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High-speed coupling?

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High-speed coupling?

High-speed coupling?

McLeod

(Mechanical)

(OP)

23 Mar 04 18:42

I'm searching for a small (~.187 in OD) flexible coupling for a low-torque (~2 oz-in), high-speed (80,000 rpm) application in which the angle between the rotating shafts ranges from 0 deg. to 20 deg.

Of the flexible coupling options that I've explored so far (U-joint, ball, bellows, spring, jaw, Oldham, Schmidt, flex-shaft, etc.), there are many options of workable size which can handle the torque, but none that can come close to meeting the speed requirement even when run in-line, much less at 20 deg. angulation.

Does anyone know of a component which meets the specs?

Replies continue below

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RE: High-speed coupling?

CouplingKing

(Mechanical)

25 Mar 04 10:44

There is no standard product available to do this duty.

Rexnord offer a metal disc type coupling from their BSD series that can cope with rpm, but it is limited to about 1 degree angular misalignment. They are quite specialised but they may be able to help.

The only couplings used for misalignments above 10 degrees are universal joints, and these normally can't handle the speed.

Goodluck

CK

RE: High-speed coupling?

McLeod

(Mechanical)

(OP)

25 Mar 04 11:09

CouplingKing - thanks for your feedback!

One thing I should add is that the duty cycle is intermittent - one minute on, one minute off, over approx. 60 min. for one "use".  It has occurred to me that the vendors' published ratings may carry an assumption of continuous duty over longer periods.  I've asked one vendor (whose products are rated to 20,000 rpm) to clarify the test criteria, but have not heard back yet.

Is there an applicable standard for rating the top speed of couplings?

RE: High-speed coupling?

CouplingKing

(Mechanical)

26 Mar 04 04:02

The short service life will give you considerably more options for both speed and misalignment. If a metal disc coupling is misaligned beyond it's normal operating range, the discs take on an S shape when viewed from above. The high stress points are where the S shapes start and finish, this is also where the discs will flex during the rotation. Hence fatigue failure is the expected failure mode. With the short life time, you may get away with it, the manufacturer will have to advise you.

Mayr make a disc coupling of a similar type, where the discs are Star shaped, allowing significantly more misalignment capability. I think they call it a DS-W. DS is the standard high performance metal disc coupling, I think the W variant offers bigger misalignment, but I am not sure about the speed. Their website is

Hope it goes well.

CK

Catalogue ratings are based on an acceptable service life. Coupings are generally expected to outlast gearbox bearings, with the replacement of occasional wearing parts (e.g. rubber spiders in jaw couplings).The short service life will give you considerably more options for both speed and misalignment. If a metal disc coupling is misaligned beyond it's normal operating range, the discs take on an S shape when viewed from above. The high stress points are where the S shapes start and finish, this is also where the discs will flex during the rotation. Hence fatigue failure is the expected failure mode. With the short life time, you may get away with it, the manufacturer will have to advise you.Mayr make a disc coupling of a similar type, where the discs are Star shaped, allowing significantly more misalignment capability. I think they call it a DS-W. DS is the standard high performance metal disc coupling, I think the W variant offers bigger misalignment, but I am not sure about the speed. Their website is www.mayr.de and follow the links to the English language section.Hope it goes well.CK

RE: High-speed coupling?

amorrison

(Mechanical)

26 Mar 04 15:59

some maybe options

1. electric generator->electric motor power transfer
Coupling via wires (and suitable electronics?)
2. gear down the input rpm - go through a "regular" coupling and then gear up again
3. do gaseous couplings exist? This is how low rpm power is extracted from very high rpm jet turbines
4. Maybe a gaseous viscosity friction coupling - two impellers "connected" by gas friction using a bellows container enclosing the system.
5.magnetic coupling system?

RE: High-speed coupling?

EdDanzer

(Mechanical)

30 Mar 04 22:09

Amorrison4,
I like your magnetic coupling idea, but mass and size could be a problem.
A hex socket and hex ball ( on the end of a hex wrench) might work. Picture a socket head cap screw and a ball hex allen wrench, and a dry lub.

RE: High-speed coupling?

Warpspeed

(Automotive)

1 Apr 04 04:29

Just a stab in the dark, but how about a short lenth of flex cable ?

RE: High-speed coupling?

fredt

(Mechanical)

For more information, please visit High Speed Grid Couplings.

1 Apr 04 08:10

Because the dimensions are so small and the torque very low it is likely that something quite simple will work - the 20 deg angle is difficult however and the geometry of the axes intersection point will also be significant.  A magnetic coupling is probably ruled out because the halves have to be in close proximity.

I would try a helical spring set up to tighten with rotation.  It may be a better option than the flex cable suggested which is also worth considering.  Although the speed is high the very small diameter means that centrifugal forces will not be great.  You will need a bit of luck to avoid instability problems.  On that scale it should not be an expensive exercise to test various options on a simple rig.  I much doubt that you will find a stock design to do the job.

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News

The guideline to make the right coupling selection

In the power transmission field, there are many different types of couplings that can be used in order to transfer power from the gear side to the machine. Taking into consideration that each specific application has its own features, it is extremely important to analyse and check what characteristics should our coupling have, to ensure a long-life cycle and a successful performance of our machinery.

We should take into account the following factors in the coupling selection process:

1. Environmental requirements: temperature, corrosive environment, etc.
2. Accessibility: space required to apply the coupling.
3. Geometry requirements: Type of shafts.
4. Coupling sizes: maximum outside diameter and length to work with.
5. Misalignment requirements: angular, torsional misalignment, angular, etc.
6. Mechanical performance requirements: torque, speed, cushioning capability, etc.

1. Environmental requirements

It is important to analyse the area, the temperature where the coupling is going to be exposed, and also if the device is going to be in a corrosive environment or not.

2. Accessibility

The space might be an issue when placing the coupling. In some applications there is a limited or a difficult access to locate the coupling. Therefore, this is also another key aspect to take into consideration for the coupling selection.

3. Geometry requirements

The type of shafts should be checked, as well as the diameter and the length.

4. Coupling size

As an example; considering the access, space required, and the shaft types, we have to analyse what size would apply best to our installation from our range of products. 

5. Misalignment requirements

The operator should check what types of misalignments should be corrected; parallel, torsional, axial, angular or lateral.

6. Mechanical performance requirements

The main target consists on understanding what kind of performance we want to have with our coupling; high torque, high speed, repeatability or high level of flexibility and cushioning.

Decide which type of coupling will be most appropriate depending on the above aspects.

• Rigid coupling: provides a solid connection between two shafts, high precision, and torque transmission but it has no misalignment capabilities. Explained in another way, it allows no movement between two shafts. Sleeve type coupling, flange type coupling, 

• Flexible coupling: compensates for some misalignment, movement or deflection. It is very useful when having quick and short starts. Normally less torque transfer, but it can absorb misalignments and shocks.

Instructions for coupling selection

In order to determine the type of coupling to be used the following formula should be applied:

M = N hp/ n. . K

M = N kW/ n. . k

M = Nominal torque

N = Driving-motor power (CV or KW)

n = Minimum speed of the connected axles (rpm)

k = Multiplying co-efficient

The value obtained on applying the formula should be less or equal than the indicated in the tables of sizes and powers that refer to the corresponding coupling in the column &#;nominal torque&#;.

k = Multiplying co-efficientElectric motor
Steam turbine
Transmissions11.522.53Steam machine
Gas machine 
Hydraulic Turbine
Diesel 4-6 cylinders1.522.533.2Diesel 2-3 cylinders
4 Stroke motor2.22.52.83.23.5Diesel 1-2 cylinders
4 stroke motor2.62.833.54

Notes:

The values indicated in the above table are by no means applicable to every case. If, for example, one of the machines to be coupled displays such a degree of irregularity that it is judged necessary to carry-out technical investigations of the oscillations, then it is recommended to proceed to the selection of the multiplying co-efficient using the enclosed questionnaire.

The following groups apply to the machines being driven:

K-coefficient calculation guidance for different groups of machines.

1. Continual load machines: Generators (electro genetic group). Conveyor belts. Small hoisting equipment of up to six starts per hour. Low power machinery for working wood. Small fans. Small machines of which principal movement is rotation. Small centrifugal pumps.
2. Generators (electro genetic group). Conveyor belts. Small hoisting equipment of up to six starts per hour. Low power machinery for working wood. Small fans. Small machines of which principal movement is rotation. Small centrifugal pumps.
3. Variable load machines: Small hoists. Generators. Winches. Hoisting equipment of up to 120 starts per hour. Conveyor chains. Crane movement mechanism. Sand blast equipment. Textile machinery. Transmissions. Conveyors Turbo blowers (gas blowers: compressors). Fans. Machine tools in which main movement is rotation. Large winches. Centrifugal pumps.
4. Normal size to heavy machinery: Heavy hoists. Revolving ovens Tannin barrels. Cylinder grinders. Refrigerating drums Continuous Ring Looms. Mechanical mixers. Cutters. Sharpening machines. Washing machines. Looms. Brick presses. Fans Hoisting equipment of up to 300 starts per hour. Translation mechanism.
5. Heavy machinery: Dredge control mechanism. Briquette presses. Rubber rollers. Ventilators for mines. Machinery for sand papering wood. Sand and paper grinders. Pumps with immersible piston. Cleaning drums. Machinery of oscillating movement. Compound grinders. Cement grinders. Drawbenches. Hoisting mechanisms. Hoisting Equipment of more than 300 runs per hour.
6. Heavy machinery of variable energy consumption: Large drilling installations Machinery for glossing sheets of paper. Horizontal and reciprocating vertical saws. Presses. Paper calenders. Roller trains for laminators. Drier rollers Small rollers for metals Centrifuges. Roller equipment for paper.

Key factor for the coupling selection process

Example:

The elevator bucket is driven by a motor of 16 kW; n=1.450 rpm., by means of a reducer whose outlet axle rotates at a speed of n= 180 rpm. The motor and reducer are protected by a UNE-FLEX flexible axle coupling.

1. COUPLING BETWEEN MOTOR AND REDUCER

N = 16 kW
n = rpm
M = NKw/n. . k

Elevator buckets figure in group 2 of the classification. Under &#;variable load machinery&#;. The multiplying co-efficient k = 1,5 figures in the k value table under heading 2 and in the classification of machines driven by &#;electric motor&#;.

M = 16/ x x 1.5 = 158.07 Nm

Then, according to the power table. the appropriate coupling for a torque of 158 Nm. is model M-5.

2. COUPLING BETWEEN REDUCER AND ELEVATOR, BUCKET MECHANISM

N = 16 kW
n = 180 rpm
M = NKw/n. . k

M = 16/180 x x 1.5 = Nm

Then, according to the power table, the appropriate coupling for a torque of Nm is the model M-9.

Note: to carry out the correct selection of a coupling, an indication of power and speed is generally sufficient. However, it&#;s better to have the following information as well:

The company is the world’s best Parallel Shaft Gear Reducer supplier. We are your one-stop shop for all needs. Our staff are highly-specialized and will help you find the product you need.

NECESSARY DATA FOR THE SELECTION OF THE APPROPIATE UNE-FLEX COUPLING DRIVEN BY ELECTRIC MOTOR

1. Kind of motor (make, type, running factor in ED %
2. Power of motor: N&#;..kW
3. Speed: n&#;&#;.rpm
4. Input and output shaft diameters
5. Couple of start of the motor: C = Nm
6. Type of machine to be driven
7. Whether operation is continuous or intermittent
8. Number of runs per hour
9. Whether operation conditions are uniform, irregular or special, and if there is any running change