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gearbox rotate from output

gearbox rotate from output

(OP)
Dears,

I would like to know what happened when a gearbox rotate from output instead of from input?
I know it is harder to rotate gearbox from output instead of input, however I don't have any value.

there are cases that the motor is off, however the machine can rotate the gearbox because of inertia or other sources. Does it make damage to gearbox?

Is there any value how much power needed to rotate a gearbox from output?

RE: gearbox rotate from output

You're talking about the unit as a speed increaser.

The efficiency is probably about the same going in reverse as going forward. Unless it's a worm drive, the torque ratio will be similar in both directions.

The main mechanical risk IME is when the unit has a force lubrication system that is not running when the gearbox is backdriven, because then you can get lubrication failures. If the bearings and gears are greased or dip lubed you should have little risk.

Check your safety requirements - backdriven equipment can be extremely dangerous to personnel especially if the source of movement is unpredictable.

RE: gearbox rotate from output

(OP)

However I have experienced it is very hard to rotate the gearbox form output, isn't it?

RE: gearbox rotate from output

Quote (mas26amin)

However I have experienced it is very hard to rotate the gearbox form output, isn't it?

That depends entirely on what type of gearbox it is we're evaluating here.

RE: gearbox rotate from output

geesamand

It can be locked for reverse motion even with spur gears if the gears are designed to be "All Recess Gear" or even with larger recess action than access action.

RE: gearbox rotate from output

To clarify, when it is not a full recess action gear the reverse action can be much harder (lower efficiency) but may not be actual locked.

RE: gearbox rotate from output

(OP)
The gearbox type: bevel helical gearbox, rotation ratio= about 30
can it have reverse motion?
if hard, how much hard, is there any value?

we have a belt conveyor with dual drive,one on head the other on tail. I would like to know if one motor is on and the other is off, what happened?
in this case the belt forces the gearbox to rotate in reverse motion.

Is there any data that shows gearbox and motor can work in this case or not?

RE: gearbox rotate from output

If you grab a shaft and turn it, you will feel the friction of the bearings and the rotating inertia of the rotating parts.

If you twist the small shaft, you will have up to 30x more leverage and it will spin easily and turn the big shaft slowly. If you turn the big shaft, you will feel much more torque and the small shaft will spin more quickly. This is normal and it's the principle of a gear reducer - trade between torque and speed.

At the end of the day, you want to know if the gearbox can be driven as a speed increaser. You ask us for data, but the only data you offer is "ratio = about 30". As mentioned above, a few helical designs cannot run in both directions. So you need to take the nameplate information to the OEM and see if it can be done. We can't answer that.

RE: gearbox rotate from output

(OP)
the power of the motor is 110 kW.

RE: gearbox rotate from output

Based on the description of the gearbox provided, I assume there is at least one spiral bevel gear mesh used. Some things to consider when back-driving a spiral bevel gear mesh is how the forces on the bearings change, and how the mesh contact pattern is affected.

RE: gearbox rotate from output

I expect something will break. If two motors are required and only one is operating and is set to backdrive the non-operating one through a high reduction box, most likely the operating motor will overheat and fail from the additional load, if it doesn't stall out.

At the least there should be over running clutches to prevent one motor/gearbox from trying to backdrive the other.

RE: gearbox rotate from output

(OP)
As the system is reversible, in each time only one motor needed.

Is there any documents or references that show this type of gearbox could not be backdriven?

RE: gearbox rotate from output

Do you, or do you not, have the ability to contact the manufacturer of this dual-drive system?

At some point internet speculation becomes wasteful.

RE: gearbox rotate from output

geesamand - we passed that point a while ago.

Information that would have helped - manufacturer nameplate for gearbox, including maker, model number, possibly reduction if not clear from model number. Some idea what the non-operating torque to turn a motor and the expected RPM, and maybe a full schematic of the system.

Too late now.

RE: gearbox rotate from output

The inertia from the output end would of course drive/rotate the input geared motor if this was not fixed.

This can be done manually (with some effort) but also happens when the power is switched off at the input leaving the output 'coming to rest' which may
last some time.

In the case of large rotating structures, 'coming to rest' period should be noted with caution and safety considerations, as huge amounts of
kinetic energy is present, and from our experiences it is important not to brake by mechanical/hydraulic means too quickly if not at all.
This depending on the application of course.

By braking too quickly, mechanically or hydraulically, does intensify stresses/pressure beyond practibility causing input gearedmotors
to be damaged and smashed beyond repair.

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