Talk:Krauss-Helmholtz bogie

Article errors
This article appears to contain fundamental errors, and needs to be re-written, preferably by someone with operating experience of the K-H truck. This truck was/is fitted to the South African Railways 2-foot gauge 2-8-2 NG15 class locos. One of these is currently being restored on the Welsh Highland Railway, Wales, UK, and at least one is in steam at the Sandstone Estates system in South Africa. Engineers from either of these railways would be well qualified to speak on the K-H truck from hands-on experience. The K-H truck as drawn here cannot work - it would derail at the first curve. In addition to the pivot as drawn, there must also be a slider, to permit lateral movement of the truck. The K-H truck is best thought of as a four-wheeled bogie (as fitted to a 4-6-2 for example), but with the following departures from the four-wheeled bogie: (1) the rear wheelset is of a greater diameter than the leading wheelset - in fact it has the same diameter as the driving/coupled wheels; (2) the rear wheelset is driven by a pair of coupling rods; (3) the axle of the rear wheelset does not rotate into the curve, but remains parallel to the other driving/coupled wheels - of course it can, and must, move laterally as the loco enters the curve. This is why there has to be a slider, and not just a simple pin. The rear wheelset must move laterally in the same direction as the leading wheelset (although not as much), and not in the opposite direction as drawn. - Comment by User:Tonnaxyz moved here from article mainspace.


 * Thank you for your comments. Having reviewed the article text against Lexicon der Eisenbahn and German Wikipedia, I am struggling to understand what "fundamental errors" are being referred to. The diagram is rather basic but it appears to address the points made i.e. the "rear wheelset" (actually the forward coupled wheelset) is shown as (1) larger than the carrying wheelset, (2) coupled and (3) able to move laterally (hence the double-headed arrow). What is less clear IMHO, but explained in the text, is that the carrying wheels pivot radially about the pivot pin and returned to the centre position by heavy duty springs.
 * As far as I can see, the "rear wheelset" cannot move laterally in the same direction as the carrying wheelset as you suggest. If it did the lever would break.
 * If you know of experts who could check this and cite appropriate source material for any changes to the text, that would be great. Bermicourt (talk) 18:18, 11 March 2015 (UTC)

Dear Bermicourt. Thank you very much for moving this to the talk page - as a novice user of Wikipedia, I did not realise that this was an option, and it is much the better option! Thank you also very much for your reply, and also your edits in your main text. I think you have in fact covered the main issue, which is that I believe the lever pivot needs to be mounted in a sliding block, which moves laterally as the loco enters or remains on a curve. I recall seeing photos from the Welsh Highland Railway's NG15 2-8-2 showing such a slider. This is just like the slider on a normal loco bogie, as in a 4-6-2 wheel arrangement. If a normal bogie did not have a slider, the loco would derail at the first curve. I am a model engineer and UK chartered engineer, and have experience of bogies on live steam miniature locos. When I have time (!), I will try to get some source references sorted out. I have long been impressed by the ingenuity of German steam loco designers in articulating long wheelbase locos for normal curved railway tracks, e.g. K-H, Luttermoller, Klein-Linder. I believe the locos on the Harz Mountains railways have articulation, possibly K-H?). In the meantime, thank you for your patience, and all best wishes!  — Preceding unsigned comment added by Tonnaxyz (talk • contribs) 12:08, 21 March 2015 (UTC)
 * The Harz Mountains are a special place. I spent many days hiking around the Harz in my quest to become the first British Harzer Wanderkaiser by visiting all the checkpoints in the Harzer Wandernadel. It was amazing to see and hear the steam engines in many parts of the Harz; quite ethereal if you were in the middle of the forest and could hear the long whistle blasts of the loco. Welcome to Wikipedia and enjoy building articles. One of my interests is pre-war German railways and we have a task force here in case you're interested too. Cheers. --Bermicourt (talk) 16:29, 21 March 2015 (UTC)

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