C.Defeo's Decorating and Building Merchants


Hans and Matilda wanted some sheet metal to build the battery box so popped down to C.Defeo's Decorating and Building Merchants for supplies. The shop keeper advised them that he only had large sheets but he'd cut them for free. He lead Hans and Matilda to the yard out back where the massive sheets of stainless steel were stacked. Hans and Matilda looked up at the sheets and could not work out how the shop keeper was going to move them. He pulled a flute out of his pocket and played a strange tune. From what appeared to be a pile of cement sacks slowly arose a grey brown figure who lumbered over to where they were standing, it was a golem! The shop keeper passed the golem a bottle of ginger beer and he drank it down. The golem turned red then yellow then white and Hans and Matilda realised he was getting very hot so stepped backwards. The golem swiftly and neatly sliced through the metal sheets with his white hot hands before collapsing back onto the cement sacks and falling fast asleep. He does not need much explained the shop keeper, just a few spoonfuls of cement and gingerbeer. "We think he generates acetylene gas which burns internally to produce the heat, not quite sure how it works" he explained, "but it does a good job". "He will now need to sleep for an hour to cool down". The shop keeper explained that he'd been gifted the golem by a Rabbi from Prague in return for some electronic components. Hans and Matilda thanked the shop keeper and returned home with their smaller sheet of metal.



WARNING!! - Don't mix cement with ginger beer

It probably won't create acetylene but it might create an exothermic reaction or at least make a sticky mess.



Referring to Engineering Workshop Practice 1956 volume III, we can see that the neutral plane for a bend lies 20% of the way through the sheet. Everything on the inside of that will be under compression and everything on the outside will be under tension. We can use this to calculate an allowance for bending.

Bending Allowances from Engineering Workshop Practice Volume IIIBendingAllowancesFromEngineeringWorkshopPracticeVolume32.jpg

The formula for calculating an allowance for bending when the measurements are on the outside of a joint are as follows:

L= A + B - (2 * 0.8)T


if the measurements are made on the inside of the joint then it's

L= C + D + (2 * 0.2)T


Based on this Matilda sketched a design for the battery box that could be folded out of the metal the golem had cut for them.


A box was built based on the sketch and above calculations and the battery fitted perfectly. However, the cable was too short to reach the power board.

Battery Box V1

So a redesign was needed, the side was taken off and it was re-drilled.


The rear basement had already been extended to allow for the size of the stack of Arduino and shields. The charging circuit and boosting circuit was moved slightly and the battery and cable now both fitted. The main board was fitted to ensure that there was clearance for all the connectors and that the battery could be removed without needing to disassemble the boards.


Some of the cabling was also started with some cables for the LED power and LED made up and a cable for the power also soldered up. The protoshield was wired up with headers for the servo and power supply, for the cables that were undecided they work left long and wrapped over the side of the board. A space was left in the middle of the board for a power mosfet to turn on and off the servo and lighting board.


A productive if not particularly technical week for the project. Next up some more coding and power management and after that if time permits there's still some further enchantments to be applied.


Next: Enchanted Objects Design Challenge - Sleeping Golem