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-   -   Large volume hotbox (http://www.rcuniverse.com/forum/composites-fabrication-repair-97/11221804-large-volume-hotbox.html)

T_om 09-08-2012 09:06 AM

Large volume hotbox
 
If any of you guys have any experience with relatively large volume hot boxes, I would appreciate some advice.

The interior dimensions of the box need to be:

48" wide

36" high

18" Deep (front to back)

Exterior dimensions are unimportant, but the inside must be the above or a bit bigger.

The box needs to hold an even 180 degrees Fahrenheit.

Any suggestions as to materials, heating elements and controls?

Thanks.

Tom

soarrich 09-08-2012 09:46 AM

RE: Large volume hotbox
 
I made one once. I used 2" x 2' x 8' pink foam from HomeDepot just duck-taped together and a small space heater, but I had to shorted out the thermostat to get very hot. I think in the end I used a 1000 watt floodlight. Just stick a meat thermometer through the pink foam. You want a small fan to mix the air.

T_om 09-08-2012 10:48 AM

RE: Large volume hotbox
 
Thanks,

There are a LOT of posts about hot boxes, but the one sized as I want it has a large interior volume that has to be a bit hotter than the usual glass curing box. If anyone has any experience with larger boxes, I would appreciate any info.

Tom

soarrich 09-08-2012 11:30 AM

RE: Large volume hotbox
 
Tom
Mine was 6'x2'x2', the foam was 2" thick, so mine was bigger than what you're trying to make.

T_om 09-08-2012 11:32 AM

RE: Large volume hotbox
 
OK, but as I said, I need 180 deg. F, did yours do that? I don't see a floodlight in a big box holding 180 degrees.

Tom

soarrich 09-08-2012 12:13 PM

RE: Large volume hotbox
 
Tom
I think I did, (it was 5~6 years ago), with the small space heater, it was 1500 watts with a fan. I was drying HydroCal 30 molds, I needed ~140° for about a week and the space heater made me nervous, the lights held the temp I need.

wyowindworks 09-08-2012 01:17 PM

RE: Large volume hotbox
 
Extruded polystyrene insulation foam isn't very stable about 165*F.

I would frame the box just like you would a wall.  I would line the interior with fiber cement tile underlayment.  You should be able to get it from Home Depot or Lowes.  You can insulate it with regular house insulation.

I would heat it with a 120 volt baseboard heating unit.  You can get 30" ones for around $20.  You will will have to jump/disable the heat protection circuit breaker or put a breaker with a higher temp rating into the unit.  If you want to get to 180*F then you want to use at least a 200*F breaker.

You'll want to install a fan to the inside that can circulate the air to eliminate hot spots.  You will need a fan that uses bearings that can handle the higher temps.

You can control the heating unit with a Ranco controller.  These wire up very easily and already contain the relay and temp sensor.  There are other heat controllers out there on ebay but you will need to wire them up to a relay to turn the heating element on and off.

Adam

T_om 09-08-2012 01:35 PM

RE: Large volume hotbox
 
Thanks Adam, do you have a source on the controller?

Tom

wyowindworks 09-08-2012 01:39 PM

RE: Large volume hotbox
 

Quote:

ORIGINAL: T_om

Thanks Adam, do you have a source on the controller?

Tom
http://www.etcsupply.com/ranco-etc11...ller-p-86.html



T_om 09-08-2012 06:19 PM

RE: Large volume hotbox
 
Thanks Adam, I ordered one tonight. I used to have an old Johnson Controls unit but it is apparently lost forever... have no idea where it went.

Will be looking for a fan or fans that can take that heat now too.

Tom

XE521 09-13-2012 10:58 AM

RE: Large volume hotbox
 
Hi Tom,

just a thought on this subject, you could use a fan from a junked hot air oven.

Regards.

Karl.

T_om 09-13-2012 11:35 AM

RE: Large volume hotbox
 
Hello Karl,

Just for giggles I put in a 99 Cent bid on a used convection oven fan with free shipping on eBay... and won. :) My Ranco temperature controller came yesterday, I got it here as recommended by Adam: http://www.etcsupply.com/index.php

All I have to do now is build the box.

Tom

XE521 09-13-2012 02:13 PM

RE: Large volume hotbox
 
Hi Tom,

wish you all the best, just hope it turns up.

Here in Germany it appears to be the 'in thing' not to deliver if the price is too low. I've no idea what it's like in the States, but here it's too much hassle to sue the seller and evilBay are of no help.[:o]

Regards.

Karl.

P.S. I'm glad that this theme cropped up as I'm in need of a large hotbox.

SCALECRAFT 09-14-2012 07:29 AM

RE: Large volume hotbox
 
Just remember to use it outside. Fire hazard and vapors from cure not good.

Steve

T_om 09-14-2012 07:41 AM

RE: Large volume hotbox
 

Quote:

ORIGINAL: XE521

Hi Tom,

wish you all the best, just hope it turns up.

Here in Germany it appears to be the 'in thing' not to deliver if the price is too low. I've no idea what it's like in the States, but here it's too much hassle to sue the seller and evilBay are of no help.[:o]

Regards.

Karl.

P.S. I'm glad that this theme cropped up as I'm in need of a large hotbox.

Hello Karl,

The shipper was an honest one... I got the USPS shipping notification and Priority Mail tracking number yesterday.

He was the one listing ".99 Cent Opening Bid & Free Shipping" so I guess that he just took a chance it would go for more than minimum and lost. He has a bunch of sales and very good feedback too.

Tom

T_om 09-21-2012 06:24 AM

RE: Large volume hotbox
 

Quote:

ORIGINAL: wyowindworks

Extruded polystyrene insulation foam isn't very stable about 165*F.
Hello Adam,

I have all the necessary stuff now. For weight savings I am going to use this: [link]http://www.r*****c.com/downloads/DataSheets/rmp3.pdf[/link]

It is in-stock at Home Depot and is rated to 250 deg. F. Backing that with other rigid foam should be safe at 180 deg.

Tom


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