Well it has been some time since I started this particular journey, but here is the conclusion (so far anyway)
To re-cap, my intention was to even out the weight of the loco taken by each axel and the bogie. Reviewing a number of 4-6-0 full size weight diagrams it seemed that for full size 1/4 of the weight is taken on each D&C axel with 1/4 taken on the bogie.
My B1 is very front heavy which I am reliably informed is a common trait of this model design as it was also in full siz
To add some weight to the rear I decided to make some dummy seat boxes (yes I know not prototypical but would not look out of place) which would be cast in lead then clad with brass. I decided this was easier than trying to make sealed brass 'boxes' filled with molten lead, mainly due to my desire to follow the various shapes inside the cab/running boards to make best use of the space available.
I apologise for not taking phots of each stage, this project has taken some time and I just forgot to record the stages.
As mentioned in my earlier post I first decided to remove the hydrostatic lubrication system in order to free up some space both under the footplate and inside the cab. This was replaced by two mechanical lubricators sited in the LH running board in the same place as Martin Evans located his twin pump lubricator. The reason for using twin lubricators is so I can ensure even lubrication to each cylinder.
This has allowed me to refit the steam brake cylinder and operating valve making revised pipework where necessary.
The injector steam pipes were originally routed through bulkhead unions in the running boards each side within the cab so these had to be re-piped to within the frames so as to clear space for the seat boxes. At the same time, I changed out one of the No.4 injectors to a No.2 with the intention that this can be left on whilst running to maintain the water level in the boiler.
Next up I designed the seat boxes in F360 to make use of as much available space as possible. These were 3D printed in various versions until I was happy with the design.
The final 3D prints were then used as moulds for the lead to be cast in plaster. Various other non-ME projects then got in the way but at least it allowed the plaster to really harden and most of the moisture to evaporate out. I used a casting plaster called Stonecast by Mouldmaster, it is advertised as being harder when set than usual plaster of paris and I can agree that it made a very hard mould.
When the time came to pour the lead, I heated and removed the 3D printed plastic patterns which came out spectacularly easily without any damage to the plaster. The lead was then poured, I had to make two melts for each mould as I under estimated the amount of lead required. Unfortunately, the free version of F360 doesn’t include the analysis function to calculate the mass if a material is allocated to the model.
Once cooled and removed from the plaster the seat boxes were milled to final height (the mouldings were made deliberately too high to allow for this) and smaller cut outs milled which would have made the moulding unnecessarily complicated. I then clad the visible faces with 16g brass sheet held in place with 4BA brass CSK screws self-tapped into the lead.
These two boxes have a total weight of around 6kg, not an insignificant amount.
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A revised footplate was also made from 16g brass and some ¼" brass for the supports
So now to see the effect of the weight boxes on the weight distribution of the loco.
I set up the weighing scales as per previous posts.
I set each axle over the scales and recorded the weight, note this is still as a complete axle and with coupling rods in place.
I moved the loco back and forth a couple of times between each reading which as might be expected changed the recorded values.
I made one change after 6 recordings that was to tighten the springs on the Driving axle by half a turn. This made a negative effect so I returned them as they were after the final recording of data.
These are the updated graphs from before showing the recorded data.
As can be seen the weight distribution is very much more even than before, this was to be expected after the last experiment previously adding weight to the footplate.
Before anyone shouts about the apparent increase and decrease in total loco weight I accept there is some discrepancy in the recorded weights which I suspect is due to a number of reasons:
1. Lack of accuracy of the scales themselves - I have no idea how repeatable the scales would have been before I dismantled them, and what effect my modifications have made or the accuracy/quality of the strain gauges and circuits used.
2. My loco is still quite new and there is some tightness in the axle boxes which will improve with wear as I really don't want to strip the loco for that at the moment.
3. The coupling rods were left attached and as mentioned before this may also have a negative effect on accuracy of results.
Overall i am pretty happy with the outcome and will run the loco as it is for the time being to see if the revised weight distribution shows an improvement in pulling power / traction.
In a couple of weeks i should have an opportunity to compare the axle weights of my B1 with two others in the club so that could be an interesting excercise.
Chris
