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Learning how to build Lotus Seven replicas...together!
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PostPosted: October 9, 2021, 11:20 pm 
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Joined: December 13, 2007, 9:37 pm
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Location: Pelham, NH
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This thing constantly gives me chills. Please tell me it looks fun and I should build it.

I would love all kinds of feedback. Everything is changeable.

$6,000, 864lb - Two Chevy Volt battery packs, used, 36.8kWh
$2,400, 156lb - NetGain Warp 9 motor
$2,875, 16lb - Zilla 1k controller + hairball
---------------
$11,275, 1036lb - I haven't bought anything

Motor coupled directly to the pinion shaft of an IRS LSD diff, possibly Ford 8.8" (rotated backwards, do diffs hate being run primarily backwards?).

The major components, plus driver, are positioned approximately to put the center of gravity exactly centered between the axles.

I've been dabbling in design for a long time. I think I've finally about settled on what I want to build. I still need to build a mock-up of the cabin to see how it feels. I still need to figure out exact steering and suspension geometry. Inboard coilovers, outboard brakes. Some kind of FSAE style anti-roll. The Porsche 911 steering rack that Kinetic Research mentioned sounds like it could be a good fit.

I'd rather start with an Internal Combustion Engine, honestly, just because parts are so much cheaper. But the 9.9" from the bottom of the oil pan to the top of the drive shaft I just cannot get to work, aesthetically (there are old models on my website).

SCCA cage rules say 1.375" x 0.080" round tube, bent, for the roll hoops, for up to 1700 pounds. But compliance seems impossible because I want to use cut and welded square tube. Plus they don't allow non-production electrics. So, I'm thinking 1.5" tube for the roll hoops (primary behind the passenger, plus all the way at the front), and 1" for everything else? Wall thickness?

I have no building experience. I change my own oil and brakes. I'm mechanically inclined. I'm hoping the simple shape will make it a little easier on me, compared to those of you who use things like compound curves. For a long time I figured I'd be learning to use an English wheel, or fiberglass molding, I just ended up liking this shape more. I figure first steps are find somebody with a welder I can practice on a bit before buying one. I'm a computer geek, I run linux. I'm modelling in blender, which is free. I live in Pelham, New Hampshire.

I want a TIG welder, because I care more about making it pretty than doing it fast. I got time. Maybe just a used DC (not AC/DC) welder to start with though, because I'm currently just interested in steel.

I want 245/40-24 tires / wheels. That gives me about the same sidewall as OEM 1995 BMW M3, with the tall tires I want for aesthetics. But they seem... hard to find. I'd rather use parts that are easily available. 245/60-20 has about the same outer dimensions, and is commonly available, but that seems like way too much sidewall. These both would give me about 1.4x the contact patches of the M3, if you can do that by just multiplying diameter x width. I'd be happy with less, exploring the limits of traction is more fun that perfect sticking.

I know it's a very ambitious project, but I'm happy to see less ambitious than some around here. I figure on building it a couple times for practice.

I have a 2003 CBR1100XX. "It's more fun to ride a slow bike fast than to ride a fast bike slow." So, I'm not going for the fastest, I'm going for the most fun, which I can actually push without instantly exceeding speed limits. I'm very grateful for my too fast Blackbird with its endless throttle, but that's not what I'm looking for in this build.

A lot of stuff says electric motors don't need a transmission, multiple gears. All the torque from 0 rpm and all that. I'm obviously planning to take advantage of that. And will need to change the diff gearing to be able to do highway speeds without exceeding the motor's max rpm, but they're available. But I'm still a little concerned about stuff I've heard about optimal power bands with electrics - not entirely certain I'll be happy without a transmission. But I think it'll work.

The Ford 8.8" diff pinion has a 2" horizontal offset, is there a more symmetrical decent option?

The batteries and controller are liquid cooled. The motor isn't, which I'm not happy about.

Oh, yeah, I think I'm going to design my own windshield wiper mechanism :?
A lot of busses have a wiper that stays vertical. I figure that basic concept shouldn't need to be changed much so one wiper can be lined up with the edge of the windshield at each side.

Website: https://www.eternalmachinery.com/ecar/
There are 4k 60fps 53 second video loops to download. They're about half a gigabyte, I don't recommend trying to play them in a browser.

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PostPosted: October 10, 2021, 12:36 am 
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I like it, hope you build it. Tandem is great for aero profile.


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PostPosted: October 10, 2021, 12:51 am 
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Yeah, that's why I haven't gone down Electric Road, as $11K just for the drivetrain is a bridge too far (for me). But since I'm spending your money, I think that you should build it. In fact, since my money isn't at stake, have you considered making it 4WD with a second motor up front?!

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PostPosted: October 10, 2021, 12:48 pm 
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Location: Pelham, NH
Kinetic Research wrote:
I like it, hope you build it. Tandem is great for aero profile.

Thanks. Hah, yeah, but nothing else about this design is. I used to be completely obsessed with aerodynamics. The first time I modeled with tandem seating may have been inspired by somebody cutting off the passenger side of their cabin, on ecomodder.com, to reduce cross-sectional area. But over the years, I realized aerodynamics wasn't a thing that got me excited, so I gave up on it. Probably most because of the Avion, which set the Guiness record for fuel economy at 103.7 mpg diesel in 1986, using a Volkswagen Rabbit engine (not hybrid). And it looks great. And nobody cares. The Prius has never been impressive.

I used to lament how sexy open wheeled cars were, because they're so aerodynamically awful. Then I gave in.

KB58 wrote:
Yeah, that's why I haven't gone down Electric Road, as $11K just for the drivetrain is a bridge too far (for me). But since I'm spending your money, I think that you should build it. In fact, since my money isn't at stake, have you considered making it 4WD with a second motor up front?!

Thanks. Yeah, the price is rough. But I haven't managed to want anything else, and I want this.

Yeah, I've thought about all wheel drive. That may have stopped when I read this article about a two engine classic Mini Cooper. I like having all the front traction for steering (and braking). For sporty cars, I love the balanced feel of rear wheel drive, balanced center of gravity, and four matching tires. For off road, I'm real happy with my 2010 Tacoma.

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PostPosted: October 10, 2021, 2:05 pm 
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Cool, had not heard of the Avion. It's been years since I ventured onto ecomodders.

I get the feeling spats and fully encased wheels are coming back into style, reference the rolls Royce silent shadow. Could suit both your aero goals and styling goals?


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PostPosted: October 10, 2021, 2:54 pm 
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The sporting cousin of the Cybertruck. I like it. Instead of a tilt up canopy, you could incorporate a sliding canopy like vintage aircraft.

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PostPosted: October 10, 2021, 4:07 pm 
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Kinetic Research wrote:
Cool, had not heard of the Avion. It's been years since I ventured onto ecomodders.

I get the feeling spats and fully encased wheels are coming back into style, reference the rolls Royce silent shadow. Could suit both your aero goals and styling goals?

Thanks, I've played with that idea, I think I'm happier just giving up on aerodynamics.

RTz wrote:
The sporting cousin of the Cybertruck. I like it. Instead of a tilt up canopy, you could incorporate a sliding canopy like vintage aircraft.

Hah, yeah, I wondered how long that would take. I started modelling this basic shape five years before the Cybertruck was announced. Which probably made me less surprised by it that most people - it has a structural elegance that I sympathize with. Thanks. Yeah, I could do a sliding canopy. I think I prefer the aesthetics of the flipping canopy more, and I don't think sliding would be easier?

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PostPosted: October 10, 2021, 4:57 pm 
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Darxus wrote:
But over the years, I realized aerodynamics wasn't a thing that got me excited, so I gave up on it. Probably most because of the Avion, which set the Guiness record for fuel economy at 103.7 mpg diesel in 1986, using a Volkswagen Rabbit engine (not hybrid).
The designer/builder/owner bumped it up to 114 mpg about ten years ago, after converting the powerplant over to a Smart Car diesel (which is not available in the US). An even better freeway flyer than my MAX*, at slightly over 100 mpg.

*Kubota-powered Locost with a Lola Mk1 body

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PostPosted: October 10, 2021, 6:04 pm 
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Location: Pelham, NH
JackMcCornack wrote:
*Kubota-powered Locost with a Lola Mk1 body

It's fun to see somebody familiar. 9 years ago I wanted to build a VW L1 shaped car with a Kubota engine, because of your car.

For entertainment, my last post here, 14 years ago, time is weird: http://www.locostusa.com/forums/viewtop ... =32&t=2988

I first told a friend, who was a car guy, that I wanted to design and build a car 20 years ago. His response was "No you don't." I guess it's about time.

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PostPosted: October 10, 2021, 6:51 pm 
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Location: San Tan Valley, Arizona
"Motor coupled directly to the pinion shaft of an IRS LSD diff, possibly Ford 8.8" (rotated backwards, do diffs hate being run primarily backwards?)."

Why rotate the differential backwards? The Warp 9 electric motor is double ended.


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PostPosted: October 10, 2021, 6:55 pm 
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waltj wrote:
"Motor coupled directly to the pinion shaft of an IRS LSD diff, possibly Ford 8.8" (rotated backwards, do diffs hate being run primarily backwards?)."

Why rotate the differential backwards? The Warp 9 electric motor is double ended.

To put the motor directly behind the rear axle. So the passenger can be directly in front of it.

Oh. That means while driving forward the diff would be rotating in the direction it was designed to rotate while driving in reverse. And I don't know if the gears are cut asymmetrically or something in a way that would have a problem with that. I guess I should be able to find out if the ring and pinion for front diffs are identical.

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PostPosted: October 10, 2021, 7:01 pm 
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I know that some diffs have reverse rotation gear sets available for use in front axles in 4x4s Not sure about 8.8s but it is the proper way to get reverse rotation. If you spin in the wrong way, oil doesn't get pumped to the small pinion bearing.


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PostPosted: October 10, 2021, 7:08 pm 
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Sean in CT wrote:
I know that some diffs have reverse rotation gear sets available for use in front axles in 4x4s Not sure about 8.8s but it is the proper way to get reverse rotation. If you spin in the wrong way, oil doesn't get pumped to the small pinion bearing.

Nice, that makes sense, thanks. I believe I saw that there are Ford 8.8" front diffs (yup, F-150), and I need to get different gearing anyway. Hopefully everything will fit together. And I'm not attached to that diff, should be able to find something.

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PostPosted: October 12, 2021, 11:58 am 
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Darxus wrote:
Sean in CT wrote:
I believe I saw that there are Ford 8.8" front diffs (yup, F-150), and I need to get different gearing anyway.


Like you found, the F-150 has an 8.8 up front and Ford offers a decent selection of ratios for it. You can also get a Torsen or other locking differential if you want traction for all of those electrons.

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PostPosted: October 12, 2021, 5:24 pm 
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Then you need another controller to control the two controllers and act as your center diff.

Yesssssss, all wheel drive so all the torques can be utilized.

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