1980 C3 Corvette Conversion

13890 Views 12 Replies 5 Participants Last post by joekitch, Jun 3, 2019

LunaTech

Discussion Starter · May 4, 2017

There's only one other thread, but I decided to make this the main thread before things got too out of hand. Here's the old one for reference. http://www.diyelectriccar.com/forum...ible-corvette-stingray-conversion-183714.html
So did a TON more research and heres where I'm at
The problems I have found, after some preliminary calculations
-The C3 Corvette has a curb weight of 3500 pounds, much to heavy for my range and weight goals. But determined to use it, I'm trying to use me and my dads engineering backgrounds to determine the best possible way to reduce some of the weight.
-Budget: My budget of $1500 for the donor makes it difficult to find a c3 corvette in good shape. In GOOD shape. But that doesn't mean I can't find one with a rotten frame. Tying into the first point, I'm reconstructing the ladder frame with carbon fiber, or magnesium tubes (round or square). This will be sturdier and lighter. The frame itself doesn't weigh much I'm aware, but any reduction is more range.
-Getting the Tesla styled touchscreen working: Still haven't figured out any solution for connecting the car to this. I was going to extract the can bus system from a donor scrapyard car, install it, and hook it up via OBDII to a scrap skylake i7 pc, and 17 inch laptop screen. But then I learned can bus didn't work that way. I refuse to drop the idea. Quiet rationality. I don't need you.
-Battery Packaging: This has more to do with frame design and weight. My original box idea might not be very good if I'm going for weight reduction on the structure, especially using expensive material like carbon fiber. Will need to run more thorough calculations.
-I can't decide on my EV components, until I have a grip on the rest of the information.

The First Steps
On that note if you read my first post you know what my first step will be...
Step 0.5) Actually obtaining my G2 License. Starting lessons. Wish me luck.
Step 1) Drawing the concept interior, and calculating accessory power draw. Drawing is almost done. Just need to do some math. That’s fine, I like math.
Step 2) Producing some engineering drawings, and running more detailed calculations to determine the material that I will be opting for. I'm going to try to have the drawings done by May 15th.
Step 3) Starting the search for a C3 Corvette. And by that I think I may have already found one for $1200 through the power of Kijiji.

So yeah, all in all im at the stage of "if i dont go through with this I'm going to hate myself until I do"
So this is happening
As for thread updates, i'm prob going to do weekly updates, depending on how much i get done on this.

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WolfTronix

· #2 · May 4, 2017

I have always wanted to do a C3 Corvette Conversion too.

The later 1980–1981 C3 Corvette (with the 190HP engine, and automatic transmission) would be ideal for me, since no one wants them... and the local Corvette club won't mind if you convert one into electric.

Perhaps when I get done with my truck.

My plan is to use dual Siemens 1PV5135 4WS14 AC Induction motors, belt drive (4:1) to the differential drive shaft.

Like on my truck, but with much wider belts:

I already have two Azure Dynamics DMOC 645 controllers, I would need to acquire another Siemens motor...

I would power it with two Nissan Leaf battery packs.

I even got the digital dash and everything working years ago:
https://youtu.be/za_pqhRaySY

I think it would be a fun car to drive.

I wish you luck on your build.

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LunaTech

Discussion Starter · #3 · May 5, 2017

WolfTronix said:
I have always wanted to do a C3 Corvette Conversion too.

The later 1980–1981 C3 Corvette (with the 190HP engine, and automatic transmission) would be ideal for me, since no one wants them... and the local Corvette club won't mind if you convert one into electric.

Perhaps when I get done with my truck.

My plan is to use dual Siemens 1PV5135 4WS14 AC Induction motors, belt drive (4:1) to the differential drive shaft.

Like on my truck, but with much wider belts:

I already have two Azure Dynamics DMOC 645 controllers, I would need to acquire another Siemens motor...

I would power it with two Nissan Leaf battery packs.

I even got the digital dash and everything working years ago:
https://youtu.be/za_pqhRaySY

I think it would be a fun car to drive.

I wish you luck on your build.

I'd say well done, but I still don't know what half the stuff i just saw is

Thanks though, this is definitely going to be one of the more fun projects I have done... and most expensive... by far

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galderdi

· #4 · May 5, 2017

Hey WolfTronix,

Can I get some more details about your build there?

What is the ratio between those "sprockets"?
What is the width of the belt?
What power do you push out of each motor?
What sort of weight are these pushing?

Do you get any slipping or stretching of the belts?

I am interested because I am considering something similar but in a much smaller scale.

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WolfTronix

· #5 · May 5, 2017

galderdi said:
Hey WolfTronix,

Can I get some more details about your build there?

What is the ratio between those "sprockets"?
What is the width of the belt?
What power do you push out of each motor?
What sort of weight are these pushing?

Do you get any slipping or stretching of the belts?

I am interested because I am considering something similar but in a much smaller scale.

Info is here:
http://www.wolftronix.com/E10/index.html

I think the large sprocket is 100 tooth, and I the smaller ones are 32 tooth.
You might be able to count the teeth in the pics.

Belt is 12mm wide.

42kW max per motor.

4000 pound S-10 truck.

The belts are very tight with little stretch.
I have broken 2 belts, in about 10 years.

I just shut down the broken side and drive home on the other motor.

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brian_

· #6 · May 6, 2017 (Edited)

LunaTech said:
There's only one other thread, but I decided to make this the main thread before things got too out of hand. Here's the old one for reference. http://www.diyelectriccar.com/forum...ible-corvette-stingray-conversion-183714.html

That thread has a comment about Tesla using "recycled" laptop battery cells. They're a type of cell (including size and shape) commonly used in laptop packs, but it's hard to imagine that they are discarded bits from computers, or that buyers of such expensive vehicles would tolerate that... although a Tesla expert could say one way or the other.

LunaTech said:
-The C3 Corvette has a curb weight of 3500 pounds, much to heavy for my range and weight goals. But determined to use it, I'm trying to use me and my dads engineering backgrounds to determine the best possible way to reduce some of the weight.

Other than the obvious deletion of the engine and related components, it will not be cheap or easy to reduce weight. There's a reason it's not light - the bits are all needed... and this is already a composite-bodied vehicle.

I would plan on the converted result being heavier than 3500 pounds.

LunaTech said:
-Budget: My budget of $1500 for the donor makes it difficult to find a c3 corvette in good shape. In GOOD shape. But that doesn't mean I can't find one with a rotten frame. Tying into the first point, I'm reconstructing the ladder frame with carbon fiber, or magnesium tubes (round or square). This will be sturdier and lighter. The frame itself doesn't weigh much I'm aware, but any reduction is more range.

The cost-benefit ratio and technical complexity of merging carbon fibre composites with rusty 1970's GM steel are mind-boggling. It seems very likely that a new frame - built to accommodate the electric drive components rather than an engine and fuel tank - would be more effective and a better value. Available ready-made replacement frames for the C3 (usually set up to use newer suspension) are built of ordinary steel tubing (e.g. 2"x4"x0.120" box) and are both stronger and lighter than the original.

The C2 has steel components embedded in the fiberglass. Although this might sound like a way to protect them from rust, they do rust and are expensive to fix. If the C3 has similar construction, watch for that.

LunaTech said:
-Battery Packaging: This has more to do with frame design and weight. My original box idea might not be very good if I'm going for weight reduction on the structure, especially using expensive material like carbon fiber. Will need to run more thorough calculations.

This is also related to the distribution of mass. Some well-constructed EV conversions have a pack extending disturbingly far forward, which must have a substantial and negative effect on handling. Why build a Corvette and have it handle like a Caprice?

LunaTech said:
-I can't decide on my EV components, until I have a grip on the rest of the information.

Now that makes sense!

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brian_

· #7 · May 6, 2017 (Edited)

The C3 (and C2) use the final drive unit (differential) and halfshafts as parts of the suspension; the C4 rear suspension is different, but still uses the drive components as suspension. That means that either:

you work with the stock final drive, or
you use the differential and halfshafts from some donor vehicle and need to build an entirely new rear suspension (or adapt something... C5/C6 are popular).

There are commercially available solutions which convert to a modern suspension design which doesn't put suspension loads into the final drive... but to use any of those you would need at least ten times more budget.

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LunaTech

Discussion Starter · #8 · May 14, 2017

brian_ said:
That thread has a comment about Tesla using "recycled" laptop battery cells. They're a type of cell (including size and shape) commonly used in laptop packs, but it's hard to imagine that they are discarded bits from computers, or that buyers of such expensive vehicles would tolerate that... although a Tesla expert could say one way or the other.

You are correct

What I meant to say was more along the lines of "The type of cells tesla batteries use, is the same type of cell used in Laptop batteries"

Other than the obvious deletion of the engine and related components, it will not be cheap or easy to reduce weight. There's a reason it's not light - the bits are all needed... and this is already a composite-bodied vehicle.

I would plan on the converted result being heavier than 3500 pounds.

I have seen weight reductions of up too 500 pounds it the corvette forums, without a dramatic rebuild of the frame, so I'm cautiously optimistic right now

my goals around 3000 lbs, but im more than prepared too not get anywhere near that

The cost-benefit ratio and technical complexity of merging carbon fibre composites with rusty 1970's GM steel are mind-boggling. It seems very likely that a new frame - built to accommodate the electric drive components rather than an engine and fuel tank - would be more effective and a better value. Available ready-made replacement frames for the C3 (usually set up to use newer suspension) are built of ordinary steel tubing (e.g. 2"x4"x0.120" box) and are both stronger and lighter than the original.

Agreed, I'm thinking of reconstructing it into a tesla skateboard frame, but I'm worried about reaching the batteries.
What I may do instead is build it out of aluminum, and add cross sections too house the motor and transmission. My ultimate goal is too keep as much weight near the middle and trunk as possible, so im still playing with the idea of adding a spine to the car to house the batteries.

The C3 (and C2) use the final drive unit (differential) and halfshafts as parts of the suspension; the C4 rear suspension is different, but still uses the drive components as suspension.

Thanks, I didnt realize that... Would this effect swapping the brakes at all (are any of the suspension connected there?). I was planning on swapping in c6 brakes from a salvage car I found...

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brian_

· #9 · May 14, 2017

LunaTech said:
I have seen weight reductions of up too 500 pounds it the corvette forums, without a dramatic rebuild of the frame, so I'm cautiously optimistic right now my goals around 3000 lbs, but im more than prepared too not get anywhere near that.

I would be interested to hear how those weight reductions are accomplished, but I wouldn't be surprised if some of that comes from deleting emission control equipment, such as the catalytic converter. Tubular headers might replace cast iron exhaust manifolds. You're removing that stuff anyway in a gas engine to EV conversion, and that's part of what you need to do to make up for the battery mass. Another possibility is removal of bumper structures, and I don't know if you want to do that.

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brian_

· #10 · May 14, 2017

LunaTech said:
Agreed, I'm thinking of reconstructing it into a tesla skateboard frame, but I'm worried about reaching the batteries.

It's not just reaching them. Even Tesla's little 18650 cells are 65 mm tall, so by the time they are packaged (in the obvious way, as Tesla does, standing vertically) they're a significant thickness. Do you hang that much under a car which already has little ground clearance, and bash the pack into speed bumps and rocks? Do you raise the car that much, destroying the appearance and ruining the suspension geometry in the process? Do you put the pack on the floor inside the stock body shell and leave the seats right on the floor with the occupants heels at the same level as their butts, like sitting very uncomfortably on a floor? There's a reason that only Tesla uses this "full floor" design, and everyone else only extends the pack under seating or down a central tunnel.

LunaTech said:
What I may do instead is build it out of aluminum, and add cross sections too house the motor and transmission. My ultimate goal is too keep as much weight near the middle and trunk as possible, so im still playing with the idea of adding a spine to the car to house the batteries.

Starting from scratch on the frame is practical if you have the fabrication abilities, and makes some sense to me given that the drivetrain is entirely different. Aluminum makes life much more difficult than steel, for most fabricators.

If a central battery tunnel is used, the motor must be in the back (presumably without the original transmission), and the central floor of the body must be completely reconstructed. That makes sense to me, but keep in mind that while the car has a large transmission hump, the seats are not very far apart so there isn't much width available for a tunnel rearward of the transmission area. I've only driven a C3 very briefly, but as a passenger the car strikes me as a large pile of drivetrain and tires wrapped around two people, with space for little else.

Modern cars usually have the fuel tank under the rear seat (or behind the seats in a two-seater), but the C3 has the tank behind the rear axle, and even behind the "trunk" space... maybe not where you want batteries, but perhaps it can work. Even worse, it is on top of the frame rather than down between the frame rails, to fit the spare tire. I would consider omitting the spare and placing a pack lower. A more radical option is to flip the final drive around (there are mechanical consequences to this), put the motor on the back, and fill the width of the car ahead of the axle line with battery.

Perhaps a rear pack replacing the fuel tank and spare, plus a front pack replacing the engine, is enough without a central tunnel.

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brian_

· #11 · May 14, 2017

LunaTech said:
Would this effect swapping the brakes at all (are any of the suspension connected there?). I was planning on swapping in c6 brakes from a salvage car I found...

The disks bolt to the hubs, regardless of how the suspension is located; the calipers bolt to the hub carriers, and either way you have hub carriers. There are lots of details of design that matter to whether the bits are interchangeable, but the type of suspension links is not a relevant detail. That doesn't mean these brakes are compatible, only that any issues are not due to the different suspension design.

Are the C6 brake components lighter? In general brake disks don't get lighter with the evolution of a model, because the material stays the same and they get larger for better performance. It's unlikely that a low-budget EV conversion will be driven harder than the original so greater brake capacity is unlikely to be required. If you have regenerative braking, you need even less ability of the brakes to absorb heat. The C6 calipers might be lighter or larger, so I assume that's where some advantage is desired; it looks like they would only be lighter.

Both the C3 and C6 use the hat section of the rear disk as the drum of the parking brake (a design which I have in my Toyota van, and despise, but that's irrelevant here

). They're compatible in that sense, but I have no idea if they exactly match in dimensions, allowing the disks to interchange. Both rear calipers are mounted by axial bolts, but they are quite different calipers (it looks like the C3 uses a fixed-body 4-piston design, while the C6 is a sliding single-piston design), and I wouldn't assume without confirmation that one caliper fits the brackets intended for the other.

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LunaTech

Discussion Starter · #12 · May 16, 2017

brian_ said:
It's not just reaching them. Even Tesla's little 18650 cells are 65 mm tall, so by the time they are packaged (in the obvious way, as Tesla does, standing vertically) they're a significant thickness. Do you hang that much under a car which already has little ground clearance, and bash the pack into speed bumps and rocks? Do you raise the car that much, destroying the appearance and ruining the suspension geometry in the process? Do you put the pack on the floor inside the stock body shell and leave the seats right on the floor with the occupants heels at the same level as their butts, like sitting very uncomfortably on a floor? There's a reason that only Tesla uses this "full floor" design, and everyone else only extends the pack under seating or down a central tunnel.

Starting from scratch on the frame is practical if you have the fabrication abilities, and makes some sense to me given that the drivetrain is entirely different. Aluminum makes life much more difficult than steel, for most fabricators.

If a central battery tunnel is used, the motor must be in the back (presumably without the original transmission), and the central floor of the body must be completely reconstructed. That makes sense to me, but keep in mind that while the car has a large transmission hump, the seats are not very far apart so there isn't much width available for a tunnel rearward of the transmission area. I've only driven a C3 very briefly, but as a passenger the car strikes me as a large pile of drivetrain and tires wrapped around two people, with space for little else.

Modern cars usually have the fuel tank under the rear seat (or behind the seats in a two-seater), but the C3 has the tank behind the rear axle, and even behind the "trunk" space... maybe not where you want batteries, but perhaps it can work. Even worse, it is on top of the frame rather than down between the frame rails, to fit the spare tire. I would consider omitting the spare and placing a pack lower. A more radical option is to flip the final drive around (there are mechanical consequences to this), put the motor on the back, and fill the width of the car ahead of the axle line with battery.

Perhaps a rear pack replacing the fuel tank and spare, plus a front pack replacing the engine, is enough without a central tunnel.

Hmmm... All very good points... While I can't ascertain anything for certain without an actual car, I have been running math based on dimensions I could find online, and I believe that the central tunnel idea is doable, if I can find 16 inch replacement seats, or can shorten the stock seats. I'll post my rough math and drawings as soon as I get home (Its kinda hard to read but its rough

)

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joekitch

· #13 · Jun 3, 2019 (Edited)

from the lack of replies for two years, i'm guessing this fizzled out.
cross linking this back to a post on the corvette forums...

https://www.corvetteforum.com/forum...-here-but-electric-hot-rod-c3-feasible-2.html

but yeah the stock weight of the c3 is concerning, even considering the SBC 350 engine alone is 500 lbs, you can't replace -that- many batteries with 500lbs, and the motor's going to be 200.
i'd be ok with the weight going up to 4000lbs but that's pretty much my limit, any more would really start to bog the car's handling characteristics.
thankfully the watt hours per mile calculations get easier since the model 3 weighs a similar amount and it's watt hour per mile consumption is like 260-300, meaning my conversion (at 40kw of batteries) should get like 130-150 miles of range...although the model 3 is is much slipperier (0.24 cd instead of the c3's awful 0.44), so highway range won't be as good
gotta make sacrifices for those looks

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