Thursday, 17 July 2014

Gate modification

We recently agreed to look after a relative's dog for them and realised that we needed to make a few changes to accommodate the dog safely. One of these was making the back garden gate so that it would not be easily jumped over.

I had difficulty removing the screws holding the hinges. The gatepost was not actually attached to the ground simply screwed into the fence so I remove the gate and post together.



I ended up drilling out the screws as they could not be shifted, even after repeat soakings in WD40. We'd decided to replace the gatepost with a taller one. This turned out to be a good choice as the post was pretty much rotten.



I dug a hole for the new post and used a broken crowbar and a bolster to chip through 4 inches of concrete. I don't recommend doing it this way as I managed to hit my hand with the hammer a few times. SDS drills don't cost much so next time I'll get myself one of those.



The new post was concreted in using some concrete I'd had left over from another job. This was not sufficient so I topped it up with some postcrete.





The gate was extended using two 50mm "fence posts" a batten across the top and some willow screening. The old grot and paint was removed with a pressure washer.



The framework of the gate was sawn down to make space for the posts. I drilled and chiselled a mortise in the top of each post and simply slotted the cross bar in place. The uprights were then screwed to the frame of the gate.



The willow screening was then attached using some heavy duty U shaped staples. You need to be very careful with the willow as it's so easily broken. The final steps are to give the gate and gate post a coat of preservative and to screw the gate back onto the post.



Friday, 11 July 2014

Spacers

A simple but important part for the clock was the spaces that connect the two clock frames together. These were a simple machining job, brass rod was faced off and drilled with a 2.3mm drill. It was then parted off in 15mm lengths.

The parts were rechucked and the parting off pip was then faced off. Finally the parts tapped with a 3mm through tap. The same technique of tapping in the 4 jaw chuck as used for the bush was used for the spacers. A pipe cleaner was used to clean out the threads before testing with the brass screws.



When assembling I found one of the threads was a bit tight so I ran the tap through it a couple more times. I discovered that a large tap wrench is a good holder for small round part.



Monday, 7 July 2014

CapSense Switches

As a little side project, I've been looking at some capacitive touch switches and their suitability for workshop projects. Element14 and Cypress Semiconductors kindly provided me with an evaluation board for the CapSense MBR3 switches as part of the Element14 roadtest programme.



As preparation for my roadtest report I've been writing up some blog posts on what I've discovered so far.



Tuesday, 24 June 2014

Small screwed bush

The next component to machine was one I like to call the "Top Hat". It fulfuls two purposes, it holds the clock mechanism to the face of the clock and it acts as a bush to support the spindles that drive the hands of the clock. I made a special clock opening tool to remove the existing one with the intent to re-use it. However it had an uknown thread on it and rather than go to the effort of working out what that was and then trying to buy a suitable tap set I decided to remake it.

Before I could start I chiseled the back of the clock to fit my new plates. I then had a look at my taps and an 8mm x 1.25 seemed the most appropriate. The plate had already been drilled and the brass was easy to tap.



I selected a bronze bar as I had some in stock. I started by facing the bar and drilling the hole. I then turned the the outer diameter down to 7.5mm on the lathe. I estimate this size based on measuring the tap as I did not have a suitable chart to hand. That's definately a mini project to source and print the data as a quick google failed to find the information. When it came to cutting the thread I used a 4 jaw chuck to securely hold the part and held that in the vice.



I did not really think out my machining sequence and after a near disaster I ended up having to saw the bar to length and file the head. However the end results turned out ok.



Here's the part in for a test fitting. I still have to cut the slot so it can be screwed in from the front. I will likely do that with a cutoff disk in my mini-drill but I might have a practice first on some scrap.



Tuesday, 17 June 2014

More clock shafts

After my previous success drilling a tiny but deep hole through some brass rod, I got thinking about how to machine the outsides. Referring back to my diagram the idea was to take a 4mm rod and machine most of it down to 2mm.



But on reflection this seemed like a bad idea so I decided instead to start with a thinner rod and add a bush to mount the gear wheel. I found some 2.4mm copper coated welding rod. I initially tried machining the copper coating but the rod was bending in the lathe and did not produce a good finish. However I discovered that the soft copper coating was quite thin and was easily removed when polished with some emery cloth.

A brass bush was drilled and turned so that it was a tight fit on the welding rod and also a good fit for the plastic gear.

Here's the redesigned shafts, the lengths have still to be determined.



Thursday, 12 June 2014

Pepper's Ghost

A few weeks back my 3 year old daughter gained a "Sooty" magic wand on the front of a magazine and has been trying to make things appear and disappear ever since. To help her "magic things" I was thinking about self working tricks. Initially I thought about some high tech solutions such as something that would respond to 3 taps of the wand in a similar manner to this secret knock detector.

However, I then remembered the old "Pepper's Ghost" trick which is an optical illusion which can make people appear and disappear simply by changing the lights. I borrowed some ideas Übernotes from to build one.



We created the effect by painting the inside of an old teabox with black poster paint. When it was dry a door was cut in the front and a flap in the top. we also added part of a fahita box for a roof.



After a quick trip down the workshop to cut a piece of perspex, we added that in with some whitetack. Finally a figure was added on the right of the box.



All that was left was to shine a torch through the hole in the top. Here's the effect in action.


Monday, 9 June 2014

Robot Kit

The HapPi-Robot is a lightweight solution to get you started with turning your Raspberry Pi into a robot. The range consists of a series of Case4-Kit cases, a H-bridge driver board and mechanical parts kit to get your robot moving.

Lewis Wass and Steve Bloye from The Little British Robot Company told me all about their project.



Workshopshed: Chaps, thank you for agreeing to be interviewed. The other Pi cases I've seen are acrylic or laser cut plywood, why did you choose cardboard?

The Little British Robot Company: The usual acrylic case and chassis offered by other companies are fine but rather expensive, are hard to modify and are quite heavy.

We use Kre8® SuperSheet a new ‘making sheet’ material we have developed to provide the properties required for making rigid forms at a lower price than acrylic or wood.

Kre8® SuperSheet is made from four layers, each with a different property, glued together providing a surprisingly rigid, good looking, lightweight 3D form when assembled. The attractive protective top glossy printed surface also acts as a hinge when sheet is folded and makes assembly (and disassembly) fast and easy, without the need for glue or nuts and bolts. Robots made from acrylic can break when dropped on the floor. Kre8® SuperSheet is more robust and gives good protection and does not shatter if dropped. Wood is hard to decorate is not to everybody's visual taste. Both acrylic and wood cannot easily be folded to produce 3D forms.

Workshopshed: Do you need to remove the Pi from the Case4-Pi when you are not using it as a robot or to program it?

The Little British Robot Company: No. The RaspPi once inserted can be left in the Case4-Pi as all connectors and the SD card slot are accessible.

In use the Case4-Pi can be used with or without its lid which can be used to

a) act as a normal fully enclosed lid or b) act as lid with an opening so RaspPi add-ons can be accessed or c) to provide a place to assemble a circuit on top.



Workshopshed: Why does the Pi need a H-bridge driver board to run motors?

The Little British Robot Company: To prevent the the Raspberry Pi burning out and allow robot steering. Motors require more power than the RaspPi can provides safely and for robots need to be reversed.

The H-bridge chip used can control two dc motors in forward or reverse or can used to control four dc motors with just on /off. Robots need to be able to reversed so this chip is ideal enabling a robot to move:- forward, backwards and spin fast or slowly assuming a program such as ScratchGPIO is used to program it.

Workshopshed: What else can you use the board for?

The Little British Robot Company: Besides motor control the HapPi add-on board provides access to all the connectors including the GPIO pins, camera connector etc and also includes three protected inputs so switches can be connected directly without need for extra protection resistors. It also has a i2C connector for more advanced work.

The HapPi add-on can be used to do just about anything as it can use all the features the Raspberry Pi but also adds robot motor control. Extra circuitry can be added as needed using jumper leads as commonly used with breadboards.

Workshopshed: Is there support for the usual programming environments such as scratch and python?

The Little British Robot Company: Stewart Dunn who has written various school textbooks is producing a support website at www.pi-school.com. The initial focus will be on using ScratchGPIO to control motors, robots, traffic lights and various practical fun activities for use schools.

An easy way to get started is to use ScratchGPIO but more technical users may prefer Python but other languages can be used id supported by the OS community.

Workshopshed: Who are the kits aimed at?

The Little British Robot Company: For anybody who wants to extend the use of the Raspberry Pi by making use of the GPIO pins to make things work in the real physical world.



Workshopshed: How do you see schools benefiting from having robots in the classroom?

The Little British Robot Company: It brings excitement into the classroom and can be made suitable for all ages and abilities. The knowledge gained can be applied to may problem solving activities. The Raspberry Pi is a full blown computer suitable for beginners right through to university level. RaspPi Robots allows open-ended-learning to take place at any level.

Workshopshed: Thanks again for taking time to talk to me and good luck with the project.

Case4 Kits and HapPi-Robot

Workshop Practice Series