These are two questions most people have when trying to decide which TigerStop material pusher to buy. The answer is, like almost everything in life, “It depends!” To better grasp what you can do with a TigerStop product, you need to understand some basic physics concepts, Inertia, Thrust, Coefficient of Friction, Acceleration, Duty Cycle and most importantly, String Theory. Actually, we are joking about the String Theory part but it doesn't hurt to brush up anyway!
Inertia is the measure of a body's resistance to changes in momentum or the energy inherent in a mass that is either moving or not moving. Whereas work is the energy expended to change the motion of any mass, either to accelerate it from a standing position, bring it to rest, or change its speed or direction. All of these changes to the inertia of an object require the expenditure of energy. Inertial mass is the combination of the ‘at rest mass’ or weight of an object coupled with its motion. A good way to look at it is the example of a hammer and nail. A hammer may weigh only 12 ounces, about the same as a small loaf of bread. If you set the hammer head on top of a nail it would not sink the nail into a board. But when you accelerate the hammer and then stop it suddenly on the head of the nail, the inertial mass is great enough to drive the nail into the board. An extreme example could be, to take a feather and accelerate it to the speed of light in 0 time would require more energy than exists in the entire universe.
Thrust is pretty simple. It's the force exerted in a straight line. Imagine holding your arm out in front of you and someone taking their hand and pushing your arm back toward your body. That's thrust.
Coefficient of Friction
There are two types of friction: static friction and kinetic friction. Friction is the resistance of one object rubbing or sitting on another. Generally, if a piece of material weighs one pound on a surface and the amount of energy necessary to move it across that surface after it is set into motion is a force of one pound, the coefficient of friction is one. If it takes less than one pound, say ½ pound, the coefficient is 0.5. If it takes two pounds then its coefficient of friction is 2, and so forth. Static friction has a larger coefficient of friction than kinetic friction coefficient.
The coefficient of friction is important to understand when determining the type of friction your material will have when being fed through a cutting application for example. It's why roller tables come in so handy to seamlessly feed material at an accelerated rate (we'll get to acceleration next) when applicable, and why friction tables are a safe bet when you want to slow material down before it is sawn.
This is the rate at which you take an object from not moving to moving at a target speed. A handy rule of thumb is, to double the speed of acceleration you must square the energy input. If it takes 300 watts of power to accelerate a five pound mass to 15 inches per second speed, it will take 90,000 watts of power to accelerate it over the same distance to 30 inches per second speed.
This is pretty much just what it sounds like. It refers to how long in a given period the machine is operating versus being at rest. Think about carrying a backpack up a steep hill. If you go very slowly you can most likely climb the hill without stopping- that’s a 100% duty cycle. If you sprint up the hill you may only be able to go 25% of the way up the hill before you have to stop and rest. Let’s say you sprinted one minute and then rested nine minutes to catch your breath. You would then be working at a 10% duty cycle. Positioners are just the same. If you want the machine to be running backwards and forwards constantly, the load you can move is going to be much less than if you need it to work only 10% of the time.
How Fast Can You Go?
Now that you have mastered Physics 101, back to the issue of how much weight a TigerStop can push and how fast. Well, what does your object weigh? How fast do you want to move it? How fast do you want to accelerate it? What is the coefficient of friction? Is your mass moving toward the positioner or away? Is the positioner impacting the mass or is the mass positioned against the foot of the positioner? These are all important questions to ponder.
Here are some rules of thumb
When determining what type of equipment you will need to push or feed material through your application of choice, whether it be a saw, drill, press, you name it, here are a few points to take into consideration.
- If you are moving heavy materials, you will need to accelerate much more slowly.
- If your coefficient of friction is high you will not be able to push very fast- most likely you will move very slowly.
- Use a gentle touch, a spring buffer, or other method to load material. Think in terms of a 30 foot steel beam moving at 10 inches per second striking a fixed object. Would you want to put your pinky between it and the fixed object? Of course not! You would instinctively know that the inertial mass of the beam of steel would squash your finger flat, handy on hot days as a fan but exquisitely painful. When you run a heavy piece of material into the pusher at any speed the amount of energy required to hold position becomes tremendous.
- Use roller tables as your mass gets greater or if you have high coefficients of friction like green lumber running on solid steel tables.
- If your duty cycle is low you can push more weight; if it is high you will have to push much less.
TigerStop’s specifications are related to thrust output. Weight and speed are the maximums in optimal conditions. The heavier the object, the slower you will move, and reciprocally the lighter, the faster you will be able to go. Our top speeds are return speeds with no load. Our maximum thrust is at very slow speeds and very slow acceleration.
TigerStop offers a wide range of material feeder systems. If you are pushing extremely substantial loads you don't have to compromise on speed entirely. For instance, the TigerTurbo system pushes loads of up to 840 pounds at 180 feet per minute. But maybe you need a system that's even more heavy duty? TigerStop has a conveniently named tool called the HeavyDuty 2, which can feed material up to 2,100 pounds with repeatable accuracy shift after shift.
To determine what kind of material pusher is truly best for your application, visit the TigerStop product selector or tune in to to the second installment, Material Pusher 102, coming up shortly!