A Driving Instructor's Blog


Cheap wooden kneeling chairAs well as being a driving instructor I also do a lot of work on my computer (websites, programming, and so on). So being comfortable is very important.

I’ve used all sorts of chairs over the years, and ones with arm rests or which tilt drive me nuts. I’d much rather sit up straight. So for some years now I have been using one of those ergonomic kneeling chairs, as shown in the photo above. I find them very comfortable and versatile, but the ones I purchased have all had serious quality issues. It’s not surprising when you consider that the most expensive ones can cost upwards of £1,000. Spending around £50, like I did, was bound to raise questions.

The first two I had were made of wood, In spite of getting them from different suppliers, it was obvious that they all come from the same place of manufacture. They were identical to each other, and they both had the same eventual problem. To start with, no matter how well you assemble them (they’re flat-packed), the screws work lose and they start to squeak. For a while, re-tightening works, but eventually the threads will not grip and the movement gets worse until there is an actual wobble. Eventually – and it doesn’t take that long – the wood splits due to the movement and the chair is unusable. Furthermore, even from first use, it is quite possible for one of the castors to fall off while you’re sitting on it or moving it.

In desperation, the third one I bought was more expensive and made of metal. I thought that a metal chair would be indestructible, but I was very wrong indeed. It was clear that the metal version came from the same original source as the wooden ones. Now, that shouldn’t have necessarily been a problem if the metal box sections used had been sturdy, but they weren’t. To keep costs down, the box section was made from a light gauge of steel, and although it was less flexible than wood, this rigidity meant that stress was concentrated across a very specific area near the seat. After about a year I could detect movement and when I checked, the metal had simply cracked.Fairline arc welder and Black and Decker angle grinder

Anyway, like with most problems I encounter, I started to puzzle over how to get round it. I’d thought about drilling holes and fitting long bolts to act as supports – until I discovered how hard it is to drill holes in mild steel on something that is already assembled. The next thing that occurred to me was welding. I’d never done it before, and my only experience of it was my dad coming home with arc-eye on a regular basis when I was a kid (he was a welder, though admittedly on much bigger things), and I started thinking about hiring a welding machine. But then I found out how small and cheap they are. I picked one up for £50 from Makro. At the same time I also bought an angle grinder for £20 (more on that in a later article).

I got a couple of lengths of mild steel flat bar from B&Q and set about welding some strengthening spars to my rickety chair. This was quite successful and the repair, albeit temporary, was good.

By this time, I had discovered that welding isn’t easy. Not at first, anyway. Striking an arc is pretty simple, but keeping it is a skill. Welding rods get used up very quickly, and it is easy to get one stuck. Welded metal gets very hot, the heat spreads quite a long way through a metal object. Paint is flammable, even when it’s nowhere near the actual weld.

As a result of this article, I’ve had a few hits from people using the search term ‘welding rod keeps sticking’ or some such. This can happen if you are holding the rod too close to the weld – the current is therefore lower, so I guess the weld is cooler and solidifies more quickly, hence the stuck rod. It is even worse if you’re so close that the rod keeps touching the weld, as this can cause the arc to extinguish – also resulting in a frozen rod. Also make sure you are using the right current setting for the thickness of rod you’re using.

But back to the story. The idea of building an ergonomic kneeling chair from scratch had been running around in my head for some time, and now that I knew how to weld, the idea started jumping up and down as well. I found a company called Metals4u on the Internet, and they will supply any quantity of metal you want, and their prices are very good. So the project was set to get going.

The project summary can be found here.

* Note that Metals4U asked me to remove the direct link to their site. As far as I understand it, as well as getting too big for its boots these days, Google also appears to have outgrown its brain and is penalising companies for links to their websites from “lesser ranked” websites such as mine. Their web address is metals4u dot co dot uk


Over the years, I have updated this article several times as I have found progressively better solutions to the problem. I’ve now found pretty much the complete solution.

The problem of smeared windscreens in the rain has been driving me nuts ever since I started driving, but it became a major headache once I started teaching people to drive.Smearing windscreen in rain

I guess everyone has experienced it. You get a few spots of rain, and when the wipers wipe you get a mosaic pattern left behind for a few seconds. But in heavy rain it’s like someone poured chip fat on the screen and you just can’t see properly. I’ve had varying levels of success removing it – scrunched up newspaper (no good), sodium lauryl sulphate (not bad), various solvents (fair), Clearalex (quite good) – but things came to a head when my lease company replaced my last car. In rain you couldn’t see anything, and absolutely nothing would get rid of whatever it was on the windscreen. I was close to assuming that the glass must have been damaged in some way since it was a brand new car.

Where does it come from?

In normal circumstances, every vehicle that uses our roads leaves deposits behind. Some of it is dusty, some is gritty – but a lot of it is oily. That’s why when it rains after a period of dry weather we’re advised to take care, because the road can be very slippery as water and oil sit on top of the tarmac before the oil is eventually washed away. While it is fresh, road spray is obviously going to be a mixture of dirt, oil, and water, and when this gets on to your windscreen you start to get smears. Now, up to a point, your screen wash can deal with it (unless you just put water in your tank, in which case you’ll get smears all the time). Eventually, though, the oil seems to bond to the screen such that removing it is no longer easy.

Another source of windscreen contamination is, oddly enough, washing your car. Even if you don’t choose the waxing option in the car wash, the brushes will be contaminated with wax from people who did, and if you’ve ever noticed how a single fingerprint can be smeared across almost a whole mirror or windscreen unless you use something which lifts it off, you’ll realise that a little wax (or oil/grease) can go a very long way. Even if you hand wash your car, small amounts of wax and oil gets on to your rags and gets spread on the glass. It also gets on to the rubber of your wipers, so it is smeared back on as soon as you use them, even if you got it off the glass. People often forget that the wax (and oil) collects below the wipers, and if you don’t clean that area properly, the wipers dip into it like a pen dipped into ink and spread it across the glass again.

The particular problem with my lease car turned out to be the result of a manufacturing residue as far as I can tell. It’s something that gets on the glass during manufacture, and which they don’t remove properly.

How can you get it off?

Most detergents and surfactants will remove the normal deposits of wax and oil with varying degrees of success, though car wax is particularly stubborn. Even Fairy Liquid works up to a point. Some cleaners are more powerful and are much more effective. You used to be able to buy powdered products like Clearalex in sachets (they sell it in liquid form instead, now), which you add to your windscreen washer fluid. Clearalex works quite well, but leaves terrible white residues when it dries (which I find very distracting). I have also had some success with Sodium Lauryl Sulphate (SLS), which is an anionic surfactant used in many household products. SLS removes quite a lot of windscreen gunk, but it won’t touch wax and it leaves a slight residue when used at the required concentrations. I was very happy with SLS until my recent vehicle change, where I found that no matter how much I used it would not touch whatever was on the glass.

After a lot of research, I found a reference to sugar soap. I’d not heard about this before, but it is used by decorators and builders to remove grease and dirt from surfaces prior to painting. Sugar Soap - from Screwfix

Wikipedia describes it thus:

Sugar soap as typically found in Commonwealth countries is a cleaning material of variable composition sold for use on surfaces affected by greasy or tarry deposits which are not easily removed with routine domestic cleaning materials. When in dry powder form it looks like table sugar thus causing the name.

The solution is alkaline and its uses include cleaning paintwork in preparation for repainting.

It looks like Clearalex powder, and I suspect that there may be some similarities in chemical composition. However, sugar soap is dirt cheap, at about £2 for nearly half a kilo from Screwfix. I bought some, made up a batch using information on the pack, and gave the windscreen a good scrub using it. I rinsed it and took the car out for a run in the rain.

Initially, I didn’t see any difference, but after a few wiper passes the glass was getting noticeably clearer. The sugar soap appeared to have softened whatever it was on the glass and it was gradually coming off. So when I got back home I made up another batch and soaked some rags in it, then left them covering the windscreen (including the bit at the bottom) for about half an hour. I also cleaned the blades with it. This time the windscreen was absolutely crystal clear.

Sugar soap is great for one-off cleaning, but being a solid there is still the problem of residues if you use it in your normal washer fluid.

A while later, I started using a local hand car wash. I was intrigued by how easily they managed to remove every trace of dirt and oil from the car with only a power spray and some mysterious hand-pumped spray guns with various liquids in them, so while they were working I did a bit of snooping and noted the names on the various drums and containers lying around. The important one turned out to be “TFR” – which I discovered means “traffic film remover”. Already this was sounding quite exciting (well, it’s exciting if you’re a chemist) due to theory behind the way TFRs operate.

I bought some TFR from a company called JennyChem. They also supply the mysterious cherry-smelling shampoo the hand car washes use. In a nutshell, a 1-2% TFR solution gets all the oil/wax film off a windscreen in one go, and it seems to also attack the residue I’d been plagued with on my lease cars (I’m getting a new one soon, so I’ll test this out properly then). The same concentration in your wash bottle keeps it off. I use a combination of sugar soap (soaking using rags) and TFR as required, and a 1% solution of TFR in 10% ethanol/water as my screen wash. I also use this solution in a hand spray bottle for spur-of-the-moment cleaning, and for doing the inside window surfaces.

As time has gone by, I have started using the TFR spray to clean my alloys and bodywork in between visits to the hand car wash when I have an upcoming test. It removes brake dust from alloys like all get out, as well as summer tree gum and bird crap (especially when the little sods have been eating blackberries and insist on sitting on the telephone wire right above my driveway).

I’m getting a lot of hits on this now I’ve mentioned TFR.

As a footnote, my hand car wash has just started using what I am assuming is a liquid wax (I haven’t yet identified it) that makes water bead very easily (and very impressively) when it rains. The problem is that it gets on the windscreen, and it is a sod to get off (two sugar soap treatments did it).

Does TFR damage the windscreen?


Does TFR damage paintwork?

If it is the non-caustic type, and if it is used at the manufacturer’s recommended concentration, no. But remember that TFR will remove any wax you have applied, so you will need to re-wax  after using it on painted surfaces. However, removing wax is exactly what you want if it’s on your windows.

Strongly caustic types – which are cheaper and harsher, and often used to shift several centimetres of crap off the undersides of lorries – could damage painted surfaces if used at high strengths and if left on for too long.

The stuff supplied by JennyChem (linked to earlier) is not strongly caustic as far as I am aware, and is specifically designed for use on cars.

Does TFR leave a residue?

The stuff I use doesn’t – well, no more than normal windscreen washer solution does. You’ve got to remember that when you use your windscreen washers, you’re doing it to remove dirt on the windscreen. That dirt is visible, so when you wash it off it will leave visible streaks outside the wiper area when it dries. It’s like when a bird drops a load on the screen – when you wipe it off there’s a good chance it will sit on the screen at the edge until you scrape it off by hand. There’s not much you can do about that.

Is there a non-chemical solution?

A reader (from Australia) wrote to me recently to tell me that he had had success removing that new-windscreen film using Cerium Oxide paste. You can buy it easily from various places (including Amazon) in various forms – powder, paste, or block – and it is specifically used for polishing glass. If you buy it, make sure you get the finest grade possible – ideally, one which is specifically sold for the intended purpose.

Can you put oil on the windscreen to prevent smearing?

Or, as it was put to find the blog, “can u put oil on wind screen 2 prfent rain”? NO. It will make it worse. It’s oil (and suchlike) you are trying to remove. Put it on deliberately and you could end up killing yourself – you won’t be able to see properly.

You can buy things like Rain-X, which are intended to make water bead up and roll off more easily, but those who use it often complain that it is patchy in coverage and leads to worse problems with smearing when the wipers pass over the glass, especially as it starts to wear off. I nearly tried this, once, but the risk of it causing more problems put me off. I’m not saying it doesn’t work, just that not all reports about it are as positive as the advertising is.

My windscreen is smearing when it snows

That’s probably a different thing, and not “smearing” at all.

When the windscreen wiper rubbers get cold, they also get stiff. As a result, instead of flexing to the windscreen contours and bending forwards an backwards on each stroke of the wiper, they snag and bounce across. They may even not touch parts of the screen properly on the wipe. All of this is often accompanied by a horrible grunting sound, and it leaves behind a trail of smeared water.

Also, if there are remnants of snow on the blades, this can leave a trail of melt water as the blades wipe.

There’s not much you can do if it’s really cold except put up with it, or let them warm up as the windscreen warms up. But scrape off any snow or ice and at least you won’t get melt water (and they’ll warm up quicker if they’re going to).


I was surprised to hear that some ADIs have never changed a wheel before. How times have changed.Flat tyre

When I first started driving on my own after I passed my test, I couldn’t wait for an excuse to get the jack out and have a go. Mind you, this was back when just about everyone (who was male) did their own brake pads and stuff on the banger they’d managed to scrape enough money together for in order to save it from the knacker’s yard! Nowadays, I drive a leased car which includes all maintenance and “breakdown recovery”, so it’s really only punctures I have to worry about.

I have to confess that for the first few years of being an ADI I used that free recovery option whenever I did get a flat tyre. The reasons for this were that I didn’t want to get dirty, I hate scissor jacks (my dad was once nearly crushed when one gave way when he was under a car), and… well, if you have a dog you don’t do all the barking yourself.

What made me start doing it myself again was the reliability of the recovery company. I am supposed to have priority service, but if that was the case then I’d hate to have been a pleb who didn’t! On the occasions I have actually broken down, they have turned up in less than an hour once. All the other breakdowns have seen me waiting for between 90 minutes and several hours – and we’re talking about breakdowns in the city of Nottingham here, not the middle of the Sahara. Several waits have been in the dark, and one involved a pupil for whom I had to pay for a taxi to get her home as the wait was over two hours. Yet another situation saw a passing breakdown truck from the same company stop and see if he could help as he was just parking up, but who was then refused permission, whereupon I had to wait for at least another hour – only for a third party contractor to arrive! When you call them, you always got that absolutely bullshit recorded message “we are experiencing high call volumes at the moment”. Every time without fail you hear that, and it doesn’t give you any hope at all that they will turn up within a reasonable time frame.Clarke trolley jack

The last straw came when I called them for a flat tyre about 8pm one summer evening about three years ago and no one was answering, even after repeated calls. So I got the jack out and did it myself. Apart from skinning my knuckles a few times on the tarmac (bloody scissor jacks), and losing about 10lbs in sweat, I changed the tyre in less than 30 minutes.

Next day, I went straight to Machine Mart and bought a Clarke trolley jack (shown above) for about £20. It easily fits in my tool chest in the boot, and I can change a tyre in not much more than 15 minutes without breaking sweat now. I have a torque wrench but my spare tyre is a space saver, so this is academic since I have to get the tyre fixed before I can do further lessons anyway.

I don’t waste time showing pupils how to change a wheel (except when a puncture occurs on a lesson). They’re not paying me to teach them how to do that, and in most cases they have no inclination whatsoever to try it. I would demonstrate it if anyone ever requested it, but no one ever has. However, I do tell them how easy it is, and explain the basics. I also advise them to buy a trolley jack!


My last lesson tonight cancelled due to being unwell, so I finished early. It was actually quite useful, because on Friday the central heating packed in and a plumber is coming out tomorrow now we know it is the the boiler (Ouch! £££) and not the pump.

Very ColdAs I mentioned in the previous post, it was -9ºC again this morning. It never got higher than -2ºC all day (so much for the forecast high of 1ºC) and that was with full sunshine throughout.

At 3.30pm I frantically started looking around for a heater. Maplin do quartz halogen heaters, but they had sold out and had 1,000 on back order, but all were spoken for. Machine Mart had sold out. So had B&Q – although they did have some basic quartz heaters, which are just as effective (so I bought one: only cost £20).

Just as well, really. By 3.50pm the temperature was -6ºC.


I wrote about this a year or so ago, but one of the best things I ever bought was a set a flyscreens from www.flyscreensuk.co.uk (tel. 01628 481919).

Hinged Flyscreen

I used to have major problems every year with my computer attracting all kinds of winged nasties – huge moths, daddy long legs, every gnat and midge in a 2 mile radius. It still does, of course, except that they cannot get through the flyscreens!

I’m not lying when I say that last summer I did not have a single bug get through – and that includes those thunder flies (thrips) you get every year (tiny little black things).

I received a mail-out today, and Window Screens UK (the name of the company in question) has opened a new showroom so you can see what the products actually look like. They’ve revamped their website, and introduced some new products (including ready-to-fit roller blind screens and spares/accessories for the whole range).

I honestly don’t know why I put up with the problem for so long, before wondering if it were possible to get flyscreens in the UK. They are, after all, very common elsewhere in the world – particularly America.

The screens I bought were self-assembly (very easy), and they fit over my window cavities using continuous magnetic strips. I really do recommend them to anyone sick of flies getting in the house.


A wooden self-assembly kneeling chairMy project to build an ergonomic kneeling chair has been one of the most popular items on the blog. This page is a summary to identify the various separate articles involved in the project.

Note that this kneeling chair is made out of metal, not wood. The finished article is absolutely bomb-proof.

The separate articles are listed below:

  1. Welding Isn’t Easy! (Introduction)
  2. Project #1
  3. Project #1 (Update)
  4. Project #2
  5. Project #3
  6. Project #3 (Update)
  7. Project #4

Follow each stage in sequence.

Someone asked me what size bolts I used. I didn’t include that information in my drawings – I think I assumed that the diameter of the holes was enough, but I should have explained more clearly. In fact, the bolt size doesn’t matter as long as you don’t make your holes so large that the structure is weakened, or use such small bolts that these themselves become the weak point. Mine were two sizes – the ones used to link the struts were about 5/16″ (or 8mm); the ones elsewhere were about 3/16″ (or 4.5mm). I bought them online.

Someone else asked if the drawings could be used to make the chair out of wood using 2x2s and 2x3s. The short answer is no – because the strain on the part where the struts join the feet would be so great that the assembly would split (and even wooden ones you buy suffer from this problem, which is why I went for metal if you remember the introductory article). I suppose you could modify my plans and develop a functional wooden chair, but that is beyond the scope of this series.

I should also clarify that the kneeling chair I built used three parts left over from the last one I bought: the seat and knee pad panels, and the raising mechanism.

The pad panels are just bean-shaped plywood with threaded mounting holes in them. I re-upholstered them using foam and fabric purchased online (detailed in the articles). However, if you were building one from scratch it would be a simple matter to make your own panels for the seat and knee pads using ¼” or ½” plywood. The raising mechanism  would be a little more of a challenge, but still fairly simple to construct. All it consists of is a threaded shaft inside a corresponding threaded socket. When the shaft is turned the overall length of the socket/thread assembly either increases or decreases. Since the ends of this assembly are fixed to the support struts of the chair, the seat rises or falls as the thread is turned.


The chair is now complete and in use! If anyone has any questions you can email me via the contact form (comments were abused so I turned them off).

Here are a couple of diagrams showing how I put the parts together – you need to refer to parts #1 (plus update), #2, and #3 (plus update) for this to make sense, of course.

First of all, this is the seating section (the seating plate attaches to the top).

The Seating Section for Kneeling Chair To put it together, I used a pair of small G-clamps to hold to spacers (SP2a and SP2b) in the positions I had determined for them on one of the struts (A1). I made a weld along one edge so I could get the clamps out of the way, then finished off the welding in a vice. Then, I used the G-clamps again to hold the other strut (A2) in place – I used a mallet to knock it into position to obtain the correct spacing (so my screw-adjust riser would fit). Note that at this stage I also made sure the curved bottom ends were level with each other so the foot (C1) would be horizontal. Then I made the welds as described above.

Placement of Seat Plate on Seating SectionI used a pair of powerful welding magnets to hold the foot (C1) in place while I welded it in place.

I made sure the 45º angle cuts were level with each other (just a little filing was needed to get the Seat Plate to sit level), then I used the welding magnets to hold it in place while I welded it.

Once the seat plate was welded in place (see diagram opposite for placement), I was able to slide in the Seat Support Struts (A1a and A2a) – again holding them in place using the magnets. They actually fit almost perfectly, but I did a little trimming to make sure I got the best fit possible. In each case I welded one side so I could get the magnetic clamps out of the way, then finished off the whole weld (all four sides) in a vice. Note that the dotted squares in the diagram show the approximate placing of the struts on the Seat Plate.

Next, the Knee Section. This is a little easier – note that I originally planned to use two spacers on this section, but I didn’t allow for having to slot the Seating Section through it, and a spacer higher up would have got in the way.

The Kneeling Section for DIY Kneeling Chair I assembled this in more or less the same way as the Seating Section. Initially, I clamped the spacer (SP1a) in place on one strut (B1) and did a single weld, then finished it off in the vice with the G-clamp out of the way. Then I positioned the other strut (B2), making sure the curved cut-out was level with the other one (for the foot) and that the spacing was correct along the whole length. Then I welded it. I welded on the foot as described for the seating section.

I used my angle grinder and a flap wheel to grind down all the welds and to remove spatter.

Next came the test assembly. Omitting the second spacer from the Kneeling Section had the additional benefit of allowing a little flexibility when it came to sliding the Seating Section between the kneeling struts. But I’d got it right and everything fit. I did have to do a little widening of the holes to get the bolts through – with hindsight I would have drilled after welding (unless you are millimetre perfect there is always going to be a slight mis-alignment).

I painted all the parts using Hammerite Metallic Black (from a tin). I inititially tried Hammerite Silver (from aerosol), but apart from the fact it doesn’t fill in imperfections very well, it also looks a bit cheap – too silver, if you ask me! It also makes a bloody mess.

This is the finished stool, fully painted and assembled. You can see how the riser mechanism fits between two sets of holes, and the other set is where the two sections are joined.

The Completed Kneeling ChairYou can also see the crappy cushions I am using at the moment – the final stage of this project is going to be to make a decent pair (I’ve found a great company called eFoam who can cut foam to measure).


I’m putting the parts together at the moment – just finished the seating half.

While I was assembling it I discovered an error in one of the dimensions on the diagram in Part 2 of this project.

You can find Part #4 (the final) of this project here.

The support strut longest length should be 90mm and not 110mm.

I’ve amended the original diagram and annotated the Part 2 write up. Apologies to anyone who has been following this (and there appear to be quite a few) – but at least it is an error in the right direction – the part will just need trimming slightly. I used a flap wheel on my angle grinder to work it down.

I don’t know how it happened. I made a mock-up out of paper when I did the original calculation, so I can only guess that I put the wrong dimension in the drawing as a typo – and that’s what I was following!

Incidentally, I’m getting better at welding as I do this and one thing I’ve learned – probably obvious to those with more experience – and that is GO SLOWLY . You get a nice weld without gaps or pockets of slag.

EDIT: If you came to this page from a search engine, don’t forget to look for Kneeling Chair Project parts #1, #2, #3, and #4 (plus a couple of updates) using the site search facility. This project is now complete and there are drawing/blueprints in the other parts.


Here’s an update to my on going project (Part 1 here and here, Part 2 here) to build a kneeling chair .

Also take a look at the Part #3 Update here.

The diagram below – you can call it a blueprint or whatever (I make no claims in that area) – shows the holes and necessary cut outs for the support struts I am going to fabricate from the steel I purchased recently.

Kneeling Chair Parts - Drilled Holes And Cuts Don’t forget that I am using some of the parts from my existing chair, and that explains some of the oddities (e.g. the 9mm holes, the hole spacings on the seat plate, and so on).

The plans above should make sense – the 9mm holes are in the sides of the A and B struts, and there are a set of 5mm holes in the top faces of the B struts for the knee-cushion to be fixed to. All the holes go through both faces of the struts.

At the bottom end of the A and B struts, in the side faces, there needs to be a cut out 30mm across (the width of the box section metal) and with a radius of curvature of ¾” (so it fits the 1½” diameter tube which forms the feet of the chair).

I’ve spent a few hours over each night of the last week sanding the parts to remove corrosion and oil coating, cutting out the curved notches, and drilling holes. I’m hoping to at least start the assembly over the weekend.

EDIT: If you came to this page from a search engine, don’t forget to look for Kneeling Chair Project parts (#1), #2, #3, and #4 (plus a couple of updates) using the site search facility. This project is now complete and there are drawing/blueprints in the other parts.


OK. This ongoing project for a DIY kneeling chair is well on its way now. Here’s the schematic of the parts I’m using and the relevant dimensions. You could call it ‘plans’ or ‘blueprint’, but I’m not making any claims in that area!

Also refer to the next article (Part #3) here.

EDIT: Please note the dimension in yellow… this corrects an error I discovered when I put the seating section together (it originally said 110mm).

Kneeling Chair - Updated Parts List I spent today (had most of the day off in order to get this going) trimming the parts. Last week I used an angle grinder to take the 3m lengths of 30mm box and 1½” round steel sections down to manageable pieces. The diagram below shows roughly how the parts will fit together – I’ll put up a better drawing with dimensions later.

Schematic Kneeling Chair (labelled)Basically, there are two seat struts (A) parallel to each other, and two knee struts (B) the same. The seat struts are closer together and fit inside the knee struts in a distorted X shape. I’ll use the spacers to make sure that the struts are the right distance apart.

You can see how those seat support struts (Aa) I mentioned in Part #1 will work. The original chair didn’t have these, so you can imagine how weak it would have been. In order to accommodate these struts I increased the size of the seat plate from the original, though the hole spacings will be the same. At a later stage I’m going to build my own upholstered seat and knee pads, but for the time being I’ll just transfer the ones off this existing chair (hence the hole spacings).

Anyway, I ended up using a good old hacksaw to cut the 45º angles. It was far less hassle then I’d imagined (from metalwork days back in school). I must confess I used the angle grinder and a coarse grinding wheel to trim the ends, though. I finished/squared these off with a metal file.

EDIT: If you came to this page from a search engine, don’t forget to look for Kneeling Chair Project parts (#1), #2, #3, and #4 (plus a couple of updates) using the site search facility. This project is now complete and there are drawings/blueprints in the other parts.