As we connect the dots backward.
I hope you read our previous blog, where we demonstrated how we electrified a Mercedes Benz S-Class from August to October 2022. Here’s a glimpse of the next three months of drill that we had.
It continued to provide us with invaluable insights, and data about our platform. It helped accelerate the core VCU requirement definition and development for us. We also realized that the pouch cell form factor wasn’t suitable for us. Cooling the pouch cell while keeping the weight down proved to be a difficult task. Unfortunately, a few of the pouch cells also bloated (and had to be immediately replaced), even while on standby, further ruling them out completely!
While continuing to test the S-Class, we progressed toward creating an actual truck-based platform. However, adhering to the fundamentals of Delta-Engineering, this time we focused solely on changing the powertrain from ICE to electric, understanding the load conditions with our battery packs, and limiting development to create what people in this industry call a COWL.
If you ever need to buy a partial truck or its parts in kilograms (not sure why you would, but just in case 🤣), you should visit Siddaiah Road in Bangalore! There, you’ll find shops with small entrances that magically expand into massive storage warehouses for trucks and parts. Here, hundreds of cabins, engines, huge gearboxes, and parts are stacked on top of each other. The store manager can point you precisely in 3D to any part you might be looking for! It’s something you have to see to believe!
By November 15, we had determined what would meet our requirements (a stripped-down Tata 1109 without its cabin and body). We picked an 11-tonner, as that was the maximum size that could fit our garage back then. It also had the maximum turning radius with which we would take it out of our basement. By the 20th, our frame was ready to be electrified!
Now, these were the new problems that were staring at us:
- Chassis – we didn’t want to alter the existing chassis, as it’s a project in itself. We couldn’t optimize it because we didn’t know the actual loading conditions. So, how could we achieve our “battery in the chassis” objective?
- Gearbox – We needed a gearbox! Powering the S-Class directly from our motors was straightforward as the torque requirements weren’t high. But to meet our target, we needed at least 12,000Nm on the tires! Every electric truck in the world (and diesel, for that matter) has a 6 to 11-speed gearbox!
- Clutch – An extremely small fraction of the Indian trucks have automatic gearboxes (we couldn’t get one for our rating), and manual gearboxes need a clutch! And we didn’t want to add a clutch, for reasons you can probably guess.
- Air Compressor – This time, we needed a far more powerful electric air compressor, not for the suspension but for the brakes! The eVerito is too weak to power the air compressor for the brakes on a truck, and no one in the country manufactures one!
Entering debugging mode, we decided to:
- Create another chassis that would act as the supporting structure for our batteries (as in the final design), and mount it on top of the existing chassis. This provided us with an additional load to test our vehicle.
- Use the same gearbox that powered 1109, as it had the gear ratios we wanted.
- Implement a digital clutch. Whenever a gear change was required, the motor would enter a neutral 0-torque mode, and the gear could be changed easily. (In later systems, we would first match the motor RPM with the required shaft rotation for smoother shifts). Also, Tresa is building eAxles, so the motor, automatic gearbox, differential, and motor controller would all be integrated into a single independent unit!
- As for the air compressor, that was a tougher problem to solve. Initially, we finished the pneumatic circuit and “charged” the air tank externally, our engineers told us that now we can apply brakes 20 times 🤨! (Yes, we all felt it was a bit strange hearing this for the first time😂) Finally, we had to design one internally using components from an industrial AC compressor, coupled with a DC-AC inverter to get the platform functioning properly. This solution wasn’t super-efficient, but it was perfect for our tests.
By late December, we had finished machining the motor mounts and other mechanical parts. This time, we needed a huge coupler to connect the drive shaft with the motor, and an additional hydraulic lift to work with now-super heavy components. The electronic and electrical integration was less challenging, as we had solved most of the problems while electrifying the S-Class. We spent the latter half of January on full integration and testing, and by the 2nd of February, we were ready to test our COWL!
Working with a passionate team that loves creating together feels amazing! Getting this project up and running presented its own set of unique challenges and even more creative solutions! Check out this short video that we made to give you a behind-the-scenes look at our COWL testing process.
I have spoken multiple times about our Axial Flux motor. There are only a handful (around 10-11) manufacturers of this motor in the world at our power rating! But what exactly is an axial flux motor? What makes it so special that Daimler actually purchased a company that manufactures them? How did Tresa become India’s first Axial Flux motor manufacturer delivering such high power?
There’s so much to share and explore on this parallel journey at Tresa. But we’ll have to wait until the next blog to delve into those details. See you soon!