69843 Posted May 31, 2013 Share Posted May 31, 2013 Whilst looking around at various test trains lately, not helped by Newbryfords efforts with the NR stock and the NER/GWR dynamometer cars, it made me think: Has anyone made a model test train? When I say model test train, I mean a dynamometer car that gives you a scale speed reading, a wagon reading the weight that an engine can haul etc. I believe Model Rail has such a dynamometer car, as I have heard about it occasionally in the reviews, but has anyone ever made there own such vehicles? And how would you make them? Link to post Share on other sites More sharing options...
AngryMeerkat Posted May 31, 2013 Share Posted May 31, 2013 Very good question, I'll be following this topic to see the answer as I'd love to make something similar. Mark Link to post Share on other sites More sharing options...
RMweb Gold SHMD Posted May 31, 2013 RMweb Gold Share Posted May 31, 2013 This is something I have been interested in for a long time and have had quite a few thoughts on the subject but no actual progress. I did see someones ingenious solution that went some way to being a "test train". He fitted a "cycle computer" to a wagon, entered the appropriate wheel sizes and got instant distance, min, max, average speeds, etcetera on the display. He said that the only apparante drawback being that it only worked for speeds upto 100Mph!!! (IIRC - It may have even been here on RMweb.) Very nice work/lateral thinking, I thought. Kev. Link to post Share on other sites More sharing options...
69843 Posted September 23, 2013 Author Share Posted September 23, 2013 Right, after a couple of months of forgetting about this, I recently had a rethink on the idea of this. The idea for a dynamometer car is to have a sprung drawbar in one end of the coach to give a reading of the weight that can be hauled (with the weight starting from/including the weight of the actual car itself (i.e. 300g to 1600g, giving a max load reading of 1600g including test car at 300g)) on a marked sheet. This also means that unlike a real dynamometer car, it *might* not need turning. As originally mentioned above by SHMD, a small cycle computer linked up to either the 'rear' wheels/bogie or a ninth wheel to give a reading of the speed isn't a bad idea. Depending on the model of computer used, you could set it to 1/1 scale speed giving you a reading such as 11.2mph if it's travelling at 112mph scale, of if it is capable of being set to over 100mph, scaling it down to scale speeds. I drew up a plan of this the other day, but I can't be bothered to find it now at 11:40pm, so I shall add it here soon. If anyone has a spare YMRV Mk1, it may not be a bad starting point. We haven't gotten the mag down here yet, but I do have a old Hornby/Lima BG somewhere (the over-length one), and that could probably be used as a proof of concept. I shall keep everyone posted. And if anyone wants to add ideas or critisism, I'm open to any and every idea for this. Link to post Share on other sites More sharing options...
shortliner Posted September 23, 2013 Share Posted September 23, 2013 One of the electronic luggage scales possibly - if it is capable of reading sufficiently low? I have an electronic scale that is used for measuring letter weights, and that reads from 0.000 gms/ozs/troyweight Link to post Share on other sites More sharing options...
Baby Deltic Posted September 23, 2013 Share Posted September 23, 2013 You would need a load cell out of a set of luggage scales, plus, probably the electronics unless you want to build a circuit to calculate the span and tare. The load-cell would need to be hooked to a draw-bar to measure the amount of draw-bar pull (tractive effort). You might also want to measure axle speed to calculate scale HP and acceleration. An electronic gyro out of an RC helicopter might be useful to measure gradient. Plus a powerful PIC micro to process all the info....... Edit: Small kitchen scales up to a couple of kilo's might have a small enough load-cell with enough span to weigh a couple of kilo's but still be accurate to half a gram or so. Link to post Share on other sites More sharing options...
stewartingram Posted September 23, 2013 Share Posted September 23, 2013 Didn't Model Rail pursue this concept in its early years? With a bit of refinement and modification into a vehicle I'm sure it could be done. No doubt our friend dibber will be along soon to correct this, but I think they used a mechanical spring scale, anchored at one end, the other being hooked to the loco. The result drawbar "horsepower" was then recorded by the scale of the machine. Stewart Link to post Share on other sites More sharing options...
34theletterbetweenB&D Posted September 23, 2013 Share Posted September 23, 2013 Over a decade past I had a fiddle around with the load cell from an electronic kitchen scale which could manage 2g increments. The board with the readout was a rather clumsy item to accomodate in 4mm scale, and the trip to the floor that had ruptured the scales' outer casing (and thus made it available) led to somewhat flaky reliability in use. However, using this NPL calibrated - NOT - 'instrument' and with the controller turned up to 11, I obtained a power estimate from my somewhat modified Bachmann A4 of 1.2W at the drawbar; for which I claim a totally unverifiable UK record for steam bodied OO traction... Link to post Share on other sites More sharing options...
Baby Deltic Posted September 23, 2013 Share Posted September 23, 2013 A class 3 scale will have 3000 divisions, therefore it could be 0.5 to 1500g, 1 to 3000g etc, or if it has dual increments, e=0.5g to 3000e (1500g) then e=1g from 1500g to 3000g. Link to post Share on other sites More sharing options...
shortliner Posted September 25, 2013 Share Posted September 25, 2013 FWIW - Maplins sent a money off listing today = they have a portable luggage scale, weighing in gms, kilos, pounds, ozs for £7.99 ref# N35HT Link to post Share on other sites More sharing options...
billbedford Posted September 26, 2013 Share Posted September 26, 2013 Just a clue for those looking at using load cells, The rolling resistance of a 4mm wagon with pin-point bearings is around 0.5 gm and for a coach 1.5 - 2 gm. Link to post Share on other sites More sharing options...
Baby Deltic Posted October 9, 2013 Share Posted October 9, 2013 You could always invest in one of these little pull meters: http://www.micromark.com/digital-pull-meter,9577.html?ns_md=Email&ns_sc=Marketing&ns_cn=13WS065&ns_pc=13WS065&utm_source=Marketing&utm_medium=Email&utm_campaign=13WS065 Link to post Share on other sites More sharing options...
69843 Posted October 9, 2013 Author Share Posted October 9, 2013 You could always invest in one of these little pull meters: http://www.micromark.com/digital-pull-meter,9577.html?ns_md=Email&ns_sc=Marketing&ns_cn=13WS065&ns_pc=13WS065&utm_source=Marketing&utm_medium=Email&utm_campaign=13WS065 Thanks for pointing that out. I may have to pick one up soon. Link to post Share on other sites More sharing options...
Baby Deltic Posted October 9, 2013 Share Posted October 9, 2013 I've just ordered one. Link to post Share on other sites More sharing options...
Recommended Posts
Archived
This topic is now archived and is closed to further replies.