Since last time we got a very exciting news. We wanted to start the endurance test on the motors before the production kick-off. Before doing that, we needed to accurately test the motor performance to understand whether the 1000-hour test would have impacted on the performance. In order to do that, we needed a test bench. We initially searched for commercially available test bench, but those were either too expensive ( a bench which can brake 120Nm is a fairy large thing), weren't a good fit or had too long lead times ( 5+ months).
So we decided that we had to build a test bench ourselves. The picture here shows a glimpse of it.
So we took a 13HP electric motor to act as a brake, and we put some moltiplication in the middle, in order to lower the braking torque and increase the RPM, so that the output power of our motor would have been more manageable. The designed the test bench to brake 150Nm in order to allow more margin for the locked rotor torque and we finished the test bench build approx 20 days ago.
What a wonderful torque
During the first test of the motor with the production material we had a very pleasing surprise: at 150Nm of braking torque applied, still the motor didn't stop. And that was the 500W version on test!
Locked rotor torque is the torque that the motor can give you starting from a stop. 150Nm is a very impressive number considering that other mainstream ebike motors range from 70Nm to 90Nm as peak torque.
So we had to modify the test bench to check what was the maximum torque of our system. That modification costed more than two weeks, but at the end we've been able to add an additional mechanical brake to reach higher braking torque.
We repeated the test, anxious to see what was the maximum torque of the BEST motor. We reached 170Nm on the 500W version! Improved magnets, lamination and winding did their job and we surpassed our ambitious target.
This torque is not just a performance figure to brag about, it brings you a real advantage: the optimal efficiency of brushless motors is around 50% of their maximum torque. So if you have a motor with 90Nm as maximum torque, the peak efficiency will be at around 45Nm, so when you're pedalling on a flat road. With 170Nm you can have optimal efficiency at 85Nm, exactly where other motors stop. Higher efficiency means a battery which last longer because energy doesn't get dissipated into heat thus more miles per charge and less stress on electrical components.
Basing upon the endurance test results, we'll decide how much of this torque we'll made available in the production motors, but the efficiency advantage will still be there in any case.
Controller box casting
We launched the sand casting version and the moulds will be ready next week. Some of you asked about the position of the control box, so here's some picture of the box installed on the bike.
As you can see, the design doesn't affect the ground clearance. The color choice of the box will be as the motor, so black motors gets the black controller box. The next 10 days we'll be able to check whether the final look of the casing is acceptable so that we can use them on the production. In the last updated we indicated end of April/ beg of May as a possible shipment, now May is more likely.
Endurance Test is started!
After the motor performance test, we put the BEST system on the endurance test. That will be 1000 hours on 3+ systems. In order to get the motor running day and night at full power, we used a forklift battery.
We made a quick footage to see the endurance test going. Sorry again for the audio and background noise of the bike roller which is amplified.
The system is now doing approx 800km per day at full power.
Getting the right crankarm
The crankarm supplier finally did it right and we're waiting for the first batch next week.
Production line : work in progress
We started gathering all the materials to setup the production line. On the bench there are boxes with the presses and tools, waiting to be put in place.
We'll keep you posted as we plan to intensify the updates in the last final rush since everything is coming together at a higher pace. So you can expect the next update in 15 days.
All the Best,
Matteo, Luca and Bikee Bike Team.