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Stieber offers the most comprehensive one way clutch and backstop programme in the world.
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31/08/2010

MARLAND products available from STIEBER

STIEBER represents the full range of MARLAND world-known foot-mounted overrunning clutches series CECON and the low speed backstops series BC..MA on the European, African, Middle East and Korean markets.

STIEBER and MARLAND are sister companies within the ALTRA Industrial Motion group, a designer, producer and marketer of a wide range of mechanical power transmissions products.

Together with FORMSPRAG the third company of the platform, ALTRA is the world leader producer of one way clutches and backstops.

Further information: www.marland.com ; www.altramotion.com

04/12/2007

STIEBER catalogue 2008 with a new design

Have a look at our new 2008 overrunning clutches and backstops catalogue

You will appreciate the new layout with colours and photographies that will give you the illusion the products are actually staying on your desk.

As usual you will find a complete information about overrunning clutches and backstops. From the basis to selction and maintenance.

The product range is also shown quite in details.

17/04/2001
VDMA-e-market is online
Looking for power transmission products? Visit the VDMA-e-market homepage! Note: You will leave the STIEBER-website by following this link!

27/06/2000

Double cage freewheel

Double Cage Sprag Type Freewheels

Double cage freewheels have been available for the industrial machine construction for more than 20 years. Nevertheless, the primary application for this type of unit being the automotive transmissions, their design and availability were dictated by the needs of this market. The use for industrial machines meant to accept their characteristics as they are.

STIEBER produce now an adaptable line designed for the industrial machinery and its specifics needs.

The name freewheels designates mechanical single direction automatic clutches or brakes designed for overrunning, backstopping or indexing applications.

They are composed of an inner and an outer member (races) that can be indifferently input or output. Between these races are located clamping elements, that according to the direction of rotation insure torque transmission or release in overrunning.

Several technologies are available on the market, the most known being the roller/ramp and the sprag designs.

The double cage freewheel uses shaped sprags as clamping elements. With a height of 9 mm, they are located in two steel concentric cages. A ribbon spring with individual tongues acting on each of the sprags provides for their energisation.

This double cage technology, insures a synchronisation of all the sprags for a good load sharing, backed up by the individual sprag energisation.

An effect of the spring action is that the cage rotates with the outer race. In overrunning condition, the relative motion takes place between the inner race and the sprags. When the working conditions may cause the cage assembly to slip within the outer race, additional friction springs called clips and secured on the outside of the outer cage reinforce the connection.. 3 to 6 clips are generally sufficient., but it is always possible to increase the number when necessary.

This cage is generally sold as such, without inner or outer races. It can be mounted in the machine parts, running directly on a case hardened shaft and located inside a gear wheel for example.

These double cage freewheels were originally designed for use as lock up clutches in automotive torque converters and overrunning clutches in automatic gear boxes...
These applications feature good concentricity, high overrunning speeds and lubrication with ATF oils. The requested life time does not exceed 2000 hours.

Other sizes than the ones currently available were not possible to manufacture. Any size could rapidly become obsolete if the main automotive application that supported it was fading out.

In case of industrial applications, the overrunning speeds are generally not so high, but the requested life time much longer.

In addition, it is not always possible to provide for the best concentricity and the range of lubricants employed oil or grease may be vast. Applied torque may have dynamic variations that are not always clearly evaluated.

STIEBER with their DC type want to offer the users a double cage type freewheel that answers better the needs of the machine construction. The present results are as follows:

Tests have shown that the present STIEBER unit is able to work as a backstop in gear reducers using the standard gear oils.
It is possible to increase considerably the overrunning life time by using the "Formchrome" sprag treatment. Overrunning tests have shown life time increases up to 4 times outscoring all other methods to increase sprag type freewheel life time.
STIEBER DC cage is available in all the original imperial dimensions, but models with a metric outside diameter are also available. This dimension matches the one of current bearings and allows a plain outer race path cheaper to manufacture.
As long as we can use the standard sprag, any dimension can be manufactured in quantities as small as 25 to 50 pieces according to the size. This flexibility of manufacture may be convenient as much for new applications as to obtain replacement for designations considered as obsolete.

As an evolutive product STIEBER will actively use their experience to continuously improve the design and adapt it to the industrial machine construction needs.

Plans are to improve the sprag fatigue resistance, to allow the use of gear oils in a wider spectrum of applications and authorise larger run-out mounting tolerances.

Further information:
Bernard Fayol, STIEBER- Product Manager

27/06/2000

STIEBER belt pulley prevents 'Mr Angry'

Trucks for refrigerated food transport or air-conditioned buses require more and more electrical power, which in turn means that larger and larger alternators must be driven by the trucks Diesel engine.

Unfortunately, as the alternator increases in size, its inertia increases exponentially. This results in conflict between the high inertia generator trying to run smoothly at a fixed speed and the fidgety Diesel engine delivering nothing but torque peaks.

The victim of this incompatibility is usually the drive belt between the alternator and the Diesel crankshaft pulley. It stretches, swings and vibrates until drive to the alternator fails either by the belt jumping off both pulleys, or with the belt being shredded as it passes over the pulley flanges. In any event, without alternator drive the bus or truck must soon stop until the drive is repaired. 'Mr Angry' soon appears either as one of the passengers stuck on a bus which is rapidly warming, or from the suppliers (or customers) of rapidly melting food on the truck.

STIEBER have designed an alternator pulley with an integrated overrunning clutch which helps to eliminate belt failure.
From the outside, it looks like an ordinary pulley, but inside the boss there is a bearing supported roller-ramp type overrunning clutch.

Just like the freewheel on a bicycle the overrunning clutch transmits torque when the driven part tries to run slower than the driver. If the driven part tries to run faster than the driver it is free to do so. Greased for life, the unit is maintenance free with centrifugal force keeping the lubricant where it is required - between the rollers and the outer race.

Typically, the overrunning clutch pulley is mounted on the alternator shaft and allows the alternator to overrun between the engine firing cycles.
The torque measured on an alternator shaft fitted with a standard pulley looks like an earth quake magnitude 7 on the Richter scale. With the overrunning clutch pulley fitted the torque curve is almost a flat line.

Technically, this is a demanding application. If for example the Diesel runs at 2000 rpm, the clutch must cope with 3 firings per engine rotation, or 6000 per minute.
Thus in a life-time the clutch will have to withstand billions of torque cycles, and this will be whilst rotating at around 6000rpm due to the drive ratio between the crank and alternator. Two sizes of STIEBER clutch pulley are now in regular production. Other sizes are currently on test.

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