The Saunders casting machine, part 4: They call me MISTER Saunders

Fighting 15s’ new casting set-up, new machine on the right. And yes I still have to trim a few inches off the bench top

Well, here’s a surprise: the article on casting tips for a Saunders spin-casting machine is put back for a while thanks to the arrival of a new baby in my life: a virtually mint Saunders Mark 5. I am now the proud owner of three of the beasts: two working, and one for spares, repairs and ultimately refurbishment.

The idea was that my spares machine would be machine number two, but refurbishment is currently awaiting welding work on the casing and lid, and it really needs a new funnel.

The new machine has arrived thanks to a chance conversation with Paul Thompson of Early War Miniatures at the Bovington wargames show. It was his spare, but he has now acquired another compressor machine. According to Paul the Saunders had been languishing in a basement for 10 years before he acquired it, having originally been bought to cast model railway parts. But the then owner couldn’t get it to cast and abandoned the project.

I spent the weekend clearing out the workshop to make space for the new beast, and a morning cleaning the machine and freeing-up seized parts. I have never seen such a pristine example of a Saunders, however, it is showing all the signs of long storage. Most of the internal arms and threads still have a golden tinge of what looks like zinc plating, and slight oxidation of this means that the threads on the weight arms needed re-stripping using the 5/8 BSF die nut I’d bought to refurbish machine number two (see part 3). I am fortunate in that I have a sturdy bench vice to hold parts securely while I turn nuts with a wrench after applying universal engineering solution no 1 for parts that don’t move but should – WD40.

The machine had some slight metal build up on screw threads, all of which was possible to flick off with the help of a screwdriver. I also scraped the inside of the casing to retrieve a few hundred grammes of unknown metal.

It should be obvious from the picture above that although both machines are Mark V Saunders separated by only a couple of hundred by serial number, they are both different. The most noticeable differences are the height of the motor mounting, the nature of the belt guard – which accounts for the different height of the motor, and the start-stop switch and lid-lift break switch.

The belt guard on the new machine is a fully enclosed type – the old machine has a guard only at the front. After fitting it, I have to say it’s the worst designed bit of safety kit out, as it catches the parts it is supposed to enclose. In the end I left the back part of the guard off, and ultimately I may replace the front part with the half-guard from the spares and repairs machine. The enclosed guard necessitates a lower mounting position for the motor assembly.

The start-stop switch is a soft, NVR type; the older machine has a less-safe on-off type switch which in my experience causes RSI through repeated usage because it takes a good prod with a finger to turn it on. The lid has a complex arrangement that sounds as if it operates a relay to turn off the machine when the lid is lifted; it takes some time for the turntable to come to a halt, so safe operation is best accomplished using the start-stop switch. As this is soft-touch it shouldn’t cause RSI.

My original machine has a simple push-rod system that operates a switch under the machine when the lid is lifted or closed, and I therefore tend to use the lid to start and stop the turntable – saving me a fortune in chiropractor’s bills. The spares machine has no lid switch at all.

Recessed platter for 11 inch moulds: the line drawn in felt pen helps approximately centre 9 inch moulds that have no central location stud

Inside, the bottom platter of the turntable is different: it is recessed by several millimetres to accommodate 11-inch moulds. This also lowers the typical height of the top platter in the machine, in theory allowing slightly thicker moulds to be accommodated. One of the weaknesses of the design of the Saunders is that it cannot cope with really thick moulds because the adjusting screws on the top of the weight arms can only be adjusted upwards so far (a modern compressor/ram machine is far more flexible when it comes to mould thickness). The recess on the platter unfortunately catches the first knuckle of the fingers when using a nine-inch moulds, making protective gloves essential.

Update: The recess has the unfortunate side-effect of increasing the distance between the end of the funnel in the lid and the mould. I found this led to more metal spray across the top plate, and so I put in a 5mm packing sheet of rubber (I vulcanise a few layers from an organic rubber mould to make these) when casting to make it behave like my other machine.

Owning two machines that show no signs of being able to adjust the motor speed – the knob to adjust the motor distance from the turntable belt wheel and therefore alter tension on the variable speed pulley on the motor spindle is just too stiff – it was a surprise that this aspect of the new machine works as intended, with the adjustment knob turning freely and allowing a speed selection of, in theory, 500 to 900rpm (see part 1). However, the machine doesn’t run sweetly until set to 700rpm or faster; increased speed is certainly noticeable when cranked up to 900rpm, which should make this machine better for dealing with problem castings.

A word of caution. Because the actual speed depends on the tension of the belt on the variable speed pulley, the speed on the gauge may not be accurate. If links have been taken out of the belt since its factory set-up then there will be more tension on the variable speed pulley and it will run slower than indicated. Trial casting seems to indicate that turning the new machine at the indicated 800rpm seems to produce much the same result for casting success as my other machine set to 600rpm – but that has a fan-belt rather than a multi-link V-belt between motor and turntable. I haven’t changed that to a V-belt because the machine is running fine and I work on the principle that if it works, don’t touch it.

Update: Inspecting underneath the machine, I eventually twigged that the main V-belt pulley on the new machine and spares machine is 6 inches in diameter; the one on my original machine is 8 inches. I don’t know if was subsituted by a previous owner, but it explains why the maximum speed of the original is capped at about 640rpm, whereas the others will get up to 850-900rpm. There again, different Saunders machines may have been built to different specifications. I’ve ordered a new 6in 5/8in bore V-belt pulley for the old machine – ideally I’d like both machines to behave in exactly the same way.

The new machine has only a set of heavy weights, which were set slightly more than half-way down the weight arms. It’s no surprise that the original owner couldn’t get anything to cast. I tried it, and even my AB horse moulds, which require more pressure than others to seal, would not cast successfully at any motor speed. I then decided to adjust the arm weights, which is when I discovered they were locked pretty solidly onto the shaft, which meant I reached for the WD40 and took everything apart. However, it was interesting to try a machine that looked factory fresh on its set-up.

With the weights wound up to the top of the arm, mark a line on them with a felt pen so that the number of turns down the arm can easily be counted. This allows mould pressure to be adjusted with a fine degree of control

Once I’d freed up the weights and the adjustment screws on the top of the arms, I set the weights to my usual number of turns down the shaft (10  complete turns from the top for horses). To do this, wind the top nut on each arm to the top of the arm (i.e. nearest the platter), then wind the weight up to touch the nut. Mark the weight with a felt pen – I draw a line outwards from the centre – and use this line to count the number of turns back down the shaft. Then tighten the top and bottom nuts lightly with a spanner to lock the weight in place on the shaft.

With a mould and the top platter in place, hold each arm in turn so that the top adjustment screw just touches the platter (there’s a circular steel disc where each arm falls). Turn the screw so that it falls roughly in the centre of this disc (see part 2, for how to accomplish this easily using record turntable spirit levels).

Update: The adjustment screws on this machine are tight and don’t move freely, despite cleaning, and I have ordered a 5/16in BSF die nut to re-cut the threads.

As explained in part two, I attach spirit levels with epoxy putty or adhesive to the top of each arm after turning the turntable pillar up and the adjustment screw down so that the screw lands centrally on the pillar – all three arms are held by rubber bands to keep them in this postion until the glue has set. With the pillars wound back down and a mould and the top platter in place, the adjustment screw is turned until the spirit level bubble is central. This means when casting that pressure is always applied at the same point for all three arms, regardless of variations in mould thickness, thereby ensuring more even distribution of pressure across the mould.

I set the speed to what was supposed to be 700rpm, but eventually moved up to 800rpm to replicate the results from the older machine.

I will at some point use a non-contact laser photo tachometer to accurately measure the speeds of all the machines. When I last borrowed one to measure the speed of my original Saunders, it was running at 620rpm or so regardless of what the machine’s speed gauge said.

Update: I fitted reflective strips for the laser photo tachometer to the belt wheels on the underside of both machines so I could read the turntable’s revolutions per minute without opening the lid. The new machine, set to 750 on the gauge, runs at 620 rpm; the original machine, set to 600 on the gauge also runs at 620 rpm. So both machines are now set to run at the same speed. The new machine when set at 800 on the gauge was actually running at nearer 700 rpm. Just so you don’t go around believing anything a machine tells you.

Encouraged by the fact that the motor speed was clearly adjustable, I applied engineering solution no 1 to the screw elements of the motor rack on my original machine, and within a few minutes the WD40 had penetrated and I was able to adjust the motor position. Again, there was no discernible change in speed, but the original machine uses a fan belt which I suspect when only just taut is too long for the distance between turntable belt wheel and the variable drive pulley to make a difference. When it eventually fails, I’ll replace it with a proper multi-link V-belt.

WD40, however, has failed to help on the spares machine, so I will be disassembling the motor mount and adjustable rack when I have time. I suspect the screw threads must corrode slightly and they just need cleaning and freeing up.

Anyway, with two machines now set up to cast properly, I should be more efficient in what I turn out. I’ll be able to have one machine running while I empty the other. I work by optimising the machine for a mould and then running that one mould repeatedly, rather than working through a stack of five or more moulds, to avoid having to adjust the machine each time between moulds. This is because I am an insane perfectionist who would rather work slower to achieve the optimum result for a mould. 🙂 I should add that even this trait does not guarantee an end to mould lines; it just minimises them. If I ran compressor machines that automatically adjust for different mould thicknesses, where pressure can be changed at the touch of a button, and motor speed can be changed at the turn of a dial, then I would work through a stack of moulds like any normal person.

I’ve managed to operate Fighting 15s for 10 years using just one casting machine with no guarantee of finding spare parts or being able to get it repaired if key parts go wrong. The nightmares associated with its possible failure – the one week I spent without it was problematic to say the least – mean that although it may seem excessive to have two running machines and a spare, I am at last in the position where I can survive the failure of one machine and quickly repair it or slot in the spare until the failed machine can be repaired.

Next: Casting tips or the Saunders instruction manual (if it arrives!)


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