8 replies to this topic

[liftmech]

Every lift has at least three brakes (most, four) which must operate to certain torque standards. These values are arrived at by the engineer who designs the lift, and they reflect stopping distance, the lift's vertical, and overhauling direction (the tendency of a lift to accelerate in one direction or another with all brakes released) among other factors. At least twice a year- preoperation and once during operation- the brakes must be torque-tested to ensure that they will hold at those values. (Everywhere I've worked, however, brake tests are done once a month and after any adjustments.)
Some lifts can be tested by installing a torque wrench directly onto the high-speed shaft (others by attaching a dynomometer between the brake disc and a comealong or chain winch) and attempting to rotate the lift through whichever brake is being tested. If the brake holds to that certain value, it passes. Poma also has a 'slip value' on their lifts which is 120% of the normal test value (for example, the Flyer's brakes must hold at 261 kg on the dyno, and must slip at or before 313).
A photo of this month's brake test being performed.

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•  brake_test.jpg (109.04K)
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[poloxskier]

I have noticed on some riblets there are actual rope brakes that will clamp on the rope, I am guessing that this is an all else fails brake and that it would be the most effective way of preventing a roll back if engages. Do any other manufacturers use a similar system?

[Outback]

poloxskier, on Mar 23 2005, 09:26 AM, said:

I have noticed on some riblets there are actual rope brakes that will clamp on the rope, I am guessing that this is an all else fails brake and that it would be the most effective way of preventing a roll back if engages.  Do any other manufacturers use a similar system?
<{POST_SNAPBACK}>

Beauty of the TRB was the internal clip design.
Wouldn't work with an external grip, although it would be fun to run one through it backwards at 100%!

[poloxskier]

Well it would be possible on a detachable wouldn't it? As long as the brake was located near the bullwheel after the grips had detached.

[liftmech]

Might work, but I agree with Craig that it is probably lift-size limited.
Bud, did you ever have the opportunity to see how Doppelmayr tests their brakes? The do not use the torque-measuring setup that most of us are familiar with; instead they have the mechanic or electrician but a meter on a separate set of lead from the drive, and then try to drive through the brakes one at a time. The pass/fail measurement is a measure of the current the drive is pulling, and because it's possible to know how much horsepower the motor is generating at a given current, it's also possible to know how much torque the brakes will arrest.

If one placed a bullwheel brake on the return bullwheel, how would line dynamics affect the braking? A full-speed normal stop on the Flyer generates at least two back-and-forth oscillations at the bottom return bullwheel, the first of which is a rollback of approximately six feet under full-load conditions. Granted, most lifts aren't 9900' long, but the principle still holds.

[Kicking Horse]

budfischer, on Mar 24 2005, 02:12 PM, said:

DO NOT try this test on a Riblet traction rope brake,  Nuff' said?
<{POST_SNAPBACK}>

why?

[Aussierob]

We retro fitted an electric torque test system to our Doppelmayrs a couple of years ago. Its fairly simple. It has an ammeter on the front of the panel and a key switch for each set of brakes. The key switch causes the brakes to close and bypasses the brake fault. When the switch is activated you just read the current draw off the meter. Typically the system works like this.

Perform your 5 year load test as normal. You now know that the brakes are correctly set for stopping distance and holding power. Perform a torque test using the above system. This becomes the baseline measurement. Any time in the future that you adjust the brakes, just redo the test and make sure the current draw is the same. Readjust brakes if necessary.

Caveat - This is a simplified description, I ommitted some details for brevity.

[Kicking Horse]

this may need to be in a new topic but...


How is the daily stop distance measued on a FG?

[Allan]

I'll reply here - since it's a short response. It's simple - run the lift to max speed, pick a point of reference to stop the carrier on (such as a guide sheave) & stop the lift when a grip gets to that location. Measure the distance from a point on the carrier that is directly below the grip back to the location you picked as a reference.