Holding on to the Axle

We’ve now seen that even reliable old Percy can lose the grip between axles and wheels when things get rough. I’m driven to ask what exactly is the best way to connect the wheels to the axles so they don’t slip?

There are plenty of scale locomotives running around with an interference fit between wheel and axle, and many of these have plastic wheel centres, especially in Britain. #10 was built this way, with EM Gauge Society split axles and Mike Sharman’s Millimetre Range wheels, and should still be running like its similarly-constructed brethren. Yet it isn’t. Perhaps the very air in Britain is special. Maybe that would explain how that island has produced Cornish pasties, The Two Ronnies, bagpipes, and now wheel centres that stick. So to be clear, I am looking for a method of attaching drivers to axles so that they not only maintain their quartering, but so that they maintain their quartering for me, here in North Vancouver, where the air only produces Bannock Burgers, Douglas Coupland1, Bryan Adams and wheel centres that don’t stick.

It’s time for a little science! Maybe very little. In fact, I’m not sure this would pass muster in my kids’ high school science classes, but I have only so much energy to apply to pure research.

I devised an experimental setup involving clamps, a scrap of brass that pressed over a hex-shaped test piece representing the wheel centre, some incredibly strong dental floss, and a ginger ale bottle full of coins. My son, who knows exactly what high school science experiments require blanched in horror when he saw this apparatus. However, remembering that they laughed at Newton, I pressed on and tested four methods of holding onto a slippery stainless steel axle:

  1. Interference: a 3D printed wheel centre pressed onto the axle with a press.
  2. Capillary CA: The same interference fit centre, pressed on and CA applied through capillary action. This mimics a likely scenario of rotating the wheels into quarter and gluing after becoming happy with the running.
  3. Printed key: A .009″ key 3D printed as part of the wheel centre that engages in a slot cut in the end of the axle. The key thickness matches the slot created by my jeweller’s saw.
  4. Solder: Soft solder flowed into a machined brass centre.
Failure weights (g)Trial 1Trial 2Trial 3Trial 4Average
Capillary CA214296279263

I weighed the ginger ale bottle at the point when the joint failed completely. The Capillary CA joints, in particular, collapsed slowly, rather than spilling all the coins on the floor at once. The soldered joints failed to break before running out of coins and room in the ginger ale bottle.

The lever arm is 2.5 cm long, and I suppose I could calculate the torque applied in each instance, but that is not as interesting as the relative strength. Obviously, for maximum strength, solder is the winner. However, that adds to the complexity of wheel construction. The Key also adds complexity, but it is probably manageable. It would be great if an adhesive, especially one that allows for adjustment, could exhibit strength similar to solder or even to the key. I have a few more to try.

1 Actually, I think Douglas Coupland might be from West Van, but ignoring real estate prices, it’s basically the same place.

2 The alignment on this trial was poor, giving it a slight advantage over the other three. Discarding this result, the average is 214g.

8 thoughts on “Holding on to the Axle

    1. Yes, it’s on the list. I was re-reading Guy Williams’s book last night and noticed that he used LocTite 601, but referring to their website, it looks like 290 would be better for my purpose. I have some Rite Lok RT41, which looks similar to 601. Next is sourcing…

  1. Rene, Loctite makes a wide range of adhesives for bonding things to shafts in a selection of strengths and “removability”. I seem to recall, perhaps incorrectly, that a SS axle may need a pretreatment spray to activate its surface for a Loctite to reach is ultimate design strength.

  2. I guess my question would approach the problem from a different angle. What is causing the axle and wheel to slip? As you’ve discovered, the quartering is binding because the driving rods are forcing the axle and wheel to slip as it comes out of quarter.

    The axle and the wheel can slip all day long on non connected drive wheels (cracked axles anyone, famous in various scales), but once they are connected via a driving rod that’s when issues arise.

    Forcing the axle and the wheel not to slip (say a solid wheel/axle one piece combination) still isn’t going to solve why the quartering issue is only present when you run it on the layout vs on the bench (haven’t your quartering issues all happened once the locomotive runs on the layout?).

    From my perspective it seems like the quartering and therefore slipping of the axle/gear is a symptom of something else, were as your perspective is that the axle/gear interface is causing the issue.

    I could be completely wrong, but I really hope that you can figure out the root cause of all your issues.


    PS, the Loctite Red was used in my scale by Aristocraft trains to fix a axle/wheel interface issue. It’s removable with heat but otherwise permanent.

  3. Couple of thoughts. First, can you design the axle and wheel to accommodate a sliver of steel (ex. fine piano wire?) as the key. Second, (kine of the same thing Craig wrote about) I was wondering what is causing what – a) drivers going out of quarter causing things to jam or, alternatively, b) something else pushing the drivers out of quarter and causing the jamming up? If the only reason things jam is that the drivers go out of quarter, then preventing the drivers from rotating on the axle makes sense. But, if the drivers go out of quarter due to the operation of some other force, then I wonder whether preventing the drivers from going out of quarter might end up breaking something else.

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