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.