I'm torn on plastic vs metal. Metal wheels oftentimes do perform better, but they make a lot of noise. Plastic wheels don't make the noise, but they can and do warp, leading to poor performance. So the debate continues.
I guess for me, I don't swap metal for that plastic, and I don't swap plastic for metal. I will sometimes replace stock plastic wheelsets with a higher grade plastic version if they are warped. Accurail had a problem with warped wheelsets for a while. 3/4 sets would be fine, but the 4th was really nasty.
JJF
Prototypically modeling the Great Northern in Minnesota with just a hint of freelancing.
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While I have some cars that came with metal wheels, I much prefer plastic, although in most cases, I don't change-out the metal ones for plastic.
I would agree with the superior rolling qualities of many metal wheels, but not all of them.As for plastic wheels, I have purchased pre-owned rolling stock with crud on the plastic wheels, but it's easy enough to remove. As for crud on the wheel treads of my own rolling stock, I've yet to see any in the 30 years-or-so that my layout's been in operation.
Rolling qualities aren't much of a concern for me, as all of my locomotives have "tonnage ratings", which allows me to assign the proper loco(s) to each train with consideration to the many grades they're likely to encounter.I generally don't clean track, either, unless it's just been ballasted, as excess glue does need to be removed from the rails. I attribute the low maintenance to good housekeeping in the layout room.
Wayne
My guess is that the largest part of improvement (even with clean plastic wheels) is a much lower friction factor of the metal rim to rail vs. the plastic rim to rail. I believe that a push of a plastic wheeled truck along a straight piece of track will cause it to roll considerably less far than a similar truck with metal wheels in almost all cases.
The frictional force against movement is a combination of the friction factor and downward weight. If the steel wheeled truck goes farther, with the same initial push (on flat track) than the plastic wheeled truck, then the friction factor improvement is greater than the (potentially negative) effect of the additional downward weight on the wheel to rail friction force.
There is also the difference in the amount of axle tip friction in the axle cone, but my guess is that is a secondary effect, assuming the axle lengths are appropriate (in particular, not too long and tight) in both cases.
That's my story but if missing something, I'll be glad to not stick to it.
Paul
Modeling HO with a transition era UP bent
A lot of it is angular momentum. While total angular momentum isn't much on scale wheels, the angular momentum of metal wheels is still much greater than plastic, because of the difference in density of the materials.
That gives metal wheels more ability to roll past a brief increase in friction that might be caused by dust in the bearings, and also a bit more ability to roll over irregularities in the track that might stop or significantly slow plastic wheels.
Also, many brands of metal wheels are turned rather than just cast, making them much more consistently round than their plastic counterparts, so the car's linear momentum is dissipated much more evenly than is a car's that has plastic wheelsets.
Mark P.
Website: http://www.thecbandqinwyoming.comVideos: https://www.youtube.com/user/mabrunton
I agree 100% about the metal wheels usage. Also, I am learning metal wheels performance can decrease or increase based on the truck in which they are installed.
Scaled down, same reason the real railroads use metal wheels - Contact area. Smaller contact area means less friction.
And as Rick J mentions, the "crud" that plastic wheelsets gather (and spread) affects that contact area. More build-up of crud on the wheels makes a bigger contact area, making more friction. (And more crud on rails makes less power transmision ability.)
Ricky W.
HO scale Proto-freelancer.
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The major problem with derlin wheels is they pick up oil and dirt then spread it all over the layout. Nickle silver wheels usually do not do that the wheels and the layout keep clean, it is the reason our club bans plastic wheeled cars.
Rick Jesionowski
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John,
Here's a couple of possible reasons...
Tom
https://tstage9.wixsite.com/nyc-modeling
Time...It marches on...without ever turning around to see if anyone is even keeping in step.
Based on experience, there's no doubt in my mind that they do. They seem to roll much more freely. I've never understood why. It seems to me the important factor would be the friction between the axle ends and the pockets in the truck. I don't know why that would be different if there are metal or plastic wheels on the axles.
Whenever I put a new piece of rolling stock on the layout, I do two things. I put KD 148 whisker couplers on and replace the plastic wheels with metal if they don't already have them. The replacement wheels definitely make them roll better even if I don't know why.