November 2012

Up until now all the bases have been made from purchased precut billets of aluminium which are then machined by the subcontractor or since last month myself. Having got new quotes for finished bases to the new drawings; I decided that I should undertake the machining myself on the Boxford AUD ..

Having purchased 1500mm of 75mm diameter Aluminium bar stock from a scrap metal merchant (via a very nice chap called Keith !) a couple of weeks back (a real deal providing I could either cut it down myself or borrow a sawing unit to do it at little cost) I set about setting up my  Wadkin C6 bandsaw to try a few test cuts….

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How I wished mine looked like this – alas I rebuilt mine from a scrapped unit out of a skip at a factory closure, no table, blade guides or fence. But for free what could I say ?

It now sports a 600 x 900mm x 30mm thick solid steel table, a set of decent guides and shares a fence with my old startrite table saw. It also runs a single phase 2kw motor and has a very dented set of guards thanks to the skip entry and exit ! A rather effective blade guard fashioned from Ali’ chequer plate completes the unit.

What I needed to do was to guide a 1500mm by c25kg length of bar stock under the saw in such a way that it would cut true, not spin the bar, twist the cut or result in my losing finger tips etc. I decided to build up a sled jig which would allow me to both clamp the bar to a fence, run it along the guide dado in the bandsaw table and also an additional guide down the saw table free side.

First cut was 550 mm off the end of the bar – to make things a little less long for handling.  The next question was that of saw blade selection. A couple of years back I came across Ian John  – Store Owner at Tuff Saws  http://tuffsaws.co.uk/ 

Now Ian is one of those guys that you know he knows what he is talking about and can trust. I have purchased quite a few bandsaw blades from Ian in the past and can only say that every last one has been perfect for the job in hand be it cutting up big heavy Oak wet logs or air dried oak cabinet joints. So I dropped Ian an email Sunday lunch time, I got a reply a couple of hours later … get the idea 🙂

I ordered a 4 tpi super hard carbon blade on his recommendation. Meanwhile I searched the workshop for a pack of old blades I dug out of the skip and found an unused 8tpi carbon steel blade which whilst 3/4inch wide looked like it would do the job to get things started while I awaited Tuff Saws best.

I vacuumed out all the saw dust form the saw behind the doors, striped and cleaned the blade guides and lubed with the new oil can for the Boxford 🙂 All set up; guides adjusted and blade tensioned and running true to the sled face,  I cut the bar stock – nice and steady with light thumb pressure. Noise asside which was not great but different to the wood cutting noise, all went quite well…

The bar in two I checked the cut ends with an engineers square – less than 0.3mm deviation from true – perfect for minimum facing up on the lathe, less scrap and time at the lathe. I adjusted the length stop and then set the shorter length of bar stock up for the first disk cut. 30 disks later and all well except for my getting a numb thumb from the vibration.  I varied cutting pressure and didn’t get much difference in speed but lots of heat and more deviation so kept things slow and steady – I will finish the short length cuts in the morning and then re-clean the saw down to ensure the aluminium particles go into the scrap bin, then its on with the turning.

Meanwhile, sales continue to hold up with the HT modifications proving to have opened up the market. 

Investment has now been fully recovered and at last materials are being purchased from revenue streams rather than continual cash injections to meet the growing demand from stock. I expect that there will be a further demand blip ahead of the festive season followed by a slowing down for the end of the cold season … but who knows for sure ?

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Mid September we took the plunge to invest in some equipment to help speed up the prototype production of fan hubs and bases not only for the HT version but also the two new products being developed in the background … top secret couldn’t possibly tell you more at this time without then killing you !

Having searched for what would provide the best degree of flexibility within the available floor space (5ft x 3ft of workshop floor) I plumbed for a centre lathe. Then it was down to either  a new chinese unit from Chester Machine Tools or something from the used market.  The key feature for my mind was to have a powered cross feed to enable me to make good clean facing cuts on the bases – this sealed the fate of the Chester units as the footprints were too large as was the price tag.  I got a small degree of satisfaction when I discovered an old English make and on line forum for owners / users http://groups.yahoo.com/group/BoxfordLathe-UserGroup/

My Boxford AUD, purchased via ebay from a School in Sandbach took 6 lads to lift it into the workshop after my virtually stripping all down to lesson the load.  It now sports a bright red coat of paint, single to three phase inverter and I have stripped down and rebuilt the cross slide, saddle assembly to ensure smooth cross cutting.  Having not used a metal lathe since I was 15yrs old and doing Metalwork O Level at a Grammer School – it was surprising how much I could recall (very little !) The wood turning of the last 5 years has helped to a degree as far as tool grinding etc. 

A new Chinese 125mm dia’ chuck was purchased, as the 100mm chuck wouldn’t open to take the 75 m base blanks for machining.  The frustrating thing was that the new chuck only just takes them with the jaws sticking out 18mm !  So I looked and found a used 5″ Bernard & Pratt 3 jaw scroll chuck – lovely bit of kit unfortunately on the wrong backplate for my lathe – so then we had to make a new backplate from a part machined blank.  This was proper engineering,  working to 0.0005″ for a fit !  I managed after a few hours to get the location plate boss machined into the chuck backing plate.  Then all that was required was to drill and tap through the chuck body M8 – a tight fit through the old imperial holes but when complete it runs true as a nut on the Boxford – where-as the 4 jaw scroll chuck from RDG which cost twice the price of the used B&S runs out of true … quite a bit – something I will try to resolve when time permits

To finish things off, a spare set of inside/outside jaws and some soft jaws also from ebay . Oh , then of course there was the cutting tooling, quick change tool posts, spanners, allen keys etc etc and Oil Can…. all that was left was to learn how to turn …. and determine what the final design of the HT Fan-Ce base would be. Now I had ample time to make samples for testing.

Having now turned a lot of  bases from sawn billets and machined all of the older bases into the new design it all seams to be going fine (kiss of death). I should add, we purchased a milling bracket, collet set and tooling to ‘get the job done right’ !

Quite a chunk of additional investment over and above the outlay for the lathe & power conversion. But its 75% paid back already so no bad thing !

Sales in October were strong – well over the total sold from the start of the year through to Sept’. November is looking good, as the HT base and some dircet mails to previously found clients looking for a HT version have all resulted in sales. The additional costs, + VAT and recovery of postage costs not previously allowed for have resulted in a substantial price hike – which with the increase in sales numbers has taken my by surprise – economics A level I’m sure sugguested higher prices push demand down – unless we have now entered the real of  ‘good of ostentation’ !

It has not been all good news, we have had a few returns – notable of which was one set of charred remains which were returned apparently not the result of the fan being exposed to temperatures over 200 degrees C.  The fan blades were gone, the copper work looked like that of a twenty year old immersion heater – the soldered tips had migrated – the TEG cooked even the Teflon coated wires had melted. Quite a sad mess – ALL the returns are as a result of high temperature exposure and the resultant TEG failure. With the exception of the Charred remains, all units have been repaired and returned at cost – clients picking up the bill for the new TEG and my changing the base to the new HT version as a preventative measure.

As I type, another order for a Fan-Ce Black HT has been paid for – leaving me out of stock when they arrive already !

Nice position to be in though.

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Nov 6th 2012

Time has wizzed by since the last post / update.

Having made various versions of base profiles and designs to overcome the excessive heat exposure on some stove tops and having thrown the towel in on a few occasions .. or rather toys out the pram !
After quite a few months we found a solution which was both effective and cost efficient.

Armed with pages of data (well a dvd anyway) logged from thermocouples recording both hot plate temperature and base top temperatures (TEG exposure Temp), Fan RPM and motor voltage and current , Tony Gospel arrived at our premises to repeat the tests and put the project to bed with a successful result.

First problem was moving the 600 mm x 600 mm Steel Hot Plate into  safe position within the workshop – quite a heavy lump of equipment. Once installed on heat proof materials with plenty of head room and free air around the unit was brought upto temperature.  Now anyone that knows the workshop knows its not heated – so the 6 degree C air temperature was not helping with the heating up !  After a couple of hours the plate had just about managed 395 degrees – however initial tests of the same fan assembly were concerning as they HT base did not appear to be preventing the TEG exposure exceeding 210 degrees.

We were troubled to say the least ? why with all the same equipment and test subjects were the results repeated in the Lab in Nottingham not repeating here ?  Trying to salvage the day, we set up the Hot Plate to 350 degrees C which it held quite happily, we tested multiple base samples / fan combinations to ensure that normal manufacturing tolerances were proven. The net result, well not the 400 degree C exposure we wanted but at 350 degrees C the TEG exposure was 190 degrees C.

In our view this would cover the vast majority of Stove Top Plate Temperatures. After the heating kit had cooled sufficiently to handle it was loaded up and Tony left me to convert the stock of Fan-C & Fan-Ce over to the new HT  base design….. once i had made the first batch.

As of November 1st, all products shipped have been HT versions. Additional improvements include High Temperature adhesive for fan blade to hub & drive plus grub screw amongst others.

Meanwhile, we have managed to secure a stock of the popular Black Fan-C bodies and these have sold as fast as i make them up. The Fan-Ce in black on the other hand is a rare beast and attracts a premium when the units become available – the additional costs in building these special order products will soon preclude sales….. or maybe not ? The current units of which I have two pre-ordered at just shy of £200 and a third to hold as stock.

It is a shame I have as yet drawn a blank when it comes to finding a nickel chrome plating service prepared to undertake the operation – a new search must now be high on the list of things to do, in order to supply this niche market with a select product.

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This image taken by Tony Gospel from the Environmental Technology Centre University of Nottingham shows a Fan-C airflow test underway.  The results demonstrated upto 200 cu mtr/hr at full speed, not bad for a small stove top fan  under 6″ tall. If I recall that Hot Plate burnt out after testing and a new larger unit was purchased for the test program – thankfully I never had to pay the bill.

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