Digital Hotbox
Posted: Wed Oct 01, 2014 6:14 pm
Recently having moved from QLD to NSW, I've come to realise I'm going to need some kind of hotbox for curing glues & resin. In QLD the sun & ambient temperature just about cut it, here in NSW, particularly in winter, technology needs to step in where nature fails. I'm not going to say "I'm the first to do this" (as I'm sure there are plenty of others out there doing the same) but most hotboxes I've seen utilise the 100 watt bulb solution to raise the container temperature. This one uses a cheap $15 heater operating through a $35 ($50 inc. shipping - http://www.lightinthebox.com/max-30a-di ... om=sysmail) controller unit. The idea originally came from trying to pull a kitchen oven apart, then speaking with my electrically minded brother who set something similar up for his homebrew.
Additional items other than the heater & controller are the extension lead ($5, from memory), electrical lead hooks (for keeping the lead down - $2?), 4 caster wheels ($8 each but only because they had only 3 of the cheap ones), a few boxes of screws, some terminal blocks and a few short pieces of wire (which I already had).
The frame is standard shelving angle (I'm not going to lie, this wasn't cheap), providing 2.4m length by 600mm width by 600mm height. The walls are 7mm ply ($50ish a sheet where I am, cheaper in urban centres) with a layer of 15mm insultation board glued internally ($15ish a sheet, I think).
The ply lid has warped but that's an easy fix with some more support struts over the ends. I finished the wiring this weekend and it's functioning, albeit in an ugly & unsafe fashion. I need to get the controlling unit & wiring nicely tucked away in a box, rather than stuck to the side with tape...
Here's the unit in action -
Reading 20.8 deg. C, I've got it set for 50 deg. C so that it will turn off at that point, then turn back on at 45 deg. C (although these parameters are completely adjustable, within a fixed range).
Now, i know what you're all thinking - "Why would you build a hotbox that crazy big?". Well, I'll usually glue up a bow & laminate a glass lam at the same time, so I needed some extra width. The other dimensions just seemed to all slot together, so why not? It doesn't have to be this big but for someone who might be gluing multiple bows at once (Yeoman) it's about right, and you could probably even put an extra shelf in too. Plus, it gives me scope to move into some aeronautical & automotive projects I've been putting off.
In terms of construction cost, I think it is a bit more expensive than the electric bulb solution, but with a maximum 15 watt heater operating far more efficiently than 4 100 watt bulbs, savings will be made on electricity and general usage. The bulbs will have to be on a while to crank up heat, this fella controls himself. I also read rumours that the specific bulbs used are getting harder and harder to source, so in future this option may be something more available to most people.
Anyway, please excuse the shoddy build, but maybe it'll be a chance for me to get something completed and show you all what I can actually do...
Additional items other than the heater & controller are the extension lead ($5, from memory), electrical lead hooks (for keeping the lead down - $2?), 4 caster wheels ($8 each but only because they had only 3 of the cheap ones), a few boxes of screws, some terminal blocks and a few short pieces of wire (which I already had).
The frame is standard shelving angle (I'm not going to lie, this wasn't cheap), providing 2.4m length by 600mm width by 600mm height. The walls are 7mm ply ($50ish a sheet where I am, cheaper in urban centres) with a layer of 15mm insultation board glued internally ($15ish a sheet, I think).
The ply lid has warped but that's an easy fix with some more support struts over the ends. I finished the wiring this weekend and it's functioning, albeit in an ugly & unsafe fashion. I need to get the controlling unit & wiring nicely tucked away in a box, rather than stuck to the side with tape...
Here's the unit in action -
Reading 20.8 deg. C, I've got it set for 50 deg. C so that it will turn off at that point, then turn back on at 45 deg. C (although these parameters are completely adjustable, within a fixed range).
Now, i know what you're all thinking - "Why would you build a hotbox that crazy big?". Well, I'll usually glue up a bow & laminate a glass lam at the same time, so I needed some extra width. The other dimensions just seemed to all slot together, so why not? It doesn't have to be this big but for someone who might be gluing multiple bows at once (Yeoman) it's about right, and you could probably even put an extra shelf in too. Plus, it gives me scope to move into some aeronautical & automotive projects I've been putting off.
In terms of construction cost, I think it is a bit more expensive than the electric bulb solution, but with a maximum 15 watt heater operating far more efficiently than 4 100 watt bulbs, savings will be made on electricity and general usage. The bulbs will have to be on a while to crank up heat, this fella controls himself. I also read rumours that the specific bulbs used are getting harder and harder to source, so in future this option may be something more available to most people.
Anyway, please excuse the shoddy build, but maybe it'll be a chance for me to get something completed and show you all what I can actually do...