What are traction motors?

3rdrail wrote:Did the industry dislike, distrust, or not be familiar with electric, or be concerned about safety concerns ?

I'm going to say it's a bit of that, AND the fact that until the 1950's, you needed either a DC system - and 3kv requires lots of substations and is constrained anyway - or AC at 25hz, an oddity even then.

Had the practical rectifier locomotive come about in the mid 1930's instead of the early 1950's, I suspect things would look VERY different today in the US. Even electric was a financial godsend Vs steam, but once you factored in a 25hz power system, it wasn't. EMD and Alco had useful diesels ready to go in 1946, GE and Westinghouse had nice electrics - if you were 3kv DC or 25hz AC. Even into the 50's though, the industry spoke of diesel as a stop-gap measure, and at least some believe electrification was coming soon. By the 70's, it became cost, and these days, I frankly believe that it's more "not invented here" than anything else. US railroads these days are on the trailing end of any innovation, and seem to want to stay that way, for whatever reason...

Hi Nasadowsk - thanks for that super explanation. (I don't know why it by-passed my email. I just found it now by scanning.) That certainly answers a lot of questions. Electrification fascinates me. It is my main focus (traction) regarding my hobby. May I ask you what made the difference in Europe, which seems to be exactly the opposite in that their focus is, and has been, electric motors ? Thanks again.

3rdrail wrote: May I ask you what made the difference in Europe, which seems to be exactly the opposite in that their focus is, and has been, electric motors ?

It varies by country. These days, France can justify it with the buckets of cheap nuclear power they've got (they export electricity to everyone, even the UK). Switzerland has lots of hydro - always cheap - and lots of nuke. Most of the systems are smaller and more dense, leading to higher traffic volumes, which always favors electrics. Plus, historically the Europeans were not good at diesel locomotive development, and WWII interrupted everything.

As speeds increased, electrics became popular, even though multi-system ones are NOT an easy thing - most multi system locomotives have 4 pantographs on the roof - one for each system and no backups.

The flip side: There's plenty of differences between countries, and even in country - France has two voltages and two pantograph standards, Germany has a totally different one, Italy's is different, etc. Nobody shares the same cab signal systems either.

The stupid thing is, the US is ripe for standarized cab signalling / PTC and electrification standards. We're starting from scratch and they aren't. But, look how the industry's gone with PTC. At least 12.5kv / 25kv 60hz will dominate...

while im sure that info is credible, and makes sense, can someone explain what nasadowsk just said.. w/o the fancy terms.. sorry i may seem slow here.. just want to understand, haha tks!

slrr1 wrote:while im sure that info is credible, and makes sense, can someone explain what nasadowsk just said.. w/o the fancy terms.. sorry i may seem slow here.. just want to understand, haha tks!

Hmm.

Ok:

France has nuclear power, so electricity's cheap. Switzerland has dams, so power's cheap. But their trains use different electric systems, so they can't run over each other's tracks unless they have locomotives designed for both, and it's enough of a mess that the roof looks cluttered from all the equipment And France can't make up it's mind what it wants.

Oh, and European diesels have traditionally sucked. Actually, that's being real harsh, but they've always been a LOT better at electrics.

I'm not kidding, either, France literally has two voltages they use, and each system requires a different pickup design. That's partly why they developed that funny bent arm pantograph - to fit an extra few on the roof.

so what you are saying that it is not universal in europe as it is here in America.. 6 in one, a half dozen in the other... I see.. TY for clarifying..

Me thinks we is way off topic , no ?

no.. we are discussing why certain powers are used for traction motors.. explaining traction motors.. Jez everyone is wicked
obsessed with "staying on topic"!

slrr1 wrote:no.. we are discussing why certain powers are used for traction motors.. explaining traction motors.. Jez everyone is wicked
obsessed with "staying on topic"!

The topic is traction motors, let's make sure we stay close to topic, ok?

Maybe someone can clear up a puzzle in my mind. I took these shots in 1977 at the Orient Heights Car House. The trucks that you see are from 1923 Pullman East Boston Tunnel Cars (subway cars) which run on third rail or catenary via pantograph. The question that I have is that in the shot of the truck which has been removed, you can see the gears on the axle where the traction motor drives the axle along with a buffed area on both ends of the axle - one next to the gears and the other, next to a hub of some kind on the opposite side. However, in the other photo of a truck mounted underneath the car, you can see that this same area appears to be exposed. I thought that the traction motors would be attached to the trucks covering this area, no ? Am I seeing a truck that has had it's traction motor removed ? (This mounted truck photo was taken in the yards outside.)

Moderator's Note: Images size reduced to save rr.net bandwith, 10-25-09, 4:10 AM CDT

Looks like the motor's been removed

Look at Dutch's post on the first page, with the yellow traction motor. To the left of the pinion gear is an opening, with a support bearing inside. There is another support bearing at the other end of the motor.
The axle goes through these support bearings, keeping the gears correctly meshed. The other end of the motor is supported by a spring pack, up against the bolster.

On the subway car photos, there are two shiny spots on the axle, one next to the bull gear on the right, the other next to the "hub". Those shiny spots are where the support bearings contact the axle. The 'hub" is most likely some sort of thrust bearing or stop to keep the motor from shifting left. It appears that the subway motor is not as long as a locomotive TM, which takes up the full width between the backs of the wheels.

It would be useful if someone were to post a photo of a traction motor and wheelset "combo", assembled and complete with gearcases. Normally those gears are not seen outside the shop. And what an interesting wheel profile, to say the least.

Check this out: (1974) Is this merely "dynamic braking" for a subway car ?
http://books.google.com/books?id=VWTF3m ... q=&f=false

Subway Car typical truck

AC motors have several advantages over DC. As others said, they are far simpler to build and maintain; just check the bearings every so often. They are also lighter and smaller than a similar horsepower DC unit.

But AC motors of this ilk are single-speed devices. You think that is a dealkiller, but....

That speed is a function of the frequency of the AC feeding it. So the magic is: the "throttle" is in fact a frequency control, almost akin to a trombone slide. To go faster, raise the power frequency; slower, lower it. It's only in the last 10-20 years that the needed good, high-power semiconductors capable of transit/locomotive loads have come into play in the marketplace.

Further, AC motors integrate well with traction control. Traction control is basically slipping wheel detection, which then briefly cuts the power to that motor until it stops slipping. That way, the system can apply maximum power to each wheelset.