# 1938 Rolls Royce Conversion



## Maximum Turtles (Aug 12, 2018)

Hey all. I've started work on a very ambitious project to convert a 1938 Rolls Royce 25/30 to electric power. I'm a master technician at Tesla, with a heavy specialization in electrical/computer diagnostics and repair, and I'm partnering with a gentleman/artist who has a long history of fabrication experience.

The subject of the conversion is a 38 Rolls Royce 25/30 that has been sitting garaged for about a decade with an engine that needs a serious overhaul. It was left to my partner by his mother, and he has already begun modifying the body to be an "art car." It's seen better days, but I have a good deal of restoration experience already under my belt, and my partner is a very accomplished craftsman, so the restoration part of the restomod is less daunting.

The donor vehicle, still to be acquired, is a Nissan Leaf. I am very well versed with CAN diagnostics and "hacking" (tricking the network into thinking it's healthy enough to function, mimicking commands/data sent by modules in the network, etc) and plan to do a live transplant with all necessary or usable components. We are aggressively visiting salvage auctions in an attempt to find a suitable power train donor.

https://www.dropbox.com/s/xm40bcdajzrkqbk/IMG_20180815_173752.jpg?dl=0

We're trying for a budget build, though we're not suffering under the delusions that this will be cheap. By budget, I mean only that we aren't prioritizing performance or impressive range over the goal of simply getting the vehicle driving under its own power without going bankrupt.

I know others have dissected this power train quite a lot, big props to miscrms for the extremely thorough documentation of his findings, but I'm sure I'll be coming here a lot for help over the next few years.

Wish us luck everyone, we're gonna need it!


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## piotrsko (Dec 9, 2007)

If you are a tesla tech why use a leaf? The price and availability for both salvage vehicles is similair unless there mechanical advantages.


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## electro wrks (Mar 5, 2012)

This a big, heavy car. I think you will be disappointed with the only ~100 HP available from the Gen1 (and Gen2?) Leaf power train. Supposedly, ~200 Hp will be available the next Gen. But, of course, that won't show-up on the secondary market for some time.

This car is probably long enough to accommodate the complete Mod 3 battery box/electronics hump assembly. With you folks cranking out so many 3s, soon there's going to be a glut of them on the secondary market. With a full frame on the Rolls, body off frame mods may be needed. https://mfpclassiccars.com/rolls-royce/52160-phantom-iii-frames.html .The hump will probably fit under the rear seat, like in the Mod 3, with room to spare. If there is enough ground clearance available, mount the Mod 3 assembly below the frame. The running boards may have to be modified or moved to fit the width of the battery box. 

The rear drive/ suspension, as with using the Leaf parts, is going to be a challenge. The Rolls has a live rear axle with leaf springs. A de Dion suspension, like used on the Ford Ranger EV, might work. 

Not my kind of project. But it looks like fun and a great conversion challenge!


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## Maximum Turtles (Aug 12, 2018)

We're not looking for power here, by any stretch. The stock motor coming out was an underwhelming 29 HP, after all! And the weight with its enormous engine and transmission is under 3,000 lbs, swapping in Leaf components I expect to see a final weight around 3500-3800 lbs, not far off the stock Leaf.

The live rear axle is a little frustrating, it would have been nice to use the stock Leaf reduction/differential, but removing the reduction gearbox and running a 2:1 reduction out of the motor into the 4.55:1 differential gives us a single speed gearing that is fine for our needs.

Body off frame mods are a certainty, but something we've both done before. The plan, still to be edited as measurements are made and bad ideas spotted, is to make 2 additional crossmembers to support the weight of the motor and gearbox behind the front seats (the rear floor is being remade completely, clearance is no issue), and an upper torque mount, then run a CV axle from a Tesla from the gearbox output to the differential input, using the stock rear axle and suspension. I could think of a million more elegant solutions, but all are more expensive and complex to execute. I'm trying very hard to resist the temptation to over-complicate things as I try to get this thing on the road.

I'd love to run Tesla components, but unless I'm missing a nice treasure trove of cheap Tesla parts, I'm not finding anything approaching the cost of the Leaf. I've been stalking auctions for a while, and it's not uncommon to see a "Runs and Drives" Leaf go for less than $4.5k, but I rarely see a Tesla in any condition go for less than $10k, let alone one whose battery I would trust. What kind of prices are you seeing for salvage Teslas?

The M3 battery has been the bottleneck of manufacture pretty much the whole time we've been trying to get these cars out, so I'm pretty sure its going to be a long time before we can count on finding those laying around. Range and performance are not priorities here, a degraded 24 kwh pack should be okay for getting around town on occasion.


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## brian_ (Feb 7, 2017)

electro wrks said:


> This a big, heavy car. I think you will be disappointed with the only ~100 HP available from the Gen1 (and Gen2?) Leaf power train.


Perhaps. On the other hand...


Although the Rolls-Royce 25/30 had a big engine, this is old stuff, so it only put out (according to one source) 115 bhp @ 4500 rpm. With a broader power band, the Leaf motor should be very comparable.



Maximum Turtles said:


> It was left to my partner by his mother, and he has already begun modifying the body to be an "art car."


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## Maximum Turtles (Aug 12, 2018)

Thanks for all the interest, the 25/30 title actually represents the range of horsepower these hand built engines had. This is the last of the "small horsepower" Rolls Royces, this one came from the factory with 29.4 horsepower at the flywheel. I'm really not worried about performance. 

I'd love to go with Tesla parts, but I can't find them anywhere near the cost of a leaf drivetrain (or even for twice as much). If you spot something like that, let me know and I'd jump on it quick!

Going over the Rolls and getting everything in order has revealed some surprises. The mechanical linkages on this vehicle are really something else. Unfortunately that means that the brakes won't work without the stock manual transmission!

So it looks like we'll be doing a more conventional EV setup with a motor adapter plate. We'll just have to be careful not to thrash the poor old gearbox. After finding mpaulholmes's motor controller board replacement for the EM61 inverter, I'm reconsidering the concept of a live transplant. Too much dead weight in the form of unnecessary modules, and inless I convert the Rolls brakes to hydraulic using the leaf master cylinder or otherwise spoof the cooperative brake system, I wouldn't be able to get regenerative braking working. 

The only thing I'm clinging on to is the battery/BMS/charger bundle that would come with the leaf. Going to spend the next few days comparing systems I could come up with on my own for them.


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## electro wrks (Mar 5, 2012)

As I recall Rolls, for a time, would only list their top speed and HP ratings as "adequate". Also, this car is from a time when posted allowable top speeds were only 45MPH or less. 

What is the connection between the trans. and brake system?


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## Maximum Turtles (Aug 12, 2018)

That sounds like a Rolls Royce thing to do.

I'm glad someone asked about the brakes, they're a fascinating bit of automotive history. The transmission output shaft is geared to a second output, running straight out the left side of the transmission. This shaft rotates a clutch inside a drum that is normally not engaged. When the brake pedal is pressed, the clutch engages (but does not lock), twisting the drum. The drum is linked to a T shaped piece that pulls brake cables for the front and rear, in such a way that whichever way the output is turning, the torque of the drum will assist braking.










Totally mechanical, totally cool, totally inconvenient. I though about substituting a motor linked to a brake switch for the drum, as all this system provides is torque on demand, but I think I'll stick to as few risky ventures as I can. For now, keeping the old trans will do.


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## electro wrks (Mar 5, 2012)

Yes, but I'm regretting for having asked! The trans. has an output shaft driving a rotating clutch set-up to provide power braking, through linkages, from the mechanical inertia of the engine?!!


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## brian_ (Feb 7, 2017)

Maximum Turtles said:


> Thanks for all the interest, the 25/30 title actually represents the range of horsepower these hand built engines had. This is the last of the "small horsepower" Rolls Royces, this one came from the factory with 29.4 horsepower at the flywheel. I'm really not worried about performance.


While I don't see a reason to be concerned about performance, that engine puts out a lot more than 30 horsepower. The 29.4 value is the result of the old British taxable horsepower formula, which is based only on the bore dimension (3.5"), the number of cylinders (6), and the typical output of engines circa 1910. Actual output of a late 1930's engine would be much higher, which is consistent with the 115 horsepower reported by another source. The Leaf motor should be a reasonable replacement.

RAC horsepower rating
(D * D * n) / 2.5 = 3.5 * 3.5 * 6 / 2.5 = 29.4
where D is the diameter (or bore) of the cylinder in inches and n is the number of cylinders

As an example of how irrelevant this formula is now, the current 455 hp Corvette engine would be rated at 52.7 hp.


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## brian_ (Feb 7, 2017)

electro wrks said:


> Yes, but I'm regretting for having asked! The trans. has an output shaft driving a rotating clutch set-up to provide power braking, through linkages, from the mechanical inertia of the engine?!!


Not just inertia but driving force - the engine continue to run, even if only at idle.



Maximum Turtles said:


> I though about substituting a motor linked to a brake switch for the drum, as all this system provides is torque on demand, but I think I'll stick to as few risky ventures as I can. For now, keeping the old trans will do.


Another approach would be to keep the clutch drum and turn it with a constant-speed electric motor. A huge waste of energy, but closer to the original design.


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## electro wrks (Mar 5, 2012)

brian_ said:


> Not just inertia but driving force - the engine continue to run, even if only at idle.


Sorry, that's what I meant to write.


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## Maximum Turtles (Aug 12, 2018)

Thanks for that info, Brian! I had no idea about this system, and was taking the horsepower number at face value. That's actually a bit of a relief, I didn't want to subject the drive train to several times the original stress it was built for 80 years ago. I've found several sources quoting several horsepower numbers, mostly around 85, but none that say how they've come up with such numbers. 

There are definitely some easy ways to imagine getting the servo working again with a new drive train, but the added complexity and risk has tipped the scale for me to reusing the original transmission.


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## Duncan (Dec 8, 2008)

That old "Horsepower" system is why these old engines all tended to be very long stroke - the TAXED "horsepower" was set by the engine Bore

So by having a small Bore and a long stroke you could get a decent sized engine but only pay taxes for a small one


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## Maximum Turtles (Aug 12, 2018)

Yeah, I was reading that too. Stuff like that is all that seems to ever happen when we try taxing or regulating things indirectly. At least with tailpipe emissions checks, companies have to just blatantly cheat to get around it.


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## Wingsinger (Jul 10, 2014)

I love this kind of project. A friend had a ‘28 Rolls and the mechanical brakes combined with the weight did not make for very good stopping distances.

Upgrading axles and drivetrain could make this easier and more reliable.

I’m starting a ‘28 Chevy sedan, but upgrading the motor, tranny, and axles. I want reliable brakes and relatively low maintenance. The frame is boxed in to stiffen it up, Monte Carlo rear axle, custom front end, classic body.

Best of luck with your project, looks like fun.


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## chicowoodhill (Apr 15, 2014)

Cool project! Cool enough to get a lurker to finally post... 

As to the donor vehicle, you might consider finding a Ford Ranger EV pickup, built by Ford in the '90s but then orphaned (as per the movie, "Who Killed the Electric Car?"). 

I have two of them, each nearly 20 years old. I replaced the aging NiMH batteries (which ran great for nearly 15 years) with Lithium packs, added Orion BMS and Elcon chargers, and couldn't be happier. Much zippier and more fun to drive than my Tacoma. The world really needs a commercially available electric pickup...

Like you, I'm an electrical engineer who knows how to hack the data communications protocols to make the older systems jump through the necessary hoops to do what I want them to do. I've written a Windoze app to replace the Ford-specified NGS diagnostic tool, and designed a few small microprocessor-based boards to make sure all the electronics think they're still living in 1999. Sounds like you have the skills to do similar.

Reason I suggest this is these can be found cheap when the original NiMH or lead acid packs (they came in both flavors) go bad. I got both my trucks for around $2k online...then the Lithium packs and new electronics add in maybe another $8-$10k, depending on how fancy you want to get. I put a Ford Focus 65Ah pack into one of my trucks, which gives me around 60 miles range. The other has a Microvast LTO 100Ah pack which gives around 80 miles. A friend of mine has installed larger packs which give him well over 100 miles. 

Ford won't admit to ever building these but there's a fair amount of documentation available, including the original shop repair manual and wiring diagrams. Unfortunately there aren't schematics of the key electronics boards, which would be very helpful, but part of the fun is figuring out how to either repair them, or spoof them and remove them entirely. Replacement boards are available but getting more expensive as they become more rare. 

I'd say if cost is the main issue, these trucks can be found pretty cheap. But if fully available/non-hassle replacement electronics is a requirement, this might not be the best option. Just thought I'd suggest it so you can put it on your list of possibilities. 

Pictures, please, as you move forward!


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## goingbush (Jun 20, 2017)

have a look at this 

http://www.abc.net.au/news/2018-06-16/vintage-rolls-royce-converted-to-electric-vehicle/9869888


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## Maximum Turtles (Aug 12, 2018)

Thanks for the support guys, really. I've seen a few of those rangers in my area, but I think people around here know how cool they are. The cheapest one I've seen around here was $9k, and that was with a bunch of dead lead acid batteries. If I see one (or really any electric vehicle) that's competitive with the Leafs (Leaves?) I'm finding, I'll snatch it up. 

If there's one thing I'm nervous about on this build, it's the brakes. I looked into swapping axles or doing hydraulic conversions on the existing axles, but every solution would up leading down a very expensive rabbit hole. Current plan is to use the custom controller to set the pedal up for one pedal driving with regenerative braking as aggressive as possible, and just get the friction brakes up to par for an emergency. 

Engine's ready to be pulled now, and we're on the hunt for a deal with a Leaf. Just let an 8 bar 2012 slip through my fingers for $3400, kicking myself a bit. As soon as we find a donor, things are ready to go.


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## Maximum Turtles (Aug 12, 2018)

I saw that rolls conversion before. If they think that's sacrilegious...


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## Maximum Turtles (Aug 12, 2018)

Got a lot of the old stuff out of the car today. Gas tank, most of the fuel system and the exhaust are all out. Drained all the old fluids out of everything and started going through the brakes and getting everything back to working order. Lots of room for batteries in this guy. The area between the frame rails where the muffler used to be looks to be damn close to the size of a battery box containing the rear leaf pack, and the gas tank spot looks like it would fit the rest pretty handily. 

Looking at wiring diagrams of the leaf pack, it looks like the BMS, contactors and precharge circuit are all really easy to repurpose. Does anyone know of anybody ever using the charger or DC/DC box from a leaf in a non-stock application? I'm not sure if the VCM is required for their operation.


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## Maximum Turtles (Aug 12, 2018)

Well the brakes have been a bit of an adventure. Three different special tools are needed to remove the rear drums.

http://www.oldcarmanualproject.com/manuals/RollsRoyce/RR-_V_Tag_-_Hubs-4951.pdf

Have to see if I can machine these tools (if I can work out their measurements) or even find them. Google search results for "Rolls Royce driving dog extractor" aren't promising.


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## brian_ (Feb 7, 2017)

Maximum Turtles said:


> Google search results for "Rolls Royce driving dog extractor" aren't promising.



Fortunately, the driving dog extractor looks like an ordinary two-arm steering wheel /harmonic balancer / flywheel puller... with of course the correct BSF threaded bolts.


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## Maximum Turtles (Aug 12, 2018)

School is starting up again, so time for the project has dropped to about 2-3 hours a week. Got a quote for the tools necessary for the brakes, $1250. Ouch. Decided to see how bad they are before we tear them down. 

Got the radiator and some body panels out of the way, lots of room to get the engine out now. Still amazed at how easily all the nuts and bolts are turning on this guy. Only had a few minor drilling/cutting incidents while removing the radiator. 

Information is murky at best for the servicing of these vehicles, every step yields surprises. Got a whole day off next week, gonna try to get the engine fully out then, but I'm expecting something crazy to happen along the way.


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## itchyback (May 28, 2014)

gorgeous. keep going, you cant lose if you dont stop


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## Maximum Turtles (Aug 12, 2018)

Picking away at this still. Got the engine and all the rest of the ICU stuff out. Starting to clean up and pull the decayed harnesses out. Haven't had a chance to go to a single auction yet, too busy, but eager to get my hands on the donor parts.


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## Ada Diamonds (Feb 9, 2018)

Incredible build! Are you near Tesla's HQ in Palo Alto? I live a few miles away and could possibly help you if you need a spare set of hands to pull the body or whatnot.

Have you considered/is it in the budget to go to with an Art Morrison custom chassis? All things considered, they're not that expensive and you can step up to absolutely bulletproof, safe, proven hardware:

https://www.artmorrison.com/frames.php

It'd be about $12-18k all in for the chassis, suspension, steering rack, brakes, etc. Everything you'd need except wheels. You can design the entire chassis around your chosen battery and driveline as well.

In the long run, that may be a faster and cheaper option versus trying to integrate with century-old parts. 

You could go with a full chassis like this post-war Silver Cloud:
http://car-from-uk.com/sale.php?id=52562&country=us

Or weld modern parts into your existing frame, like this guy building a 1939 Wraith with a weld in independent rear suspension:
https://artmorrison.com/news/1939-rolls-royce-wraith/

Art Morrison has done EV swap frames before as well:


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## hiura (Jul 25, 2018)

piotrsko said:


> If you are a tesla tech why use a leaf? The price and availability for both salvage vehicles is similair unless there mechanical advantages.


No Tesla has ever sold for a few hundred dollars on COPART yet many Nisan Leafs have. Now, please do tell where these places are with sub $1500 Teslas for sale!


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## Maximum Turtles (Aug 12, 2018)

Sorry for not updating in a while, I will update again soon, but quick summary:

Got a Leaf, reverse-engineered the EVCAN BUS enough to get the car charging with only a few key modules. Our current strategy is to use the BMS, DCDC, charger, etc from the Leaf, controlled by the Vehicle Control Module (VCM). 

We have decided, however, to take direct control over the traction motor with a modified inverter control board.

Started body work on the Rolls, and will be pulling the drive unit and battery in the next couple weeks.

Pics, etc to follow.


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## Tremelune (Dec 8, 2009)

Maximum Turtles said:


> Got a Leaf, reverse-engineered the EVCAN BUS enough to get the car charging with only a few key modules. Our current strategy is to use the BMS, DCDC, charger, etc from the Leaf, controlled by the Vehicle Control Module (VCM).


Many are very interested in doing the same. Do you have this documented or the code published anywhere? I couldn't get the BMS and charger working (ditto the DC-DC), though I found a few projects (that were very specific to their platform) that did. How much custom code and Arduinoing did you need to do?


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