Category: Clamping System

Ohhh noooooo, Mr Raman is on leave 🙁

This meant that we can’t:

1. Grind our 2x 15cm rods down to fit into the pillow blocks better. 
2. Get our 1x 25cm rod 

Here are the two too-big rods:

 

 

The 15cm rod (on right) is unable to fit into a significant length of the pillow block. The diameter of the pillow block probably isn’t consistent or has some (invisible to the naked eye) slight protrusions here and there, which caused the rod to be unable to fit into the pillow block.

One of our 15cm rod (on left) can fit into the pillow block quite well but cannot go past the black screw hole portion of the pillow block. As we can see, there is a slight protrusion from the black screw hole area. This may cause the interference fit between the 15cm rod and pillow block to be too tight.

 

 

Even though the rod can be rotated quite smoothly within the pillow block, even with the poor fit seen in the rod and pillow block on the right, we decided that it is not safe to use it for our lifting arm. Safety first!!!!

 

 

On the bright side, some of our ball joints arrived. These, pictured below, are typically used in cars for stick shift control. They seem to be pretty strong.

 

 

Here is a video of the ball joint rotation:

 

 

 

 

Here are some possible double ball joint configurations which we can try out:

 

 

 

 

 

 

 

We will brainstorm the pros and cons of each configuration before giving yall the update!!

 

Lastly, we need to settle how the Programmable Logic Controllers will work.

 

We bought a wireless controller which has the up, down, left, right button for remote control. However, we haven’t figure out what Programmable Logic Controller to use yet.

 

We had two possible choices for lifting arm control:

1. Manual control of individual actuators
2. Manual control of “Up, Down” motion

 

Manual control of individual actuators will mean that the controller will have a set of 3 up and down buttons for all three actuators. SMRT technicians will then have to know which buttons to press to control the actuators to raise the units to different heights. While this will be easier for us to programme, the SMRT technicians will need to be keenly familiar with the stroke length and angle of each actuator. This may be challenging for the SMRT technicians to master. Also, the motion of the lifting arm may be slower as actuators cannot move together, upwards.

 

Manual control of “Up, Down” motion will mean that the controller will have one set of up and down button, which controls all 3 actuators. We will have to do careful motion study in real life, with measurements, translate this into an algorithm with up and down motion and then code it into our Programmable Logic Controller. While this will be a lot more time-consuming and challenging to programme, the SMRT technicians will find the lifting arm easier and more efficient to use. Also, the motion of the lifting arm may be faster as the actuators can move together, upwards.

 

hmmmmmmm, thinking

 

 

 

 

 

On 5 Jun, our risk assessment finally got approved! YAY!!

 

 

To us, bastions of safety and wellbeing, this was a crowning achievement.

 

This meant the procurement of the safety paraphernalia. We went to look for safety boots online. We found some pretty-looking safety boots on Amazon. However, Tony, our experienced 5th to 10th member,said that safety boot sizes can be quite different from our normal shoe sizes, and recommended us to buy them in person. When we borrowed safety boots from SMRT for our Tuas Train Depot site visits, we also felt that the safety boot sizes are usually larger than normal shoe sizes. So we decided to buy them in person instead.

 

However, we faced lots of problems. Places selling cheaper safety shoes did not seem to have a retail or outlet store where we can try them out.  We discovered that Timberland sold safety shoes, however, they were really pricey, at about $200 for a pair. A whooping $800 (about half of MnT budget) to buy shoes for all 4 of us.

 

hmmmm, how?

 

Also, we are reconsidering our first lifting design which has an extruding arm and worm gear. Worm gears, those in our price range at least, are too weak to lift the heavy load of the lifting arm and the unit, with a maximum torque of about 60-100Nm.

 

Hence, we decided to use linear actuators. They are much stronger and can exert a lot more force at about 3000-5000N. This meant that the linear actuators is more likely to be able to lift the lifting arm and the unit (to be substantiated with calculations soon).

 

The drawback of using linear actuators is the decrease in the rotational ability (directly translated to mobility in our first design). To counteract this, we will use a configuration of 2/3 arms connected with linear actuators. To preserve the high mobility of the clamping system, we will still use a ball socket joint between the lifting arm and the clamping system.