[galderdi]

Hi everyone,
It has been a while since I last posted. Some of you may remember my previous projects which were budget minded autocross centred EVs. Since then our governing body has closed the gate on EVs and there is no glimmer of hope for the foreseeable future for electric vehicles under them. So my last chassis is going into retirement. I am commencing a new project which will enable me to continue my EV journey on public streets. It will be a scratch built Porsche 55 Spyder themed road car.
I have placed a deposit on a locally built chassis which normally has a fibreglass body but will be near perfect for my objective.
I will be building a buck for the 55o style body and constructing an aluminium body.
I know there are kits available. But I am not really doing this to gain a car. I am doing this for the satisfaction that can only be obtained by doing something special.
It will not be a true replica as the interior and some other details will be different. One notable difference will be the addition of head rests which are mandatory for all new road cars here. I will be building streamlined pods behind each occupant. The headrest will be built into the front of each pod. Inside each pod will be a roll bar.
I will be aiming to have about 20kwh of capacity.
The voltage is yet to be nailed down but it will be somewhere between 175 and 350 depending on the final choice of controller. I may well start with my existing ZEVA controller and upgrade later.
I had ambitions of having a front and rear motor providing all wheel drive. But I need to have an engineer certification for road registration. It has gone through a few iterations and I haven't fully landed on the final decisions but AWD is off the table. I can do pretty much anything but I face a choice between something different which would incur at least $5000 extra cost for all the tests. So I am having to compromise in order to align with a previously tested chassis and avoid all the extra costs. The approved design is 550Kg (1200lbs) so keeping reasonable battery capacity and power is tricky. The chassis design calls for a mid mounted drive train using a FWD gearbox. I know a load of people will scoff at the idea of running a gearbox but again changing this part of the design would trigger a chain reaction that would result in a heap of delays and extra costs. Running through the gearbox means I only need an adaptor and mounts and I'm good to go.
The motor I am running is an Advanced DC 8 inch. In the previous car the motor performed excellently from 0 - 80kph (45mph) but was lacklustre from there to 100kph (70mph). But that was running at 172v so the back EMF was catching me in the higher revs. So I am intending to swap to a controller that can handle high volts to combat the back EMF and give better top end performance. But even if I run with the ZEVA controller for a while it will perform just like my last car which was awesome up to 80kph.
This will be a long project but I plan to provide regular updates along the way.
I have placed a deposit on the chassis. So I anticipate picking it up in March (maybe). I have already designed the slices for the buck and I can get started on parts of the construction. I have already created a scale mockup of the buck in paper just to check for any concerns. As a result I am adjusting my approach slightly. I have an english wheel and bead roller. I will need to purchase a few other tools and I need to do a TIG course (booked in for March). I am practicing with the various techniques and in particular I am performing a full size proof of concept on the door area to understand how to achieve a good gap.

I will upload some photos for reference shortly

 

[Duncan]

That looks truly awesome!
I would not dare to try to make an aluminium body!

Have you thought about using something like a Nissan leaf power unit ?
You get the engine and gearbox together as a single unit - as long as it is low enough for the body

 

[brian_]

This sounds like a great project, and I'm looking forward to following it.

Have you thought about using something like a Nissan leaf power unit ?
You get the engine and gearbox together as a single unit - as long as it is low enough for the body

Yes, and we had this discussion during the design of galderi's previous project; however, I think the explanation for this choice has already been given:

​

The chassis design calls for a mid mounted drive train using a FWD gearbox. I know a load of people will scoff at the idea of running a gearbox but again changing this part of the design would trigger a chain reaction that would result in a heap of delays and extra costs. Running through the gearbox means I only need an adaptor and mounts and I'm good to go.​

​

​

The motor I am running is an Advanced DC 8 inch. In the previous car the motor performed excellently from 0 - 80kph (45mph) but was lacklustre from there to 100kph (70mph). But that was running at 172v so the back EMF was catching me in the higher revs. So I am intending to swap to a controller that can handle high volts to combat the back EMF and give better top end performance. But even if I run with the ZEVA controller for a while it will perform just like my last car which was awesome up to 80kph.

That makes sense. Or you could just shift, since you're stuck with the transmission anyway.

 

[brian_]

I have placed a deposit on a locally built chassis which normally has a fibreglass body but will be near perfect for my objective.
I will be building a buck for the 55o style body and constructing an aluminium body.
I know there are kits available. But I am not really doing this to gain a car. I am doing this for the satisfaction that can only be obtained by doing something special.
It will not be a true replica as the interior and some other details will be different. One notable difference will be the addition of head rests which are mandatory for all new road cars here. I will be building streamlined pods behind each occupant. The headrest will be built into the front of each pod. Inside each pod will be a roll bar.

It's also mechanically very different from the 550, in both suspension and in engine configuration, so it will be near-replica of the body on a different chassis of the same general layout. I like the fairing (pod) plan.

Searching for the chassis, I learned that Graham McRae built some highly regarded replicas a couple decades ago, but this is not one of those or a continuation of them - they were much closer to the original mechanical design. It does look like a very nice design, with a much better suspension than the original.

 

[galderdi]

That looks truly awesome!
I would not dare to try to make an aluminium body!

Have you thought about using something like a Nissan leaf power unit ?
You get the engine and gearbox together as a single unit - as long as it is low enough for the body

Thanks Duncan, Lets wait and see the quality of the outcome. I am new to body work. But doing the course did give me some confidence. It looks like a load of trial and error and rework. There are some areas (example around the wheel arches) where I am clueless at the moment. But I will try a couple of techniques and see how it goes. Funny enough after examining many photos I can see the replicas do not have the little flare around the wheel arch which would solve the problem.

I have and still am considering all the options. Leaf, Tesla, Bigger DC, AC etc etc. But I already have two of these motors and they are simple. I have enough learning coming with the body. I don't want to distract myself with trying to alter the driveshafts, hubs and the snow ball effect all that could potentially have on other components. But certainly down the track something like that could be the basis of phase 2 (or Phase 3 assuming it is AC )

 

[galderdi]

This sounds like a great project, and I'm looking forward to following it.


Yes, and we had this discussion during the design of galderi's previous project; however, I think the explanation for this choice has already been given:

​

​

That makes sense. Or you could just shift, since you're stuck with the transmission anyway.

It's also mechanically very different from the 550, in both suspension and in engine configuration, so it will be near-replica of the body on a different chassis of the same general layout. I like the fairing (pod) plan.

Searching for the chassis, I learned that Graham McRae built some highly regarded replicas a couple decades ago, but this is not one of those or a continuation of them - they were much closer to the original mechanical design. It does look like a very nice design, with a much better suspension than the original.

Hey Brian, the motor choice is about convenience and cost. I am already up against a load of challenges, I don't want to add more to the mix.

Shifting up doesn't help significantly. The gearing doesn't drop the revs low enough to put the motor back in it's ideal rev range. So then there isn't enough power to over come the mechanical disadvantage the new gear just introduced. I am fairly sure what I need is higher volts to extend the power into the second half of the rev range.

The Chassis is known as the GTZ here in Australia. It was produced under agreement with the original designer in the UK. There is a thread here (Hopefully you can see it):

Sign In - OzClubbies

www.ozclubbies.com.au

 

[Duncan]

I'm building a Marlin Roadster
I sort of fell into this build
Its simply too small to fit enough batteries to make it a second electric car
So its getting an old Ford Crossflow

If I had not started this my "plan" was to make a Jaguar "C" Type - or XK120 replica
But I was going to make the body from fiberglass

The chassis I was going to make using fiberglass honeycomb sandwich panels

 

[galderdi]

I'm building a Marlin Roadster
I sort of fell into this build
Its simply too small to fit enough batteries to make it a second electric car
So its getting an old Ford Crossflow

If I had not started this my "plan" was to make a Jaguar "C" Type - or XK120 replica
But I was going to make the body from fiberglass

The chassis I was going to make using fiberglass honeycomb sandwich panels

Interesting project. Not enough space for batteries!!! It looks like a semi trailer compared to a 550. But looks can be deceiving.
I have done fibreglass (not suggesting I'm an expert). I recently completed a metal shaping course (english wheel etc). My simple assessment is....
If you have access to suitable moulds or if you intend making more than 1 copy then fibreglass is awesome.
But if you don't have moulds and only intend a single copy then metal is the way to go. The other caveat is the complexity of the shape. Older cars have curves but they tend to flow and can be replicated through basic metal shaping techniques. Modern cars have curves and angles that cross over each other and intersect and compete and would be a nightmare to replicate. I don't blame modern panel beaters for just buying new panels.
I'm not talking you out of fibreglass. I think it is horses for courses.
Here is a pic of the panel I made in the metal shaping course which was only 2 days and much of that time was standing waiting for machines that were shared amongst the 12 students.

What will the new car be used for? Road registered? That chassis would be a nightmare to get certified here. Keep me informed of the progress.

 

[Duncan]

Looks can be deceiving - the Marlin is an old kit car - this one is Morris Marina Based so its about a foot shorter and narrower than my "device"
The wings and running boards design means that you cannot use that space - putting the motor - I had a nice 9 inch unit for it - in the gearbox space leaves the engine bay for batteries
Using that and the duel tank location I could have squeezed as many batteries as I have in my "Device" - 14 kwh
But I already have a short range car
I find I'm either driving less than 50 km - the Device will work - OR over 150 km
So I need about three times as much in the way of batteries

I haven't had any kickback at all using my Device for autocross and such like - maybe I would hit problems if I started to win!

 

[galderdi]

Looks can be deceiving - the Marlin is an old kit car - this one is Morris Marina Based so its about a foot shorter and narrower than my "device"
The wings and running boards design means that you cannot use that space - putting the motor - I had a nice 9 inch unit for it - in the gearbox space leaves the engine bay for batteries
Using that and the duel tank location I could have squeezed as many batteries as I have in my "Device" - 14 kwh
But I already have a short range car
I find I'm either driving less than 50 km - the Device will work - OR over 150 km
So I need about three times as much in the way of batteries

I haven't had any kickback at all using my Device for autocross and such like - maybe I would hit problems if I started to win!

What if you made a small trailer in a suitable style containing another small set of batteries (like 100kwh) as a range extender. Then just suspend a cable from the trailer back to the car. I really should take my own advice. That might work for the 550

 

[Duncan]

What if you made a small trailer in a suitable style containing another small set of batteries (like 100kwh) as a range extender. Then just suspend a cable from the trailer back to the car. I really should take my own advice. That might work for the 550

I thought about that - the trailer could earn its keep as storage for my solar panels when it was not being used
Now I'm trying to remember why I did not go that route!!

 

[brian_]

The Chassis is known as the GTZ here in Australia. It was produced under agreement with the original designer in the UK. There is a thread here (Hopefully you can see it):

Sign In - OzClubbies

www.ozclubbies.com.au

That forum requires a login, so I can't see the thread, but I found the car...

• Listing by AutoYas: Suncoast Sports Cars Australia & NZ
• Facebook: Suncoast Sports Cars Australia & NZ Strangely, they posted this: "10th GTZ NOW SOLD. Thanks for the support to all the builders of GTZs. Its been a wild ride. No longer taking orders. Check in for further updates on existing builds."
• Brochure linked to Facebook page: GTZ Brochure.pdf (some specs, not a lot of good images)
• Entry in Bolwell Sports Cars blog: GTZ Built to Drive (more photos)
• Custom Fiber Creations - Services: Suncoast Sports Car (the manufacturer of the fiberglass body, but that won't be used in this project)
• Shannons Club: 2019 Suncoast Sports Cars GTZ (car belonging to an RX-7 club member; mentions "Kit is designed to use the mechanical and electrical components from a 2005-2012 1.6L Hyundai Getz")

I don't know which British kit this is based on - 550 kits typically use VW/Porsche suspension, and even the that I noticed with double wishbones (from Holmes) uses a boxer engine.

 

[brian_]

Shifting up doesn't help significantly. The gearing doesn't drop the revs low enough to put the motor back in it's ideal rev range. So then there isn't enough power to over come the mechanical disadvantage the new gear just introduced. I am fairly sure what I need is higher volts to extend the power into the second half of the rev range.

Big steps between gears can be a problem, but will that be a problem with the Hyundai 5-speed that this kit uses? All you need is to maximize motor power output; it doesn't matter what the speed and torque combination is, because that's what the transmission changes for you.

 

[brian_]

What if you made a small trailer in a suitable style containing another small set of batteries (like 100kwh) as a range extender. Then just suspend a cable from the trailer back to the car. I really should take my own advice. That might work for the 550

With any luck the combination of electric power and towing a trailer won't drive Porsche enthusiasts to kill you in their rage.

But it could work. Presumably one would equip the trailer with its own BMS, and the car with a switch to choose between onboard and trailer batteries, routing the BMS information for the chosen battery to the dashboard or displaying both.

I thought about that - the trailer could earn its keep as storage for my solar panels when it was not being used
Now I'm trying to remember why I did not go that route!!

A major issue with my Spitfire conversion plan was inadequate range, and I can see doing this: transit to events using the trailer, saving the onboard battery for the event. For me, the problem would be that I would have built a really fun-to-drive car, then saddled it with a trailer when on the road. I don't mind towing a trailer, but it's not what I want attached to a sports car.

Also, a trailer is a real drag... literally. Towing one costs more in energy per distance travelled than just carrying the battery weight in the car.

 

[brian_]

The design of this conversion will be a challenge in the usual area: battery packaging.

In general, mid-engine cars with longitudinal engines have the advantage of a substantial space between the seats and the rear axle for battery. Even the Porsche 914 - which had a short boxer 4 like the 550 - has a generous engine compartment (perhaps because it was designed to fit the Porsche 6-cylinder as well). Unfortunately, the GTZ uses a transverse engine so it is not clear how long (front-back) that space is, and the conversion is to use the same transaxle; with the transaxle and electric motor in place, there might not be much room left for battery. I realize that it isn't feasible in the local regulatory environment, but a drive unit that places the motor on-axis (such as the Chevrolet Spark or Bolt) would be nice to leave battery space while not mounting the motor hanging out the back.

A rear drive and originally mid-engine car doesn't want a lot of battery mass up front, but it is reasonable to replace the fuel tank (which is usually up there, including in the 550 and any traditional VW/Porsche) with a small battery pack. Unfortunately, much of the space is taken by an inboard suspension. Inboard suspension is usually used to get the springs and dampers out of the aero tunnel, but of course this car doesn't have those. Often in kits inboard suspension is just used to look cool - not so much here, as it is not exposed. In current racing cars, inboard suspensions bring the components together making interesting designs such as heave springs and inerters possible, but there's none of that here. I assume that GTZ uses front uprights which are designed to carry the load through the upper ball joint (because they are adapted from the Hyundai - it uses the same hub-bearing units front and rear), and resorts to rocker arms to keep the springs and dampers low, rather than sticking right out the top as they would need to if mounted directly to the upper arms near the uprights. Anyway, with major suspension modification unlikely, and the foot box extending to the suspension area, there appears to be no room to stuff battery modules up front.

Centre consoles or big sill boxes (depending on how the seats are placed in the width) are sometimes potential locations, but this narrow car doesn't offer either.

 

[brian_]

After a substantial time looking at this car it finally dawned on me that although the plan for the body is to emulate the Porsche 550, the chassis and kit body are not based on a Porsche at all, but instead copy the body of some low-production British car of the past (similar to the Ginetta G12). I was just interested in the chassis and not paying much attention to the body. I hope the 550 body proportions work with the chassis, but I'm sure that has already been considered.

A genuine Porsche 550 has a 2100 mm wheelbase; the GTZ is significantly longer at 2260 mm so the body will need to stretch to accommodate that. I don't know how the stretch will need to split between ahead of and behind the driver position to place the cockpit correctly, or how much if any will be in the cockpit opening. The width is a nice match, and the cockpit sides appear to be taller on the 550 (which is a lot easier to accommodate than the other way around).

The GTZ has a wide single rollbar, which would have to go to be replaced by twin rollbars in pods. The GTZ bar is just tacked on top anyway, not extending to the floor and not braced rearward at all (it wouldn't pass any reasonable racing tech inspection); the twin bars can be better than the original if care is taken to feed the loads into appropriate frame points.

 

[galderdi]

Thanks for all the effort and interest there Brian. You are on the money with your responses.
Yes Glen's vision was only to build 10 of the GTZ. While he has not totally closed the door to more it is not on his immediate horizon. He has taken this on as a life journey and is keep to find a new journey. He is watching the EV side with much interest.
Yes a slight stretch is required through the body to match the GTX wheel base. I am planning for a small portion of the stretch to be just in front of the door, another 1/3 to be in the door. The final 1/3 is interesting and debatable. I have noticed on my scale model and most of the 550 photos I have found it appears the rear wheel is slightly forward of the arch centre. It is possibly a visual illusion but regardless it is an opportunity to move the wheel back slightly to centre it in the arch without altering the body design. But aside from all this I acknowledge the process I am going through is far from precise. The buck I will build won't be perfect, then I will eye ball it and make adjustments (even less perfect). But hopefully my eye balling will still end up with a body that is recognisable as 550ish. If non porsche people look at it and recognise the shape then I am happy. I won't be concerned with purists criticising small deviations. The whole front and back top surfaces of the 550 are higher than the GTZ. It will likely only be a couple of inches but it is still enough to buy me some internal space for batteries. When I inspected what has turned out to be my chassis I realised there is triangulation front and rear in the door area. This will be challenging as the 550 did not have this. So with the door open it will look different from the 550. But the triangulation is on the inner part of the frame so I am confident I can shape the inner part of the door to dovetail with the frame shape while the outer door shape will be closer to the 550 design.
The majority, if not all, the battery will be behind the seats as you suggested. I don't like the idea of side pod batteries. If they do have an issue resulting in extreme heat or fire I don't want that in the only point of egress. The foot well on the driver's side is a no go for battery capacity because the design requires space for pedals. But the passenger side standard design does have some space in front of the foot well. Plus the foot well itself is overkill as it doesn't have pedals. So I plan to bring the passenger footwell back in line with the Driver's pedals. This does buy a little space I could use for a small portion of the batteries. However I am not convinced I will take this option as splitting the battery then introduces the need for heavy conductors running from front to back. I still have some design work before these decisions are finalised. There are other components that can be placed up front without the need for the heavy conductors. But that approach will make it more difficult for me to match the original weight distribution. Like I said I have some work to do here.
The single rear roll bar is being omitted from my chassis in favour of 2 individual hoops as you say. The chassis will still not be supplied with any rear stays but I will add them later. I need to take care with that part of the design otherwise I risk blocking the ability to get the motor, gearbox and batteries in and out of the car.
I know I haven't address all of your points because many of your points were spot on anyway. But if I have missed anything requiring clarification please let me know.

 

[brian_]

The Chassis is known as the GTZ here in Australia. It was produced under agreement with the original designer in the UK. There is a thread here (Hopefully you can see it):

Sign In - OzClubbies

www.ozclubbies.com.au

I decided to register with OzClubbies, which took a couple of days.

Strangely, the original UK manufacturer seems to be some sort of secret, since everyone seems to avoid using their name; the problem is that the Australian builder only bought the rights to the chassis and body design, not any of the names. It is Sylva (the Jeremy Phillips designs); the model with that body would be their J15 or later Vectis, although the chassis design started with the Riot. Each model is tweaked to use the popular donor of the day: the Vectis goes with MGF bits, and Suncoast has set up the GTZ for Hyundai Getz bits.

Front suspensions vary - only some have the rocker arms and inboard damper and springs; the Ford version of the current Riot appears to have the same rear suspension as well. At least some Sylvas appear to use Triumph Spitfire front spindles (hopefully with lower ball joints instead of the trunnion bearings), like many British kits and low-volume sports cars; the GTZ uses modified front uprights from the donor (Getz in this case).

The front upright conversion is unusual in that it requires cutting and drilling (typical practice is bolt-on adapters), and interesting in that is incorporates the steering arm in the adapter to reposition the rack much higher.

One of the goals of kit car design is the "single donor": every needed donor part from one salvaged vehicle. This isn't one of those - you need two sets of front hub-bearing units, and steering column parts from different Hyundai models. For the EV version it would likely make sense to just buy the needed chassis bits and transaxle individually.

Interestingly, the originals appear to typically have dual roll hoops which would fit the 550 body plan better than the wide single hoop used on the GTZ.

 

[brian_]

The single rear roll bar is being omitted from my chassis in favour of 2 individual hoops as you say. The chassis will still not be supplied with any rear stays but I will add them later. I need to take care with that part of the design otherwise I risk blocking the ability to get the motor, gearbox and batteries in and out of the car.

Bolt-in rear stays seem like a reasonable design to me.

 

[galderdi]

Oh I forgot to mention. The Porsche nose is slightly longer than the GTZ and there is no ned for the radiator. So there is a possibility of including some battery up there. But it's not my preference as I'd rather not have it at risk in a front impact.