I´ve been building a DIY foam cutting power supply, it will soon be ready.
The next step will then be to build a bow for the hot-wire. Now, a friend of
mine gave me a coiled heating wire from a ceramic oven and I´m hoping I
could use this. Took me an evening to uncoil the stuff, managed to do it
with no nicks in the wire, but it´s a bit wavy still and just forming it
with my fingers or pulling on it won´t straighten it out. Any ideas on how I
could get it straight and smooth?
Cheers, Ken
The tension of the bow should be able pull the wire straight and
tight. Foam cutting wire is very thin, on the order of .020", or .5mm,
preferably stainless steel. I suspect that oven wire is probably quite
thick.
I built a DIY foam cutter last year.
I have used cheap picture hanging wire 22 gauge. It works ok, but it
stretches, and breaks easily.
The best wire I have used so far is .014 diameter stainless steel
fishing leader. I works great.
I have never tried Ni-chrome wire, I can't find it locally.
Any wire thats small, yet doesn't stretch much when heated will work.
On Tue, 12 Aug 2003 12:41:14 +0300, "Ken Mattsson"
More than likely, that is nichrome wire and really isn't the best stuff for
foam cutting. It stretches a lot and is hard to hold tension. The wire you
really want is Inconel. If you are using 20-40 volts, then wire near .015
diameter will work well.
Me thinks you are waisting your time. I use Tekoa's carbon wire it
costs $4.50 for an 8' length and lasts foreever if you don't miss
handle it. The wire is called T370 is used to make coil springs. It
doesn't streach like like ni-crome. I have a 54" bow that I use to cut
Q500 wings and the wire in it is about 6 years old and has cut about
50 wings.
So to me the bother of unwinding a coil is just not worth $4.50. Kind
of like making your own CA.
Tekoa is here
http://www.tekoa.com/catalog.html
And there's a distributor here.
http://www.acp-composites.com/ACP-CAT.HTM
http://www.acp-composites.com/acp-FoamCuttingEquipment.pdf
IMHO,
Stan D.
On Tue, 12 Aug 2003 12:41:14 +0300, "Ken Mattsson"
I built a very easy foam cutting bow that works great. I used a piece
of metal electrical conduit from the hardware store as a handle. I bent
it into a bow shape with a pipe bender. I stuck a piece of dowel into
each end, drilled through it and secured it with a screw. The thick
dowel sticks out of each end about an inch or so. I drilled through
both dowels and put bolts through them to attach the wire to. The bolts
have the type of heads that are flattened for turning with your
fingers. I drilled little holes in the heads and attached the wire,
which was stainless fishing leader. Then I wired it to a cord with
medium sized battery clamps on the ends. Whenever I want to use it, I
just attach it to a car battery.
It works great, and it cost well under ten dollars.
Ken,
If you find a place to buy fishing leader in lengths longer than 15cm here,
please let me know about it! I have had to bring it from the UK on visits
(to use as closed-loop wire).
How's that simulator you bought from me doing?
--
Dave S, Kuusankoski, Finland.
My return address requires modification before use.
Thank you guys for all the great advice I got! I´ll try to straighten out
the wire I have first, If I don´t succeed I´ll start shopping around for
other wire types.
here,
Dave,
It seems that most fishing shops in Finland have a somewhat restricted
sortiment. I´ve been looking for suitable fishing string (or do you call it
fishing line???) for a bungee launcher for sailplanes, but the shops mostly
only have quite thin string and even less of string in 100 meter reels or
more. By fishing leader, do you mean that first length of wire from the
lure, used to avoid getting the line cut off by too aggressive fish? =)) If
I run into this kind of wire sold by the meter, I´ll be sure to drop you a
line.
Oh, I learned to hover in different positions, with tail in and side in.
Then my studies and work took the best of me and haven´t played around with
it that much after this. Still, I´m very pleased with it and wouldn´t sell
it, not even if I could afford the Realflight G2. There is something very
cosy about the CSM v.10. Still haven´t found a Piccolo heli for the sim
though, that´s to be honest the real reason I eventually stopped using it.
The Piccolo is, I´m afraid to say, some kind of obsession to me, I will get
a real one before I die, even if I die trying to get one=)) Those little
helis just are so darned expensive and it seems that even if I try to talk
smoothly in German with the guys at Ikarus, they just don´t seem to get it,
that they need to give me a special deal in order to save the world and make
it a better place to live in;)
Still, in case there is any friendly Piccolo nut with a suitable setup for
the CSM sim reading this, I´d be very happy indeed if he/she would be
willing to send me the settings. Tried asking around for a CSM Piccolo in
heli groups once, but nobody had done it and I cant since I have no idear of
how the Piccolo should act to get it right. As a parentesis I have to say
that for owners of real Piccolos there are some VERY nice web sites out
there, very fine sites indeed.
Oh well, ´nough said about helis. It´s been great fun building this foam
cutter power, and again a big thanks to the kind soul who put out the
building description on the net for all and everyone to enjoy. It´s great
fun building one´s own tools.
Cheers, Ken
Finland
visits
it
mostly
If
with
get
it,
make
of
Fishing leader, or trace line as it seems to be called in the UK, is indeed
the thin metal line (usually with a nylon coating) that is used to defeat
the teeth of the pike. In the UK it can be bought on reels, but I have seen
it only in short lengths here.
For really thick nylon monofilament, try Kärkkäinen; not the model dept, but
the fishing section. I saw some line about 2mm thick when I was there a few
weeks ago. Last summer I was towing up a 3½ metre glider with some line I
got from Prisma! Nordic sports in Kouvola also have some decent line.
My heli addiction has finally been cured, only two left now and both for
sale. My only experience with a micro heli was a friends Hornet - about 100
times harder to fly than a glow heli! I saw a guy with a 'made in Finland'
micro heli a few weeks ago - he flew it IN the SIL shop! I was told there
are plans to go into production. At least then you could order your spares
in Finnish!
--
Dave S, Kuusankoski, Finland.
My return address requires modification before use.
Dave,
I can get Inconel fairly inexpensive ($1.75/foot in small quantities) and I
have a fair amount right now at about half that cost. Inconel is a lot
better than stainless. It takes less power to heat and doesn't stretch as
much.
Send me a few Euros and I'll set you up with about 10 feet of it.
tie a 3 kg rock to your head and jump up and down on the spot for ten
minutes. That should give you a headache about as quickly as trying to
straigten out wire, Ha, ha. ;b
I must admit, this suggestion seems the best to me:
Me thinks you are waisting your time. I use Tekoa's carbon wire it
costs $4.50 for an 8' length and lasts foreever if you don't miss
handle it. The wire is called T370 is used to make coil springs. It
doesn't streach like like ni-crome. I have a 54" bow that I use to cut
Q500 wings and the wire in it is about 6 years old and has cut about
50 wings.
So to me the bother of unwinding a coil is just not worth $4.50. Kind
of like making your own CA.
Tekoa is here
http://www.tekoa.com/catalog.html
And there's a distributor here.
http://www.acp-composites.com/ACP-CAT.HTM
http://www.acp-composites.com/acp-F...ngEquipment.pdf
IMHO,
Stan D.
--
Randori
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I finished the DIY foam power supply recently and tried it out with 48" and
24" long wire from the ceramic oven. Well, it didn´t work out that well.
This wire is 0.5 mm in diameter and while the power supply is designed to
work with the above mentioned lengths of wire, I had to use it with the
switch turned to the 48" length position with the 24" long wire to get even
e very low intensity reddish glow. Seems pretty clear I need a thinner and
more easily heated wire. So, what would be a better pick, inconel 0.015 or
that other stuff, carbon wire which they sell at the feathercut site?
By the way, here is a link to the DIY power supply I built:
http://nsrca.org/technical/tip_tricks/foam_cutter/foam_cutting_power_supply.htm
I haven´t yet started building the bows, thought I´d surf the net a bit
first to see what sorts of bows can be built. Something that could be easily
taken apart and set up again would be nice.
Ken
From the land of the...well, very very many...lakes.
A dull reddish glow is WAY too hot for foam cutting! My wires do not glow
at all and cut as fast as my macine travels. You should try tocut some foam
before changing anything.
You will also find that Inconel takes a lot less power to cut foam.
The wire shouldn't get red hot. The wire only needs to be hot enough
to slowly melt its way thru the foam.
If the wire is too hot you'll melt a 1/4" gap thru the foam instead of
a gap the thickness of the wire.
The bow needs to be made from wood or either use insulators to connect
the wire to the bow. You don't want electricity traveling thru the bow
trying to heat the bow instead of the wire.
If you use metal templates to shape of the foam, be sure there is no
electrial path between the templates.
I once tried using 2 aluminum rulers clamped around a block of foam to
square cut the end. I was using a metal clamp to secure the metal
rulers. The electricity traveled from the wire to the ruler, thru the
clamp, to the other ruler, back to the wire on the other side. The
wire on both sides was hot, the wire in between the rulers was cold
and would not cut.
You already have your Power Supply, but the one I use is a $12 Radio
Shack 2.5 Amp 120VAC-input 25VAC-output Transformer connected to a $3
rotary-dial dimmer switch. It provides an infinitly adjustable heat
range for any length bow and any type foam, white, pink, blue.
The dimmer switch controls the input voltage, with directly controls
the output voltage(heat).
On Mon, 18 Aug 2003 16:34:55 +0300, "Ken Mattsson"
Ken, what do you plan to cover the foam cores with? I ask as I have had some
problems with veneered foam wings since I moved here, in that the veneer has
split due to the very low humidity here. I never had that problem when I
lived in England!
--
Dave S, Kuusankoski, Finland.
My return address requires modification before use.
some
has
Well Dave, having been to England a couple of times and always encountered
rain, I can see your problem! =))
Still, the same happens to me wherever I go here in Finland, been called the
rainman by my local friends...
As to what material to use for covering the cores, I must say I´m a newbie
to this subject too. Still, I believe most guys over here use balsa sheets
for this, mainly because it´s easily available. You can get thin plywood
too, from the model shops, but as to the suitability of this for sheeting
foam cores, I´m not that well informed. You might want to post your question
to this group: sfnet.harrastus.pienoismallit or sfnet.harrastus.ilmailu. You
can probably post in English if you like, the guys in the groups are mostly
good at English. I have always received good advice there, still I like to
use these international newsgroups too just because one can reach so much
more fellow enthusiasts this way.
By the way, I was kind of hoping I could get away WITHOUT sheeting the cores
for the basic trainer wings I´m contemplating, but maybe that would make the
wings too weak...? Still, there´s no sheeting on the Sturdybirdy II or
Duraplane wings, the former is strengthened by applying strips of glassfiber
reinforced tape (from your favourite "rautakauppa" over here) over and under
it, lengthwise, the latter has a metal U-channel in it (I think). I have a
Sturdybirdy and the tape trick seems to work, doesn´t even look too bad when
covered with a suitable iron-on covering film.
Hope this helps, if not, just post your question in the above mentioned
Finnish newsgroups, you will surely be helped. If that doesn´t work, drop me
a line and I´ll translate your question into Finnish for you.
Ok, have to run now to get the necessary stuff for a cutting bow!
Cheers, Ken
Sipoo
Finland
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