Wisconsin Racing has always prided itself on pushing the limits of design. In spirit of that determination the WR-217e is developed around an all-wheel drive architecture. This architecture utilizes custom front and rear drive units, optimally designed to minimize mass and maximize available torque.
Rear Drive Unit
The WR-217e utilizes a two stage single speed reduction transmission for the rear wheels. This unique gearbox features a custom cast center piece locating two completely symmetric gearbox's to allow for totally independent control of the rear wheels.
This novel transmission allows the controls team behind the WR-217e to fully optimize the capability of the two Nova 30 motors. Each motor is independently controlled to output the maximum allowable torque for the vehicle based on the available traction limit of the tires.
In development the transmission center housing was rapid prototyped using direct metal laser sintering (DMLS) with Midwest Composite Technologies.
Motors: Plettenberg Nova Series
The extremely power dense Plettenberg Nova series motors power the front and rear drive units for the WR-217e. Plettenberg's brushless surface permanent magnet motors were developed from experience, inspiration and devotion to setting the highest quality for a new dimension of electric drives.
The combination of intelligently selected materials and components together with innovative geometry enables the unique drive units.
Plettenberg worked closely with the Wisconsin Racing engineers to optimize the motor configuration for the Formula SAE racing application. Plettenberg's highly skilled team worked for months answering questions and tailoring the motor specifications to achieve the perfect solution for the WR-217e.
In-Hub Motors Assembly
Wisconsin Racing's first in-hub motor design utilizes a 6:1 planetary gear reduction, custom inverted quad piston (IQP) caliper and unique hub configuration.
The calipers are developed in two variations, billet machined 2024-T6 or direct metal laser sintered (DMLS) titanium. The billet machined calipers incorporate external fluid routing while the high temperature titanium calipers utilizes internal fluid routing.
The novel hub motor system will deliver 180 Nm of torque to each of the front tires, increasing acceleration capability by ~25%.
The system was developed with brake design support from Hayes Performance Systems, 3D printing from Midwest Composite Technologies, rotor blank grinding from Midwest Grinding, upright and wheel center machining from Revolutionary Machine and Design, motor design support and manufacturing from Plettenberg Motors, gear analysis support from KISSsoft,bearing analysis support from Silverthin, and gear machining from Edgerton Gear.
The 6:1 planetary reduction transmission utilizes a fixed planet, sun drive and ring driven gear configuration. The planets ride on NSK ball bearings while the ring gear delivers the torque to the wheels.
The unique transmission allows the wheel center to rotate around the upright with the use of two high precision SilverThin 1/2" cross section angular contact ball bearings.
The custom student designed gears utilize a diametral pitch of 24, pitch angle of 20 degrees and 4140 steel nitrided and polished to increase the safety factor against beading and surface wear.
The gears were analysed using a student developed machine elements calculator in combination with finite element analysis and a highly specialized KISSsoft transmission design software.