Some thoughts on redesigning the Karmann Ghia

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reikiman
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Basically we've identified that the current motor & controller isn't quite up to the task of driving this car. One critical weakness is cooling the controller, and the other is that one of the batteries has a weak cell. So long as I go easy on it the car seems to handle my daily commute. But I really want this car to do much more. I have plenty of vehicles that can handle short and medium distance travel, this car needs to handle longer distance travel and reduce the use of my gas car to once a month or less.

Starting with a couple pictures of the engine compartment's current layout.

DSCN1890-web.jpg

DSCN1891-web.jpg

The new motor (pictured below) has a 9+ inch diameter or a bit less than 5 inch radius. The existing motor is a 6.7" diameter. By my measurement the distance from the center of the existing racks is approx 5 inches, the diameter of the motor is slightly less than 5 inches.

Hence the new motor will be a tight squeeze. Hence it would be good if the battery racks could move a couple inches. Fortunately it seems the battery racks aren't bolted to the frame, instead they're bolted to the motor mount as well as to a bar that's also a second motor mount underneath the motor. That is the motor has two mounts - one serves as an adapter plate attaching to the transmission, and the other is this bar underneath the motor. The bar doesn't appear to be attached to anything other than the motor, however. It means that most of the weight of the motor and batteries is resting on the motor mount.

The battery trays look like they should be bolted to the car - but they aren't. Instead there's a bit of foam stuffed under them between the tray and the car. That seams odd but on the other hand the tray-like area in the motor compartment isn't really sturdy structural, it's just there.

The other thing to notice is the controller. I'm going to be replacing the controller and the new controller doesn't look like it will fit very well. The existing controller is 7" long, 4" wide, 3" deep, or thereabouts, while the replacement controller is 12" long, 7" wide, and 4" deep.

DSCN1895-web.jpg

This is a Curtis 1231C - it weighs quite a bit - has better built-in heatsinking than the Alltrax - but is not programmable. The heatsinking even has this channel that you could run a water pipe through for cooling, maybe.

The thing is it's a lot bigger - bigger enough to not fit where the existing controller sits.

What I'm thinking is to build a tray for the controller to sit on, and have that tray bolt to the frame, and to make sure the tray also acts as a heat sink.

Either that or I'll be getting a Kelly 144v controller because those are programmable. I gotta be able to geek out on the controller, right?

DSCN1897-web.jpg

DSCN1899-web.jpg

This is the new motor. Netgain Impulse9. It already has a VW clutch and adapter plate. The people at Green Rides were working on mounting this motor & controller onto a kit-car which has a VW transmission. Therefore I know that this motor will bolt directly to the transmission on the Karmann Ghia.

I've had a recommendation for a local car shop to work with - It's a shop that Richard Hatfield knows and claims is interested in or experienced with EV's. I'm planning to have an experienced shop do the motor swap because - heck -I know nothing about transmissions and motor swaps, it's better to let an expert handle it.

This motor will work at 72 volts so I intend to do the motor swap now and continue using the existing controller. It will stay that way until the new battery pack arrives at which time I'll swap the battery pack and controller in one go. The new motor is more than enough to handle this job so it should fix the bit about the motor overheating.

I really should do something about heatsinking the existing controller, then, as a stopgap measure .. it's gonna be approx 2-3 months before the new pack arrives from China and is ready to go. Hurm.

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- David Herron, Green Transportation Examiner, Green Transportation Info, The Long Tail Pipe, Electric Race News, davidherron.com, 7gen.com, What is Reiki
- Charger bike (rebuilt), Electrified Electra Townie, 1971 Karmann Ghia

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Spaceangel
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Re: Some thoughts on redesigning the Karmann Ghia

When you pull the old motor out. Can you do an autopsy on the motor to a small extent. I have burnt commutator on my Prestolite on my truck from I presume the Motor Vehicle inspection station trying to test parking brake. So one commutator is blackened and I am sure causes me to draw max amperes more than I used to draw. I am sure any controller is going to run better "HEAT SINKED". So inspect for a burnt section ?

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antiscab
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Re: Some thoughts on redesigning the Karmann Ghia

reikiman wrote:

This is a Curtis 1231C - it weighs quite a bit - has better built-in heatsinking than the Alltrax - but is not programmable. The heatsinking even has this channel that you could run a water pipe through for cooling, maybe.

The thing is it's a lot bigger - bigger enough to not fit where the existing controller sits.

What I'm thinking is to build a tray for the controller to sit on, and have that tray bolt to the frame, and to make sure the tray also acts as a heat sink.

Either that or I'll be getting a Kelly 144v controller because those are programmable. I gotta be able to geek out on the controller, right?

I would suggest avoiding the 1231C, unless you get a *really* good deal on one.
they aren't very user friendly.

if going kelly, get at least 800A.
all controllers are rated in max motorside amps (which is related to how much switching silicon the controller has)
your problem is continuous motor amps, which is related to how much heatsinking the controller has.

the kelly has less heatsinking per unit switching silicon than the curtis.
so the result is, to get the same continuous current, you end up with a controller that has lots more peak current limit.

you can just back the current off in software though.
http://www.kellycontroller.com/product_info.php?cPath=25_38&products_id=312

I'm pretty sure the impulse 9 has more back emf than your present motor.
that means whatever controller you use won't have to work as hard as your controller does now.

so put the new motor in first before buying a new controller
ideally buy the new controller when you have a battery big enough to need it :)

Matt

__________________

Daily Ride:
2007 Vectrix, modified with 42 x Thundersky 60Ah
Vectrix 60Ah Lithium Tyres Fuel Registration Insurance cycle analyst replacement TC Charger
conversion
Spent so far: $5800 + $7000 + $1720 + $960 + $320 + $720 + $140 + $600
Cost to do it again: $2500 + $5600 + $1720 + $960 + $320 + $720 + $140 + $600
Cost for a Petrol bike:$6000 + + $1440 + $6000 + $800 + $1400 + $3200 servicing
Total spent: $17260
Total to do again: $12560
Total to have used a petrol bike: $18840
Total distance travelled so far: 79'120km

reikiman
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Points: 8456
Re: Some thoughts on redesigning the Karmann Ghia

There are three screws on the side of the Curtis that I believe are meant for adjustments. I'd rather geek out with the software though. I'm sure than an unused Curtis controller will go for a good price on eBay. The controller and motor came as a package deal, see.

I'm pretty sure the impulse 9 has more back emf than your present motor.
that means whatever controller you use won't have to work as hard as your controller does now.

so put the new motor in first before buying a new controller
ideally buy the new controller when you have a battery big enough to need it :)

Yeah that's what I'm thinking too. The new battery pack will be here in approx 2 months, well that's when the cells arrive from China, dunno how much time is needed to assemble it into a working pack.

__________________

- David Herron, Green Transportation Examiner, Green Transportation Info, The Long Tail Pipe, Electric Race News, davidherron.com, 7gen.com, What is Reiki
- Charger bike (rebuilt), Electrified Electra Townie, 1971 Karmann Ghia

John Kelly
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Re: Some thoughts on redesigning the Karmann Ghia

I am no help with the electronics, but you might think about cutting the engine bay sheet metal and making a rack for the batteries that is lower down...basically where most of the weight of the original engine was. It will help the handling and stability of your Ghia.

I thought about building an electric Ghia, but have given up customizing Ghias after many years. I would have cut the center tunnel of the floor pan out for more battery space, and added a roll cage for rigidity and crash worthiness.

John www.ghiaspecialties.com

reikiman
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Re: Some thoughts on redesigning the Karmann Ghia

John, thank you for your thoughts but there isn't a need to cut out room for more batteries. What I'm planning to do is take out the back seat, build a tray, put the batteries there, and make a platform on top of the batteries for cargo. Basically I think the back seat is worthless and it might as well be for cargo. And that location is nice and central to put weight nearer the center of gravity. That position won't be big enough for batteries, and will put the rest in the front section or else in the engine compartment.

So--- you're thinking that sheet metal can just be cut away without structural significance? It certainly seems that way, and I wonder why VW put that piece of metal there in the first place.

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- David Herron, Green Transportation Examiner, Green Transportation Info, The Long Tail Pipe, Electric Race News, davidherron.com, 7gen.com, What is Reiki
- Charger bike (rebuilt), Electrified Electra Townie, 1971 Karmann Ghia

strawhistle
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Points: 340
Re: Some thoughts on redesigning the Karmann Ghia

If I remember right the Ghia has a uni-body frame ! I wouldn't cut the frame without additional reinforcement. That sure sounds like a SweeT project ! thanks catch ya LaTeR

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antiscab
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Re: Some thoughts on redesigning the Karmann Ghia

reikiman wrote:

There are three screws on the side of the Curtis that I believe are meant for adjustments.

The three screws on the side of the controller (in no particular order, IIRC):
1) adjusts low voltage limit (controller shuts down completely for a moment every time this voltage is reached)
2) adjusts max motor side current limit
3) adjusts PWM % ramp rate (so if you adjust it enough so the car doesn't "lurch" on take off, change in throttle position is glacial when at speed).

the lurch on take off is because the throttle directly controls motor voltage, with a fixed motor current limit.

sometimes a table shows this best:

throttle position: rpm motor voltage motor amps motor torque/acceleration
0% n/a 0 0 0
1% 0 1% 20% 20%
5% 0 5% 100% 100%
100% 0 5% 100% 100%
20% 20% 20% 10% 10%
25% 20% 25% 50% 50%

so when the motor is spinning below the max power point (usually around 3000rpm) the difference between part throttle and full throttle is *very* small.

all digital controllers (including your altrax) has the throttle proportionally setting motor current limit before transitioning to motor voltage limit.
so their table looks more like this:
throttle position: rpm motor voltage motor amps motor torque/acceleration
0% n/a 0 0 0
1% 0 0.05% 1% 1%
5% 0 0.25% 5% 5%
100% 0 5% 100% 100%
20% 20% 21% 20% 20%
25% 20% 21.25% 25% 25%

generally you don't find out how much it affects the cars drive ability until you try it out, after installation.
so if you get a cheap one, give it a shot.
but definately don't buy a new one.

Matt

__________________

Daily Ride:
2007 Vectrix, modified with 42 x Thundersky 60Ah
Vectrix 60Ah Lithium Tyres Fuel Registration Insurance cycle analyst replacement TC Charger
conversion
Spent so far: $5800 + $7000 + $1720 + $960 + $320 + $720 + $140 + $600
Cost to do it again: $2500 + $5600 + $1720 + $960 + $320 + $720 + $140 + $600
Cost for a Petrol bike:$6000 + + $1440 + $6000 + $800 + $1400 + $3200 servicing
Total spent: $17260
Total to do again: $12560
Total to have used a petrol bike: $18840
Total distance travelled so far: 79'120km

John Kelly
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Joined: 05/22/2010
Points: 14
Re: Some thoughts on redesigning the Karmann Ghia

The engine compartment sheet metal is not structural. It is there to isolate the cold air (air-cooled engine)coming in the top and the hot air going out the bottom... also keeps hot exhaust from being recycled through the cooling fan.

The center tunnel is structural. I would have made extra bracing for the floor pan if I had gone that route. I look forward to hearing more about your Ghia as you make progress!

John www.ghiaspecialties.com

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