Pushing the Max

[IAMaxxer]

I run a 20 amp CC power source... With the 720 rule, at the extreme I would do would be aproxmintaly 480 sq inches. With that said I have a guy that wants me to do a tunnel extension on a snowmobile it is closer to 600 sq inches.
1St question is can I mask off the inside of this(it does not need to be anodized on the inside) and use only the out side surface area sq inches to calulate the 720 rule.
2nd question what do you use to cover the surface that will withstand the ano. bath..
3rd question How many of you push the max out of your power source to do a job?
Thanks Ross

[destroyer125]

I have heard of people making plastic plugs to mask off the inner bore...I usually hit a 20 amp load doing an enitre pb gun with a 35 amp power supply.....CV mode that is.....no problems so far

[acidrain]

Caswell makes a liquid mask that is just for this purpose. I haven't used it though.
Masking with vinyl tape should work as well, and be much cheaper.
I tend to take it easy, and try not to get too close to the max of my PS.

[cameraman]

Yes, you only have to count exposed surface area in your calculations, so masking off the inside removes it from the math.

I use Caswell's liquid mask; it works great.
As an experiment I tried electrical tape but wasn't surprised when I saw it floating around the ano tank. I also tried electrical tape and 'sealed' the edges with liquid mask - that worked. You could probably use some sort of packing tape and do the same, just paint around all the edges with the mask. Doing a large surface area with just the mask would work, but it would be irritating to do. The 'liquid' of the mask is mostly toluene so you have to balance well ventilated area with that fan's drying up all my mask stuff.