Primitive Archer
Main Discussion Area => Bows => Topic started by: simk on September 25, 2019, 02:09:52 pm
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Hey Bowyers
Thought there might be too little heat treating threads around here 8) therefore starting another one:
Heat treating mostly seems to be done with the heat gun. Me myself having bought my third heat gun now in two years...got a little annoying. Also there is always the hot-air-flow-issue endangering the back, not talking about the lame-shoulder-effect after a heat treating session as badger does it and i also did ::)
bought a cheap quartz radiator for 20 bucks last week (1500w 1200w).
I did heat treat a whole bow which worked really really well and comfortable. The radiation is heating only the wood in direct sight - the back in the shade remains completely cool until the heat having creeped through the whole bow. The result was a very evenly heat treating as you see on the pic. Today I did a heat correction on a little elb - pic 2.
I must say heat treating by radiation works very very well. I will still use the heat gun but only for smaller spots.
Cheers
Edit: Temp is regulated with distance - for the heat correction on the elb I didn't need too much heat. For the real heat treating the distance was about 2-3" and the heat treating took about 10-15 min until the back of the bow was untouchable...
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Hmmmm, I was going to buy a heat gun today but now im rethinking! ahhhhhhhh! the indecision! ::) ;D What made you think about doing this. Like what made you think about using a radiator?
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deerhunter: i thought about this already long time...but to be honest, it was also b2w who reminded again me when we talked about it this summer ;D
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Thought there might be too little heat treating threads here 8) therefore starting another one:
(lol)
I just watched the documentary and series on Chernobyl so I was a little nervous seeing your title.
Do you have to move the bow a few times? How long did it take vs a heat gun?
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Ben: Don't need to move the limb - after 10 minutes the wood starts to get brown, then it starts vaping, then the back gets really hot and you are done. don't have much expierience yet. still have to experiment with the 2 variables (time and distance). have fun!
when I used the heat gun it took me about 15 min for a whole limb - i did it lmoving up and down very close with my 2000w heat gun.
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so the belly is supposed to smoke/steam? sorry but i'm heat treating a bow for the first time.
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yes, after a certain time the whole bow starts steaming/fuming - like your pizza when coming freshly out of the stove ;D
you should try it with your problem bow and will be surprised, i'm sure about that. me myself have had several miracles with heat treating and i'm also still a beginner
The radiator for me is a multi-purpose gadget: It will solve the gelling-problems when sinewing from now on and I will never freeze again in my shop in the upcoming winter
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That sounds like the perfect solution, Heat scorching the back has been a constant annoyance. I think I will go this route
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I made one of these(sorta) a few years ago although mine was made with an old 1500 watt heater(wire coil type). It works great for straight bows but if they are a bit wonky mine wasn't wide enough. Yours has that covered I think but what about reflexed limbs. Mine would heat the center(end to end) more than the ends, sometimes way more depending on the amount of reflex. Is there a difference between radiant and the coil type heater I used?
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steve: i'm feeling honoured 8)
don: yes, that's a point to consider - the bow I heat treated was a d/r, so i had this problem. in that case i had to do the limbs in two steps. you either then change the bows position or the lamps position so that the distance is always good. i finally got the middle of the bow slightly double-treated that way, what wasn't bad anyway to better preserve the reflex-bend. there are no perfect solutions in our imperfect world - still adjusting and fooling around is needed also this way. Sure you will find solutions...
In this case I clamped the bow on the caul then put the radiator in position. Did lot's a hooks on the ceiling so that i can easily change the radiators position to where its needed.
by the way: buy a radiator long enough. I was impatient and just bought the one they had, which is slightly too short for longer limbs. I will look for a longer one then...
cheers
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If someone could build a flexible radiant heater that could be adjusted to any shape I bet we would all get one.
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I can bend mine slightly to compensate for reflex but too many bends will probably break it. It's only 2" wide so sideways stuff is a problem. I don't want to jump all over simk's post but I've had this in the back of my mind for quite awhile and maybe many minds can come up with a solution. I hang mine from chains so i can just hook it in different links to vary the height.
Simk, you mentioned that yours is too short. How short do they come? Maybe two or three of them end to end might be a solution. Mine is pretty critical of height/distance above the bow. Having them hung by chains I also thought that maybe a mechanism that would swing the heaters lengthwise would even out any hot spots. I tried just swinging it but it only goes for a few seconds.
Anyway here's mine.
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I dont know if i can find a 20$ one like you simk!
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Best I can find is $100-$200
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quick update before work: when i first looked the www. the price range was chf 150-250. i found one for around chf 70.-
when i went to the big store there was this absolute white label product from china for chf 19.95
i also was offered a second hand radiator for chf 25
IMPORTANT: MINE HAS ONLY 1200W (checked again - sorry) AND ITS PLENTY SUFFICIENT
cheers
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There are flexible heating elements and coils available for fairly cheap online. I’ve been fixing to wire one up for a while now but got caught up tinkering with a light kiln. I have a couple styles on the way, I’ll play around with them hopefully this week and see if I can get a design going.
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I searched and all I can find so far in flexible are silicone(not hot enough) or elements that are flexible once before you heat it up. Once they've been heated they're rigid. The wire coils from the common heater work well if you can find insulators to support them. Then I need some kind of support that can be adjusted to varying curves to match the bows limb. It has to take the heat. Also since we're kind of limited to 1500 watts(15 amp breakers) a reflector to concentrate the heat is nice but then it also has to flex. Any ideas.
Simk- do the radiant heaters put out more heat than the conventional wire coil or is there a lot of hype involved :D
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I crossed my mind that you could put a straight limb under the heat and poised over the caul. When it was all cooked you could just quickly clamp it to the caul and let it cool. I sort of tried this once with less than stellar results but I was heating with a gun so the whole limb wasn't hot.
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DC: I'm no scientist nor have I any special education...On wikipedia I can read the following about quartz infrared heaters: Electrically-heated infrared heaters radiate up to 86% of their input as radiant energy. Nearly all the electrical energy input is converted into infrared radiant heat in the filament and directed onto the target by reflectors. Some heat energy is removed from the heating element by conduction or convection, which may be no loss at all for some designs where all of the electrical energy is desired in the heated space, or may be considered a loss, in situations where only the radiative heat transfer is desired or productive. For practical applications, the efficiency of the infrared heater depends on matching the emitted wavelength and the absorption spectrum of the material to be heated.
Finally I just tried this one and it worked well for a proper heat treating in a relativly short time. Still I think also your oldschool conventional wire coil should do the job. What results did you get?
Practically I think it's easy to put the bow loosley on the caul then just heat it up with a good distance until it's hot enough to finally force it proper on the caul (stage one). Once fixed on the caul in the final position you closen the radiator and do the actual heat treating.
My actual r/d shown first was steamed onto the caul in the steaming bag - didn't have the radiator at this stage...I always put them loosley on the caul start steaming and after a while start clamping until i'm on the final form.
I did not claim a miracle all in one device processor but it's imho better than my old heat gun. Still curious with what santanasaur and shannon will come up then ;D I'm happy with my little progress at the time. cheers
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Well, I’m relieved. When I saw this post’s title, I was expecting to see a home-made nuclear reactor!
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I’m not saying I have any special heat treating solutions, or start a contest, this is just amateur experimentation. So far I’ve played with cheap flexible heating coils, one was for a dryer. I never found a nice support and it felt like an awful fire hazard, but would definitely be a solution if safety was managed. These are cheap, I bought them for $5-10 a piece. Silicone heat pads only get to around 250f which isn’t hot enough, but many of the cloth coated heating tapes/cables get to 1000. I’m waiting in the mail for one that gets to 900 and is a 1/2” by 48” strip, so hopefully that will cover a limb at a time. Supposedly it remains flexible through use. Ive also seen several tapes/strips for heating frozen pipes that claim to get around 400, but need a temperature controller which can be expensive.
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DC: I'm no scientist nor have I any special education...On wikipedia I can read the following about quartz infrared heaters: Electrically-heated infrared heaters radiate up to 86% of their input as radiant energy
I think I remember reading that conventional heaters are about 75% efficient but that was in the context of heating a house. No idea where the other 25% went ;D
I think the wire coil will do the job and if we come up with something better we can change up. I did two or three bows with mine but for wiggly reflexed staves i went back to the gun. I will try the radiator again but it will be a while. The horn bow is about ready to shape and I seem to be building an "N" gauge model railroad for/with my grandsonm ;D
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DC: I dont think those %-numbers are really important. it's only about bringing the wood to a certain temperature, which can also be done with lower efficiency - i dont care about the electricity-bill in this case 8)
santanasur: i really think you could be on a good run - alone i^m not talented in tinkering electrical devices but will be the first ordering yours ;D
cheers
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I occasionally used a heat gun in the way Badger does. But it was too noisy and tiresome. I started collecting heating coils and even fans to make a heating panel to be hung over the limb. I thought about using a radiant heater. Too much energy and somewhat dangerous. Finally I decided to buy the silicon heating blanket used to bend wood for string instruments. It does go up to 200C (392F) using just 300W. I think all I need is 170C (338F) that will make the wood plastic. But the belly started to burn at 150C. The belly was almost black and smoking probably after 30 minutes. I did put some wood blocks on top to keep the blanket in contact with the belly. Not a good idea? That was the first try about two weeks ago. I have not stringed the bow yet.
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If someone could build a flexible radiant heater that could be adjusted to any shape I bet we would all get one.
the refrigeration industry uses long resistive elements marketed as "evaporator condensate heaters".
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Thank you scp! Hoping for more details incl. pics soon! I did also google these silicon heating blankets some time ago; they aren't too cheap, are they? Cheers
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Willie, those heaters are simple cal-rod heaters. Same as the cooking rings on the top of an electric stove. They will not handle much of a bend before breaking the internal element. They are designed for primarily for conductive (in contact) heat. Used solely in a convection application they will burn out quickly.
Using radiant heat is an option I hadn’t considered. Radiant heat waves heat only the objects the waves come in contact with adding an element of control to the process. so I’ll be keeping track of this thread for solutions to the raised questions.
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I occasionally used a heat gun in the way Badger does. But it was too noisy and tiresome. I started collecting heating coils and even fans to make a heating panel to be hung over the limb. I thought about using a radiant heater. Too much energy and somewhat dangerous. Finally I decided to buy the silicon heating blanket used to bend wood for string instruments. It does go up to 200C (392F) using just 300W. I think all I need is 170C (338F) that will make the wood plastic. But the belly started to burn at 150C. The belly was almost black and smoking probably after 30 minutes. I did put some wood blocks on top to keep the blanket in contact with the belly. Not a good idea? That was the first try about two weeks ago. I have not stringed the bow yet.
This sounds very promising although the numbers don't work for me. When I heat treat the wood doesn't start darkening until my thermometer reaches 400°f+. maybe my thermometer is wrong, don't know. How many times would this heater last using it like this? How expensive are they? Where can I read about them? etc etc
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This was my first Google hit. It mentions 400°
http://www.scavm.com/blanky.htm
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Not trying to hijack the thread but does anyone else recall a fella cutting a hole in the back of his microwave, I believe it was an old Amana Radar Range (sure looked like the one we had IIRC). Anyway, like others, the heat gun is a slow and noisy way to go but it does work and is likely a lot safer than microwaving the stave.
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That is how Bubby does it, I think. Most of us are too cautious(read chicken ;D ;D)
I found this video. https://www.http://www.scavm.com/blanky.htmyoutube.com/watch?v=EI6K7IHq0a8
He uses lower temperatures but he does say that a few fires have been caused with these which sounds promising. I'm intrigued. More reading :D
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I found an outfit, Omega Engineering, that makes these. They make one that's 3" x 24" for about $75can. I'll give them a call and talk about our application.
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Eddie Parker(Mullet) cut holes in the side of a microwave for heat bending bows. I think he stuffed rags around the bow at the holes to seal in the goodies.
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I got my silicon heating blanket from the biggest online retailer. Not cheap but quite reasonable. I can justify its use as "primitive" because similar effect can be achieved by using several heated stones on top of the belly. I did try to use the smallest iron once. Too flat and stiff bottomed to use effectively. And it will take too long for modern people.
Radiant heat from coal bed or bonfire might be more authentic, but the primitive did use heated stones for cooking. And so far as I know, many old bowyers burnished their bows, especially on the back. They could easily have done the same on the belly with very hot stones.
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I talked to Omega's tech department and he said that about 430°f is the point at which the heating pad will start to fail and that heating bows might just be too close to the limit. But he did say that if you could keep the temp below 400 it should work.
scp- I'm not to concerned about "primitive". If the end result could be conceivably built by primitive man that's good enough for me. Anything else you can tell me about these things would be appreciated. How many times have you used yours? I'd hate to spend $75 and get 3 uses out of it. Do you control the heater with anything? Monitor the temp? that kind of stuff :D
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DC: We probably need to start a new thread, as using a radiant heater is a good topic by itself. My heating pad comes with a thermostat at a similar price. I just used it twice. If you use it following the instruction (I didn't bother), it should last indefinitely. I don't trust its thermostat. Better use an instant or laser thermometer and keep it under or around 170C (338F) for less than 20 minutes. If you see smoke, you better turn it off. Good luck.
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Willie, those heaters are simple cal-rod heaters. Same as the cooking rings on the top of an electric stove. They will not handle much of a bend before breaking the internal element. They are designed for primarily for conductive (in contact) heat. Used solely in a convection application they will burn out quickly.
Using radiant heat is an option I hadn’t considered. Radiant heat waves heat only the objects the waves come in contact with adding an element of control to the process. so I’ll be keeping track of this thread for solutions to the raised questions.
Beba,
those heaters are a bit long for the rated voltage, and don't get red hot like the stove type. a buddy that installs them reports they can be bent using a tubing bender, at least before they are fired up. he said he never tried to rework one that had been in service.
If you have one it might be worth trying, but after giving some thought to the requirements for bow heating put forth in some of the posts above, I have been leaning towards re purposing a milk house heater. the coil could be removed and hung from something like a piece of stiff but malleable wire or some sort of support that could be easily be formed into the shape to follow the contours of the limb
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I have been leaning towards re purposing a milk house heater. the coil could be removed and hung from something like a piece of stiff but malleable wire or some sort of support that could be easily be formed into the shape to follow the contours of the limb
That's where I've been. I got stalled trying to find ceramic insulators of the right configuration and fabbing reflector/s. I like your idea of hanging the coil from a rod so what we need is insulators with two holes, one for the coil and the other for the rod. Could probably braze reflectors on in between the insulators. Hmmmm :D
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Don
keep us posted about the insulators you find. I am looking also. some sort of ceramic filament might be useful.
3d printing can do ceramic parts
thinking about a piece of flexible metal conduit for a support
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Maybe I’m wrong about this but I think it might be better not to use insulation at all. My thinking is that radiative heating hits the belly and absorbs or bounces off before affecting the back.With convection heating, hot air has a chance to go around and scorch the back. This is why I also like using the heat gun close up where you get more radiation to less hot air. If im thinking about this correctly, to get a deeper heat treat before the back starts scorching, air temp should be minimized while as much of the heat as possible comes from direct radiation and not hot air.
in cooking terms I think we want to broil the bow as opposed to baking it, for similar reasons you broil or grill a steak rather than baking it. This is why a salamander broiler in restaurants is open so that it doesn’t heat up and act like an oven. Insulation would make the rig a better oven but worse of a broiler.
On a separate note, if a good way to thermally insulate the back from the belly was found (badgers heat tape post) then convection would work without the issue of scorching the back.
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The insulators we are talking about is to isolate the heating coils electrically from the structure of the thing. They are just little ceramic buttons sort of. if that's not what you're talking about I'll shut up ;D ;D
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Nevermind then DC, I though you were talking about thermal insulation. Id really like to see a safe design with the resistance coil type. The one I tried nearly caught fire in my shop so I moved it outside, but when it rains it shorts out. It was a terrifying and rackety thing.
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What do you think about using emf protective clothes for heat treating? Just a thought. Sorry for bumping the thread.
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can you link to something like you are suggesting?
EMF protected clothes sounds like something you would want to be wearing if there was a nuclear bomb explosion nearby
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That looks like an excellent way to heat-treat a bow. I would consider this a major contribution to the craft!
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So...after 3 or 4 years since this thread started... what's being used now for heat treating?
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I still do the bed of hot coals method and just watch over it and monitor it closely. If I notice it’s getting a little hotter then I like I adjust the height and watch it toast slowly. 2-3 hours in good weather usually yields great results. The neat idea of the radiant heat set up with electric or gas fired radiant heat is that it can be controlled and set up in a shop if safety precautions are taken. Much of the guess work and repeatable heat treatment can be done from bow to bow. The obvious problem with the coal bed is getting consistent repeatable results from bow to bow. The last batch of bows I did this way were all heat treated same bed but some had deeper cook then others. Efforts are made to minimize this to some degree but invariably still get some variations in heat from spot to spot. To minimize some of these hot spots and get more consistency I’ll move bows around and shuffle them from spot to spot. It helps but the temp controlled electric heat treatment system set up would be ideal for consistency. Just my 2 cents.
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So...after 3 or 4 years since this thread started... what's being used now for heat treating?
This is the first I have seen of this post. I really like the idea but seldom make bows anymore. I will still probably get myself set up to do it. Several things I like about it. #1 By simply adjusting the distance you can control the temp. 2. I would set it up with a temp sensor on the back of the bow. # It might make it easier to monitor and test how heat affects the back of the bow, I have always wondered if keeping the back as cool as possible was better or bringing it up to a certain temp was better. Heat guns are kind of a pain in the ass when you need a lot of test samples.
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I have always wondered if keeping the back as cool as possible was better or bringing it up to a certain temp was better.
keeping the heat element above and radiating heat down to the belly surface seems to be key to preventing hot air going places you dont want.
if you were really concerned about the back and were using a form to hold your bow, then it might be reasonable to keep a wet pad between the back and the form. you could probally rewet it in place as it dries during the process and get a idea of the back temps by watching for steam