| Author | Message | ||
| john marbury (Jmarbury) (65.100.118.17)
Rating: N/A |
I need to make a "hot wire" to trim the foam insulation. Does anyone know what I need to do this? What kind of wire? what to use to hold the wire? hot to attach wire to handle? etc. John | ||
| Gary Stadler (Boogiethecat) (68.7.217.217)
Rating: N/A |
John, You can do it with a piece of nichrome wire taken from a heating element of some type. I get 220 volt "dryer restringing kits" from Johnstone supply (a national supplier of HVAC parts). In the kit is a length of heavy nichrome wire that is measured out to draw a few kilowatts at 220 volts. You measure the overall length as it comes from the factory, cut it to the much shorter length you want, and then calculate the ratio of the two lengths, multiply the result times 220 and now you have the aproximate the voltage you need to give to your shorter piece to make it work. Mine usually ends up wanting about 40 volts. It's fairly easy to make the handle using wooden dowels with attached aluminum pieces at the ends to hold the wire and make the connections...hose clamps to the rescue... The big problem is how to energize the wire. Technically you need a low voltage at a fairly high current (usually around 5-10 amps) for a few reasons: (1) Your wire should be thick so it's somewhat strong under tension, meaning that to get it almost red it will take a higher current than would a thinner wire gauge (2) The entire tool needs to be transformer isolated from the power line for safety. You don't want a hand held tool with either end of it hooked directly to 120 volts... it'd be tough to hold, dangerous to work with, impossible to set down without making sparks or getting shocked, not to mention shorting to the bus frame every time you hit it. BIG safety issues here... Finding a transformer that puts out the required current at the proper voltage might prove tough... (3) You need some sort of variable control method to control temperature. Sometimes you can get away with a simple household dimmer but most of the time dimmers don't like running into big transformers, so a large variac is the only way to do it. Expensive and hard to find (4) Last, if it's 2 part spray-on foam (or even one part expanding type) that you're thinking of trimming, before you go thru the hassle of making a wire cutter, heat up a piece of metal (like the blade of an old kitchen knife or something) with a torch and try running it thru your foam. Most likely you'll find that it makes some pretty nasty and otherwise toxic stink, and you, like I did, will quickly rethink your wish to use a hotwire. ......... I have all the stuff to make hotwires. When I did my bus, I gave up on that idea almost immediately. I ended up making a neat 3' long side-cutting bow-saw out of a piece of U- bent 1" square steel tubing, with a chunk of bandsaw blade stretched across the ends and welded. Came out looking kinda like a bow-and-arrow thing. That silly saw did 90% of my trimming, and it did it quickly and easily. It was long enough that I could hold it across two bus ribs and cut the foam inbetween, and the ribs guided it so the cut was flat with the ribs. Simple! For the rest of it where I couldn't get into the proper angles, I simply punched three holes in a grinder blade and bolted in three 1/4-20 bolts. This thing is messy but it is AMAZINGLY fast and makes very clean cuts. Here's a photo http://www.heartmagic.com/FoamGrinderTool.JPG Have fun. Get the wife to vacuum it all up when you're done looking like a snowman! Gary | ||
| Stan (216.95.238.81) Rating: N/A |
Without making any comment on the pros and cons of hot wire cutting spayed in foam, I made commercial cutters for expanded styrene (styrofoam) a lot of years ago. After a lot of design time with rejected power supply ideas I used an ordinary variable transformer AC welder. The common, cheap Millers and Lincolns worked fine. They have lots of adjustment and could handle cut wires 10 feet long or two feet long. I had two busses spray foamed and in both cases I let the contractor do the trimming. They used an air turbine driven helical knife that took about two or three hours to do the whole bus. | ||
| Jay Gerlick (152.163.252.163)
Rating: N/A |
OK this may seem real rinky dink, but We took a old fashsioned cross cut saw and mounted it to an old craftsman hedge trimmer. Took a few tries and Ny-loc nuts to hold it on but it worked great. We did the whole floor in our MCI 9 with spray foam. Just about ready to do the walls. The old Craftsman hedge trimmers held out great so far. I think I could dig up a picture or two???? | ||
| two dogs (67.30.23.65) Rating: N/A |
sounds like one of them turkey carvin' knives might work,don't know the correct name,one blade goes in & the other blade goes out... | ||
| Richard Bowyer (Drivingmisslazy) (24.196.191.70)
Rating: N/A |
Doggie, properly called an Electric Carving Knife FYI. Richard | ||
| Phil Dumpster (12.230.214.167) Rating: N/A |
A loop of metal coat hanger wire (the uncoated kind, pardon the pun) installed onto a Weller-type soldering gun in place of the normal tip works great for cutting and trimming foam. | ||
| jim mci-9 (209.240.198.60) Rating: N/A |
use the transformer off of a model train set..... works good.... | ||
| john marbury (Jmarbury) (65.100.118.17)
Rating: N/A |
thanks for the replies. You guys come up with great ideas. I often think "why didn't I think of that". I think I like the band saw blade idea best for what I need to do. John | ||
| R.C.Bishop (128.123.221.183)
Rating: N/A |
The wire coathanger sounds like a clean, simple and very practical approach. Other ideas good, but seem to me to be cumbersome in many respects. The wire can be reformed for corners, curves, etc. Great idea! Thanx for the tip, Phil  RCB '64 Crown HWC | ||
| Gary Stadler (Boogiethecat) (68.7.217.217)
Rating: N/A |
But RC, have you ever tried hot-wire cutting the sprayed stuff? It's NASTY. Hot wires work great on stryofoam but on the urethanes (at least mine) they make a LOT of yucky toxic fumes... I tried it for about two seconds and realized that if I wanted to actually be around to drive my bus someday, that wasn't a good idea for my health! Batteries not included... Gary | ||
| R.C.Bishop (128.123.221.223)
Rating: N/A |
Haven't tried it Gary, but I can imagine with a control of heat, as the Weller has, and as a train transformer would have, it would work under almost any circumstance....I understand that is the way foam "rubber"...as in pads, mattresses, etc... are cut. Have never done it but it's what I've been told by a place that sells the pads. FWIW RCB '64 Crown HWC | ||
| Gary McFarland (Gearheadgary) (198.88.152.22)
Rating: N/A |
Actually, the Foam houses that we've been to, had a way cool horizontal bandsaw, over a highly polished table, they just set the height of the bandsaw, and bush the foam "Block" through. Gary (The other one) | ||
| mel 4104 (208.181.100.53) Rating: N/A |
as posted yoy might want to check out if you realy want to cut the foam with a hot wire as the fumes are VERY toxic as the wire will be burning it way through the foam. the cost of a good suit and mask are very high and with out them it is very bad for your health. the fumes from ths heat cut foam remains on both sides of the cut this means that the peice you are keeping will retain fumes that leak out over a long time. a simple test is get a tin can and put a piece of foam in the can and lite it on fire, use a small piece,once the flame has go out wait for a few minutes as the smell the cam. if after this check your life insurance policy. but then again it is your choice. mel 4104 | ||
| Gary McFarland (Gearheadgary) (198.88.152.22)
Rating: N/A |
I just spent a day and a half researching the dangers of using Styrofoam, and I have some comments on Mel's Post. First, as to the toxicity of styrofoam, what is your data source? In my reasearch, vapors emitted from burned styrofoam were less tocxic than vapors emitted by burning Flour....Hey, that's what the documentation said. I talked with my son-in-law about this, he is a assistant cheif of a fire department. There are many substances they check for when entering a burning structure. Styrofoam is WAY way down on the list. He said "It's no more toxic than other commom building materials". Funny, that's almost word-for-word what the Data sheet said. It's all a moot point though, when you are hot-wiring styrofoam, it's it not on fire. No deadly vapors. Burning plastic smell, yes, deadly vapors no. There is no ignition source, like there is when you stuff it in a can and light it off. All of this is based on Styrofoam, if you are talking about urethane or some other foam product, um.....never mind. Gary | ||
| mel4104 (208.181.100.14) Rating: N/A |
gary i may have it wrong as my info was for the hot two part spray foam that people spray on the wall of their buses, as on the drums that it comes up here it states very clearly even when spraying the you must use proper safty eq. as i stated take a piece of spray foam and lite it on fire and take a whif of it to see what it is like then you will know. mel 4104 | ||
| Gary McFarland (Gearheadgary) (198.88.152.20)
Rating: N/A |
No no no no. You are right! I was talking about styrofoam, the white stuff. What you're talking about is Urethane foam, I think. All the posts just said "foam Insulation" I think I am going with Styrofoam, and I'll use the aerosol can stuff for the cracks. Someone correct me if I'm wrong, but you don't use a hotwire for the spray in stuff, but a sharp knife. I believe it cuts real easy. (Not so, the aerosol can stuff, however). Have you seen the professional system stuff? Where do you buy it and How much$$? Gary |