side bending

[gratay]

Is anyone using heating blankets?
I am torn between making a fox style bender with light bulbs or using a heating blanket..
I would rather use a blanket but can only get the temp control for the 110v models......and this is starting to add up $$ when you have to add a step down transformer to the equation
If anyone is using blankets in australia ....how are you controlling the temp

I am inclined to go without temp control on a 240v model and either keep turning it on and off or use a spray bottle to cool it but these things heat to 500 degrees F in 2 minutes

I have asked many questions in american forums but just interested in how people in australia are using them or whether most people opt for the light bulbs?

the 240v blanket for LMI is about $124 US which would be viable if you can use them without temp control...
I can always go the pipe route but want to research blanket possibilities first

[kiwigeo]

Saw your posts in OLF Grant. If cost is a factor then go for light bulbs. Make sure you run your bender off a timer so you dont set fire to your expensive rosewood sides when you walk away and forget about them.

While youre humming and harring about which route to take with the bender you could put the time to good use by whipping up some sides on a good old fashioned bending iron...its not as hard as it looks and its fun.

[Flowboy]

Hi Gratay,

I happen to have a 240-110V step down transformer, which I could be persuaded to loan to you. Believe me its plenty powerful enough to run an electric blanket.

Regards

Rob

[gratay]

cheers thanks for the offer rob.
i'm not sure which method i will use as yet ... but whichever way i go i want to start building the jig now....luckily whether it be bulbs or blanket will be pretty much similar jig.....

[Paul B]

You can buy 240V silicone heating blankets here:

WATLOW AUSTRALIA PTY LTD 4/57 SHARPS ROAD
TULLAMARINE VIC 3043
AUS
Phone: +61 3 9335 6449


http://www.watlow.com/products/heaters/ht_flex.cfm

[gratay]

thanks paul.......i did speak to them a few months ago and they said that the blankets that size 37" x 6" were only 110v plus they were about $260 as opposed to the LMI ones which are around $125 US
I must give them another call just to check it out again

are you using one?

[kiwigeo]

These guys might be able to help you. They have temp controllers as well as silicone rubber blankets.

http://www.hotco.com.au/Flexible_Elements_Tapes.html#Flex_SSR_Blanket

Cheers Martin

[Paul B]

No I'm sticking with my bulbs, they do the job for me and are easy to replace locally.

Maybe watlow only have 240V blankets in sizes other than the one you're after.

I know someone on the OLF sells heating blankets in 110V and 240V 'cause they said so in a post a few weeks ago. Might have been John Hall of Blues Creek Guitars.

[bobz]

Hello gratay,

I`ve made a Fox bender although I have`nt used it yet, but I will be using it with a heating belt. I just recently purchased a 220v timer from LMI which they did`nt have in stock at the time I bought the heat belt. I have also bought a meat thermometer with a 3/16" stem which I`ll use to monitor the temparature. The steel slats and the damp side will draw the heat away from the blanket in use, and I should think you can have the blanket on for about ten minutes with no ill effect. I don`t really know yet hence the thermommeter. You can see in the photo that I have still built in light bulb heating into my Fox jig just in case I destroy the heat belt.

[kiwigeo]

Nice work on that bender Bob. Did you make or buy the hardware?

[gratay]

thanks for the hotco link martin.....i have contacted them and their standard size is 265mm x 320mm w/temp control 240v which was ...wait for it...$399 .so i'm waiting for a quote on 940mm x 150mm but not holding my breathe

and bobz nice bender ...so sounds like your giving it a go without temp control...someone on the OLF said their temp control was a spray bottle of water which may work depending on what order of layers you have ....?

[contrebasse]

You can see in the photo that I have still built in light bulb heating into my Fox jig just in case I destroy the heat belt.

But, you'll need to encase the thing in another ply box if you need to use the lightbulbs or else all the heat will escape out the sides, no?

Anyway in answer to gratay's question, I used only a heat blanket from watlow for my bass ribs; they can send you a huge catalogue for free and you can order in 115v and 240v with only a few weeks delay. they make them up overseas and ship them in i think. I didn't use controller and didn't need one - as unlike using a pipe bender the ribs get soft so fast you are bending the whole thing within a minute or two. No chance I'd walk away and forget them!

Now - I can imagine using lighbulbs, things would take a while longer to get interesting ...

[Malibu]

Gday Gratay,
I had the sales rep call in from Hotco the other day and I thought.. hmm.. while you're here!!
He said the standard belt off the shelf is 25mm wide and around 900 long with a price tag of around 50 bucks. He did some searching in his cattle-dog and a blanket of around 75 wide and 100 long hit the tarmac at around 600 bucks.
After I regained my footing, I passed up on the blanket idea!

John

[Jackspira]

Hi grant, I looked into finding a 240 volt controller for a heat blanket a while back too, found a different suppleir on the net which I've forgotten, but they were a similar too high price.
When I get around to it I think I'll make my own. In issue 55 (spring 2006) Guitarmaker magazine, there is a good article by an American called jack Clark. He describes in detail how to make a controller from parts that cost him about US$100. The three main components being a solid state controller, a thermocouple heat sensor and a relay ( the controller he used is limited to 2 amps so a relay was needed- I havn't tried to source one here yet but I imagine it would be a similar situation)
Its a good article with a clear wiring diagram and a list of bits.
I'm pretty crapo at electronics, but my dad is a retired electronic engineer so I'm confident he'll be able to sort out the mess after I've had a go.
For now its just one of the many things I'm procrastinating about. Your welcome to have a look at the article if you like

Jack

[Jackspira]

heres the one I found on the web, I found it agian. I don't know anything about it though! http://www.omega.com/ppt/pptsc.asp?ref=CN-TOT&Nav=heam03
Jack

[contrebasse]

my blanket from watlow is 18" x 10" and cost $230

you can use a standard stove element controller to regulate the temperature.

[Jackspira]

you can use a standard stove element controller to regulate the temperature.

A stove controller eh? (mr burns voice) That sounds brilliant, is that what you have used contrebassse? Can a stove controller measure the actual temperature, or does it regulate by simply switching on and off at different rates?
Jack

[Strungout]

Saw your posts in OLF Grant. If cost is a factor then go for light bulbs. Make sure you run your bender off a timer so you dont set fire to your expensive rosewood sides when you walk away and forget about them.

While youre humming and harring about which route to take with the bender you could put the time to good use by whipping up some sides on a good old fashioned bending iron...its not as hard as it looks and its fun.

I have gone through this exercise and found that trying to get the blanket down here was just too expensive .
After your advise regarding the bending iron Martin,I started to have a play around with a piece of 100mm Aluminium tube ($10.00) and a hot air gun ($50.00).

I only bent up a piece of scrap but it got hot fast and it did work.

I am also going to stick a 12 Volt 50 Watt halogen lamp inside it to see if that will work.???? I will let you know

These might be able to be used under the bending "jig".They seem to get hotter faster than a normal lamp and also are Low Voltage.

[gratay]

In regards to the stove thingy.....apparently a lot of people use router speed controls to work like a dimmer as the blankets are somewhere around 1000w and normal light dimmers can't do that sort of wattage...

but again my knowledge of all things electrical is very limited and how you would connect this upto work is beyond me

[kiwigeo]

Grant, you could get your friendly sparky to do it for you. I got mine to check wiring on my bulb powered bender before I cranked it up. He did it for free while attending to other electrical jobs in the workshop.

[kiwigeo]

I am also going to stick a 12 Volt 50 Watt halogen lamp inside it to see if that will work.???? I will let you know

These might be able to be used under the bending "jig".They seem to get hotter faster than a normal lamp and also are Low Voltage.

Halogens are more efficient at converting electrcity into light...that could work against you. I dont know if theyd get hot enough to efficiently heat sides. You'd need to have quite a few of them and theyd need to be close to the work. Let us know the results of the experiment.

[contrebasse]

A stove controller has a tiny internal bimetallic element that heats up - an internal and adjustable thermostat. It controls an element typically about 600-800 watts. I didn't use it on my heat blanket but I have heard of people using them successfully.

Malibu?

Low voltage is also inefficient because a lot of the energy is lost as heat in the transformer. standard bulbs are cheap as chips and very efficient at heating!

a heat gun, like a blowtorch, is NOISY

[Jackspira]

Thanks contre, I'm actually seriously looking into the whole thing, at my usual glacial speed, and had not come across that idea before.
Jack

[contrebasse]

How a stove controller works

http://www.appliance411.com/links/jump.cgi?ID=303

A 900 watt heat blanket on a 240v supply will draw 3.75 watts according to my calcs.

Your average stove controller should be able to handle up to 15 amps, that's about 3600 Watts. Enough for you?!!!

matthew

[Malibu]

Gday guys
That website looks pretty good for a description on stove controller operations (and I'm sorry, it's been about a zillion years since I had anything to do with them).
The other thing that MIGHT work, is a three heat controller form an old electric blanket. They switch (dredged up from from my feeble memory) two sets of elements into:
a) both elements on full power on setting 3
b) both elements in series, reducing the heat by half on setting 2, and
c) one element on full power on setting 1.
Once again, it's been soooo long since I had to do anything with 3-heat controllers, I couldn't be sure, but that's pretty much the gist of it.
It may give enough control to be use in bending sides and will have plenty of current rating for side bending heaters.
Of course, you'll have to argue that one, and why you need the electric blanket in the workshop with "the Mrs" on your own!!
If she asks, you've never heard of me :D

The other thing that would be quick and easy is the light dimmer. they're not really a high current rating, but will handle 150W globes without any problem. They're basically Active in and load out... there's no rocket science in connecting them up and I think they come with instructions anyway! I use one to control the speed of my Dremel and does a sterling job too.
You could easily (and cheaply) use one for each globe you have in a bender, but I wouldn't use one for a blanket... a blanket would probably use too much current for a dimmer controller.

Just as an after thought.. you budding home-sparkie's please, please, PLEASE be careful mucking around with wiring on house mains. Believe me, the stuff hurts when it gets hold of you and unfortunately, sometimes far worse. I personally know 7 electricians who have come off second best with a tangle with live circuits and one of them tells no tales.
The general rule, if it looks dodgy, it probably is! Just remember the earth and stick an RCD on to be sure!

John

[Malibu]

Sorry, I meant to say too that the low voltage downlights are only rated at 50 Watts and are directional because they have a mirror back... Great light, but hardly any (useable) heat. Contre said it right in that the transformer uses a lot of the energy, and the heat source is transmitted out in one direction...

[gratay]

so contre, let me get this right...you just used a heat blanket with no temp control.. ?
because i have heard of people doing it....

They heat up very fast which i guess means you have to work fairly quickly ....but i"m guessing they don't cool down so quick if you had to switch off the power because it was getting to toasty
i will call watlow and see what options there are ....like if there is a lower maximum temperature blanket ? which would be perfect if you can get one that only goes to 320F or somewhere round that...

[contrebasse]

To be quite honest I didn't even try to measure the temperature.

Because you are heating the whole soaked rib sandwiched between two sheets of tin, (I used strips of frying-oil can!), and the blanket is in contact with the whole rib, it heats very quickly - about 15-20 seconds.

I turned the blanket on until steam puffed out the sides then turned the blanket off and tightened the clamps. It retains heat quite well. If it got hard to bend I gave the blanket another blast until the wood became floppy again.

[kiwigeo]

a heat gun, like a blowtorch, is NOISY

Heat guns are perfect for undoing epoxy glue after you install your truss rod in upside down!!

[gratay]

Thanks Contre,
I'm starting to feel that it wouldn't be so hard to do with just the blanket
as long as you stay there until its finished and don't take your eyes off it...which is how I'd be doing it anyway
If you have a meat thermometer touching the wood then should be able to monitor temp and with a spray bottle handy should work....if all else fails it wouldn't be so hard to whip the clamps off and get the blanket off your precious sides until things cool down....

Finished my outside mold yesterday ...today will start setting up (get my head around) jigs to make the sanding dishes....

[kiwigeo]

Grant, for best results you need to let your sides cool down with them clamped onto the mold. If you take them off while still hot theyre going to spring out a bit and youll end having to stick them back in the mold again and heat them up again.

[gratay]

Grant, for best results you need to let your sides cool down with them clamped onto the mold. If you take them off while still hot theyre going to spring out a bit and youll end having to stick them back in the mold again and heat them up again.
for sure...definitely.
I was just thinking if the sides were starting to burn it wouldn't be to hard to undo the clamps on the jig and separate the blanket from the sides until things cool down to start again
but you would need some heavy duty gloves i imagine to deal with that sort of temp

[kiwigeo]

for sure...definitely.
I was just thinking if the sides were starting to burn it wouldn't be to hard to undo the clamps on the jig and separate the blanket from the sides until things cool down to start again
but you would need some heavy duty gloves i imagine to deal with that sort of temp

Yeah youre going to end up with hot fingers....I suggest you nip down to your local foundry and borrow one of their fire proof suits and a helmet. Youd also better have the local fire station on standby whenever you do any side bending....they can take care of cooling down the bender with their hoses.

I still reckon you should forget about the blanket and go for the bulbs..sometimes low tech is best.

[gratay]

You may be right martin,
One thing that concerns me with the bulbs method is the fact that the sides arn't getting close to the heat until the bend has started.....which although i know this works just concerns me that still could be easy to apply to much pressure to quickly and snap a side where as the blanket seems pretty fool proof.....
but maybe the bulbs is just as easy and fool proof ...in that case it would probably be the safest and cheapest way to go?

Has yours got ceramic batons?

[Malibu]

A bit of snooping in my paperwork today and I've come up with this that might be pertinent to the discussion.
First two pictures are a scan from the RS Componants book and show temperatures of the bi-metalic sensors. As you can see, they're cheap as chips too.
Last picture is a possible circuit that might be helpful.
Description of operation:
The RCD is for safety and I haven't drawn a power point to save space. Basically, I've drawn the circuit for 3 controllers, but you could use as many or few as you need. All of them are in series and I've picked a some at random that could be good, ie: TH1 is part number 229-5834, TH2; 229-5812 and TH3;228-2541 and this gives 3 temperature ranges of 125Deg, 150Deg and 200Deg.
Looking at the circuit, if all switches are off (SW1 to SW3) the temperature reached will be the LOWEST range control... so at 125Deg, TH1 will open and turn the heaters off.
If you turned on SW1, the next LOWEST range will be TH2... so at 150Deg, it will open and turn of the heaters... For the next range, turn SW2 on and so on down the line...

This is a really simple and cheap way to control the temperature, but not very accurate due to the wide turn on/turn off span of the devices.
I've never used these before, but I would say they would be best mounted on an aluminium plate (which would need to be earthed) and outside the heater box (in the case of a fox bender with light globes) if possible. If you mount these inside the heater box, you would have to use high temperature fibreglass/nickel cable to withstand the temperature because "normal" wire is only rated to 90Deg C.

Any questions, I'll try and answer them as best I can :)

John

[Malibu]

Hmm, don't think the pictures went.. try again

[gratay]

thanks malibu,
Theres lots of good ideas coming out in this topic.....and I'm sure I'll have some questions for you after I've read it a couple of hundred times to try and get it through my skull.
seriously though ..looks like a cheap excellent idea....

as for light bulbs ..if you had a simple light dimmer on each bulb you would really be able to get the temperature right...is this possible?
I don't know how much dimmers are but probably pretty cheap as well

[Malibu]

There's no reason that you couldn't use a light dimmer on each lamp and you could even have a few lights running from one dimmer. They are rated at around 450W so could supply at least 4 x 100W globes.
A quick hunt on the web and I came back with a price of around $50 each so it's still an affordable option.
The only drawback that I could see is not knowing what temperature you're running at. I've tried bending scraps at different temperatures and found around 135Deg C to be a pretty good mark to go by. You could get around this problem with some sort of thermostat or dial gauge to show the temp, but it all adds to the cost of course.
I've used a dimmer to control an infra-red ceramic element to heat my home-brew kit, but gave up on it because I couldn't quite get the temperature to what I wanted, even with a visual indication (Temperature strips) to show the current value... I admit, I was only looking for 28Deg, but I had a hell of a time trying to jiggle the knob to get the right control. I prefer something more tangible that I know has consitency every time.
Anyway, this is all about ideas, so I thought I'd toss in my 2 bob's worth :)

[kiwigeo]

3 bulbs...1 x 150 and 2 x 100 watt will work. If you need a bit more heat go to 2 x 150w and 1 x 100 watt. You won't have room for 4 ceramic bulb sockets if your bender is a fox based design. One dimmer only needed on all the bulbs..keep it simple.

To monitor heat use a meat thermometer (or two) as close as possible to the top of the form. On my bender the thermometer protrudes out one side of the jig so its easily monitored. Also use your ears and eyes and nose to tell if things are starting to cook...the smell of burning brazillian rosewood is a bit like a corked wine..its a smell you dont quickly forget!!

Having said all that....my bulb powered bender generally sits in the corner covered in dust....I do most of my bening on an electric iron. Call me old fashioned..call me stupid...but I just loooooove working on a hot pipe!!

[kiwigeo]

You may be right martin,
One thing that concerns me with the bulbs method is the fact that the sides arn't getting close to the heat until the bend has started.....which although i know this works just concerns me that still could be easy to apply to much pressure to quickly and snap a side where as the blanket seems pretty fool proof.....
but maybe the bulbs is just as easy and fool proof ...in that case it would probably be the safest and cheapest way to go?

Has yours got ceramic batons?

Grant,

1. start your waist bend on an electric iron and then stick it in your bending jig. This reduces risk of rib breaking as you apply the waist clamp. If you sandwich your rib with thin sheets of Stainless steel (Stewmac supply them) and apply the clamp slowly then risk of the rib cracking is further reduced. One of the advantages of using a pipe is your hands are always in direct contact with the rib and you can feel (and often hear) when its about to yield and adjust pressure accordingly.

2. you MUST use ceramic bulb fittings in your bending jig. Standard plastic fittings will melt. Check out herpatology supply websites to source ceramic fittings. Im out on an oil rig here in NZ right now so dont have access to my info on the latter. Just do a google search on herpatology supplies and make it an aus specific search.

Cheers Martin

[bobz]

I would just like to clarify a point about using the Fox jig with light bulb heating. I purchased the video from LMI demonstrating the use of thier Fox jig, and using the light bulb method is very efficient. First the steel slats are placed in the jig and bent round the form as you would do bending the sides. The bulbs are switched on for about 15 minutes to get the slats nice and hot. Release the slats, place side between slats and start bending at the waist slowly. After the waist has been bent, back of the screw one or two turns and then bend the upper bout then the lower bout. Once done, screw the waist down fully again. Gloves will be required during this operation. On the video, he did burn his forearm once. :D

I`m using heat belts on my bender because I want to bend a serpentine cutaway half for my guitar and I think the light method would`nt work so well with the sharp bend required. The slats would have cooled down too much by the time I came to bend this part of the side. But for bending non cutaways, I would go for the light bulb method because it`s cheap and it works very well.

[Malibu]

Here's a photo of my over-engineered, over-priced and over-powered bending iron.
An Omron temperature controller with a 250W element in a 2" round bar of aluminium and a PT100 temperature sensor. (Still cold, because I only turned it on for the photo)
It's worked great so far on the scraps that I've used it on, but the test is yet to come when I get around to doing some "real" sides.
The thing I like about it is I can dial up any temperature I want and I can read it on the screen. The biggest down side is the cost, which is probably somewhere around the $600 mark...
I did find out early on that 250W is way too much heating power for bending guitar sides, but with no starting point, it seemed like a good figure to begin with.

[Malibu]

hell, this time I forgot to attach the picture!
I'll get it together one of these days!!! :rolleyes:

[gratay]

I would just like to clarify a point about using the Fox jig with light bulb heating. I purchased the video from LMI demonstrating the use of thier Fox jig, and using the light bulb method is very efficient. First the steel slats are placed in the jig and bent round the form as you would do bending the sides. The bulbs are switched on for about 15 minutes to get the slats nice and hot. Release the slats, place side between slats and start bending at the waist slowly. After the waist has been bent, back of the screw one or two turns and then bend the upper bout then the lower bout. Once done, screw the waist down fully again. Gloves will be required during this operation. On the video, he did burn his forearm once. :D

I`m using heat belts on my bender because I want to bend a serpentine cutaway half for my guitar and I think the light method would`nt work so well with the sharp bend required. The slats would have cooled down too much by the time I came to bend this part of the side. But for bending non cutaways, I would go for the light bulb method because it`s cheap and it works very well.
thanks bob for the very informative description of how it actually happens...
Do you soak your sides?
and how much time roughly does it take for the first waist bend......I know this is different for each species and the variables with different temps and wetting timber times or at all......... but I'm just trying to get an idea of the time frame ...is it quite a slow process winding it down?
thanks

[Strungout]

Here's a photo of my over-engineered, over-priced and over-powered bending iron.
An Omron temperature controller with a 250W element in a 2" round bar of aluminium and a PT100 temperature sensor. (Still cold, because I only turned it on for the photo)
It's worked great so far on the scraps that I've used it on, but the test is yet to come when I get around to doing some "real" sides.
The thing I like about it is I can dial up any temperature I want and I can read it on the screen. The biggest down side is the cost, which is probably somewhere around the $600 mark...
I did find out early on that 250W is way too much heating power for bending guitar sides, but with no starting point, it seemed like a good figure to begin with.

Hi Malibu,

Do you have any details on the element you are using.Brand ,price and where you got it?

Thanks

Greg

[contrebasse]

Interesting to hear about pre-heating the steel straps. What thickness are these? Don't they cool down fast when you have to put the sides in the bender?

And ... all this talk about getting the temperature right!

When the wood is wet and cold, it doesn't bend. Seems to me, when you heat it up it gradually becomes more plastic until you can feel it give. When this happens, the temperature is right. If the rib doesn't bend, you don't force it, just keep steady pressure on and it will relax at the right temperature.

The wood isn't likely to cook unless you walk away from the whole thing. Certainly won't catch fire.

[kiwigeo]

When the wood is wet and cold, it doesn't bend. Seems to me, when you heat it up it gradually becomes more plastic until you can feel it give. When this happens, the temperature is right. If the rib doesn't bend, you don't force it, just keep steady pressure on and it will relax at the right temperature.



One of the key "tricks" to bending without breaking....and IMO its something youre much more aware of when you hand bend on an iron. Even if you plan to do most of your bending work on a jig I think its worth doing at least one set of sides by hand just to get a feel for how the wood responds to heat.

[kiwigeo]

Do you soak your sides?
and how much time roughly does it take for the first waist bend......I know this is different for each species and the variables with different temps and wetting timber times or at all......... but I'm just trying to get an idea of the time frame ...is it quite a slow process winding it down?
thanks

Grant, some people soak their sides, others lightly spray with a squirt bottle while others dont use any water at all. I use a Windex sprayer bottle filled with distilled water which I spray on the side of the rib thats having the heat applied to it. I just spray enough water on to get the wood damp, I dont saturated it.

Time....on a bending iron it usually takes me about 20 minutes to get the bend into the waist using 2mm thick Indian Rosewood. On banding jig it would be a bit quicker.

[Jackspira]

Even if you plan to do most of your bending work on a jig I think its worth doing at least one set of sides by hand just to get a feel for how the wood responds to heat.

I couldn't agree more! As with the thicknessing we were discussing a while back, learning to do it by hand first will really give you a head start whatever method you end up jigging for. It also, I think, can help to get into the actual bulding process faster with less distractions making setups ( which is kind of an endless process in itself?!)
Jack

[contrebasse]

you're right, of course!