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Pete Howlett
11-11-2011, 10:39 PM
As you know I am a facist when it comes to machine bending, using it almost exclusively for my sopranos; so when it comes to rethinking my processes as I did yesterday I thought I would share a moment of revelation and catharsis.

The reason I don't really get on with machine bending is access to the proper temperature controllers etc. I can't yet afford that great setup offered at LMII so ultimately the process in my workshop is more often hit and miss with a lot of over heating going on. I've recently adopted parts of Chuck's 4 minute bend at max power technique so know how my 5" Hana Lima blanket works for bending the soprano sides - am very comfortable with this. However I have a 3" British supplied blanket that is fearsom and I invariable cant seem to get the process under my control.

Yesterday I had a great thought - I hand bent the sides (this only take 5 - 10 minutes) and then put them into my machine bender to set them for 4 minutes. Now you might ask why? Invariable with hand bending you get slight variations in the curves which I rather like - perfect symmetry often makes the instrument look to me very 'hard' and clinical. However, if you have a bit of wild figure this can create 'cockling' (a northern English term) or facetted bends asnd often the waste is quite a chellenge with a curl positioning itself, as it nearly always does, right in the valley of the bend. The setting proceedure irons these out and makes fitting the 2.2mm alder solid linings a much easier process.

Now I am 100% sure I am not the author of this technique. However I now have much peace of mind and a process I am very comfortable with. Off to bend some Tasmanian Blackwood...

Michael Smith
11-12-2011, 12:20 AM
Can you use a router speed control or a dimmered outlet or a dimmer built into an extension cord to cool those blankets 10 to 15 percent? Your blankets may produce more heat even if the ratings are the same for the 220 volt versions than the 110 versions? You may be getting a little more voltage if you are stepping down from 220 to 110 and running a 110 blanket than Chuck. The blanket I bought had a temperature control built right on the blanket, a nice feature but I tend to run it full blast as it is much cooler than my previous blanket. It stopped my burning problems has given a much greater room for error.

Timbuck
11-12-2011, 01:49 AM
Get one of these Pete...It'll do the job nice http://www.ebay.co.uk/itm/POWER-REGULATOR-ELECTRIC-MOTOR-SPEED-CONTROLLER-/110768895288?pt=UK_BOI_Industrial_Automation_Contr ol_ET&hash=item19ca573538 ....This one will handle 600W but they make bigger ones if needed.... Make a nice little box for it ...You connect the mains where it says 110v upto 230v and then connect the blanket where it says load then adjust the knob to desired temp then away you go....I'll lend you the cash if your skint:)
And here is one my son made up as a router speed controll.
http://i219.photobucket.com/albums/cc143/shiregreenbod/speedcontroll.jpg
I usually bend my sides twice in the bender... first I bend them and put them in my stick machine to hold shape in storage..and just before I use them on a uke, I give them another quick session in the bender just to iron out any areas that are trying to staighten out again..But I still have to use the hot pipe on the end bits where they meet the blocks..Co's I didnt allow for that when I made the former :o

Pete Howlett
11-12-2011, 03:59 AM
I already have voltagr controllers. The LMII system links these toa thermo couple which is what you need if you are to do this right since the margin bewteen scorching some woods liek kao is very narrow.

Timbuck
11-12-2011, 04:19 AM
I already have voltagr controllers. The LMII system links these toa thermo couple which is what you need if you are to do this right since the margin bewteen scorching some woods liek kao is very narrow.
I havn't scorched any wood since I bought the meat thermometor, and fitted it inside one of the bender heat retaining rods.

Also I'm considering getting one of these sometime soon as an uprade http://www.ebay.co.uk/itm/Digital-AC-DC-Multimeter-Thermocouple-Sealey-MM20-/400210883043?pt=UK_BOI_Electrical_Test_Measurement _Equipment_ET&hash=item5d2e6d71e3 or http://www.ebay.co.uk/itm/TM-902C-K-Type-Digital-Thermometer-Thermocouple-Probe-/280755448465?pt=UK_BOI_Electrical_Test_Measurement _Equipment_ET&hash=item415e542a91

Rob-C
11-12-2011, 05:12 AM
How many watts is your heat blanket?
One of these will drive a 3 amp load and has a range of 0-400 deg C
http://www.ebay.co.uk/itm/Temperature-Controller-K-Type-Digital-Setting-220-/250401858760?pt=LH_DefaultDomain_0&hash=item3a4d1d24c8

Moore Bettah Ukuleles
11-12-2011, 06:34 AM
At least two ways to prevent scorching; one is to moderate your heat, another is to protect your wood. Personally, I like lots of heat when I bend, and I use two blankets, one on each side of the wood. Of course the wood is well protected by metal, canvas, whatever. Full power, four minutes, done.

Timbuck
11-12-2011, 07:12 AM
How many watts is your heat blanket?
One of these will drive a 3 amp load and has a range of 0-400 deg C
http://www.ebay.co.uk/itm/Temperature-Controller-K-Type-Digital-Setting-220-/250401858760?pt=LH_DefaultDomain_0&hash=item3a4d1d24c8
Thats just the job Rob..it's 5Amp output thats 1150 Watts it'll handle two 500W halogens at once...and k type thermocuples are cheap on e-bay....Thanks for that.

Pete Howlett
11-12-2011, 08:47 AM
I wouldn't even know how to wire it all up... Chuck's method really works :)

Rob-C
11-12-2011, 11:46 AM
Thats just the job Rob..it's 5Amp output thats 1150 Watts it'll handle two 500W halogens at once...and k type thermocuples are cheap on e-bay....Thanks for that.

I found the datasheet - it's 5A at 24vDC; 3A at 240vAC. You could always switch the halogens via a relay..