Diary and thoughts on setting up and using a small shed as a workshop. Using and improving metalwork tools such as a pillar drill and small lathe. Home foundry work melting aluminium in a flowerpot furnace.
The purpose of the MCB (miniature circuit breaker) is to turn off the power to a circuit when the current limit is exceeded. The reasons to do this are to stop the wires or appliances setting on fire when there is a short circuit or overload. The short could be caused by a person touching the live circuit in which case we'd want the circuit to shut off pretty dammed quickly.
In the workshop environment the most cause of an overcurrent situation is when the lathe or drill stalls on something, this causes the motor to draw significantly more current. But it could also be when you hacksaw through the a live cable because it was hiding under your work piece (a good reason to have a tidy workshop).
Anyway, to summarise what I'm saying, it's a good idea to have MCB's connecting up the power in the workshop. For a similar reason a RCD is also a good idea, see article on workshop electrics.
The IET brought to my attention that there are some counterfeit circuit breakers. These are just shells from MCBs with a shank of copper wire where the circuit should be, the modern equivalent of a nail across the fuse. It should be theoretically possible to spot them because they will be lighter than the real ones but if you are not used to handling the real ones then it could be easy to mistake them.
So if someone offers you some cheap MCBs in the pub carpark then it could save your life to "just say no!"
"Can you make me up a 38mm washer with a 19mm bore", said my father, "in 3.5mm stainless steel" he added.
My first problem was finding a supplier for the stainless steel. I quickly discovered that I was not going to be able to get a 38mm round bar and that sheets did not come in 3.5mm thickness. There were suppliers of 3mm sheet (mostly 1m by 2m). I checked with Dad and he accepted that a 3mm washer would work. Also whilst looking for the suppliers I found that there were different grades of stainless available, my Dad suggested 316 which is the favourite for marine stuff items, I found someone who could supply an offcut of a size that I could use, MetalsDirectUK on ebay so luckily I don't have a workshop full the the brim with stainless steel sheet.
I knew that I was going to have to bolt this to a makeshift mandrel of some form as I've still not worked out how to remove the lathe's chuck to swap it for a faceplate. I've nothing to clamp it with yet anyway so I'm not sure if it would have been a better solution.
I tried a technique from a Model Engineers Work shop 136. In an article by John Slater called "Making Solid Swarf" he described how you can use trepanning to cut a circular slot through your metal. For me it did not work, too much chatter and a tendency to jam, possibly did not help that I was working right on the edge of the metal. After 30minutes and only 0.5mm through I abandoned this technique. I'll definately give this another go if I have any brass or aluminium plate to machine.
The wooden mandrel I was using also was causing a problem with slippage and movement. This may have been the cause of some of the issues just mentioned. I swapped to an aluminium mandrel made from some scrap from another project. The stainless steel was roughtly sawed in to a round and then used a more convential turning technique to cut the outside.
This did the job nicely so I drilled and bored out the centre to the desired size without incident. Care is needed not to try to machine the chuck jaws, the lathe provides a little bit of clearance in the middle but if you slip then you could be into the jaws. You also need to be careful with clamping large items in the chuck as the jaws will catch the bed if you open them up too far. I like to give the chuck a spin before starting it up so that I know it's not going to catch.
The stainless steel is not actually too difficult a material to machine, I found that I could be quite agressive with regards to how much metal could be taken off and this did not affect the finish. Lots of coolant was used so it was a big clean up job afterwards. The opinion on the web is that the 300 series is not a problem but the 400 series is a bit of a pain.
I've popped the washer in the post, I've no idea what it's for so I'll be following the Honey Bee / Crunluath blog to see if it gets a mention.
The Society of Model and Experimental Engineers have issued their Low Energy Challenge, SMEELEC. The requirement is that you use a low energy supply to store up energy then release it to raise a weight as fast as possible. There is an electric challenge (button cell) and a thermal challenge (candle powered). The idea sounds simple but the entrants will have to produce an efficient and powerful machine to win. Slightly above my level of skill at the moment but it will be fun to go and watch.
The competition will be run at the Model Engieering Exhibition this September at Ascot race course. Details of the competetition and entry forms can be found on the SMEE website. http://www.sm-ee.co.uk/
On a less serious note, students from Purdue University's Society of Professional Engineers won the 2008 Rube Goldberg contest with a device that requires 156 to assemble a hamburger. Rube Goldberg is the USA's equivalent to Heath Robinson.
The changes to the UK electrical regulations made in 2005 are designed to reduce the number of people electrocuted by their own incompetent wiring and to eliminate cowboy electricians. The "part p" regulations basically specify that a competent person (electrician) should install and self certify your shed wiring. These notes are here to help you plan and discuss your requirements with an electrician and hence not over engineer or under engineer your workshop supply and to avoid unnessary work by making the right choices.
Please note that other countries may have different regulations and these regulations may change.
Regulations Q: What are the regulations for? A: Part P schemes should ensure that electrical work in dwellings is designed, installed, inspected and tested to the standard required by BS7671. The regulations are British law, not just guidelines.
Q: What if I ignore this law? A: You could be fined upto £5000, be required to remove your or have your work altered and if you sell your home the purchasers solicitors will require you to have certification for work done.
Q: Why does this apply to my shed or workshop? A: The regulations apply to a building or garden that receives its electricity from a dwelling. So if you powered your shed from a wind turbine or from batteries then you could in theory do the work yourself but you might then find that you are affected by a whole raft of other regulations...
Q: What about modification of an existing setup? A: The regulations apply to major involving one or more complete new circuits. You can complete non notifiable work such as changing a socket or adding lights or replacing a damaged cable. Check the regulations as there are exclusions for these works meaning some things must be done by an electrician, these include kitchens, bathrooms and gardens.
Q: What if I still want to do this myself? A: This may be possible but you will need to discuss it with your building control office. There are options such as having the building control office inspect you work, however they don't have to accept your plan.
Cabling to the workshop The cabling to the workshop is typically connected to a spare way on your consumer unit and then via special cable to the workshop, it is buried in the ground. A warning message on a tape is buried on top of the cable.
Q: What kind of cable is used? A: An underground cable needs to be protected. Typically this is done with a steel armour around the cable. The cable requires special glands at the ends to terminate the armour.
Q: How deep should the cable be buried? A: This depends on the your circumstances but is typically 18 inches. If you are putting the cable below flowerbeds or a vegetable patch then you may wish to go deeper and/or provide additional protection to the cable. Special considerations may be required if your area is populated by burrowing animals or rodents.
Q: Is there a maximum distance? A: Yes, the distance is determined by the current requirements the size of the cable and the allowed voltage drop. Your electrician will work this out for you but to put it simply, you will need fatter cables the further the distance and fatter cables to supply a higher current. Most workshops / gardens should not have a problem but if you are supplying high currents over 50m then you may have an issue.
Q: I don't have any spare capacity in my home's consumer unit, will I need a bigger one? A: Not necessarily, the electrician may be able to spur your supply from your ring main.
Q: Can I put other items such as network cables in the same trench as my electrical cable? A: It is recommended that you have your network cables at least 15-20cm away from your power cable. There is a version of Cat5 cable that can be directly buried or you can put it into waterproof PVC conduit.
Cabling in the workshop Q: What kind of cables are used in the workshop? A: The same as in the house.
Q: Do the cables need to be put in conduit? A: The wires need to be physically protected, in a house this is normally by keeping them inside the walls. In a workshop this may not be possible hence you need to protect them with condit or by routing the cables away from the areas of any work. Please note that if you use metal conduits then you will also require additional earth bonding to be done.
Q: Once the workshop is wired up, can I make my own modifications? A: The regulations still apply so you can only make non-notifiable changes, see above.
Q: Do I need an RCD? A: Yes, your electrician should provide one either via a socket or in a small consumer unit. Q: I don't want the lights to go out when my supply trips. A: Hopefully your supply won't be tripping if it's setup correctly but it's possible for the electrician to add a small consumer unit in your workshop so that over current problems with the sockets won't trip the lights. Be aware though that tripping the RCD on the workshop may also trip the RCD on the house, this is typically unavoidable.
Q: My workshop is steel framed or I have pipes / large metal items in the workshop, do I need to advise the electrician? A: Yes, this will require extra work as they will need to earth bond these items. Small portable appliances such as a power drill should not need bonding, larger lathes and mills will likely need earth bonding.
Q: I'm thinking of buying a large machine will this cause additional issues? A: Yes, an inductive load such as an inductive motor can affect the power factor of the supply, this will have potential effects on the your workshop supply such as increased voltage drop over the cables and increase your power consumption. This can be resolved with additional components called Power Factor Correction which are typically in the form of capacitors added to the circuit.
Q: Can I use an extension cable? A: It's acceptable to use an extension cable for temporary use or for portable tools but not for a permanent installation.
Q: My drill/lathe/mill advises using a slowblow fuse but I've got MCB (minuature circuit breakers), what do I need? A: There are different types of MCBs, advise your electrician of your requirements and they can fit a type C or other appropriate breaker.
Three Phase Q: My lathe/mill is three phase how can I supply it? A: You have a couple of options with regards to three phase supplies. If you have a large workshop then you could spend a lot of money and get the supply company to provide you three phase to your property. The alternative is to get a box called an inverter.
Q: What's the choices for inverters? A: There are different kinds, some can vary the output hence providing speed control. Static inverters or capacitors can make your equipment work from a single phase supply but are not really powering all phases. The alternatives generate the other phases either using clever power electronics (digital phase converters) or via a small motor and switches (rotary phase converters).
Q: What factors should I think about? A: Things to consider, cost, speed control, current, space requirement, number of devices to be powered.
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but there are also many simpler guides to the wiring regulations.
