Coldgunner Posted August 8, 2012 Share Posted August 8, 2012 Hoping someone can answer this question... Take 2 loco's, any class and double head them on a heavy train. Is the tractive effort and power output greater than the sum of the component loco's or is it simply loco 'x' times 2? i.e. would 2x 9F's doubleheaded be simply 39,667lbf x2 (79334lbf), or would it be greater/less than? Link to post Share on other sites More sharing options...
Baby Deltic Posted August 8, 2012 Share Posted August 8, 2012 There was a thread on this in the old forum with a link to an excellent US website explaining tractive effort and horsepower. Link to post Share on other sites More sharing options...
Baby Deltic Posted August 8, 2012 Share Posted August 8, 2012 Found the site: http://www.alkrug.vcn.com/rrfacts/rrfacts.htm Link to post Share on other sites More sharing options...
Coldgunner Posted August 8, 2012 Author Share Posted August 8, 2012 Superb, looks like a good read. Link to post Share on other sites More sharing options...
retbsignalman Posted August 12, 2012 Share Posted August 12, 2012 Hi! Without going too much into the horrors of maths, when I was on my Trainmans course in '89, we were told that it wasnt double the power, but 1.5 the power of the two locos. This was the 'general rule of thumb' calculation for traincrew when making up trains and assessing power requirements etc. Hope this helps, Graeme Link to post Share on other sites More sharing options...
Edwin_m Posted August 12, 2012 Share Posted August 12, 2012 When DBS ran the long coal trains a few years back, I'm pretty sure the pair of 66s hauled 42 bogie hoppers which is twice a typical single-headed train. Link to post Share on other sites More sharing options...
RMweb Gold The Stationmaster Posted August 12, 2012 RMweb Gold Share Posted August 12, 2012 It's all a bit more complicated than simply doubling the single loco load. With modern traction the question of coupling strength is probably more important that adding another loco or two and mixed coupling types make things even more complicated (when we ran the 12,000 tonne trial out of Merehead c.20 years ago the biggest problem was coupling mix and the biggest fear was a coupling breaking. The latter was exactly what happened but surprisingly it was a loco drawhook that went and not a wagon coupling or headstock). The position and nature of gradients is also important and that to can relate back to coupling strength. Don't forget that today the freight operators are playing with some very powerful locos by British standards but still doing it on a very British railway topography - and often trains will run out of length before they run out of trailing tonnage. Link to post Share on other sites More sharing options...
woodyfox Posted August 14, 2012 Share Posted August 14, 2012 It gets more complicated when 2 different 'blue star' loco's are used as an example with different tractive effort, load regulation and horsepower etc... Then if really want to enter a quantum physical universe - how about the combination of old Southern Region multiple working with KA/KB/JA/JB 4VEP etc.............. Link to post Share on other sites More sharing options...
DonB Posted August 14, 2012 Share Posted August 14, 2012 Haven't looked at the USA link,(perhaps I should!), be what happens with the USA / Canadian practice of topping and tailing the consist with an additional loco in the centre? Link to post Share on other sites More sharing options...
RMweb Gold The Stationmaster Posted August 14, 2012 RMweb Gold Share Posted August 14, 2012 Haven't looked at the USA link,(perhaps I should!), be what happens with the USA / Canadian practice of topping and tailing the consist with an additional loco in the centre? The point of putting a loco mid-train or on the rear is to reduce coupling strain and depending on how the controls are arranged it can be useful when blowing-off the brakes. When we did it with the 12,000 tonne job we had a loco in the middle mainly to reduce coupling loadings as we had some vehicles in the train with 50 ton couplings. However brake propagation can be a far bigger problem especially on a hilly road with a very long train as you can be in a situation where you need to apply power at the front but the brakes are still partially applied at the back (which is why they use 'End of Train' monitoring kit in the USA as it lets them know the state of the brake at the back of the train). Thus if you can pump up the brake from mid train (or the rear) you will get the brakes at the back off a lot quicker. Quite how the US roads run it I don't know but I'm sure they are fully aware of all the problems and most of the answers. When we tried it we knew the problems and thought we knew some of the answers but we couldn't squeeze an EoT monitor out of the Yanks (despite me asking those with the right contacts if they could touch up their US contacts for one and that was possibly partly our undoing although the coupling which broke was found to have a slight flaw (which had never been bothered by a 5,000 tonne trailing load but clearly didn't like being in the middle of 12,000 tonnes trying to do two different things. Link to post Share on other sites More sharing options...
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