Beam Axles - Front, Rear or both.

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Originally posted by coleasterling:
... but there comes a point when you have to actually make it and PROVE superiority.

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coleasterling,

And for the Nth**n time, it is the most thoroughly proven concept in the ground vehicle industry!!!

Read the Appendix in the above paper, and then YOU PROVE to me how modern racecars (the odd ones out) are superior. http://fsae.com/groupee_common/emoticons/icon_smile.gif
~~~o0o~~~

"... you're just that crazy old guy who yells about how dumb kids these days are..."

The crazy thing is that I feel like the teenager living in the Old Folks Home.

OFs "Have some tea and digestive biscuits Z."

Z "Aw, but I want to go out and play. You know, do something interesting..."

OFs "No, no, Z, don't put any sugar in your tea! You'll get too excited. Now you don't want to miss Bingo this afternoon. You know how much we all enjoy that..."
~~~~~~o0o~~~~~~

whiltebeitel,

Yes.

"flowery personality and charm"?

The OFs like it.

Z

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Originally posted by Z:
ENGINE. The engine in the Twin-Beam sketch was supposed to be a Royal Enfield, based on info I found on various websites. It won't work as shown. I got parts of the old and new models mixed up...

But, funnily enough, the day after I posted the sketch I was tyre-kicking in a quad bike shop and guess what's sitting in the corner? Three old British bikes - a Norton twin, Matchless 500 single, and a Royal Enfield 500! (Old Z had a Matchless 500 engine that went in every "fun" vehicle he dreamt up. I clearly remember it NOT being a great success in the canoe (I was about 10). The first time the throttle was cracked open the propellor spun maybe five times one way, and the canoe did a half turn the other!)

So I had a good look at the RE, and I like it! If lots of REs were available, at the right price, then I would certainly consider one. The long term goal would be a turbo or supercharger (with standard CR~7:1), crank driven clutch and dog-neutral, then direct chain final drive ~5:1 (ie. ditch the gearbox).

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Royal Enfield motorcycles are available new - made in India. http://www.enfieldmotorcycles.com/

Indian Institute of Technology Roorkee competed at FSAE Australasia in 2011 using this engine.

Gruntguru,

Unfortunately RE have updated the engine so that it and the gearbox are now of unit construction. The advantage I saw in the old engine was the separate gearbox that could be relocated to the front of the crankcases, for better overall packaging.

Or better yet, the gearbox could just be deleted, then some variation of single or dual chain drive used. The RE turns slowly enough that a direct final drive is possible. Less is more!

The old style engine had air-cooling with big fins, 2 valve hemi-head, approximately square bore/stroke, roller main bearings but pressure fed slipper big-end, dry-sump with separate inernal scavenge and pressure pumps and internal oil tank, and a direct drive alternator. Not too far from what I would want in a bespoke FSAE engine.

Z

Cole,

You say, "... I do have the opinion that your overall package is way out there for an FSAE car."

By "way out there" I guess you mean that you don't approve of it, and you think that it won't work?

Well, around the same time I was pushing the "brown go-kart" back in 2005, RMIT (with Geoff Pearson) built a car that was a step in that direction, and it was very successful. Quite a few more teams are now going in that direction (witness all the recent debate about "singles vs fours" that wasn't there in 2005).

However, the simple, lightweight single (with aero!) is still in the minority, so most FSAE students think that this approach is a "radical" step with lots of associated risks (eg. many think that they have to go "carbonfibre + titanium" to have a chance).

I am just trying to reassure these students that the KISS approach is in fact the easiest way to outright victory. (And please note, KISS does not mean mindlessly copying the unnecessarily complicated "standard" FSAE car.)
~~~o0o~~~

"....you've "already explained why" the single or two gear concept is better, but again, saying it and proving it are two different things. You speak these things like they are gospel when there are no results to back them up in FSAE."

Quote from Kevin Hayward in "Any way to objectively choose engine?" thread.
"Many cars in FSAE have done very well running the endurance in one gear. Even with heavy cars."

And, incidentally, Kev's old school, UWA, has successfully run soft twist-mode suspension for quite a few (?) years.
~~~o0o~~~

"... but dang those insults are getting old."

If you do something really stupid, and you are told that it is stupid, then it is only an insult if you refuse to believe that it is stupid.

A kick up the bum can be good for you. Thinking back, I wish I got a few more at certain times in my life. http://fsae.com/groupee_common/emoticons/icon_smile.gif

Z

Love this thread. I have been advocating the single with aero and beams for a while. Now the "soft twist" concept has my attention but there are so many questions. For example - in the top left Z-Bar drawing, how would you adjust RMD? Adjustable side pivot location to change A/B would be a design challenge. Would fiddling the RCH's be sufficient? Perhaps an ARB at one end? And how to select the longitudinal location of the side pivots - at the CG? Slightly further back if running a spool?

These are some of the design challenges that would make teams wary of such a radical departure from "typical" FSAE layouts.

Gruntguru,

The top-left Z-bar sketch was mainly intended just to explain the concept. In practice it could be done, but the RMD wouldn't be easily adjustable, so you would have to work that out first.

That's why I also did the bottom-right sketch with its longitudinal Z-bars. These are harder to understand, but they make it easier to adjust RMD, simply by adjusting relative A and B lengths.

One of the main advantages of beams is that they can run very soft springs, so the suspension is already reasonably twist-soft. However, to adjust ERMD you have to change springs, which can be time consuming, expensive (need lots of springs), hard to make fine adjustments, etc.

So if you have beams with longitudinal Z-bars (and perhaps soft central coils like in top-left sketch) you can more easily adjust RMD via the geometric change to A/B lengths, a relatively simple bit of mechanical detail design.

Also, I would suggest to start with a soft damper-at-each-corner. So if the Z-bars get too confusing you can scrap them and easily go back to a spring-at-each-corner (on the dampers).

Z

I should also note that "Z-Bars" can be done "2CV style" (see 2CV pic somewhere? on these pages).

So let's say you are already running push/pullrods-and-rockers, and the pivot-axes of the rockers lie in a vertical-lateral plane. Now you can interconnect the pair of rockers (F&R) on each side of the car with a pullrod that acts as a Z-bar. Ie. when one wheel goes up, it pulls the rod, which forces the other wheel down.

Practically, the Z-bar-pullrod could be a ~4mm diameter cable with its ends wrapped around pulley sections on the rockers (like those machines in gyms). Somewhere along the length of cable would be fitted a compression spring, in the fashion of the springs used on tent ropes.

Importantly, the SPRING-RATE does NOT have any influence on handling balance via ERMD. The springs are there for comfort. The ERMD (=ELLTD) is determined soley by the geometry of the rocker arms (etc...), and is thus independent of bounce/pitch/roll motions of the car, and (importantly!) of twist in the roadway.

A system like this is the only justification for "rockers" that I can think of (ie. at least here the rockers are doing something useful!). Its practical implementation would be quite easy, being similar to current layouts, and allowing flexibility in the positioning of the Z-bar-pullrod/cable runs.

(Note also: Only three Z-bars total are required for sufficient control of the suspension of all four wheels. I'll let you students figure that out...)

Z

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Originally posted by Z:


"Many cars in FSAE have done very well running the endurance in one gear. Even with heavy cars."

And, incidentally, Kev's old school, UWA, has successfully run soft twist-mode suspension for quite a few (?) years.
Z

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How are you defining "well" and "success" here? Doing well, by my definition, is putting down an endurance pace capable of giving your team an overall win. To my knowledge, no team running a single gear has been able do this. That certainly doesn't support your concept.

How successful is UWA? My definition of success is winning the competition. Not to mention, sure, UWA is soft-twist, but they are still nowhere close to your overall concept.

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Originally posted by coleasterling:
How successful is UWA? My definition of success is winning the competition. Not to mention, sure, UWA is soft-twist, but they are still nowhere close to your overall concept.
-Cole

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A pretty old list but I don't think WA's wins have been reversed.

Team Name # of Wins
Cornell University 9
University of Texas - Arlington 8
RMIT 4
Georgia Tech 3
University of Toronto 3
University of Wollongong 3
Texas A&M University 3
Sophia University 3
Graz University of Technology 2
USP São Carlos 2
University of Western Australia 2
University of Stuttgart 2
California State University - Pomona 1
Centro Univ. da FEI 1
Kanazawa University 1
Steven's Institute of Technology 1
University of Akron 1
University of Applied Sciences Graz 1
University of Houston 1
University of Maryland 1
University of Michigan - Ann Arbor 1
University of Texas - Austin 1
University of Wisconsin - Madison 1
Virginia Tech 1
Faculdade de Engenharia de Sorocaba 1

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I wasn't claiming they don't have any wins. It was a genuine question. The statement still stands, however. They build a car that is nothing like the beam-axle concept.

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There has been one more win since then, and a few more if you are only looking at dynamic wins. Not the same concept sure, but many similar outcomes. Ours is more of an "add on" way of achieving soft twist.

We have run the system for a long time, even after the sponsorship went away in the GFC. So it must have something going for it. It has no advantage in the design event, and until a judge drives it, will remain extremely difficult to justify to them.

On the flip side, Stuttgart has a pretty good dynamics record too, with a pretty similar concept but with a stiff twist mode, and the FSG track is far from flat.

So, hard to tell if the soft twist is much of an advantage, but clearly UWA, and some stop watches, thinks so.

Pete