clecklewyke Posted February 20, 2016 Share Posted February 20, 2016 In another place I explain how eye-sight problems are causing me to consider moving from P4 to OO. One way forward would be to sell my P4 converted Hornby or RTR locos and replace them with new (or used) RTR equivalents. I might lose a bit of money- P4 locos have a smaller market than OO equivalents - but it would save a lot of time and money fitting new Gibson OO wheels. However, I am not impressed with the quality of RTR coupling rods as they are very over-sized and chunky compared with the real thing. One can buy better coupling rods from several sources (Comet, Gibson etc.) but I wonder whether they can be fitted to the Hornby or Bachman wheels, and in particular to the crankpins they use, which I presume are of a bigger diameter than e.g. the Gibson ones. Am I worrying unnecessarily; has anyone any experience of fitting better scale crankpins to RTR wheels? Ian Link to post Share on other sites More sharing options...
RMweb Gold ROSSPOP Posted February 20, 2016 RMweb Gold Share Posted February 20, 2016 hi Ian Yes I have..... Mainly use Gibson rods and Gibson infill washers when you have to remain with the RTR coupling rods for those wheelbases that are a compromise(wrong) Gibsonised Hornby..... If you use wet and dry on the gibson axles until finely polished you can fit them by finger pressure alone and thus prevent damage to the plastic axle hole and also prevent wheel wobble........ Ditto with Bachmann Of course Ian you could sell, all/ mostof , your P4 stuff and move into O Gauge...... John Link to post Share on other sites More sharing options...
clecklewyke Posted February 20, 2016 Author Share Posted February 20, 2016 hi Ian Yes I have..... Mainly use Gibson rods and Gibson infill washers when you have to remain with the RTR coupling rods for those wheelbases that are a compromise(wrong) Of course Ian you could sell, all/ mostof , your P4 stuff and move into O Gauge...... John Hi, John. I think you have misunderstood me. I think you have re-wheeled your locos with Gibson wheels. I am thinking of retaining the Hornby/Bachman wheels but improving them by using, say, Gibson rods. I want to avoid re-wheeling. The question really is, can you use finsecale rods with the crankpins on Hornby or Bachman wheels. I suspect not because the crankpins will probably have too large a diameter. Ian Link to post Share on other sites More sharing options...
RMweb Gold ROSSPOP Posted February 20, 2016 RMweb Gold Share Posted February 20, 2016 Sorry Ian Yes I did misunderstand your point. I would think that there is not enough metal area on the boss ends of `scale` coupling rods to accomodate the size of hole required to use the RTR `crankpins` Which is why the RTR crankpin bosses look so oversize. But then is it worth making the RTR coupling rods profile thicker by sweating on extra metal......... a lot of extra work that I have never tried....... Then the crankpins will protrude and catch on locos with outside valve gear......... John Link to post Share on other sites More sharing options...
RMweb Gold Joseph_Pestell Posted February 20, 2016 RMweb Gold Share Posted February 20, 2016 I suspect that there is no single answer to this question. It will vary from loco to loco. The crankpins on most modern r-t-r are not that large a diameter. There is a huge amount of "slop" as the holes in the rods are much larger than the diameter of the crankpins. All part, I suppose, of making things to go round 15" radius curves. I think that you will need to experiment but it is probably possible to use finer rods although you might need to open out the holes a bit. Link to post Share on other sites More sharing options...
Quarryscapes Posted February 20, 2016 Share Posted February 20, 2016 It's going to vary a fair bit, but I've just measured a Bachmann 57xx wheelset. They don't use separate crankpins but a boss that's part of the wheel of 2mm diameter which is tapped for a screw to hold the rods captive. I imagine most Bachmann of similar vintage will be to the same dimensions, but can't guarantee of course. (I have only converted the 57xx so far) Link to post Share on other sites More sharing options...
RMweb Premium Daddyman Posted February 21, 2016 RMweb Premium Share Posted February 21, 2016 It's going to vary a fair bit, but I've just measured a Bachmann 57xx wheelset. They don't use separate crankpins but a boss that's part of the wheel of 2mm diameter which is tapped for a screw to hold the rods captive. I imagine most Bachmann of similar vintage will be to the same dimensions, but can't guarantee of course. (I have only converted the 57xx so far) Mmm, I think this is the problem. What makes the rods so overscale is the crankpins and screws/bolts that RTR locos are fitted with. I've just measured a Hornby L1 and that has a similar tapped boss on the centre wheel which measures 3mm! As a comparison, when I'm using Romford crankpins on a kit-or scratchbuilt loco, I'm drilling the rods to either 1.2 or 1.3mm (I can't recall at the moment). That's a considerable difference. I'm pretty sure there is not enough "land" on a scale rod for a 3mm hole, much less for the 3.2 or 3.3mm hole that would be required for play. I have some unwanted Gibson 9'6" rods that have a barbaric southerno-great-western fish-belly shape on them, so are unusable on the NER loco I bought them for. You can have them if you want to experiment with a 3mm drill (or a 2mm drill if you are modelling a pannier). I don't possess a drill that big so can't try for you. But I suspect that if you plan to re-use the RTR wheels I think you'll be forced to use their crankpins and therefore forced to use their rods. If I were you I would keep your converted locos, sell the P4 wheels and replace with Gibson 00 wheels - you know these will fit your (scale) rods. Link to post Share on other sites More sharing options...
clecklewyke Posted February 21, 2016 Author Share Posted February 21, 2016 Many thanks, especially to the last two posters, who took the trouble to measure the rtr crankpins. It is, as I suspected, not going to be possible to put scale rods on rtr wheels so I will probably bite the bullet and convert my P4 locos back to OO. Ian Link to post Share on other sites More sharing options...
RMweb Premium Nile Posted February 21, 2016 RMweb Premium Share Posted February 21, 2016 Even if you don't make any money from your P4 wheels, buying new OO Gibson wheels is going to be much cheaper than buying a whole new loco. And new wheels is all you need, everything else is re-used. Link to post Share on other sites More sharing options...
Quarryscapes Posted February 22, 2016 Share Posted February 22, 2016 Just for reference, Gibson crankpin bushes are 1.5mm diameter, so if you've got rods that are meaty enough they may be suitable for opening out to suit Bachmann wheels. Link to post Share on other sites More sharing options...
drgj Posted February 26, 2016 Share Posted February 26, 2016 Pretty sure someone makes variable wheel base etched rods that you build up. Can't remember who, though! Dave Link to post Share on other sites More sharing options...
RMweb Premium Daddyman Posted February 26, 2016 RMweb Premium Share Posted February 26, 2016 Pretty sure someone makes variable wheel base etched rods that you build up. Can't remember who, though! Dave Gibson. Link to post Share on other sites More sharing options...
RosiesBoss Posted February 26, 2016 Share Posted February 26, 2016 G'day, all, I agree that many RTR models have over-scale rods - probably engineered to be bullet-proof (and child-proof). Their replacement with new rods of scale proportions is more feasible when the model is re-wheeled with scale wheels from Gibson, Markits, Romford, etc. But for those of us who (for various reasons) wish to keep the original wheels, rod replacement is not so easy. One way may be to first fit Romford crank pins to the original wheels, provided that the crankpin hole in the RTR wheel is not too big, and then fit scale rods. For those of us who find this to be a bit too hard (eg due to poor availability or lack of funds), there is a simple dodge that has improved some of my models. Part of the issue is the insistence by many manufacturers to chrome- or nickel-plate the rods. This draws the eye to them and exacerbates the over-scale appearance. If they are painted in the same colour as the wheels or otherwise weathered with track colour, they blend in to the model much more effectively. Here is an image of an old Hornby Ivatt 2MT, where (among other issues) the valve gear assembly shouts that is is so toy-like: Here is an image of a similar model, converted to Standard 2MT with a Crownline conversion kit. Here, the same wheels and valve gear (with new cylinders) appear much more acceptable. The difference is black paint. Food for thought? Regards, Rob Link to post Share on other sites More sharing options...
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