Projects '31 A FHC build (design?) thread

In the above the left front is going down when the right front goes up - in real life this dosn't happen. When the left front goes down the right rear reacts not the right front. the left front drops and the right rear will rise. And that is where i see problems with the pressure in the system.

 

The frame, the axle, and the two triangular control arms represent the sides of a trapezoid. That is, the control arms aren't parallel - in fact their effective angle from vertical is greater than it seems because the upper pivot is a steering ball-joint, the pivot point of which is in the large cylindrical thing outboard of the tab on the axle. So, the control arms are non-parallel swing-arms, which means that their extrapolated intersection defines an instant centre about which they allow the axle to rotate in roll. As it happens that instant centre is normally about 65mm above the road, and it doesn't migrate very far over the 6°-odd of roll that is required.

The movements in the diagram are relative to the car's frame. What happens in real life is that three wheels remain on a roughly horizontal plane while the fourth is displaced above that plane due to a bump in the road. The frame will tilt slightly about a diagonal axis.

Let's say it's the left front that's on the bump. In a conventional system (and discounting the effect of frame flex) the left front and right rear springs compress, and the right front and left rear springs extend. That does in fact give the diagonal reaction you're talking about, and it also induces torque in the frame. The point of the interlink system is to allow diagonal reactions to self-compensate through corresponding opposite displacements in the other two wheels, and thereby eliminate torque in the frame.

The result is total, free, unresisted articulation in warp. Park the car with one wheel on a bump, and none of the springs will be compressed. The frame will merely assume a slightly-tilted attitude to compensate. (And, though this will be a low car, it will be able to accommodate a single-wheel bump of around 11" - much more than the ground clearance! - through that free diagonal tilt action.)

It takes a while to get one's head around the warp-articulation principle: at first it seems disastrously unstable. Once one sees it it makes perfect sense, but it is a completely different mind-set. Take another look at the first diagram: that's the principle in its simplest form. There are many possible equivalences, though, of which one is the hydraulic system I have in mind.

 

Ah, I get it. Thanks.

 

Still digging this thread. Understandint a tad more, too. I wonder how many HAMBers know what FHC means? Gary

 

A bit like a DHC, innit.

This really is fascinating, not I´m starting to get a handle on how it functions. Never seen anything remotely like it on a modern car. Or indeed any car!

 

Sort of relevant: I recently posted this on my blog:
http://artisanalcars.blog.com/2012/03/19/warp-articulated-suspension/

 

at some point you've got to start cutting some metal!

 

I know! but at this stage the problem is buying some metal ...

 

I haven't been finding a lot of time for this project. It is always at the back of my mind, though, so further developments are merely a matter of time.

However, there is a lot in this project that stretches the idea of traditionality employed on the HAMB. Though I do not intend to use any principle that was not present on the engineer's palette during the "traditional" era - except that of the low-profile radial tyre - my aim is nevertheless something very far from the dominant hot-rod praxis of the time.

Therefore, lest this stretching exceed the newly-tightened focus of the HAMB, I have established a continuation of this thread on Dogfight:

Continued: '31 A FHC build (design?) thread