# homemade oav



## rookie2531 (Jul 28, 2014)

I made an oav out of 3/8" thick x 3" wide x 4" long aluminum block. It was circular before I cut it square and has a raised rim 2.5" diameter plate. I drilled a hole just to the side of the dished side to accept the glow plug element. Then on the side of that has a set screw to hold it tight to one side of the aluminum. I even have a small piece of aluminum as a heat sink for the outer glow plug to screw on.

Well, I tested 1/2 teaspoon and the acid burned super slow. It took 10 minutes for it to burn to nothing( used fully charged car battery). I did a second test, this time the plate was pretty warm and it took 6 minutes, and when it did start burning it went pretty quick. The second time, the acid even boiled fast and spit a little.

The glow plug I used, I bought from eBay and was titled 12volt, but the actual glow plug itself had a stamp mark of 6V. Do you think maybe I have the wrong glow plug, because all the information, I have seen, says 1/2 teaspoon of acid should burn within 1-2 minutes. I have seen one were there were 2 glow plugs used in one block. Thoughts


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## crofter (May 5, 2011)

From your measurements it sounds like you have quite a bit more mass than some of the units that use one glo plug for a heat source. The mass in itself should only delay heatup, except for the fact of the additional radiating surface giving more heat loss. You could perhaps remove some material so that it had less than an 1/8th inch of material outside the bowl and it might gain you a bit. I am surprised that the plug with a 6v rating did not go poof. Is just the tip of the plug clamped to the bowl? In several of the threads there was reference to several recommended parts numbers. It could be that the model you used has a low wattage output.


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## Rader Sidetrack (Nov 30, 2011)

The Bosch 80010 is one glow plug that is often mentioned in homemade vaporizer threads. Here is one of those threads:

http://www.beesource.com/forums/showthread.php?286888-Home-made-Vaporizer-design

The 80010 plug is spec'd at 11 volts by Bosch: https://www.boschsparkplugs.net/product.aspx?zpid=15989


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## Dave H (Aug 23, 2014)

I built one recently using a Champion ch271 glowplug. It tested pretty good, but I haven't tried it out on the bees yet. It took ~ 2 1/2 minutes to cook off 1 gr OA. It's 2 1/2" X 2" X 1/2". This is my first attempt. On the next one I'll reduce the mass and make the pan a bit larger.
Regardz, Dave H.


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## rookie2531 (Jul 28, 2014)

crofter said:


> . Is just the tip of the plug clamped to the bowl? In several of the threads there was reference to several recommended parts numbers. It could be that the model you used has a low wattage output.


I drilled two different size holes. One for the heating element and one for the tapered outside part. The heating element is clamped tight and the tapered end is just barely in the hole. I did this to prevent heat lose out the hole, but still letting the element expand. The drilled hole is a little longer than the element as well. I am going to make a few adjustments. I do have the other glow plug and am going to make either a second one or combine the two for a faster burn.


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## Dave H (Aug 23, 2014)

The heating element in mine is a very tight fit. I had to heat the aluminum with a torch and put the glowplug on ice to get it in position. My thinking being that a tight fit means a more effective transfer of heat.


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## crofter (May 5, 2011)

The handle bolt being screwed directly into the heating pan is a very large heat loss. In some successful models the pan is held only by setscrew onto the element tip. The body of the glow plug is held tight to the heatsink which is also where the handle attaches. Even the body of the glow plug should be free of contact with the pan to minimize conductive heat loss. You only have 150 watts max to play with; you have to put it where it it counts!


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## Acebird (Mar 17, 2011)

crofter said:


> The handle bolt being screwed directly into the heating pan is a very large heat loss.


So why have any pan at all? Can't the powder be put directly on the glow plug itself mounted in a T fitting?


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## crofter (May 5, 2011)

Ace, tell us about your proposal and perhaps a drawing and we will critique it for you. If you have something that is more workable and simpler to fabricate than existing models you might be able to cut a deal with SNL one of our paying sponsors here on the forum.


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## rookie2531 (Jul 28, 2014)

I attached a second plug and ran the test again.
The results from a cold start to finish was 3 min. 30 sec.








OH, and the all thread did take some heat up 4", and I had to remove the heat sink in order to attach the all thread and second plug.


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## crofter (May 5, 2011)

Hey now you are cooking! You could still take more meat away on the sides of the bowl and if you clamped a cross bar from body to body of the glow plugs you could put the handle rod into that crossbar instead of into the bowl. That would drop your delay time considerably but that is workable as you have it. Nice!


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## rookie2531 (Jul 28, 2014)

crofter said:


> Hey now you are cooking! You could still take more meat away on the sides of the bowl and if you clamped a cross bar from body to body of the glow plugs you could put the handle rod into that crossbar instead of into the bowl. That would drop your delay time considerably but that is workable as you have it. Nice!


Oh yeah, great tip. I will do that. And the plug bodies will have a heat sink as well. Thanks for all the advise.


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## gman1001 (Sep 24, 2013)

I'm endeavoring to build my own as well. I just bought of these heaters on ebay. http://www.ebay.com/itm/PTC-heating...187?pt=LH_DefaultDomain_0&hash=item2343854693

They may be junk, who knows. Be fun to test though.


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## crofter (May 5, 2011)

gman 1001 How many of them are you going to use? They are only 10 watts each.


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## BudsBees (Mar 10, 2013)

I build and sell OAC on beesource too. The ones I make only take about 2 min to completely to do a hive.


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## BudsBees (Mar 10, 2013)

OAV


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## crofter (May 5, 2011)

Sorry BudsBees, I did not realize you were in the market too! I know from experience that a person can waste a lot of time trial and error to get all the variables worked out and have a good working vaporizer!


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## Acebird (Mar 17, 2011)

crofter said:


> Ace, tell us about your proposal and perhaps a drawing and we will critique it for you.


You start with something like this:
http://www.amazon.com/Stainless-Steel-Fitting-Class-Female/dp/B003GSKXFK
Put the glow plug in the long way and add a nipple (reduced) in the tee side to go into the hive. The glow plug would be upside down in use and you would fill then plug the top side of the tee.


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## BudsBees (Mar 10, 2013)

We have all of our kinks worked and can sell our OAV at a very reasonable price. We include some oxalic acid, a measuring scoop and instructions on proper usage of the vaporizer.


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## Rader Sidetrack (Nov 30, 2011)

Ace, the threads on that Tee you linked are NPT threads. How do you propose to mate that with the glow plug? :scratch: :s

The glow plug certainly does not have suitable NPT threads!


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## Acebird (Mar 17, 2011)

Rader Sidetrack said:


> Ace, the threads on that Tee you linked are NPT threads.


They are carving up solid blocks of aluminum. I would assume they have a machine shop where they could make an adapter.


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## Rader Sidetrack (Nov 30, 2011)

So if you are assuming that the full capabilities of a machine shop are available, then what is the point of your plan of starting with a "manufactured" Tee with NPT threads? :s

Why not just cut the appropriate threads for the glow plug directly into the vaporizer aluminum block to start with? :scratch:


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## Acebird (Mar 17, 2011)

FFF (form, fit, and function) and cost.

Form: The form is too massive causing delays before vapor is produced.
Fit: The bowl has to be placed inside the hive where you can't see what is going on.
Function: It is not convenient to use from hive to hive or box to box. It drains battery source. It takes forever to cool to recharge.

Cost: If you think you can make something from billet stock cheaper then from a manufactured tee go for it.


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## Rader Sidetrack (Nov 30, 2011)

> Form: The form is [HIGHLIGHT]too massive [/HIGHLIGHT] causing delays before vapor is produced.

Anybody that has _actually compared_ the size of the business end (tip) of a glow plug to the 1/2" NPT pipe Tee that Ace is advocating will realize that the *mass* of that 1/2" Tee is way to big for the tip of the glow plug!

Then add in the *mass *of the adapter that he is also promoting, and what do you have? A *massive *combination of metal. See earlier posts for the consequences of such a design. 

:kn:


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## Acebird (Mar 17, 2011)

Rader Sidetrack said:


> > Form: The form is [HIGHLIGHT]too massive [/HIGHLIGHT] causing delays before vapor is produced.
> 
> Anybody that has _actually compared_ the size of the business end (tip) of a glow plug to the 1/2" NPT pipe Tee that Ace is advocating will realize that the *mass* of that 1/2" Tee is way to big for the tip of the glow plug!
> 
> ...


I don't know what size tee should be used for the proper FFF. I will leave that to those that want to produce the device. The idea is to NOT heat the tee but to put the glow plug in contact with the acid. The tee should be sized to accommodate the charge such that the heat end of the tip is covered. The adapter can be figured out after the chamber is sized.


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## Rader Sidetrack (Nov 30, 2011)

.... sounds like you have put a _lot_ of thought into that design.


Why don't you post some pictures?


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## crofter (May 5, 2011)

I think he should give a thought to the temperature of the tip and the caution about not overheating the vapors;also the phenomenon of recondensing on parts of the apparatus that are not above the 320F. temp. There are multiple facets to the function and you fool yourself if you think they can be addressed simply in isolation. Do a search on Rube Goldberg inventions for further suggestions.


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## Acebird (Mar 17, 2011)

crofter said:


> I think he should give a thought to the temperature of the tip and the caution about not overheating the vapors;also the phenomenon of recondensing on parts of the apparatus that are not above the 320F. temp.


I would suspect the tip gets hotter than 320 if it is capable of heating a heavy mass to 320. A system of turning on and off the glow plug would solve this problem. You just need to validate the cycle to attain the temperature you want.

I did think about the condensing problem and there are a couple of ways you could approach the problem. You could prewarm the mass with a torch to keep the condensation to a minimum or you could let it condense until it insulates the heat transfer. The tube that extends into the hive box could be made of teflon. One would have to test these ideas as to their practicality.


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## rookie2531 (Jul 28, 2014)

Well, I cut the corners off and changed the all thread to connect to a heat sink. The results did not change. 3 1/5 minutes will have to do. It is alot better than trying to be consistent with that crack pipe


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## crofter (May 5, 2011)

I am surprised that relocating the handle attachment did not cut the heat up time. Is the body of the glow plugs tight against the bowl ? If so you have a heat loss there. If they are not in contact and you still have the electrical connection to the bowl, as in your picture, then electrical current path is through the heated tip of the plug. Inconel is a really poor conductor and hot inconel even more so. Give that a think and see if I am reading the situation correctly. Perhaps you should move that lead from the bowl onto the heat sink and plug body.


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## rookie2531 (Jul 28, 2014)

The bodies are touching the bowl, heat sink and handle as I have the negative wire at the end of the handle. I will loosen the set screws and pull them out just a bit and run a neg. Wire from the bowl instead? The heat sink got really hot and so did about 3" of the all thread. I am not sure what inconel is. I have the pos. Wired to both plugs and the neg. Wire is wired on the all thread handle.

I don't know if it matters, but the pos. Wire is braided and the neg. Is solid 12 guage.


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## crofter (May 5, 2011)

The tip of plug is made of inconel. Heat resistant but a poor conductor especially when hot. The electical circuit connection points should be A. the terminals on the glow plug and B.the body of the plug. polarity does not matter. Yes back the glow plugs out slightly and retighten set screws. Dont wire it so the bowl and the tips of the plugs are required to be part of the electrical circuit. Also it is probablly best that the length of the steel handle shaft also not be used as conductor although that would be a minor resistance.


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## rookie2531 (Jul 28, 2014)

crofter said:


> The tip of plug is made of inconel. Heat resistant but a poor conductor especially when hot. The electical circuit connection points should be A. the terminals on the glow plug and B.the body of the plug. polarity does not matter. Yes back the glow plugs out slightly and retighten set screws. Dont wire it so the bowl and the tips of the plugs are required to be part of the electrical circuit. Also it is probablly best that the length of the steel handle shaft also not be used as conductor although that would be a minor resistance.


OK, I will back it out and retest. Thanks Frank. I'll post updated pic after work. I am planning on using it this afternoon on the girls. Would it hurt to dip some of it in water to cool it down quicker? I wouldn't dip the part that holds the plugs, just the bowl.


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## BudsBees (Mar 10, 2013)

What is the gauge of wire are you using. Have you check the ohms of your glow plug . What size of bowl are you using? How thick is your base? The size of your base? These are all factors in building one.


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## crofter (May 5, 2011)

I splash a bit of water in my bowl until it just quits sizzlling; probably around 200F. as a guess. I can dump a new charge of OA in without any off gassing and it cuts about a minute off the heatup time.


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## rookie2531 (Jul 28, 2014)

updated pics, and that is 1/2 teaspoon spread out. The heat sink is touching the other glow plug threads, but since I didn't drill the holes for the tips with a drill press, they were not perpendicular and that is the only way I could do it.


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## nater37 (Aug 15, 2013)

My hives that have easy access, I was able to use my truck battery and it took 2.30 mins. I have some hives I cant reach with truck so I used a motorcycle battery and it took 4.30 mins to cook off. I put 20 feet of #12 wire and it is working great. But the amps from batteries make all the difference in how hot it gets for sure.


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## rookie2531 (Jul 28, 2014)

Very nice Nate. And good to know about the battery.


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