Making a wheel profile tool - testing the tools.

The proof of the pudding is, as they say, in the tasting. So the first job to do after the forming tools were finished (see here) was to turn a pair of wheelsets.

My usual method is to turn a wheel using a turning tool leaving .05-.1mm on all diameters, then relieving the back face with a parting-off tool;

Then a forming tool can be used to finish the wheel off;

Once the profile is formed I drill and ream the centre then part off.

Here's the results;

And fitted with stub axles and an acetal muff;

The surface finish isn't great on either set, and I'm a little unsure about the profile on the Code 72 pair.

I've left these as they have come off the machine with no polishing.

I've fitted the 2FS pair on a muff set to the normal 2mm standard gauge back to back, I have however made a second muff machined to modified 2FS standards for 6mm gauge.

Have I been successful? I'd say yes, even if the Code 72 tool doesn't live up to expectations, I've learned a lot and pushed myself (and the machine). I may end up remaking the Code 72 tool, but first I need to test both tools properly.

The next step will be to build a pair of locos, one to 009 and the other to 006, then I'll know whether I'm happy or not.

Paul.

Making a wheel profile tool - turning the forming tool.

 Now that I had a pair of masters (see here) I could use them to make the forming tools themselves. Like the masters they're made from 16mm dia. silver steel.

The first job was to turn the outside diameter, just to true it up, then with the master tool set to centre height it could be plunged into the rod about 1mm from the front edge until the full form is below the outside diameter of the bar. This is the 2FS tool being formed;

Note the cutting compound, I used the type for tapping and dieing, which I'm not sure was the best choice. The work was turning using the slowest speed possible, and the finish wasn't as good as I'd hoped, the metal tending to tear rather than cut, especially on the wider Code 72 tool. A larger machine would have been a better choice, I felt that I was pushing the Unimat 3 to its limits on this job as far as rigidity was concerned.

I set the toolpost to sit on the right of the saddle whilst doing this, this way all of the force is going straight through the saddle;

When I turned the Code 72 tool I drilled a centre hole and used my rotating centre to help cut down vibration, this was because the code 72 tool is wider than the 2FS one and therefore puts more strain on both the machine and the workpiece;

Once the formers were turned they were both drilled out to 5.1mm, then cut/parted off before being turned to length using a watchmakers step collet leaving 1mm either side of the form;

The next stage followed the same pattern as the master, that is to file out a notch to make a cutting edge, stone the edge until smooth, and then harden and temper both cutters.

Here's a photo of both tools, mounted in the same holders that I used for the master tools.

Now I needed to test them both.

Paul.

Making a wheel profile tool - turning the master.

Despite owning several wheel profile tools bought from eBay I thought it might be fun to make my own. First of all I did some research, and found this article on the Manchester Model Railway Society website. The gist of it concerning making the profile tool is; turn a wheel to the correct profile in silver steel, convert that into a cutting tool, use that tool to cut a negative profile into another piece of silver steel, convert that into your forming tool. Silver steel can be easily worked then hardened and tempered making it ideal for making cutting tools.

I decided to make two tools, one to 2mm Finescale standards and one to NMRA RP25 Code 72, to cover both my 009 work and any future delving into 006. The relevant standards can easily be found online.

First of all I aquired some 16mm dia. silver steel, and turned the end to the basic dimensions of the wheel;

Then the 3 degree tread cone angle was turned, using my compound slide. There are two ways to get the correct angle for the flange (about 20 degrees), either by setting the turning tool to an angle to cut the flange angle at the same time as the tread is being turned, which is what I did on the 2FS wheel, or using the compound slide set to 20 degrees as shown below on the Code 72 wheel;

Once the basic form was finished a 5.1mm hole was then drilled in the centre and the wheel cut or parted off. Then using a watchmakers step collet the back face could be faced to length;

A simple mandrel was used to hold the wheels so the flange could be rounded off with a file and the wheel polished to a fine finish;

Both wheels ready to be made into cutters;

A centre line was scribed onto the back face and a cutting edge filed to just below the centre, to give some cutting rake (clearance);

Once I was happy with the shape the edge was ground, starting with fine oilstones and finishing with an Arkansas stone;

Then both cutters were hardened, by heating to bright red with a blowtorch and quenching in water, then tempered in the kitchen oven set to 200 degrees for 45 minutes to an hour. I then tickled up the cutting edge again with the Arkansas stone.

To use the cutters I made simple holders from 8mm square steel, drilled and tapped M5.

The next step will to use these masters to make a pair of forming tools.

Paul.

A new motor for my Unimat 3.

I've bit the bullet and bought a replacement motor for my Unimat 3. The original motor, despite being repaired a couple of times had a habit of tripping the mains, and of course Unimat motors are not continuously rated, so cannot be used for more than 8 minutes without rest. The lowest speed is 130rpm, a little too fast for some of the work that I intend to do. I do have a decent spare, but I wanted something better.

I found this one on eBay; 

It looks to be a scooter motor, with a control box on top. The single speed controller on top also doubles as an on/off switch;

Another view of it fitted;

Speed range using one belt (no idler pulley) is a claimed 20 to 2400rpm, although I'm not sure if that's at the motor or spindle.

 So, is it any good. Well, yes and no. It's nicely put together and smooth running, and adjusting the speed without swapping belts is nice (although swapping belts didn't bother me) as is the ability to work without worrying about the motor overheating. But, at low speed under heavy load the motor has a habit of 'pulsing' or stuttering, which is a nuisance when using profile tools. As I wanted a low speed motor for such work I'm unsure just how useful this motor is going to be, time will tell. This is the second motor that I've had from the seller, the first one displayed the same characteristics so I had it swapped (I should point out that the seller was extremely helpful). It may be that I only use it for general work and try to find another solution when using profile tools.

Paul.

PST/Zebrano Gaz-03-30 Soviet City Bus - chassis and wheels.

 The chassis comprised of 12 parts, four of which made up the engine and exhaust. The chassis rails, rear springs and axle and the front axle/radiator fitted together reasonably well, however locating the engine to the gearbox to the chassis proved rather troublesome, the fit being vague at best, not helped by the V shaped arms that run from the clutch to the front axle. In fact I ended up having to lengthen the prop shaft to get it to fit, cutting it in half and inserting a short piece of .040" styrene rod;

Painting started with a wash with warm soapy water and a soft brush, followed by a coat of Hycote red oxide primer applied with my Badger 200NH. For the top coat I used my Badger 150 and Vallejo 862 Black Grey, a nice dull weathered black. At this stage whilst searching for images of the bus online I noticed that the chassis had two rods running from the rear axle to somewhere in front of the propshaft, quite where I couldn't quite make out as the kit differs from the prototype in the chassis layout. However, I decided to add an approximation of these from .020" styrene rod, scraping part of the paint away to get a bond;

Of course this meant getting the airbrush out again to blend in the new parts and touch up the paint where it had been scraped away, but that did give me an excuse to use my Aerograph;

To give me something to hold onto whilst painting the chassis I drilled a small (.8mm) hole in the top of the engine and inserted a cocktail stick to act as a handle.

The wheels were cleaned up, sprayed with Hycote grey primer (through the 200NH again), then sprayed with a mix of Vallejo 866 Green Grey and black. Once dry the hubs had a coat of plain black on the outer side, and black grey on the inner. This was done to give the impression of a bus that is cared for.

Here's the chassis right side up;

I also painted the radiator surround and the front bumper plain black, which contrasts nicely with the dirty chassis. The exhaust had a coat of Humbrol Leather, with it has to be said poor results. Humbrol paint isn't what it used to be I'm afraid.

Body next.

Paul.

Fixing a problem with my airbrush compressor

My airbrush compressor, an unbranded (although the pressure gauge has Sparmax written on it) TC-501C bought in 2008, recently developed a fault. When switched on it kept running after the set pressure had been reached rather than stopping automatically as it should. I checked the joints for leaks with soapy water, but found none so I started a thread on the Britmodeller forum (plastic kit modellers are far more likely to use airbrushes than railway modellers) asking for help. Someone replied suggesting that the pressure switch might have failed and advised me to contact air-craft.net for further advice and spares. This I did, and the helpful Martin agreed that it would be said switch, which had either failed or been blocked by debris. So, I removed the outer casing from the compressor, firstly by unscrewing the feet then undoing four screws in the base and disconnecting the on/off switch. Then the pressure switch, which is protected by a rubber cover and some heatshrink, could be unscrewed with a big-ish adjustable spanner. It can be seen in the photo below, with the rubber cover pulled back;

Note the exposed wires, these are mains leads so the unit needs to be unplugged whilst doing this!

I also removed the L-connector, and both connector and switch were cleaned out with cotton buds and toothpicks.

This is the switch, note the black crud and dirty water inside;

I then reassembled the switch and connector, with the switch sitting at 180 degrees to its original position as I found I got a better air seal that way;

I refitted the on/off switch and tested the unit, and I'm pleased to say that the pressure switch is now working as it should. I have however ordered a replacement from air-craft as I'm sure that I'll need it one day.

And here's the reassembled compressor;

With thanks to little-cars on the Britmodeller forum, and Martin at air-craft.net (usual disclaimer applies).

Paul.
 

PST/Zebrano Gaz-03-30 Soviet City Bus - opening the box

An odd choice of model perhaps, but odd subjects do have a habit of catching my eye. The Gaz-03-30 was based on the Gaz AA truck chassis, which owed its origins to the Ford AA. Production started in 1933 at the Gorky Automobile Plant with the last bus coming off the line in 1950. The body was made from a wooden frame with metal cladding, and due to the poor roads and basic truck suspension needed to be completely replaced every few years. No heating was provided, but it was I suppose better than walking. This model represents a post war bus, after 1945 certain economies were made due to material shortages, hence the simplified angular front fenders (early buses had curved wings). See here for more information, and remember that Google translate is your friend. Information on these is pretty scarce to be honest.

This 1:72 scale kit is a collaboration between PST and Zebrano, two companies based in Belarus. 

Opening the box, the runners and instructions are sealed in a plastic bag;

Four runners are included. The parts look pretty good at first glance, with minimal flash although the detail is a bit 'soft', not as sharp as you would find on, say, a modern Airfix kit.
Here's the chassis and seats;

And the body;

There's no moulded clear parts, just a printed sheet of clear material;

Decals are included, but where do they go? The instructions are very brief and contain no information on positioning them, or even on livery. The exploded diagram does a reasonable job as far as showing where all the parts go though;

This is going to be an interesting build...

(It does strike me that this kit would make a decent freelance railbus in either standard or narrow gauge.)

Miniart make a 1:35 scale kit for this bus, and there are 1:43 scale die-cast models available on eBay. The die-casts all come in plain liveries with no markings.

Paul.

Pinpoint axle bearing reamers.

 Sometimes when your building a wagon kit, no matter how careful you are, the thing just won't run as well as you'd like because the wheels are tight in the axleboxes. This is where bearing reamers come into play;

The ones above are DCC Concepts N/009 type on the left and an Ultrascale OO/EM/P4 etc. on the right. Here's a closer look at the Ultrascale offering;

Note the cutting edge, on one end only. These are as far as I can tell no longer available, but DCC Concepts do stock similar, in both 26mm and 24.25/25.25mm axle lengths.

The two DCC Concepts jobs in close up;

The left had one has clearance for typical N coupling pockets. These have a different style of cutting edge, which is repeated on both ends of the axle.

In use, in this case on my laser cut van (which never has run particularly freely);

They have improved matters, now the van runs quite easily. My thanks to Neil Moss for flagging up the DCC Concepts reamers on the NGRM-Online forum.

These reamers are really only suitable for use in plastic bearings, but should be useful to us kitbuilders as well as improving any tight RTR stock.

Paul.