So as a bit of background, the engineering company I work for has two old cranes. They just failed their lifting certificates, because they don't have the the modern alarm and sensor systems modern cranes have. They see very little use - maybe between the two of them, they get used twelve times a year. We can't afford to buy new cranes, and these ones suit our needs just perfect in function, so I put my hand up and said I would have a crack at the task of retrofitting the cranes with a modern system. To give you an idea of the age of these cranes, one is a 1967 Oxford, max lift 5.2T and the other is a Scotch Derrick with an extendable boom, max lift 3.2T mounted on the back of a 1945 Mack truck (the crane is older and was mounted on a Reo somewhere between 1915 and 1935).
Now this is not the first time they have needed things fitted. In 2006, I designed and built hydraulic load cells to go in the luff lines of the boom, so they could know the lifting weight, if they read the lift radius and pressure and looked at a graph on the wall of the cab they would know the weight. This allowed us to keep a lifting certificate until now.
So I have come up with this plan for the 1945 Mack: two oil-filled pendulum gimbal boxes, with hall-effect industrial sensors on the shafts to measure rotational angle going back to a small data acquisition board in each box which has a serial cable hook-up. One will be placed on the boom, the other on the luff wire, which will give angle data for boom length and lift radius. There will be a third gimbal box with an added pressure transducer which will be hooked up to the load cell. This will be put on the floor of the cab so we have the vehicle orientation data and load weight. All this data needs to be crunched so it will go back to a PC/104 computer which will run an LCD and interface for the driver, trigger alarms and act as a black box in case of an accident. This whole system will automatically be turned on when the engine is started.
The 1967 Oxford will have a similar setup but the boom stays the same length so will not have a gimble box on the luff wire. The cab is mounted on a slew so there will be a hall effect sensor put on the shaft that rotates the slew so I know where the crane is pointing. The mathematics for the vehicle orientation will be different since the gimbal box will be rotated with the cab but physically the sensor arrangement is the same.
Oh I know this is going to come up, I thought about accelerometers to replace the gimbal boxes but there is a lot of vibration and we can make the gimbal boxes in house cheaply, so I thought, for accuracy and less signal processing, this would work well.
Now this is my first practical electronics project, I normally work as the senior system admin / stock management and acquisitions person at work.
Please give me some feed back if this is madness
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