David Andrews Princess Royal - 6206 Princess Marie Louise

Then I connected the loco and tender together and it immediately tripped out the controller and so I started a further round of troubleshooting. First I removed the bogie and after coffee I went back into our cloakroom where I have temporarily set up my test board. This room is west facing so gets sunlight mostly in an afternoon but it's below ground level as the path outside the window is cut into the embankment and so doesn't get quite as much natural light unless the sun is really high in the sky and it's late afternoon.

Now one of the suggestions from Thursday nights meeting besides dig out the multimeter was to try hunting for shorts in the dark as sparks are easier to see. As I went in for further testing I forgot to turn the light on and so the room was a little gloomy. This proved to be a benefit, because as soon as I moved the bogie on it's own, I noted a spark which I wouldn't have seen with the light on. I noted that the guard irons were quite close to the rails and may have caused shorts on curves so they were adjusted and then further examination showed that I had fallen foul of the etched washer/hub insulation again. A further check of the trailing tuck revealed the same issue. I had a few spare insulated washers that I had turned when working on the tender but they proved to be too thick even after turning/milling down the axle bushes.

I was initially going to make some up by using a hole punch to cut holes in some styrene sheet and then snip of /file them into circles. By good fortune a video that I had seen some time ago that was lurking in my memory surfaced on my Youtube feed. After rewatching it I decided to have a go at pressure turning a number of washers all at once.

Now unless you want really big washers the process is a little wasteful because you need enough stock to hold onto to drill the centre hole. I chose to cut some 0.5mm styrene sheet into 20mm x 20mm squares aiming for a finished size of 10mm diameter. You also need some scrap to hold the parts and one of them becomes almost sacrificial.

The first step is to grip the styrene squares between the two pieces of scrap material.


Drilling blanks
I used a 1" G clamp and a small engineers clamp to hold them all together to drill a 5mm hole through all the parts. This was to allow clearance on the 3/16 (4.7mm) axles. At this point you transfer the whole set up to the lathe before releasing the clamps.


Setting up for pressure turning

Pressure Turning Parts
I created the above set up which consists of a 22mm piece of Delrin in the collet (I had to turn a stub down to fit in a 16mm collet which is the largest ER25 collet that I have). This had a 5mm hole drill partially through it. At the tailstock end is another piece of 22mm Delrin which has had a 60 degree cone turned in the back so that it fits on a live centre then a short section turned down to 10mm to allow the tool to clear the workpiece(s) again it has a 5mm hole through it. Then a length of 3/6 rod was passed into the hole in the mandrel in the collet chuck and the parts fed onto it, before removing the clamps. Lastly the live centre is wound tightly against the parts which squash and grip all the parts for turning and locked.

The next step was to turn down the sacrificial scrap support until all the parts start to be turned. My sacrificial scrap was plastic which has a layer of aluminium either side of it and I found that the most depth of cut I could manage was 0.25mm per pass otherwise the parts started to slip. I started turning with a carbide tipped bit until it would no longer fit, then I changed to high speed steel grooving tool that I had ground for another job some time ago.


Washers well on their way.

Finished Washers
One piece of advice given in the video was to make sure that you were using a sharp tool for the final pass to help prevent the tool from rolling the edges of one part over onto the next.


Finished Washers
These are the finished parts and they are all really crisp, aside from the one that was nearest the left hand piece of scrap which had a small burr around the edge (visible at the corner of the ruler). This burr was easily scraped off with a scalpel blade.

 

It's been getting on for six weeks since my last update on HRH. I haven't been idle and the process of eliminating shorts has been a journey of education, frustration and determination to not let it beat me.

Starting with a belt and braces approach I remade the drawbar in Delrin.



Next, having already added insulated washers to the wheels which are insulated at the hub I turned my attention to the driver which are rim insulated. I had previously made inner balance weights from Nickel sheet and although I had stuck them to the wheels with epoxy I was concerned that they be be helping to bridge the insulation gap should they touch the frames. My answer was to remake the balance weights for the insulated side from styrene.



Then I noted that the cross piece pf the rear inner frames was touching the tyres of the rear truck wheels. You can see the plate with the half etched rectangles in the image below.

A look at the instructions mentions the possible need to remove the half etched sections in case of shorts so the plate was removed and the rectangles removed.


Sadly, this didn't cure the problem so in the end I took of the outer sections leaving just the brace in the middle.


As it turned out that solved one problem but left another which will be the subject of another post

 

Having solved the issue of the wheels touching the upper frame I then discovered that the wheels were touching the inside of the frames when going around a 6ft curve.



So I added some styrene insulation either side of the inner frames.



This cured the short problem but running trials revealed that although it would now go around 6ft curve without shorting it didn't do so reliably without the trailing truck derailing.

In an attempt to cure this I tried introducing some weight on to the trailing truck. I cut a couple of rectangles of lead and using a V block and a couple of different sized rods I created some weights that fit on top of the ruck over the axle.





I was getting low on lead but just this week we have had a couple of chimneys repointed and re-leaded as well as four wet verges I asked the roofer for the lead that they removed so I now have sufficient to see my days out I think.

 

Hi Jim,
I have already done that prior to arriving at this point. There is more to come...

 

Hi Andy,

The styrene is only 0.25mm thick so quite thin.

 

All issues of whether the styrene might wear over time aside, even with added weight on the trailing truck, the chassis still wouldn't go around a 6ft curve reliably so more drastic measures were needed.

Using a piercing saw I cut out part of the inner frames.



Then I soldered a plate across the ends of the frames at the front by good fortune there were two tabs at the rear with could be soldered to.





I then reduced the width of the inner plate and soldered the frame pieces back together with some end plates to take up the gap left by the saw kerf.





A quick dry fit of the rear truck leaves plenty of space either side of the inner swing so there should be no shorting but I may need to remove some of the spring casting to allow more swing to help it get around the curve - it's a long chassis.

 

Well, I got there at last. Her Royal Highness will now go around 6ft curves without derailing or shorting.

I did have to introduce some springing to restrict the movement of the bogie.



There are two spring wires at the rear which fit between the inner and outer bogie frames. They restrict the sideways movement of the rear of the bogie. The bogie pivot point has side control springs which allow more movement at the front of the bogie. This sort of worked but the front of the bogie was so light that it had a tendency to lift of the track so I added a second element of springing which holds down the front of the bogie and all runs nicely. This spring has a loop which is held in place by the pivot screw then bends over the front of the plate that you can see in the image below before curving onto the front of the bogie frame. Although it looks huge in the enlarged image it's only 0.5mm spring wire.

 

A few photos of the state of play before I strip her down and pack her up for painting.

 

Hi Jim,

Yes the tender axlebox will go on after paint de to the need to line around the lightening holes in the tender frames it just makes it easier for the painter.

I have checked and thankfully it's a trick of the camera the step are vertical on both sides (Phew!)

 

No problem Jim, I would much rather someone said something while there was still a chance to rectify it, as you say it would be a nightmare after it's painted.