PowerWheels 2014 Drivetrain Ideas

Brushless DC Motor

Stuff To Know

• Total power consumption must be 1440 Watts or less:
  • 36v = 40A Fuse (Digikey #F3089-ND)
  • 28.8v = 50A Fuse (Digikey #F3090-ND)
  • 24v = 60A Fuse (Digikey #F3091-ND)
  • 12v = 125A Fuse (Digikey #F1879-ND)
• Motor Controller is required.
• Size limit: 62” long x 36” wide x 72" high (including driver).
  • Seat height may not be lower than the axle height.

RC

• Repurpose outrunner brushless DC hobbyist motor for car/boat
• Overview of this technique for scooters
• Requires motor (2 motors?) and motor controller
• One recommended part supplier

Advantages

• Definitely the best weight/performance/efficiency ratio

Disadvantages

• Not as straightforward electrically
• Overkill?
• More expensive than hacky solutions ($200ish) (However people in town may have parts for us?)
• Less known about how to do this
• Tend to be fast RPMs so big amount of gearing down

Washing machine

This is the same idea as the RC motor except that we repurpose a washing machine motor instead

Advantages

• These motors and big and cool looking. We will look totally rad
• Unique, innovative

Disadvantages

• What voltage do these run on? Likely we will need to rewind coils?
• Motor controller might not work out-of-the-box. (What do we do, set for "spin cycle?") We have to make our own or hope for the best for a commercial unit?

Hydrostat

• Use 12V pump from Harbor Freight ($30ish each) to pump oil to turbine

Power Steering Pump as Turbine

• Needs to be vane pump. Most but not all PS pumps are vane. Disassembly Video
• Pumps available from salvage years for $20ish. Some (Don Schmid: $22) are pick/pull and some (A-plus: $20ish) are not.
• Vanes in PS pump fly out from centrifugal force.
• Must use lubricating liquid

Advantages

• Innovative/unique
• Could be cool to use transparent pipes plumbed all over the place so people can see the hydraulic action. Put glittery stuff inside the fluid
• CVT Transmission!

Disadvantages

• Getting the balance between pressure and displacement of liquid likely to be tricky
• Extra weight/parts that are totally unnecessary
• Efficiency? Likely low
• Only 1 example found of using a PS pump as a turbine (MIT project) and that example was a report and not explained in detail.
• Not much reference in using vane pumps in general as turbines. Does this mean it's a bad idea?

Tesla Turbine

Advantages

• Seems cool/innovative

Disadvantages

• Make our own?

Wheelchair System

• Use 2 motors from one of the 3 wheelchairs we already have.
• Use the intended motor controller for the wheelchair
• Re-gear the motor for more speed and less torque

Advantages

• Might be the easiest/cheapest way to go, since we already have motors and a motor controller

Disadvantages

• These motors are built for battery efficiency over hours and not for speed. Are they strong enough? Will they be fast?

Traditional Scooter Motors

• Use a couple of traditional permanent-magnet scooter motors

Advantages

• This is the standard solution used by most other teams. It's tried, tested, and works. If we want to be absolutely sure that we won't be laughed off the track, this is safe.

Disadvantages

• Doesn't really take advantage of the parts we happen to have on-hand
• Not as fun a solution as others?

Bicycle Components

With any of the above solutions, we will likely need to gear down or gear up. Bicycle components may be a way to do this

• Use crank/sprocket/derailleur with bicycle wheel to get the right gearing
• With wheelchair motors we could attach large gear from crank to motor shaft. There are good ideas on Instructables about how to do this.
• Scooter motor distributors sell small gears that fit on motor shafts which are compatible with bicycle chains.

Advantages

• Takes advantage of parts that we probably already have around. A super cheap way to go
• Easily change gear ratios so we can find the best combination without knowing what we are doing. :-)
• Bicycle repair workshop on Sat might be a way to fuel this idea further and get parts

Disadvantages

• Thin tires. Could this cause traction problems?
• With wheelchair we would be gearing down then gearing up. Not very efficient?
• Slightly less efficient than a direct-drive solution