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Old 08-09-2012, 06:49 PM   #1 (permalink)
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5th Wheel Aero Tail with E-motor

So, I'm surprised I'm having such a hard time finding this, someone has to have tried this. I am familiar with a lot of 5th wheel projects but has anyone built one into an aero tail? A retrofit that wouldn't require messing with the existing drivetrain.

Are there any inherent bad reasons for having a fixed (vs trailered) driven 5th wheel?

I have an Insight and have been looking at the tail project on here. But, I've also been trying to figure out the best way to add a plugin EV drivetrain to the car. There are a number of solutions, but most involve significant modding of the actual car body and/or mechanics.

In fact, I was thinking it would be cool to have a bolt on belly pan with aluminum rail frame that goes back to become an aero tail with a 5th wheel driven by a e-motor. Depending on space constraints, I could fit some batteries in either the hatch back stowaway compartment or in the tail itself, or both.

On the surface, seems a doable idea. Clearly ambitious though, and I'm hoping that some of you folks can poke some holes in this idea before I try to get started.

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Old 08-10-2012, 04:27 PM   #2 (permalink)
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So I did a crude mock up drawing, hope it makes sense. The idea is to just bolt this to the underside. The idea is to get the aero benefits and a plug-in hybrid all in one piece. Theoretically it could be taken on and off relatively easily.
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Old 08-10-2012, 04:58 PM   #3 (permalink)
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Okay, so after more research, it appears that you do have tire scrub issues if the 5th wheel forms a fixed triangle with the rear tires and the amount of scrub is proportional to how much the wheel sticks from the rear wheel axis.

So you would have to have the 5th wheel on a pivot point like a trailer or your tires would get bald really fast. That means that the tail couldn't be quite as streamlined with the body because it would also have to allow for some side to side movement. However, it could still work, but not as I had hoped!

Thanks for all the input.
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Old 08-10-2012, 06:23 PM   #4 (permalink)
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I've seen the fifth e-wheel made for the Insight. It's a really simple motorcycle type chain drive with an actuator or hydraulic pump that lowers it and presses it into the ground. That part is key, It needs to have force applied pushing it into the ground for traction and power. The prototype was mounted just to the left of the rear right wheel attached to where the spare tire well is. That is the best place to put it, simple and efficient.

Another problem with mounting it on the tail is you have inconsistent traction on the wheel as it goes over wavy hills and dips. An EV trailer type trailing arm would work, but it's better right next to the rear wheel. Best to keep them seperate.

The problem with a fifth wheel is that the prototype doesn't have the power required for freeway speed cruising. It's more accelerating from a stop and cruising around 35mph. Thats ok for some people, but if you want a serious EV mode plug in hybrid type deal, Then do a partial EV rear wheel conversion. Get some good motors.

If you just want a fifth wheel, from what i saw it looked easy to fabricate if you can weld and all that stuff.
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Old 08-10-2012, 07:10 PM   #5 (permalink)
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Hey sheepdog,

I assume you're referring to Mike Dabrowski's 5th wheel. Yeah, what he did was very difficult. I'd rather do something more simple. I see that there is no way to get around having the trailer hitch. I didn't think about up and down movement along the road though. Thanks for that heads up. I guess I would have to have some side to side play and up and down play. Basically all X-Y-Z axes. Thus the ball joint type hitch that is used for trailers.

I have been keeping an eye on Agni motors as they have a great power to weight ratio. Only 25lbs and their up and coming version is supposed to have 30kW cont rating. That was the biggest problem with Mike's version is that he used an underpowered motor. He had acceleration issues as well.

I believe that with the Agni you could get onto the freeway and cruise at 60mph. Although, for me it would be most useful as a street mode and/or extra assist on the freeway to achieve the max 150mpg.
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Old 08-10-2012, 07:20 PM   #6 (permalink)
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Yeah, but his build is really simple actually. It just bolts on underneath the car. Really easy to make if you know how.

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