Steering Systems, What Is It All About?
When we look at a go kart, and we wonder, (especially when we turn the steering wheel and look down at all that linkage) “What in the world is happening down there?” It is not that frightful. But, there are some things that we need to discuss and that need to be understood.
First of all their two types of steering systems:
- Wagon Style Steering System,
- Steering Knuckle System.
The wagon style system is where the wheels are mounted on the single axle and the axle is pivoted in the middle. And the wheels rotate, if you will, or run together.
The steering knuckles system is where the axles themselves, which are mounted on a knuckles, out and away from the go kart, and they actually rotate around these pivots, and cause the wheels to turn.
There actually is a relationship in the wheels to a turned center, and there is a positioning system on these steering knuckles which is important for steering. It is more important when you get into heavier vehicles. The lighter vehicles it is not as important.
The major discussion here is going to be on the steering knuckle system. We are going to bypass the wagon style system, because that is primarily used on wood go karts, there are not other options but the wagon style system, which in passing is just inherently unstable. It is hard to control, there is a lot of attention required to maintain position when you are driving that. It is actually unstable and harder to maintain, you have to have a very good sense of control, when you are using that type of system. The wagon style system is also unstable on corners because you are demanding that the pivot actually resist twisting as the go kart cornering forces are pulling the go kart over in a rolling fashion, and the pivot can not hold it very well, and you tend to actually bend that area, and can have a premature flip. The other issue is that it is hard to maintain when you are sitting on it.
The steering knuckle system can be made for wood go karts, I have seen it done, but it is not as precise that you can put together with a metal system. Basically what you would use would be a hinge. You would bolt the tire through the hinge system, and then the wheels do not actually follow the knuckle per se' , but they mimic a knuckle system. Again it is not as precise. It works okay for lighter applications, but I would not recommend it for any motor powered applications, as in go-karts.
If you are seriously going to make a go kart, I would highly recommend that you go to the steering knuckle system.
That said; let us discuss in further details the steering knuckle system.
There are a couple of things that we need to identify: there is a turn center, and vehicle radius turn centers.
The hardest part to envision here is that the inside wheel is trying to spin slower that the outside wheel. And that by definition means that he radius of turning for the inside wheel is going to be smaller than the outside wheels turning radius. The best way to explain this is:
If you were sitting on a merry-go-round. If you get in a merry-go-round and it is spinning like it would at a park with kids on it. And you were to go to the center you would notice that it is not spinning as fast. You will feel less pulling energy. But as you go to the out side you will feel yourself being yanked out. The reason for that is you are actually feeling more velocity or energy, if you will, more speed on the outside. Because everything is spinning the same, but as you actually move radially out on the circle, you actually will be spinning faster to maintain the same position.
And that is the same thing that is happening with a go-kart when it is turning, the outside wheels will spin faster than the inside wheels in a turn. (Just as a side note: the differential on a car is designed to accommodate the different speeds of the outside verses the inside wheel. So that the outside wheel actually spins faster than the inside wheel. If you ever do some noticing, and are making a turn in a car, and you stomp on the gas in the car, the inside wheel is the one that is going to spin, it going to burn rubber.)
On a go-kart however, because the small turn radius of it, it is just as easy to expend rubber. In other words the inside tire will be going in the same speed in turning as the outside wheel, and you will cause the tire to spin or loose rubber when you are turning the go-kart. That is where the wear comes from. It is primarily coming from corners. Because the outside wheel is actually spinning faster than the inside wheel would like to go)
Keeping that in mind, the steering mechanism on a go-kart needs to be accommodating that. To have maximized effectiveness and cornering. Now there isn't a whole lot to worry about when you are doing that, in your mechanism you design that. And you can eye-ball it. I actually, if you were beginner, I would not worry about it. I would just let it happen. Just put your system together and orchestrate steering system so should be the way should be and you should be fine.
When needed to turn of the knuckles hanging down this is fine. We'll later get into how you actually actually do steering systems. There are above and beneath systems for steering or forward and backward systems.
The Turning Point
To actually get a tire to turn well or easily, you need to turn around the turning point. If you were to watching a wheel as you're turning it, the knuckles will actually cause the wheel to turn forward beyond the knuckle if you will. And the intent of the design, because when you turn the wheel you actually went to turn around the center of the tire. When you think about that there is less scrubbing action it is a lot easier to deal with. If you were to do some examining of wheels on cars, and how they set them up, you will see the tires will actually spin around their center. And in doing so, it is easier on the tires, it is easier on the suspension system, it is easier on the drive line, it is easier to steer for that matter.
Four wheel drive trucks have difficulty and actually having that happen, they have to do some mental gymnastics, if you will, to get to that ideal positioning. If you look at trucks for instance they have the same issues. What they will do is they will make the hub stick out a lot farther because they are trying to get the turn’s center to be right at the center of the tire.
Now there is another issue, a third issue, and that is the incline of the turning. And that has to do with the forces that the vehicle encounters during turning. If you lean the system back towards you, the steering will be more advantageous, more aggressive. Also it turns to your advantage, the vehicle has less affect over the steering wheel and you have more over all command of the steering wheel than the vehicle does on you. That is the purpose of it.
Now it is incorrect to design a vehicle so that the wheels will turn not ideally on the turn center. It just makes it harder on the turning system itself; you'll be fighting the steering wheel more to get things to occur. So you will have to keep that in mind, if you are designing it with really big tires,, that if you have big tires and big heavy, vehicle, and your steering system is not designed correctly, you will be fighting it. And it will not be an enjoyable to ride.
And ways to get around that would be to have a rack and pinion steering, so that you actually have a steering system, if you will, which helps to give you some mechanical advantage. In other words, it makes the resistance of the turning less. It makes it easier to steer.
The way to get around that is to sign your steering system correctly, and then you're not fighting it as much. It does take some ingenuity, and design layout for that to occur.
Now engineers devote their lives to design a suspension systems for cars that is all they do. So to expect yourself to design something right off the bat, it is kind of a lot to expect. One way to get around that is to buy someone's plans where they have performed all those calculations, and they have done it already. Or you can use the rough guidelines I've talked about, you can do some rough layouts, try to figure out a little bit. In the "How To Build A Go Kart.pdf" there are further details on how to design a steering systems. This is a great resource, especially for those who want to do it right.
Now the steering system itself, we had talked about, how you activate and move the wheels back on forth. Now they are actually levers that are put onto each one of the steering knuckles. And the longer the lever, the better the mechanical advantage. However, the longer the lever, the more throw is required. And of the more throw that is required, then you are going to have an expensive type steering system. So what really you are going to end up with is equal length systems on your steering and on your steering knuckles. They are going to be roughly about the same radial distances, and what you are basically putting together as a parallelogram system. So that you basically have an equivalent amount of movement in the steering wheel and in the wheel as they are turning.
The inherit designs that I have on my go karts have the inside wheels turning more, as the outside wheels turning less. It has to do with the offset it is similar to what we call a four bar linkage. The layout of that you can roughly two on a piece of paper or on a mechanical design program to figure out what those radial turn relationships are.
But it is not wrong to have both tie rod ends joining at the same point. It is not wrong and is not going to malfunction or not steer. It is more ideal to have them offset, as I have in my plans. It is just a four bar linkages design it works better. It has been proven out. A lot of your race go-kart designs use this offset for bar linkage design.
Figure: Outside Wheel Has Less of an angle (15 deg) where as the inside wheel has a steeper angle (19 deg). Notice the two different radial turning paths for each tire. The outside has a larger radius and the inside a smaller radius. The outside must go faster to keep up with the inside tire.
Now, the question as to go above or below the steering system? I prefer, to go below. And the reason for that is, your feet can get above the steering mechanism, they're not getting going to get all tangled up in it. I have seen it were the steering mechanism is above, an unfortunately your feet get tangled up in your socks and can get tied up in that. So, prefer to have it, down below from a packaging standpoint.
One thing to keep in mind, especially if you are using a suspension, the relationship of the steering tie rod ends can change when the suspension moves. And what you will find is if you do not design your steering system correctly, (in other words if you do not put center lines of your steering tie rod ends right in the center, as in a parallelogram system) what will happen is when you hit a bump and wheel goes up, your wheel will either move out or in. It will change the relationship of the wheels, and they will flop back and forth. That can be very dangerous when you are driving. So keep that in mind when you are designing your suspension system in the front. You need to have the relationship between the tie rod ends and the center distance of the steering system correct.
You need to have the tie rods in a neutral position as the suspension moves. So that the wheels themselves are not turning when the suspension moves. That is pretty important. If you look at a car, and examine its suspension system. You'll get the idea that the tie rod ends and their relationship to the suspension does not move. They maintain a central a position and that is very important for, obviously tracking. Imagine if you were to put a load, a front load, with someone who is heavier than you, and all the sudden the tracking of the wheels is off because the suspension tie rod ends relationship is not neutralized or correct.
The steering knuckle system is by far the most reliable, most robust and most controllable system that go carts use, and cars use for that matter. As far as the steering knuckle designs are concerned, there's a whole host of different ways holding onto steering knuckles.
You can use the tube with a very large bolt welded to the tube, then you surrounded with a C-channel. You will then run a bolt through both the C-Channel and the tube. On the tube itself you have welded a radial arm. On the arm itself you gusset it, so that it maintains twisting motions when you hit bumps and so on. But also on the arm have a hole, and you mount your tie rod to that. And then the tie rod mount over to the steering system. The steering system itself obviously, goes out towards the passenger. And it basically is a rod with a radial arm on it. And then you bolt on to the radial arm with your tie rod end.
Tie rods are basically a moving joint that has a ball in it. The tie rod can move and about 360° in motion in two planes. You can move the rod back and forth. It is designed to transfer the load from the steering system to the steering knuckle. You can purchase those steering rod ends at any go-kart supply house.
There different kinds you can use. There is a rod with a thread, and you take the steering tie rod end and just thread it on. One important thing to keep in mind is that the rod itself can become loose. So you want everything to be tight. So what I do is take a tie rod, and that I take a tie rod end and then I take a nut and I jam nut on to the tie rod end. This keeps everything nice and tight. It is very important that all joints be relatively tight and not loose, because vibration will start to make things fail and bend and wallow out. And then you're steering system will be off, and will have lots of vibration. Even if you have the very large motor and engine vibrates a lot, as long as your steering system is pretty tight you will be safe. You may have a vibration that comes up the steering column, but that will be ok as long as you have everything tight. If things are loose then you're steering knuckles will wallow out. Your tires will wear out sooner.
Now one word on adjustment of your steering system. I have noted that some go-kart places denote that you should have your wheels forward 1°. They basically are towing them in.
And the reasoning for that is: that when the go-kart goes forward the slop is taken up, and all wheels will be parallel. So it is a good idea to put at least 1° forward. It will wallow itself out when you start driving. It also has to do with the amount of bite you get when you steer. Additional information about the steering system is available in the suspension area.
Great Birthday Present: The Father and Son Wood Go Kart Project