A.R.& E.


First Quality ~ First Time
Apparatus Repair & Engineering, Inc.
Hagerstown, MD  21740



Read Me First




Reducers WON'T help you lose WEIGHT!!

Reducers are more properly identified as "Speed Reducers" in that they do just that.... they reduce the speed coming into the device to a lower speed on the output by means of gears inside the housing.

There are a number of different types and brands of speed reducers and each one has it's particular applications to serve.

The major types of speed reducers are listed below with links to a description and some helpful information on applications and uses.

Keep in mind also, that a speed reducer is also a TORQUE MULTIPLIER! The laws of physics apply to speed reducers and the formula indicates that torque will be multiplied by the amount of the speed reduction. So for ease of calculations, if you start out with a 1HP motor that is rotating at an arbitrary 1800RPM it produces 3 lb-ft of torque. If that 1HP motor is connected to a Speed Reducer whose ratio is 10:1, the output torque will be 30 lb-ft of torque. You can check the formula for torque on our formula page and compare some of your own calculations to see how dramatic the results actually are.

Worm Gear Speed Reducers - This is one of the most popular speed reducers in use today. Due to changes in manufacturing technologies and materials, these little workhorses have become smaller, more compact, more efficient, and are almost a commodity. Everybody's got one and everybody's is better than everybody else! Because of the way the second gear WORM WHEEL mates with the WORM GEAR, this reducer is always a RIGHT ANGLE REDUCER.

In reality, their design is rather simple. The input shaft has a WORM gear cut into it's body. This worm gear is usually made of hardened steel and based on the ratio desired in the reduction, the worm may be finely cut or rather coarse. The design of the worm gear being a "screw like" device, as it is turned, it's mating gear is "pushed" around and since it is attached to the output shaft, the output shaft is also turned.

Common ratios of these devices is in the range from 5:1 to 60:1 with some exceptions. Manufacturers differ, but most have ratios that follow 5:1, 10:1, 15:1, 20:1, 30:1, 40:1, 50:1 and 60:1. Due to those wide ranges of ratios, the user must either handle minute differences in desired output speeds with an additional speed ratio device. This can be placed on the output like a belt and sheave or chain and sprocket, but that means this second ratio device MUST transmit the full torque that is being produced by the reducer. For this reason, most users who need a different output speed than can be had with just the reducer, will change the INPUT speed to the proper amount so that when it arrives at the output shaft, it's already reduced to the proper amount. In this way, the reduction is accomplished at the beginning where it's much lower.

This reducer can be had with a standard input shaft, or a "QUILL" (hollow) type input that will accept the shaft of a mating electric motor or other input device. The input can have a flange that will mate with standard NEMA electric motor configurations and many IEC flanges, as well. Specials can be made to accept hydraulic motors as well as air motors. The output shaft, too, can be numerous arrangements. A flanged output, a hollow shaft output, a vertical output shaft, double output shafts, etc. etc.

Having noted previously, the various standard ratios of a "single" reduction unit, we must also mention that most manufacturers have them available in double and some triple reduction units. The double and triple reductions can be of various designs. Some have all the reduction stages as worm gear design and others have the beginning stage as a helical set of gears and the others as worm gearing. One of the problems facing the multiple stages of worm gears is that of INEFFICIENCY! The ratios are staggering .... since the ratios multiply. If we put a 5:1 into a 10:1 and finally into a 60:1 we end up with a 300:1 reducer. The problem is that the inefficiency of the worm gear and worm wheel combination in each stage, may have us driving this combination with at 1 HP motor and maybe only getting 1/4 HP out of the whole thing. That's a 75% loss of power. Now, if we make the first 2 stages HELICAL gearing we will usually only lose about 3% per gear set. That means that we only lose 6% in the first 2 stages and may very well only lose 30% in the whole thing. A whole  lot better than losing 75%! Multiple ratio units can be almost any combination of ratios you can imagine so check with the sales department if you think a multi-ratio reducer is in your future project.

The final bit of information is the size. Most manufacturers have gone to a catalog numbering system that designates the ratio and size of the unit. Size is determined by the "CENTER DISTANCE" of the reducer. Typical center distances in worm gear reducers today are 133, 154, 175, 206, 237, 262, 300, 325, 375, 450, and 516.... just to mention some standards from a few manufacturers.

Helical Shaft Mount Speed Reducers - This type of reducer is made for a specific purpose. It is used to drive conveyors! It can, and has, certainly be used for other applications, but as a whole, these devices are primarily for conveying systems.

They are physically "THIN" because they are basically available only in a single reduction unit. The output is a HOLLOW bore in the output gear set. This hollow bore is what establishes the catalog number for most manufacturers of this type reducer. The NUMBER of the reducer in the manufacturer's catalog will be as follows.... the first number will be the FULL inch dimension of the output bore and the next 2 digits will be the number of 1/16" increments". That means that a helical shaft mount reducer whose size is 307 has an output bore of 3-7/16". It's not rocket science, as they say.

The output of most reducers have a tapered bore so that it is easy to mount and dismount the reducer and also... they make one size reducer... the maximum bore available in that particular unit and then make a number of logical sized tapered bushings to fit the interior bore and match up with standard or non-standard shaft sizes.

These reducers have to be held in place because they are basically "hanging" on the shaft of the driven equipment. This is done with a "torque arm". The torque arm is a rod with a clevis device at one end to attach it to some stationary member of the driven equipment. This keeps the reducer from turning around rather than driving the shaft of the conveyor. Some of the sophistication of these devices can be that this torque arm can have a "load sensing" device like a load cell. If the load cell's rating is exceeded, that means the conveyor is overloaded and the device can trip the motor starter that is driving the whole system.

Ratios are limited. The standard ratios are 5, 9, 15 and 25:1. Because of this limiting factor, the driving device is usually connected to the input shaft of the reducer through a belt drive or some other device where an additional reduction can be established fort the application. Numerous other standard as well as special input and mounting configurations are available depending on manufacturer and particular reducer required.

Size and ratio will establish the maximum HP transmission possible but as a rule of thumb, you can figure on finding reducers of this type capable of fractional through 200 HP.

Helical Offset Shaft Speed Reducers - These reducers are designed to supply a high ratio unit in a compact footprint.

The term "offset" comes from the fact that the input and output shafts are not in line with one another.... they are "OFFSET".

Gearing is helical in design and therefore the final reducer is very efficient, typically losing only 3% power per gear-set. The helical design also makes a rather quiet type of device.

Typical HP ranges for these reducers is fractional through 150 HP and ratios are very numerous. One typical manufacturer has ratios of .... 2, 3, 4, 5, 6, 8, 9, 11, 14, 17, 21, 26, 31, 38, 47, 58, 71, 87, 106 and 130. These ratios cover single, double and triple reduction designs. In these devices, the ratios are considered "nominal" and the manufacturer actually publishes the "actual" gearing ratios so you can figure the precise output speed you'll receive at the output shaft for a given input speed.

Mounting designs vary but mounts for electric motors can be had that allow "C" flange, "D" Flange, "IEC" Flange, foot mounted motors, as well as special mounts for hydraulic and air motors. One of the many mounts that is rather typical of this design reducer is the "SCOOP" mount. The name comes from the appearance of the mount. It is attached to the input side of the reducer and looks like a "flour" or "sugar" scoop. A standard foot mounted electric motor is mounted on the scoop and attached to the reducer with a standard flexible coupling.

Parallel Shaft Speed Reducers - This reducer is a special design and considered the "Granddaddy" of them all. These are the MONSTER drives. They are what run steel mills! Horsepower ratings from the hundreds to the thousands and tens-of-thousands!

Nothing is standard between manufacturers. The size can be as small as a table to bigger than a house! Typically manufactured in single, double or triple reduction designs. Ratios similar to the helical offset shaft reducers mentioned in a previous paragraph, but as we said, nothing is standard, so special ratios can be had.

One of the problems with these devices is that they are transmitting so much power that there is a significant amount of heat generated in the gearing even though the helical and spur gears only lose the 3% per gear set. Think about it..... a reducer is being driven by a 2000 HP motor and is a triple reduction unit. We'll assume the 3% per gear set and we come up with 60 HP loss in the gearing. Now, 1 HP is 746 watts of power, so 60 x 746 is 44,760 watts of power lost to friction in the gearing. That's equivalent to the output of a furnace rated at 152,000 BTU per hour! Quite a bit of heat. So cooling is a real problem. Many times the limiting factor of the reducer is NOT the mechanical strength of the steel in the shafts and gears but the thermal capabilities. The output has to be reduced so that the various materials don't exceed their maximum thermal limit and fail.

Right-Angle Bevel Gear Speed Reducers - Another special application speed reducer. Something needs to be driven at right angles but at the same speed, or close to the same speed, as the incoming power.

In this scenario, you don't need a worm gear reducer, because even though you'd get the "right angle" application handled, the lowest ratio you can get is 5:1 and your output speed would be different than your input speed. You could maybe use a helical reducer because you can get them in 2:1 reduction but then you haven't solved the right-angle portion of the problem. So manufacturers have made the right-angle bevel gear speed reducer. The ratios are rather limited. The most common is 1:1 but 1.5:1, 1.8:1 and 2:1 are also offered.

You can get these devices in numerous configurations but the two most common are the standard right-angle and the double output shaft right angle. Horsepower ratings from fractional to 10 HP are typical.

A very special device for special applications. Call our sales staff to inquire about your project.

These are what we consider the most common speed reducers in standard industrial usage. Believe me, we haven't covered everything but I think it's the majority of what you'll encounter in your normal day to day activities.

If you find something that we haven't mentioned and want us to toss it around with you, don't hesitate to call. A.R.& E. personnel are eager to assist you and make your job easier and your next project a snap! Give us a call and we'll see what we can do.


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Copyright 2000 Apparatus Repair & Engineering, Inc. All rights reserved.
Revised: January 13, 2013.