I'm referring to Positive Traction Control which was developed back in the early 70s by CN. It has been described as "electrical side rods for diesels", in effect PTC made high horsepower on 4 axles a viable proposition. Prior to PTC, high horsepower locomotives like the GP40 were slippery, and that's primarily why CN never purchased more than 16 or so. It's probably also why the SD40-2 sold so well relative to its four motor counterpart on other roads.
CN had discovered that the SD40's long wheelbase truck was hard on the railway's curves (especially in northern Ontario and Quebec),and that's why they set out to develop PTC.. which in conjunction with GMD resulted in North America's largest roster of GP40-2 locomotves by the late 70s.
What I find interesting about this story is that CN invented PTC and then went to GMD with it. Subsequently all high horsepowered locomotives (and probably all six motored engines too) were built with PTC, thanks in large part to one railroad's R&D efforts. The same can be said for the safety cab (now called the North American cab). No new regulations called for a stronger, better cab, it came about entirely due to CN's initiative in improving crew comfort, safety, and productivity. More proof that perhaps government ownership and initiative/leadership aren't mutually exclusive.
I suspect EMD and the late Dr. Bruce R. Meyer, PhD, might have a different 'take' on this, as they developed the "Super Series" limited-slip / 'creep' type wheel slip control for the 50-Series and later locomotives. See, for example:
"Wheel Slip Control on NS SD60I's - Question" (yes, I started the thread about 5+ years ago):
http://cs.trains.com/trn/f/741/t/164145.aspx
http://trid.trb.org/view.aspx?id=157477
http://www.railroad.net/forums/viewtopic.php?f=6&t=26741
http://mycommunity.theiet.org/communities/discussions/viewtopic/69/118/16253#.VNpOLU10y70
Brian Solomon's book "GE and EMD Locomotives" says on pg. 300 (bottom right) that the Super Series wheel slip control was developed from technology licensed from the Swedish firm ASEA and applied to experimental units in the late 1970's.
- Paul North.
And here I thought the other PTC was the "Philadelphia Transportation Company" which operated so many of the trolleys I grew up watching and riding. Or perhaps the "Pennsylvania Turnpike Commission" who I have paid tolls for the "honor" of using their roads.
CN's PTC would have preceded Bruce Meyers' contribution by at least a couple of years as all of CN's GP40-2s were built between 1974 and 1976 and were equipped with PTC. I'm not sure if Bruce Meyer improved on PTC or if his work solved the same problem in a different manner. An electrical engineer could probably clarify that point.
EMD was testing 'Super Series' in the mid 70's. EMD discovered that a little positive wheel slip enhanced traction. The advent of affordable ground radar on a locomotive allowed this. It became an option in late 'Dash 2' production and BN even took delivery of an order of SD40-2's with the 'SS' feature. It became 'standard' on the '50 Series' line of locomotives. The initial work was done in the early 70's(1974 comes to mind). EMD was doing testing on the Milw 'Short Line' between St Paul and Mpls with a 4200 hp test SD45X, The center traction motors were cut out and a ground radar unit was installed. A test run up the hill was made for a benchmark, and then tests were run while dialing in wheel slip. The expectation was that the TE would drop, but it improved. After discussions by the engineering types, they realized that the positive wheel slip 'heated' the contact patch between the wheel and the rail - Thus the sticky patch improved adhesion.
Several 'after-market' PTC kits by several vendors were produced to improve older locomotive performance. I seem to remember DRGW and WC Ltd were big users of PTC upgrade kits'.
Starting with the SD45, EMD offered IDAC(Individual Correction And Control). IIRC, this was standard on the SD45, and an option on the rest of the '40 Line'. This became standard on the 'Dash 2' Line. This was not PTC, but a 1st real attempt by EMD at correcting wheel slip at the time.
If there are connections to the CN PTC and EMD SS traction control, I have not seen and notes.
Jim
Modeling BNSF and Milwaukee Road in SW Wisconsin
Interesting, so was PTC a precursor to SS?
I don't think so. EMD just had a different way of doing it. GE never did and even today doesn't even use a true ground speed sensor or radar gun like EMD does. All of the other traction controls I know of do NOT use radar.
The early EMD radar engines including the SD50s were crap in my opinion. It really took a processor like the MOD1 to make it work.
The CN engines were clever , I think the components were actually built by one of the predecessor company of Q Tron . Later Q Tron went on to build terriffic equipment that the WC used for traction enhancements.
There is quite a list of micro's that came out in the 80's and 90's to add to existing locomotive fleets.
Woodward
Quantum
OTP
Pulse
and a few others.
Randy
Good Question! I looked through my slides and it was the fall of 1973 I took pictures of the SD45X 5740 with the ET800 test car. Small mobile 'industrial strength' ground radar units that could be truck mounted were just arriving on the scene. Being able to measure the actual ground speed vs the wheel rotation is the key to these systems. Size and cost were declining in the early 70's.
Conrail tried PTC on the four ex-RDG GP40-2s. Did it work? Yes. Did Conrail need what it did? No.
-Don (Random stuff, mostly about trains - what else? http://blerfblog.blogspot.com/)
Randy StahlI don't think so. EMD just had a different way of doing it. GE never did and even today doesn't even use a true ground speed sensor or radar gun like EMD does. All of the other traction controls I know of do NOT use radar. The early EMD radar engines including the SD50s were crap in my opinion. It really took a processor like the MOD1 to make it work.
Both EMD and GE (and PTC) played a current maximization game. Give it more juice until the current starts to back off and motor speed comes up. That means you're past the peak adhesion.
EMD's radar was there to be able to put a limit on the amount of creep. Problem was when the radar couldn't or wouldn't read ground speed, the whole system defaulted back to WS10 performance.
GE just didn't care about ground speed. They would just compare motor speed from all the axles and limit speed differential.
CN's GP40s were among the locomotives built without IDAC(Instaneous Detection And Correction) wheelslip control. Pre-1965 locomotives of all builders had very primitive wheelslip conntrol systems. EMD developed the IDAC system to improve the system in order to make the SD45 a viable locomotive with its relatively high horsepower per axle. However for all their other models it was an extra-cost option. The GP40s in particular could have used the same system from the start. Most railroad companies did not wnat to pay for the system on their early GP40 and SD40 locomotives. They soon found out that they needed something better than the standard system. CN went their own way and developed the PTC system. EMD made the IDAC system standard on all their road locomtives in late 1967 or early 1968. As far as I am aware the railroads retrofitted the system to all the unequipped GP40 and SD40 locomotives eventually. With the inauguration of the Dash-2 series the IDAC system became the card based WS-10 system. Besides CN only D&RGW had locomotives equipped with PTC, as D&RGW chose to retrofit their SD40T-2 locomotives with the system in order that they could develop similar Continuous Tractive Effort to their SD50 locomotives. Since then many companies have developed microprocessor based systems that include wheelslip control as well as engine controls. Wabtec, ZTR systems, Quantum, and Woodward. The Woodward has left the market, and the few locomotives equipped with their system have been scrapped or converted to somebody elses system. EMD's Super Series and the GE equivilent are the best North American systems currently. As far as I am aware no North American railroad has ordered any new locomotive with a system other than that supplied by they locomotive builder in many years, probably since the last CN Dash-2 locomotive.
The GE system is called Sentry, FWIW.
Late Dash 7s generally had CHEC (Constant Horsepower Excitation Control) excitation and Sentry wheelslip systems
The Sentry system wasn't that great. Most of the late dash 7's I've been around had Chec and CMR. Sentry had ALOT of parts. At least Sentry did get rid of the mercury switches though
Dash 8s had microprocessor emulation of CHEC and Sentry. microCHEC and microSentry. Worked pretty well. TM speed sensor probes were a great idea - better than axle alternators.
CMR was pretty similar to IDAC/WS10 in that it just looked at motor current and cut back excitation when they were not roughly equal.
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