Monday, November 29, 2010

The Hy-Bridget

Review of The Hy-Bridget concept from U.S.A. Motors.
By Dennis Mac Luggage
Car and Track Trends Magazine
April 2013

Amazingly after less than a year Sonny Sanders, deep pocket begetter of the exquisite Bridget Roadster, is at it again. Even before his original creation debuted to critical acclaim and solid sales numbers his merry band of tech rats were working on a concept vehicle based on the Bridget. It's uncertain if this new concept will be produced but if the public reception is enthusiastic enough, and if the price can be held to within spitting distance of the original sticker of the Bridget Roadster then it just might be in the cards.

The first odd thing about the Hy-Bridget is its looks--in that it looks exactly like a stock Roadster. Not a square inch of exterior sheet metal, trim, or interior appointment has been changed. The entire meat and guts of this concept are in the powertrain department and even there some parts, like the original engine, remain. It's a hybrid of course as indicated by the name but there is little resemblance mechanically to any other passenger car hybrid on the road today.

Sanders describes the vehicle as "an experiment rather than a concept". The object of the experiment was to find out if a hybrid powertrain could be developed and produced for nearly the same price as a conventional one without sacrificing performance, without increasing weight, and at the same time increasing fuel economy. He claims to have accomplished this feat, although instrumented testing on our part has yet to confirm it, but since every claim for the original was purely based in reality we question not, yet, these claims.

Hy-Bridget can perhaps be characterized more by what isn't there rather than what remains. What isn't there is a starter motor, flywheel, clutch, transmission, shifter, driveshaft, rear brakes, or any sign of the superlight but conventional solid axle from the original. What has replaced these parts is a 40HP 300amp generator plugged into the back of the engine, a "wheel motor" on each end of a simple alloy rear axle tube, and a small ultra-capacitor used for energy recovery. What else isn't there that is on a conventional hybrid is any sign of a main drive battery costing many thousands of dollars and weighing hundreds of pounds.

This is what as known as a "serial" hybrid design, similar in concept to that used in locomotives but rarely seen in the automotive world. Hy-Bridget makes no claims at all of having a consequential electric only range or any plug-in capability. Its standard engine and its diminutive fuel tank remain intact although the tuning of the engine is quite different. The engineering goal was to see if economy gains could be made without the weight of heavy batteries compromising performance or sending costs soaring.

Sanderson claims to have achieved all these goals and our brief test drive confirmed everything excepting the increase in fuel economy, and the price of course, but there is little reason to doubt him. The key is simplicity, of a sort that "conventional" hybrids can only dream. There's an engine, a generator, one electric motor for each rear wheel, and a 30 pound ultra-capacitor nestled into the still extant driveshaft tunnel. The big honking cap recovers energy as the car slows, assists for brief periods with acceleration, and in concert with the drivetrain management electronics serves as the rear axle's primary brakes. Pretty slick.

The use of wheel motors in concept vehicles is not new, they've been in development for well over a decade, but what makes them viable in this case is their small size--about 25 pounds each. Each "pancake" style rear wheel motor is rated at only 20 horsepower and 50 pound feet of torque--plenty for the needs of a Bridget. A wheel motor's inherent design provides mechanical advantage characteristics which obviate any need for gearing so full functionality and power is available from the motor at normal wheel rotational speeds. Needing only 25 horses and 50 lb/ft of torque puts these motors on the favorable side of the equation in terms of weight and cost. As such motors escalate to sizes and power levels needed by much larger vehicles prices skyrocket and unsprung weight becomes a major problem.

A weight of 25 pounds doesn't sound feathery but have you ever seen a conventional AC powered 25 horsepower motor in the flesh? Three strong guys would barely be able to move it. Pancake motors are very high tech and consequently expensive so even with the units replacing a lot of parts under the car it's a bit difficult to understand how U.S.A. motors could make the financial claims they touting. The similarly teched-up generator could only add to the price pressure. Once again have you ever seen a small light fifty horsepower generator? As they say about such things: Strong, light, cheap. Pick two.

Wheel motors definitely increase unsprung weight but in Hy-Bridget's case the problem is helped greatly by using the motors themselves as the main rear brakes. The HB's power management ensures that even if the ultra-cap cannot accept any more braking energy the rear brakes can have reverse polarity power applied to them to slow things down. If for some reason the engine fails completely and the cap is completely discharged the front brakes are plenty capable of slowing the car in a safe manner--they aren't power boosted if you recall so they need no additional help except for a decently healthy leg.

The Hy-Bridget's engine is identical to the Bridget Roadster's but it has been tuned to deliver about 20 fewer horsepower at a mere 4000 rpm but an identical 100 pound feet of peak torque. These 20 fewer horsies slow the Hy-Bridget's top speed to about 95 mph which although around 10 mph slower than its sister still feels like about 200 with the top down. The system takes little away from the Bridget's driving joys. No lag in power delivery. The engine spools up quickly enough but with its table flat torque curve it hardly needs to. Acceleration feels very similar to the BR with throttle response that is more than adequate, if slightly less than stellar. Handing dynamics are indistinguishable from the BR as well thank goodness. We didn't bring our bathroom scales with us on the test drive but the car feels no heavier even if it has the slightest touch more understeer than its sister. All in all the chassis tuning is succesfull in replicating that ineffable Bridget handling goodness.

The dash is almost unchanged as well. Still the same gauges since the engine still needs them but they reflect the changed operating conditions of the power train. No dash indication of the electrics is present nor is it really needed since there is no expensive persnickety battery to baby sit. There is a fault light for the ultra-cap since it is so involved with braking but even if it toasts itself the car is plenty drivable enough to get to you home provided you aren't sluicing down into Denver from the Eisenhower Tunnel. The front brakes alone could probably handle things but a long descent without electrical braking will mean one seriously fatigued extremity and probably some toasted brake pads. On the upside is that this configuration allows full authority traction control under all circumstances and significantly expands the Bridget's rather limited winter weather repertoire. There's no shifter of course and a keyed column and a button for forward and another for reverse take its place. Power management software allegedly assures that if the reverse button is hit at high forward speed nothing will be damaged. I was not brave enough to try it.

In short the Hy-Bridget "experiment" exhibits virtually the same driving experience as its conventional sister with the exception of a lower top speed. So little has been lost but has anything been really gained? Hard to say really for the light weight of the Bridget puts it in a class of its own in the automotive world. Try to translate such a powertrain to a car weighing twice as much or more and developing three or more times as much power and the cost/weight curves will climb like a P-51 Mustang at full throttle. A biggish battery is needed in most cases for typically sized hybrids or fuel economy gains will be elusive. Add to that the fact that a high-tech 40 horse generator is no heavier than the Bridget's starter/flywheel/transmission combo whereas a 150 or 200 HP generator is a whole other heavy as hell kettle of fish. Diminishing returns rapidly rear their unlovely heads in packages much heavier than a Bridget so one is unlikely to encounter a similar system in 6000 pound SUV.

CEO Sanderson swears that the car can be built for close to the BR's price but are the projected fuel economy gains worth the trouble? Sanderson is claiming a 60 mpg city rating and a 50 mpg highway rating which are impressive numbers even these days. This amounts to a 50 percent better city rating but only about a 5 mpg better highway rating. In my estimation the experiment has been a success operationally but since the genny Bridget already is a fuel miser the gains from the new powertrain will not make a big difference in operating costs and the maintenance costs may well be higher depending on the reliability of the electrical hardware. If your driving is mostly city based, that is out of the Bridget's natural element, then the mileage will definitely save dough and your range will be stellar. If you use Bridget as she is intended, scooting through curvy countryside, then you'd probably pass on the amped up version. One of each would be nice though and you could buy both for less than most current hybrids cost and instead of twice the fun you'd get four times as much.

So I count the experiment a success while questioning any real need for production but that of course is up to Mr. Sanderson. No matter. As long as the original Mz. Bridget continues to be produced he can build nitromethane powered skateboards for all I care.

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