Newbie small oven build

[Stubbie68]

Hello all! As stated, new to powder coating and building my first oven. Starting small, very small but still want some descent functionality. Therefore I opted to make my first oven out of a 55 gallon steel drum. The footprint is small and can be heated by one element with minimal power consumption but I can still do car rims due to the circular space in the oven. Conventional house oven wouldn't work. I have attached some pics to show where I am at this point. Just got my PID and SSR in the mail yesterday. Planning on doing the final hookup in the garage and all the wiring next weekend. Having a little trouble with the PID as it didn't come with any instructions but I'm figuring it out. Might post up some questions later on. For now just wanted to say HI! and share what I have done so far.

I bought the drum from a farm supply store in town for $12. I used 2 inches of Johns Manville "spinglass" ceramic enhanced fiberglass insulation rated up to 1,000 degrees (ebay $50). Then I skinned the outside with 22 gauge steel from the home improvement store. Cut ben't and riveted into place over the insulation and secured around the rim. I installed the heating element in the bottom and built a cover with a 2 inch gap all around in the hopes that it would provide natural air circulation or convection and prevent any direct heating on the parts to avoid burning them. Opinions and suggestions are welcomed.

[Stubbie68]

Re: Newbie small oven build

Here are some pics of the element and cover.

[baz]

Re: Newbie small oven build

the oven will probably work but it does not seem very practical , loading from the top means that whenever you open the cover to check the temp you will lose most of the heat, also how will you hang or support a Wheel Inside the oven.
i don t have the exact measurment of the ID of a 55 gal drum but i think it is around 21 or 22 inches and i know that an 18 inch rim has about 19 inches OD that will leave you about an inch all around the Wheel when you lower it down flat , a very slight angle on the Wheel when going down will scrape the powder off the edge .

[Stubbie68]

Re: Newbie small oven build

I get what you are saying. And I appreciate it. The goal here was to keep the footprint as small as possible and still be able to do rims. It is possible that the drum that I bought is not typical as the inside dimeter is 23". As long as I am able to raise and lower the top following guides to keep it perfectly straight it should be fine. Given the oven's small size and mimimal wasted space (opposed to a square) it should heat up again somewhat rapidly even after it's opened and closed. Thanks for the input though. I knew going into this my design would be atypical and would have issues that I would have to overcome. If it works and I am able to get the job done and be consistent, once I make a little money I will upgrade and build something larger. Baby steps for now. Biggest obstacles are two fold; working on a budget and convincing the wife that this whole crazy idea is actually viable.
Cheers.

P.S. by the way, to your point baz. I was planning on using a cable system attached through the top of the oven to raise and lower the top with the piece attached to the top in the center via hooks. Rims would be kept flat by running a piece of pipe with something flat welded to the bottom and run up through the center bore hub hole. I've seen some support rims through the valve stem hole but that won't work for me.

[ed_denu]

Re: Newbie small oven build

Nothing wrong with thinking outside the norm. My one concern would be that with two rims, the bottom one would reach part metal temp much quicker than the top one.

[Stubbie68]

Re: Newbie small oven build

Haha, one at a time for now. Depth is only 31 inches so 29 unless I want to be bumping on the burner. It is obviously going to take a long time for me to do a set of rims, but, after I make a few bucks and the wife gets more comfortable with it I will be able to expand my opportunties and capabilities. Still have to build a sand blaster too.

[ed_denu]

Re: Newbie small oven build

My first blast cabinet was home made out of plywood. I still use it for plastic media and sometimes walnut shells. If you haven't already check this site:

Homemade Media Blasting Tools

[Stubbie68]

Re: Newbie small oven build

Ed, thanks a bunch for pointing me to that website.That site is awesome. So many great ideas.

[baz]

Re: Newbie small oven build

one of those steel funnels upside down with a eye hook at the small end would work well to hold the wheel and would fit different hub sizes.

[Stubbie68]

Re: Newbie small oven build

That's what i was thinking. It would be self centering also.

Just finished building the control box with the PID and SSR. Bit of a pain since it didn't come with instructions. I worked it out though. Got a friend from work thats an electrical engineer to test it. Works perfect. Doing all the connections to the oven and installing the outlet in the garage this weekend.

[Stubbie68]

Re: Newbie small oven build

Anyone with some insight into the wiring? Just want to make sure I wired it correctly. Powerpoint schematic is attached. The 220-240 service was pre existing in my garage for the electric car charger we had installed by an electrician. I tapped off of that to install the outlet. I am thinking I should change the breaker to a 30 amp just to be on the safe side. Recommendations?

[ed_denu]

Re: Newbie small oven build

I don't see that you ever stated what wattage the element you are using is rated at. You probably could have gotten by with a single 120 volt 1500 watt element versus going with a 240 volt feed. 1500 watts can adequately heat around 10-12 cu ft. However a 240 volt element would work fine. Your diagram indicates that the circuit you plan on using is a 2 wire with ground. This is fine for what you depict, but there is no neutral so that rules out using a light or fan which I don't believe you were considering.

You don't show a relay in your diagram, but wiring for a single element would not require 10 ga conductors. For a typical oven element around 3000 watts, 14 gauge would be adequate. High temp wire should be used for the last connection into the element.

You really aren't showing how you intend to wire the pid/ssr/elements in your diagram so it's not possible to comment on it being correct or not. What is the existing breaker size?

[Stubbie68]

Re: Newbie small oven build

Ed, thanks so much for the reply.
The element I got from an oven that was free on craigslist so I didn't have to purchase it. Also, the element type has the flange about 3 inches away from the end of the element or where the wire connects. The wire connections to the element are outside the oven and inside separate electrical boxes mounted to the outside of the oven. No heat on the wires to worry about. In other words, there is no wiring inside the oven chamber. The oven is very small with no windows so light or fan are not necessary at this time. When I make a bigger one then we will see. As far as the control box I do have a PID and SSR (40 AMP) and I am sure it's all wired correctly because I brought it to work and had an electrical engineer friend of mine hook it up and test it. I was mainly concerned with the wiring from the panel to the outlet. Just wanted to make sure that was correct. There is no on off switch so the oven will be unplugged when the car charger is in use and the car won't be charging when I am using the oven. The panel has a 40 amp breaker on that line and since the wire is 10 awg I was thinking I might need to change it to a 30 amp just to be safe. Do you concur or am I fine?

[Stubbie68]

Re: Newbie small oven build

one of those steel funnels upside down with a eye hook at the small end would work well to hold the wheel and would fit different hub sizes.

Baz, This is what I came up with to hold the rims in the oven. Good and solid and goes up through the center bore just like the funnel you were suggesting. Thanks for the idea.

[baz]

Re: Newbie small oven build

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Baz, This is what I came up with to hold the rims in the oven. Good and solid and goes up through the center bore just like the funnel you were suggesting. Thanks for the idea.

Nice, that should do the trick.