So, what feature provides the "maxi" in a "maxi traction" streetcar?

For a 4 axle trolley with 2 motors, the maximum traction truck put more weight on the power axle improving its traction compared to the balanced weight distribution in a conventional truck in a 4 motor car.

The Maximum Traction truck has a small, non-powered, pony wheel set and a much larger drive wheel set which is powered by a single large traction motor..
As previously stated, this puts more weight on the driven axle, hence "maximum traction"

...and as most museum members which operate Max Trac cars know, the name is a misnomer. The pony wheels have a propensity to come off on curves.

Maximum Traction cars were used in regular service in Ballarat and Bendigo in Victoria, Australia until closure in 1971/72. They were on secondhand trams which the operator purchased from Melbourne in the late 40s, and were suitable for the provincial city operations of these places. The Brill 22E trucks are a sight to behold.

Cheers,
Matt

If you search the term in google books, many era resources will emerge. The Max Trac apparently was only safe for lower speed operations, and had significant issues with noise and braking (due to the different wheel-sizes)...

Not only was the power wheel larger, but the bolster was offset to put much more weight on the motor end of the truck. A modern New Orleans trolley with 8 equal sized wheels, symmetrical bolsters, and only 2 motors should be more slippery than a Maximum Traction car of the same weight. For even more traction and complexity, try the 6 wheel, 2 motor Robinson Radial single truck!

Here's a picture of a car with maximum traction trucks: http://www.tmny.org/catl.php?n=84&d=none&c=BRT+DR+MT+trolley+No.+3300 You can see the difference in the wheels and the offset appearance of the trucks.

Need a better look of the trucks? This may help.

That's also the more common arrangement, with the little wheels tucked under the platform knees, allowing lower platforms (and therefore faster boarding). The BRT car shown earlier has the somewhat unusual arrangement with the motors toward the ends of the car, but then that car also has very short platforms, for a streetcar.

Typical cock n' bull investigation story. The second news item on the Shorpy page states that the investigation at the scene showed the brakes to be "locked". Unfortunately, the photo shows the brake piston to be retracted. Not that it mattered, as with the body off the trucks the rodding is likely pulling the shoes against the wheels, but that says nothing of the condition that existed before the body left the trucks. It appears that investigations tended to be whitewashes back in 1919, too.

To see "Maximum Traction" trucks close-up, there are several cars preserved with these "bogies". Orange Empire in Perris, CA has Hill of Howth #2, a double-deck tram from Ireland. It hasn't run for quite a while, but it was often operated during Rail Festivals in the 1990's. It normally ran on the south end of the main line, where its leisurely pace would not affect other operations. For several years we had a young woman playing a bagpipe on the upper deck, adding to the Celtic atmosphere. #2 is currently stored in Barn 4, along with Pacific Electric and main line railroad cars.
A "Maximum Traction" equipped car that's currently in service is Dallas 434 at Seashore, a Stone and Webster "turtleback" streetcar. I think Seashore has some other "Maxi's" and there may be some at Baltimore. Here's a question: was "Maximum Traction" a Brill trademark name?

This YouTube video may be of interest;

http://www.youtube.com/watch?v=cKvdR0wQT0U

It shows Prahran & Malvern Tramways Trust maximum traction car No44 in Melbourne, Australia. This weekend just gone was the one hundredth anniversary of the opening of the P&MTT tram depot/carbarn at Malvern in suburban Melbourne.

For the occasion, two ex-P&MTT cars were brought to Melbourne from Bendigo where they have been restored in recent years. No84 was restored especially for this celebration. No44 rides on Brill 22E maximum-traction trucks.

As I mentioned above, the Melbourne & Metropolitan Tramways Board (which was set up to bring all of the municapal and private operators in Melbourne under a single authority) sold Melbourne cars to the operators of the Bendigo, Ballarat and Geelong tramways once they were no longer needed in Melbourne. These three systems were small provincial operations so single-truck cars and two-motor bogie cars were quite sufficient. Also, six of Australia's eight Birney cars were used in Geelong and then Bendigo.

So the ex-Mebourne max-trac cars saw use in the three systems until Geelong closed in 1956, while Ballarat closed in 1971 and Bendigo in 1972. A large part of the Bendigo system was turned into a tourist tramway and a small section of the Ballarat system survives also.

All of the cars which were at Bendigo at closure are still there and many have been returned to earlier condition, such as 44 and 84 in the above video.

Cheers,
Matt

Baltimore has 3 cars with Maximum Traction Trucks. We have 2 pair of Brill 22E, and a Baltimore Car Wheel Co. version. The Baltimore Car Wheel version has a bolster and kingpin arrangement like most trucks, the 22E truck has no bolster or kingpin, and "floats" on bearing surfaces. Both work fine if provided with adequate lubrication.

That's not the only way to lock brakes on a streetcar. Another is for a part of the brake linkage to get snagged on something stationary, and pull really hard on the rest of the brake linkage, causing a very hard brake application on all or some axles.

Another factor is that some brake linkages on older cars started on the carbody but terminated on the truck. That meant brake applications provided rather considerable force between carbody and truck. A snagging of brake rigging could cause extremely high forces between truck and carbody - enough to tear the car off the truck? I don't know but I do find it plausible.