Hose connectors are problematic, I am going to investigate designing a laser cut acrylic stack to make an air tight ‘printable’ connector however most hoses come as an assembly and the connectors are custom moulded parts, I could however use a hose clamp and some ridged PVC from a plumbing store, but the aesthetic might let the product down.
Finding alternatives to motors is difficult because the motors used in vacuum cleaners are specialised for their job, they rotate at high RPM and are designed to cool themselves through the airflow they produce. Buying a motor to spec from a supplier might work for this first prototype but it is not sustainable as more people build their own open source vacuum cleaner.
So, the problem is also that anyone selling this type of product is going to be selling it in large volume for manufactures of vacuum cleaners. This doesn’t leave much option open for actually buying a motor and other types of motor are likely to be inappropriate for the task and suffer similar issues of quantity, but is there another way?
In recent years the growth of online spare parts suppliers means that it is now relatively easy to obtain a service part for almost any modern vacuum cleaner. The trick is that the motor it takes needs to be a popular one, i.e. one that is likely to be around for a long time, such that the project isn’t held at the mercy of the manufacturers obsoleting the product by discontinuing spares, even better would be a product that has third party substitute parts, however this is unlikely given the safety concerns of mains power and high speed mechanical parts.
An obvious choice would be to look at the popular products of the main manufacturers:
I am in discussion with a website called eSpares to find out what the most common parts are and therefore what are most likely to last the longest.
The handle part on the end of the hose will consist of three parts, a tube bent to a comfortable angle. A hole with plastic insert to allow control of the reduced suction mode. A hose coupling on the end.
There are two standards for existing tools on the market. 32mm and 35mm. It makes sense to use a universal size rather than a bespoke one. The handle is the least of my concerns at this stage.
Hose types Suction hose is a special type of plastic hose, usually made of PVC that is designed to allow a vacuum force inside the hose to pass without the hose collapsing. This is achieved usually through the use of a continuous ridged metal or plastic spiral embedded in a flexible plastic extrusion.
Other types of suction hose found commonly in cheap vacuum cleaners use moulded rings along the length of the hose to provide strength whilst the caps between allow flexibility. These cheaper hoses tend to break due to the stresses on the more ridged plastic, and the tear in the plastic tends to run all the way around the ring until it falls off and is essentially unrepairable.
Repairability PVC spiral suction hoses are still susceptible to breaking because the flexible plastic structure linking the spirals can tear or be punctured causing a tear along the spiral down the length of the hose. This is almost as unrepairable however due to the distance between the spirals it is sometimes possible to repair these.
One of the key issues in favour of the cheaper plastic hose other than cost is that if the damage occurs near the end of the hose, as is common due to the stresses at these points, it is normally possible to unclip the hose connectors, cut the end of and re-clip it leaving a slightly shorter but working hose. The more expensive spiral hoses however are quite hard to cut due to the ridged embedded spiral and the difficulty in cutting a straight edge through a spiral. Either way the most common factor preventing repair is the one use nature of many of the compression fittings used to at either end of the hose, clearly an area for improvement if at all possible.
Length Another aspect to consider with these hoses is their length, most hoses are about 1.5 to 2.5 meters in length, the length makes a big difference the usability as it allows you to walk more freely with the vacuum cleaner dragging behind. Length also affects the power of the machine and can cause it to be greatly diminished if it is too long, due to the suction acting on the host trying to crush it rather than pulling in material from the end. Also while many hoses are smooth internally there will still be bumps and the contour of the bends that restrict the airflow.
Internal diameter One final aspect is the internal diameter of the hose, too small and the airflow will be restricted, too large and the airflow will dissipate. An average hose has a 25–45mm internal diameter.
Materials The inside surface of any hose should be smooth as this will prevent clogging and build up of dust and other materials, investigating a transparent hose would be an idea as it allows for a clear view of any blockages, especially from brightly coloured cat toys…
Solution So what is the solution then? I have found numerous companies selling hose for suction of dust and air, I haven’t managed to find one that sells small lengths however I am hoping they will help me out.
The power switch in this product will be important, it needs to be rated for 240V at least and a good 10A. I am keen to use a decent quality switch as again this isn’t about building the cheapest vacuum cleaner but a decent one where you can make it your own way. With this in mind I have considered many options including those with little lamps but I think a switch like the one picture is best as it clearly shows which mode it is in and the bulb can’t break as it doesn’t have one. This switch is mains rated for 10A and has blade connectors making it a simple job to replace as it is a clip in design. I need to ensure the switch cannot pop out by accident however!
The subject of how to move the unit around is a difficult one, it needs to be quiet, not prone to leaving marks or collecting dirt, easy to move over many types of surface, and designed to be removed for permanent installation in smaller spaces.
In the situation where it will have wheels it would be ideal to have four swivel wheels as these make it hyper mobile like a fighter jet, unlike a fighter jet it will not however have a flight computer to compensate for the jittery controls and may need a rubber bumper for crashes.
Castor wheels are a good fit as they come in a variety of standard sizes and usually have a flap plate fitting which would be easy to remove or replace.
The issue with wheels is that they can pickup dirt and leave marks when dragged, it would be important to ensure they didn’t have rubber trims as these are most likely to pickup dirt and leave marks.
Something made of a hard plastic would be good as even if the wheels bound up they would have very little friction over the surface. They aren’t necessarily the quietest however.
A solution without wheels can be fraught with problems too as the bottom surface could more easily scratch due to the focus of weight in one area, a hover craft solution like the Hoover Constellation was a classic example of this, floating just enough to lift its weight off the floor and not to much that it was free from the carpet and therefore sliding all over the place due to lack of carpet friction.
A solution with a very low centre of gravity that has a very polished base like a russian doll could work, however dragging it over the hard floors would be horrible.
Another solution to revert back to is the backpack vacuum cleaner, this solution is questionable because modern vacuum cleaners kick out a lot of heat and may be uncomfortable to wear. Equally carrying it in one hand means you cannot give the carpet a good scrub with the tools.
The solution seems to be some decent quality hard plastic swivelling (not fixed) castor wheels, the key is finding wheels that aren’t massive but clear the carpet.
The last thing I looked at was the power cord, but equally important is the plug and it’s fittings, strain relief, etc…
Unfortunately power plugs don’t seem to be so much of a fashion statement as the fancy chrome plates sockets, and fabric sheathed cables that adorn them. This means that most plugs are just ugly plugs, but there are a few clever ones out there which a maker might choose over the standard cheapie.
Most plugs in UK high street shops seem to be manufactured by Masterplug, so there is a rather limited and duplicated set of products from various suppliers including, Homebase, B&Q, Screwfix, and Robert Dyas.
Masterplug have three ranges of standard UK three pin plug, the first is their heavy duty model (HDPT13), which is available in black (HDPT13B), white (HDPT13W) and orange (HDPT13O). It is 13 amp rated and as the picture shows, it has a chunky rubberised finish with good side grips. This retails for £3.
Next up is their rather ordinary looking PT13 model which as you can see comes in black (PT13B), or indeed white (PT13W), which seems to be the most common in the shops and retails for £2, it has a glossy finish and is very plain and cheap looking.
The last in their product line is an interesting one as it has a special grip at the back to make it easier to remove. PT13H comes in white only (PT13HW) and has the same cheap nasty glossy finish as the PT13 but has a ‘ring pull’ to make it easier for those with difficulties gripping to pull it out, especially useful if the pins get bent as can happen sometimes. It retails for about £2 also.
The Other End
At the other end of the cord will be a connector as well, as there is no cord retract on this model it makes sense to make it easier to put the cable away at the end of use, or to help routing it around things for a more permanent installation in a makers shed. What we commonly think of as a ‘kettle lead/cord’ actually has a far more boring, but technical name… ‘IEC 60320 C15’.
To break down what IEC 60320 C15 is I did a bit of research… IEC stands for ‘International Electrotechnical Commission’ who are a body who deal with the specification of international electrical standards to make things more compatible. IEC 60320 is one such standard, specifically it is for a non-locking electrical power coupler, i.e. a socket and plug for powering devices. The specification is specifically designed for home and office use, as it specifies sockets for up to 250V @ 20amps (in some cases).
Within the IEC 60320 standard are a number of different types of connector for different purposes, from your traditional 2 pin electric shaver C1/C2 coupling rated for a mear 0.2 amps, a three pin cloverleaf shaped laptop power supply C5/C6 coupling, and the widely used figure-8 connector on a radio called C7/C8. Through to the even more common C13/C14 connector used on a home computer and the confusingly similar C15/C16 connector used on heated appliances especially older kettles, where the difference is simply the maximum temperature the cable assembly is rated for, and a small notch to prevent a ordinary C13 plug being coupled with a C16 socket where the heat could melt the plastic of the C13 plug leaving exposed live wiring, or shorting out whilst powered. At the top end there is even a C19/C20 used on the back of a Mac Pro and other high end computers mainly, which is used for high power appliances where a traditional C13/C14 assembly wouldn’t support the current requirement.
There is an interesting part of this IEC 60320 standard which is that C17/C18 are actually two pin versions of the common kettle cord, and among the many places such as Xbox’s they are commonly found on vacuum cleaners. Indeed some commercial/industrial use machines have this, and vacuum cleaners commonly aren’t earthed as they produce so much electrical noise and have no exposed metal surfaces to ground. The C17/C18 coupling isn’t easy to get hold of and is pin compatible with a C13 cord, but not the other way C14 and C18 because this would leave the earthed product unearthed.
It would seem logical to make use of the vertical right angle plug, or horizontal right angle plug in this design to avoid it being pulled out by accident, the cable could come down along the body of the vacuum cleaner and through a metal retention clip like below:
I had thought that it would be good to have a cable retract and that may yet still happen however the main focus is the vacuum cleaner, the power cord rewind is secondary. I would also quite like to investigate an audible alert mechanism for when the retract is pulled out to its limit as the yellow and red tape indicators aren’t particularly obvious.
I would still like to use an attractive cord, indeed the whole point of making your own vacuum is you can make it your way. I am looking at using a fabric sheathed cord. I have looked at samples from FabricCable and I quite like the black and white striped cord, however their products are apparently only rated for lighting appliances so I will have to speak to an electrician about whether I can use it for a vacuum cleaner safely.
UPDATE: Looks like they do sell a power cord for appliances but it’s a number of times more expensive here.
This weekend (Sunday 6th January) I held a workshop at The Rag Factory, Bricklane, East London. I invited strangers to attend this workshop as a way to kickstart the process. Though the workshop we started with introductions, it turned out that we had:
Barry – Mechanical Engineer/Designer
Gangj – Product Design Student
Jeffrey – Electrical Engineer
Oliver – Interaction Designer
The mix was male orientated, and all had some relationship to the Royal College of Art, although they were not all derived from contacting students. I guess the project appeals a certain type of person?
Anyway next we talked about the idea behind this project, and its founding principal which is that I wanted to examine what happens when the concept of The Maker’s Bill of Rights, Open Source Hardware, The Fixers Manifesto and the general maker/crafter philosophy is applied to the design of every day items, specifically in this case a vacuum cleaner.
Next we watched an episode of Tim Hunkin’s TV series, The Secret Life of Machines, this episode was dedicated to the vacuum cleaner.
After this we started talking about some of the current models of vacuum cleaner, and produced a reasonably extensive plan of those products:
One key issue the group came up with at this point was ‘Who is this vacuum cleaner for?’ The issue is that the vacuum cleaner isn’t designed for mass production, nor to compete on price, and it’s designed by amateurs so it probably isn’t going to be a better vacuum technically than existing models, so what makes it worth building? The answer we came up with was, that this vacuum cleaner might be made by makers for makers because realistically not many people would feel confident enough to make their own, nor would they want to bother with that. So went about plotting what alternative uses we could think of that the vacuum cleaner could serve in addition to the existing role as a cleaning device…
Next we started looking at the two vacuum cleaners I had brought along to dismantle and examine, the first was a £29.99 model from Argos (406/7946). Unfortunately the vacuum cleaner was not designed to conform to The Makers Bill of Rights and so although it had standard Phillips head screws they were at the bottom of a very deep and tight hole so we couldn’t get the driver down to them.
To add insult to injury, I had bought a special kit of long security torx drivers as I researched the Dyson we had to take apart and found it used these so as it turn’s out aren’t nessisary on the Dyson as they are all flush with the surface, while the short screw drivers I already had for the Philips and flat head screws didn’t reach quite far enough to open the cheap Argos vacuum cleaner.
We did however take some measurements of the vacuum cleaner at three key points to measure airflow fall off and allow us the make some basic comparisons to the outcome of this project, obviously we did this before trying to take them apart incase it all went tits up.
The three points of measurement were, direct from the motor, this measurement was difficult as the port is larger than the anemometer vane we used to measure it. However the ‘after filter’ was the port on the outside of the machine after filters/bags/cyclones where the hose would normally connect. The hose measurement was the result airflow at the end of the hose and the bendy handle bit.
Interestingly the Dyson doesn’t really loose airflow speed thought this process but the Argos clearly does as the filter impedes the airflow. Next we unpacked the brand new Dyson DC11 for it’s ‘inspection’…
We performed the same set of tests on the Dyson:
We even used polystyrene balls to visualise the cyclone power, it turns out that even though the Dyson is very powerful and cyclone-y the Nikon D7000 can still capture a still image in mid rotation:
Now we start on the interesting bit, the disassembly, a dark day for this vacuum cleaner, would it ever work again?
The first step was to remove all the ‘accessories’ that come off by design…
Strangely the mechanism that Barry is holding there in his left hand actually comes of using a plastic screw, as though it is intended for a user to service but only reveals the life time filter which cannot be removed without full disassembly, we could only presume it aided in cleaning the hose or user replacement of this part as it gets a lot of abuse.
This is where the investment in the T15 Torx driver came into it’s own as every other screw in the machine was a T15 (except one T6 I think). The first part off was the accessory storage bay (above), then the hose clamp/cable guard.
With a half dozen more screws removed we could lift the lid on this beast, and discovered a rather modular and serviceable machine, not unsurprising when Dyson have to service these themselves. The base comprises of three modules, the cable retract mechanism at the front there, you can see the upside down Y shape, that is the break release button. Behind on the right is the lifetime HEPA filter, and to the left is the motor canister, and that is it!
Here you can get a closer look at the base, and see there is a PCB module on the motor canister, which wasn’t surprising as we had already turned the machine on and discovered that it seemed to be a soft start on the motor (where it ramps up power), we also noticed a green LED which seemed to flash for some time whilst it did something before going to green to indicate it was ready, also the power button didn’t operate for short taps but only longer presses.
To our surprise the motor seemed to be Dyson’s digitally controlled motor, or brushless as the resident EE described it. The motor had phases, each attached to a transistor, through a opto-isolator to another, larger PIC microcontroller which presumably is connected to the power board and it’s radio transmitter chip and antenna.
Barry, the product mechanical engineer got a bit carried away disassembling it and ended up dismantling the entire motor, we learn’t however that the motor has an optical encoder to detect the passing of a cam on the motor shaft, to presumably measure RPM.
Jeffrey the Electrical Engineer got rather excited by the electrical aspects of the product, noting some interesting polyester capacitors and gigantic diodes in a full bridge rectifier converting the 240V mains AC into about 300V DC although he presumed it was not powering the motor at that power through the transistors.
Here is the back of the board, the larger chip in the bottom right is (I think) the PIC.
How does this go back together?
The extracted power switch board, come radio bug thing, strangely it was noticed that in addition to the antenna bit, there was a tri-colour LED which we only ever saw green, but also presumably was able to do Red and Yellow. There was also a buzzer which never buzzed, and both boards had what was presumed to be a reset switch for the PICs, a small ribbon cable connector acted as an interconnect between both boards.
We ended up with a discussion about where we are now, recapped the mission of the project and had a great suggestion about using the exhaust of the motor to blow back into the carpet pile to loosen it before sucking it back up again, this would also allow for a ‘closed loop’ of dust to create recirculate any last particles in the air through the vacuum filters again, and again.
Long post, long day, and lots learned. Some how I am struggling to figure out what the next workshop might entail, however myself and the others agreed it was a great start to the project and my tutor doesn’t currently see what can been gained from another workshop, I wonder if another might be a test build to see how others get on with building the final version, however that would be in February.
I will leave this post with a time lapse of the whole day…