59, Joinery, part two, Sanding.

With all other window parts taken care of, the inside linings were next on the agenda. My ultimate goal is to have all the interior joinery, (reveals, architraves, skirtings etc.), manufactured from Blackwood. In the shorter term, however, unless I can secure a good quantity of reasonable logs for the right price, much of it will initially be of painted MDF.
The insde linings, being a permanent structural part of the window frames, needed to be of blackwood and I sifted through my piles of timber to extricate all of this stuff. Subsequently, after completing the dressing of all of it that I had, I was marvelling at the variety in the colouring of the different pieces when my wife commented. She mentioned that a paricularly large, dark stick, that I had ripped down was originally "bought to make a piano stool" for her. This got the grey matter ticking and the penny then dropped that I had just wasted all my Walnut!
The stock of Blackwood also included some "Black Wattle", a similar species which is rather plentiful in our area. The timber is slightly paler, but the grain is very similar. It is, however, hard to find good straight logs of millable size as the trees are relatively short lived and tend to be more bushy.
As I began to dress of all this stuff, I was reminded of this woods cantankerous nature. It contains a lot of silica which tends to dull blades, any slight pause during machining would burn the surface, grain tearing and furry patches occurred frequently. My previous experiences with it was on lesser scales, odd pieces of furniture and kitchen cabinetry, which, with smaller pieces, was relatively easy to sand smooth. It was fairly obvious that, if I was to continue with it's use, I would need some serious sanding equipment. My initial enquiries had me looking at second hand drum sanders and I made an offer on one advertised in Queensland, subject to reasonable freight costs. The offer was accepted, however, I was unable to find a transport company to deliver it, (to a depot in Melbourne), for any less than about $500.00. The deal fell through, but it turned out to be a blessing in disguise, the more I thought about it, the less I liked the idea of a small drum doing all the work. Any stutter in the drive system could potentially still lead to burning of the stock.
My searching ultimately led me to a machine in Brunswick, made by the now, long defunct, Heidelberg West based firm of L.S. Barker P/L, which, at first, put me off due to it's size. It was a large 3 phase "platen-roll" wide belt sander, having an adjustable flat platen or pad mounted behind the main sanding drum. This would ensure a more consistantly smooth flat surface. The machine was also "open sided", this would enable wide pieces of work to be sanded with multiple passes and the reversing of the work. Although the sanding belt was only 15" wide, with the open side and further clearance on the inside, panels up to about 41", (1040mm), in width could potentially be processed. After much deliberation and due to there being nothing else available, a sale price of $1000.00 was  negotiated and my next challenges were then faced.

Loading the machine onto the trailer was no issue using the sellers forklift, however, unloading the heavy beast at my end proved to be more of an issue. The front end loader, which could easily handle the more than 1 ton weight, has been out of action for some time. At this stage there is no light on the horizon for it's rectification so I assembled a gantry over the load using scaffold components. Once winched clear, the trailer was moved out, more bracing was attatched and the sander was lowered to the ground. With it down, my home made, 3 point linkage, rock carrying forks, attatched to a friends Kubota was barely able to cope with with the load, but was able to move it to the shed floor where a pallet trolley could then be used.
Having the Sander in the workshop then enabled me to commence it's restoration. It was the beginning of another very underestimated project that was to consume most of my spare time for the next 5 months.
For single phase operation all the motors and electrical equipment were removed. Replacement motors were sourced and fitted. The switch panel and electrical cabinet were replaced and the wiring was completely redone from scratch. Each of the 3 separate motors had their own issues of new mounts needing to be fabricated and drive pulleys etc. being altered to gain optimum operational speeds.

The main drive motor presented a bit of a challenge. The original, which ran at half the speed of my replacement, was fitted with a pulley which incorporated a brake drum of the same diameter. My original intention was to incorporate an electrical braking system, however, following much researching and testing, I found that it would not be possible using single phase AC motors. This meant reverting back to the original mechanical brake. To enable this I fashioned a new drum from a twin belt  pulley and turned out the center to accommodate a taper lock bush. A shoulder was also formed on the drum center to allow the much smaller drive pulley to push over it. This was neccessary to be able to fit the two of them on the limited length of the motor shaft.

After reassembling the pedal operated friction brake, I then figured that the last thing I would want to be doing in an emergency situation would be standing at the machine, trying to stop it with my foot!. To alleviate this I fabricated a rather convoluted, hinged lever which was coupled to the brake shoe, a trampoline spring was then mounted to apply the braking pressure and a pneumatic ram, scrounged from amongst my collection of  bits, was fitted to keep the brake released. With a simple solenoid valve controlling the air, any interruption to the power supply would allow the air to exhaust causing the brake to apply. This system has proved to be remarkably effective.

 

After an incredible amount of "trial and error", the pneumatic belt tracking system was redesigned. The original belt "sensor" relied on a jet of air passing across the belt's path to a reference port on the opposite side, higher or lower pressure in this port would control a diaphragm which in turn controlled a two way piston connected to the top roller. The angle of this roller governs the tracking direction of the belt.
As effective as this system appeared to work, I found that, no matter how finely I had it tuned, my 10 CFM compressor was unable to keep up to the demand. Another bout of head scratching was required. The solution came in the form of a photoelectric switch, purchased from Hong Kong, via ebay for less than $20.00. This, via some electronic circuitry, (which took many hours to refine!), was connected to a change over solenoid valve which directly operates the two way piston.
Another potential issue was also considered with this set up; any dust settling on the sensor lenses would cause it to malfunction. Again, the grey matter was worked hard to design a blower system to clear the lenses at regular intervals with puffs of air, a continuous blow would have me back where I started with insufficient air supply. Another solenoid valve, with its controls slightly "bastardised", together with a small reservoir and a couple of flow control valves, all fed via a seperate air drier, finally proved to do the trick. This constitues most of the gear connected to the red tubing in the above photo.
Limit switches were also added as an extra safety precaution, should the belt drift too far.

As if the sander wasn't enough of a diversion on it's own, it also gave me an excuse to make a sheet folder, something I had been in need of for a long time. A lot of googling furnished me with enough photo's, from which to base the design. My own slant was the inclusion of an extra angle iron insert under the clamping bar. This could be removed and substituted with different sized and length pieces to allow a limited amount of box folding to be carried out.
With the folder complete I was able to put it to good use, making various missing parts for the sander. This included panels, doors and dust extraction ducting. 

After having a coat of paint slapped over it, my new toy is ready to rock and roll!. The offset section in the front panel was required to provide some clearance for the vacuum ducting. Other minor modifications included provision of longer adjustable feet, this would allow the pallet trolley to fit underneath and the installation of a dial gauge, with associated linkages to accurately measure the sanding depth. A seperate motor is used to adjust the table height and very fine adjustments are easy to achieve using the handle which needs to be rotated about 6 times for every millimeter of travel.

I am very happy with the performance of the machine and the quality of the sanding. On top of the original purchase price of $1000.00, it has cost me about $450.00 for parts and paint. Was it was worth all that time I spent working on it? I would have to say yes. It should more than pay for itself over the duration of my building.