Valves...

Although I've still got 4-way adjustment (high and low speed bump and rebound), there's still going to be times when there isn't enough adjustment available within the bleed and blow-off valves to match into the car. So, instead of the solid piston and through rod design of the original, the picture above is of a standard shim valve and orifice piston. This will be the ultimate determining factor for high speed damping - which gives the option of using the high speed adjusters to control the 'knee point' of the damping curve.

Virtually every damper uses shim valves somewhere along the line as, although they're horrendously non-linear (although a quick study of the various text books will give the suitable formulae - sadly the IMechE site is down at the minute, so I can't tell you if it's in Roarkes or not) they're a nice consistent non-linear, which needle valves tend not to be. The disadvantage is that, other than by supplying a pre-load (and a lot of cheaper dampers provide adjustment this way), you can't change the characteristics except by cracking the damper open and changing the shim diameters, stacking arrangements and thicknesses. For a top end damper, you often get a choice of 30 different shims to build into your stack, which gives an eye-watering number of options and excessively long times spent playing with the damper dyno trying to get the characteristics you want.

The basic design is still going to be twin tube, with all the flow passing through the valve block. The problem with this is that as the damper moves in and out the volume of the working chamber decreases and increases. Now hydraulic fluid is not renowned for it's compressibility, so we need a reservoir to hold this extra fluid. In 'proper' twin tube dampers, the annular ring around the working chamber does the task, but I want these dampers to work irrespective of orientation - the classic way of telling that a twin tube is a twin tube is to invert it, pump air into the working chamber and feel the lack of damping that occurs. So we'll need a second floating piston somewhere, with a gas pressure chamber on the other side.

Gas pressure can be a useful thing, in that you can use it to support some of the weight of the car and you get a slightly (more if you don't have a big enough chamber for the gas) rising rate as well. WNTL? It's another non-linearity which may need tuning, and I don't have huge amounts of free time...

Back to the drawing board...

OK, so I got a price back from my tame manufacturing partner for the design of the six way adjustable damper which made my eyes water a little and, notwithstanding the fact that it was for an engineering one-off, even with economies of scale wouldn't really be viable in the sense of being able to sell it to any target group other than rich idiots.

So we're off on a voyage of discovery into how to make something cheaper. The first thing to go is the plethora of adjusters. I'd envisaged lots of precision drilled barrels which would give consistence between units. Of course if you take a cylindrical component that can be turned out a huge rate and then have to carefully mount them in a dividing head and drill 16 holes (8 for the indexing mechanism and 8 different sized ones for the orifices) in exact positions, then it's going to cost a lot more to build one. If you're building thousands then you sort out jigs and fixtures, but I can never foresee this being a mass production item, not matter how bling it is...

Now, I still want separate adjustability of high and low speed damping at a sane price, so that I can take a unit off the shelf and valve it for most applications. If we can't have miniature drilled orifices to squeeze hydraulic fluid through, then we'll need a needle valve that you can screw in and out to change the size of the orifice. Not as repeatable and you'll need a damper dynamometer (a few thousand pounds) to do setup.

High speed adjustment will be similar to the original design... OK, so a short CAD session later we have mark II of the adjustment valving:

I've shrunk the component count down from eight individual bits down to three (not including the coil spring and various sealing O-rings) and there's no nasty indexing and drilling required. With the exception of an exhaust hole in the blue component and the hex adjuster on the top, it's all lathe manufacture and thus reasonably rapid (and hopefully cheap)

Away from the tiny precision bits, I'm rationalising the design of the main body. Instead of having a massive boring job, I'll use standard off the shelf tubes interfacing with turned caps. Minimal cost, and bar a few threads, no machining. It'll all be fine...