Front Wheel Track

[CheeseheadEarl]

7/9/14
[Broken External Image]

Elio Motors Hello , the only way to roll an Elio is by reversing at 45mph and performing a sharp turn. It takes more than 0.8Gs to get us into a skid!
2 · 2 hours ago

Izzat like when the HUMMVEES first came out and were impossible to tip? Didn't take GIs long to prove that wrong.

 

[Snick]

The pull rod design itself would not relate to what we call 'suspension geometry'. The pull rod could affect geometry relating to spring rate compression(but can be designed not to), and that could get involved with roll over if the 'progressive-rate' were too soft. This is normally not as important to rollover as the actual tract width and placement of the CG within the triangle formed by the tire contact to the road. Also a minor effect is the tire pressure/loading. In both cases of softness, the ride would get sort of spungy in a turn where the body leans over, and so then the CG has moved to the outside too. A wider front-end would add to counter that effect.

As you likely remember from the CabinScooters group, truly, the height of the Center of gravity (CG) and it's forward position is the largest factor affecting the choice of width needed to have a desired resistance to rollover. In effect the width chosen is a tradeoff with [fitting on the road and aerodrag] vs [rollover safety]. Their engineering decision would have been based on that and the idea that a 6ft is not too hard to live with. Understand that the narrow rear end is still narrow and allows more freedom in turn than a four wheeler with a square shadow. Avoiding obstacles will be very easy with the Elio.

As an example, the 'indy cycle' reverse trikes often increases lateral stiffness via a solid linkage between left and right, greatly reducing that roll-over softness. This comes at the cost of allowing more bump induced body roll, and therefore less comfort, and added body shake. That vehicle has such low momentum, and that type of driver has low requirement for comfort, therefore that owner base doesn't usually mind those attributes. If you had your kid in back, you likely would. There are other tradeoffs as well. They have a far back position for their CG, so up to a 7ft width is highly desirable. More than that and it's too wide for easy driving. The Aptera also had a very wide width, or something near to that(but not the solid linkage).

My question about the pull rod is: isn't its purpose to limit front end roll upon turn-in? And if the track width were narrower, would the angle of the pull rod not affect performance of it? I don't really understand this suspension type yet very well, so any explanation helps.

Also, I am concerned about the stability with a heavy passenger in back--I do think the Cg is placed too far to the rear (wonder why they did this), and I understand that Electronic Stability Control will be necessary which is why it is going to be standard. If any of your ESC sensors fail, and you have a heavy passenger...look out.

 

[outsydthebox]

Also, I am concerned about the stability with a heavy passenger in back--I do think the Cg is placed too far to the rear (wonder why they did this), and I understand that Electronic Stability Control will be necessary which is why it is going to be standard. If any of your ESC sensors fail, and you have a heavy passenger...look out.

I suppose it could be a problem, If you push the limits all of the time.

 

[olddog1946]

My question about the pull rod is: isn't its purpose to limit front end roll upon turn-in? And if the track width were narrower, would the angle of the pull rod not affect performance of it? I don't really understand this suspension type yet very well, so any explanation helps.

Also, I am concerned about the stability with a heavy passenger in back--I do think the Cg is placed too far to the rear (wonder why they did this), and I understand that Electronic Stability Control will be necessary which is why it is going to be standard. If any of your ESC sensors fail, and you have a heavy passenger...look out.

I'm trying to figure out why you think the Cg is too far to the rear?? You have the entire front suspension, two tires and wheels, an engine and a transmission, firewall, steering column, windshield and miscellaneous all in front of the driver,,,with one seat, one tire and one swing arm behind the driver. Unless I am totally nuts, I doubt the Cg is too far back.

 

[Snick]

I'm trying to figure out why you think the Cg is too far to the rear?? You have the entire front suspension, two tires and wheels, an engine and a transmission, firewall, steering column, windshield and miscellaneous all in front of the driver,,,with one seat, one tire and one swing arm behind the driver. Unless I am totally nuts, I doubt the Cg is too far back.

The EM's Cg appears to be a bit aft of ideal. For a 200lb man driving it alone, it appears the Cg would be about where the driver's thighs are (depends on seat positioning, too, a little), but with a heavy passenger, plus any luggage in the trunk it looks like it will shift back more than is best for stability (the polar moment of inertia also increases more than for a 4 wheeled conventional car because of the thin body shape). Does anyone know the actual Cg location? I searched through some old technical talks but only found mention of how low it is (which does help, too.)

 

[CheeseheadEarl]

Does anyone know the actual Cg location? I searched through some old technical talks but only found mention of how low it is (which does help, too.)

In one of the tech talks, there was a 70/30 F/R weight split mentioned. I assume this is empty, but you know how assuming works...

I don't know where the fuel tank is located, 8 gallons of fuel is somewhere around 55#, driver weight "looks" like it would shift CG back slightly, a passenger more so, but - it's all inside the triangle, unlike say loading the trunk of a conventional auto or trailer tongue weight, which being behind the rear axle create a more than 1:1 transfer of weight front to rear.

The .8G on the skidpad (theoretical I assume...again) is pretty decent - I just looked at a Car and Driver test - a 2014 Impala with the big 19" rubber did .82G - it's not a sports car, but they get around corners darned well for a car it's size. My '04 would start losing grip at around double the posted corner speeds. If the Elio handles like that, I'll be happy.

 

[goofyone]

In one of the tech talks, there was a 70/30 F/R weight split mentioned. I assume this is empty, but you know how assuming works...

I don't know where the fuel tank is located, 8 gallons of fuel is somewhere around 55#, driver weight "looks" like it would shift CG back slightly, a passenger more so, but - it's all inside the triangle, unlike say loading the trunk of a conventional auto or trailer tongue weight, which being behind the rear axle create a more than 1:1 transfer of weight front to rear.

The .8G on the skidpad (theoretical I assume...again) is pretty decent - I just looked at a Car and Driver test - a 2014 Impala with the big 19" rubber did .82G - it's not a sports car, but they get around corners darned well for a car it's size. My '04 would start losing grip at around double the posted corner speeds. If the Elio handles like that, I'll be happy.

What I have been told is that the Elio is designed to be equally balanced on all three tires with a full load of fuel and a 180 lb driver which matches pretty well with the listed 70/30 weight distribution number. FYI, the fuel tank is located in a structurally reinforced compartment under the passenger seat.

Based on what I have read and been told Snick would be correct that the presence of a passenger would shift the CG towards the rear potentially leading to snap oversteer situations. This is relatively easy to overcome using the included stability control system however, as Snick also mentions, it is something Elio drivers should be aware of.

 

[outsydthebox]

What I have been told is that the Elio is designed to be equally balanced on all three tires with a full load of fuel and a 180 lb driver which matches pretty well with the listed 70/30 weight distribution number. FYI, the fuel tank is located in a structurally reinforced compartment under the passenger seat.

Based on what I have read and been told Snick would be correct that the presence of a passenger would shift the CG towards the rear potentially leading to snap oversteer situations. This is relatively easy to overcome using the included stability control system however, as Snick also mentions, it is something Elio drivers should be aware of.

Anything that we do in ANY vehicle, requires us to exercise common sense. We cannot reason that, " because I took that curve yesterday (when it was sunny and dry) at 50mph, I should be able to do the same thing today...when it's raining, or snow covered. We also need to remember that this is designed primarily as an economy vehicle, and should be driven accordingly. If not, we should be willing to accept responsibility for our actions.

 

[Folks]

Anything that we do in ANY vehicle, requires us to exercise common sense. We cannot reason that, " because I took that curve yesterday (when it was sunny and dry) at 50mph, I should be able to do the same thing today...when it's raining, or snow covered. We also need to remember that this is designed primarily as an economy vehicle, and should be driven accordingly. If not, we should be willing to accept responsibility for our actions.

I doubt any of us will reach a testing point of the Elio's stability thresholds in normal driving conditions. Certainly the exceptions are conditions of wet leaves, gravel, sand, snow and Ice. In those cases most, I'm willing to bet, are just too timid to move to an area of nil traffic and test braking and steering and various speeds. Especially in black ice and freezing rain. I've but one experience in rain on sheet ice that after easing to a complete stop I sneezed causing the car to slide sideways to the curb. With that exception I'm willing to bet after building a more confidence to test skid our vehicles in a no obstacles area we'll build a little more confidence in those slip and slide conditions. Testing as such will make great conversation when we get our Elios.

Of course there are a few here that will need the moon to be in the seventh house and Jupiter to alien with Mars before they will ever attempt a skid test. LOL

 

[Edward43]

I doubt any of us will reach a testing point of the Elio's stability thresholds in normal driving conditions. Certainly the exceptions are conditions of wet leaves, gravel, sand, snow and Ice. In those cases most, I'm willing to bet, are just too timid to move to an area of nil traffic and test braking and steering and various speeds. Especially in black ice and freezing rain. I've but one experience in rain on sheet ice that after easing to a complete stop I sneezed causing the car to slide sideways to the curb. With that exception I'm willing to bet after building a more confidence to test skid our vehicles in a no obstacles area we'll build a little more confidence in those slip and slide conditions. Testing as such will make great conversation when we get our Elios.

Of course there are a few here that will need the moon to be in the seventh house and Jupiter to alien with Mars before they will ever attempt a skid test. LOL

I (laughingly) assume it be time to implement a sneeze arrestment system.