Comments From A Mechanical Engineer

[NSTG8R]

I hope to add a bit of clarification to the wheel spin and suspension questions. I wrenched for many years, raced both cars and bikes, and love the thrills they bring. (Even at my old age)
Differentials, both rear wheel drive and transaxles, have planetary gears inside, allowing each axle exiting them to spin at different rates as needed. When you turn a corner the inside wheel is spinning at the rate the ring and pinion assembly is, the outer wheel rolls faster than that due to "free wheeling planetary gears". For those who already have front wheel drive, accelerate harder out of the corner and notice how your steering wheel tries to turn you straight! That's the inside wheel catching up with the outside one.
A limited slip or positrack differential uses springs and friction plates to put pressure on the planetary gears. This increases dramatically the force needed to make one wheel spin, while the other "floats" along. Useful for drag strips and most circle tracks, but usually not needed for everyday driving. A locked rear end is just that, both wheels turn at the same rate no matter what. Locked rear ends don't allow for smooth cornering, but force a person to burn some rubber to bring the car around. If you lock the rear end, you've pretty much ruined the handling of that particular vehicle for anything except straight lines.
I've commented before on how much I like the front suspension on the P4, but didn't elaborate much. What it has is called a double wishbone suspension. Even without a sway bar it will handle very well indeed! With a sway bar there isn't many cars on the road that will do better. Look at Indy cars, euro racing cars and road racing cars. Odds are you will see the double wishbone suspension!
The double wishbone causes the the downforce of the vehicles weight to be applied at the top part of the tire assembly. This allows the tires to remain a lot more upright (eliminating the tires folding under in the corners) while cornering! The benefits are, weight is distributed to three firm points as well as the other side of the vehicle, the upright tires allows all the tread to remain on the ground, the weight is added proportionatly instead of instantly, rebound rates are very mild AND you end up with a very stable ride.
Sorry so wordy, and I hope I didn't add confusion for anyone. I work graveyards and have stayed up to watch the ballgame today, so I plead ignorance for any mis spelled words on this particular day...
Edited for th brake questions. I expect the Elio will have either a 70-30 or 80-20 perportioning system, with most of the braking being the front wheels of course..

Nice write-up Bert! Very well explained...and I completely forgot about the proportioning valve. Got an adjustable Wilwood on my Porsche due to the different front/rear tire sizes.

 

[wheaters]

actually, the breaking should have the ability to sense the weight distribution of the vehicle and balance the braking forces according to the total weight distribution, like the later model goldwings do.

That's what ABS does, but not directly. Each wheel has a sensor in proximity to a toothed or slotted ring. If one wheel is running slower than it should, under braking, the brake line pressure is reduced to that wheel.

I think I read that the Elio will have ABS..

 

[D Borland]

A

I've been exchanging info about Elio Motors with a good friend who has degrees in both mechanical and electrical engineering .... he's also owned/driven motorcycles for well over 40 years, currently owns 2 nice Harley cruisers .... as a result of me asking him to look into it, he sent the following :

"IMHO it should have been designed to drive the rear wheel and keep the front end light enough to lift one of the front wheels in a hard turn. Put the trunk in the front engine over the rear wheel. With some caution (I could be wrong) I believe this design is going to drive like a square fronted boat. With three wheels something has to shift in a turn. With 4 wheels the weight shifts and the platform remains parallel to the ground. With three wheels the same weight shift causes a lean over the single wheel, you can't fix that so you have to go with it and allow something to roll over. Otherwise you need an acre and a half to make a flat turn without the roll.

Three wheel design = drive the single wheel and allow the front end to take up the roll required to make a turn. Morgan has this right."

I have gone back and looked at every YouTube Elio video that I can find and I haven't seen any which show it in a sharp turn .... in thinking about it, the Elio is designed to be a commuter vehicle which usually doesn't require traversing a slalom course .... that said, I have no doubt that some folks are bound to give it a try .... I'm looking forward to a test drive, hopefully that will be possible next year

Jim

More investigation is needed by your friend. I don't believe he had seen all of the footage. They have run a
Slalom and it did very well.

 

[wheaters]

I can strongly agree with Bert's comments about double wishbone front suspension. My Liege has it and it handles extremely well, better than most modern cars can. It out handles my son's BMW, to his amazement, even though the tyres are 145 section cross ply (bias belt), designed 60 years ago.

 

[goldwing06]

I can strongly agree with Bert's comments about double wishbone front suspension. My Liege has it and it handles extremely well, better than most modern cars can. It out handles my son's BMW, to his amazement, even though the tyres are 145 section cross ply (bias belt), designed 60 years ago.

in agreement on the suspension and realize the coil over shock is light weight but for the long haul, torsion bar suspension is superior and adjustable for aging or performance tuning. the torsion bars also add rigidness to the frame for crash protection. works well with double wishbone arms but the lower one needs to be stout enough to be the supporting arm. probably won't fit in to pauls design scheme though.

 

[JEBar]

actually, both wheels received equal turning force from the differential assembly. if the driving wheels were making a turn, the outer wheel would need to travel further than the inner wheel, thus the differential would allow the difference in travel speed while still applying rotating force to both axles. if the traction was such that one wheel was allowed to slip, the drive shaft would continue to apply the same force but the differential would allow all the force to be sent to the wheel with the least resistance.)

info makes sense and is appreciated

Jim

 

[Bert]

I had a 67 Cuda formula S fastback, 383 4 spd. Oh those were the days.. LOL. The torsion bars suspension is a great one, but it needs a very heavy and durable cross member to keep the frame from twisting. I learned overthe years how to plate that cross member after a few of the torsion bars broke through! They don't allow for the weight to be distributed though, and the lower ball joint takes a pounding, as it's the focal point of pressure at the wheel.
As a side note, I practically went broke replacing U joint on that one, but man was it worth it.. LOL

 

[wheaters]

Torsion variety suspension..... Morris Minor Traveller, my wife's first car, before we were married. A total nightmare to fix, especially when the chassis crossmember is past it's best! The front suspension's threaded lower trunnions needed regular oiling. We discovered this the hard way....the ones on this car hadn't been serviced and the trunnion was worn out.

When this happens, the internal threads lose engagement, the torsion bar forces the trunnion apart so that the lower end of the suspension leg is no longer supported. The entire car falls off its front suspension on that side, the wheel splays out from under the wing and the car drops to the ground....

On my wife's car the front wing was ripped off as two burly truck drivers tried to lift the car back onto four wheels. End of car!

 

[goldwing06]

ick

Torsion variety suspension..... Morris Minor Traveller, my wife's first car, before we were married. A total nightmare to fix, especially when the chassis crossmember is past it's best! The front suspension's threaded lower trunnions needed regular oiling. We discovered this the hard way....the ones on this car hadn't been serviced and the trunnion was worn out.

When this happens, the internal threads lose engagement, the torsion bar forces the trunnion apart so that the lower end of the suspension leg is no longer supported. The entire car falls off its front suspension on that side, the wheel splays out from under the wing and the car drops to the ground....

On my wife's car the front wing was ripped off as two burly truck drivers tried to lift the car back onto four wheels. End of car!

wow! sounds more like shoddy design or no preventative care. lower ball joints have carried the weight of the front end of cars for the last 40 some odd years and yes they do wear and some wore quicker than others but so did king pins back in the day too. chrysler has been a leader in torsion bar design since the 57 plymouth. it worked well on the first dakota pick ups too. i'm content to wait on the elio to be produced as paul and staff sees fit and worry about improvement, if needed, later.some of this stuff is just fun to talk about though. hey, anyone remember studebakers hill holder brake device?

 

[ehwatt]

I'm with skygazer on this one. The weight in the back could create understeer in cornering. I had a VW bug back in the day, and while it got good traction in the snow, it was pretty scary in the slick stuff...kept wanting to go straight! I do remember a video of the P3, I believe, taking a slalom course. I didn't have a sway-bar on it, so there was a little body roll, but for the most part, it seemed pretty agile.

It seems that rwd autos with the engine last (not rear, mid-engine) generally understeer with power and the opposite without it. This induces the infamous trailing-throttle-oversteer and the need then, of course, to dial in "just enough" oversteer to point the nose like the earlier Porsches and the Elise with the rear weight bias it was deliberately given and yes, even those old VWs would bite if you're running in the snow or gravel and chop the power.

Rwd sportyy cars used to lift a front tire because of chassis flex. Lotus depended on chassis flex in the handling. Now they're so stiff you can get three tires on a Corvette off the ground with one jack.

For the safety of the general public it will likely have a relatively wider rear tire which will allow it greater lateral traction than the smaller fronts, resulting in safer understeer. This will be fairly easy to balance with tires, spring/shocks etc, even tire pressures.

When the power is abruptly reduced in fwd cars in a corner they tend to tuck the nose in tighter because of the forward shift of weight causing increased traction. And to beat all else, when a fwd sporty car is hard in a corner, it lifts the REAR tire.

I