Saturday, 14 April 2012

Shake, Rattle & Roll

I am probably one of the few people who is really bugged by axle slop in freight car trucks. I say this, because as far as I can see no one else seems to think it is a problem. The nearest I see to anything about axle lengths is some of the guides one can download so one can order replacement wheelsets with the right axle length by manufacturers like Reboxx and NWSL.

I have been replacing wheels in my trucks since the get-go, which for me was 14 years ago when I started my P&SR project that I abandoned. Back then, and up until a short time ago (last couple of weeks) I've been happy enough to follow the published advice. Until that is I discovered a problem.

Shake, rattle and roll.

Go and pick up a truck, any truck by your favourite manufacturer and shake it. Can you here it rattle? From what I've read the received wisdom on the model railroading sites is that a little slop is good as the trucks roll further when sloppy.

Uhm..., while this may, or may not be true, what is certainly true is that pinpoint bearings are not designed to have pinpoint axles slop around in them willy-nilly. So I've been experimenting, and the way I did this was to order a bunch of Reboxx wheelsets from Caboose Hobbies.

First off, may I just say how nice the Reboxx wheels look, which is my positive thing to say about the product. However, the sizes specified when buying said wheelsets are  less than ideal, because it became clear after measuring that the specified size was an indicator of the maximum length of the axle; not the size of the axle that one is going to get.

Okay, caveat, no manufacturer can supply perfect sized parts, due to manufacturing tolerances that inevitably arise as a part is being made. However, saying that one can expect that all the parts marketed as being to a specification will be within a few thousands of an inch. So then the question is how large is a few thousands of an inch?

Good question, so I look around at other bespoke model railway manufacturers and measured the lengths of their axles. I chose Exactoscale and found that all their axles were within a plus or minus range of two thou. So, for example about a dozen axles were  length X, and about four were two thou shorter, and about another four were two thou longer. Length X is irrelevant, as axle lengths are different for American versus British practice. This seems like a good spread, as the majority are al one length, and consistency is what one wants.

Good new is that Reboxx axles are more consistent than the NWSL wheelsets I had, having less outliers. Bad news is that the axles were all under size, just the same as the NWSL axles I have. So if you really want 1.015 axle for example, then buying the packet marked 1.015 will, I'm afraid to say, lead to disappointment. Furthermore, the replacement sizes recommended are less than ideal, since they do not address the main problem from the experiment of shaking the trucks to see if they rattle, and then checking to see how they roll?

Having bought a packet of each size of axle I thought I needed, or two in a couple of cases,  and having taken all the wheelsets out of all my freight car trucks, and measuring the axle lengths, I was able to do some experimentation.

Using a Kadee ASF Ride Control truck I changed out the 1.015 axles, which were in fact less than 1.015, and by trial and error fitted replacement wheelsets to fit;  until I had no rattle when shaking the truck, but still had a truck that would roll freely. What I found was that Reboxx 1.027 axles worked best in the Kadee ASF truck. Hopefully, this means that all the Kadee trucks that are stated as needing 1.015 axles will actually run with 1.027 axles (Andrews, Barber, PRR 2DF8 and Vulcan are said to all be 1.015 like the ASF Ride Control's).

Next I took the axles out of my ExactRail Barber S2 trucks and repeated the process. The original axles varied from 1.003 to 1.005, and I found that they would run with 1.012 axles.

Result is that I now have five freight cars on my layout with wheelsets that have axles long enough so that the trucks don't rattle when shaken, but the cars roll nice and freely. I also have a fifteen boxes of axles all sorted by length that by-and-large are of no use to me.

Plan B now involves selling all the axles I have and replacing them with ones that are longer.

Addendum: A big shout out and thank you to both Susan Parker of CLAG, and David Fouracre of The Tool Box for their considered input into this piece.

No comments:

Post a Comment