So, with the F40 thread and the Hybrid thread and a couple other threads all talking about the weight problems with classic framed modern passenger power, I've been wondering, why was the A1A wheel arrangment dropped? Wouldn't it have been cheaper engineering to simply use A1A trucks with a proven design rather then the added cost of the AMD-103 design? Why doesn't MPI look at A1A to counteract it's wheight problems? or the F59PHI?
With A1A you could fit larger engines and HEP generators, you would have better ride characteristics, You could run on lighter track. What's the downside?
I mean sure the old Bloomberg A1A bogey is a little long in the tooth, but there are Still bloomberg B and Flexcoil trucks out there and I would think that bringing it into the modern world would be way lower cost then what the Genesis was.
For that matter, why wasn't A1A considered for the GP60Ms?
I think a combination of cost, an increase in allowable axle loads and an increase in diesel engine output all did in the A1A truck. You don't want to have to maintain an extra pair of wheelsets if you don't have to.
The Genesis design is a good example of how you can build a modern passenger locomotive with good ride quality and packaging on 4 axle trucks.
-Don (Random stuff, mostly about trains - what else? http://blerfblog.blogspot.com/)
"I Often Dream of Trains"-From the Album of the Same Name by Robyn Hitchcock
oltmannd wrote: I think a combination of cost, an increase in allowable axle loads and an increase in diesel engine output all did in the A1A truck. You don't want to have to maintain an extra pair of wheelsets if you don't have to.
Especially if that extra pair of wheelsets is just along for the ride.
Dan
Sure, but how much additional maintence do those trucks really entail? And sure, the genesis is a marvel of engineering, sure, but was it worth the cost in engineering when a more stock design riding on A1As would have been as effective? remember Amtrak's always being squeezed for money so every dime of expense is fought for. Given that Alaska got the 70 MAC with convertable trucks, it seems like it wouldn't have been an impossibility.
But even beyond the Genesis, what of MPI? They're having weight issues with the MPExpress. Couldn't the A1A truck have allowed them more room to play with to get a better performing engine? Why design something less optimal just to use a 4-axle truck?
MPI may have had weight issues with the MPExpress suburban locomotives, but an A1A truck would have become a cost issue. It would be a non-standard (expensive) design and would have required a totally different frame to allow for the longer wheelbase.
Those equalized A1A trucks have a bazillion parts to them, and getting at the brakeshoes on the ones with the drop equalizers is a big pain. The 4 axle Blomberg has too many parts. The A1A has about double.
I wonder if the patterns for the EMD or AAR style A1As are even around anywhere.....
MP got the job done on 4 axles - good enough for the commuter market, anyway.
carnej1 wrote: Interestingly there are some modern "A1A" Passenger units in North America. The Alaska Railroad's SD70MACs have the ability to switch one of the AC Inverters from traction to HEP for passenger train service. When this feature is selected one traction motor on each truck is cut out, making them "A1A". For freight the engineer switches the electrical system back to standard CC configuration.It's a clever way to use the units electrical capacity and have plenty of "hotel power" available without needing an auxiliary genset.
This isn't true, on the SD70MACs with HEP you cut out the power to one whole truck, making the locomotive a C-3, rather than an A1A. The SD70MAC has two traction invertors, one for each truck, not three for pairs of axles.
The reason for the disappearance of the A1A truck is related to the need for weight on the powered axles, too much power for too little weight means the wheels will slip. Of course you could limit the power at lower speeds, but US passenger cars are relatively heavy, compared to European designs.
beaulieu wrote: carnej1 wrote: Interestingly there are some modern "A1A" Passenger units in North America. The Alaska Railroad's SD70MACs have the ability to switch one of the AC Inverters from traction to HEP for passenger train service. When this feature is selected one traction motor on each truck is cut out, making them "A1A". For freight the engineer switches the electrical system back to standard CC configuration.It's a clever way to use the units electrical capacity and have plenty of "hotel power" available without needing an auxiliary genset. This isn't true, on the SD70MACs with HEP you cut out the power to one whole truck, making the locomotive a C-3, rather than an A1A. The SD70MAC has two traction invertors, one for each truck, not three for pairs of axles.
What you say is exactly right for a freight only SD70MAC, but those Alaska SD70MACs might be a special case, since they are "dual mode" need the output of one inverter for HEP. Very clever to go A1A-A1A on one inverter in passenger mode.
beaulieu wrote: carnej1 wrote: Interestingly there are some modern "A1A" Passenger units in North America. The Alaska Railroad's SD70MACs have the ability to switch one of the AC Inverters from traction to HEP for passenger train service. When this feature is selected one traction motor on each truck is cut out, making them "A1A". For freight the engineer switches the electrical system back to standard CC configuration.It's a clever way to use the units electrical capacity and have plenty of "hotel power" available without needing an auxiliary genset.The reason for the disappearance of the A1A truck is related to the need for weight on the powered axles, too much power for too little weight means the wheels will slip. Of course you could limit the power at lower speeds, but US passenger cars are relatively heavy, compared to European designs.
Don't forget that when all those A1As were being built, the norm was axle loadings from 70 ton frt cars. Now it's 100+ tons....
oltmannd wrote:What you say is exactly right for a freight only SD70MAC, but those Alaska SD70MACs might be a special case, since they are "dual mode" need the output of one inverter for HEP. Very clever to go A1A-A1A on one inverter in passenger mode.
Don, shame on you, you have knowledge about locomotives, each invertor is designed to power three axles, you must have some idea of the complications of the additional wiring and serious software changes that would be required to make one of the invertors power 4 axles when in HEP mode, and only 3 motors when in normal mode. The ARR HEP MACs are a cheap and dirty modification to get a combination freight and passenger locomotive. To shift one invertor to HEP just requires software changes to allow them to work at different settings, to allow one to power 4 instead of 3 would require some fancy switchgear and a lot of extra cabling. Remember the front invertor powers the front truck of the locomotive, the rear invertor powers the rear truck. You would need six cables running from the front invertor to the rear truck (three for each motor), and they would only be used when the locomotive is in HEP mode. The invertor that powers either three or 4 axles would have had to be custom designed, and would have cost a great deal of money, and to boot it would be non-standard compared to the rear one and those used in the non-HEP equipped in the ARR fleet. Something like what is proposed would be easy with a GE AC4400CW where you have one invertor per axle, and all 6 invertors are in one compartment adjacent to each other, but in the SD70MAC the invertors are located at each end of the long hood with the engine compartment inbetween. It is totally impractical in a SD70MAC or a SD70ACe. Remember the ARR went through some hoops to get non-Tier II compliant SD70MACs rather than SD70ACes for parts commonality reasons. That is also why the GP49s departed rather than the less fuel efficient GP40-2s.
beaulieu wrote: oltmannd wrote: What you say is exactly right for a freight only SD70MAC, but those Alaska SD70MACs might be a special case, since they are "dual mode" need the output of one inverter for HEP. Very clever to go A1A-A1A on one inverter in passenger mode. Don, shame on you, you have knowledge about locomotives, each invertor is designed to power three axles, you must have some idea of the complications of the additional wiring and serious software changes that would be required to make one of the invertors power 4 axles when in HEP mode, and only 3 motors when in normal mode. The ARR HEP MACs are a cheap and dirty modification to get a combination freight and passenger locomotive. To shift one invertor to HEP just requires software changes to allow them to work at different settings, to allow one to power 4 instead of 3 would require some fancy switchgear and a lot of extra cabling. Remember the front invertor powers the front truck of the locomotive, the rear invertor powers the rear truck. You would need six cables running from the front invertor to the rear truck (three for each motor), and they would only be used when the locomotive is in HEP mode. The invertor that powers either three or 4 axles would have had to be custom designed, and would have cost a great deal of money, and to boot it would be non-standard compared to the rear one and those used in the non-HEP equipped in the ARR fleet. Something like what is proposed would be easy with a GE AC4400CW where you have one invertor per axle, and all 6 invertors are in one compartment adjacent to each other, but in the SD70MAC the invertors are located at each end of the long hood with the engine compartment inbetween. It is totally impractical in a SD70MAC or a SD70ACe. Remember the ARR went through some hoops to get non-Tier II compliant SD70MACs rather than SD70ACes for parts commonality reasons. That is also why the GP49s departed rather than the less fuel efficient GP40-2s.
oltmannd wrote: What you say is exactly right for a freight only SD70MAC, but those Alaska SD70MACs might be a special case, since they are "dual mode" need the output of one inverter for HEP. Very clever to go A1A-A1A on one inverter in passenger mode.
Mea culpa! You are right. Lots of cable and switch gear. Also, would have to match wheels on all the axles, not just all the axles on one truck. Big pain.....
oltmannd wrote: Those equalized A1A trucks have a bazillion parts to them, and getting at the brakeshoes on the ones with the drop equalizers is a big pain. The 4 axle Blomberg has too many parts. The A1A has about double.I wonder if the patterns for the EMD or AAR style A1As are even around anywhere.....MP got the job done on 4 axles - good enough for the commuter market, anyway.
The EMD A1A patterns were scrapped years ago. You are exactly right about the number of parts in both the A1A and the GP swinghanger trucks - no one today would design a truck like that. Too many wearing surfaces that are expensive and difficult to restore during rebuild. Look at the HTCR - no wearing parts to weld up and machine, just change bushings and some bolt-on wearplates and it is back to new condition.
Dave
jrw249 wrote:So E units don't have 3 traction motors per truck?
No, just two motors. If they had three it would be a C-C locomotive. Letters indicate powered axles, numbers indicate unpowered.
wyomingrailfan wrote:I believe the idler was used to make the E units have a better ride.
The idler was mostly to hold the locomotive up. An E8 is too heavy for 4 axles.
YoHo1975 wrote:Why are bloombergs so popular still? Why didn't the HT-B truck on the GP40X become wide spread? I mean, I realize that the HT-B didn't take off and therefore there are approximately a bazillion Bloomberg B and M trucks to scavange, but still. If they were such a nightmare....
I know very little about the HT-B. That'd be a good one for bogie_engr. Hope he chimes in. The Blomberg is a proven design with good ride characteristics (with the leaf spring secondaries, anyway), and it's easy to do brake shoes and adjust piston travel, but no one would start from scratch today and come up with that design. As long as there are good frame castings floating around, the Blomberg will soldier on. Big steel castings are expensive.
jrw249 wrote:Do the E units have two diesel engines and generators?
Yes. One powers the front truck and the other the rear truck.
For more Faster Accleration and also to since they were Passenger power usaly they were over powered normally.
jrw249 wrote:If a F unit has 4 traction motors and an E unit has 4 traction motors then why does the E unit have 2 diesel engines and the F unit only has one diesel engine.
More HP!
An F7 has a single 16 cyl engine making 1500 HP and an E8 has 2250 HP.
An F9 has 1750 HP and an E9 has 2400.
The EMD "F", "GP" and "SD" series (except the SD45) had one 16 cylinder diesel engine.
The EMD SD45 had one 20 cylinder diesel engine, as did the F45 and the FP45.
The EMD "E" series had two 12 cylinder diesel engines.
The EMD "DD" series had two 16 cylinder diesel engines.
OLTMANND got it right - the "A-1-A" truck was required for distribution of the weight of the then heavy "E" units. The very first of EMD's passenger locomotives (EMD #511 & #512, B&O #50, ATSF #1 & #1A) had two Winton 12 cylinder 201-A diesel engines and were on "B" trucks. With the introduction of the "E" series in 1935 EMD also went to the A-1-A truck.
The EMD FL9 locomotives have a "B" truck under the front and a "A-1-A" truck at the rear. Again, weight distrtibution.
Because the E unit had two engines I was wondering why it didn't have twice the horsepower as the F unit but you explained why ( i.e. smaller engines). Thats everyone for the information.
oltmannd wrote: YoHo1975 wrote:Why are bloombergs so popular still? Why didn't the HT-B truck on the GP40X become wide spread? I mean, I realize that the HT-B didn't take off and therefore there are approximately a bazillion Bloomberg B and M trucks to scavange, but still. If they were such a nightmare....I know very little about the HT-B. That'd be a good one for bogie_engr. Hope he chimes in. The Blomberg is a proven design with good ride characteristics (with the leaf spring secondaries, anyway), and it's easy to do brake shoes and adjust piston travel, but no one would start from scratch today and come up with that design. As long as there are good frame castings floating around, the Blomberg will soldier on. Big steel castings are expensive.
The HT-B story probably belongs in a different thread but here goes:
The GP swinghanger truck, as EMD calls it, is still around because there was no incentive to design a new 2-axle truck once the HT-B died it's quick death. The HT-B was created simply to improve the weight shift between axles that the GP swinghanger truck suffers from so badly. When a locomotive equipped with GP trucks is working at 25% adhesion, the lightest axle (which ever axle is leading on the lead truck) is at about 84% of it's static axle load while the trailing axle of the trailing truck is at about 116% of static. Before the introduction of the Super Series wheel creep control, this caused the adhesion capability of the locomotive to be limited by the slip of whichever wheel slipped first, almost always the lead wheel of the lead truck due to the weight shift. The HT-B was designed to address that with its inclined rubber secondary suspension focused at rail height and the much lower centerbearing. The net result was almost no weight shift between axles within one truck and only the weight shift between trucks due to the coupler height above the rail. So at the same 25% adhesion, the HT-B lead truck axles are at about 96% of their static weight and the trail truck axles at about 104%. The HT-B was a technical success but being introduced with half of the GP40X prototypes, the other half with GP swinghanger trucks, allowed head-to-head adhesion testing to demonstrate the benefit of the lower weight shift. All GP40X's had Super Series wheel creep control systems and the result of testing showed no significant overall locomotive adhesion improvement with the HT-B truck. It was theorized that the creeping lead axle of the GP swinghanger truck provided a beneficial cleaning effect on the rails. Regardless, the main reason to introduce the new truck was proven no advantage. The many disadvantages of the HT-B included high production cost, a different underframe design due to the low mounted centerplate, stiffer ride compared to the leaf spring GP's, and a longer wheelbase that cut into the limited space on a GP model for fuel. But I think most importantly, EMD at the time did a good business in LRO (Locomotive Rebuild Order) orders where a customer would trade-in a unit for re-use of trucks, traction motor frames and some engine parts. Without trade-in credit for the trucks, the value of the trade-in was minimal so EMD lost a major competitive marketing advantage. So before the GP50 was introduced, the HT-B was dead within EMD, even though there is literature that suggests otherwise.
By that point in time, 4 axle locomotive production was dwindling and the truck design effort was focused on developing the radial steering trucks. If you were designing a 2 axle truck today, the GE P40/P42 truck or the EMD DE/DM30AC truck might be typical of what a new design would look like. Not the fabricated frames necessarily, but the elimination of friction wear surfaces such as the pedestal liners, bolster chafing plates, swinghanger bearing blocks and bushings, etc. in favor of rubber bushings that give consistent performance over their wear life.
The ride on an E8/9 was the best I ever had (on a train). So smooth, and so slippery!
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