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Discussion Starter · #1 ·
Hi folks,

During the era a few months back when huge amounts of data vanished from this forum, I decided to do my build thread on my own blog. But things seem to have settled down some and the help and support that this group offers will be huge as I get deeper into the project.

But the blog has already been going, and since I am also involved in a BMW forum and I have various friends, clients and family that are interested to follow along, I decided to just keep the blog and link to it here for each update. The blog is located here in case you are interested:

bmwcse.com




Here's the first post:



My name is Paul Dexter, and I have a problem: I have been a lover of European cars as long as I remember.

Sure, my dad and his ‘50s car club buddies built plenty of American muscle hot rods. But my mom opted to haul us around in various VWs and Volvos.



As I came of age in the ‘80s and ‘90s I began to explore a string of my own European cars. Nothing fancy mind you, I would buy what I could afford, which wasn't much. Always a bit rough, I drove a string of Alfa and Fiat Spiders, Jensen Healey, Triumph, Saab. But German cars were my obsession for their combination of engineering, performance and personality. Plenty of BMWs, Porsche’s VW 16Vs, Audi Quattros, and a few Mercedes passed through my garage. The BMW straight 6 and the Porsche flat 6 engines were so intoxicating for me, they could literally wash away a bad day by joyously going through the gears.
Then Tesla came along.



I was drawn to the refined stealthy, torquey, efficient power. I threw all financial caution to the wind to buy one and it ruined my love for internal combustion engines forever.

Manual shifting is fun sport, but it doesn’t match the gratification of having all the power you could ever dream of at your disposal - at any speed and any time you want it.

But after a few years with the Tesla my soul longed for the one thing I missed from my early cars: Personality. Cars that were drawn by hand, with long hoods and chrome bumpers. Cars that mock wind tunnel tests.
So That Settled It



As Ferdinand Porsche said “I couldn't find the sports car of my dreams, so I built it myself”. Similarly, I decided that what I must do is build my own modern classic for my daily driving enjoyment. Two cars that always topped my list were an early 911 and a BMW 3.0 CS. Both have seen remarkable - perhaps obscene - runs on values in the last ten years. The last thing I wanted to do was destroy the true value of a highly collectible car. Then again I wanted to drive my car, not store it in climate controlled environment and visit it on occasion.

Since I still run the kids to school most days, the BMW coupe made most sense. My wife has always wanted a 2002, so building on its big brother checked even more boxes.

The BMW E9 coupe built by Karman from 1969 to 1975 is one of the most classic and iconic designs of its time. Its pillarless design and shark nose front that went on to define the marque for decades. This Coupe's capable performance and driving experience is responsible for the term “The Ultimate Driving Machine” and firmly footed BMW as a sport-luxury brand.

So if you like, read on, and follow the project. We've got a ways to go...

Cheers,

Paul Dexter
 

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Discussion Starter · #2 ·
This blog is broadly written to speak to car enthusiast, electric car fanatics, friends and family, and that person who got bored on the internet one day and stumbled upon this blog. I will try my best to be too technical, too simple, to colorful and too plain since pleasing everyone is impossible anyway.

Finding the Right Coupe

I searched nationally for a good amount of time for the right car at a fair price. Because I want to convert it to electric, I was hoping to find a roller. Something with it's original motor and transmission missing, so that I could feel a little better that I wasn't the first person to cause harm to the collectable originality of the car. My car would certainly have rust, but I wanted to avoid a rolling rust museum. The overall condition of the car did not need to be high, but finding one as original as possible, and with as much of the trim intact was very desirable.

I can not and will not unpack the mysteries of the collector car market and it's currently obscene values of certain cars. Many cars from the 70s and 80s are getting very hot, so what you could get for just $5k a few years back is suddenly costing $20k. In looking for my coupe I wasn't as concerned with value, but I did want to do the best I could to avoid getting caught up in all the hype.


In the end I came a very interesting 1974 3.0 CS through a very off-the-radar listing (really helping with the aforementioned over-valuation hype). It was close by in San Diego. It is a European market car, imported to the US in 1994. This is interesting for a couple of reasons: First, it was driven for many years by actual Europeans, most likely full-throttle on the Autobahn. Second, it means that it has the lovely small bumpers that by 1974 all US market cars did not. They received park bench units that hung well into the next county. What really pleased me is that she is a sunroof model. Those that know me know that if my cars don't have a sunroof, a convertible or a targa, I will likely find a saw nearby and take it to the roof. (You should have seen my 1978 VW Rabbit Targa- it really happened). Sunroofs were rare for the European market, so that's even more interesting.

It was originally Polaris Metalic (silver) with blue leather. At some point the car was painted white, along with it's factory alloy wheels. White wall tires were fitted to complete the interesting look. The car is very complete, with a fairly tidy interior. The power windows work with a little assistance. The car runs and drives. With no working clutch, the driving experience is even more exciting.

Bringing Her Home


With Trailer in tow I headed in her direction. I hadn't actually been able to see the car in person. I had to buy based on photos, more detailed photos, and answers to my many questions. Then I had to pay for the car, then come pick it up at a third party. Highly aware of the common scams, this was clearly not that. It was just a seller that did not or could not deal with the process of showing the car. Since the car was nearly half the price of others I were looking at and in far better overall condition I did take that chance. When I pulled up I was greeted with a clean California Title, a bill of sale, an original BMW key and a car that looked better than the photos I had been reviewing.

Getting her on the trailer was fun without a clutch or a winch. We tried disconnecting the coil and driving up the trailer ramps with the starter, but that wasn't enough power to make the climb. So I had to drive it up and try to remember to turn off the engine once on the trailer. Things were going swimmingly until the car jerked to a stop with a loud crash! The exhaust (which was attached to the car only at the manifold and the tailpipe) was hanging just a bit too low. We thought it would clear, but just enough of it caught the hard edge of the trailer that it ripped the entire system right at the manifold. We gathered the parts and put them in the truck then gave it another run. This time she sounded like a terrific track runner. I drove it to the top of the trailer so easily that of course I forgot to turn off the motor until I just about drove off the front of the trailer. But I found the key just in time and avoided any more excitement for the day.

In the Shop

Back at the shop we pulled her down and settled her in. We will likely weld the exhaust back to the car so that we can drive her around a bit and have some fun before she's completely disassembled. We also want to weigh the 4 corners of the car with the exhaust in place so that we can design the weight balance of the new system with this in mind.

With the couple snuggled in for the night, I leave you with this little video of how great she sounds with no exhaust.


Sorry, I don't think the YouTube function worked too well for me.

Until next time,

Paul
 

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Discussion Starter · #4 ·
Today we finally took some tools to the CS. Before we tear it down, we thought we would repair the exhaust and service/adjust the clutch just so that we could run the car some. We will be selling off the entire drive train and wanted to shoot a driving video - running through the gears around town. Once we got the car up and took a deeper look, it was clear that a quick repair wasn’t going to happen. One of the downpipes bends had been pulled out of shape enough that it no longer lined up on each end. The other downpipe had taken a portion of the rear manifold with it. While it is all repairable, we decided that it was too “exhaustive” and time consuming. Any time spent here is going backwards from our actual goal, so we decided to move forward.



Weighing the CS

We want to weigh the four corners of the car so that we have a good basis for our new weight distribution. Our electric motor, batteries, and associated systems will replace an engine, a tranny, drive shaft, differential fuel tank, etc. The weight of our new systems can be equal to the items we remove , depending on the number of batteries we end up using. The minimum number of batteries to achieve the voltage and minimal driving range will weigh a tad less than our current drive train, but additional batteries to increase that range will add to the weight. We are somewhat flexible here, as we are not requiring a 300 mile-range car. We also don’t want to settle for 50 miles. Thus we need to weigh the car now, then weigh it again with it’s drive train removed. We can then begin that engineering. The good news here is that the CS is a fairly light car, weighing around 3100 lbs. It’s current successor can weigh 4500 lbs. Naturally our chassis and suspension is not built to handle that kind of weight, but we certainly do have a bit of room to play with and maintain a fairly light car.



To be economical, we built a pair of scales using some basic parts. Our scales are capable of measuring 600 lbs, so we configured them to measure half-weight. We verified our rig’s half-measurement by weighting an item directly, and then using the scale. Once satisfied, We rolled the front wheels onto the pair, keeping the rear wheels elevated the same amount as our scales. We swapped the scales around a couple of times to verify that the readings were coming back the same. I assume that our final measurements will be off by a very small amount, but certainly within just a few pounds at each wheel which is certainly close enough for our needs.

With a full tank of gas our CS weighs in at:

Front: 1743 lbs. (Drivers 916 lbs, Passenger 827 lbs.)
Rear: 1427 lbs. (Drivers 719 lbs, Passenger 708 lbs.)
Total: 3170 lbs.

Hood Upright Repair

The drivers side hood upright arm had been poorly repaired at least a couple of times and had failed again. We will likely move to a more modern and lightweight approach of gas-charged struts, but for the time-being we figured we should properly fix the stock setup. The sledgehammer that we had been using to prop the hood up has far more important jobs to do.



So that’s it for today. We hope to get in there again next week and have a drivetrain removal party.

Cheers,

Paul
 

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Discussion Starter · #5 ·
1974 BMW CSE Progress

Setting Up Shop

https://bmwcse.com/buildblog/2018/10/12/setting-up-shop

Last week was mostly spent setting up the shop. My A/V company has some extra warehouse space so after moving various pallets of amps, speakers, theatrical lighting, we found a nice corner for the project.



We aren’t swimming in money, but we do like the safety and efficiency of a hydraulic lift. It made sense with the amount of fabricating that needs to be done top and bottom, in addition to the typical restoration work.

To save $400 in freight, I opted to pick it up in Los Angeles. Using my short-bed Tundra only half of it hung past the tailgate so wheelies were enjoyed in rush hour traffic on the 405.



Once the lift was setup, we finally got to get a good look under the car. We found various rust repairs that appear to have been performed in decade intervals. I was surprised not to see any duct tape.

This is going to be more fun than we thought!
Finally, we printed out and posted a reminder of the goal on the wall. When we find ourselves elbow-deep in rust, welders, batteries and wires we may risk losing sight of the dream. I assume that a poster will be all it takes to get us back on track :)



Until next time,

Paul
 

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Discussion Starter · #6 ·
Re: 1974 BMW CSE

Out with the Old

This week we saw our first real milestone: Removing the 3.0 straight-six motor and drive train. It was bittersweet to be sure. It is not lost on me that this (and every) BMW straight six is a beautiful piece of engineering. I have had a number of people remind me that I am ruining a classic combination of coach and motor by converting her to electric.

On that note, last weekend I rode along with a friend on a two-day rally through the Southern California mountains and deserts. In the group were some of my favorite gas-burning vintage cars: Porsche’s, BMWs, Austin Healeys, Triumphs and more. We drove my buddy’s terrific vintage Alfa Sport Sedan. These great cars offer their drivers the enjoyable chore of working the clutches, gears and non-electric steering through the curves and the grades. The feeling returned from this enthusiastic driving is pure joy.

I wanted so badly to take the coupe on this drive before it’s disassembly and restoration, but neither exhaust nor clutch it was pretty much out. All weekend long I kept thinking about what I was giving up by removing the soul of the vintage machinery for the advantages of the electric. But the CSE is to be my daily car. A weekend of smelling like exhaust, fuel and coolant is awesome with a bunch of car guys, but not ideal for a board meeting or date night. I am trying to build something that can give me a slice of the vintage soul in a “scent free” edition, so that I can enjoy it every day.
Out with the Old

Before we strip the car all the way down for it’s proper restoration, we wanted to find out just how much the drive train weighs. The engine, transmission, drive shaft, differential and cooling system weigh far more than our little electric drive unit. But the tank of gas weighs a fraction of our new fuel: Batteries. In order to achieve our goal of 250 miles of range we need quite a few of those heavy beasts. A few posts back we weighed in the coupe in at 3170 lbs. We are hoping that the drive train is a large amount of that weight.

Things got off swimmingly. We started at the rear with fuel tank and the differential. We thought the diff would be maybe 40 pounds or so. We were happy to discover it a beastly 85 lbs! We were off to a good start. We left the half-shafts going to the rear wheels in place as those (or replacements) will connect to the Tesla drive unit. We then removed the drive shaft and the shifter. Finally we unbolted the transmission and motor mounts and lowered the car. We then removed the radiator and anything else involved in making the car go. Everything else stays in for the moment. We drained and properly collected gallons of various liquids, but somehow still had to mop up gallons more. A pesky tie rod that was interfering was just not interested in coming loose. Perhaps we could have pressed her apart, but it was more fun to whip out the grinder. At least we used safety glasses.

After a few careful hours and one forklift, the motor and tranny were safely out of the car and on a pallet for it’s future owner.
What’s the Verdict?

With no drive train our coupe weighs in at:

Front: 1020 lbs. (Drivers 576 lbs, Passenger 444 lbs.)
Rear: 1140 lbs. (Drivers 588 lbs, Passenger 552 lbs.)
Total: 2160 lbs.

Drive train approximate weight: 1010 lbs.

In rough numbers, our Tesla drive unit weighs 295 lbs, and the battery modules weigh 55 lbs each for a minimum of 550 lbs. This brings us to 855 lbs. Add to that the weight of our fabricated mounts, battery enclosures, battery management and charging systems, and it appears that we should be able to end up about the original weight of the coupe. If needed, we still have the option of lighting up other portions of the car such as seats, carbon-fiber hood and more. We are exploring some suspension options that could be lighter and more friendly as well.

Until next time,

Paul
 

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Discussion Starter · #8 ·
I very much appreciate your thoughts- so I won't defend myself, but I do have a few thoughts- and I wonder what you think back...

Yes I was happily surprised at the weight. While my scales aren't completely accurate, they are accurate to themselves, and since my first weight was very close to what BMW says the car weights, I know that I am extremely close.

Regarding the LR difference, that inline did lean way into the passenger side, so it makes sense for the amount of difference there- though more than I expected. And with a full tank of gas removed from behind the rear passenger tire (and the spare tire still in) the rear balance made sense to me. I may ditch the spare, but wanted to leave it in for this purpose.

Regarding my 10 module minimum. It is enough to build up the voltage, but true, not nearly the range. Still, the Model S is 4800LBS, and my car 3170. That is fairly significant to the performance and range I should expect. I do hope to get 12 modules in there, but I think my weight to performance ratio will top out about there. 16 modules in a 4800LB car that gives 300 mile range versus 10-12 modules for 3200 pounds and I should beat my 250 mile goal. I had the 70D with 240 miles and I was very happy for everything around So-Cal.

I wonder your thoughts...
 

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Discussion Starter · #11 ·
Thanks guys-

I think that we may have landed on a couple of points - Even the Tesla gets less range at freeways speeds. I could never get 240 miles on road trips in my Tesla, but I would easily get that around town. So when I say I am hoping for 250 miles it is mostly certainly around town. Without the Superchargers I used for road trips, this car will certainly not be used for long hauls. Besides, living in L.A. we are lucky to get up to 30MPH on the freeways. So I don't think my 70's aerodynamics are going to hurt me:). So with my 10-12 modules I might be pretty optimistic, but not crazy I don't think.

Great points on all the rest. That is why I am here- to keep learning from you all.
 

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Discussion Starter · #14 ·
A little more detail on this issue...

That's 96 pounds difference, and 4.4% of the total. The car appears to have been set up to handle the offset engine, and will likely need some tweaking after half a ton or more of EV components are added (in different positions from the original powertrain).

It's a relatively small detail, and I'm sure that most builders wouldn't worry about it, but since you have the individual corner weights and are building a car known for handling, it would be a good detail to sort out... eventually.
Brian- thanks for that, I appreciate your details here. My post is from my blog site (which has to appeal to all types of folks- some that just want to follow the project for fun) I didn't get too into the WHY I was weighing the corners. It was certainly to find out exactly where I can be putting in these components. We are literally making bricks of battery modules the same size and weight so that we can insert them and weigh the car with various scenarios.

While this is to be a normal car- not a track car- I do want it to behave extremely well for spirited driving as a car enthusiast.

So I very much welcome your thoughts on this- I am excited to fit in the components in such a way to better the original weight distribution if possible. I will be trying under the rear seats as well as a bit out back- but using the engine compartment for a majority.
 

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Discussion Starter · #17 ·
Re: 1974 BMW CSE

Here's another update from the blog. Nothing EV specific yet, but getting closer:)

November was an extremely busy month outside of this project. We only were able to fit in a few half-day sessions on the car, but that was enough time to get her stripped down and sent off to be blasted.

The Hanz and Franz Effect



Since Karmann had coach-built these cars for BMW, we discovered some very interesting peculiarities as we were disassembling. At the risk of sounding insensitive (but with a tribute to Saturday Night Live) we dubbed this the “Hanz and Frans” approach to building cars.

The best we can tell, Hanz was responsible for the driver’s side, while Frans assembled the passenger side. Where Hanz would use a 5mm phillips screw to attach a bracket, Frans would use a 6mm hex bolt to attach the same bracket on his side. One might argue that this was not the case - instead attributing it to 44 years of repair work done by various people. Probably so. We prefer to imagine Hanz and Frans starting the day with a good strength workout, putting down plenty of sausage, then getting to work assembling the car each using whatever bin of fasteners they had handy.



The Quality and Design

On the other hand, it was equally fascinating to discover some wonderful engineering and design. The dash for example. While it appears to be robust component, it is instead a series of small layered assemblies. The steel of the dash frame forms the entirety of the shape. Wonderfully high grade plywood forms the dash trim pieces themselves, and 44 years later, they are still in terrific condition.

We bagged, tagged, binned, and categorized every part on the car. So many trim pieces are in terrific shape and can go right back on, while so many more will be cleaned, straightened, polished, painted, wrapped, powdered, or chromed.



We had great fun cutting away every bit of wiring in the car. One buddy that dropped by left in horror wondering how we were planning to recreate the wiring harness. We could hear him yelling as he drove off “So long suckas- have fun putting that back together!”

We wanted to start fresh with the wiring for a few reasons: First, none of the wiring that had to do with the gas motor will apply. Second, we want to modernize how the lights and windows are powered. No longer does every light, motor and switch require several wires running to it. We will be running LEDS for nearly every light, so fewer, smaller gauge wires can be ran to just about everything. Finally, we need to account for the 12v side of the EV systems. For the combination of these reasons, we want to design an entirely new wiring schematic. The goal is that it will look like we bought and installed a modern factory wiring harness.

Off to the Blaster



Finally, she was ready to head to the blasting shop. We agonized about removing the suspension and fabricating a dolly for her, but in the end we opted to send her off on her own tires. We will remove the suspension when she returns and finish grinding and sanding those last sections ourselves before we begin the metalwork.

We can’t wait to see her return as bare metal. We have new floors and frame rails ready to weld in along with a number of other areas which we will better evaluate when the paint is off.

Until next time!

Paul
 

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Discussion Starter · #18 ·
A little more on the space in the rear...

The E9 seems to have the space under the trunk divided down the middle, with the spare tire well on the left and the fuel tank on the right. See the third-from-last image in the restoration link above for illustration..
Hi Brian,
Thanks for all that. Yeah, as we were stripping her down we began to so some basic imagining of these locations. It seems certain that we should be able to get a couple of modules under the rear seats. We do figure to stack 2-3 rows high in the front engine compartment, but want to leave enough space for an A/C unit and other items. We removed the large vacuum unit for the brakes and will provide electric power for that to free up more space.

Perhaps when the car comes back clean I might take a batch of photos at even angles and draw in to scale some of these ideas. Love to hear what you and the others have to say based on those. Clearly you might have reasons why some of my ideas wouldn't work, and that is exactly what I am looking for with this group!

Thanks again!

Paul
 

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Discussion Starter · #24 ·
Happy New Year folks! Here's another blog post update from bmwcse.com:

Swiss Cheese and the Rebar Method


Last week the coupe arrived back from the glass blaster. We knew that we were going to discover hidden issues, so we weren’t surprised to find quite a few areas with poor metal work and plenty of filler covering things up. The car had been repainted 10 or so years ago, and one can hide a lot of sins under a fresh coat of paint.

Now that all is exposed, we have plenty of Swiss Cheese holes. Behind the sunroof (where the water drains had clogged decades ago). On fenders, behind rear wheels, doors and more.


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The Rebar Method



What we were not prepared to see was rebar. Inside the driver’s front wheel well was plenty of fiberglass, reinforced with rebar and more fiberglass. Scott, our faithful blaster said that in his years of blasting restorations he has never discovered rebar as a structural component. I never thought that Home Depot would have many parts for auto restoration.

As bad as this is, we already knew of a lot of repairs in the strut supports, so we won’t let this beat us down too much. We will source new metal and get it cleaned up properly. It’s too early to get beat down yet.
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Battery Module Placement




Now that things are finally clean and free of grease, we took an opportunity to dry-fit some foam models of our Tesla battery modules. Through our research we know that we can run these units vertically with very little gap between them - as little as 3/16” if we configure mounting rails just so and our wiring setup doesn’t push the bolts to the next module. In this photo, we have 9 units across the engine bay (but we may need to reduce this to 8 to allow a bit more room for reality). The far left and right unit are sitting on frame rails, but the center units are extremely low in the bay.

We then add 2 more where the radiator sat, and finally up to 4 more can stack flat on top of the main cluster of modules. This gets us 14+ all in the engine bay, and the bulk of the weight will be much lower than the engine weight which sat much higher in the compartment.

To keep the center of gravity the lowest, we would prefer not to stack that last 3-4 modules on top of the base cluster. One module does fit under the rear seats with some modification to the tunnel. We would have to perform a lot of modification to get one or two where the transmission sat. Finally we could easily get 2 or more in the trunk, but we prefer to not add the weight back there, as the drive unit is as much weight as we like back there.

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Raspberry Pi for dessert


We picked up a Raspberry Pi with dual isolated CAN Buses and a 7” touchscreen to begin programming our control system. This system will control most of the basic functions of the car from blinking the turn signals, setting the interior to 70 degrees and more. It won’t perform critical motor and braking control, but it will push to the Tesla control unit what preset we are running (i.e. Standard, Sport or Valet modes) I will describe more of these details in a future post.

Well, that’s all there is to report this time around. Happy New Year!

Paul
 

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Discussion Starter · #26 ·
Here's another update from the Blog

Cut, Weld, Smooth, Repeat.

After ordering up a truckload of sheet metal and a 50 gallon drum of perseverance, we dove head-first into rust repair. We started in the rear of the car going spot by spot through the simpler areas. Below are some photos of one spot of the trunk. We cut a section out, weld a fresh section in and smooth it out. Good as new, right? Well yes, after we do this process a hundred or so more times.

Cut out the cancer…Weld in a fresh section…Then smooth it out.

Then there are the floors

While the bodywork is happening up top, we also began work on the floors. The passenger side sub-frame rail underneath was rusted through. We sourced a pair of new replacement rails, but they didn’t really match up to the angle and length at the front. After some debate about fabricating from scratch, we decided to modify these units which wound up working out well. A bit of smoothing will still take place after the floors go back in, and we will move to the driver’s side.

Remember this photo from a few posts back? Looking a lot better now.

Some toys showed up

Our Tesla drive unit, controller, and battery modules have arrived. We have to hand it to HSR Motors/057 Technologies for terrific communication, education, support and packing (thought you wouldn’t know it from these pictures, as it looks a little like Christmas morning just happened). We chose 057 Technologies after a lot of consideration - and I know there are more opinions here than there are stars in the sky. We tossed around buying a totaled Tesla at auction, and stripping her ourselves of all her goods. We considered saving a few bucks and buying from any number of cut-rate dismantlers. Lastly, was the idea of buying from a shop that specializes in Tesla and EV conversion support. After visiting some, and chatting with others, I felt like I bought into not only the passion, but the engineering approach that 057 has taken with their controller, but also the drive units themselves.


We will surely see if we made the right call once we can dive into this gear in the coming weeks. In the meantime, it is back to Cut, Weld, Smooth, Cut, Weld, Smooth, Cut, Weld Smooth…
 

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Discussion Starter · #28 ·
Re: 1974 BMW CSE

Hi all,

While this post isn't related to the EV portion of the build, I just want to continue to paste over the updates from the bmwcse.com build blog.

Here Comes the Sunroof

You might remember that one of my requirements for the coupe was that it have a sunroof. Of the 60 or so cars I have owned, a majority of them have been convertibles - I simply crave the open air. While this car was not going to be a convertible, it was most certainly going to have a sunroof.



But our story takes a turn with the little tube shown in this photo. The photo shows a new tube, but imagine one just like it that was plugged inside like a clogged drain. This tube, along with 3 comrades, takes the portion of rain water that makes its way through the sunroof seal, and passes it into hoses that run to the bottom of the car. This is a great plan so long as the tubes aren’t clogged, and in our case, the tubes had become very clogged, very long ago. Water would come in and take up permanent residence - turning our roof and the sunroof frame mechanism to rust.

We were unaware of this rust until the car came back from the media blaster. We were then faced with three options: 1, we simply fill in the roof. This is the course that any sane person might take. But since a sunroof was an early requirement, this was not an option. 2, we could fill it in, then install a very nice modern OEM electric sunroof. Our car is a “resto mod” after all, so a blend of modern elements is not out of the question. However, another goal is to retain the classic styling of the car, and the original steel sunroof is an important part of that. So our 3rd option was to painstakingly rebuild the roof and frame. This took a few good weeks to do, and here is the story:


Here is the roof from inside the car. Rust on all four sides.


The damage to the frame (the sunroof track) was even worse than the roof itself.

Let’s make a new roof:


Trace the sunroof hole and prep it for cutting.


Cut along the line- this part seems a lot like elementary school art class but with steel.


Begin the process of bending the edges to form our thick and smooth final edge.


Continue the bending and shaping process with the panel setting on the car.


Finally we have a panel which is looking like a final product.


Weld the piece in, then smoothing, smoothing, smoothing.



We also found that we had to strengthen the sagging steel behind the sunroof as well. We then smoothed and smoothed and smoothed some more.

In the end we now have an entire roof that is better than new.

Continued...
 

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Discussion Starter · #29 ·
...Continued due to the limit of 10 photos- all of which I have hosted elsewhere 🤨

Repairing the Sunroof Frame

The jig is up. Well, in the photo the jig is on the bottom and the frame is up, but you get the idea.


Our frame attached to the jig.


With the frame on the jig we can cut out sections and start replacing them.


Tyler is a patient craftsman. Give him some steel and some tools and he can turn out just about anything.


Here’s a fun, rusty rounded corner,


And here’s the new replacement piece all clean and tidy.


All the new sections welded and smoothed into the frame.


The restored frame receives a fresh black coating.


Installing the frame back into the coupe. Tyler loves crawling around grinding things in the car.


It’s looking good from up above.

Finally we set the sunroof back in and check the fit. The gaps are cleaner than when we bought the car. With our new drain tubes and fresh hoses, as well as a new seal in place we should be good for another 45 years of open air, rust-free enjoyment.


While all this sunroof work was going on, there was a lot of junk going on in the trunk. Next week I’ll post an update on all that.

Cheers!

Paul
 

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Discussion Starter · #30 ·
Here is another post from my bmwcse.com Blog

While all of that sunroof work was being done Brett and I started to have some fun with the Tesla drive unit.



We are not the first people to retrofit a Tesla unit into another car. We leveraged some of the engineering, trial/errors and successes from some of the more graceful projects that we have followed.

We started by clearing out the trunk floor. We want the motor to sit no lower than the original differential, but also no higher than necessary - leaving us with a good amount of trunk space.

Getting off the Ground

Our Tesla unit weighs 291 pounds, so I can’t exactly hold it in place while Brett bolts it to the car. We welded up a rolling stand that could safely hold the unit under the car, then we would use the car lift to lower the coupe to the unit.

Here’s our Tesla motor stand. I am going to reach out to Elon to see if he wants to put an order in for several:)


A forklift is the closest thing we have to an engine hoist, so here we go.


The unit feels secure in its temporary home.


Reinforce and Fabricate

With the unit on the rolling stand we put it into position to verify our mounting design and overall clearances. We strapped the rear wheel into a relative ride height, so that we could check the axle angles.

While we had done our homework I am not going to lie - there was some relief when everything fit without obstructions.


Tesla Unit in Position


Regarding the mounts: There is a front mount which was a simple matter. The side mount can be tricky since there is suspension right there, and the rear mount has nothing to hang from.


We plated the front and rear of the wheel well to distribute the loads and to give us something to attach to.


Brett welds in the horizontal plating, which will support our front mount.

continued below...
 

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Discussion Starter · #31 ·
The Front Mount

(Sorry I don't know if I figured out how to present YouTube videos)
Cutting the thick stuff is like cutting warm butter when you have a plasma torch.


The front mount had the trickiest shape to it and required some bending of the center plate.


The front mount welded into the car.

The Side Mount


We created a side mount plate with a compound bend by notching, then smoothing out.


Welding the side mount sections to our plate.

The Rear Mount


The rear mount suspends from a beam which spans between the wheel wells.


Reinforcing the hanging points with gussets. It was just an opportunity to take a photo through the taillight hole.

Clean Things up and Hang the Unit


With the welding done, we cleaned up any rough edges and applied etching primer to everything.


Finally the drive unit is hanging in it’s final home! We strapped the front of the car down to the lift just in case things got a little back-heavy:)

The moment of truth when the Tesla unit is successfully raised off its stand.


The placement leaves plenty of usable trunk space. We have a large and deep rear section, then an upper forward shelf (with perhaps a plexiglass floor for any Cars & Coffee events we may find ourselves at).

Next we connect the axles from the drive unit to the hubs. So that we don’t twist the old BMW axles we opted for Tesla performance axles, which will mate (somehow) to the BMW hubs.

That’s it for now- until next time!

Paul
 

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Discussion Starter · #34 ·
Brian,

Thanks for the thoughts. You are correct that we did cut off the bracket that held the front of the Diff, and the rear of the Diff did connect to the car forming the tee you mention. We do plan to reconnect this tee structure in some form.

It is a bit of a strange setup, as the point of isolating this front unit (in my estimation) was purely to isolate the differential vibrations from the car. Front drive cars often simply attach the trailing arms to the car itself. So we are doing a bit of research to determine the best course modifying this. Either we reverse the tee shape forward and connect it with a mount (with bushing) in the tranny tunnel, or we simply shorten the tee and attach closer to the Tesla front mount.

Thanks again for your thoughts and concern - it's what I love about this group!

Paul
 

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Discussion Starter · #38 ·
Yes, we considered quite a bit the idea of attaching the front motor mount to the suspension subframe. In the end we saw a lot of well done cars where the drive unit was attached to the car directly- using the Tesla motor mounts as the isolation. Naturally them (and us) all created distribution for the loads of those mounts.

To use the subframe for even one of them would mean not using the Tesla motor mount as it would require a multi-bolt setup (in the same manner as the 4 bolt setup to the differential- which was acting as a bridge to the rear mount to the car).

We decided on this route as the simplest and most robust. We did certainly plan for the 2000lb. We aren't auto engineers, but we do a lot of structural work where we have to account for 7x the maximum expected load for rigging. You can probably tell by the type of steel beam we used in the rear :) It looks more like we are hanging speakers above an audience in a fine arts center...

Regarding that subframe 3rd mount, I am doing a bit of research on just how much torque she will see. The 20" back or so that it attached in the past was because she experienced a lot of torque to spin the wheels. Now she does nothing but go along for the ride. The main thing is to lock her in so that the two main bolts aren't expected to do all the work- they would shear eventually. So I thought of going perhaps 12" or so forward in the tunnel and attach with a generic isolated motor mount, or even as you mention, straight up to our front Tesla mount (other than it being crowded up there).
 

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Discussion Starter · #42 ·
That's great ,
Maybe I missed out , but , how much modules will you put in ? , all 16? to get proper voltage..
We are starting with 14 modules, which is the old Model S 60 configuration. It will be very tight getting them in. We were able to get 14 foam models under the hood while accounting for just enough between them for connections and mounting. But it was still best-case, and our brake booster - while smaller than the original- will still eat up a bit of that space that we tested with.

So we may wind up with 2 modules in the rear (above the drive unit where I wanted that cool plexiglass section to be). We could put one under the rear seats if we had to, but I don't want to have them spread out under every knock and cranny :)

Bottom line is, 14 modules to get our minimum voltage, then if we do wind up better off than we think we will certainly add 2 more to bump up kWh.
 
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