Little & Large - The Socially-Distanced Challenge

andrewnummelin
Posts: 288
Joined: Mon Jul 21, 2008 9:43 am

Little & Large 10 - The Socially-Distanced Challenge

Postby andrewnummelin » Fri Nov 06, 2020 12:49 pm

Is half of my challenge complete?

Little

All that's left to do now is the lettering, weathering and testing!
little and large 036.jpg

I prevaricated a long time about wheels as I hardly ever use my lathe, and am really a poor novice. In the end I decided it would be easiest to try in brass - I was pretty sure that using a form tool to cut the profile would not work on my Unimat 3; but I had a go just to confirm that the machine was simply not powerful enough. So I took a different approach as illustrated below.
Firstly a bar was turned down to 12.5mm diameter, just larger than the 12.3 final target. Then, with the top slide set at 3º, the tread was cut, with a width just over 1mm, to a diameter of 11.6mm (the dimension scaled from the drawing rather than the 12mm that I initially assumed).
little and large 025.JPG

Then, with a parting tool, a groove was cut to just less than the tyre tread diameter.
little and large 026.JPG

The flange was then cut with the form tool, stopping when it just rubbed the tyre tread.
little and large 027.JPG
little and large 028.JPG

The tyre was faced to the final width (1.25mm), and the bar drilled in stages to 8mm diameter, being the largest drill that would fit the chuck. A boring tool was used to open up the centre.
little and large 029.JPG
little and large 030.JPG

The target diameter was 10.7mm so as to accommodate the printed centre that I had measured as being 10.67mm diameter - testing was by trial fitting rather than measuring.
little and large 030.JPG
little and large 031.JPG

The tyre was parted off and the back rubbed down on a file until smooth. This was repeated three times to make 4 tyres, then the centres were fixed with super glue. A couple of tyres have subsequently come loose and have needed re-glueing so I'm not sure if I used the optimum approach.
little and large 032.JPG

The centres had been printed with a nominal 0.9mm axel hole so this was drilled out (by hand) to 1mm and the wheels were fitted to the axels and fixed with Loctite 603 whilst held in a back to back gauge.

The wheels were fitted to the wagon and I was very pleased to find that they were just small enough not to foul the spring carriers and rotated freely.

Because I'd had two slightly different wheel centres printed, and I prefer the look of steel, I decided to have a go using the same approach with a steel bar. This went fairly well but I did find it more difficult to get a good finish: it was difficult to see exactly what I was doing as the chips did not clear easily as I was using cutting oil brushed on as a lubricant.
little and large 033.jpg



Here's a comparison of the various wheels, a standard P4 set, the thinned down P4 ones originally tried, the brass tyred one (now blackened) and the steel ones. The nylon print finish looks rather rough but is fine when viewed from a few inches away.
little and large 034.JPG


But not all was perfect: a couple of the wheels wobbled a bit which could be critical being so narrow. When checked with a back to back gauge nothing seemed amiss and a bit of tweaking could get them to run OK. It is clear that the very fine spokes are a bit flexible so things may seem fine when pushed onto a back to back gauge but I fear they may relax when removed. Perhaps I had not been careful enough when drilling the axel holes - with hindsight I think it would have been better if the centres had been fitted to the tyres and the axel holes drilled while still in the lathe. I hadn't done this as I was concerned that the spokes might not have been strong enough to survive drilling on a machine. The second problem was caused by my forgetting one thing and not looking carefully enough. Some of the wheels derailed when run along a bit of straight track! Examination with a magnifying glass revealed a slight burr on the edge of the tyre where it had been faced off and this was catching on the rail - I had forgotten to chamfer the edge of the tyres! I went round the edge of the tyres with a fine file and whilst not an ideal procedure seemed to solve the problem. The wheels will roll down a bit of straight track and stay on! At the moment I only have a bit of straight track on the test bench and with lock-down there's no chance of taking the wagon to a layout to see if the wheels are OK for normal running. I can't have been working to high precision using only a vernier and eyesight - did I achieve adequate consistency?

So with the wheels fitted it was on to doing the last bits. Fitting axel boxes & springs (commercial castings), the remaining iron work to secure the tubs (will they survive just glued on rather than pinned?), axel box ties (simply round wire rather than properly shaped), straps round the buffers and crown plates (not on the drawing but possibly used in reality). The brake was fitted with an arrangement that would work in a more conventional way that shown in the drawing, but I did stick to just the simple catch for the brake lever as shown rather than a normal lever guard. As drawn and modelled the brake could only be held on by someone leaning on the lever or possibly sticking a sprag in the W iron.

The wagon and tubs were painted plain black as I guess this was most likely. I'm now debating whether to use a known, more modern livery, or simply use an old name and made up numbers. I assume the wagon and the tubs would have had to have had their owner's name on them.

I thought it interesting to compare the wagon with the normally advised weight for reliable running: I expect this model might well bounce off the average model railway trackwork as it weighs only 6.5 grams - the two tubs come in at 3.5 grams. I've worked out that I can probably get around 7g of lead in the chassis. With this, will the wheels stay on the track? How will such narrow wheels behave on a common crossing? Time will tell!

To emphasise its small size, here's a comparison with a couple of more common coal wagons.
little and large 035.JPG


Large

This is also progressing: the bogies have been assembled, brake blocks fitted (a terrible fiddle) and axelboxes added - thanks to Justin of Rumney models who had a few lovely castings spare that he was able to supply. It is now impossible to remove the wheels from the bogies as there is insufficient flexibility and the bearings are glued in rather than being allowed to drop out. Even if I had allowed for removable bearings, two axels would still have been trapped by the brake blocks - I didn't even consider making hinged hangers! The bogies have now been fitted to the wagon with the suspension beams held in place by temporary pins until some proper trials can be done on a layout.
It took three attempts to make the stanchions: initially I tried turning down brass bar but this flexed too much and I found it impossible to make it parallel. I then tried steel and, whilst more rigid, this also flexed and and I broke a couple while trying to turn the shoulder. So I decided to try some 0.9mm wire with a tiny bit of 2mm soldered over it that could be turned down to form the shoulder. This worked fine and the photo shows a couple fixed in place and another couple stowed along the solebar. The stanchions were probably secured to the wagon by a small bit of light chain but I've chickened out of trying to do this on the model!

A brief test showed that the wheels of the centre bogie did foul the plates under the wagon where the drawing was marked "pocket cut away and splasher fitted where wheel occurs". However instead of making a splasher, I simply bent the plate upwards out of the way. Very fortunately this bodge is not visible through the holes in the top of the wagon so saving some very tedious and fiddly work!
little and large 037.jpg

What's left to do is the fitting of the brake operating gear, adding cosmetic rivets and the label pockets to the solebars, painting and lettering. And, of course, a trial on curved track to see how the bogie suspension performs - twiddling the bogies by hand suggest that only large radius curves will be negotiable.
Regards,

Andrew Nummelin

Philip Hall
Posts: 1582
Joined: Mon Aug 10, 2009 7:49 pm

Re: Little & Large - The Socially-Distanced Challenge

Postby Philip Hall » Fri Nov 06, 2020 8:06 pm

Andrew,

Very interesting how you decided to do most all of the turning to produce the wheel with normal tools and only fettled the flange with the form tool. I suspect this is the approach I will use when the Society form tool is produced. I can’t produce a taper easily with my Unimat SL so think I might use a tool I made up years ago to true up a Sharman wheel which just has the taper of the tread and the radius between tread and flange.

I don’t think any kind of superglue is strong enough for gluing tyres on. A while back I thought I’d try and save time by using Hafixs to glue tyres back on some trued up centres. It just didn’t last and there was no time for adjustment. So I went back to my usual Devcon 5 minute epoxy which has been completely successful. It’s quite thin, but still stiff enough to stay put and fills gaps very well.

Philip

andrewnummelin
Posts: 288
Joined: Mon Jul 21, 2008 9:43 am

Re: Little & Large - The Socially-Distanced Challenge

Postby andrewnummelin » Sat Nov 07, 2020 9:08 am

Philip Hall wrote:Andrew,
..

I don’t think any kind of superglue is strong enough for gluing tyres on. A while back I thought I’d try and save time by using Hafixs to glue tyres back on some trued up centres. It just didn’t last and there was no time for adjustment. So I went back to my usual Devcon 5 minute epoxy which has been completely successful. It’s quite thin, but still stiff enough to stay put and fills gaps very well.

Philip


I did consider epoxy but thought there was a risk of it ending up filling the tiny gap where the spoke meets the rim. Maybe the answer on any future project would be to rivet (pin) through the tyre. Not illustrated on the original drawing, but certainly not unknown at the time!
Regards,

Andrew Nummelin

Philip Hall
Posts: 1582
Joined: Mon Aug 10, 2009 7:49 pm

Re: Little & Large - The Socially-Distanced Challenge

Postby Philip Hall » Sat Nov 07, 2020 3:55 pm

Andrew,

I think Devcon is thin enough to be able to just have a smear on each segment of your centres and then to push the rims on. I normally push the rims on whilst the centre is still in the lathe so I can check that it doesn't wobble. If any glue did stray I think it would be simple to pick it off with a cocktail stick after it's started to go off.

Philip

davebradwell
Posts: 415
Joined: Fri Jan 18, 2019 3:48 pm

Re: Little & Large - The Socially-Distanced Challenge

Postby davebradwell » Sun Nov 08, 2020 9:08 am

Full marks for having a go at making fancy wheels but it's troubling that the design of the form tool seems to waste 3 times as much material as you use - can't you grind off the LH side, possibly at an angle just to be more economical. I hope the new Society tools won't repeat this problem......or am I missing something? Might I also suggest you try to have less tool sticking out of the holder. The tip should be as close as practical to its holder without risk of hitting the chuck. It makes a difference on my half ton lathe so it will on your Unimat. Personally I'd just set a tool to give a 68deg straight flange then part off, pausing to round off the flange tip and chamfer front corner. Form tool seems redundant unless you make plain rings first then mount each for a single plunge.

As I understand things, superglues are unsuitable for fitting tyres because they will go off as you start to put the tyre on.

You should be able to make wheels run true if you're careful when drilling and fitting - wouldn't your 0.9 hole give a press fit or did it come out different size? Method will depend on what equipment you have, of course. I press wheels on in a pillar drill.

DaveB

andrewnummelin
Posts: 288
Joined: Mon Jul 21, 2008 9:43 am

Re: Little & Large - The Socially-Distanced Challenge

Postby andrewnummelin » Sat Nov 21, 2020 2:49 pm

Philip Hall wrote:Andrew,

I think Devcon is thin enough to be able to just have a smear on each segment of your centres and then to push the rims on. I normally push the rims on whilst the centre is still in the lathe so I can check that it doesn't wobble. If any glue did stray I think it would be simple to pick it off with a cocktail stick after it's started to go off.

Philip

A lesson for next time! Thanks.
Regards,

Andrew Nummelin

andrewnummelin
Posts: 288
Joined: Mon Jul 21, 2008 9:43 am

Re: Little & Large - The Socially-Distanced Challenge

Postby andrewnummelin » Sat Nov 21, 2020 2:54 pm

davebradwell wrote:Full marks for having a go at making fancy wheels but it's troubling that the design of the form tool seems to waste 3 times as much material as you use - can't you grind off the LH side, possibly at an angle just to be more economical. I hope the new Society tools won't repeat this problem......or am I missing something? Might I also suggest you try to have less tool sticking out of the holder. The tip should be as close as practical to its holder without risk of hitting the chuck. It makes a difference on my half ton lathe so it will on your Unimat. Personally I'd just set a tool to give a 68deg straight flange then part off, pausing to round off the flange tip and chamfer front corner. Form tool seems redundant unless you make plain rings first then mount each for a single plunge.

As I understand things, superglues are unsuitable for fitting tyres because they will go off as you start to put the tyre on.

You should be able to make wheels run true if you're careful when drilling and fitting - wouldn't your 0.9 hole give a press fit or did it come out different size? Method will depend on what equipment you have, of course. I press wheels on in a pillar drill.

DaveB

I don't trust my skills on a grinding wheel to reduce the tool size without risking destroying its temper. I'd rather waste a bit of bar metal!
Yes, I certainly should have had the tool mounted better.
The printed hole did come out a little undersize and I should have done the job of mounting the wheel on the axle with more care - a lesson for next time!
Thanks for the advice.
Regards,

Andrew Nummelin

andrewnummelin
Posts: 288
Joined: Mon Jul 21, 2008 9:43 am

Re: Little & Large 11 - The Socially-Distanced Challenge

Postby andrewnummelin » Sat Nov 21, 2020 4:24 pm

The challenge is "complete".

Little

Now lettered (imagined, but Thomas Powell did have this type of wagon), weathered and lead sheet added, so there's nothing more to be done for the time being other than retiring to the armchair and wondering if I should plan to make a rake of similar wagons. However I'm put off by the thought of having to couple them up to make a train - it might be better to think about going further back in time to have wagons coupled by a simple bar rather than chains. (See part 3 of Michael Lewis's "Steam on the Sirhowy Tramroad and its Neighbours".)


Large

So the final details have been added, brake gear fitted (so trapping the bogies) and the wagon painted. The lettering may be temporary - the G.W.R plates came from a plastic kit but the rest of the lettering is by hand made transfers. These are decidedly sub-standard and I hope to eventually do something better: an etched number plate is a possibility, probably as a spare bit of some future etching project. The load and tare lettering may be more of a challenge - I have some commercial GWR trasfers on order but I suspect that this wagon may need bespoke lettering so as to fit the restricted spaces available.
The wagon runs very nicely along my 35cm of test track and the bogie suspension allows it to bump over small obstacles smoothly. The remaining armchair exercise now is to discuss with myself whether to add a chained down load, or simply chains (stored in the pockets?), or leave it unloaded - I enjoy prevarication!

little and large 038.jpg
Regards,

Andrew Nummelin

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David B
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Re: Little & Large - The Socially-Distanced Challenge

Postby David B » Sat Nov 21, 2020 4:56 pm

That is very nice, Andrew. It was a heavy vehicle and your model conveys that weight - it has 'presence'. It has been very interesting following the creation of the wagon. Well done.


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