal, the rigidity-to-weight ratio is also the lowest among all kinds of chassis bar the ancient ladder chassis. Moreover, as the whole monocoque is made of steel, unlike some other chassis which combine steel chassis and a body made of aluminium or glass-fiber, monocoque is hopelessly heavier than others.

Although monocoque is suitable for mass production by robots, it is nearly impossible for small-scale production. The setup cost for the tooling is too expensive - big stamping machines and expensive mouldings. I believe Porsche is the only sports car specialist has the production volume to afford that.

ULSAB Monocoque
Enter the 90s, as tougher safety regulations ask for more rigid chassis, traditional steel monocoque becomes heavier than ever. As a result, car makers turned to alternative materials to replace steel, most notable is aluminium. Although there is still no mass production car other than Audi A8 and A2 to completely eliminate steel in chassis construction, more and more cars use aluminium in body panels like bonnet and boot lid, suspension arms and mounting sub-frames. Unquestionably, this is not what the steel industry willing to see.
Therefore, American's steel manufacturers hired Porsche Engineering Services to develop a new kind of steel monocoque technology calls Ultra Light Steel Auto Body (ULSAB). As shown in the picture, basically it has the same structure as a conventional monocoque. What it differs from its donor is in minor details - the use of "Hydroform" parts, sandwich steel and laser beam welding.

Hydroform is a new technique for shaping metal to desired shape, alternative to pressing. Conventional pressing use a heavy-weight machine to press a sheet metal into a die, this inevitably creates inhomogenous thickness - the edges and corners are always thinner than surfaces. To maintain a minimum thickness there for the benefit of stiffness, car designers have to choose thicker sheet metal than originally needed. Hydroform technique is very different. Instead of using sheet metal, it forms thin steel tubes. The steel tube is placed in a die which defines the desired shape, then fluid of very high pressure will be pumped into the tube and then expands the latter to the inner surface of the die. Since the pressure of fluid is uniformal, thickness of the steel made is also uniformal. As a result, designers can use the minimum thickness steel to reduce weight.

Sandwich steel is made from a thermoplastic (polypropylene) core in between two very thin steel skins. This combination is up to 50 percent lighter compared with a piece of homogenous steel without a penalty in performance. Because it shows excellent rigidity, it is applied in areas that call for high bending stiffness. However, it cannot be used in everywhere because it needs adhesive bonding or riveting instead of welding.

Compare with conventional monocoque, Porsche Engineering claimed it is 36% lighter yet over 50% stiffer. Although ULSAB was just annouced in early 1998, the new Opel Astra and BMW 3-Series have already used it in some parts. I believe it will eventually replace conventional monocoque.

Backbone Chassis
Colin Chapman, the founder of Lotus, invented backbone chassis in his original Elan roadster. After failed in his experiment of glass-fibre monocoque, Chapman discovered a strong yet cheap chassis which had been existing for millions of years - backbone.

Backbone chassis is very simple: a strong tubular backbone (usually in rectangular section) connects the front and rear axle and provides nearly all the mechnical strength. Inside which there is space for the drive shaft in case of front-engine, rear-wheel drive layout like the Elan. The whole drivetrain, engine and suspensions are connected to both ends of the backbone. The body is built on the backbone, usually made of glass-fibre.

It's strong enough for smaller sports cars but not up to the job for high-end ones. In fact, the original De Tomaso Mangusta employed chassis supplied by Lotus and experienced chassis flex.

TVR's chassis is adapted from this design - instead of a rigid backbone, it uses a lattice backbone made of tubular space frames. That's lighter and stronger (mainly because the transmission tunnel is wider and higher).

http://articles.sae.org/9522/

Well, this gets the wheels a turnin'
Let me see what I can come up with

Ima gonna call 'er the Torsk, just cause it sounds kool
...seen a documentary on the U.S.S. Torsk a couple of weeks ago (a bad azz piece of machinery)
Attached Thumbnails
De_Tomaso_P70_chassis_at_Turin_Motor_Show_in_November_1965.jpg   Lotus_Elan_car_chassis.jpg  

Backbone Uni-chassis.jpg  
__________________
RESISTANCE IS FUTILE
Reply With Quote
  #2  
Old 03-26-2018, 06:56 PM
jandj's Avatar
jandj jandj is offline
Senior Member
 
Join Date: Nov 2009
Location: Williamsburg, Va
Posts: 1,158
Thanks: 34
Thanked 452 Times in 315 Posts
Default

Reply With Quote
  #3  
Old 03-26-2018, 08:12 PM
Functional Artist's Avatar
Functional Artist Functional Artist is offline
Senior Member
 
Join Date: Jul 2016
Location: Toledo, Ohio
Posts: 1,997
Thanks: 767
Thanked 753 Times in 598 Posts
Default

Quote:
Originally Posted by jandj View Post
Very Kool!

Check this one out
Attached Thumbnails
side engine chassis.jpg  
__________________
RESISTANCE IS FUTILE
Reply With Quote
  #4  
Old 03-26-2018, 09:00 PM
anickode's Avatar
anickode anickode is offline
Senior Member
 
Join Date: Apr 2010
Location: S.E. Michigan
Posts: 1,796
Thanks: 59
Thanked 800 Times in 555 Posts
Default

Those old Diesel boats are really something to see. The Tench class were really slightly upfitted versions of the later Balao class boats.

I got to tour the USS Pampanito in San Fran several years ago. Even after 75 years, it still smells of graphite grease and diesel fuel ... Crazy to think about the guys (kids) that crewed those boats. Tiny, cramped, crowded quarters, crap food, stuffed up for 2˝ month long patrols in enemy waters, the constant oily stink of those giant 2 stroke diesel engines breathing through the snorkel tubes, and the only relief you get relief from that is when you're running silent and deep, right on the verge of being depth charged or torpedoed and suffering a most unpleasant death in the crushing pressure at the bottom of the sea...


Let's see a 19 year old kid do that today. They don't even trust themselves to own a gun.
Reply With Quote
  #5  
Old 03-26-2018, 10:07 PM
Functional Artist's Avatar
Functional Artist Functional Artist is offline
Senior Member
 
Join Date: Jul 2016
Location: Toledo, Ohio
Posts: 1,997
Thanks: 767
Thanked 753 Times in 598 Posts
Default

Real men & serious machinery

Wonder what the fish thought when they saw this thing?
Attached Thumbnails
USS Torsk.jpg  
__________________
RESISTANCE IS FUTILE
Reply With Quote
The Following 2 Users Say Thank You to Functional Artist For This Useful Post:
anickode (03-26-2018), RangerRob007 (06-15-2018)
  #6  
Old 03-26-2018, 10:38 PM
Functional Artist's Avatar
Functional Artist Functional Artist is offline
Senior Member
 
Join Date: Jul 2016
Location: Toledo, Ohio
Posts: 1,997
Thanks: 767
Thanked 753 Times in 598 Posts
Default

Here is some more interesting info I found, it's for designing racecars but, most info should still pertain

Chassis explained

As you design a racing car, it is important that you know the requirements of your engineering work. The nature of the race car's normal operation and fatigue life depend on the structure and material composition of the car. Therefore, topics such as metallurgy and structural design are important for the designer to grasp. The whole concept of engineering considerations is that you keep in mind four aspects, where they are appropriate:

Any good chassis must do several things:
•Be structurally sound in every way over the expected life of the car and beyond. This means that nothing will ever break under normal conditions.
•Maintain the suspension mounting locations so that handling is safe and consistent under high cornering and bump loads. This means that there is no flexing of the body, or at least to reduce flexing on lowest possible value.
•Support the body panels and other components so that evevrything feels solid and has a reliable life span.
•Protect the driver from external intrusion.

Structural stiffness is the basis of what you feel at the seat of your back bottom. It defines how a car handles, body integrity, and the overall feel of the car. Chassis stiffness is what separates a great car to drive from what is merely OK.
Contrary to some explanations, there is no such thing as a chassis that doesn't flex, but some are much stiffer than others. Even highly sophisticated Formula 1 chassis (actually, Formula 1 has monocoque structure) flex, and sometime some limited and controlled flexing is built in the car.
The range of chassis stiffness has varied greatly over the years. Basic chassis designs each have their own strengths and weaknesses. Every chassis is a compromise between weight, component size, complexity, vehicle intent, and ultimately, the cost. And even within a basic design method, strength and stiffness can vary significantly, depending on the details.
There is no such thing as the ultimate method of construction for every car, because each car presents a different set of problems.
Some think an aluminium chassis is the path to the lightest design, but this is not necessarily true. Aluminium is more flexible than steel. In fact, the ratio of stiffness to weight is almost identical to steel, so an aluminium chassis must weigh the same as a steel one to achieve the same stiffness. Aluminium has an advantage only where there are very thin sections where buckling is possible - but that's not generally the case with tubing - only very thin sheet. And even then, aircraft use honeycombed aluminium to prevent buckling. In addition, an aircraft's limitation is not stiffness, but resistance to failure. Aluminium problems are overcomed something with Audi Aluminium Spaceframe (ASF), very expensive and for now made in limited models.

Ladder Chassis (Body on frame technology)

This is the earliest kind of chassis. From the earliest cars until the early 60s, nearly all cars in the world used it as standard. Even in today, most SUVs still employ it. Its construction, indicated by its name, looks like a ladder - two longitudinal rails interconnected by several lateral and cross braces. The longitude members are the main stress member. They deal with the load and also the longitudinal forces caused by acceleration and braking. The lateral and cross members provide resistance to lateral forces and further increase torsional rigidity. Since it is a (little bit more than) 2 dimensional structure, torsional rigidity is very much lower than other chassis, especially when dealing with vertical load or bumps.
This technology you can find today in some basic auto racing categories. Most known is kart. On picture below you can see chassis of an Superkart car without bodywork.

Backbone chassis

Backbone chassis is a type of a car construction chassis that is similar to the ladder design. Instead of a two-dimensional ladder type structure, it consists of a strong tubular backbone (usually but not always rectangular in cross section) that connects the front and rear suspension attachment areas. The tunnel or backbone becomes a primary load bearing member.

Backbone chassis is very simple: a strong tubular backbone connects the front and rear axle and provides nearly all the mechanical strength.

Inside backbone is space for the drive shaft in case of front-engine, rear-wheel drive layout like in the case of Lotus Elan. The whole drivetrain, engine and suspensions are connected to both ends of the backbone. A body is then placed on this structure.
It is almost a trademark design feature of Czechoslovak Tatra heavy trucks (cross-country, military etc.), but this type of chassis is also often found on small sports cars. It also does not provide protection against side collisions, and has to be combined with a body that would compensate for this shortcoming.

http://www.formula1-dictionary.net/chassis.html

I kinda like this Backbone chassis concept
...but, it's like "too" simple
Attached Images
    
__________________
RESISTANCE IS FUTILE
Reply With Quote
  #7  
Old 03-26-2018, 11:08 PM
Kartorbust's Avatar
Kartorbust Kartorbust is online now
Senior Member
 
Join Date: Feb 2016
Location: Lincoln, NE
Posts: 2,818
Thanks: 599
Thanked 757 Times in 637 Posts
Default

The DeLorean DMC-12 and Lotus Espirit are cars that used the backbone design. If I was doing a 2 seater kart/buggy, it's a design I'd be considering using, or ladder.
__________________
In the age of information, ignorance is a choice.
Reply With Quote
  #8  
Old 03-26-2018, 11:13 PM
anickode's Avatar
anickode anickode is offline
Senior Member
 
Join Date: Apr 2010
Location: S.E. Michigan
Posts: 1,796
Thanks: 59
Thanked 800 Times in 555 Posts
Default

Even better is a backbone design that incorporates the driveline components as structural members rather than something to be supported.

Not that there's much option for that on a go kart... Chains are notoriously floppy.
Reply With Quote
  #9  
Old 03-26-2018, 11:15 PM
Kartorbust's Avatar
Kartorbust Kartorbust is online now
Senior Member
 
Join Date: Feb 2016
Location: Lincoln, NE
Posts: 2,818
Thanks: 599
Thanked 757 Times in 637 Posts
Default

Well backbone design would work well for front engine designs. Use it as a chain guard and also could use it to run a jackshaft, without taking up space.
__________________
In the age of information, ignorance is a choice.
Reply With Quote
  #10  
Old 03-27-2018, 07:29 AM
ezcome-ezgo's Avatar
ezcome-ezgo ezcome-ezgo is offline
G'me sumthin to write on
 
Join Date: Aug 2015
Location: Atlanta, GA
Posts: 3,015
Thanks: 2,481
Thanked 1,006 Times in 807 Posts
Default

"Protect the driver from external intrusion."

QOTD
__________________
My name is Sylvester McMonkey McBean. I will make a decontamination.
Reply With Quote
  #11  
Old 03-27-2018, 08:39 AM
Functional Artist's Avatar
Functional Artist Functional Artist is offline
Senior Member
 
Join Date: Jul 2016
Location: Toledo, Ohio
Posts: 1,997
Thanks: 767
Thanked 753 Times in 598 Posts
Default

Quote:
Originally Posted by Kartorbust View Post
The DeLorean DMC-12 and Lotus Espirit are cars that used the backbone design. If I was doing a 2 seater kart/buggy, it's a design I'd be considering using, or ladder.
Yup, the DeLorean DMC-12 (the only model ever produced) used a backbone style frame

IMHO
An actual, backbone chassis is basically, a tunnel or tube that the front & rear wheels attach to (directly or with suspension) & incorporates most of the drive line within, (drive shaft, differential, drive axles & bearings) which kept everything evenly lubricated, protected the lubrication from debris, protected the components from corrosion & also helped protect everything from external damage.

The fabricated box "X-frame" like DeLorean used, is more of a hybrid. It is a backbone chassis designed & built using Monocoque techniques & also has some Ladder chassis style features.
Attached Thumbnails
delorean-dmc-12-back-future.jpg   Delorean Backbone-Chassis.jpg  

__________________
RESISTANCE IS FUTILE
Reply With Quote
  #12  
Old 03-27-2018, 08:58 AM
Functional Artist's Avatar
Functional Artist Functional Artist is offline
Senior Member
 
Join Date: Jul 2016
Location: Toledo, Ohio
Posts: 1,997
Thanks: 767
Thanked 753 Times in 598 Posts
Default

Quote:
Originally Posted by anickode View Post
Even better is a backbone design that incorporates the driveline components as structural members rather than something to be supported.

Not that there's much option for that on a go kart... Chains are notoriously floppy.
On an electric kart the battery pack is, usually, the heaviest component after the driver.

I am thinkin' about a backbone chassis design that incorporates the battery box as a structural member rather than something to be supported.

This way most of weight of the batteries could be centrally located & spread out along the length of the frame.
The driveline (the battery cables, speed controller & most of the wiring connections) could be mounted & ran thru the inside of the tunnel/tube & would be protected in the true spirit of a backbone chassis
__________________
RESISTANCE IS FUTILE
Reply With Quote
  #13  
Old 03-27-2018, 10:31 AM
anderkart's Avatar
anderkart anderkart is online now
Moderator
 
Join Date: Apr 2009
Location: Surprise Arizona USA
Posts: 6,105
Thanks: 496
Thanked 1,160 Times in 961 Posts
Default

If we're talking about go karts with a live axle, a modern racekart chassis would have the advantage on most types of tracks, because they're designed to unload weight from the inside-rear tire while cornering, so the live axle doesn't cause understeering issues. While cornering, they transfer weight from the inside-rear tire, to the outside-front tire...
Reply With Quote
  #14  
Old 03-27-2018, 02:44 PM
Functional Artist's Avatar
Functional Artist Functional Artist is offline
Senior Member
 
Join Date: Jul 2016
Location: Toledo, Ohio
Posts: 1,997
Thanks: 767
Thanked 753 Times in 598 Posts
Default

Quote:
Originally Posted by anderkart View Post
If we're talking about go karts with a live axle, a modern racekart chassis would have the advantage on most types of tracks, because they're designed to unload weight from the inside-rear tire while cornering, so the live axle doesn't cause understeering issues. While cornering, they transfer weight from the inside-rear tire, to the outside-front tire...

Yup,
a live axle + a 40 lb. motor & a 40-60 lb. battery pack = understeering issues "big time"
...been there/done that with the (original) El Dingo kart
http://www.diygokarts.com/vb/showthread.php?t=33680

I am just adventuring & exploring with different chassis/frame ideas & concepts

Most of the vehicles with backbone chassis that I have seen, usually incorporate a differential & half shafts into the rear axle

But, yea
I'm thinking of using a live axle on a light & balanced backbone chassis style kart
Still researchin' & bouncing ideas around
__________________
RESISTANCE IS FUTILE
Reply With Quote
  #15  
Old 03-27-2018, 04:27 PM
Functional Artist's Avatar
Functional Artist Functional Artist is offline
Senior Member
 
Join Date: Jul 2016
Location: Toledo, Ohio
Posts: 1,997
Thanks: 767
Thanked 753 Times in 598 Posts
Default

Here is more frame/chassis info


Spaceframe

The two most important goals in the design of a race car chassis are that it be lightweight and rigid. Lightweight is important to achieve the greatest acceleration for a given engine power. Rigidity is important to maintain precise control over the suspension geometry, that is, to keep the wheels firmly in contact with the race course surface. Unfortunately these two goals are often in direct conflict. Finding the best compromise between weight and rigidity is part of the art and science of race car engineering.

As ladder chassis was not strong enough, and provide small rigidity values, motor racing engineers developed a 3 dimensional design - Tubular space frame.

The spaceframe chassis is about as old as the motorsport scene. Its construction consists of steel or aluminum tubes placed in a triangulated format, to support the loads from suspension, engine, driver and aerodynamics. A true space frame has small tubes that are only in tension or compression - and has no bending or twisting loads in those tubes. That means that each load-bearing point must be supported in three dimensions.

Tubular space frame chassis employs dozens of circular-section tubes (some may use square-section tubes for easier connection to the body panels, though circular section provides the maximum strength), position in different directions to provide mechanical strength against forces from anywhere. These tubes are welded together and form a very complex structure, as you can see in the left picture.

For higher strength required by high performance sports cars, tubular space frame chassis usually incorporate a strong structure under both doors, hence result in unusually high door sill and difficult access to the cabin.

In the early 50s, Mercedes-Benz created a racing car 300SLR using tubular space frame. This also brought the world the first tubular space frame road car, famous 300SL Gullwing. Since the door sill dramatically reduced the accessibility of cabin, Mercedes had to extend the doors to the roof so that created the "Gullwings".

Since the mid 60s, many high-end sports cars also adopted tubular space frame to enhance the rigidity / weight ratio. However, many of them actually used space frames for the front and rear structure and made the cabin out of monocoque to cut cost.

There are also some inherent advantages to using spaceframes at the amateur level of motorsport as well. Spaceframes, unlike the monocoque chassis used in modern Formula 1 or CART, are easily repaired and inspected for damage.

Triangulation

How does triangulation work? The diagram below shows a box, with a top, bottom and two sides, but the box is missing the front and back. The box when pushed collapses easily because there is no support in the front or back.

Of course, race cars (or any other car for that matter) need to be supported in order to operate properly, and so we triangulate the box by bracing it diagonally. This effectively adds the front and back which were missing, only instead of using panels, we use tubes to form the brace. See below:

The triangulated box above imparts strength by stressing the green diagonal in Tension. Tension is the force trying to pull at both ends of the diagonal. Another force is called Compression. Compression tries to push at both ends of the diagonal (Shown above in the horizontal yellow tube). In a given size and diameter tube or diagonal, compression will always cause the tube to buckle long before the same force would cause the tube to pull apart in tension. As an experiment, try pulling on the ends of a pop can, one end in each hand. Then, try crushing the can by pushing on both ends. The crushing is much easier, or at least humanly possible, compared to pulling the can apart.

Spaceframes are really all about tubes held together in compression and tension using 3D pyramid-style structures, and diagonally braced tube boxes. A true spaceframe is capable of holding its shape, even if the joints between the tubes were hinges. In practice, a true spaceframe is not practical, and so many designers "cheat" by using stronger materials to support the open portions of the structure, such as the cockpit opening.

Torsional rigidity applies to spaceframes too, but because a spaceframe isn't made from continuous sheet metal or composite panels as in monocoque design, the structure is used to approximate the same result as the difficulty to twist "cigar car".

Another reason torsional rigidity is mentioned here is that it greatly affects the suspension performance. The suspension itself is designed to allow the wheels/tires to follow the road's bumps and dips. If the chassis twists when a tire hits a bump, it acts like part of the suspension, meaning that tuning the suspension is difficult or impossible. Ideally, the chassis should be ultra-rigid, and the suspension compliant.

It is important to ensure that the entire chassis supports the loads expected, and does so with very little flex.

Advantage of spaceframe is that is very strong in any direction compared with ladder chassis and metal monocoque chassis of the same weight. Disadvantage is that is very complex, costly and time consuming to be built. Impossible for robotized production. Besides, it engages a lot of space, raise the door sill and result in difficult access to the cabin.

Monocoque

In contrast to Spaceframes, the monocoque chassis uses panels, just like the sides of the box pictured below. Instead of small tubes forming the shape of a box, an entire panel provides the strength for a given side.

A common shape for 1960s racing cars of monocoque construction was the "cigar". The cylindrical shape helped impart something called Torsional rigidity. Torsional rigidity is the amount of twist in the chassis accompanying suspension movement.

Monocoque, from Greek for single (mono) and French for shell (coque) (monoshell), is a construction technique that supports structural load by using an object's external skin as opposed to using an internal frame that is then covered with a non-load-bearing skin. Monocoque construction was first widely used in aircraft in the 1930s. Structural skin or stressed skin is other terms for the same concept. A welded unit body is the predominant automobile construction technology today.

Modern car monocoque chassisToday, 99% cars produced in this planet are made of steel monocoque chassis, thanks to its low production cost and suitability to robotized production.

Monocoque is a one-piece structure which defines the overall shape of the car. In fact, the "one-piece" chassis is actually made by welding several pieces together. The floorpan, which is the largest piece, and other pieces are press-made by big stamping machines. They are spot welded together by robot arms (some even use laser welding) in a stream production line. The whole process just takes minutes. After that, some accessories like doors, bonnet, boot lid, side panels and roof are added.

Monocoque chassis also benefit crash protection. Because it uses a lot of metal, crumple zone can be built into the structure. Another advantage is space efficiency. The whole structure is actually an outer shell, unlike other kinds of chassis, therefore there is no large transmission tunnel, high door sills, and large roll over bar etc. Obviously, this is very attractive to mass production cars.

There are many disadvantages as well. It's very heavy, thanks to the amount of metal used. As the shell is shaped to benefit space efficiency rather than strength, and the pressed sheet metal is not as strong as metal tubes in spaceframe construction or extruded metal, the rigidity-to-weight ratio is also the lowest among all kinds of chassis bar the ancient ladder or backbone chassis.

Although monocoque is suitable for mass production by robots, it is nearly impossible for small-scale production. The setup cost for the tooling is too expensive - big stamping machines and expensive moldings.
Attached Thumbnails
not triangulated box demo.gif   triangulation box demo.gif  

box demo with end panels.gif   chassis_tortional_rigidity.gif  

__________________
RESISTANCE IS FUTILE
Reply With Quote
  #16  
Old 03-29-2018, 11:24 AM
Functional Artist's Avatar
Functional Artist Functional Artist is offline
Senior Member
 
Join Date: Jul 2016
Location: Toledo, Ohio
Posts: 1,997
Thanks: 767
Thanked 753 Times in 598 Posts
Default

Now, lets look into the "load" that the chassis/frame will have to support.
There are a couple of different kind "loads" to keep in mind.
The static load is the weight that the frame has to support when the kart is standing still.
The dynamic load is the weight of the kart plus the force of moving that weight & stopping that weight.

This explains it a bit more

Static Load vs. Dynamic Load
The main difference between a static and dynamic load lies in the forces produced by the weight of an object. When static, the load remains constant and doesn't change over time. With a dynamic load, some outside factor causes the forces of the weight of the load to change. Some of the factors that can affect a load and make it dynamic include:

Movement: If the holder of a load is in motion, chances are that the force created by the weight distribution could change. This means that such changes in force must be taken into account when moving a load from one place to another.
Increased tension: Tension is created when two loads struggle against one another. This increase can make the forces of the weight shift from one load to another. The result is that the bigger load has a greater impact on the smaller load, maybe even causing it to become unbalanced.
An outside force: Air, water and ground movement can cause a load to shift. This shifting usually causes changes to the force of the weight as well. This means whatever is holding the weight needs to adjust to compensate for the changing force.


Examples of a Static and Dynamic Load
A good example of a static load is a truck with cargo inside sitting still in one spot. The force of the weight of the load has little chance of changing as long as the truck remains still. Once the truck begins to move, the load becomes dynamic, as the force of the movement can cause the load to shift, changing the effect of the force of the weight of the cargo. If the truck goes too fast, it could even cause the forces of the load to shift greatly, causing it to fall or to at least make it harder to drive the truck on the road's surface. Also, when stopping, the force of the weight of the load can shift forward, making it harder to stop the vehicle as quickly.

A bridge represents another example of static and dynamic forces in play. The weight of the bridge is a static load, as it doesn't change over time, as long as nothing moves across it or outside forces, such as the wind, don't move against it. A truck moving across the bridge places a dynamic load on the bridge by increasing the weight of the bridge as it crosses. A wind blowing against the bridge can also change the forces of the weight of the bridge, as it moves it from side to side, creating a dynamic load on the bridge. That is why it is important that engineers take all of the forces that might apply to a particular bridge in order to design a stable and safe structure. Another important force to keep in mind is torsion, with any twisting of the bridge in the wind causing additional tension on the structure, which in turn can affect how much of a load the bridge can handle.
__________________
RESISTANCE IS FUTILE
Reply With Quote
  #17  
Old 03-29-2018, 02:28 PM
Functional Artist's Avatar
Functional Artist Functional Artist is offline
Senior Member
 
Join Date: Jul 2016
Location: Toledo, Ohio
Posts: 1,997
Thanks: 767
Thanked 753 Times in 598 Posts
Default

Well, that leads us to,

"Another important force to keep in mind is torsion"

IMO I think, "torsional rigidity" is what is needed to be considered when designing & choosing materials for a chassis or frame. (especially on a backbone chassis)


"Rigidity is the maximum resistance an object can offer before it deforms, in other words, it is the minimum force required to deform an object.

Torsional Rigidity : The minimum force required to deform an object by twisting through a unit dimension..(in this case, for twisting the dimension is in angle of twist)

Lateral Rigidity : Again, the same logic.. The minimum force required to deform an object by bending along the lateral axis through a unit dimension..in this case, the dimension of bending is normally in mm or other length measure scale.. (if the bending load is applied on the longitudinal axis, then the object will not bend, instead the load will act like a compression load)"


So, for a backbone chassis the design & the materials used for the backbone have to be rigid enough to
...support the weight of the kart (everything between the wheels-frame, motor, batteries, driver etc.)
...support that weight while moving, turning & stopping
but, also flexible enough to take some bumps, while supporting that weight @ ~20mph

* Think about the dynamic load that is applied to a kart frame when doing a "Power Slide"
...or while doing donuts
...that's a lot of load
Attached Thumbnails
torsion.jpg   TorsionConstantBar.png  

Chassis_TorsionalRigidity.png  
__________________
RESISTANCE IS FUTILE
Reply With Quote
  #18  
Old 03-31-2018, 10:05 PM
Functional Artist's Avatar
Functional Artist Functional Artist is offline
Senior Member
 
Join Date: Jul 2016
Location: Toledo, Ohio
Posts: 1,997
Thanks: 767
Thanked 753 Times in 598 Posts
Default

Bouncing around some ideas

The simplest backbone chassis would be an "H" shape (kinda like a clothesline pole)

Think of a ~4" x 40" round tube/pipe (backbone chassis) with a couple of ~4" x 24" round tubes/pipes welded on each end (front & rear axles)

But, having long "arms" sticking off each side like that (~4 x the width of the chassis) would require a lot of extra supports & braces.
&
being mostly 2 dimensional, that kind of leverage could/would apply a lot of twisting force

A wishbone style or even a double wishbone frame/chassis would seem to be better designs (or at least going in the right direction) but, where would the batteries go?
...saddle bag style hanging off either side of the backbone

An "X" frame with more of a (3) dimensional design looks like it would be super rigid but, it would probably be really heavy & a lot of work to construct
Attached Thumbnails
SAM_8393.jpg   SAM_8394.jpg  

Backbone twist test.jpg   SAM_8391.jpg  

SAM_8396.jpg   SAM_8399.jpg  

__________________
RESISTANCE IS FUTILE
Reply With Quote
  #19  
Old 04-01-2018, 11:14 AM
Functional Artist's Avatar
Functional Artist Functional Artist is offline
Senior Member
 
Join Date: Jul 2016
Location: Toledo, Ohio
Posts: 1,997
Thanks: 767
Thanked 753 Times in 598 Posts
Default

Lets examine the weight on a kart & how it is spread out
...then look into balance & symmetry

Rear wheels ~30 lbs, (~15 lbs. ea.)
Motor ~20 lbs.
Batteries ~35 lbs. (~8 lbs. ea.)
Operator ~150 lbs.
Front wheels ~15 lbs. (~7 lbs. ea.)

The design in the (2nd) pic is pretty well balanced
~50 lbs. in the rear (motor & rear wheels), ~150 lbs. in the middle (operator) & ~50 lbs. in the front (batteries & front wheels)

The (3rd) pic shows how unevenly the weight is distributed on the !ARRIBA! kart.
~100 lbs. in the rear, ~150 in the middle & only ~20 lbs. in the front

The (4th) pic shows (top view) how nicely everything can be balanced.
...& symmetrical (left half is a mirror image of the right half)
Attached Thumbnails
SAM_8405.jpg   SAM_8401.jpg  

SAM_8402.jpg   SAM_8404.jpg  

__________________
RESISTANCE IS FUTILE
Reply With Quote
  #20  
Old 04-01-2018, 04:33 PM
Functional Artist's Avatar
Functional Artist Functional Artist is offline
Senior Member
 
Join Date: Jul 2016
Location: Toledo, Ohio
Posts: 1,997
Thanks: 767
Thanked 753 Times in 598 Posts
Default

Bouncing around some more ideas
...starting to "zero in" on where were going

Need to design a frame that is strong & light weight, rigid but, slightly flexible & evenly balanced

Choosing materials:
What are we gonna make this thing out of?
What shape would work best? round, square, custom?

Pic #2 shows a (2) part (top/bottom) custom bent battery box style frame
Pic #3 shows an "H" style frame made with round pipe/tube
Pic #4 shows a Backbone/Wishbone hybrid made with square tube
Attached Thumbnails
SAM_8448.jpg   SAM_8449.jpg  

SAM_8450.jpg   SAM_8451.jpg  

__________________
RESISTANCE IS FUTILE
Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off



All times are GMT -6. The time now is 09:56 AM.