Last week’s technology lesson with Gramps covered lots of ground, most of it beyond me. However, Emily helpfully wrote me a great summary of all that she learnt with Gramps on that occasion – which seems to have been loads!
First up, they watched a video about differentials, which, Emily tells me, are mechancial devices which allow wheels on vehicles to rotate at different speeds, improving turning ability and safety. Gramps showed Emily this model of differentials in action (good old mechano!).
They then talked about whippletrees – for the uninitiated, like me, it transpires that whippletrees are devices used to distribute weight more evenly. Emily explained to me that whippletrees are used for draught horses, as for them to pull a load without one would be uncomfortable for them, and a bumpy ride. She also told me that they’re used in windscreen wipers to allow the force of the wiper to follow the curve of the windscreen. Apparently, they’re also used to lift concrete bars that have been reinforced with steel; these are strong under compression but weak under tension and will break under their own weight if lifted without a whippletree to share the load. There were lots of diagrams to illustrate these; they’re also used in the complex interlocking systems of automatic drive cars, so Gramps showed Emily in his car.
Back to differentials, Gramps explained to Emily about other uses of differentials, such as in adding/subtracting machines and analogue computers (with whippletrees – who knew?). Gramps also showed Emily a slide rule and explained how it was a precursor to the calculator, and could be used for adding, subtracting, dividing, multiplying, roots etc. She loves “old technology”, so she was very interested in that if rather glad that we have calculators these days! On a related note, Gramps has a fantastic, very old, manual adding machine thing with all sorts of interesting levers and bells and whatnots – Emily’s really looking forward to having a go with that!