2mm axle length

[Andy W]

I've not built much 4/6 wheel stock so this might be a stupid question - but why are 2mm axles so short that the bearings have to be packed out to prevent a sloppy fit? Is this a legacy from OO days? Does anyone produce longer axles? Or have I simply not understood a basic principle here?
Thanks,
Andy

[grovenor-2685]

The standard length for pinpoint axles is 26mm, this should fit nicely in most 4 wheel stock if the W-irons and axle boxes are at the correct spacing. Packing out suggests that the axleboxes are to far apart. What type of chassis are you having the problem with?

UK prototype wagons generally had the centres of the journals at 6ft 6 in centres, and these should come under the springs and hence the solebars. The 26 mm axle ends should be at this same place which puts them approx. 2mm in from the back of the axlebox and should not involve any packing out.

However not all kits or RTR stock are built to the correct dimensions and you need to check what you have annd decide if remedial action is needed, whether to do it by packing out or similar or by a more thorough rebuild.
Regards
Keith

[Andy W]

Thanks Keith. I'm building a Roxey kit of a 4 wheeled SECR Grande Vitesse Luggage van. It has fold up w irons from the floor etch, and when the bearings are inserted into the etched holes the axles are retained in the bearings - but there's a fair amount of slop - which I assume for S4/P4 should be eliminated?

The kit is well etched and designed, and this question is in no way a criticism of it. It's more a reflection on my lack of experience in this field.

Thanks again,

Andy

[grovenor-2685]

Certainly you don't want significant slop, there are essentially three measurements involved here and if all the tolerances are adding together it can end up as excessive and needing remedial action.
Do you have a caliper to measure with? If not you probably should get one, the 6 inch electronic ones are often on cheap sale from the likes of Aldi these days and for much of our work the simple 6 inch plastic ones are fine.
Anyway, first thing is to measure the three components then you know what you are dealing with.
1. axles should be 26 mm over the pinpoints, if they are short by how much?
2. W-irons when vertical, what is the distance between the inside faces? Ideally it should be 24 mm
3. Depth of conical hole in bearing, should be 1.25 mm, but often isn't.
Measure this using a pin or needle through a cork, press the needle back into the cork till the bearing flange is touching the cork, the calipers can then be used to measure how much of the needle is protruding.

See http://www.clag.org.uk/bearing-interface.html for more on this.

If the problem is with the W-iron spacing it would probably make sense to replace them with sprung W-irons, long wheelbase 4 wheelers do not usually run well with rigid suspension.
Regards
Keith

[Andy W]

I ran a vernier over the various elements. The axles were a tad too short, and the w-irons were a tad too wide. To compound both I suspect I hadn't bent the w-irons at a true right angle. I also used waisted bearings - which I don't think helped.

Thanks for the advice and info Keith.

Andy

P.S. The kit comes with the option to build one rocking axle.

[grovenor-2685]

Waisted bearings shouldn't make any difference, they should be the same inside! But you only really need those for springing when you need clearance inside a fixed axlebox. The standard bearings will hold the axleboxes in place better.
Some of the Masokits etches have a bearing depth gauge built on the etch that allows you to sort them by depth and then chose the depth you need. Surprising how much variation you find.

You should be OK with a rocking axle, what sort of layout is it going to run on?
Happy new year
Keith

[Andy W]

"....what sort of layout is it going to run on?"

Keith, I can't ever see myself building a layout, both trackwork and electrics remain black arts to me. However, problems like the one above shows how useful having a test track would be to check stock etc as it's being built. And that's one of the beauties of this hobby - there's always something to be learnt. Thanks again for your help, this site is a great source of inspiration and aid.

Andy