Beam Axles - Front, Rear or both.

Aha! I've just had another idea, and feel really stupid for not thinking of it in the first places, my normal work is obviously draining my brain.

Essentially, similar to the from beam ends on your original sketch, the beam forks with the top fork extending upwards. An additional arm would branch off forwards or backwards, and then a very light simple upright would mount to these three point via some Shim mounted BJ's. Still fairly bulky but...less aero disturbance and less complicated (calling it more elegant would be a push, no?)

EDIT- Three roughly evenly space branches (2 mottom one top) might end up more optimal, depending on loads and packaging issues for caliper mounts, provided you are mounting brakes outboard that is.

Dunk,

The De Dion is my preferred option (the sketch shows a spool because of earlier discussions on "Suspension for Spool" thread). With a De Dion I would definitely have some means of camber and toe adjustment, both to correct for manufacturing tolerances, but more importantly to tune handling.

This is a good opportunity for some original detail design (at Geoff's "Reasoning..." Level 1), mainly because there aren't many examples to copy. I can think of several ways to do it that would add less than 1kg to the total weight, and I might post some sketches later.

Meanwhile, how about asking all your team members (even the newbies) to solve this "Engineering Design 1.01" problem:

Design a joint in the middle of a length of horizontal (70mm diameter? x wall thickness?) tube, so that an accurately adjustable "bend", in both planes (ie. camber and toe), can be put in the tube, and the joint has the same strength and stiffness as the original tube (in bending, torsion, etc.). Low weight, ease of manufacture, and ease of "bend" adjustment being priorites. Camber adjustment +/- 5 degrees in 0.5 degree steps, toe +/- 1 degree in 0.1 degree steps, or better.

Who knows? Maybe a newbie will come up with a cracker!

Your last edit seems close to my preferred idea, but details are important. Otherwise, think about a wheel bearing housing that can be adjusted for camber/toe inside a larger, concentric, clamping sleeve???

Oh yes, KISS! http://fsae.com/groupee_common/emoticons/icon_smile.gif

Z

Any team members still around are busy finishing off the car at the moment. I'm actually on an work placement, although I'll be taking a long weekend in a weeks time to go help them finish build before FSUK. I'll be managing next year so I'm planning ahead, getting some ideas together for when I go back in August.

Sketches of ideas are good, sketches are always good. I can't sketch very well however although my technical drawing is excellent, seems a little contradictory I know.

However I can CAD reasonably well. I've had a crack about your problem but I think I got carried away, I have a soft spot for U-joints for some reason (worked on driveshaft and CV joint stuff last year, no actual u-joints though).

http://img827.imageshack.us/img827/2...ntbendforz.jpg

There's not real scale or dimensioning as such, just the concept. Additional turnbuckle could make it stronger but would also fight each other if not adjusted properly.

EDIT--my grammar is terrible.

I'm back with another challenge for your "aero-above-all" concept, Z.

You say suspension should be soft, and it must have 1inch of travel. But with this, even over small bumps, or light breaking and acceleration, you're going to have chassis ride height changes. This means changes in height of the BJs, effectively the beams and therefore wings are going to rotate about the wheels axes, meaning the aero effect is going to fluctuate. Not as much, perhaps, as a fully sprung wings, but enough so that to avoid the risk of stalling you'll have to reduce your peak available downforce somewhat.

This of course is not a problem if you go for the more complicated single "undertray" concept, but for the twin beam-wing it does reduce it's ...potency.

Quote:

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Originally posted by Dunk Mckay:
I'm back with another challenge for your "aero-above-all" concept, Z.

You say suspension should be soft, and it must have 1inch of travel. But with this, even over small bumps, or light breaking and acceleration, you're going to have chassis ride height changes. This means changes in height of the BJs, effectively the beams and therefore wings are going to rotate about the wheels axes, meaning the aero effect is going to fluctuate. Not as much, perhaps, as a fully sprung wings, but enough so that to avoid the risk of stalling you'll have to reduce your peak available downforce somewhat.

This of course is not a problem if you go for the more complicated single "undertray" concept, but for the twin beam-wing it does reduce it's ...potency.

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From what I can tell from his drawings, the beam-wing concept has no ability to pitch (except for flex in the beams).

I would be more concerned with the performance of the rear "wing" since the front wing will act as an obstacle directly in front of it, diverting air up and over the rear.

-Zach

Sure it does, if the whole chassis can go up and down and the front and rear beams aren't interconnected (except via the chassis) then the front can go down and the rear up, and vice versa.

If I got it right, Dunk means that moving the front axle up would decrease the angle of attack of the underwing... I might be wrong here, but I think the chassis pitching would not affect the angle of attack of any of the underwings significally; there would be so little movement on the BJ's (especially with some amount of "anti's" built in) that I could live with.

Yeah, essentially. As I see it the height of your wings is going to depend on a small number of things:

-You want them as low as possible without stalling so as to induce the maximum amount of venturi effect.
-You can't have then initially fixed at that height because of compliance in tire changing the ride height, and the change in the angle of attack with suspension travel.
-The also have to fit around your beams comfortably enough to have some amount of adjustment once built, because nothing is ever made totally accurate (especially when you have a tight schedule) and CFD is far from perfect.

With a single underbody surface you really only have to worry about tire compliance and maybe a small amount of packaging around the beams, notably at the rear actually.

I'm not saying that you can't still get plenty of DF with dual wings. But that there is even more benefit to a full body "undertray" in comparison, and I'm not so sure about how much extra work it would be over twin wings either.
While the mechanics of a full body undertray (mounting, packaging, stiffening, etc) might be a little more complicated to design, I think the aerodynamic work involved in getting the two interacting wings to work well together could end up being equal to simply working out a good F/R aero balance (and method of adjustment) with a full body design.

In the "WINGS" thread I suggested a small rear wing to adjust rear DF based on the belief that underbody DF tends to have CP relatively far forwards, but it was a long time ago t hat i read this and I need to freshen up before pushing that idea any further. Of course the additional wing will induce more drag, but can also be used to improve underbody performance so perhaps not a terrible loss. This all really needs much more investigation, investigation I intend to do as soon as I get back to uni in August.

On the full body mounting subject, do you think a simple beam (on eon each side) with a BJ at rear and sliding BJ or even just a P&S at the rear could work?

I agree with Dunk in almost everything; in fact I find a full undertray much much easier in terms of designing, building and integrating, plus it has potential for much more aero downforce. To get the CP rearwards, just use a rear wing to also "pump" the undertray exit...

Dunk, this is from Z on the second page:

Quote:

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Originally posted by Z:

The bottom line is that suspension Bounce (=heave) and Pitch modes only need very short travel. This is easily done with beams by having short travel (+/- 5mm) bump rubbers fitted at the mid-beam position. With these the chassis can be run very low with no scraping, so low CG, but there can still be plenty of wheel travel in Roll and Twist modes to keep the scrutineers happy. The soft Roll mode is, of course, no problem because no camber change, and the undertray doesn't scrape because it is beam mounted.

Z

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-Zach