It's just a matter of energy, the energy of the crane is transferred into the buffer. But you haven't told us what type of buffer you are using? ■

Search Google for "Impulse Force Calculation".

The impulse force is a function of the the time to bring the crane to zero speed. ■

The kinetic energy of the crane equals the potential/strain energy of the buffer, give or take hysteresis effects in the rubber. Knowing the buffer spring rate you can determine the maximum compressive force in the rubber. That's your buffer force.

ANSYS is not useful in such cases because the model swap file is too big for large strutures.

As Lyle says the force will also have to be factored to meet the requirements of the various crane standards. Especially so, because your 30m span machine is unlikely to engage the buffers simoultaneously & at 0.6m/s it is quite a flyer.

The Australian Code AS1418 is particularly useful as it incorporates so many of the latest ammendments to other established crane standards. There is also a standard for continuous material handling machinery. ■

Hi,

The energy calcs. should take into account the following

Max design wind acting in the un-favourable directions

The interia of the drive system ie motors at high speed cf wheel speed.

Plus the torque from the drive motors as they decellerate from full speed to stopped

Your machine loads...at 0.6m/sec,

To stop the machine - U have to disappate all of these loads.

I would suggest a hydraulic type buffer rather than an elastomeric one.

The latter is a spring > more deflection > means more reaction forces plus the bufffer will then try to push the machine away after when it has stopped your crane.

For the thermal expansion...why not have free play in your bogey pivots ?

Thanks

James ■

Pinned frames are used on high perfomance heavy duty cranes to compensate for rail misalignment, however slight. At your duty level, in anybody's code, thermal expansion is not an issue. Imagine you have a steelworks crane parked over a soaking pit, air conditioning is applied to the girder internals, with a 290 tonnes load underneath; then thermal issues do have relevance.

Your 18 tonnes load is...9 per buffer or 18 on the first side to hit?

Wheel spin at rest would give you about an extra tonne per track; windage should be included in your 6m/min??

In my day we used to curl the rails as well if it was a bog rough outdoor machine i.e. weld a 35-50 mm profiled panel onto the rail head so the beast had to climb as it stopped. Don't forget that you shouldn't be hitting the buffers anyway. ■

How do you guarantee that the crane hits the two buffers evenly?

Surely a more likely scenario is that one buffer is hit first?

Worst case is that only one buffer absorbs all the load?

At what point have you cut the power to the longitudinal drive motor, maybe the drive is still on when you are hitting the buffer(s)? ■

Most elastomeric and hlical spring buffers are very non-linear. So, the average deceleration velocity will not apply.

The difference in impact between the two buffers must be evaluated with the potential crabbing of the wheels, the angle of the crab position, its related displacement between buffers and the buffer displacement.

In most instances, the crabbing angle is quite small when considering the play between front and back wheels. Takeing that angle across the crane buffers will also result in a small difference in comparison with the displacement of the buffers.

There may be a difference in load sharing, but, I suspect it will be small. ■