Re the "heavy" manhole cover - please don't be misled about this!
For example, I recently built a concrete soakaway 3m deep using concrete rings. It has a solid iron manhole cover like what you see in the street which is much heavier than 7.5kg
Yes the thing is heavy for me to lift - but actually even my relatively weak partner can open it with ease.
You use a simple short hook or section of rope, to crack the cover and then shift it sideways to open. It pivots very easily
Simple physics.
The point is that with these kind of access covers, you don't need to dead lift them.
You lever them or pivot them off.
Most of the weight is supported by the ground at all times, so I only need enough force to move it up 10cm or so, and then overcome friction to drag it sideways.
In the same way i was able to reposition the concrete rings themselves because the weight is supported by the ground - i only need to overcome friction.
Bottom line, even an injured man can open a 7.5kg cover.
He does not need to use his stomach muscles to lift.
He can pivot it off with his arm/shoulder alone - or knees.
For example, I recently built a concrete soakaway 3m deep using concrete rings. It has a solid iron manhole cover like what you see in the street which is much heavier than 7.5kg
Yes the thing is heavy for me to lift - but actually even my relatively weak partner can open it with ease.
You use a simple short hook or section of rope, to crack the cover and then shift it sideways to open. It pivots very easily
Simple physics.
The point is that with these kind of access covers, you don't need to dead lift them.
You lever them or pivot them off.
Most of the weight is supported by the ground at all times, so I only need enough force to move it up 10cm or so, and then overcome friction to drag it sideways.
In the same way i was able to reposition the concrete rings themselves because the weight is supported by the ground - i only need to overcome friction.
Bottom line, even an injured man can open a 7.5kg cover.
He does not need to use his stomach muscles to lift.
He can pivot it off with his arm/shoulder alone - or knees.