MTSU Students Retrofit Hub Motors (Converting an Accord into a plug-in Hybrid)

[Otto]

Originally Posted by serialk11r

I don't consider replacing the brake simplicity, because that involves making a rather specific hub motor for every car. Besides, reduced braking function on the rear wheels is quite a large compromise, that I think sensible people would consider unacceptable. Weight transfer may leave the rear axle with perhaps under 40% of the weight for taller vehicles, but the hub motor is never going to be able to apply enough torque to lock the wheels even in that case. Losing even 20% of braking capacity is huge. And on RWD cars (I know I know, most people here think RWD is stupid or something), you absolutely cannot replace the brake because the front does more braking.

Many cars aren't coming with drum brakes anyhow, because they suck. The secondary drum brakes used for the handbrake are not going to suffice either. Heck, the Honda Accord (current one at least) has rear disk brakes.

Even if braking performance weren't an issue, is embedding the motor armature into a new "brake" hub really easier than just bolting a motor to the spindle and using gears?

Could easily insert the permanent magnets into the slots of a double-wall disk brake, and use the existing caliper mounting to support the fixed electromagnet assy. Braking loads being greater than acceleration loads, these structures are already more than adequate strength.

Still better to put the permanent magnets on the wheel itself, with the electromagnets fixed to the strut with a ring bracket. Bolting on a motor at the spindle is needlessly heavy, and applies the torque at the worst possible location--the hub.

Dump the entire stock drivetrain, fuel, muffler, radiator, etc. and go to 4 wheel electric drive, electronically controlled. Maybe have onboard aux power unit in form of a lightweight diesel generator to keep the batteries topped off and have regenerative braking, reducing the number and weight of batteries needed. Having saved the weight of the combined conventional driveline/fuel/transmission, etc., the car is now much lighter, some of which weight is replaced by the new batteries, etc.. If overall final weight is reduced, brakes can be reduced accordingly since now they bear a smaller load. Also the car structure itself, which now carrying a lighter load, needs less strength and attendant weight to be sufficient.

[freebeard]

If overall final weight is reduced, brakes can be reduced accordingly since now they bear a smaller load. Also the car structure itself, which now carrying a lighter load, needs less strength and attendant weight to be sufficient.

Once you head down that path, you just use 1—4 sets of pedals and dump the APU.

Oh, and this:
New Wood Pulp Concoction Stronger Than Kevlar, Carbon Fiber | Autopia | Wired.com

[Mr. Previa]

Fantastic idea. Awesome job!

[Otto]

Originally Posted by freebeard

Once you head down that path, you just use 1—4 sets of pedals and dump the APU.

Oh, and this:
New Wood Pulp Concoction Stronger Than Kevlar, Carbon Fiber | Autopia | Wired.com

Thanks mucho, Freebeard, that helps a bunch. I just finished a class on advanced composites, with emphasis on vacuum infusion and carbon fiber. Unfortunately, carbon fiber is expensive, labor intensive, and error prone on application. It does not like to wet out as well as other composites, so the selection of resins is somewhat more limited and expensive. It's also somewhat fragile and brittle, and can shatter on impact, so its lack of toughness means it needs Kevlar or other such facing to protect the ride in, say, a streamliner recumbent bike. (Shards of carbon fiber could be dangerous when the bike falls over, trapping the rider in a sort of cheese grater.)

I'm very curious about this new wood pulp composite, especially which particular wood.

Some types of wood have much better fatigue strength than metals. Stiffness and fatigue strength are what engineers must design around, since we don't want the car to break when the metal gives out, so more metal is put in on construction, to offset and prevent the anticipated failure. In other words, much of the metal is dead weight.

Bamboo (esp. stronger varieties such as Tonkin, used for fishing poles) is said to have nearly the stiffness of carbon fiber, is tougher, vastly cheaper, and is excellent as a vibration dampener, so would make a quiet riding vehicle. Bamboo is actually a grass, and grows vastly faster than wood, sometimes several feet per day, and is much more environmentally useful than hardwoods, metals, or composites. It's stronger than oak and harder than maple, hence its growing popularity for flooring. Has natural antibiotics to resist jungle rot, etc..

I wonder about using bamboo leaves (being flat) for oriented strand board, which might be steam/pressure formed into compound curved parts.

Bamboo can be steamed or heated and bent somewhat. YouTube for it.

Hemp fibers are also a good candidate for composite structures, very tough and strong, and very cheap. Henry Ford is said to have tried hemp composite for use as car fenders in the 1920s or '30s, of course rust proof, and pretty tough and comparatively impact resistant.

[freebeard]

Happy to help. You don't have to sell me on bamboo and hemp.
- Bamboo Workshop Gallery

Calfee seems to be the leader in bike frames:
http://www.calfeedesign.com/products/bamboo/

And there're a lot of varieties:
- Bamboo Flora Gallery

I'm curious about the 70% of the cellulose that isn't nanocrystals (pollution) and the acids involved.

Sounds like a fun class. Did you do a project?

[serialk11r]

Originally Posted by Otto

[/B]

Could easily insert the permanent magnets into the slots of a double-wall disk brake, and use the existing caliper mounting to support the fixed electromagnet assy. Braking loads being greater than acceleration loads, these structures are already more than adequate strength.

Still better to put the permanent magnets on the wheel itself, with the electromagnets fixed to the strut with a ring bracket. Bolting on a motor at the spindle is needlessly heavy, and applies the torque at the worst possible location--the hub.

Not sure that would work, brake rotor temperatures can easily exceed the Curie temperature of the magnet, and I imagine the reduced induction of the coils could fry something somewhere.

In case it wasn't clear, I was talking about bolting a motor to the spindle that applies torque directly to the rim.

[Otto]

I wish the class had gone farther, with emphasis on cost vs. strength and stiffness of various choices, etc.. Also, I wish they'd included at least perfunctory information on new technologies such as 3D printing, graphene, nano tubes, and now this wood byproduct. We did basic projects including vacuum infusion into molds, such as skate boards and longboards, as well as a 12' dory. Visited some aerospace companies on field trips, where they make jet engine nacelles, flaps and ailerons, etc.. I also wanted to explore alternate methods of fabrication, i.e., how to make stuff cheaper but of equivalent strength. F'rex, use 5 cent/square foot plastic shower curtain as re-usable sheet for vacuum bagging vs. one-time use of 15 cent/square foot stuff. Or, autoclave out of household materials. Also considered making a recumbent bicycle out of a ~4" thick piece of bamboo with composite fittings, and see how that might compare with store-bought 'bents of carbon fiber.

Anyhow, I'm convinced that starting with a clean piece of paper and using some new ideas (esp. if the wood products composites pan out as hoped), one could build a 2 seat sports car of ~<1,000 lbs. and be very fuel efficient, including electric propulsion based on that discussed in this thread. The MTSU motors have ~200 ft. lbs. of torque per Prof. Perry, who says his battery and control pack will be about the size of an airline carry-on bag. If so, dump the whole conventional propulsion system, go with upgraded MTSU version with regen braking, applied to a very light but aero efficient car.

PS: I suspect the remote control model airplane crowd is miles ahead of anybody else not paid by the Pentagon, and has found ways to get more bang for the buck. Worth monitoring.

[Otto]

Originally Posted by serialk11r

Not sure that would work, brake rotor temperatures can easily exceed the Curie temperature of the magnet, and I imagine the reduced induction of the coils could fry something somewhere.

In case it wasn't clear, I was talking about bolting a motor to the spindle that applies torque directly to the rim.

Maybe so, so the best place to put the magnets from a temperature and torque standpoint would be on the wheel itself, out as close as practical to the rim. Rather than bolt a motor to the spindle, the wheel is the motor.

Wheel weight would grow by only the weight of the magnets. Given lower vehicle weight upon dumping the whole conventional drivetrain and associated gear, the wheels would be carrying less load and stress, so could be machined to thinner wall thickness, perhaps with less overall weight including magnets than before. The brake caliper hardware could carry the loads of the ring of electro-magnets, which in the MTSU video don't look all that heavy. At least one wheel motor proposed for car use has eliminated the brakes entirely, relying on its magnets to both regen and brake. If so, such a wheel motor might weigh less than the unsprung weight on your car right now. Interesting to learn more, though.....

[freebeard]

Anyhow, I'm convinced that starting with a clean piece of paper and using some new ideas (esp. if the wood products composites pan out as hoped), one could build a 2 seat sports car of ~<1,000 lbs. and be very fuel efficient, including electric propulsion based on that discussed in this thread.

Not the design I went looking for (bamboo in torsion for the suspension) but it will do:

Ajiro Bamboo Velobike: A "Grown Vehicle" That's Farmed, Not Factory-Made : TreeHugger
Mixing spoked and hubless wheels is like wearing stripes and plaid.

PS: I suspect the remote control model airplane crowd is miles ahead of anybody else

Tell me about it:

http://www.youtube.com/watch?v=CjBm7iUeVl4

[Otto]

Just replaced the brake pads on my BMW 325is, and while in there I spent some time looking around and imagineering: I'm convinced that especially with both regen braking and anti-lock braking circuitry, rpm and torque management is quite feasible. Conventional brakes as drums or disks and callipers could be eliminated entirely, saving lots of unsprung wheel weight and reducing the energy previously needed to accelerate and decelerate the wheel. This, coupled with the reduced loads on the wheel itself meaning the wheel could be much lighter due to reduced wall thickness, mean that a wheel motor could be vastly lighter than a conventional wheel. No brake caliper, line, drum or disk would be needed. Such a lightened load means a thinner and lighter spindle, too, as well as a lighter spring.

What about air shocks and springs? I was at a tire shop today and noticed air bladder shocks/springs used for auxiliary dampening on trucks, etc.. Why couldn't the conventional metal spring/shock/strut assembly be replaced by an air shock/spring? Lighter, never wears out since it's just air inside, and adjustable via internal pressure. Anybody here have insight to share about how well air shocks/springs work, their merits and demerits?

Combined with lighter wheel motors, air shocks/springs could mean major reductions in weight.

Thoughts?