Author Archive for Stephen Burke  Page 2 of 3



Red Bull Soap Box Race in Belfast (25 May, 2008)

Red Bull SoapBox RaceLooks like its too late to enter this years Red Bull Soapbox race in Belfast on May 25th, 2008. What a pity. Still the event itself should be a good laugh with plenty of ideas and soapbox carts/karts to see with 47 teams been given “Soap Box Racing licences”. The event seems planned very well, with plenty of information on the RedBull website, including details on brakes and steering!

Attending the race is free to the public, and as the teams are from all over Ireland/N.Ireland it’ll be well worth a visit.

Soap BoxSo, what is a Soap Box? They are simple vehicles which reply completely upon gravity. Typically they are raced together as part of a “Soap Box Derby” which is exactly what is happening with the Red Bull Soapbox race.

Keep the ideas and kartbuilding going!

EDIT:
Due to the interest and questions recieved about Red Bull Soapbox racing via email, some vidoes of previous races can be found on youtube. The following are two relevant ones. The first video shows part 1 of the construction of a soapbox racer. The second video shows one of the soapbox carts in action.

 

Preview: Off Road Kart Plans in the making.

Apologies for not blogging here in quite a while. Behind the scenes more plans and material is been made. Below is a preview of plans for an off-road kart currently being drawn up. Full cutting lists and bills of materials will be created covering all aspects of building the off-road kart, using commonly available materials and parts. For example, for the seat below, which is a modified plastic chair with side reinforcements and padding, will be fully descibed with details on how to adapt it to suit. The wheels shown below are from a wheelbarrow! The idea of these kart plans is to provide details and information on making a low-cost, low-budget kart.

Overview of Off-Road Kart

Front Elevation of the Off-Road Kart

Plan View of the Off-Road Kart

End View of the Off-Road Kart

Off-Road Kart as built

The plans being drawn will contain all the details and information of the the above kart (photo). It will be a few months however before the all the plans, details and information is fully completed for the above kart, so check back soon. If you have any ideas on what should be included in the Plans for this Off-Road Kart, please get in touch and let us know.  

Stay tuned!

Going Karting

goingkarting

GoingKarting.co.uk: This website offers great tips and advice to help you get the most out of go-karting. There is some good general knowledge on karting, with all types of karts (pedal to petrol etc.) been covered for both young and old. It also has information on setting up a karting meeting.

Worth a look.

SolidWorks CAD Drawing of a Tony Kart Chassis

ABout Tony Kart

Tony Kart produces high quality racing kart chassis. A catalogue of their kart chassis can be found on their website. A particular chassis model, a Tony Kart Extreme ’97, was modelled using SolidWorks, and is available for download. Below is an overview of the chassis, in isometric and in a plan view.

Overview of Chassis in SolidWorks

This chassis is modelled perfectly in SolidWorks, with each member as an individual part and fully in-context. With the complete assembly and part files, it would be very easy to create 2d drawings of the chassis. The chassis is full size, so no scaling would have to be carried out.
Perhaps in the future the author will complete a fully dimensioned chassis using SolidWorks. Please contact the author if you have any queries etc. regarding this.

Download SolidWorks Files

The SolidWorks assembly file can be downloaded from its original location here, along with some other CAD drawings also. A backup local copy of the SolidWorks chassis is also available.

eDrawings Download of the Chassis

In case you don’t have a copy of SolidWorks to open and measure the components, the eDrawings viewer can be used to open the chassis, measure each component, and create a section view through the chassis. The chassis opened in eDrawings can be seen below:

Tony Kart Chassis in eDrawings

Download the Tony Kart Chassis ’97 eDrawing
Note: the eDrawings download of the chassis contains a self executable viewer application.

Conclusion

Hopefully the detailed professional chassis design will give you ideas on how to design and create your own chassis. An idea of the size of the chassis design can also be obtained using the eDrawing. Best of Luck!
If you have any queries or comments, please email them to the author at:

Edit: A few people emailed me asking for the above Tony Kart in AutoCAD DWG Forma: PDF Format of Tony Kart | DWG Format of Tony Kart (in a Zip File) | STEP Format (in a Zip File)

Vintage Go-Karts: A Website Review

The following website (http://www.vintagekarts.com/karts.htm) has some excellent photos and articles on old vintage go-karts. These karts were made using the basic necessities, and still achieved high speeds with excellent cornering and handling. Several ideas can be taken from these vintage karts where there were “no frills” to building gokarts. Ideas which can be combed from the gallery of photos include:

  • Twin Engines
  • Simple friction brakes
  • Types of Seats
  • Keeping Chassis Designs Simple

Thumbnail Previews of VintageKarts.com’s Gallery: 

      

View more photos here: http://www.vintagekarts.com/gallery.htm

Preview of VintageKarts.com’s Articles:

There are also some excellent in-depth articles about the history of karting, right up to the current day! Some of the topics discussed include:

  • Karting Grand Nationals, from 1960 to 2005
  • Transportation of GoKarts
  • Women Gokart Racers
  • Rocket Powered Karts
  • McCulloch’s Entry into Karting

Hopefully this website will provide further insight and details as to how simple engine powered gokarts were and can be made. If you would like your karting website reviewed and mentioned here, or if you have any comments on this or any other article, please contact the author by email at

Video on making a Go-Kart with Suspension

Dirt Devil KartThe following well produced video shows the stages involved in making a Go-Kart using the Dirt Devil  kart plans. The stages shown in the video below are:

  • Welding, Cutting and making the Chassis
  • Obtaining parts for the Suspension
  • The 18hp Engine
  • The Rear brake Calliper
  • Steering Setup
  • Testing and Racing the Go-Kart with Suspension

A lot of parts were taken from a quad and an other working go-kart! The suspension seems to work very well, however the camber angle on the front wheels seems too much. The front wheels are splayed out sidewards. Perhaps this is the suspension, but ideally this would need to be readjusted. Read more on camber angles here.

Free Technical Kart Drawings (FIA)

CIA LogoThe CIA (Commission Internationale de Karting) is the specialised Karting commission of the FIA, the governing body of world Motor Sport. The CIA oversees Karting safety in conjunction with the FIA and with a Research Group exclusively dedicated to Karting.

The CIA publish Technical Regulations for Karting, which includes detailed Drawings and specifications. In their most recent publication (2007), detailed drawings showing measurements and designs for Kart chassis are included.

CIA Sample Kart Chassis Technical Drawing

The drawing above shows actual sizes (metric also!!) of Karts and provide an excellent guide to building a Kart complete to regulation!! Many people, including myself develop free kart plans, and overlook the wealth of information and diagrams offered by Karting Authorities such as the CIA.

Original Reference Hyperlink to CIA’s 2007 Technical Regulations
Saved local copy of the CIA_2007_Technical_Kart_Regulations

Some more Drawings from the above Technical Regulations can be seen below:

CIA_Sample_Technical_Chassis_Drawing_Front_Elevation

CIA Technical Kart Drawing

Steering Geometry and Setup for Go-Karts

There are three different factors when deciding on the Steering Geometry for Go-Karts. Those are:

  1. Castor Angle
  2. Camber Angle
  3. Ackermann Angle

This article covers the above three factors in relation to Go-Karts with no suspension, and outlines typical angles and geometry which should be used. The information for this article is taken from “The NatSKA Guide to Karts and Karting” and is currently available on ebay! The off-road kart plans, and racing kart plans on this website, take into account these steering geometry angles and match the values in the above Guide.

Parts of the Steering Setup on a Kart

Steering Terminology on KartsThe (1) Stub-Axle, (2) n shaped Yoke, (3) King-Pin Post make up the essential parts of the steering.
The King-Pin Post is attached/welded to the chassis.
The n shaped Yoke pivots/hinges on the King-Pin Post.
The Stub-Axle is attached to the n shaped Yoke.

These three parts are welded/attached at various angles to make steering easier on a kart. The practical side/making of these parts are not discussed here, and instead just the theoretical setup.

Castor Angle

Castor AngleThis is the inclination of the King Pin whose top leans in a backwards direction towards the rear of the kart. This is the most important factor governing how the kart will handle. This is however, interrelated with the other angles. In the case of the King Pin inclination, the greater the angle, the greater the “jacking effect” on the chassis, and the greater the oversteer the kart will develop. If there is too little, the kart will tend to understeer. The greater the angle, the heavier the steering and tendency to self-center. In practice, many people settle for angles between 20 and 25 degrees.

Camber Angle

Camber AngleThis is the inclination inwards at the top of the king pin towards the center of the kart, and it is aimed at counter-acting the jacking effect of the castor: at the same time it helps to produce a stronger joint, which will be able to withstand higher shearing forces. Generally this angle is between 10 degrees and 12 degrees, and to allow the wheels to stand flat on the floor, is offset by a similar angle on the stub axle.

Ackermann Angle

Ackermann AngleThis refers to the placement of the steering arms (when viewed from above), in relation to the chassis, and the rear axle. Ideally, lines projected through the center of the King Pins, and through the bolts holding the track rods, should meet at the center point of the rear axle. The effect of this is that the inside wheel always describes a smaller radius arc than the other wheel, when the kart is being turned – this is most especially important at low speeds, and on tight corners. The length of the steering arm, in relation to the spade/drop arm, effects the “speed” of the steering reaction. A long steering arm causes slow but very light steering, whereas a short arm causes quick steering but requires greater effort.

Correct Placement/Arrangement of n shaped Yoke

Correct Steering Setup on a KartAs can be seen from the following image, there are two possible arrangements of the n shaped Yoke. It can be attached to the chassis, or it can be attached to the stub axle (recommended). It is recommended that you attach the “King Pin Post” to the chassis, and that the n shaped yoke is attached to the front stub axle. This will make it easier if you are installing brakes on the front wheels. It also provides for greater clearance for the steering arm.
Result of Incorrect Steering setupThe problem with installing the n shaped Yoke on the chassis, is that when attempting to achieve “full steering lock” the steering arm hits off the n shaped Yoke. This was found on a previous kart and a notch had to be removed from the steering arm to allow for extra steering lock.

Conclusion

There does be a lot of debates regarding the ideal steering setup for karts, and especially when deciding on the actual angles to use for King Pin Inclination (KPI), Camber Angles and Castor Angles. All these angles are interrelated and allow for a Go-Kart with no suspension and a solid live rear axle to steer smoothly. If you have any comments, questions or queries about this article, feel free to email me: Mail

EDIT: There is also an excellent article cover some of the above, and also toe-in and toe-out on Racing Cars (Formula 1 etc.) http://www.ozebiz.com.au/racetech/theory/align.html
EDIT: Another excellent article with interactive Flash Diagrams http://www.bcot1.com/karting/ (local)

Popular Mechanics: Rotax Racing Go-Karts and a Honda ATV

Popular Mechanics LogoPopularMechanics is well established magazine, and has an excellent website where there are two very good articles under the theme of kartbuilding:

Doing 100mph in a Rotax Go-Kart

This article describes how a Rotax Go-Kart with a 34hp two-stroke engine of a mere 125cc! can achieve 100mph!! Including the driver, the total weight of the kart comes to only 300 pounds (or 136kg), with dual disc brakes on the rear axle, and disc brakes on each front wheels.

The Go-Kart has an amazing transmission. It has a 2 speed direct drivetrain which is chainless and shifts electronically via two large paddles mounted onto the steering wheel. There is an electric starter which can also move the kart in reverse!!

Overall its an excellent article with some very informative and detailed photos, and well worth a look. If you don’t have the $8000 money to buy it, you might at least get some good ideas! The article again is located at: http://www.popularmechanics.com/outdoors/adventures/1278136.html

Details, Specs and Trial of a Honda ATV (Foreman Rubicon 400)

Although this article was written in 2000, it contains some up-to-date details and information on the transmission and capability of an ATV (All Terrain Vehicle). Details on the “Hondamatic” transmission providing engine braking are included, along with Limited Slip Differential are included! This article is definitely for the off-road enthusiast.

There are no exact details on the engine specs or the costs. There is also a hayes owners workshop manual available for this ATV. Perhaps some of the technology could be taken off one of these ATVs and transplanted into a Off-Road Kart.

The article again is located at:
http://www.popularmechanics.com/outdoors/adventures/1277601.html

Safety Factors for Designing and Building Go-Karts

Introduction to Factor of Safety

Recently, a person emailed me (kartbuilding[at]gmail.com) asking about the “factor of safety” (FoS) required when undertaking calculations to design and make a go-kart. The “factor of safety” is the maximum force and stress a kart can possibly undergo, multiplied by a suitable factor/multiplier. Ideally if the maximum force and stress a kart can endure is calculated, then this factor gets multiplied by the factor of safety.
Having a FoS of 1, means that a Go-Kart is not “overengineered”, and nothing extraordinary will occur. It is when the “extraordinary” or unthinkable happens, that the FoS comes into effect.

Quantifying the Factor of Safety

Quantifying the FoS for a Go-Kart is not an easy task! It certainly cannot be applied to the entire Go-Kart, but parts of it, e.g. the chassis, transmission, brakes, etc. The same FoS cannot be applied to the chassis in every Go-Kart. The purpose and category of Go-Kart must be firstly determined. I.E. is it a racing kart and in what category of racing kart? Once the category and type of Go-Kart is determined, then a FoS can be obtained.

NatSKA – Classes of Racing Karts, and Safety Regulations

NatSKA LogoNatSKA (The National Association for School and Youth Group Karting) governs the sport and activity of karting in schools throughout the United Kingdom. The association holds race meetings run under strict regulations of its governing body (Motor Sports Association), and periodically publishes a Handbook and Regulations. The most recent Handbook and Regulations (2007) outlines the various “classes” of karts, and range from Class 1 (50cc Single Ratio Open) to Class 16 (Honda C70, C90 and C90 Cub Gearbox). Specific specifications (including safety) are outlined for areas of the kart. The following is an edited exerpt from the NatSKA Kart Regulations on chassis design:
The chassis in general shall be of safe, sound and adequately strong construction and shall not include any components of a temporary nature. Specifically, the wheel base is to be a minimum of 101cm and maximum of 127cm. The maximum length of the kart, including bodywork shall not exceed 210cm. No kart is to weigh more than 100kg without the driver.

I highly recommend that the NatSKA handbook and regulations are read and followed, especially if other people are driving and racing your Go-Kart. At the very least, excellent safety guidelines are outlined.

More Technical “Factor of Safety” etc. – Formula Racing

CAD Stress Tests on a ChassisIf you are designing your own Kart on a CAD system etc. some software will allow you to carry out “Stress Analysis” of components. Some examples of CAD software packages are: Solidworks and Cosmos, Pro-Engineer and Pro-Mechanica. These software packages will allow you to carry out simulation of kart components, allowing you to place particular loads throughout, and calculate a FoS automatically! If you are heavily involved in design and analysis of karts, this CAD software will speed things up, and provide a wealth of information.

Stress Test and Factor of Safety Analysis of a Front Stub Axle from a Go-Kart

Stress Test Result Image on a Front Stub AxleAs an example of the amount of information and the ease at which CAD software can calculate the FOS, a stress test was carried out on a Front Stub Axle from a Go-Kart, as can be seen in the image on the left. The entire CAD HTML Stress Analysis is also available. The plans for this “Front Stub Axle” are contained in the Complete Set of Racing Kart Plans.
This test, taking a total of 10 minutes to model and analyse, found that, if a loading of 50 kilograms were placed onto the steering arm, that the resulting Factor of Safety would be 1.466. Therefore, this Front Stub axle is slightly overdesigned. An in-depth knowledge of the individual forces involved in a Go-Kart would be required for an entire Stress Analysis.

Factors of Safety for Go-Karts in Amusements and Funparks

In doing some research on Factor of Safety for Go-Karts, I came across an “Amusements Devices Act” which makes specific references to Go-Karts and the required Factor of Safety! Although the act (legally binding),  has been superseded by a later document, the numbers and references are interesting to see. Part IV of the above act, pertains specifically to Kart Design! An excerpt of its legal requirements are:

  • The speed of an adult kart shall be limited or governed so as not to exceed 45 kilometres per hour.  R.R.O. 1990, Reg. 20, s. 40 (2).
  • The seat, back rest and leg area of every kart shall be so designed as to retain the driver inside the kart in the event of a collision at the front, rear or side of the kart.  R.R.O. 1990, Reg. 20, s. 41.
  • Rotating, moving or hot engine parts of a kart that may constitute a hazard to an occupant of the kart shall be shielded to prevent burns to the occupant or the entanglement of the occupant’s hair, hands or clothing.  R.R.O. 1990, Reg. 20, s. 42.
  • The wheels of a kart shall be so enclosed or guarded that the wheel of one kart cannot interlock with or ride over the wheels of another kart.

Factor of Safety on Formula Racing Cars

Various universities are taking part in “Formula Student” lots of readily available information about building advanced racing Cars is available. Two excellent reports on designing formula racing cars can be found here and here. The latter document has a section on “Factor of Safety Development”.

Conclusion to Factor of Safety when Designing Karts

The materials used, and the forces involved make the calculations for FOS quite difficult. CAD software makes things much easier, allowing you to select the materials from a drop-down menu, and allowing you to apply forces wherever you require. CAD software will also allow you to change material thicknesses to achieve an optimum FOS, and weight balance.
Using your common sense, and reinforcing areas which would potentially fail in a collision will go a long way in having a robust Go-Kart.
If you have any queries or questions, drop me an email or leave a comment below.