I know they're not much to look at, but at least it's a start. The drawing above is straight out of the AP racing catalogue and is their 10" disc with integral mounting bell. I had wondered about designing my own hub-cum-mounting bell but as I've said earlier, I don't want to price the car out of the market and the less machining that potential racers have to do the better. For those who like looking at catalogues it's part number CP2222-258/59
Now, I know this looks unbelievably unlike a Wilwood Powerlite calliper, but don't worry. What I've done is create a volume model which encompasses the maximum dimensions for the calliper. If this fits under the virtual wheel, then I'll know I haven't got a problem when it comes to the real thing. The last thing I want to do is waste oodles of time generating a micron perfect facsimile of the calliper only to find that tolerance build-ups in the real thing lead to an expensive aluminium-to-aluminium contact.
Anyway, with these two bits designed I can move on to getting the upright designed. I'll be trying to make the upright as light as possible, by designing pockets into it. So that I don't make the thing ludicrously weak, I'll be taking advantage of the built-in FEA to SolidWorks.
I'm back... I did take the laptop away with me to a very nice part of Wales, but it was so nice, I didn't actually take it out of the bag at any point during the week. Anyway, as I've still got a week before I have to go back to work, I've got some time to crack on with the design.
For my other reader, the upright is the business end of each wheel station. It carries the hub that the wheel bolts onto; the outboard pickup points for the suspension; the joint for the steering arm; the brake calliper and the brake disc as well. In short it has to resist all the road loads into the chassis without deforming.
There are three ways of manufacturing an upright: casting, machining and fabrication. Now, while I do have a fully working forge, I'd wager that very few hobbyist builders out there do. Casting is wonderful for many reasons but for small runs it's extremely expensive and you tend to have to do a lot of machining on the finished casting anyway. So I can probably safely discount it.
Machining is what I'm best at, but the cost of a lump of billet might scare a few people - a 2" x 2" x 3000mm (don't you just love industries where Imperial and Metric dimensions get mixed about) billet costs around 150 GBP and with a decent design most of that billet will be converted into swarf. Most 'professional' race cars tend to use machined billet uprights (the McLaren F1 did as well) and as it's someone else's money when we're living in virtuality, I'm not necessarily worried about wastage.
Fabrication is a very efficient way of manufacture, but it requires real craftsmanship to get an accurate finished item with no structural weaknesses. A good quality fabricated upright probably isn't going to come out of an amateur's garage with the aid of a Machine Mart MIG welder. I don't think I'd be happy racing around with something I've welded together, and welding pretty much guarantees the use of steel and it's resultant weight penalty.
So, machining it is and the next job is to get a few parts modelled up for further use: the brake disc and the calliper space model (i.e. I only need the outside dimensions rather than an exact 3d model with all the fillets, chamfers and the like). I'll be back after I've got busy with Solidworks.
Because I like nothing more than fiddling, I've put the majority of my calculations (I've left out the bit about effective pad radius for the moment) into a nice Excel spreadsheet and included some stuff about specifying the brake bias bar and the master cylinder diameters for front and rear. I've uploaded it here for your general delectation and amusement. It's in Excel format, although the original was done in OpenOffice...
I'm disappearing off on holiday for a week or so, so my three readers will have to amuse themselves elsewhere...
My other commenter (my god, I'm starting to sound like Terry Wogan) wondered why I was going with 14" wheels, when 13" wheels would be lighter and the brakes that I could fit underneath would be more than man enough for the task - and if someone wanted to fit 14" rims, there would be nothing stopping them. The short answer is that I had no strong feelings on the subject, other than the fact that I like having plenty of space around the upright for kinematics reasons. I did however promise to do some calculations and get back to him. OK, here goes...
Minimum weight for the car is 560kg and I'm currently working with a wheelbase of 2.2 metre. We're going to be mid-engined, so I wouldn't be too surprised is we have a weight distribution somewhat towards the rear, say around 45% Front : 55% Rear. Centre of gravity height is unknown. The only useful figures I've got (I've only ever done testing of military vehicles, which probably doesn't help much) are for a Toyota MR2 at 0.485m above ground. We'll be a smidgin lower and the absence of a roof on the car will take that lower still, so I'd estimate (in finest sticking a finger in the air fashion) a centre of gravity around the 0.42m mark.
The tyres for the formula (Yokohama A048R) can produce a static coefficient of friction of around 1.2-1.3, but we may well have plenty of downforce, so it's not entirely inconceivable that we could be producing around 1.5g under braking. So, a quick spurt of calculation gives the following weight distribution:
| Front | Rear |
| Nearside | 123.75 kg | 151.25 kg |
| Offside | 123.75 kg | 151.25 kg |
Let's now look at the weight distribution under braking. When you brake, weight is taken off the rear wheels and put on the front wheels. The amount of weight transferred is a function of mass, rate of deceleration, wheelbase and centre of gravity height. The governing equation is:
Weight Transfer = Mass x Deceleration x Centre of Gravity Height / Wheelbase
So with 1.5g deceleration, we get just under 1.6 kN of weight transferred (or 160.3 kg of mass). That's a fair chunk of mass - we end up with just 71.1 kg of mass on each rear wheel when braking, which wouldn't give me huge confidence under braking unless there was a nice, healthy chunk of downforce to screw the rear wheels down. We also have 203.9 kg on each front wheel.
At 1.5g of braking, and assuming we've wound the bias adjusters to the perfect position, each front wheel has to provide 203.9x9.81x1.5 = 3 kN of deceleration force. George Polley's website suggests that the overall diameter of a 13" A048R tyre is 550 mm, which gives us a torque produced by the braking system of 3x0.55/2 = 0.825 kNm.
I've been looking at two different brake callipers - both can use a 276mm diameter disc (that's 10.5" in old money give or take a gnat's chuff). The bigger, 4-piston, calliper uses a 46.1mm high brake pad and 4 1.25" diameter pistons and the smaller, 2-piston, calliper uses a 38.4mm high brake pad and two 1 5/8" diameter pistons. The coefficient of a brake pad varies a bit, but Ferodo DS2500 compound (I know a lot of racers use Mintex, but Mintex don't publish their mu values and Ferodo do) has a mu value of 0.5, so effectively the deceleration force at the rotor needs to be doubled to give a force at the piston.
I'm going to assume an even distribution of force across the whole of the brake pad so that the centroid of that force is in its centre. So the effective radius for the application of the braking force is going to be (disc diameter - pad height) / 2, or 110.45mm for the 4-piston callipers and 114.3mm for the 2-piston callipers. Torque = Force x Distance, so the piston force = torque / distance (x 2 to allow for the pad friction coefficient). Running with the values earlier, we get the following numbers: 7.2 kN for the 2-piston callipers and 7.5 kN for the 4 piston callipers.
Pressure = Force / Area, so we can now calculate the pressure required in the braking lines at the front. It comes out at 24 Bar for the 4 piston design and 27 Bar for the 2 piston design. The callipers are rated at 30 Bar, so they're man enough for the job and all we need to do now is sort out whether our poor race will actually be able to apply enough pressure at the brakes to get that level of deceleration. The ECE braking regulations mandate a brake pedal force of around 500N for stopping with the engine disengaged. So if we assume this is our pedal force and a pedal ratio (amplification by the lever action) of around 5, we have a pedal force of 2.5 kN. This means we need an area ratio of around 3, i.e. the area of the calliper pistons needs to be no more than three times the area of the master cylinder piston. For our 4 piston calliper we get a piston diameter of 36mm and for our 2 piston callipers we get a maximum diameter of 58 mm. These comfortably fit within the bounds of what is available and give plenty of options for fine tuning by having a smaller pedal force ratio.
So, in summary, the 2 piston callipers and 13" wheels will be fine, and in a desire to make as many people happy as possible, I'll engineer the uprights and suspension to fit under 13" rims. I've got a nice steel rim handy - I'll measure that if this rain ever stops falling.
actually it's probably my second or third. This one stems from a close study of both Milliken and Milliken and Katz while in my favourite room of requirement. M&M reports a lot of results from the F1 ground effect era which indicates that the best downforce was actually developed with a ground clearance of 75mm (which just happens to be the minimum ground clearance for RGB) and there are some useful wind tunnel results from vehicles with underbody tunnels and no sealing sideskirts. So with careful consideration paid to the shape of the underside of the chassis, it looks like there might be the possibility of generating useful downforce for the car. Hmm.... I had been slightly upbraided by my solitary commenter (thanks Steve) for having a pushrod suspension system in the first picture produced out of SusProg. If I do manage to get significant downforce out of the car then having a pushrod system will make it easier to engineer in a third spring to deal with the extra aero-loading. I quite liked the idea of a pushrod suspension in any case as it makes it far easier to adjust the suspension in terms of ride height and damper adjustment as you can get at the adjusters simply by taking the bodywork off rather than having to get down on your hands and knees and contort your wrist around the suspension arms, driveshafts and brakes. I have to do that now with my daily driver and it's not a whole heap of fun.
I've also been thinking about the uprights as well, or more specifically the hubs that are going to bolt into them. I'm not a big fan of reinventing the wheel, and HiSpec Motorsports do very nice CNC machined (and you can't beat CNC bling) hubs based on patterns of classic Ford boxes of the 1970s and it would be churlish not to use something easily accessible just to be different. I know of at least one racer using these, so I might sidle up to him at some point in the future and ask to come round with my vernier callipers and see if I can come and measure them for dimensions. Once I have those dimensions, I can work on sorting out the other positions on the upright. The other thing I need to work out is how to avoid the dreaded REIB problem. I could make the suspension completely non-adjustable, but I reckon there are two main problems - firstly, I can't imagine anyone constructing the car is going to be so accurate that the designed geometry is actually going to be the real-life geometry and a bit of fiddling is bound to be necessary; and secondly, giving someone a non-adjustable racecar is bound to be a recipe for disaster. A lot of the RGB racers seems to be inveterate fiddlers.
Of course, I could just ignore the fact that I'm using rod ends in bending and make them nice and stout instead. As I'm not planning on winning a Formula SAE design competition and everyone else seems to manage fine with that sort of structure. I could get away with it, but every engineering bone in my system is yelling at me not to accept such compromises and spend 6 months developing a beautiful adjustment system. Knowing my luck such a system would weigh more than the rest of the car put together, although I do like the eccentric bolt system that's on my Mazda and it would limit the amount of adjustment options to what is sane.
Anyway, time to get back to the AP Racing catalogue and find a suitable set of callipers and discs for the virtual racer. Once I have both, and the dimensions of the hub, I can sort out a wheel offset and then, finally, the position of the suspension joints. Why do I need all this information? I want centre point steering on the car. This means that the line passing through the wishbone mounting points on the upright passes through the centre of the contact patch and there is no kickback through the steering when longitudinal forces are applied to the suspension. Kickback drops driver confidence and as I've stated before, an under-confident driver is a slow driver.
In the last post, I'd sort of produced a ballpark figure for the space inside the wheel rim of around 310mm. I know that the rim slopes inward at the front and I'd probably have more to play with than that provided the brake disk and calliper wasn't too deeply embedded. So, a quick search through the AP catalogue turned up the fact that 254mm discs aren't supported by 4-piston callipers, but 267mm discs are. Of course when you look at the outside radius of the callipers they need 312mm of space inside the rim. Close but scarily close to being a show stopper. There's plenty of options in the 2-piston calliper range and frankly this car is going to weigh very little. But I just have this horrible sneaking suspicion that if we do get sufficient downforce then 2-pot callipers may not be man enough for the task. I'm thinking here of braking down at the end of the Revett straight at Snetterton - it's not somewhere I'd like to run out of brakes. I'll wait until I can measure a 14" alloy (actually, come to think of it, there's five sitting in the garage ready for the kit car it looks like I'll never finish building because I'm better on a CAD system than I am with my hands.) before making a firm decision. Having seen the trouble others have had getting brakes and uprights to talk nicely to each other, I don't want to get this fundamental wrong.
I've been doing a little playing around with SusProg in order to look at the fundamental effects of locating the instant centre along the vehicle centreline. I've revised my estimate of track after looking at the track values of someone else's car - I'm now looking at a track width of around 650mm. Anyway, I've modelled two suspensions - one with a fairly conventional wishbone setup and one with sharply inclined wishbones so that the instant centre is along the centreline.
Look at the two photos:
The upper one is the conventional. The pictures aren't to scale (blame finger trouble on my part), although the grids are identical at 40mm spacing. The big black dot is the ground on the centreline and we're looking at 40mm of bump travel here. The obvious difference is that there is a lot of camber change in the 'centreline' suspension - this is to be expected, as using such suspension gives a very fixed virtual swing arm length (approximately half the track width), while the normal suspension has a significantly longer swing arm and less camber change in bump. The question is whether the absence of camber change in roll makes up for the change in bump. The short answer is probably, but only at the rear. At the front the camber change that would result in the wheel acting like a gyroscope and kicking back through the steering. That would be something that could decrease driver confidence and is therefore a bad thing as far as my design principles go.
I'll keep tweaking the values for a while and see if I can get to a better centre point solution. I'm pretty limited in where I can put the bottom wishbone joint as it can't be lower than the 75mm limit mandated in the rules. As I'm planning to design my own uprights, I've got a fair bit of flexibility in where I put the roll centre so I can lower it from where it currently is to prevent jacking of the vehicle under cornering.
I'm getting to the stage where I should really stop fiddling with SusProg and work out what shape the uprights are. Key to this is going to be being able to fit a suitable set of brakes within the wheel envelope. This might sound easy, but I know at least one racer who had all sorts of problems trying to get a set of brakes to fit. So first job is to find a suitable wheel and get some measurements off it. I'm limited to 6" wide wheels and luckily, I've got a dented 16" alloy wheel sitting in the shed (before any of you comment, I know that the A048R spec tyres don't come in 16" sizes, but I wanted a quick and dirty check on what I had here before I pester one of you for a measuring sessions). A quick bit of steel tapery and I get a 360mm envelope within which to work. If I assume that there's no change in wheel web thickness, each 1" reduction in rim size means 25mm less envelop to play with and I doubt there's many 6"x15" wheels out there, so I should think that a 14" wheel rim is likely to be the norm. Certainly the above-mentioned racer is running 14" wheels. So, I think the maximum envelop I have to work with is going to be 310mm. Now all I need is some brake callipers to fit underneath.
One quick glance at the Wilwood catalogue and their Powerlite callipers will do the trick. The trouble is that in order to pass scrutineering the car needs a working handbrake and the 'add-on' callipers I've seen probably won't fit comfortably inside the wheel. So, the obvious choice is HiSpec Motorsport, who do specific callipers with a mechanical handbrake that doesn't impinge on the outside of the calliper. Their version of the Powerlite looks very similar, although their mounting diagrams leave a little to be desired. I'll assume a 254mm disc for now.
At its basest level, the role of the suspension is to hang the wheel off the chassis and stop it flailing around. Any object can have six ways of moving - three displacements (up and down, inwards and outwards and forwards and backwards) and three rotations. The suspension is meant to restrict five of those movements relative to the chassis so that, in theory, the only movement is up and down. If you have ball joints at each end of the suspension links, you need five separate links to control five out of the six possible ways of moving - hence the term multi-link suspension.
I've already decided to use double wishbone suspension for the car and each of those arms is equivalent to 2 separate links. This means we need an extra link - the toe link, joining the upright to the chassis, otherwise the upright will be free to rotate about an axis running between the top and bottom ball joints on the upright. On the rear this link can be fixed, but on the front it is joined to the ends of the steering rack so that the racer can actually negotiate corners. I'm actually considering having identical suspension front and rear so that it cuts down on the component rate, i.e. four identical uprights with either a fixed toe link or a steering arm rather than having four separate uprights per car. As anyone who has worked in a manufacturing environment will tell you it's far easier and cheaper to build four the same than four different.
Anyway, I digress... Analysis of five separate links is not a trivial matter but a bit of careful inspection of a suspension will show that for a given position of wheel and chassis, you can replace the entire suspension with a single arm and its kinematic and force behaviour will be the same. The point where this single arm pivots is called the instant centre of the suspension. The further away from the wheel this instant centre is, the less change there is in camber as the wheel moves in bump and rebound. The classic case is a solid axle suspension where the instant centre is effectively positioned off at infinity so that there is no camber change as the suspension rolls. A similar case is where the wishbones are parallel. Movement in bump causes no change in camber, but roll causes significant camber change.
Once you know the location of the instant centre, you can calculate the position of the roll centre. This is defined as a point where a lateral force can be applied to the car which would cause no roll of the body. Effectively it's a line of action where the side force from the tyres is transmitted into the body. If the line of action happens to pass through the centre of gravity, there is no roll and if the line of action is above the centre of gravity then the car will lean into the curve. Most of the time, the roll centre is below the centre of gravity and the car leans outwards when you steer. The roll centre is found by joining a line from the centre of the contact patch to the instant centre. Where these two lines (one for each side of the car) intersect is the kinematic roll centre.
Roll centres are important as they control how much weight is transferred to which wheel when you corner. The side force generated by a tyre is a function of three things: the weight supported by the tyre, the camber angle of the tyre and the slip angle - the angle between the direction of travel of the tyre and its heading. Controlling how much weight is on each tyre is a way of controlling its handling and it's something we'll come back to later when we get to sorting out the spring and damper rates.
We can't control the total amount of weight transferred - that's a function of how much 'g' we're pulling in a corner, the height of the centre of gravity and the track of the car. F1 engineers have been trying to put the c of g below ground level for many years with little success, and I'm sure I'm going to have similar success on that front. Having a roll centre close to the c of g is achievable and will limit the amount of roll of the car, making it more predictable. The only problem we have to consider is jacking. Anyone of a certain age might remember the joy of driving a VW Beetle close to the limit. The Beetle has swing arm suspension at the rear - instead of wishbones it used the half shaft to support the wheel. When you cornered the force was transmitted up the half shaft and with a lot of roll this would jack the rear of the car upwards and you could get the rear wheel to tuck under the car and lead to a Beetle-shaped hole in the nearest hedge.
Anyway, enough waffle, back to design. In the last post I stated that I wanted no camber change in roll and minimal migration of the roll centre. The only way to achieve this is by having the instant centres of both sides of the suspension meeting each other on the centreline of the car. This will result in shorter equivalent swing arms (i.e. the length of the imaginary bar joining the centre of the upright to the instant centre) than could otherwise be achieved. In other words, using this method there will be more camber change in bump using this system than there perhaps could be. The only way to get a reduction in camber change is to have as wide a track as possible. Until I can get out and measure someone's bodywork (no part of the tyre is allowed outside the envelop of the bodywork under the rules, which sort of rules out a Formula Ford as a design concept), I don't know how large a track I can get away with. So for now, while I work with the concept, I'll make a few assumptions and assume the maximum width will be around 1400 mm.
BTW the picture above (click it to enlarge) is of a quick and dirty concept, which has a reasonably long equivalent swing arm length (where the three thin red and green lines converge is the instant centre), but around 40mm of lateral roll centre migration (the diagram is for when the car has rolled through two degrees). It's an OK concept, except the top wishbones are too close together to match with a sane set of rollbar backstays - in an attempt to keep a handle on weight, I'm trying to use as little spaceframe as possible, so integrating the suspension pickups with the roll bar seems a fairly good idea. I'll be back once I've done some tweaking to get the instant centres aligned.
and I'm not afraid to use it. Reading through the regulations of the RGB championship, there's no ability to tune the engine from when it got separated from the motorcycle. So if you're going to build a successful racer, aside from a large amount of driving talent, you need to find other ways of gaining a competitive advantage over your fellow competitors. 'Proper' aerodynamics aren't allowed (and although there doesn't appear to be a limit on underbody aerodynamics, the minimum ride height of 75mm seems to not be of much help in generating some venturi-assisted downforce), there are minimum weights (although getting close to them seems to be a challenge for those who do indeed take the RGB regulations at their word rather than constructing a specialist lightweight chassis) and everyone is running the same tyres.
So it appears the only way to beat your fellow racers is to out-drive them, or for those with less talent, out-handle them. Here is where SusProg comes in. If you're incredibly rich, you can spend the GDP of a small African protectorate on kinematic simulation software like MSC Adams to help with your suspension design so that you don't have to rely on Colin Chapman's ethos of 'the suspension works great if you don't let it' to avoid all sorts of nasty kinematic and alignment problems.
As a former ride and handling engineer (OK, so most of the vehicles I helped engineer were green, extremely heavy and capable of dealing death over large distances), I'm afraid I treat the rest of a car as a black box - if it doesn't work, you get rid and find something else that does. I'm going to design the car from the wheels inward - create a suspension design that works, then stick a chassis on it. Using SusProg is key to this. It lets you design the suspension virtually and see how it works before you commit yourself to cutting your first bit of tubing.
I've already made a conscious decision to avoid using someone else's uprights to hang the wheels off. For a start, I haven't got the time or inclination to find some suitable uprights, sort out suitable brake discs, callipers and wheels so that they all work together and, more importantly, fit and then design a suspension that fits in with the limitations of the upright. I plan to design easily (at least easily if you've got access to a nice CNC milling machine) build-able (possibly even fabricate-able) uprights and then hang everything else from there.
Enough with the planning, lets get on with the design. I'll start at the back, not least because I only have to deal with the wheel moving up and down and not with having to steer as well. Using a double wishbone design is the obvious choice (everyone else designing racing cars seems to do the same thing) but then it all gets a bit more complex. We need to control what happens to the wheel when it rises up and down relative to the body. The two things we need to control are camber (the inclination of the wheel relative to the vertical) and toe (the rotation of the wheel about the vertical).
Let's start with toe. If your wheel steers itself as it goes over bumps this may not be a good thing. If there is enough self-steer the car will potentially be less stable. A less stable car leads to a less confident driver and a less confident driver is a slower driver. Sometimes this steering over bumps can be a good thing - Lotus use it on the Elise to improve stability with the steering that results counteracting the grip changes due to the change in loading on the contact patch. If you can find a copy of IMechE paper C466/014/93 (it's in the proceedings of the Vehicle Ride and Handling conference - take a look at C466/010/93 as well if you get the time as it's a report on what I was doing at the same time) it's all 'explained'. Personally, I think eliminating toe change altogether is an easier objective and hopefully a racer will prefer an absence of any taint to the feedback he gets from the car.
Camber is a bit more subtle. If you tilt a wheel over, instead of a nice oval contact patch between the tyre and the road, you get one shaped a bit like a banana. As the rubber rolls through the contact patch it is forced in a curved path rather than a straight one and this deviation provides a small sideways force. This is handy if the force acts in the direction you want to turn and less handy if it doesn't. As the suspension moves, it moves through some form of arc and this changes the inclination of the wheel and can lead to reductions or increases in the grip of the tyre. The arc is subtly different between the wheel moving in bump (where the chassis stays flat to the ground) and in roll (when the chassis tilts moving the suspension mounting positions relative to the ground)
Another thing to consider is traction. Potentially we are going to feed 180 bhp to the rear wheels and we want as large a contact patch as possible to avoid the wheels spinning and wasting acceleration potential. A cambered tyre has a smaller contact patch than one running upright on the road. The first racer on the gas in a corner carries the most speed out and has the lower lap time, so being able to put the power down with the car rolled over is a key issue to resolve.
So taking all this stream of consciousness out, I've come up with the following design parameters:
- Minimal camber change in roll (I'm hoping for zero change if possible, like the Porsche Carrera GT)
- A non-migrating roll centre (I'll talk about roll centres in a later post, but they're very important to vehicle handling)
- Low camber change in bump, and a negative camber change if possible
- Zero change in toe with bump
OK, so we've got some parameters to work with, let's start messing with SusProg...
I'm bored and frustrated. I teach engineering in the British 'Further Education' sector, i.e. I'm allegedly not smart enough to teach undergraduates and anybody with a modicum of intelligence gets grabbed by the local schools to be taken on the path to university, leaving us with a curious mix of students who don't quite understand the point of education. Teaching does have it's side bonuses. I have a fully equipped workshop with some very expensive CNC machines in it and a CAD suite with Solidworks. Inspired by the wonderful DP1, I'm going to do something similar, only in a British style.I have a few friends who race in the RGB series, run by the 750 Motor Club. The class seems to be a mix of classic (i.e. bolted together out of bits of 1970's vintage tat) kit cars, all using Japanese motorcycle engines. The cars have to be able to pass an MoT, although there is no requirement to actually have one. This does give a designer a great degree of freedom to work within the regulations, so I have a very basic plan:
- mid-engined racer with rear-wheel drive
- spaceframe chassis
- front or side mounted radiator(s)
- someone else's bodywork - the one thing I don't have the facilities to make is bodywork, so I'm thinking of begging/borrowing someone else's to drape over the chassis
- my design of suspension - before being dragged kicking and screaming into the halls of 'academia', I worked as a ride and handling engineer, so I should be able to make a decent fist of it...
- decently engineered front and side impact protection that hangs off the chassis, so that
when if the driver makes a small error he shouldn't have to replace the chassis or get busy with a MiG welder in the paddock
From these humble idea, over the next few months, I plan to have a fully existing CAD model of a racer that I plan to leave on the Internet for posterity so that any stupid enlightened racer can put it together in a garage and have fun with. I'm not planning to do any manufacture myself, it's more therapy to stop me taking the students around the back of the workshop and committing physical violence with a 25.4mm diameter bar of tool steel.
