Heavier REGEN as a safety feature?

Fast Eddie B

Fast Eddie B

Well-Known Member
I’ve never driven a car with heavier REGEN than the Clarity, but I know such exist, so as to provide almost one-pedal driving.

Let me tell you what just happened...

We were driving from our E TN home to our N GA digs. It was quite dark as we drove along the Ocoee river, maybe 45-50 mph, up a slight grade approaching Ducktown, TN. A quite large deer jumped right to left, directly into our path. I had split-second, just enough time to maybe get my foot off the throttle and headed towards the brake, twitched the steering wheel slightly right and missed him by no more than a foot. Whew!

First off, the car did not brake itself. I think the deer was just too close. But I was in SPORT mode with 4 chevrons of REGEN*, so I maybe got a smidgin of deceleration from that. But heavier REGEN might have been more beneficial - any slight reduction is speed/inertia helps limit damage and/or injury.

What do you think? Might heavier REGEN enhance safety in emergencies?


*SPORT with Max REGEN is my SOP.
 
Any slowing/brakes makes things better in that situation. If you hit a large object like a deer, you impart some of the car's momentum to it. The more you slow down immediately after you hit it (either brakes or regen) the more likely the imparted momentum is to have time to move said large object forward instead of your car getting ahead of it and it coming through your windshield (and in the case of a deer, possibly crushing or impaling you).
 
Fast Eddie B said:
What do you think? Might heavier REGEN enhance safety in emergencies?
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Well, you have a scenario where greater REGEN could have helped.
I'm sure there are other scenarios where it could have been a detriment.
All-in-all, the contribution of REGEN to safey (either way) seems trivial to me.
 
It would certainly apply some braking force during the time period from which the foot comes off the accelerator and is placed on the brake pedal. That time period is somewhere around 1/2 of a second for the average driver.

In many emergency situations, slowing would seem to be the logical choice to achieve a desirable outcome. There could be a rare occasion when accelerating may get one out of a pickle. Lifting off the throttle is probably the most common initial reaction, regardless of whether or not it is the correct reaction. I’d say 99% of the time having additional braking force would be beneficial, in many emergency situations.
 
DucRider said:
If you brake after hitting the deer, it is less likely to go thru the windshield? My best stab at it.
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You'd better already be breaking by the point of impact. The more you continue to decelerate compared to the now accelerating carcass, though, the less force it hits the glass with.
 
DucRider said:
If you brake after hitting the deer, it is less likely to go thru the windshield? My best stab at it.
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Yeah, I had a little trouble parsing it.

I vaguely recall a Mythbusters where the tested whether hitting something faster is ever a benefit. Pretty sure the answer was “no”. I can’t find a link right now, but I did find this:



OUCH! “Our” deer was large enough to have come through the windshield, but the timing was such that we would have clipped him with out left front fender. We were both surprised there was no impact - it was that close.
 
petteyg359 said:
Physics.
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I think I get the physics.

As a flight instructor, I often have to point out the relation of speed and kinetic energy. Mainly to get the point across that with landings, slower is better.

To make that point it’s important to know that kinetic energy increases as the square of a speed increase. Our brains tend to think linearly. For example a 100 mph hurricane sounds twice as powerful as a 50 mph tropical storm. In fact, it carries four times the punch.

To show this effect when landing, I came up with a tiny Excel spreadsheet:

23659991808_551484ec0c_o.png


Back on point, heavier REGEN in the split-second it takes to get your foot on the brake would only make a small difference in impact velocity, but that even that small difference might help in reducing damage and injury.
 
Fast Eddie B said:
I think I get the physics.

As a flight instructor, I often have to point out the relation of speed and kinetic energy. Mainly to get the point across that with landings, slower is better.

To make that point it’s important to know that kinetic energy increases as the square of a speed increase. Our brains tend to think linearly. For example a 100 mph hurricane sounds twice as powerful as a 50 mph tropical storm. In fact, it carries four times the punch.

To show this effect when landing, I came up with a tiny Excel spreadsheet:

23659991808_551484ec0c_o.png


Back on point, heavier REGEN in the split-second it takes to get your foot on the brake would only make a small difference in impact velocity, but that even that small difference might help in reducing damage and injury.
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So over the numbers at around 46 kias and landing with stall at 41 kias.
 
PHEVDave said:
So over the numbers at around 46 kias and landing with stall at 41 kias.
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I try to land at the slowest possible speed, which should normally be at or near the plane’s stall speed in any given configuration. The point of my example was that if a pilot landed at 46kias when they could have further slowed to 41kias before touchdown, they’d be carrying 26% more kinetic energy to be dissipated somehow in the event of a mishap. Same thing would apply to hitting a deer - or a moose! - at 46 mph rather than 41 mph.

As far as approach goes, the rule-of-thumb is to approach at 1.3 x the stall speed, or 1.2 for a short field. That gives a 30% or 20% margin above the stall for safety. If gusty, you further add 1/2 of the gust velocity.
 
DucRider said:
If you brake after hitting the deer, it is less likely to go thru the windshield? My best stab at it.
Click to expand...

The slower you're moving the less chance of impacting the deer with your windshield instead of it bouncing off the hood. But braking after it is hit? Hmmmm

LOL, I had "it's" hit originally. The filter took that as s h i t even with the space between the s and hit. Breaking out into "it is hit" doesn't.
 
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Fast Eddie B said:
I try to land at the slowest possible speed, which should normally be at or near the plane’s stall speed in any given configuration. The point of my example was that if a pilot landed at 46kias when they could have further slowed to 41kias before touchdown, they’d be carrying 26% more kinetic energy to be dissipated somehow in the event of a mishap. Same thing would apply to hitting a deer - or a moose! - at 46 mph rather than 41 mph.

As far as approach goes, the rule-of-thumb is to approach at 1.3 x the stall speed, or 1.2 for a short field. That gives a 30% or 20% margin above the stall for safety. If gusty, you further add 1/2 of the gust velocity.
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My plane has two rudders that work independently of one another. One for each pedal. So if I come in a little hot I can briefly deploy both rudders to drain off a little speed before landing.
 
My compact, sporty BEV's regen braking is great for planned deceleration events, but it isn't nearly as powerful as stomping on the brake pedal.
 
insightman said:
My compact, sporty BEV's regen braking is great for planned deceleration events, but it isn't nearly as powerful as stomping on the brake pedal.
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I would not expect it to be - just maybe help a tiny bit more in the short but measurable time delay it takes to get your foot over to the brake pedal. And anything even borderline aggressive would definitely need to trigger the brake lights using some sort of g-measuring sensor, as Tek_Freek suggested.
 
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