Effective density of "fluid lead".

[Atlantic 3279]

I had wondered, on several occasions, about just how effective the "Fluid Lead" (or "liquid lead") fine lead shot sold as convenient loco / model ballast really was, compared to a solid piece of lead. No matter how small the shot spheres may be there must be spaces around / between parts of them when they are packed in to the model.
I looked up the density of solid lead and found a figure of 11.35 g/cc.
I then selected a couple of small cylindrical containers (one being an old 35mm film pot) and carefully measured their dimensions. From those figures I calculated the volumes, and from those figures the mass of solid lead that would fully occupy the internal space.
Using digital scales reading in 5g steps I then weighed the empty containers, the smaller of which did not register at all, while the film pot wavered between 0 and 5g. On filling each one with the fine lead shot the weights came up to 70g and 260g, whereas my calculations for solid lead suggested 121g and 438g.
This suggests to me that the "fluid lead" alone provides only about 58% of the mass that would be provided by a perfect-fit piece of solid lead, although the glue used to fix the lead shot would add some further weight. Obviously, in some situations it is impossible to insert a piece of solid lead that fills the space, and every scrap of space that is not filled by an attempt at a solid ballast weight erodes the advantage of using solid lead rather than small particles.
I conclude that the best approach for maximum effect is to insert solid lead wherever possible, AND to pour in fine lead shot around the solid piece if that cannot be made to totally fill the space.

[jwealleans]

Nice to have empirical proof of something I've been doing for years.

[Hatfield Shed]

Nice to have empirical proof of something I've been doing for years.

Indeed, and the most common obstacles to loading the so very sensible Doncaster parallel boiler with the largest possible solid cylinder of lead are interior protusions from the handrail pillars and other applied detail. Some attention to cutting/grinding these flush can increase the added mass by circa 15% in my experience. (It's possible to load 10 oz of lead in the Bachmann WD 2-8-0 this way, once you have the cast mazak out of the boiler and smokebox; then it pulls like a hero.)

[Seagull]

This suggests to me that the "fluid lead" alone provides only about 58% of the mass that would be provided by a perfect-fit piece of solid lead

In the dim and distant past I remember reading something along the lines of your findings. That regular spheres would have a set proportion of solid object to airspace and the proportion of soild to airspace was quite low.

Most liquid adhesives have a relative density between 0.9 and 1.1 so if you want to be really scientific you could calculate how much the remaining 42% of airspace would add in weight if filled with glue.

Alteratively just buy some lead flashing from your local DIY supplier of choice - it's much cheaper than liquid lead.
Plus it is easily cut to size with a decent pair of scissors - not the ones for the kitchen though

Alan

[Hatfield Shed]

Put 'spherical close packing' in a search engine for the mathematical approach! Theory becomes problematic when the spheres are of varied size. A further factor in our application of getting as much mass in as possible, is that as surface area increases so does the proportion of surface lead oxide to lead reducing the mass of a sphere below that of one of the same dimensions made of lead alone. But that's a quibble, it's the airspaces that do the damage!

As above, sheet lead is far cleaner to work with, and if you can find it in lumps, better yet. (I am just finished working though my late FiL's supply; for some years he cast lead faces for 'knock off hub' mallets for a car marque owner's club, and an unused stash was unearthed as we cleared his garage. )

[Atlantic 3279]

Plenty of offcuts of lead piping in a bag in my shed, easily cut & opened out to flat sheet 3 or 4mm thick...

[Pebbles]

If the lead is roll Swiss Role fashion, then of course we will still have to remember the resultant airgaps. Occasionally density maybe important, but surely the important point is whether sufficient balanced weight can be accommodated within the space available.
On a separate point, I am not a fan of ballast that cannot be removed should it become necessary.

[Atlantic 3279]

I cannot argue with any of those points. Balanced weight can be very important, and a non removable weight could be a real nuisance if fate decides that some aspect of the model structure requires renewed attention. My experiment was aimed purely at finding out how effective the fine lead shot was if the goal was maximum weight.

[nzpaul]

Not so much a question about how to add the weight but, has anyone found (accidentally of scientifically) the tipping point between good for adhesion and too much for the mechanism? Something that concerns me with Bachmann and Hornby models are their flimsy intermediate and final drive gears, increasing tractive effort will inevitably decrease life expectancy. I'm interested to hear of success and failure rates if anyone has good or bad experiences.

Paul

[Hatfield Shed]

My Bach Peppercorn A1s and Hornby Gresley pacific models were weighted to have 600g on the coupled wheels within weeks of their introduction, and I operate very regularly. Best part of 20 years for the oldest A1 in this condition. (The weight is for traction to ensure a restart from rest with the largest train weight of 2.5kg and the entire train on a 1 in 80.)

Not had a single failure within the mechanisms, plastic compatible grease lubrication on gears and axles looks after these for years, (I check every two years), light oil on all rod pins at two month intervals (if rod pin lubrication is overlooked on a loco, jerkiness is observed after about three months since last lubrication). In my opinion, of all the moving drive line components on RTR OO model steam mechanisms, the coupling rod joints are the most vulnerable to wear.