McWaffel Posted February 20, 2017 Hey guys! I've been playing with the idea of implementing a terminus station into my layout. This would mean that trains need to reverse out of the station and in the best case drive around normally in reverse with a cab at the non-powered control car at the end. See this picture for explanation: I've noticed that by pushing, the Lego train engines seem to struggle a bit more with higher loads than while pulling. I don't understand why this is the case though. Physically, the forces should be the same, no? Maybe I'm missing something. Obviously I could just put an engine at either end of the train but I'm trying not to in order to have more independent trains running around. A push-pull train is very common in Germany for example (where I live). That's where I got the idea from. Share this post Link to post Share on other sites
Slegengr Posted February 20, 2017 As an engineer (mechanical, not train), I would say that the resistance would be higher when pushing than when pulling due to the difference in how the force reacts on the linkage. To pose this example, picture a rope. If you pull it, the rope stays aligned. If you push it, the rope ripples and coils over itself. Since the linkage on the train allows loose rotation, the motion could be exaggerated as the same as a rope. With the engine pulling, the cars are being aligned within the tracks. With the engine pushing, the cars will be pushed off-angle against the tracks trying to derail, causing more wedging within the track rails and resistance to the motion. I would not think this would be significant with LEGO trains, but it would have some effect. This is just my thoughts. Out of curiosity, what type of engine are you using (remote control, 9V, etc.)? I have an old 9V engine that runs faster or slower depending on which way it is placed on the rails. If the same thing is happening for you, flipping the engine bogie on the engine may help. I am not sure of this, but you might try it. Share this post Link to post Share on other sites
M_slug357 Posted February 20, 2017 Assuming your train(diesel?) has one motor but two bogies, you could: -beef up with a 2nd motor bogie -put more weight directly over the powered axles -place a helper motor in the last car, and then snake an attachment cable up to the engine Share this post Link to post Share on other sites
asleepatheswitch Posted February 20, 2017 The problem is the magnetic couplers, the "slop" between the wheels and the rails, and the 90˚ turns. As the force increases, the trucks "climb" and derail. What you could try is a matched set of motors, one at each end of the train. Difficult to do with anything but a straight run. Tom Share this post Link to post Share on other sites
dr_spock Posted February 20, 2017 Maybe pushing has more rolling friction from the passenger car bogies in front of the motor to overcome. You could model a short push-pull prototype. I made a very short push-pull commuter train a couple years ago. It ran fine in push mode without noticeable lost. Share this post Link to post Share on other sites
LEGO Train 12 Volts Posted February 20, 2017 2 hours ago, Slegengr said: With the engine pulling, the cars are being aligned within the tracks. With the engine pushing, the cars will be pushed off-angle against the tracks trying to derail, causing more wedging within the track rails and resistance to the motion. I would not think this would be significant with LEGO trains, but it would have some effect. This is just my thoughts. This is the correct point of view! Share this post Link to post Share on other sites
McWaffel Posted February 22, 2017 On 20.2.2017 at 6:51 PM, Slegengr said: [...] With the engine pulling, the cars are being aligned within the tracks. With the engine pushing, the cars will be pushed off-angle against the tracks trying to derail, causing more wedging within the track rails and resistance to the motion. [...] Out of curiosity, what type of engine are you using (remote control, 9V, etc.)? I have an old 9V engine that runs faster or slower depending on which way it is placed on the rails. If the same thing is happening for you, flipping the engine bogie on the engine may help. I am not sure of this, but you might try it. I guess that makes sense. Never thought of it this way. I'm using a variety of engines, both 9V and Power Functions motors. I used them in a consist before and as long as there's something pulling as well its all fine. Once there's only push action going on there's a significant loss in traction. On 20.2.2017 at 9:02 PM, M_slug357 said: Assuming your train(diesel?) has one motor but two bogies, you could: -beef up with a 2nd motor bogie -put more weight directly over the powered axles -place a helper motor in the last car, and then snake an attachment cable up to the engine The whole point of using one engine/powered bogie is to reduce cost I could just put an engine at either end if I was to go that direction. I guess ultimately I'd have to reduce the length of the trains or use a commuter train with the engine somewhere in the middle of the train instead. That'd be an interesting design too Share this post Link to post Share on other sites
dr_spock Posted February 22, 2017 22 minutes ago, McWaffel said: I guess ultimately I'd have to reduce the length of the trains or use a commuter train with the engine somewhere in the middle of the train instead. That'd be an interesting design too Like this? A modern Stadler GTW also has the engine in the middle like the LEGO monorail. Share this post Link to post Share on other sites
McWaffel Posted February 23, 2017 @dr_spock Oh dear! That steam engine in between the passenger cars sure looks strange. I was thinking more towards a modified version of say the Metro Liner, where the first and last cars are fully equipped with seats and windows for passengers and only a small cabin is left for the driver, as where the engine and other electronics would be stored in a car that's somewhere in the middle of the whole train. Very similar to the Stadler GTW you posted. But more like this: So no dedicated engine compartment that would somehow obstruct passengers from going to another car. Single engine as a shared-bogie by the two center cars, shared bogie by the front and second cars. I think if all but the front bogies were shared bogies and the middle one was the powered one, push-pull trains would work like a charm. 4 Cars is also a good length for a Lego train imo. Share this post Link to post Share on other sites