16T Minerals

[Hardwicke]

I'll check the bearings, but I did see the axles varied by at least 1mm. I've no idea which make, though I can usually identify PC, Studiolith, Maygib and Exactoscale.
Perhaps some lathe work...

The thought just occurred - rather than trying to replicate the coning on the ends of 2mm rod, since the manufacturers appear to be having so much difficulty with accuracy, would it be easier to cut the axles and sleeve them to fit?

Ted.

Do you mean have them plain with inside bearings ?
I hadn't planned to as I have just bought some new society w irons

[grovenor-2685]

No, he means to allow easy adjustment of the axle length without messing up the pointed ends. I have done this to reduce the length for 3'6" gauge.

[Will L]

The thought just occurred - rather than trying to replicate the coning on the ends of 2mm rod, since the manufacturers appear to be having so much difficulty with accuracy, would it be easier to cut the axles and sleeve them to fit?

Yes if you don't have a bearing axle combination that wont fit between the W irons, but in my. i accept relatively little experience, and using a very varied set of bearings (as has Hardwick by the sound of it) I could usually find a match, and coming up short was quite as likely as being over long. If undersize all you need to do is pad the bearings out a bit. (some of?) Masokits W irons come with little washers just for this job.

[Hardwicke]

No, he means to allow easy adjustment of the axle length without messing up the pointed ends. I have done this to reduce the length for 3'6" gauge.

I see.

[Hardwicke]

I'll look in my box of metal bars and rods. I could pop an old axle in the lathe for practice.

[Martin Kelly]

I bought the correct axles irons at Wells. Should the axle irons have one or two holes in them? A quick check on Paul Bartlett's site shows predominantly one.

It varied. One, two or even no holes in the plate axleguards all occurred on the real thing. Based on my own observations and examination of photographic evidence, one hole (on the outer end - i.e. nearer to the headstocks rather than the v hanger) seemed to be the most common configuration. As usual, the best advice is to model specific wagons if you have access to photographs of them.

On your other query about the length of axles being inconsistent (even by fractions of mm), I ended up bypassing the whole issue with pinpoint axles by opting to standardise on parallel-ended axles and appropriate bearings. I tend to use the excellent Rumney Models PE brass underframe kits and the frets for these come with spacing washers to help deal with slideplay/slop.

[zebedeesknees]

No, he means to allow easy adjustment of the axle length without messing up the pointed ends. I have done this to reduce the length for 3'6" gauge.

Thanks Keith, yes. Another idea is to use the very low price 1x3x1mm ball races from China, with 2mm o.d. tube and 1mm rod. Even better would be a batch of 2mm axles with 1mm parallel ends of a suitable length - too long rather than short so that the user could finish to the desired length if required. A 3D printed bearing carrier for proprietary W-irons...

Ted.

[grovenor-2685]

Length is the main problem with the Exactoscale 1mm axles, IMHO. But its not so hard to get hold of 1mm rod and cut your own.
Prototype axles for outside bearings are made to suit bearings on 6'6" centres, which geves a minimum axle length of 7'. 28mm in our scale so 25mm is not enough.
The pinpoint standard of 26mm was intended to carry the weight, which would always be at the end of the pinpoint, on the prototype bearing centre line.

[zebedeesknees]

Length is the main problem with the exactoscale 1mm axles, IMHO. But its not so hard to get hold of 1mm rod and cut your own.

Exactly, and fine and dandy with brass tube, but..
Brass in inside bearings such as when a gearbox is required on that axle is not a good idea with a brass axle, and the only steel tube I have found is stainless and a pain to cut accurately.

Prototype axles for outside bearings are made to suit bearings on 6'6" centres, which geves a minimum axle length of 7'. 28mm in our scale so 25mm is not enough.

Quite, I don't know who mentioned 25mm, I didn't specify a dim. My ideal would be bms, 22mm @ 2mm, with 1mm extensions of 3.5mm length.

The pinpoint standard of 26mm was intended to carry the weight, which would always be at the end of the pinpoint, on the prototype bearing centre line.

Hence the dissatisfation and discussion.

Ted.

[grovenor-2685]

25mm is the length of the Exactoscale plain axle.

[Will L]

...The pinpoint standard of 26mm was intended to carry the weight, which would always be at the end of the pinpoint, on the prototype bearing centre line.

Hence the dissatisfation and discussion.

Given that a pin point bearing is most unlike a real prototype parallel bearing I'm really unclear to me why we are so concerned with preserving, or for that matter taking much notice of, the prototype bearing centre dimension. Fitting axle and the bearings so that the W irons remain vertical is the key issue. Pinpoint bearings will always apply a slight sideways force on the W irons which must be resisted but exactly where the contact point works out to be in relation to the plane the w irons are in doesn't seem to be particularly material. If we have to recess or pack out the bearing to fit the axle, do we care?

[davebradwell]

In reality the cone on the axle starts very close to the wheel boss so axle couldn't be made much shorter or the wheel would be sitting on the coning. With bearings at the deeper end of the spectrum, they come pretty close to the wheel already. Of course our wheels are significantly thicker than scale wagon wheels.

DaveB

[Guy Rixon]

If we were to change things, I'd vote for shorter axles with pinpoints in line with the axleguards, and shallower cones in the bearings. This gives three advantages. We bring the bearing interface nearer the axis of working springs inside the axleguard and reduce the turning moment on the bearing carrier. We reduce the need to hollow the axlebox. We reduce the degree that the axleguards are bent to spring in the wheels, hopefully keeping the flexure inside the elastic limit.

The axles in 2FS are 12.25mm, with minimal cones in the bearings. I'd like to see that scaled up by a factor of 2.

[davebradwell]

You'd need a smaller diameter wheelseat then, Guy, to reduce the length of the axle cone which is currently 1.7. Whether the reduction in the offset of the forces by 0.75 - about 6 degrees - will make a difference is a matter for speculation.

DaveB

[Guy Rixon]

Dave, my preference is the Exactoscale approach with 1mm functional axles sleeved between the wheels for appearance sake. To simplify production for hypothetical, factory-assembled wheelsets a la AGW, how about axle ends turned down to 1mm outboard of a 2mm wheel seat and coned at the traditional angle?

I agree that the turning moment on the bearing is (probably) not a problem. It is, however, something I'd minimise if I was designing from scratch. Which I'm not, beyond the beermat stage, as I lack the tooling to make these things.

There's another issue that could be eased. When using "waisted" bearings, the length of engagement of the 2mm parallel bit with the axleguard, which keeps the wheels aligned, is comparable to the lateral slop if the axles are too short. If a bearing moves inward the axle can twist and then the bearing tip catches inside the axlebox, jamming the suspension. If I pack the bearings to remove the slop, then the parallel part of the bearing has retreated inside the axleguard and it still twists and binds. I need bearings with a greater parallel length, but tapering more abruptly outboard of this. I can make these from non-waisted bearings by filing, of course, but it would be nice if they could be bought in the "right" shape.

[davebradwell]

Yes Guy, some details of wheel/axle assembly would certainly need changing - do the 2mm folk turn the p-p on the wheel?

I'm with you 100% on the waisted brgs. They're usually ok as long as the axleguards provide a snug fit but as soon as a 0.3 washer is required there is no guiding spigot left - a 0.15 washer is just about acceptable. I've been filing the standard flanged ones down for years but it seems so unnecessary. Wonder why they are so long as the cone doesn't come anywhere near the end.

DaveB

[Guy Rixon]

Yes Guy, some details of wheel/axle assembly would certainly need changing - do the 2mm folk turn the p-p on the wheel?

In my experience (dating from ~10 years ago now), no, the 2FS wheels are moulded centres with steel tyres pressed onto a 1mm steel axle. The cone starts at the wheel face.

[davebradwell]

I'm struggling to get it - a P4 wheelset is 21.75 over tyres and 2 off 60 deg cones at 1.73 (root 3) gives a minimum axle length of 25.21. Where are they gaining the extra space or where have I gone wrong? A 2mm scale wheel must be wider than 1mm anyway. A steeper cone angle would account for it - 72 deg would make your 24.5 axle fit but that wouldn't be a good thing to do as. it would increase the outward pressure.

DaveB