# Amtrak engine trucks



## jwhit27237 (Jun 22, 2022)

Why does Amtrak not go to C (6-wheel trucks) instead of B (4-wheel trucks)? They would have better grip and extend time on the marker reader time? Pluss being easier on the rails themselves?


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## jis (Jun 22, 2022)

6 axle trucks are actually harder on the tracks than 4 axle trucks. That is one reason that there are no high speed rail engines with 6 axle trucks anywhere in the world.

Additionally Amtrak has had terrible experience with 6 axle trucks (hunting, derailments, speed restriction to 90mph or less) when it tried them in their early days, and then shunned them for good. They are quite unlikely to go back to them when they have 4 axle trucks working just fine with no problems.


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## jwhit27237 (Jun 22, 2022)

Thanks for the info. I thought the 6 axle trucks were better on tracks all the big lines run them?


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## Just-Thinking-51 (Jun 22, 2022)

Freight railroads have 6 axles, but they need the weight and traction power. When your pulling 125 freight cars it takes a bit more to start and keep them rolling. Four axles are plenty fine for a passenger train. Amtrak does not even use AC power traction motors for its trains because the train can get up to speed long before the DC motor gets hot enough to cause a issue.


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## PVD (Jun 22, 2022)

I might disagree about AC traction, since just about anything new is AC traction, even some older stuff was rebuilt AC (some AEM-7) and P32DM are AC. There are too many advantages in AC motor technology to stay with DC. Even new freight is going AC.


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## jwhit27237 (Jun 22, 2022)

Just-Thinking-51 said:


> Freight railroads have 6 axles, but they need the weight and traction power. When your pulling 125 freight cars it takes a bit more to start and keep them rolling. Four axles are plenty fine for a passenger train. Amtrak does not even use AC power traction motors for its trains because the train can get up to speed long before the DC motor gets hot enough to cause a issue.


What about the Auto-trains? Sometimes they are 40+ cars long.


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## PerRock (Jun 22, 2022)

PVD said:


> I might disagree about AC traction, since just about anything new is AC traction, even some older stuff was rebuilt AC (some AEM-7) and P32DM are AC. There are too many advantages in AC motor technology to stay with DC. Even new freight is going AC.


The new Chargers are AC as well.


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## Just-Thinking-51 (Jun 22, 2022)

Flat route, lightly loaded. Auto train is slow to power up, but if only has one scheduled stop.


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## Just-Thinking-51 (Jun 22, 2022)

PVD said:


> I might disagree about AC traction, since just about anything new is AC traction, even some older stuff was rebuilt AC (some AEM-7) and P32DM are AC. There are too many advantages in AC motor technology to stay with DC. Even new freight is going AC.


Not all freight is AC. The price point is dropping, but at one point people were point out how many replacements DC motors you could buy for the difference in the cost of a AC locomotive.

The OP was asking about 3 axle trucks and those are just not need in the passenger hauling business. Although I am sure you could find a train somewhere that use it.


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## PerRock (Jun 22, 2022)

Just-Thinking-51 said:


> The OP was asking about 3 axle trucks and those are just not need in the passenger hauling business. Although I am sure you could find a train somewhere that use it.



Metra has been wanting to for a while now. Supposedly they bought some SD70MACs, been a few years since I heard anything about that however.

peter


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## Siegmund (Jun 23, 2022)

Just-Thinking-51 said:


> The OP was asking about 3 axle trucks and those are just not need in the passenger hauling business. Although I am sure you could find a train somewhere that use it.



The Alaska Railroad has been using SD70MACs in passenger service for more than 20 years.

But that wasn't because they _needed_ 6-axle passenger power, a simple matter of ordering only one new model of power. The essential point made earlier in the thread --- that you use 6 axles when you need extra tractive effort to pull heavy trains up grades, and don't need them in passenger service -- remains true.


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## jwhit27237 (Jun 23, 2022)

Siegmund said:


> The Alaska Railroad has been using SD70MACs in passenger service for more than 20 years.
> 
> But that wasn't because they _needed_ 6-axle passenger power, a simple matter of ordering only one new model of power. The essential point made earlier in the thread --- that you use 6 axles when you need extra tractive effort to pull heavy trains up grades, and don't need them in passenger service -- remains true.


Alaska RR also has a few SD45's in use too. All 6-wheel trucks.


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## jis (Jun 23, 2022)

The most widely deployed passenger locomotives, both diesel and electric on Indian Railways are Co-Co. This is because (a) IR passenger trains are 24-26 cars long pulled typically by a single engine and (b) None of the ones operated with these locos operate above 80mph.

The specific classes are WAP-7 (electric) and WDP-4(D) (diesel).

Trains that travel faster use Bo-Bo locos, typically WAP-5. In general, for faster trains IR is opting for distributed power articulated trains, internally known as T-18, externally branded as "Vande-Bharat" (which roughly translates from Sanskrit to English as "Praise India" or "Great India"))

This is consistent with the practice of using Bo-Bo's for higher speed operations.


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## PeeweeTM (Jun 25, 2022)

*Looking at the avatar of Just-Thinking-51*


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## PeeweeTM (Jun 25, 2022)

I think, the only gain for Amtrak with 6 wheel trucks would be to get a bigger fuel tank. But as the locomotives don't seem to run out of fuel between the logical fueling points, no real win there.

Auto racks are relatively light as the cargo within the superstructure is mostly air, whether empty or loaded.

The old German BR103 of Just-Thinking-51 was said to ride a bit bumpy.


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## Just-Thinking-51 (Jun 25, 2022)

PeeweeTM said:


> *Looking at the avatar of Just-Thinking-51*


Good looking motor, unable to do the higher speeds needed, add on bonus does not return braking energy to the system. Out dated technology.


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