Official Luthiers Forum!

While I use those timers on my blankets I never walk away with that thing running, but I routinely use them on my glue pot and as a safety mechanism in case I leave the bending iron or the soldering gun on (which I hate to admit I have been known to do).

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Brock Poling
Columbus, Ohio
http://www.polingguitars.com

Heck I never leave the shop anymore with out flipping the breaker on all my outlets. After I burned up the top on the Ovation repair this past year it has become a religious practice. One excptions is a IR light rig in my finish room and I do have worris about it but to speed curing I need to be able to leave it on over night at times

      I use the 15 minute timers and there is a control that is out there. Protherm has some as watlow and omega. They are in the $350 range.
      I also ebonized a set and ever since I DONOT let the machine alone. We all got lucky once.
john hall

I'm not so sure that it's the timer that's all important here. Seems to me like temperature control is more important. If your bender is built properly (insulated against heat) you should never have to worry about a fire unless you lose temperature control.

What are you guys using to control your temperature? If you just plug these types of thing into your mains outlet, you'll only get one temperature - flat out. And that will reduce the life of your blanket.

In the lab I use heating tape all the time (pretty much the same sort of thing, but in a long narrow length for wrapping around equipment, pipes, whatever). I always use a PID type of controller with a thermocouple that sits under the tape, I'd never even try using one without a controller, I'd burn down the lab for sure. The controllers cost maybe a couple of hundred $$, a bit less if you can assemble it yourself. You can just punch in the temp you want into the display and the heating tape (or blanket) will stay at that temp all day to within a degree or two.

just my 0.02

Most of us are using a reostat type controler like a router speed controler. they work well but you have to use a thermometer to gauge temp.

Thanks, Paul. The more we hear of such close calls, the more prominent our near- disasters stay in our minds, and the more mindful we are when working with these potential hazards.

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now known around here as Pat Foster
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http://www.patfosterguitars.com

Yes, I've got it on a heavy duty reostat (sp), as well as a timer. All wired together so if either one is off the whole system is off. After doing some testing, investigating and lots of time on the phone with omega, I'm pretty sure I've got a bad blanket. This was the first bend I made with it. Everything else in the system was EXACTLY the same way I've been successfully bending for 5 years. The last piece I bent had a scorch lengthwise down the middle of the blanket. On that bend the temp didn't get above 282? which is nowhere near hot enough to burn wood. So I think they did something wrong on the blanket. And yes, I'm mad about it. It's screwed up 3 sets of sides, one bending form, a second blanket and almost burnt my $#%@ shop down. Yes, I should have been there watching it like a hawk, and like I will always do in the future.

Paul Sorry to hear about the scare, and losing the wood. Happy to hear that you caught it in time to save the shop.

Al

Just a thought.

Those blankets draw a lot of current. If you were drawing more current than the timer switch was rated for, then maybe that overheated and stuck in the closed (ON) position. I think 2 of those blankets would be drawing more current than one of the 15amp timer switches is rated for.

You did mention that you thought the blanket was bad, so this may not have been the problem, but it might be something for others to concider when using more than one blanket.

Thanks for the heads up and thank goodness disaster was averted.

johno38764.8538194444

Actually Paul Time is alot more important than you are giving credit. Though temp is important 450 degrees won;t scorth if you are the a minute or 2 but 300 will if left 30 minutes.
Reguardless the point is NEVER LET A BENDING MACHINE UNATTENDED. I did and I was lucky , just a smokey shop and lost a $40 set of Mahogany.
   John Hall
blues creek guitars

Paul B. Besides the timer, some of us use 1000 watt commercial light dimmers, others use router speed controls for temperature reduction.

Most of us use it full blast until it starts approaching bending temps, then reduce power.

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http://www.dickeyguitars.com

Hey, I don't mind being wrong. I'm wrong all the time. But, I'm really in two minds about this set-up. One of them must be wrong

This kind of set up, without any temperature control, no temperature ramping control (other than the jerry-rigged stuff). I wouldn't let anyone set-up and use this in my lab, no way. If something went wrong and someone was hurt, I'd have some explaining to do to the authorities, and would be lucky not to end up in the big house.

But, I'd probably find this acceptable to build and use at home, even though other people who use them stress the fire danger.

As I said, one of them must be wrong.

Or have I spent to much time on OHS BS?

Paul

I think you are correct, the Rheostat is a simple system that works effectivelyand is cost effective, but as others have suggested it must be monitored as all you are effectively control is the input of the current, you are not directly controlling the temperature, this system takes no account of heat build up, Variance in input current, or Malfunction except by Manual intervention.


The system you talk is very similiar to the trace heating system I used at my old company, where temprature data is fed back to the controls and the controls adjust the input current accordingly.

The issue with either system though is once the water is gone, is the temperature enough to ignite the wood or any part of the bending machine ?

If it is then neither system is fail safe, Belt and braces would be a smoke heat that can cut the current before combustion occures, or a bending setup that could contain a fire.RussellR38765.3353472222

[QUOTE=Bobc] Paul I have a setup like that. The blanket has to have a sensor built in. I don't know all the electrical end of it. I bought the blanket and temp control from Tom at Doc's mandolin. Don't have his e-mail but I thing you can use google to find him.[/QUOTE]

I have Toms bending system built in thermocouple and timer. very pleased and he is one of the good guys his email is Docsmandolins@aol.com Mark

Sorry for the problems Paul but very happy there was no serious damage to your shop or yourself. As for safety, it could happen with other bending equipment as well. Even with a thermocouple you couldn't totaly rule out a system failure and potential fire. Its best just to stay focused on the task at hand and make sure everything is shut down when finished. Thanks for the post as we always need to be reminded of the safety issues.

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Don Atwood
Arlington, VA