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Monday, 20 July 2015

Trend T3E Router

A few years ago, I bought a Trend T3E and it was installed as the woodrat router. After making plantation shutters and some other jobs it suddenly stopped working. I had a quick look and couldn't see any obvious fault, so put it away and bought a DeWalt 625 for the woodrat. As it happens it is a far superior router, much smoother, maybe a bit noisier, but with much smoother slides. Anyway, I now may have a need for the Trend, as it is lighter and more suited to hand held work. 

I got it out and put it on the bench to see if I could see why there was no rotation.

 I powered it up and it started first time. This was odd, so I took the top cover off and had a look. 

Quite a bit of sparking from the brushes, so maybe that's the problem. A quick ebay later and I have new brushes. They are a bit bigger than the old ones, but the old ones don't seem too much smaller. With new brushes, there's still a lot of sparking. There must be some other problem. I removed the rotor from the motor and had a look. The commutator seemed to have a couple of copper connectors that had raised above the rest.

This is why I have a lathe. The rotor was easy to fit into the lathe and I skimmed the high points off the rotor. I won't be able to do this very often as material is lost, but it wasn't necessary to remove much copper.

Anyway, afer re-assembly and running the new brushes for a while and the Trend is much happier. Still a bit of sparking going on, but I can probably use it for a while more.

Clock Problems

We have an outside clock and thermometer that hangs on the wall of the house. It's useful to work out how many hours it has taken to mow the lawn, or trim hedges. The thermometer is a mechanical mechanism and seems to work fairly well. The clock, however, is battery powered, which means that I have to get a ladder out every so often and replace the battery. After having done this once, the clock stopped again and I once more got the step ladder out.

After putting a new battery in the clock I was a bit surprised to see that it didn't start up again. After a few more batteries in case they were flat, I decided that th emechanism wasn't suited to outdoor use and had failed. I put the clock back on the wall in anticipation of hunting for a new mechanism.

A few days later I was asked to look at another clock which had also stopped working. I decided to take this mechanism apart and see if there was an obvious fault. The mechanisms are all similar (although the two I looked at were slightly different internally) and look something like this:

The circuit board has the electronics on it, then there's an electromagnet and a gear train that ends with the hands. Anyway, after a look at the internals, I found that the contacts that connect the battery to the circuit board were corroded. As they just touch pads on the PCB, the connection had become bad and the clock wasn't getting power. After a clean up I re-assembled the mechanism (if you do this, then I recommend taking a photo of the internals before you dismantle it. It makes putting the gear train back much easier and quicker). After re-assembly the mechanism worked. So, one clock fixed. I disassembled our outdoor clock and that too had the same contact corrosion. After a clean up that clock also now works as well.

It looks like any moisture on the contacts then cause some form of galvanic corrosion that then causes the connection from the battery to fail. This will probably happen again, so I may solder the connection in future. It's nice to be able to fix these clocks though, and give them a bit more life.

I have an ongoing project which will hopefully end up with a dining room table and set of chairs. Chairs are pretty difficult to make, especially getting the dimensions correct and aesthetically acceptable. Materials are also a big question, cost and durability have a big bearing on those. 
To address the problem of dimensions, I recently drew up some plans for a chair, based on requirements that I'd been given and examples from magazines and places we'd been that had acceptable chairs.

This is a 1:3 scale drawing I came up with of a possibly suitable design. 

 A few hours later and we have a 1:3 scale model of this design:

The woodrat mortice rail was very useful for the mortices on the uprights and other parts. Without that it would have been an impossible task.

I haven't sanded the parts yet, but it does look like a chair. We'll have to see how well it matches the requirements.
I also need to put a seat on the frame, and cover it.

Vacuum Cleaner Failure

We had an old vacuum cleaner that was on car cleaning duty. It was made by Hoiover and worked quite well. I recently bought some new bags for it, as the old ones had been lunch for a mouse or two. Of course the hoover noticed the new bags and decided that it was a good time to make a horrible noise and destroy it's motor bearings.

Rather than throw it away I thought I'd have a go at fixing it. The whole thing was actually designed to be disassembled, everything was held together with screws, apart from the bearings themselves which were pushed onto the motor axle, and a fan cover, which was also (more loosely) push fit.

I got the bearing part numbers and checked on ebay and lo and behold there were some for sale, so I bought a couple at a very reasonable couple of pounds each.

Next step: remove bearings. After pulling quite hard I tried my bearing puller, but found that it was designed for things that were fitted to tractors, not small electric motors. I bought a smaller puller off ebay and managed to easily get one bearing off. The second was more troublesome as it was quite a distance down the axle. I made longer arms for the puller and that was off too.

After pushing the new bearings on, it was time to re-assemble and try full power again. Good news: there's no nasty noise any more, so hopefully it's fixed. We'll see after the first real hoover of something...