I want to provide a more gentle start to a machine via some type of fluid coupling or other mechanical soft start mechanism in order to protect the gear train "downstream" of a motor from torque shocks.
The machine is a stoplog lifting crane on a dam. The mechanism, although sheltered from wind and precipitation, is otherwise subject to ambient temperatures -30 to +30 [sup]o[/sup]C. It is operated about twice a week year round for a couple of hours to a whole day at a time. The dam is in the middle of nowhere which makes it difficult and expensive to get any maintenance or repairs done.
The prime mover is an antique 1961 GE wound rotor induction motor, 15 hp, 875 RPM with starter and drum controller of the same vintage. The motor frame size is 324Z.
There is a V-belt from the motor to the gear trains, which consists of early 20th century cast gears. A clutch system allows the motor to drive either the hoisting gear train or the travelling gear train (the machine moves along tracks on the dam deck). The motor must deliver power in both directions of rotation. The motor and gears see some plugging and jogging service as the operators have to get the machine lined up just right over the sluices in order to place stoplogs correctly in the gains.
The condition of the gears varies from reasonably OK to really poor. The journal bearings throughout the machine are very loose, and some of the gears farthest from the motor actually have trouble meshing because of all the backlash and general slackness in the system. (We're planning for some gear and bearing repairs, but we won't be replacing all the gears certainly).
I want to protect the gear train from torque shocks after the repairs.
Because of the age of the motor and associated controls, and because of the wide range of ambient temperatures, I'm afraid of the can of worms involved in fiddling around with electric soft starts or VFDs.
As for mechanical soft-starts, I think I have a few options:
Fluid couplings sound pretty good and I've found several suppliers of them, e.g.
-Siemens' FLUDEX
-Voith (but they seem to supply only really big stuff not the little things I'd need)
-Kraft Power's Transfluid
-Baldor-Dodge's Paraflex
These sound good, but I'm worried a bit about the wide temperature range and how the viscosity of the oils used in them would react.
Centrifugal clutches sound like an option that may be less sensitive to temperature, but they seem to be more popular for automotive applications than industrial ones. The suppliers I’ve found are:
- Hilliard's Twiflex or Linkless centrifugal
- Noram
- BLM
Baldor-Dodge's Flexidyne is like a fluid coupling, but uses pellets of steel shot instead of oil. This seems to be a real Goldilocks solution, but I really know nothing about them beyond what I read in the product literature. Does anyone know of other manufacturers who offer this type of device?
I'd like to hear from folks who have experience with mechanical soft-start devices what they have found to be the relative merits of centrifugal clutches vs. fluid couplings (vs. other alternatives?)
Also, I suspect that having such a soft-start device installed may make it slightly more difficult for the operators to get the machine lined up properly over the sluices, as by its very nature it would impair their ability to plug and jog the motor. (We may have to supply them with some type of pry-bar so they can shift the machine along the tracks for fine-tuning the position.) Any other implications that I may not be aware of?
The machine is a stoplog lifting crane on a dam. The mechanism, although sheltered from wind and precipitation, is otherwise subject to ambient temperatures -30 to +30 [sup]o[/sup]C. It is operated about twice a week year round for a couple of hours to a whole day at a time. The dam is in the middle of nowhere which makes it difficult and expensive to get any maintenance or repairs done.
The prime mover is an antique 1961 GE wound rotor induction motor, 15 hp, 875 RPM with starter and drum controller of the same vintage. The motor frame size is 324Z.
There is a V-belt from the motor to the gear trains, which consists of early 20th century cast gears. A clutch system allows the motor to drive either the hoisting gear train or the travelling gear train (the machine moves along tracks on the dam deck). The motor must deliver power in both directions of rotation. The motor and gears see some plugging and jogging service as the operators have to get the machine lined up just right over the sluices in order to place stoplogs correctly in the gains.
The condition of the gears varies from reasonably OK to really poor. The journal bearings throughout the machine are very loose, and some of the gears farthest from the motor actually have trouble meshing because of all the backlash and general slackness in the system. (We're planning for some gear and bearing repairs, but we won't be replacing all the gears certainly).
I want to protect the gear train from torque shocks after the repairs.
Because of the age of the motor and associated controls, and because of the wide range of ambient temperatures, I'm afraid of the can of worms involved in fiddling around with electric soft starts or VFDs.
As for mechanical soft-starts, I think I have a few options:
Fluid couplings sound pretty good and I've found several suppliers of them, e.g.
-Siemens' FLUDEX
-Voith (but they seem to supply only really big stuff not the little things I'd need)
-Kraft Power's Transfluid
-Baldor-Dodge's Paraflex
These sound good, but I'm worried a bit about the wide temperature range and how the viscosity of the oils used in them would react.
Centrifugal clutches sound like an option that may be less sensitive to temperature, but they seem to be more popular for automotive applications than industrial ones. The suppliers I’ve found are:
- Hilliard's Twiflex or Linkless centrifugal
- Noram
- BLM
Baldor-Dodge's Flexidyne is like a fluid coupling, but uses pellets of steel shot instead of oil. This seems to be a real Goldilocks solution, but I really know nothing about them beyond what I read in the product literature. Does anyone know of other manufacturers who offer this type of device?
I'd like to hear from folks who have experience with mechanical soft-start devices what they have found to be the relative merits of centrifugal clutches vs. fluid couplings (vs. other alternatives?)
Also, I suspect that having such a soft-start device installed may make it slightly more difficult for the operators to get the machine lined up properly over the sluices, as by its very nature it would impair their ability to plug and jog the motor. (We may have to supply them with some type of pry-bar so they can shift the machine along the tracks for fine-tuning the position.) Any other implications that I may not be aware of?
