Recently, I saw the 4146 with new or rebuilt trucks on the unit at Roseville. It had lettering on each truck that said ' Steering Link removed'/ This was one of the selling features of the EMD units and now the self steering truck seems to be a normal type truck.
Anyone know why the Union Pacific is doing this?/
Thanks
CZ
With the introduction of the SD70ACe and SD70M-2, EMD introduced a new non steering truck design, the HTC-II which used many components of the contemporary radial truck, but was also said to be cheaper to maintain in the long term. For example, all the BHP Billiton SD 70ACe units, including those diverted from a BNSF order, were fitted with the rigid truck. I therefore assume that all of BNSF's SD70ACes are also fitted with the rigid truck.
Meanwhile, also in Australia, the EMD licencee EDI Rail introduced a new design of "semi-steering" truck. This used components from a local design of truck that followed EMD steering patents but was of fabricted design to keep the weight within acceptable limits. In Australia on main lines, a six axle locomotive is limited to 134 metric tonnes compared to about 190 metric tonnes for a similar locomotive in the USA. Leaving out the steering links but allowing the axles to take up a radial position based on wheel to rail creep forces saved a couple of metric tonnes per locomotive. When you are using fibreglass radiator fan shrouds and aluminium brake air reserviors and hollow stainless steel handrails to get a 4300HP locomotive to weigh 134 tonnes, two tonnes is a worthwhile saving.
However, if you simply remove the steering links from an EMD radial truck, you would obtain a truck that would be regarded as "semi-steering" like the EDI Rail design. Or you could fit rigid links making the truck similar to the rigid SD 70ACe truck.
So I can't say which option UP has taken but either way, UP may be testing whether radial trucks are advantageous in their specific conditions.
The big advantages of radial trucks are on the old alignments in the East, on CSX and NS. in the West, where really sharp curves are less prevalent rigid trucks my be cheaper to operate overall.
M636C
M636C With the introduction of the SD70ACe and SD70M-2, EMD introduced a new non steering truck design, the HTC-II which used many components of the contemporary radial truck, but was also said to be cheaper to maintain in the long term. For example, all the BHP Billiton SD 70ACe units, including those diverted from a BNSF order, were fitted with the rigid truck. I therefore assume that all of BNSF's SD70ACes are also fitted with the rigid truck. Meanwhile, also in Australia, the EMD licencee EDI Rail introduced a new design of "semi-steering" truck. This used components from a local design of truck that followed EMD steering patents but was of fabricted design to keep the weight within acceptable limits. In Australia on main lines, a six axle locomotive is limited to 134 metric tonnes compared to about 190 metric tonnes for a similar locomotive in the USA. Leaving out the steering links but allowing the axles to take up a radial position based on wheel to rail creep forces saved a couple of metric tonnes per locomotive. When you are using fibreglass radiator fan shrouds and aluminium brake air reserviors and hollow stainless steel handrails to get a 4300HP locomotive to weigh 134 tonnes, two tonnes is a worthwhile saving. However, if you simply remove the steering links from an EMD radial truck, you would obtain a truck that would be regarded as "semi-steering" like the EDI Rail design. Or you could fit rigid links making the truck similar to the rigid SD 70ACe truck. So I can't say which option UP has taken but either way, UP may be testing whether radial trucks are advantageous in their specific conditions. The big advantages of radial trucks are on the old alignments in the East, on CSX and NS. in the West, where really sharp curves are less prevalent rigid trucks my be cheaper to operate overall. M636C
Thanks for the reply. Good information to know. I was aware that some of the later orders had the ridid trucks on the BNSF units, but thought that was only a cost cutting option.
It makes sense that the self guiding trucks would benefit the owner better in tight curves in the eastern part of the USA. I did notice that not all rebuilds have that label on them. The 2002 which is the Olympic unit that was rebuilt two months ago did not get the bar removed.
This is a great forum. Ask a question and get an answer that makes sense.
So all of the steering equipment is still there, just not functioning because of a missing link???
The road to to success is always under construction. _____________________________________________________________________________ When the going gets tough, the tough use duct tape.
bubbajustin So all of the steering equipment is still there, just not functioning because of a missing link???
It depends on exactly what UP have done.
If they just removed the link between the truck and the carbody, the internal connections could still be there allowing the truck to adopt aradial position on curves. The trigger would be the "creep forces" on the wheels, rather than the body truck link. The creep forces arise through the wheels being rigidly attached to the axle. in a curve the outer wheel will try to turn faster because it is travelling (relatively) further than the inner wheel. This causes the axle to shift so that the tapered treads move to match the rotational speed on each side.
In doing this it also tries to adopt a radial position. If there is enough freedom of movement, it should do this.
This has been used for hauled trucks for some years, but there is a theoretical concern that overlaying the traction forces on a powered might distort these creep forces, and this was why EMD used the body truck links.
I know EMD representatives were along on trials of EDI's first GT 46C-ACe (a lightweight, low profile SD70ACe fitted with SD70MAC motors and fabricated semi steering trucks) because I was there and asked how it ran. They said it tracked well at all speeds.
But the EDI truck doesn't have the inter axle links either, although the axle mountings are otherwise the same as those on the body link steered DC motor GT 46C. But the presence of such links would not stop the creep forces working.
But I don't have any inside information on UP's modification. It could be a removal of the body link, removal of all inter axle links or a full conversion to a rigid truck like the HTC-II.
M636Cbubbajustin So all of the steering equipment is still there, just not functioning because of a missing link??? It depends on exactly what UP have done. If they just removed the link between the truck and the carbody, the internal connections could still be there allowing the truck to adopt aradial position on curves. The trigger would be the "creep forces" on the wheels, rather than the body truck link. The creep forces arise through the wheels being rigidly attached to the axle. in a curve the outer wheel will try to turn faster because it is travelling (relatively) further than the inner wheel. This causes the axle to shift so that the tapered treads move to match the rotational speed on each side. In doing this it also tries to adopt a radial position. If there is enough freedom of movement, it should do this. This has been used for hauled trucks for some years, but there is a theoretical concern that overlaying the traction forces on a powered might distort these creep forces, and this was why EMD used the body truck links. I know EMD representatives were along on trials of EDI's first GT 46C-ACe (a lightweight, low profile SD70ACe fitted with SD70MAC motors and fabricated semi steering trucks) because I was there and asked how it ran. They said it tracked well at all speeds. But the EDI truck doesn't have the inter axle links either, although the axle mountings are otherwise the same as those on the body link steered DC motor GT 46C. But the presence of such links would not stop the creep forces working. But I don't have any inside information on UP's modification. It could be a removal of the body link, removal of all inter axle links or a full conversion to a rigid truck like the HTC-II. M636C
Thanks for the explanation.
Maybe it would be more useful if the steering wheel was in the cab and not way in the back... no wonder they got rid of that feature!
It's been fun. But it isn't much fun anymore. Signing off for now.
The opinions expressed here represent my own and not those of my employer, any other railroad, company, or person.t fun any
zugmann Maybe it would be more useful if the steering wheel was in the cab and not way in the back... no wonder they got rid of that feature!
Good one! The actual steering wheel is in Omaha with the dispatcher.
CAZEPHYRzugmann Maybe it would be more useful if the steering wheel was in the cab and not way in the back... no wonder they got rid of that feature! Good one! The actual steering wheel is in Omaha with the dispatcher. CZ
James
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