If the drive unit is assembled in one continous unit-head pulley, drive pullies and take up and brake on one complete frame it should be square and true-if it is not its time to find a different supplier and put the christening bottle of chianti back in the closet.

If the concrete mounts are square and true and the frame assembly is square and true and they bolt directly on the imbedded bolts set in the concrete it is then time to pull belt and splice it and then train it- whips and dog biscuits work well :^) then break out the chianti and christen it.. ■

Highly depends on your knowledge of the benefits.

Some see the benefits of having ready made and aligned motor/reducer assemblies to minimize field fitting and replacement. It takes a sophisticated user to understand the benefit in production penalties if this is not done.

Handling only may become a problem with big (>800 kW) drive assemblies with all drive components mounted on a base assembly, most often a right angle assy.

There are other ways this can be accomplished, with smaller crane and crews.

There is a lot of detail that goes into such a method to get it truly right that avoid pitfalls.

For small equipment (<500 kW), mfgrs. have reasonable knowledge. Certainly they have more than a neophite. Engineers of big systems often have more knowledge of the details than do the mfgs. ■

Douglas..

Assemble the drive in the workshop. Then the important things to watch for are:

- Ensure the drive base is strong enough to limit the deflections at the couplings to within tolerances for all load cases

- Have the motor pointing towards the tail

- Position the torque arm about 2/3rds of the way back from the LS Coupling

- Position the torque arm on the centre-line of the drive. (This is very important).

- Use a nice forgiving flexible torque arm mounting

- Make sure the + run out on one LS Coupling half cancels the - run out on the other coupling half

- Check the alignment before you start up, as sometimes it moves in transit, especially if the neophitic fitter doesn't tighten up everything properly. (I don't actually know what a neophite is, but if Larry can use the word then so help me, .. so can I..)

Cheers

LSL Tekpro ■

Dear All,

In order to maximize alignment accuracy, you must control the low speed coupling manufacturing tolerances. This includes:

1. both couplings halves must have concentric bores to the bolt circle to within a very fine tolerance to contol offset

2. coupling mating flanges must be a right angles to the shaft bore to within very fine tolerances to control angular error.

3. There is a debate as to whether the two halves should be issued to motor and reducer manufacturers individually for their respective final fits, or to give both to the final assembler for fit and vibration test of the complete assembly.

These points are reflected from field observation of the reducer swing base precession.

We stipulate to the final assembly manufacturer the precession error in the horizontal reducer axial and transverse planes as well as the vertical. The manufacturer must machine, fit and align the components to achieve this goal.

Graham,

I wonder about the 2/3 rd position. We define the torque arm position to balance the center-of-gravity with the moment reaction of the drive, running at nominal torque, to eliminate the low speed shaft bending moment. Likewise, this is done in the transverse plane. This does not result in a 2/3 position.

Rhinebraun and others require safety straps to control the drive assembly against catastrophic damage if the low speed coupling or shaft were to shear off. Elevated structures and safety issues may dictate this requirement.

The reducer should be located to apply a compression load on the torque arm. If not, one should use caution on the linkage and limit torque arm compliance to maintain good load sharing during a loaded stop.

There are many issues of machining and fitting that may be the fodder of another thread. ■

You have omitted the delivery schedule from your original terms. If you ship all items to the "supplier" you are extending your own delivery period & comitting yourself to aligning a big chunk of machinery to an already? aligned coupling on an already installed & aligned drum under operating tension? i.e. what exactly are you trying to align? ■

Oh John,

The couplings take less time to manufacture and are normally scheduled to be delivered to respective fitters to assure bore mating and bolt circlel alignment. The couplings are not bored prior to being sent to the final fitters.

There are a number of combinations of coupling mating programs. I have noted that if not done correctly, this can become a issue in the field resulting in larger than acceptable swingbase precession. Some suppliers do not control the critical alignment governing tolerances to an adequate degree. One such factor is the bolt circle concentricity. If the holes are bored too large or the circle is not indexed, then acceptable concentricity maybe lost. This can result in higher than normal movement that does add stress to pulley bearings, low speed shaft bending stress, and reducer bearings life reduction.

The notes are cautionary. Most major European and North Aamerican suppiers have already been through the experience.

The pulley is not already aligned and neither is the reducer with respect to the pulley pillowblock. They are separately aligned. If the manufacturer is provided proper controls on tolerance and can fabricate to the tolerances, then there is no issue.

So, what tolerances should be specified? ■

I failed to add: low speed couplings are delivered prior the the major drive pulleys and reducer assembly completions. So, there is no schedule loss. ■

Larry

In fact the 2/3rds torque arm factor goes a long way to balance the drives on the pulley shafts and is a super rule of thumb, (but only of course if the motor points towards the tail pulley). For drives over around 110kW, and all high torque drives, and those requiring very long shaft extensions, (in cases for example where we need access to belt scrapers etc) we calculate the factor more accurately so the overhanging load when running is zero, and we tell the drive supplier where we want them to achieve this. This often miffs them off, but I don't care, I'm thick skinned you know.

Cheers

LSL Tekpro ■

You may ge right. I rarely get down to 100 kW. We are talking right-angle and rigid coupling/shaft mounted drives. ■

Indeed we are talking right angled drives. Hence the requirement that the motor points towards the tail pulley.

LSL Tekpro ■

Unless it is a downhill. Then they should point to the head. ■