RE: Cutting a 40+ inch foam combat wing

RE: Cutting a 40+ inch foam combat wing
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RE: Cutting a 40+ inch foam combat wing - 6/27/2006 4:30:24 PM

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PT- Just to be clear:
Your first cores came out bad due to a Bow/Guide problem rather than a Dimmer/Wire problem. So the ACDimmer is still OK in your book?

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RE: Cutting a 40+ inch foam combat wing - 6/27/2006 4:40:14 PM

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My first cores came out bad due mainly to a bad Patrick if the truth be told. The dimmer works fine, but wouldn't do for a smaller bow. I've got about 3/16" throw from just right to glowing red and sometimes you gotta throw the power switch a couple of times to get the dimmer to pass current. I think that's because the dimmer is set so low.

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RE: Cutting a 40+ inch foam combat wing - 6/27/2006 10:57:19 PM

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A couple of pics of the foam cutter set up I just recieved from my Dad. It's a DC power supply he designed himself with a switch for a long or short bow. The long bow is 36" and uses special RENE wire. See http://www.alloywire.com/rene_41.html I can't wait to get some foam I've been collecting from the storage unit this weekend and try it out!

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RE: Cutting a 40+ inch foam combat wing - 6/27/2006 11:23:13 PM

vicman

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ooooooooohh, nnniicee. (insert Homer's voice

) That looks pretty cool. Way cleaner than the one you saw in my shop that day.

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RE: Cutting a 40+ inch foam combat wing - 6/28/2006 11:58:45 PM

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Thanks Vic! Yeah my Pop's a real Pro. He's got a fantastic shop in his basement that makes me drool just looking at it. I was cutting foam wing cores for pattern planes with him when I was a kid. He had a great set up back then where the bow was suspended from the ceiling and counter-weighted.

< Message edited by propbuster -- 6/29/2006 12:00:00 AM >

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RE: Cutting a 40+ inch foam combat wing - 6/29/2006 8:00:29 AM

vicman

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I hereby qualify as chopped liver.

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RE: Cutting a 40+ inch foam combat wing - 6/29/2006 1:30:15 PM

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Me too, Vic. Maybe I just need to send my templates to Prop.

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RE: Cutting a 40+ inch foam combat wing - 6/29/2006 2:33:09 PM

uliner

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quote:

ORIGINAL: KidEpoxy

funny how there are plenty of warnings against 120ac, but so few folks mention there is a 3' smokin hot length of wire that can blister ya right up. Comes right to it, I've been hit with 120 & 277 plenty of times (retrofited flourecent balasts while lights on in hi-rises), I hate a blistered burn more than a 120 jolt... but I went thu 3-4 lineman pliers a year from 277 arc divots.

I dont see how AC using a heavyguage, insulated wire right up to the filiment would be any more dangerous than having 48 of hot wire in the garage anyway. If you are the kind of guy that can swap out a lightswitch or outlet while hot, go for it.

Warning: The part that will burn you, is hazardous to touch because of electrical concerns

WOW I can't agree with this. As an EE I work arroung live power every day, and it is important to minimize your risk to shock. Using a 120 V line current is dangerous, and isolasolation transformer is cheap. For less than 15 bucks and 30 minutes, you can protect yourself. Why wouldn't you?

Radioshack part 273-1512 will do, it will get warm but it should be OK. It only takes 12-18 volts to heat the wire for cutting, but where is the ground? You still may have 120volts to ground. A transformer (not a audio transformer or a variac, they have no isolation) will isolate you from the line and your only risk will be burning yourself.

Dave

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RE: Cutting a 40+ inch foam combat wing - 6/29/2006 4:33:30 PM

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If I say I eat ramen noodles because 50cents for Mac& Cheese is too expensive (sure its 33, but the milk is where they get you with hidden costs)... If I let you in on just how poor I am and still trying to get planes in the air, does that put the cost of a xfomer in scale.

Why wouldn't I spend $15? Because I want to spend that $15 on something else.
I drive the car with the windows down in 95 temp days in town (under 50mph) cause I can save a buck on gas. Is it better with the AC on, sure it is, but I have priorities, and comfort is below cost.

If folks have the skill to work ac Hot, and it aint a 000 220 200Service drop, but some 120 already thru a dimmer down to foam wattage.... save the buck. Go for it. We are talking a possible shock, not an arc that will cook you. If you have the experience & equip to replace a breaker with the pannel hot, this bow is easy. I've already shown how to use a Serial Lightbulb & GroundNeutral(fault) could safe it up for those with AC concerns.

The part that will give you 3rd degree burns, may/maynot shock you

note- sure folks like to call it 240v, but I'm old and I say the two hots make 220, even though I see 115,120,125 lables on stuff.

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RE: Cutting a 40+ inch foam combat wing - 6/29/2006 5:12:13 PM

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The voltage on the cutting side of the dimmer is way down. CP said his was cutting at <8v? A transformer would offer the oportunity to get better resolution in temperature, but careful building of the bow keeps any risk of touching a "hot" wire at a minimum.

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RE: Cutting a 40+ inch foam combat wing - 6/29/2006 6:01:09 PM

uliner

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Kid,

I have no problem with you working with a hot (electrically) wire, you have assumed the risks.

It's a free counrty do what ever you want. It's no skin off my teeth, really I don't care.

Just don't minimize the risk to others, who may not understand the issues. Electricity is not well understood by many people.

It only takes about 100ma to stop your heart, and 30 inches of exposed conductor, is inviting trouble. The systems talked about could supply many times that.

If you are an electrician, you could probably scrounge a control transformer from an HVAC system, track lighting transfomer, or a takeout from a old copier or something, or a wrecked battery charger.

A $15 transformer, fuse and a dimmer can make the cutter that is safe, and spread over 10 years, that is almost 0 cost.

Dave

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RE: Cutting a 40+ inch foam combat wing - 6/29/2006 6:41:30 PM

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Well, I think we can agree that anyone uncertain of their eletrical skills should not engage in this kind of enterprise without serious study & maybe supervision/assistance.

quote:

From CP:
Ok, I just whipped out a wing panel, I measured the cutting voltage and it was 7.8 VAC. The voltage in the barn is 120 VAC.

isnt 7.8vac what a RC 6cell ESC puts out... upto 30amps of 7-8v (dc) ?

1. The electricity at the exposed parts of the system isn't 120v 20a, its (in this case) 8v.
2. Maybe we could just use the ESC and 6-8cell 30a nicads (chevy 12vbatt?), & use the TX as the heat dial

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RE: Cutting a 40+ inch foam combat wing - 6/29/2006 7:03:44 PM

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very interesting idea.. i can just see someone walk their E-powered plan over to the foam table and plug the cutting wire into the esc and ramp up the throttle and go..

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RE: Cutting a 40+ inch foam combat wing - 6/30/2006 1:48:47 AM

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I guess it's possible that a bird or a bat could fly into my shop while I'm cutting with the light dimmer and turn the dial up to full blast. Of course, the hot wire will explode before I have a chance to remove my bare feet from the tub of well grounded and salty water that I'm standing in. I could place a 120VAC hot at one end of a small fish tank and place the neutral at the other end, submersed in normal salinity tap water. Then, while ensuring that I'm not connected to a good ground path, stick my hand in the tank and not feel a thing. We did that trick one night in the third year of my wiremans' apprenticeship program. If you have a GFI source that you can tap into, it will save you in case a bat flies in to your shop and turns up the dial while you're cutting in your bare feet.

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RE: Cutting a 40+ inch foam combat wing - 6/30/2006 2:02:32 AM

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My friend looked at me weird when I got a 6foot FG ladder out to work on his chesthigh pannel from the first step. Better safe than sorry. If you got it, use it.

I used to get a lot of new guys with backfeed on the white.... they get a real healthy respect for it that way.

Might be good for some folks to use a loose blue Newwork 2Gang on a cut extension cord... wire up the dimmer & such, then plug in.

Maybe if we got a transfusion of Distilled Blood we dont have to worry about conducting to ground if we touch something

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RE: Cutting a 40+ inch foam combat wing - 6/30/2006 2:21:01 AM

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Comming from a construction background, I've been bit enough times to remember to not let my finger slide onto the metal part of the screwdriver. The worst electric shock I ever got was from a bathroom sink. I was up on the counter changing out a light fixture and forgot about the metal sink connected to metal pipes buried in the ground. Put my knee on the edge of the sink and peeled up some hide through my jeans. I still work on live stuff occasinally, but I'm more careful.

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