Heating Blanket - Temperature Control

Pete Brown · Post by **Pete Brown** » Tue Jan 13, 2009 10:19 am

With my Fox-style bender, I've managed well enough over the years with three 150W light globes, but I'm seriously contemplating a raid on the piggy bank and an upgrade to a heating blanket - they sound so much better in terms of getting even heat distribution.

LMI sell a 220V blanket but only a 110V temperature control, which leaves me having to source something locally.

1. What do you all use to regulate the temperature of your heating blankets?

2. If you were upgrading like me, would you retain the globes and use them in conjunction with the blanket?

kiwigeo · Post by **kiwigeo** » Tue Jan 13, 2009 4:53 pm

I got my 110volt blanket from Blues Creek Guitars. It came with a router speed controller which is the temp controller. The 110volt blanket is not the cheapest option as you need to buy a hefty step down transformer to run it on 240volt power.

Hippety Hop · Post by **Hippety Hop** » Tue Jan 13, 2009 5:34 pm

Hi Pete.

Recently I purchased a 240v blanket from Michaels Enterprises, which has two blue silicon coated power wires and a brown teflon coated J-type thermocouple wire all hanging out of it.

The power wires just need connecting to a power plug - active/neutral either way, then I found the Novus thermostat controller at Ocean Controls, but haven't figured how to connect it up yet.

I've used the blanket without the controller. Heats up real fast.

Cheers Hip.

Allen · Post by **Allen** » Tue Jan 13, 2009 6:23 pm

I got my blanket from Michaels Enterprises as well, with the thermocouple just in case down the road I wanted to use it. Their controller is probably the bees knees, but at around the $500 mark it's more than I wanted to spend.

So I hooked my blanket up to a regular 240 volt light switch that I built into a box, so the box could be near the bender. After looking at Bob's tutorial about bending, I went into Dick Smith and bought the same thermometer. Now it's as simple as slipping the thermometer between the slats. Turning on the blanket, approximately 2 minutes later bending commences at 100 degrees, and blanket turned off at 150 degrees. If the bend isn't complete, then I might cycle the blanket on and off until it's done.

Pretty low tech, but it was cheap and easy to do.

I had the lightbulb set up, but just scrapped it once I got the blanket. The blanket is just so fast and easy, that I wasn't worth using the bulbs. Plus using solid bending forms seems to give a better, and more consistent shape, than the hollow forms with the metal slat.

Pete Brown · Post by **Pete Brown** » Tue Jan 13, 2009 6:54 pm

The 110volt blanket is not the cheapest option as you need to buy a hefty step down transformer to run it on 240volt power.

Martin, your piggy bank must be bigger than mine.

Recently I purchased a 240v blanket from Michaels Enterprises

Great link - thanks Hip!

I've used the blanket without the controller. Heats up real fast.

Hip, speaking as someone who can enter the workshop three times in quick succession and get sidetracked on three separate projects, I really do need some form of self-protection!

Plus using solid bending forms seems to give a better, and more consistent shape, than the hollow forms with the metal slat.

Allen, that's certainly worth considering. I've occasionally had some cupping of the sides at the end of the lower bout, even with something as easily bent as walnut, and I've put it down to the uneven heating provided by the globes.

I think the blanket I was looking at at LMI is 1000W. I was hoping there was something as simple as a heavy-duty dimmer switch I could run in tandem with the El-Cheapo shut-off timer I currently use, but maybe there's no such thing.

Allen · Post by **Allen** » Tue Jan 13, 2009 7:14 pm

I'm by no means competent with electrical wiring. If there was a way for me to set something more fool proof up, then I'd probably do it, but I'm afraid it is going to entail a visit from a sparky.

One thing about my set up, is that it goes so bloody fast, you don't have time to get side tracked. If you do, then you've got more of an "Attention Deficit Disorder" than I do.

kiwigeo · Post by **kiwigeo** » Tue Jan 13, 2009 10:21 pm

Pete Brown wrote:Martin, your piggy bank must be bigger than mine.

Tim Spittle is my piggy bank

hilo_kawika · Post by **hilo_kawika** » Wed Jan 14, 2009 1:47 am

Allen, you really might consider the router speed controller mentioned above. It's all I've used for my heating blanket needs and "works a treat". I set it at ~2/3's power and I'm good to go. More details in my "toot" as posted earlier.
I think they run ~$40 USD. A used Variac or Powerstat might be another option. They're pretty cheap as well. Consult your local EE for details on their use.

aloha,

Dave Hurd
www.ukuleles.com

Pete Brown · Post by **Pete Brown** » Wed Jan 14, 2009 9:57 am

Dave/Allen,

I found an old reference in another forum to a 220V router speed controller sold by Timbecon, a woodworking supplier here in Perth, but it's no longer advertised on their web site.

I scoured the internet last night but can't find another source for one here in Oz. They are certainly a cheap option, but all those I found are from overseas sellers and are 110V.

kiwigeo · Post by **kiwigeo** » Wed Jan 14, 2009 2:22 pm

Heres something from Jaycar but its only rated to 600W continuous, 1200W maximum.

http://www.jaycar.com.au/productView.as ... &SUBCATID=

Bob Connor · Post by **Bob Connor** » Wed Jan 14, 2009 4:11 pm

This came from Dick Smith in kit form for about $120.

To be honest I don't use it. I switch it on full, start the bend at about 100C and turn it off once the bend is completed. A total of about 4 minutes.

Pete Brown · Post by **Pete Brown** » Wed Jan 14, 2009 4:34 pm

Great tip Bob.

Perhaps one of the low-tech solutions offered by Allen and yourself will do after all. Once I've checked that the house and contents insurance is up to date, I might just order a blanket and give it a try!

Seriously though, if it heats up that quickly and can be turned off a few minutes later, perhaps with normal precautions the more complex and expensive solutions can be avoided.

Allen · Post by **Allen** » Wed Jan 14, 2009 5:54 pm

I've had no problems at all Pete. In fact, before I got the themometer, I was letting it heat for 3 minutes and using the spritz bottle test. If it sizzles, then it's probably good to go. With the thermometer though, I found that leaving it this long before bending was a little too long. I did see the tinniest bit of scorch on some Blackwood.

If you have a switch handy to your bending form like I do, with the thermometer sticking in your face, it's pretty simple just to switch it on and off, if things are getting too hot, and your struggling to get the side in shape. With the bender that I built though, it's no more than 3 1/2 minutes and I'm done.

I've seen lots of reference to people setting there timers and temperatures for something low and then letting the sides cook for an hour or so, but I just let it cool down, then hit it again with the heat to 150 degrees and then let it cool down over night. So far the sides done like this have been better than any I did with other methods. No cracks, or scorching. and ripples are very minimal. Spring back varies from types of wood, but nothing that had to be touched up on the bending iron, though I like too do this if there seems too much spring in the side to coax them into the form.

Bob Connor · Post by **Bob Connor** » Wed Jan 14, 2009 5:59 pm

I will say that I pull up a stool next to the bender while I'm doing all this and my arse doesn't leave it until I turn the power off.

Too easy to get distracted by something else. I did it once just after we built the bender - it doesn't take very long at all to scorch the wood.

ZOOTMAN · Post by **ZOOTMAN** » Mon Jan 19, 2009 9:57 pm

bob wrote:I will say that I pull up a stool next to the bender while I'm doing all this and my arse doesn't leave it until I turn the power off.

Too easy to get distracted by something else. I did it once just after we built the bender - it doesn't take very long at all to scorch the wood.

And not much longer to scorch the shop.

How about a light dimmer switch with the proper V/W rating?
That's what I use but of course it's 110 V.

Taffy Evans · Post by **Taffy Evans** » Tue Jan 20, 2009 7:32 am

Bob, I find it hard to sit still for too long, so on my bender I have two timers, one is a mechanical kitchen timer that rings a bell if I'm distracted and the other is a power point timer that will shut of the power if I get called away. I set them both. They are set within the safety time limits and if they ring or shut off while I'm there I just reset them. This is a just in case measure I do not leave the bender either.

Pete Brown · Post by **Pete Brown** » Tue Jan 20, 2009 3:10 pm

I emailed Powerform Controls in Sydney about their range of motor speed controls and received this reply:

We have supplied other instrument builders with similar requirements. Either our MSL1200 or MSR2000 would be suitable. I would suggest the MSR 2000 so you have a good overload leeway. You may need this because your heater is rated at 1065W 220 V. At 240 V it will be drawing ~1170 W which is right on the max for the MSL1200. If you want continuous user adjustable power then the units to consider would be the MSC1200 and MSR2000+RC10. Both can be supplied as panel mount or on a wall plate with switch.

The unit they recommend - the MSR2000 - is $99 + $16 freight.

Have a look at their web site at http://www.powerform.com.au

kiwigeo · Post by **kiwigeo** » Tue Jan 20, 2009 3:52 pm

I start my bending at exactly 5 minutes before dinner time. I can guarantee that 5 minutes later an angry looking woman will be banging on my workshop door reminding me that workshop time is over for the day!

Pete Brown · Post by **Pete Brown** » Tue Jan 20, 2009 4:38 pm

As I traded in the angry woman for a more sedate model, and dinner time happens if and when we're hungry, I'll opt for the MSR2000 and set a predetermined upper limit of 300F or thereabouts. The additional RC10 control they mention allows you to more easily tweak the temperature threshold on the fly apparently, but I doubt that'll be necessary once I've dialled in a temperature that's working for me.

Allen · Post by **Allen** » Tue Jan 20, 2009 6:26 pm

Thanks for the link Pete. Are you going with the RC10 as well? A picture of the set up once it's up and running would be a great help to a lot of us.

Cheers.

Pete Brown · Post by **Pete Brown** » Tue Jan 20, 2009 7:11 pm

Allen, I don't have the blanket yet and the piggy bank needs to get a little heavier, so don't hold your breath waiting for pictures! The RC10 is another $32, so I'll buy one later on if I feel the need for finer control. I'm guessing it'll be a case of "set and forget" and I'll end up making do with the main unit alone.

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Heating Blanket - Temperature Control

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