BR Wheel Rim (Disc) information.

[ClikC]

Hi All.

One of my ongoing niggles with the hobby is the lack of availability of steel wheels for various RTR conversions. That is not to say they don't exist, just I find that I don't get on with, or cannot obtain with ease, the wheels I want. My preference is for Kean-Maygib’s all steel wheels, as I find that these seam to provide my best conversion experiences. However, the coach wheels are scaled for 3'7 1/2". This is incorrect for 3'6" wheels employed on BR Mark 1 stock with BR1 and Commonwealth bogies. Alternative wheels on the market are only available with plastic centres, which I find difficult to obtain a reliable, square back to back with.

So I thought I'd have a crack at producing a range of my own wheels firstly as CAD drawings, before producing a limited run for testing and analysis on a CNC lathe.

Below is one of my efforts. A 14mm wheel mounted on a 26.5mm pinpoint axle, with two insulating bushings from Marklin (many thanks Ivan). The wheel flange and tyre profile is faithfully reproduced from the scaled BS 276 Contour A measurements from ScaleFour Digest 1.2 'P4 Track and Wheel Standards'. The tyre width is 1.92mm. I’ve aimed for as much steel in the wheel as possible, as I find the increased mass of the Kean Maygib wheels over other brands to be a major benefit.



However, I've hit a snag in terms of finding information on the wheel rims (discs) themselves. Not to be confused with the tyre that fits onto the rim.



I'm wondering if any members could point me in the direction of where I might find drawings for the wheel rims themselves? My current plan is to take a trip to the South Devon Railway on Saturday, armed with a straight edge, tape measure, steel rule and a Vernier calliper.

With some success I hope to also produce 4'0" wheels for the Class 85, followed by 3'9 1/2", 3'9" and 3'7" wheels for other classes.

Regards

Matt

[Tim V]

Looks very good, but 26.5? The standard is 26.00. Also can't help with the drawing.

I use the turned nickel wheels from Branchlines, the extra mass does give good running.

[Rod Cameron]

Looking good so far Matt, good luck with this.

[ClikC]

Looking good so far Matt, good luck with this.

Many thanks Rod, I hope to arrive with something tangible within the next month or so, no doubt I'll be wanting to test the fruits of my labours on the DRAG test track.

Looks very good, but 26.5? The standard is 26.00. Also can't help with the drawing.

I use the turned nickel wheels from Branchlines, the extra mass does give good running.

Hi Tim,

My first pinpoint axle was produced to a length of 26mm, as working to memory I believe most of the commercially available springing units are designed for 26mm axles, but browsing a number of pages in my hunt for information I found references to Bachmann and Hornby axles being 26.5mm in length. I have not dug out any 00 wheels, so I haven't measured to confirm this. Either way it takes seconds to modify in SolidWorks, and I'm not ready for 'production' as yet. My plan is to produce a range of axle solutions, so I hope to cover all bases.

I've a few of the Branchlines N/S wheels too, and found them to very good due to the increased mass and nearly all metal construction, with the minor dissatisfaction that they only come in Nickle Silver. Whereas steel on steel running is my ultimate goal.

No problem on the drawings, I consider it a long shot, as I've found very little information on the web. Although, it was with some interest today that I found a hint at perhaps why the rims are shaped the way they are. http://the-contact-patch.com/book/rail/r1610-the-wheelset "Figure 2
Bonatrans model 29 wheel disk shaped to allow for thermal stresses."

Please excuse my layman position, but I wonder if the design of the wheel rim curvature, is to allow some compression/ expansion of the wheel rim in conjunction with expansion of the tyre due to the temperatures generated by the clasp brakes. From a logical point of view, this wold make sense.

Hopefully another member maybe able to enlighten me further.

Regards

[Philip Hall]

Like Tim, I'm mystified about the references you've found to 26.5mm axles.

I have quite a few Hornby and Bachmann wheels here, having pulled them out of various vehicles, and having just measured six or so of each at random, I found that Hornby are between 25.7 and 25.75mm, and Bachmann (which seem to have sharper pin points) are between 25.95mm and 26.0mm. Whenever I have replaced Hornby wheelsets in carriages, I have almost always had to roll the bogies up and down the bench whilst pressing hard inwards on the axleboxes, a good way to slightly open up the bearings for a true 26mm pinpoint. This seems to bear out my measurements.

I am also a fan of the Branchlines wheels, also Ultrascale, but I have no problems with nickel silver.

Philip

[ClikC]

Thanks Philp, that’s saved me a job.

This latest variation on a theme, contains 26mm pin-point axles.



Regards

[Rod Cameron]

Many thanks Rod, I hope to arrive with something tangible within the next month or so, no doubt I'll be wanting to test the fruits of my labours on the DRAG test track.

Welcome any time Matt, second and fourth Mondays in each month as usual.

[ClikC]

Hi all,

Bit of an update, as I found myself free on Thursday I took a trip down to the South Devon Railway at Buckfastleigh, where I hoped to find some wheels laying about.

And boy, did I hit pay dirt!



Ten quarantined 3'6" disc wheels, including these four from a Commonwealth bogie. I measured the tyre thickness on the set, and selected the wheelset with the thickest tyre and took a crude circumference measurement to confirm the wheel is at least 3'5" in diameter. I also employed some very Heath Robinson methodology to measure the front facing dish of the disc.

I've spend a few hours working with my recorded measurements, and while very crude, I was able to produce something which has turned out a lot better than I expected.






I've increased the hub of the wheel, as the prototype is a little wider than the tyre, presumably this is to assist in keeping the wheel Perpendicular to the axle, from my experience a common cause of running issues in model form. The dish isn't as smooth as I would have liked, this is due to my crude measurements not giving the perfect tangentially joined radii. I think another visit is required, after I’ve knocked up some kind of jig measuring tool. But regardless, I'm quite pleased with the result at this early stage of CAD drawing work.

Welcome any time Matt, second and fourth Mondays in each month as usual.

Excellent, I'll wing you a pm to confirm when the time comes.

Regards

[ClikC]

Hi all,

Another update, a RMWeb member contacted me, and kindly forwarded me a copy of a official British Railways drawing of a 3'6" carriage wheel with axle for a BR1 Bogie. I won't reproduce that drawing here, as the copyright status of the drawing is unknown.

First port of call was to reproduce the wheel to dead scale.







I also reproduced the journaled axle, to produce a dead scale assembly.






At 4mm scale the thinnest part of the disc is only 0.27mm thick. So with that in mind, I set about making some alterations to the model, to make it more suitable for P4.





The details on the rear face of the wheel have been removed, in order to increase the mass of the wheel, and to thicken up the disc itself. The tyre has been increased in width to a value of 1.77mm (an increase of 0.1mm) to take into account the decrease in Back-to-Back of P4 in comparison to the prototype. All mounted on a 26x2mm pinpoint axle. The front face of the wheel has been brought forward by 0.1mm, so all features on the front face are still to scale. The thinnest part of the disc is now 1mm thick.

Unfortunately, the 2mm ID 3mm OD insulating bush from Marklin is much wider than the hub of the wheel, and so fowls the pinpoint. I may increase the boss on the back of the wheel to accommodate this, or simply trim the bush. Another option is to reduce the diameter of the pin point axle to 1.5mm, with which a more suitable insulating bush from Marklin may be used. The boss on the back of the wheel is a little tricky to machine, and I would like to avoid two separate machining operations on the wheel if possible, but this may be an option for more high-end CNC machine.

I've e-mailed Serco Rail Data, as I understand they currently hold the British Rail Board drawings for many items of post 1960's rolling stock, still in operation in one form or another, on the network today. Although, judging by the attitude of the woman I spoke to on the telephone, I'm not holding out much hope. I'd like to source drawings for the wheelsets as fitted many of the Locomotive Classes I'm interesting in, and give those a similar treatment to the Mark 1 wheel seen in this post.

Regards