10 Things You Wish You Knew Before You Started Your Go Kart Project

In my adventures over the years I  have fallen into the trap of putting pressure on myself  to make go karts out of junk, out of old tractors, old vertical engines, out of wood….this list goes on.  I am a little special in that I  try to put myself into the shoes of the guy who has nothing, but wants to have some fun with the junk he has sitting around.

There is a two prong approach to this effort in my mind.  I want to get that gokart running and for cheap, but I also want to teach and help others understand the principals behind mechanisms, engines, and vehicle dynamics.

That being said, there are ten things that I had to discover for myself and as hindsight is always 20/20 I am relaying them to you here….

Tip #1

To start the list off, the drive line is so important.  Not having the right driveline is like having a Porsche 911 that is pedal powered.   It can be the most exasperating and exhausting elements of the gokart if not designed properly.  You may have an awesome running engine but a gokart that just smokes the clutch and doesn’t go anywhere.

If I were to tally up the complaints on go karts it would be the drive system.  For example on our Wooden GoKart, the Phi Alpha 20 we did our due diligence in the beginning on the drive line.  We had limited components, but with the calculations program included in with How To Build A Go Kart 203 book we designed our driveline exactly as the program told us, and came up with an awesome accelerating machine that can climb hills and bop around yards.

The vertical engine drive system falls into the same category, though it is a bit different, it too can be tuned to fit optimum hill climbing conditions.  That is why we include our vertical engines drive course (Go Kart Building 202) with all our bundles, because we know the importance of getting the drive line right.

I’ll  let you in a little secret, there is no ONE SIZE fits all drive line, each one needs to be tailored to your go kart, and the Go Kart Building 201, 202, and 203 courses explain how drive lines work and how to get the optimum out of it.

Tip #2

Often I am stuck with time constraints and the balance between what I can scrounge, what I can make , and what I should buy.    The answer to that question is first what do you have that you can use on a gokart?  You may have a 30000 foot level understanding. For example you have a riding lawnmower and you know you could probably use the wheels, the steering wheel, the engine etc..  But the hard question to ask yourself is: How can you use the wheel and hub on a go kart?

Another prime example of using stuff off of a lawnmower is using the rear wheels and tires.  They are fantastically huge and have plenty of wear left.  But the conundrum comes into mating that wheel with an axel.  How is it possible to get a 1 inch live axel to drive a .750 inch diameter  hub?  If you study our blog article on hub-axel transformation you can get that answer.  The point I am making is, do you know how to do it?  If you do not, or you have come to the conclusion it is not possible to do, then that answers your purchasing question: you will have to buy rims and tires.

There are a host of other items on the go kart that require that decision, can I use it? Or do I need to buy it.  I have developed whole go karts and in the end I have come to the conclusion, perhaps I should have bought that part.

This is a small list of parts that if you are not mechanically inclined or don’t have the ambition to fabricate stuff that you should buy:

  1. Front Steering Knuckle Assemblies
  2. Rod Ends and Rod Stock for the steering
  3. Pedals
  4. Rear Axel
  5. Rear Bearings
  6. Brake Caliper
  7. Brake Disc
  8. Rod
  9. Steering Wheel (yes I said steering wheel, unless you know how to mate a tractor steering wheel to a splined shaft system….stay clear and buy a simple steering wheel.)
  10. Rear Drive Sprocket
  11. Clutch

Tip #3

After you have made that list of stuff to buy, then you will complain, “Well golly that is expensive!   I was hoping to spend less.”  That is where you need to have tallied up that list before you start buying stuff.

That’s right;  I said make a list.  Tally up the list, and here is the hard part…walk away and think about it for a day or two.  Then come back and start weighing the list.  Do you have some of the things in the list above that you could perhaps not buy, like rear wheels and hubs?  How much could you save by not buying that stuff?

In my opinion, you can make a seat, you can make a frame, you can make a decent steering system.  Are you willing to make it, or are you stuck on buying it?

Tip #4

Stopping a go kart is actually quite important, especially when the chain link fence is showing its mean acing existence.  Stopping the go kart there is not enough that can be said about it.  So if stopping the go kart is so important then why is it the last thing we think about when we design and built our go kart?

The best and most sure stopping power is to have both rear wheels have brakes.  The simplest system is the live axel, where a brake disc can be mounted easily and the brake caliper mounted to the frame.

Tip #5

When turning the steering wheel the last thing you want to have happen is that the front wheels continue to go straight.  We call that severe understeer.  You want good steering response, and the center of gravity is the answer to this problem.   Getting enough weight on the front wheels is the problem and positioning of the front wheels is the  key to solving this problem.   We offer as a free download the center of gravity spreadsheet which allows you to calculate the center of gravity before you develop your gokart design.  We used the spreadsheet on all of our go kart designs with success.

Tip #6

When you have the go kart all completed and it drives like a dream, it is tough to share it, because it only has one rider.  Because the  go kart that was developed for a larger person, such as an adult, the smaller “eager-to-have-a-thrill-rider” misses out because the go kart only seats one person safely.

So the bottom line is consider  the number of riders as one of your top priorities when you develop a go kart.  This decision will affect the drive system drastically, because now the 5 horsepower engine may now need to be an 8 horsepower, or at least the drive line will need to be tailored to a 5 horsepower so that you still get the thrills.

Also the brake system needs to be upgraded to handle the extra load.

If you haven’t guessed yet but are now figuring it out, it takes some thought when building a go kart and not wanting to bust your budget.

Tip # 7

The glossy eyed go kart lover may want to cut corners and try to use anything available like bike tires or solid style tires used on push mowers.  Stop!  No you cannot use these wheels safely, the power and the demands of go karting will destroy them.  Likewise don’t be fooled into thinking that the Chinese knock- off- 5-dollar wheels and rims are going to last.  They might last an outing, but the bearings might be toast after that.  Also the rubber specked out in these tires is so totally cheap that they will wear through in minutes.  A high quality rubber tire and rim is needed.

Tip #8

I have run into this brick wall a couple of times: bearings.  More specifically, front wheel bearings.  The wheel  bearings (or even bushings) that are on tractor tires or cheap rims will have ¾” diameter bearings.  These cheap bearings cannot take a large amount of load before they literally eat through the casing and then fall apart.

Be very leery of these cheap pressed bearings.  You need industrial grade radial sealed bearings.  The problem is that the inside of the hub will only mate up with a 5/8” roller bearing.  To remedy this problem either the steering knuckles that you just purchased need to be modified so that they can take 5/8” bearings, or you need to fabricate your own.

Careful purchasing of steering knuckles with the 5/8” diameter shafts is required, or you will need to modify the steering knuckles that you just purchased and weld on a grade 8 bolt to replace the steering knuckle bolt.

Tip #9

When constructing a steering system it is important to take into account the amount of steering effort that may be required to turn the steering wheel.   You may be surprised when you start putting camber and castor into your system the amount of effort required to turn the steering wheel.  The reason for this is that the camber and caster put the front wheels at angles which in effect cause the steering to leverage or lift the gokart into the air.  This added amount of leverage can be quite a problem when trying to turn the wheels.  Be aware of these consequences.

For simplicities sake and for the sake of steering ease, you may want to nix the camber and caster, seeing it is just a go kart, not a Ferrari and a Lamborghini.  If you are not willing to nix the camber and caster you may have to make a ratio reduction into your steering system to make the steering easier to turn.

Additionally, when making a two seater gokart the steering forces increase because of the weight.  Make sure all the steering linkages move well when a load is applied.  What can fool you is when you have the go kart on the stand and all appears to turn and move well, but when the go kart is put on the ground all the tire and friction forces come to bear.

To minimize friction make sure all surfaces are lubed well and that the contact surface between the steering knuckles and the channel housing are not binding but have minimal slippage.

Tip #10

Don’t be surprise with all you busy schedules if the go kart does not get completed in a summer.  You really have to have a game plan or as I call it a Realistic Gokart Building Schedule.  We offer as a free download the building schedule in our download section.

Realistically if you have your act together you should be able to get a ready and running go kart in 7 weekends.

These Ten tips are by no means exhausting but they do help with the major road blocks to go kart building.

Be sure to stop by our downloads page or sign up for our free newsletter to get access to our downloads page.  The downloads have products that are a great help for accessing your center of gravity and basic stress calculations.

 

 

VN:F [1.9.13_1145]
Rating: 10.0/10 (2 votes cast)
VN:F [1.9.13_1145]
Rating: +2 (from 2 votes)
Suspensions and Unsprung Wieght

I watched a couple of your youtube videos on suspensions and have a question.

I completed a clutch driven go kart with stub axles and no suspension, but would like to add a torque converter. So I’ll need a live axle, and i thought I I’d add a suspension while I’m at it. The easiest way would be to put the whole rear part of the kart (engine and everything) on a hinge. But I’d heard that a good suspension system minimizes unsprung weight. Having the engine unsprung would seem to be a bad idea. But as you show in your “pitfall ” video, the independent rear whepel suspension looks pretty complex and expensive. I plan to use it mostly off road. It has an 8 hp engine.

Your thoughts?

Answer:

The unsprung weight issue becomes more of a problem if you are looking for high performance applications such as Baha racing and so forth.

The purpose of having a low inertia suspension is to have it return to its relaxed position quickly, so that it is not bottomed out and essentially becoming useless.

The suspension is designed to absorb the impacts that an irregular road surface exhibits.  The trouble is if you are driving along at 50 mph on a road surface in car and then you encounter a corner with a ton of bumps in it, you want the tires in contact with the ground so that the vehicle will react in turning the car around the corner instead of having intermittent road contact and essentially going straight and off the curve.

The suspension weight or mass dictates how fast the suspension is going to react.  The lighter the quicker the suspension will react.   The reaction is for two purposes:

1. Good road contact for optimum directional response
2. Bump absorbtion

We mentioned the good road contact previously, but the bump absorption can be equally important in that the vehicle needs to be able to continue to absorb impacts.  If the suspension is bottomed out, and wont return it essentially is now a solid brick and what hits it now will damage and bend elements in the vehicles such as drive shafts and rims.
On a go kart, the MPH on a rough road situation is not going to be much more than 10 mph.  Suspension response may not be as critical in this  situation.  Having the suspension respond quickly is really the question here.  Is it essential on a go kart?

Depends on how much money you are willing to spend.  If money is an issue, then the compromise of using the total flex rear is acceptable. 

On thing of note on the flexible rear suspension is that the engine should be kept as close as possible to the hinge point as possible, this will lessen the Inertial moment that is require to be rotated.    The nice thing about making the whole rear move together is that the drive line is much, much simpler and durable. 

The chain does not need to be worried about, because the engine and the drive axel relationship doesn’t change, and so the chain will not lengthen and shorten as the suspension moves up and down.   This is a big plus.

So to recap,

The suspension mass is critical for:
1. Suspension response and tire contact for good vehicle performance
2. Suspension response is important for the next bump, will the suspension be ready, or will it be bottomed out.

Low suspension mass is important for fast moving vehicles that encounter large bumps and repeated hammerings.  Baha vehicles for example are designed for speed, vehicle cornering performance, and bump absorption.

VN:F [1.9.13_1145]
Rating: 6.8/10 (5 votes cast)
VN:F [1.9.13_1145]
Rating: 0 (from 2 votes)
How Does the Rear Sprocket To Tire Size Affect Overall Speed and Performance?

Question: Does increasing the rear sprocket size to be the same size (or nearly the same size of the tire) cause the go kart to loose speed, especially as the tire gets bigger?
The question is a peculiar one especially for those that are making their own go kart and are wondering what ratio would work best on the go kart. 

The question is this again, broken down into pieces:

The rear sprocket is the same size as the tire.  If the tire gets bigger (and the rear sprocket correspondingly grows with the tire), what happens to the performance of the go kart?

Actually, nothing.  The speed does not change, and the acceleration does not change.

I thought the answer I gave was preposterous myself, until I did the math.  The following chart shows the corresponding Drive Wheel/Sprocket Sizes versus the overall top speed and acceleration (based on a 5 horsepower engine and a 300 pound gokart):

Sprocket-Wheel Diam Vs MPH and Acceleration

As the wheel diameter changes (the sprocket diameter changing proportionally with it) the top speed (MPH) and the acceleration (FT/S^2) does not change; they remain constant.

It is hard to grasp that as the sprocket and wheel grow together in size, that the overall performance would not suffer, but it does not.

So what does that mean for the go kart drive line enthusiast?  The rule of thumb stands, keep your rear sprocket as large as possible (as close the wheel diameter as possible) and you will have a decent go kart performer. 

As you notice, the ratios in the list all change starting from 6:1; 8:1, 9:1, 14:1 17:1.  So the ratio does not tell the whole story, but is a start.

So how does this knowledge practically apply to a go kart?

If you for example are building a wood go kart, and the rule of thumb is being applied to have the rear sprocket (or pulley) as large us the rear tire, then  what if you upgrade to a larger tire, from your small 7 inchers that you currently have?  The rule of thumb still applies; you will have to make a larger pulley (or sprocket) to make the gokart perform like it did before.
Just in case you are thinking that you do not need to increase the sprocket diameter, because you increased the tire diameter, then you are going to run into stalling smoking clutches, and burning belts.
For more information about drive lines and computer program to help trouble shoot your drive line problems, go to the http://gokartguru.com/go_kart_building_203.php.  In this course you will learn how to calculate and make your own drive line system that will allow your go kart to climb hills without smoking the clutch.
Don’t be caught making a go kart and then have the drive line be the major headache.  And you don’t have to spend a lot of money on drive systems, such as a fancy clutch, just to get what you want.
Again, the go kart drive line course has a computer program that helps maximize your drive line for optimum acceleration and hill climbing performance.  Stop scratching your head, and get the answers explained and at your finger tips.

VN:F [1.9.13_1145]
Rating: 8.2/10 (5 votes cast)
VN:F [1.9.13_1145]
Rating: +2 (from 4 votes)
Wood Go Kart Steering Basics

The wood go kart steering is based off a bogie mechanism where the front wheels are mounted to one axle and the main axle on the front pivots at a center point. The bogie concept is based on basically a wagon geometry however it is very efficient as far as vehicle dynamics are concerned, because it has a true arc path.

In order for the bogie system to maintain stability it must be constrained in the z-axis. What I mean by the z-axis is that the up and down motions of the axle system are not allowed to move. The side to side motions the x-y motions are allowed however the up and down motions are not allowed.

The reason for the constraint of the axle system is to keep it from suddenly jumping up in the air and causing an imbalance situation.

The main constraint with a bogie system is trying to get it to connect to the steering mechanism, such as a steering wheel. The basic way to make a bogie system move is through a cable system, where the steering wheel is turned and the cables are pulled in and retracted on one side and extended on the other side.

The rule of thumb is that when the steering system is set up, the ropes are wrapping when the steering wheel is turned to the left. The left bogie is pulling in in other words and so the steering drum is rotating counterclockwise and is pulling the rope in from the left side. The right side is correspondingly extending the same amount of rope that the left side is.

Angle of Steering Wheel Vs Angle of Bogie System.
Angle of Steering Wheel Vs Angle of Bogie System. This graph is important for choosing the diamter of the pulley diameter for the main steering system. Additionally, it gives you an idea of how much steering resistance to expect. As you can see the bogie system has this main issue when designing a wood go kart.

The relationship between the steering pulley diameter and the amount of steering wheel rotation is shown in the following graph. When you have a 2 inch diameter drum it takes approximately one full turn to get the full angling of the steering bogie system. This angling is approximately 26° to 30°. To get a 180° wrap or turn on the steering wheel the steering drum needs to be around 4 inches in diameter.
 
The downside to making the drum larger is that the forces double. So that at a 2 inch diameter drum the amount of force required to move one side of the steering wheel is 12 pounds. When the steering drum is increased to 4 inches the amount of force required to move the steering wheel is approximately 20 pounds or more.

If a larger steering drum is desired to restrict the steering wheel movement then friction reducing materials are required to make the bogie system not bind up.

In order to make the bogie system not bind the bogie can be lubricated with grease on the bottom rails of the frame. This will allow the bogies to slide back and forth with greased surface. If for whatever reason the grease is not working out as well as it could, the bottom frame rails can be coated with either a plastic material such as a polyethylene strip, or a stainless steel plate, or a copper sheet, or a galvanized piece of steel sheeting. It is important not to have any fasteners in the sliding surface areas otherwise the fasteners will catch and bind up the steering mechanism, more specifically the bogie mechanism will get bound up.

The bogie system itself needs to be coated with plastic or a steel material as well to reduce the friction between the two surfaces.  Grease should still be used regardless of whether or not you use steel or plastic so that the surfaces will slide easily.

Use of steel cables is appropriate, however, roller surfaces will be required to make the cables not bind up or cut through the wood frame work. Ropes can be used however a very strong expensive nylon style rope is recommended so that the rubbing action does not deteriorate the rope quickly.

It is recommended that the ropes be replaced every year.

Additionally the rope should be greased on every rubbing surface to make sure that the friction is reduced.

A rule of thumb about friction is that if any of these mechanisms are making noise such as squeaking noises then the surfaces should be greased so that the noises go away. Additionally the amount of force should be noticeably reduced when the surfaces are greased.

Tightening The Ropes

Tightening the ropes is accomplished by tensioning one side with a wrench. What essentially occurs is that the retention bolt becomes a mini tensioner device. The rope will be wrapped as the bolt is twisted. The compressive action of the bolt against the tube-washers will cause the rope to become blocked or bound in a tight position.

To tighten the ropes the steering mechanism is turned full to one side. Then the other side is tightened with the ratchet bolt mechanism until the slop in the mechanism is gone.

The actual diagrams for the rope layouts and the steering assembly are provided in the Wood Go Kart Building Series; and is explained in further details in the Wood Go Kart Video.

VN:F [1.9.13_1145]
Rating: 5.7/10 (3 votes cast)
VN:F [1.9.13_1145]
Rating: +1 (from 3 votes)
A DIY Home or School Project Well Worth Looking Into….

One thing I like about projects is that they are mini building programs. Ever onward, ever upward, step by step, plug along until you finally see the fantastic results.

Go Karts as you know are those types of projects, but as you well know too, once the go kart is done, then what? Well of course another go kart, or tweaks on the existing go kart. But today I am going to seek to expand your horizons into other areas.

One thing that go karts do is teach you mostly physics, mechanics and some minor electrical. I remember growing up and my Dad was saying that electronics was the next wave. In fact I had my choice, I could have gone into Mechanical Engineering or Electrical Engineering, or even become a Doctor…but I chose what I was comfortable with: Mechanical Engineering.

I chose Mechanical Engineering because it was something I could touch and feel. To be quite honest I never was introduced well to the field of Electrical Engineering, other than by those who said “It is really hard, very math based.”

Needless to say, by the time I was half way through college I could see I could probably do Electrical Engineering, but I probably would not be as happy there, so I stuck with the mechanical world.
But this article is about opening up new horizons. DIY Home School Projects are an excellent format for exposure to many high tech fields. The downside to conventional education is the 8 hour day restriction. Additionally, the restriction on free thinking or stepping outside the box is generally discouraged. With many public schools shrinking their budgets in the tech areas and deferring their tech courses to colleges, the actual ability to get your hands dirty and do some tech stuff will not come until it is time to get a full time paying job.

And that is the Catch Twenty Two (or bite in the rear you did not expect) the business owners are looking for experience, especially in these tech jobs.

So let’s be real where to you get tech experience? Where do you get your hands dirty?

In Projects.

Projects are the backbone to any career choice. Or more specifically can show people what you can do with your own two hands, or your two brain halves.

The go kart project when done right gives you an edge in a world of mechanical design. Also fundamental to go karts is engine repair and upgrade. (We don’t go much into that on this site, but I am planning on releasing a book on engine diagnostics. Whether it will exhaustive remains to be seen. )

The project I am proposing involves multiple disciplines, mechanical, computer, and electrical. The nice thing about the times we live in is that pioneers, ones that I went to school with, developed software and wrote programs that are extremely useful to a mechanical engineer. Additionally, the electrical engineers for the most part service the mechanical world providing electrical plug-in solutions to a complicated mechanical problem.

For example an electrical engineer may provide a cam actuation package that involves servo motors and other electronic goodies versus a complicate cam profile that is fixed. You may not understand that last comment, “fixed cam profile.” But the best a mechanical world can muster is a one stab approximated solution, whereas the electrical world applied to the mechanical world opens the world of variables to the engineer.

With a push of the button a cam profile on a starving engine can be changed with a network of electrical sensors and computer mapping programs, or even better yet get real time data and give the best solution to the combustion problem at that moment.

What does that mean to the mechanical world? More Power! More speed for less weight. Moooore!

Okay just what is this project? The project involves like I said is multidiscipline but is yet in the young person’s grasp.

Okay what is it?

Well I can tell you what it isn’t…

It isn’t boring, it isn’t going to sit in the corner and never be used. It isn’t a go kart, but it could make go kart parts, perhaps….

Alright I almost let the cat out of the bag right there…

It is a Do It Yourself 3d-printer. There are about three different manufacturers of ready to build 3-d printers. They can be either ready built or they can be assembled by yourself.

A 3-D printer is a printer that instead of just printing a sheet of paper with a .0001 inch of material (such as ink on the paper) prints over and over again and starts building off of the paper and makes a stack of ink. Typically a 3d printer uses a nozzle or syringe to dispense material down and then build upon that material to make a 3d object such as a human skull or a carburetor intake for a go kart, or better yet supercharger component for the racing enthusiast.

Another way to look at 3-d printer is that they are the inverse of CNC machines. Instead of starting with a chunk of material and wittling it into a shape like a CNC machine, the 3d printer builds up material and makes the shape at the first.

These projects are not for the timid, or those that give up easily. These printers are projects that tax the mechanical genius to be efficient, the computer geek to use his skills and the electrical guru to come up with something better.

I have been watching this DIY 3d Printer field for a while now. What has spurned this urgency for this field is that though CNC machining is powerful, I believe 3d Printing has more power to it.

From a set up stand point there really is none, other than turning the printing on. With a CNC mill you have to be very careful and have everything homed in and placed carefully. Additionally the CNC mill is noisy and messy, the 3d printer is much, much quieter and there is less dust and waste.

So our project is going to be Project 3d Printer and we will see where it leads us.

You may be wondering why the change in focus? This is a go kart site. Unless you think I have lost focus fret not….remember what you can do to go karts? Supercharge them? Fuel inject them…the 3d printer can get us closer to that goal in less time that a CNC machine, because we can make mistakes without fretting. Do a redo overnight….

The next article will be comparing the different types of 3-d Printers and the directions that a DIY 3-D printer enthusiast can go with relatively low cost….

VN:F [1.9.13_1145]
Rating: 10.0/10 (1 vote cast)
VN:F [1.9.13_1145]
Rating: +1 (from 1 vote)
Making a Free Wheeling Coaster Brake Drive For a Pedal Go Kart

 

I have been racking my brain on how to develop a rear coaster brake system for a pedal go kart for a while now and it dawned on me the other day that I was making it too complicated.

It does however require two bicycle rear ends to complete the task but in reality it is quite simple.

The way it works is that the coaster brake rear end from one bicycle is made to drive a solid drive axel.

Coaster Brake Assembly with spokes removed

Coaster Brake Assembly with spokes removed

The wheel  hub will need to be de-spoked.   A sprocket will then need to be welded onto the wheel hub.  This sprocket then will drive the rear axle.

The lower rear section of the bicycle should be retained and mounted into the framework  the go kart.   It is important to maintain a workable drive ratio, and typically 1 to 1 drive will work best for the weight involved on the cart.

Ideally the most robust drive uses the bike frame work (cut back of course) because it has metal frame work.  If you cannot afford to use the bike frame work, then metal plates are the next best option.  The metal plates are fixed into the frame work using sheet metal screws or lag screws.

Free Wheel System Put Into Pedal Go Kart System. The rear (grey system) sprocket is fixed to the main drive shaft.

When using a bike coaster system, a basic understanding is needed.  The way it works is that the hub drives the wheel and the inside of the hub acts as brake.  So in action (as many of us grew up with) the pedals cause the bike hub to turn in one direction, coast in the other and then brake when the pedals are reversed.

 

The important note in all this is that there is a brake arm that hangs off the opposite end of the drive hub.  This brake arm needs to be fixed to the frame work; otherwise the brake will not work.  What will occur if the brake arm is not fixed is that the brake arm will tend to rotate when the brake is applied.  So fixing it is important.

As you have been guessing, at least two bike systems are needed to make this drive system work.  The reason I say that, is because the drive ratio of 1 to 1 is needed, and in order to attain this a large sprocket in the rear is needed.  This large sprocket will be removed from a pedal system off of another similar bike.  Then this sprocket will be attached to the smaller drive sprocket on the coaster brake system.  Because of the forces associated with the pedal go kart (mainly how heavy it is)  a ratio of 1 to 1 or even higher is needed. 

 
VN:F [1.9.13_1145]
Rating: 10.0/10 (1 vote cast)
VN:F [1.9.13_1145]
Rating: 0 (from 0 votes)
The Case of the Bouncing Quitting Go Kart: Carburetor Grief

You may have run into this or you may run into this where you are riding your go kart on a bumpy, gravely driveway and suddenly the go kart stops running properly. It just up and quits.

“Why would the go kart suddenly quit?” Is the question in your mind and “What would cause the go kart engine to stop running, since obviously nothing touched it?”

 What you will run into is that when you are riding a go kart on a rough surface the engine will be bounced up and down and in this ” bouncing up and down” the carburetor is jostled up and down. The carburetor inside has a bowl, and inside the bowl is a float that floats literally on gasoline. When the go kart is bounced up and down the float can be bounced up or down and typically will jammed in the needle valve in its seat.  It literally jams the needle valve into its seat and the only way to get it released is to jostle it again.

 The jostling effect usually comes when you start up the engine in choke it because that’s all that will that will cause the engine to run. It will run almost indefinitely and that’s a symptom that you jammed needle valve. Typically we will frantically start adjusting needle jets trying to get things to work better, just so we can limp home. We will discover however that it is probably the float inside the carburetor causing all the grief.

 If this continues to be a problem you have an alternative plan, and that is to buy a new diaphragm carburetor, or find a new carburetor that has no float in it. You see the float is designed to regulate the gas requirements for the engine. A “floated” carburetor is designed to run on a level surface not a surface that is a hill or surface that is constantly being bumped. The diaphragm carburetor however is used on things that are bounced around a lot and change angle positions a lot. For instance they are found in weed wackers and chainsaws. The best way to find a diaphragm carburetor is to go to a local small engine repair store and purchase yourself a diaphragm carburetor that will meet the CFM requirements for your engine. Also you can shop on eBay and find some second-hand used diaphragm carburetors. You need to make sure that you get the right size carburetor otherwise you will be starving your engine for its gas requirement.

And finally the engines that are most susceptible to this particular ailment are engines I have bowl-float combinations. Some of the manufacturers have come up with rubber tipped needle valves which help solve this problem, however you will discover that even going up hills can be an issue so in case you’re wondering why your go kart is quitting after you’ve been running it over bumps and or going up hills, it is because of this float needle jamming issue.

VN:F [1.9.13_1145]
Rating: 7.6/10 (5 votes cast)
VN:F [1.9.13_1145]
Rating: +5 (from 5 votes)
Goofy Twisted Belt Drive That Just Don’t Work On a Go Kart
Proposed Twisted Belt Drive For a Go Kart Drive Line

This is a typical proposed simple drive line for a vertical engine. This article will discuss why this system will not work. Put simply the ratio is way wrong and the belt will smoke.

Question: Can a simple pulley and twisted belt drive system work on a go kart for a drive system?

Answer: No, the belt will slip, and there will be tracking problems.
The answer seems simple enough, the belts slipping and belt tracking, but there is more than meets the eye here.

First off, if we run through the calculations, presented in our Go Kart Building 203 course you will discover that the following drive system will smoke the clutch.
Example: Typical Go Kart Drive Requirements
– 1.75 inch Drive Pulley
– 5 hp Engine
– 7.5 Inch Drive Pulley
– 12 Inch Wheel
– 325 lb go kart

5 Hp Chart From Go Kart Building 203 Course.  The Vertical Line is the Smoke or No Smoke Line.  If you are to the right of the line, the clutch will start to grab more, to the left the go kart will go backwards and burn up clutches and belts.  It may even stall the engine.

This chart is from the Go Kart Building 203 Course. The chart is showing the profile of a 5 hp 300 lb go kart drive line system. To the far left the clutch will smoke and the go kart will go backwards. The engine may even stall or quit. The vertical line shown is where the clutch will start to grab and the go kart will go forwards, probably with a little help though. The farther to the right the better the accelleration and less clutch or belt problems.

The following chart shows that the go kart drive line characteristics. First it is showing that the ratio of 9:1 will make the belt smoke and the engine to stall. The go kart will not move very well without a push at any ratio below 9:1. Secondly, the ratio must be above at least 10 or even 11:1 to get a decent running go kart that is not constantly smoking belts.
What you will discover is that you will not be able to get a pulley large enough to satisfy the over all ratio. You will need to get a pulley that is larger than the rear wheel. In fact, just to get to the smoking point of the belt, you will need to have a pulley that is 15.75 inches in diameter.
So you will be forced to deal with drive reduction alternatives at the outset, just to get the go kart to drive.
So as you can see, I call it a “goofy twisted belt drive” because it is not realistic, it will smoke the belts, and not allow the go kart to go anywhere anyway. It may be simple, but is does not take into account the fact that the engine and belt combination will not work together.

In case you are thinking I am saying that twisted belt drives are not plausible, I am not, I am just saying that this particular drive line is not going to work.

In the Go Kart Building 202 course we go into details on how to use a vertical engine, while not using this “goofy twisted belt drive layout” but using a system that works very well, and is quite durable.
As a side note: there are two other major issues with the layout simple layout proposed, first when using a small pulley and a large pulley in a twisted belt drive layout is tracking. The belt has a hard time finding the small belt, especially when the engine drive is slacked, the belt tends to hop the smaller pulley. And vice versa, when the engine is romped on, the belt tend to jump the larger pulley on the slack side, as the belt is suddenly stretched and slacked. The slack section tends to hop out of the larger pulley.

And finally, the smaller pullies generate a lot of heat energy when high horsepower is used. The small pulley cannot dissipate the heat readily and tends to burn the belt, or even melt the belt. It is not uncommon on our wood go karts for example to burn through a belt in a summer. Belt drives work best if the belt is just transferring power smoothly and not being required to be a clutch, or have sudden on and off engagements.
An example of belts being used for extended periods of time are lawnmower deck belts. As long as the belt is just transferring load, and not being required to slip and then engage, the system will work pretty well.

Again, in our Go Kart Building 202 course we have a rock solid drive line that will not break down easily and requires minimum maintenance. That means, nothing is overheating or breaking down in the system.

VN:F [1.9.13_1145]
Rating: 6.8/10 (4 votes cast)
VN:F [1.9.13_1145]
Rating: 0 (from 0 votes)
Go Kart Building 203: Climbing Hills Program Explaination

The Go Kart Drive Line Program

(This is an exerpt from the Go Kart Building 203 Book on the Drive Line Program)

After having gone through all these calculations you may be anxious to get some answers quicker.  The go kart program will help with that.  Though it is not as exhaustive as the graphs and formulas it will get you answers at the click of a mouse.

The go kart program is broken down into the following areas:

Inputs section for the program.  The Frame Weight, Person Weight ect...

Inputs section for the program. The Frame Weight, Person Weight, Engine Hp, Max Engine RPM, Rated Rpm and Clutch Engagement RPM

– Go Kart Specifications
– Go Kart Engine
– Go Kart Clutch
– Go Kart Drive Line
– Go Kart Calculation
– Go Kart Results
– Go Kart Recommendation

 The go kart specifications section is gathering information about the weight of the go kart and the weight of the person. 

The go kart engine section is gather information about the engine horsepower,  the horsepower rating rpm, maximum rpm and the clutch engagement rpm.  The default setting for the hp is a 5hp@3600 rpms.  The torque engagement rpm is 2200 rpm, which has been validated by in house testing.

 

 

The Drive Line Section

Go Kart Drive Line System Info, starting with chain pitch, clutch sprocket diameter, Jack Shaft 1 Sprocket, Jackshaft 2 Sprocket, Final Drive Sprocket and Tire Diameter

Go Kart Drive Line System Info, starting with chain pitch, clutch sprocket diameter, Jack Shaft 1 Sprocket, Jackshaft 2 Sprocket, Final Drive Sprocket and Tire Diameter

The drive line section is designed to take into account a jack shaft system.  The program is by default set up so the Jack Shaft system is ignored, or it is neutral in the calculation by making the input and output sprockets the same size.

The drive section is composed first of the chain pitch (this affects the diameters of the sprockets), second the clutch drive sprocket, then the J1 (or Jackshaft 1 sprocket) , the J2 (or Jackshaft 2 sprocket  which is typically a very small sprocket) and finally the Tire Diameter.

 

 

 

 

 

Calculations Section:  Starting with Total Weight, Ratio, Chain Tension of Jackshaft 1 and Jackshaft 2, Max MPH, Clutch Status, Hill Climbing Status, Accelleration Up Hill, Accelleration Flat....

Calculations Section: Starting with Total Weight, Ratio, Chain Tension of Jackshaft 1 and Jackshaft 2, Max MPH, Clutch Torque, Clutch Status, Hill Climbing Status, Accelleration Up Hill, Accelleration Flat and whether the tires spun or gripped.

The Calculations Section

The calculations section shows the essential data needed to determine if the drive system is going to work or not.

First the total weight is important for go kart performance; the program totals that up for you.  Second the OVERALL ratio is calculated, along with the chain tensions on both the jackshaft systems.  These are labeled Tension1 and Tension 2.  This data is needed to determine if the chain is going to snap or not  (unfortunately the program does not tell you if you chain is overstressed or not…yet)

Third the program also

calculates the maximum MPH of the gokart based on maximum engine rpms. Fourth it calculates the clutch status and clutch torque.  The Hill climbing status is important for go karters who are seeking to go off road. 
At the bottom of the page the program gives recommendations.  Because the hill angle was set at 10 degrees the program is recommending changes to get the go kart to climb the hill.  The overall ratio is key to this recommendation.

As you can see this program run was not successful for climbing hills.  The go kart in fact would go backwards down the hill, which is just the opposite of what we are trying to achieve. 

Upgrading The Drive System To Handle Hills: How It’s Done

In order to get the go kart to climb the hill, the overall ratio needs to be updated. 

To get  that to happen, the large sprocket on the jackshaft needs to be made larger.  So the value of 30 teeth was put into the program and as you can see the overall ratio was upgraded and the program settled down told you that you the go kart can climb hills now!

Jack Shaft Inputs.  Jack Shaft 1 is the larger driven sprocket, Jackshaft 2 is the driven smaller sprocket

Jack Shaft Inputs. Jack Shaft 1 is the larger driven sprocket, Jackshaft 2 is the driven smaller sprocket

Recalculated to climb hills

Recalculated to climb hills

 

 

 

 

 

 

 

 

 

 

 

 
Flat Landers Go Kart Calculations

Not all of us want to climb hills, so the program has the option of changing the hill angle value to 0 (zero) degrees.

(The program by default is set up for climbing hills at 10 degrees)

 When the angle is changed to Zero, the program will calculate the performance of the go kart assuming no hill. 

The recommendation section will give a drive system that is designed around the optimum accelleration of ¼ g or 8 ft/s2 .

 

Hill Angle Option can be changed to zero degrees for Flat Surface Calcs

Hill Angle Option can be changed to zero degrees for Flat Surface Calcs


Flat Surface Calculation

Flat Surface Calculation

VN:F [1.9.13_1145]
Rating: 4.0/10 (3 votes cast)
VN:F [1.9.13_1145]
Rating: -1 (from 1 vote)
Go Kart Guru A 2010 a Year in Review + 8 Tips For Your Go Kart Project

Well it was a short year. Things happened way too fast, and projects went way to slow and uncompleted.

It is going on two years now and the dual seater go kart is not complete. Which is frustrating, but necessary seeing we are videoing the whole process. Our ambitious goal was to make a two seater go kart out of an old lawn mower, using all the components from the lawn mower.

Additionally, we are using the e-books that the Go Kart Guru has on the web site. We actually have gotten pretty far. We are putting the seat on the go kart, making it so the seat can be easily removed and placed. Now that the go kart is sitting in the garage, we removed the seats so that winter varmints are not infesting the seat, and cats ruining it.

Come this spring we should be getting the first test drive in.  That will be exciting.

As far as new products are concerned we are coming out with a printed version of all the books in one big monster volume.  It is about 400 pages of material.  That will be released at the end of the month.

Additionally, we are coming out with a new book that is full of charts that show how to set up a drive system for a go kart ranging from 5 to 18 hp and 200 to 500 lbs in weight. There are two ways to set up your go kart, one for driving on level surfaces, and two for climbing hills.

There was an overwhelming amount of people who were emailing and asking why their clutch was smoking and how to set their go kart up so it could climb hills and not smoke the clutch. I used these charts frequently in email responses to help out.  I figured it is high time I just put together a book that will address all the drive systems questions.

The 201 Drive systems book is more than sufficient to get the rive system set up properly but it lacks in some areas, especially when a clutch will smoke. So this new drives systems book shows when the clutch will smoke for a whole wide variety of weights and horsepower set ups.

Later this month we will be releasing this book. I am considering putting together movies that will accompany the book to help explain how to use the charts better.

Last year the goal was to put together a curriculum for shop classes. We are really close to having this shop class package put together. It is pretty involved, includes videos and tests. So we are about really close to getting that released as well.

Keep asking questions they help fuel more helpful ideas on our end.

I hate putting together a newsletter without any helpful advise so here are some tips:

8  Tips to Help In Your Go Kart Project

Tip #1  Frame Design: When making your frame use 1×1 tubing with at least 1/8th wall for maximum strength.
Tip #2  Brake System: A live axel system is actually simpler than a one wheel drive system. As a result disc brake system is the most readily available and cost effective. Remember to leave the disc so that it can float, other wize it will bind and wear out your brake system.
Tip #3  Throttle System: When setting up your throttle be sure to have a positive return in the pedal, but most especially at the carb linkage. This is more a safety issue, so that when the pedal is released (or the cable breaks from the pedal) the throttle is in idle or in the slowest speed.
Tip #4  Drive System Layout: The simplest and most cost effective drive system is the centrifugal clutch system. A rule of thumb is to have the rear sprocket be at least 85% of the diameter of the rear wheel.
Tip #5  Steering System: The common mistake in drive systems is to have the linkages around the foot pedals. In other words, when the gas pedal is full pushed down it hits the steering linkages cause a bind up on the steering. This is a dangerous condition. Additionally, the steering is usually not set up to account for the 50/50 weight distribution, so the go kart tends to go straight. Typically the steering and wheels are behind the foot pedals for proper weight distribution.
Tip #6  Tires: Low cost tires that are found at retails stores on push dollies or cheap wagons can be used, however, they do not have the proper rubber construction to withstand driving conditions and will wear out very quickly. Beware of cheap rims they can rip loose of the hubs and fail prematurely.
Tip #7   Safety: Always wear safety equipment such as gloves and a helmut. Smaller drivers should wear chest protection, such as a ribtech unit, so that when a collision occurs they do not hurt their chests or have internal organ damage. Flipping a go kart is the most traumatic and most preventable. Good driving habits and lower speeds are encouraged for younger drivers. Dis-allow go kart drivers who will not observe safety and be sure to educate all drivers about safety.
Tip #8  Where to Drive: Driving karts on the street is against the law. You will be arrested and get a ticket. Also, there are serious insurance issues if an accident does occur. Sadly the news has some occurance where somebody has entered the roadway and gotten killed while riding their go kart. Go Karts are only legal on your property. A large open area is recommended: trees, cars and pedestrians are major hazards to go kart driving.

VN:F [1.9.13_1145]
Rating: 9.0/10 (1 vote cast)
VN:F [1.9.13_1145]
Rating: 0 (from 0 votes)

Copyright ©2008 - 2017 Gamble Industries LLC - All Rights Reserved