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Where did all the kits go?

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mcmike@insightbb.com - 21 Oct 2005 01:43 GMT
Just decided to get back into r/c after a layoff of some time.  Wanted
to build something, but the only thing out there anymore are ARF's!
Whatever happened to the kit builders?

Twangmaster
Geoff Sanders - 21 Oct 2005 02:13 GMT
Read the magazines, buy a plan, and contact one of the several kit
cutters!  That's how you get a kit nowadays!  :-)

>Just decided to get back into r/c after a layoff of some time.  Wanted
>to build something, but the only thing out there anymore are ARF's!
>Whatever happened to the kit builders?
>
>Twangmaster
>  
Fubar of The HillPeople - 21 Oct 2005 02:18 GMT
We went underground...
ARFs, man! They are everywhere, man! You cant hide!

Tower Hobbies still carries a few but the numbers are shrinking daily.
Bruce Thorpe Engineering (BTEModels.com) has a few good ones. I have the
Venture kit waiting to be built.
Myself, I haunt Ebay...

Signature

Dan
AMA605992
KE6ERB
http://www.fubar1.net
"I've heard the screams of the vegetables..."
Take out the "trash" to reply

> Just decided to get back into r/c after a layoff of some time.  Wanted
> to build something, but the only thing out there anymore are ARF's!
> Whatever happened to the kit builders?
>
> Twangmaster
indoruwet - 21 Oct 2005 03:09 GMT
The market sells what the market will bear and what the customer wants.

Guess where you and I and a few of us belong ..... ?

Out of shear frustation, I look at arf's, dl the plans or manuals, the
draw the plans myself and kit the bugger.  You'd be surprised ho
accurate some of those manuals are.
Just finished a Giles 20

--
indoruwe
Ed Cregger - 21 Oct 2005 05:08 GMT
> The market sells what the market will bear and what the customer wants.
>
[quoted text clipped - 4 lines]
> accurate some of those manuals are.
> Just finished a Giles 202

And sometimes marketing folks project their own feelings forward and make
erroneous decisions.

Once the kit builders learn that the present ARFs aren't as they seem, they
might move back toward kit building again - assuming that ARF quality does
not seriously improve.

Ask one of my friends. He was flying his brand new ARF trainer after a lay
off when the right wing panel crumpled up in flight. Closer inspection
revealed that the wing had been jig assembled and then wrapped with
covering. Not enough glue. When the covering sagged a bit, the wing
disassembled - in flight.

New OS .46AX and flight pack were trashed. Importer of the POS offers to
replace the kit. What about the engine and flight pack? Nope.

Is saving a little time worth trashing all of your flight equipment?

Ed Cregger
Paul McIntosh - 21 Oct 2005 08:16 GMT
I won't buy any ARF from that big retailer just for that reason.  Had one
come apart and found missing pieces, broken pieces, no glue, etc.  Retailer
had the gall to threaten me when I reported it on here!

Signature

Paul McIntosh
RC-Bearings.com
"when steel just isn't enough"

>
>> The market sells what the market will bear and what the customer wants.
[quoted text clipped - 25 lines]
>
> Ed Cregger
Six_O'Clock_High - 24 Oct 2005 06:08 GMT
>> The market sells what the market will bear and what the customer wants.
>>
[quoted text clipped - 24 lines]
>
> Ed Cregger

Ed,
I am not sure you are as right as we both wish you were.  Let me share with
you some comments about discontinued kits I got from Midwest a couple of
years ago when I was discussing modifications that needed to be made in the
construction manual to make the aircraft a safer model.

The guy I was talking to (on my dime) told me that they sold out of that kit
and it would not be offered again.  I asked why and what he told me is still
rocking my thought processes.  He said that the rate of return on the
investment for that kit was too low.  I did question him in general because
the exact numbers were company close held information and he did answer me
in general terms.  It seems that his company invested $X to kit said
airplane.  It cost $Y to keep the completed kits on the shelf.  When
$X+$Y+Profit could not be recovered within an acceptable period of time,
that aircraft kit was discontinued.  I asked what controlled the process and
he replied 'sales rate'.

In short I am afraid that because many are no longer building kits, they may
no longer be available in the near future.  I wish I knew a way to change
that..without making a small fortune in the R/C world.  Small fortunes are
made in the R/C world from big fortunes...
Ed Cregger - 24 Oct 2005 06:56 GMT
>>> The market sells what the market will bear and what the customer wants.
>>>
[quoted text clipped - 46 lines]
> change that..without making a small fortune in the R/C world.  Small
> fortunes are made in the R/C world from big fortunes...

I hear you, Jim. Have you ever noticed how most small businesses have a
lifetime, just like we humans?

Midwest was near the top of the heap for a while, then it grew old and faded
into the background. Just like RCM and legions of other hobby related
businesses.

I understand that no one would be expected to keep producing a product that
was not providing sufficient income to justify its existence. After all, the
bottom line is profit,
as you have pointed out so well.

However, what if the kits begin to trickle in from China? Imagine the low
cost and good quality of said kits. It would not surprise me if I learned
that some enterprising Chinese entrepreneur has been buying up plans and
designs of past favorites. What is not profitable at Midwest, may be very
profitable in a Chinese manufacturing environment.

Chinese motorcycles are about to collapse the previously Japanese dominated
market paradigm. Some of the Chinese motorcycles are part-for-part clones
(Lijan 250cc V-twin of the Yamaha Virago 250cc V-twin) of Japanese
motorcycles. The feedback that I have heard so far have been very positive.

We in the US should begin investigating how England survived, more or less
intact, its removal from manufacturing dominance a couple of centuries ago.
I do not see the trend turning around for us any time soon. By the time it
does, the jobs will have moved from the poor folks in South Africa
(previously in Bangladesh) to the poor folks in North America. Fortunately,
I won't be here to see it. Neither will you.

Ed Cregger
Paul McIntosh - 21 Oct 2005 03:38 GMT
Did you even look for kits?  Virtually every online hobby shop has them.
Sig, Balsa USA and Tower all list many kits.  What are you looking for?
Most likely someone here knows where to get it.

Signature

Paul McIntosh
RC-Bearings.com
"when steel just isn't enough"

> Just decided to get back into r/c after a layoff of some time.  Wanted
> to build something, but the only thing out there anymore are ARF's!
> Whatever happened to the kit builders?
>
> Twangmaster
Ken Day - 21 Oct 2005 05:17 GMT
>Just decided to get back into r/c after a layoff of some time.  Wanted
>to build something, but the only thing out there anymore are ARF's!
>Whatever happened to the kit builders?
>
>Twangmaster
Where ? There's lots of kits out there. Top Flite , Goldberg , Sig ,
Great Planes , Herr Engineering , Hangar Hobby and on and on.
Just gotta look.

Ken Day
Preston S Justis - 21 Oct 2005 13:38 GMT
> Just decided to get back into r/c after a layoff of some time.  Wanted
> to build something, but the only thing out there anymore are ARF's!
> Whatever happened to the kit builders?
>
> Twangmaster

I noticed that as well after a 25 year layoff :^). Kits are still being
made, what are you interested in building? Sometimes you can find a kit that
is no longer produced on ebay or in some of the RC forums like RC Universe.

I used an ARF to relearn my flying skills (Avistar) and I was surprised at
how well the plane flew. I still have it too. I have to admit, there are
some pretty nice ARF's out there now. I'm actually thinking about buying
another :^()

I will always enjoy building. It's nice to have something unique to fly at
the club field...you won't ever get it mixed up with another plane in the
pattern!

Scott
indoruwet - 21 Oct 2005 14:38 GMT
Giles 202 follow up.
Waiting for parts of engine before I can maiden :( , but after that
the drawings will be updated.  I usually do some minor modding durin
the build-up. ;)
Anybody interested in the plans, let me know what format you can us
(DWG, DXF, PDF) or I can change to Kinko format and you can have i
printed yourself.
Actually a lot of work, cutting and sanding all those parts, but if yo
like to scratch built, then this is the way to go.  Takes me about tw
months for one plane.  I am not sure of the cost comparison, but I hav
a lot of wood and "stuff" laying around. :

--
indoruwe
Martin X. Moleski, SJ - 21 Oct 2005 17:11 GMT
>Giles 202 follow up.
>Waiting for parts of engine before I can maiden :( , but after that,
[quoted text clipped - 7 lines]
>months for one plane.  I am not sure of the cost comparison, but I have
>a lot of wood and "stuff" laying around. :D

I'd love to see a .pdf, not because I want to build the Giles but
because I'm interested in seeing your building techniques.

Thanks!

                Marty
                moleski@canisius.edu
indoruwet - 22 Oct 2005 03:45 GMT
Martin X. Moleski, SJ Wrote:
> I'd love to see a .pdf

You've got it.  As soon as I have updated the dwg, I will make a PD
for you.  Give me a few weeks

--
indoruwe
quietguy - 22 Oct 2005 09:11 GMT
Hi There

Building a power panel, and I need to know the current drawn by a (typical)
glow plug - I couldn't measure it as my set up included long thin leads to
my meter which dropped the voltage a lot - plug didn't glow!

Seemed likely to be around 1.5 to 2.0 amps using a single rechargable (Ncd
I think), but I would like a better figure if known

BTW I note that some power panels supply a pulsed? drive to the glow plug -
I am not sure why, and whether that method has benefits - but I was not
planning to get all fancy - just 1.5v dc from a voltage regulator etc

Cheers

David
Doug McLaren - 22 Oct 2005 16:44 GMT
| Building a power panel, and I need to know the current drawn by a (typical)
| glow plug - I couldn't measure it as my set up included long thin leads to
| my meter which dropped the voltage a lot - plug didn't glow!

Should be easy enough to work around ...

| Seemed likely to be around 1.5 to 2.0 amps using a single rechargable (Ncd
| I think), but I would like a better figure if known

I think that's about right.  But I haven't measured it.

| BTW I note that some power panels supply a pulsed? drive to the glow plug -
| I am not sure why, and whether that method has benefits - but I was not
| planning to get all fancy - just 1.5v dc from a voltage regulator etc

I can explain the pulsed power easily enough.

Ok, you've got a 12v input and need 1.2 volts out at 2 amps.  Sure,
you can use a voltage regulator, but it'll need to dissapate over 20
watts of power ((12 - 1.2) * 2), which is probably enough to require a
big heat sink and a fan, which increases complexitiy and cost.  That,
and you're draining your battery 10x as fast as you need to.

So instead, you just pulse the power, giving a duty cycle of around
10%, and the plug glows just the same, but you don't waste all that
power.

Signature

Doug McLaren, dougmc@frenzy.com
Operator! Give me the number for 911! --Homer Simpson

quietguy - 23 Oct 2005 00:31 GMT
Thanks Doug - I wondered it had more to do with what the plug needed/could use
rather than power dissipation - I will using a SM circuit so no sweat

David

> | Building a power panel, and I need to know the current drawn by a (typical)
> | glow plug - I couldn't measure it as my set up included long thin leads to
[quoted text clipped - 26 lines]
> Doug McLaren, dougmc@frenzy.com
> Operator! Give me the number for 911! --Homer Simpson
Branko - 23 Oct 2005 01:00 GMT
> Seemed likely to be around 1.5 to 2.0 amps using a single rechargable (Ncd
> I think), but I would like a better figure if known

I measured it when I designed my glow driver (pulsed BTW).  This is what I
wrote in my notes:
"My power supply can support a glow plug at 1.42V drawing 2.67A, this works
out to 3.8W and 0.5 Ohm."

Hope this helps.
Signature

Branko

quietguy - 23 Oct 2005 22:20 GMT
Thanks mate - very helpful as I was trying to get a good idea of max current
the supply needed to be able to put out

David

> > Seemed likely to be around 1.5 to 2.0 amps using a single rechargable (Ncd
> > I think), but I would like a better figure if known
[quoted text clipped - 7 lines]
> --
> Branko
Poxy - 24 Oct 2005 00:19 GMT
>> Seemed likely to be around 1.5 to 2.0 amps using a single
>> rechargable (Ncd I think), but I would like a better figure if known
[quoted text clipped - 3 lines]
> "My power supply can support a glow plug at 1.42V drawing 2.67A, this
> works out to 3.8W and 0.5 Ohm."

I've been thinking about making up a glow driver circuit - I like the idea
of a constant voltage supply, since it would behave like a NiCad driver - it
will increase the current if the plug is flooded to help burn off the fuel.
Also, an ammeter connected to the supply would give a lot of information
about the state of the plug.

However, compared to a simple pulsed 12v supply, a constant-voltage drive is
considerably more complex, requiring a DC-DC converter and reference
voltage, and will generate considerable EMF which might disturb nearby
radios, not the best thing at a flying field really.

What have others done? Would constant voltage be worth the effort?
Doug McLaren - 24 Oct 2005 16:27 GMT
| What have others done? Would constant voltage be worth the effort?

Personally, I don't even think a power panel is worth the effort.

My glow plug driver has a subC cell in it.  My electric starter has a
battery too.  I use a hand powered fuel pump.  No power panel.

I can see where only one battery to charge would be convenient, but I
don't like the wires -- just something else to get snagged in the
prop.

Signature

Doug McLaren, dougmc@frenzy.com
Blessed are they that run around in circles, for they shall be known
as wheels.

Poxy - 25 Oct 2005 00:18 GMT
>> What have others done? Would constant voltage be worth the effort?
>
[quoted text clipped - 6 lines]
> don't like the wires -- just something else to get snagged in the
> prop.

I use a nicad starter normally, but there are 2 situations where it'd be
useful to have a 12v-driven one on hand - for when the nicad starter is flat
(which seems to happen far too often), and for when you want to diagnose a
plug problem without removing the plug. Because the drive voltage is
accurately regulated, any change in the plug would be reflected by a change
in current draw. For example, a dead plug draws no current, a flooded one
draws excessive current, a worn-out one would use less current.
Doug McLaren - 25 Oct 2005 00:46 GMT
| > I can see where only one battery to charge would be convenient,
| > but I don't like the wires -- just something else to get snagged
| > in the prop.

Of course, the #1 thing to get snagged in a prop is my fingers/hand,
but I digress :)

| I use a nicad starter normally, but there are 2 situations where
| it'd be useful to have a 12v-driven one on hand - for when the nicad
| starter is flat (which seems to happen far too often)

I keep more than one on hand, which pretty much solves that problem.

| and for when you want to diagnose a plug problem without removing
| the plug. Because the drive voltage is accurately regulated,

I'm not so sure it's the voltage, but the duty cycle that's regulated.

| any change in the plug would be reflected by a change in current
| draw. For example, a dead plug draws no current, a flooded one draws
| excessive current, a worn-out one would use less current.

A worn out one uses the same current.  It's not the coil that wears
out, it's the catalyst coating that gets fouled.

Not sure about a flooded one, but I'll take your word for it.

Personally, my favorite nicad starter has a current meter built in.
The battery has already worn out once, but it wasn't hard to solder in
a new one.

Signature

Doug McLaren, dougmc@frenzy.com                   On my signal - unleash Hell!

Poxy - 25 Oct 2005 04:25 GMT
>>> I can see where only one battery to charge would be convenient,
>>> but I don't like the wires -- just something else to get snagged
[quoted text clipped - 8 lines]
>
> I keep more than one on hand, which pretty much solves that problem.

I have 2, a new one with a meter in the top, which is nice but my engine is
inverted so I can't see it, and one which is about 15 years old and seems to
hold its charge better than the new one. That said, I've managed to succeed
in having both flat  a number of times.

>> and for when you want to diagnose a plug problem without removing
>> the plug. Because the drive voltage is accurately regulated,
>
> I'm not so sure it's the voltage, but the duty cycle that's regulated.

Broadly speaking there are 2 kinds of electronic glow driver, the most
common is pulsed 12v where, as you suggest, the amount of current through
the plug is governed by the duty cycle of the pulses. However, these are
rarely regulated - that is, there is no feedback from the plug that varies
the duty cycle. Rather you set a fixed rate.

The other type of driver is what I'm considering. It's a little more
sophistcated in that it uses a DC-DC converter to produce a fixed voltage
which youy can set, say 1.25v. Using its own accurate voltage reference, it
monitors the output voltage and has a feedback loop that varies the duty
cycle of the converter to maintain that voltage. Thus, let's say a plug
driven at 1.25V draws 2.5A when it's glowing, however, if it beomes flooded,
the metal will cool, decreasing its resistance. In an unregulated circuit,
this would cause the voltage to drop as the load has increased, however with
this circuit, the DC-DC converter will wind upthe duty cycle to maintain
1.25V and the current rises to, say, 4A while the fuel is boiled off, then
as soon as the fuel is gone and the plug is glowing again, the circuit drops
the duty cycle.

The latter kind is in some ways similar to a simple pulsed 12V supply, but
where the pulsed units operate at about 100Hz, DC-DC converters tend to
operate in the 100KHz or higher range - some as high as 1MHz leading to
issues of RF radiation

>> any change in the plug would be reflected by a change in current
>> draw. For example, a dead plug draws no current, a flooded one draws
>> excessive current, a worn-out one would use less current.
>
> A worn out one uses the same current.  It's not the coil that wears
> out, it's the catalyst coating that gets fouled.

You might be right - I always assumed the wire got thinner thus increasing
resistance, meaning the plug wouldn't glow as brightly.

I also assumed that glow plug wire was solid platinum, and that was the
catalyst?
Six_O'Clock_High - 25 Oct 2005 05:48 GMT
>>>> I can see where only one battery to charge would be convenient,
>>>> but I don't like the wires -- just something else to get snagged
[quoted text clipped - 62 lines]
> I also assumed that glow plug wire was solid platinum, and that was the
> catalyst?

Not pure platinum.  George Aldrich told me the good ones have rhobidium and
other precious rare metals.

As for the wear out question, it is not a catalyst issue but a contamination
issue that Doug addressed.
Poxy - 25 Oct 2005 13:39 GMT
>>> In article <4Zd7f.26880$U51.14526@news-server.bigpond.net.au>,

<snip>

>>> A worn out one uses the same current.  It's not the coil that wears
>>> out, it's the catalyst coating that gets fouled.
[quoted text clipped - 10 lines]
> As for the wear out question, it is not a catalyst issue but a
> contamination issue that Doug addressed.

Thanks for the clarification.
Doug McLaren - 25 Oct 2005 17:21 GMT
| > A worn out one uses the same current.  It's not the coil that wears
| > out, it's the catalyst coating that gets fouled.
[quoted text clipped - 4 lines]
| I also assumed that glow plug wire was solid platinum, and that was the
| catalyst?

I doubt the wire is (mostly) made of anything special, probably just
nichrome.

But the insides of the glow plug, and maybe the wire too, are coated
with a material that acts as a catalyst.  I think there's some
platinum in it, but there's other things too.  The wire gets it hot to
start out, and the catalyst keeps it hot by making sure that small
amounts of fuel keep burning there.

Either part can fail, though usually it's that something happens to
the catalyst that stops it from doing it's job.  I suspect it been
contaminated, but I'm not sure of the specifics.

In any event, the symptoms of that are pretty obvious -- the engine
dies as soon as you remove the glow driver, but it works fine up until
then.

I doubt the current draw changes at all if the glow plug is fouled our
not.

Signature

Doug McLaren, dougmc@frenzy.com
You have no chance to survive make your time!

quietguy - 24 Oct 2005 22:24 GMT
I plan to do some experimenting with modifying one of those car mobile phone
power supplies - they can easily be modified to change their output voltage,
but am not sure how much current they can handle - but since they are cheap
(from the tip) playing will not be expensive.

If all else fails I will build a 'proper' supply as per one of the circuits
from the rc circuits sites - high power bits from computer power supplies
(again from the tip) might work

I dont know about the interference, but I can check that on the bench, I think

David - who has not much cash, but time to play with stuff

> However, compared to a simple pulsed 12v supply, a constant-voltage drive is
> considerably more complex, requiring a DC-DC converter and reference
> voltage, and will generate considerable EMF which might disturb nearby
> radios, not the best thing at a flying field really.
>
> What have others done? Would constant voltage be worth the effort?
Branko - 25 Oct 2005 14:09 GMT
> I've been thinking about making up a glow driver circuit - I like the idea
> of a constant voltage supply, since it would behave like a NiCad driver -
> it will increase the current if the plug is flooded to help burn off the
> fuel.
A pulsed system will behave the same way, each pulse will deliver as much
more current to a cold plug (proportionally) as would the DC.

>   Also, an ammeter connected to the supply would give a lot of
> information about the state of the plug.
When I assembled my driver, it occurred to me that a piezo transducer across
the drive transistor or the plug could provide audible feedback, but I
haven't tested this idea.

> What have others done? Would constant voltage be worth the effort?
I was inspired to make a pulse driver after seeing a circuit on the WWW.
Hint: A.T's site has links to other RC electronics pages.  I posted a word
picture of my circuit to this news group a couple of years ago, would you
like a repost?

Signature

Branko

Poxy - 25 Oct 2005 15:12 GMT
>> I've been thinking about making up a glow driver circuit - I like
>> the idea of a constant voltage supply, since it would behave like a
>> NiCad driver - it will increase the current if the plug is flooded
>> to help burn off the fuel.
> A pulsed system will behave the same way, each pulse will deliver as
> much more current to a cold plug (proportionally) as would the DC.

I had thought that, although there still would be a slight voltage drop and
thus a drop in current, which attracted me to the idea of the precision of a
constant voltage circuit. In the latter case, an ammeter would give a very
accurate indication of the state of the plug. Of course, that depends on the
resolution of the ammeter, and since I was thinking of using a 3914 driving
a bunch of LEDs. I guess the resolution isn't going to be that great.

> I was inspired to make a pulse driver after seeing a circuit on the
> WWW. Hint: A.T's site has links to other RC electronics pages.  I
> posted a word picture of my circuit to this news group a couple of
> years ago, would you like a repost?

Sure - it'd be great to see what you did. If I went the pulsed route I had
planned to use a 555 timer and a mosfet.
Branko - 26 Oct 2005 12:31 GMT
>> posted a word picture of my circuit to this news group a couple of
>> years ago, would you like a repost?
> Sure - it'd be great to see what you did. If I went the pulsed route I had
> planned to use a 555 timer and a mosfet.

OK, here's what I wrote in 2003...

Observe that a glow plug has a trivial resistance when cold and soon goes
up as it starts to glow; in other words, the element is non-linear just
like a light globe.  I made this observation in my note book "My power
supply can support a glow plug at 1.42V drawing 2.67A, this works out to
3.8W and 0.5 Ohm."

The output stage of my circuit consists of a power transistor, ballast
resistor and the glow plug itself, all in series.  I selected the ballast
resistor so that the maximum collector current of the trany during the
on-cycle would not be exceeded when the glow plug (or whatever the
connector happened to touch) was at zero resistance.  Then I calculated the
on-cycle current and power based on 0.5 Ohm from above; and I finished the
paper design by predicting a duty cycle which would create about 4W
equivalent in the glow plug - 11% at approx 12V.  YMMV depending on the
voltage drop across your chosen trany and ballast resistor.  The pulse
train was generated using the ubiquitous '555.  The power transistor had
the on-current forced into its base through the collector of a driver trany.

For testing, I started with an automotive light globe.  This strategy
enabled me to tweak the duty cycle a bit.  When I replaced the globe with a
glow plug, my CRO showed that the switching transients were huge!  (More so
than with the light globe who's non-linear resistance is actually higher at
the particular duty cycle).  The EMI issue was fixed after considerable
trial and error using a capacitor to earth on the node consisting of the
driver trany collector and the output trany base. This worked far better
than attempts to quench ringing along the high current output chain.

For what its worth...
ballast resistance is 0.7 Ohm 10W tied to +ve rail,
my output transistor is 2N3055 between ballast and plug,
plug returns to earth,
behind this chain...
driver transistor is BC558,
emitter of driver trany is on the +ve rail,
its collector feeds base of output trany shared with 0.22uF EMI cap
its base is fed from 555 pin 3 via 1K Ohm
and...
the +ve rail is protected with a 6Amp diode in case of reverse connection
to 12V SLA

Had I been brave I might have reduced or eliminated the ballast resistor
and adjusted the duty cycle accordingly.

Despite the fixed duty cycle there is little or no problem with wet plug.
Its resistance goes down, it draws more current, it gets hot, its
resistance goes up.  I understand that some folks use a D size NiCad cell
to drive the plug, no regulation, no problem.

Signature

Branko

Poxy - 27 Oct 2005 00:27 GMT
>>> posted a word picture of my circuit to this news group a couple of
>>> years ago, would you like a repost?
[quoted text clipped - 53 lines]
> its resistance goes up.  I understand that some folks use a D size
> NiCad cell to drive the plug, no regulation, no problem.

Thanks for that Branko - the switching transients issue is interesting -
what frequency did you use? Perhaps a higher frequency would reduce this as
the plug wouldn't cool as much between pulses?

I'll definitely use a ballast resistor, not only to limit the maximum
current, but I can also use it as the shunt for my ammeter which will be a
3914 driving a LED array.
Branko - 28 Oct 2005 08:48 GMT
> Thanks for that Branko - the switching transients issue is interesting -
> what frequency did you use?
It worked out to about 700Hz.  I didn't think it would make much difference
and concentrated only on the duty cycle.  If you experiment with it, please
post your findings.  

>             Perhaps a higher frequency would reduce this
> as the plug wouldn't cool as much between pulses?
I wouldn't attribute plug cooling to much because thermal inertia is large
by comparison to the pulse energy.  

When it was on the bread board, I tried larger and larger capacitors on the
output stage with little or no effect.  It was quite a surprise that a
modest capacitor on the base of the final drive transistor would reduce
switching transients through a trivial reduction in rise time.

> I'll definitely use a ballast resistor, not only to limit the maximum
> current, but I can also use it as the shunt for my ammeter which will be a
> 3914 driving a LED array.
Of course you will need a sample and hold to do this but as a level shift
and gain stage will also be necessary both objectives could be met with an
op amp.  On the other hand, once you hear the output transistor scream
under load, you may think about using audio feedback.

By the way, my choice of ballast was based on Ic-max which was published by
the OEM based on continuous duty.  The component is really quite wastefull
and it could be a worthy exercise to reduce its value in combination with
an even shorter duty cycle.

Signature

Branko

Poxy - 28 Oct 2005 10:20 GMT
> When it was on the bread board, I tried larger and larger capacitors
> on the output stage with little or no effect.  It was quite a
> surprise that a modest capacitor on the base of the final drive
> transistor would reduce switching transients through a trivial
> reduction in rise time.

That's true, although I wonder if the longer rise time might lead to more
power dissapation in the transistor? Then again, as you suggest, it might
well be trivial.

>> I'll definitely use a ballast resistor, not only to limit the maximum
>> current, but I can also use it as the shunt for my ammeter which
[quoted text clipped - 4 lines]
> transistor scream under load, you may think about using audio
> feedback.

The 3914 idea was a hang over from my DC-DC converter idea where you're
dealing with stable DC. As you say, with a pulsed circuit it'd be flickering
like mad and would require a bit more circuitry to settle it down. The audio
idea might be more realistic (and simpler!) and more useful at the field.
I'll have to get on and do a prototype...

> By the way, my choice of ballast was based on Ic-max which was
> published by the OEM based on continuous duty.  The component is
> really quite wastefull and it could be a worthy exercise to reduce
> its value in combination with an even shorter duty cycle.

I guess with a 0R7 resistor it'd be dissapating almost as much power as the
plug, but I am concerned about the very real risk of a short-circtuit and
the ensuing smoke from the switching device. I'll have to check what mosfets
I've got laying about and see what they can handle.

Many thanks for your wisdom :)
Martin X. Moleski, SJ - 22 Oct 2005 14:38 GMT
>Martin X. Moleski, SJ Wrote:
>> I'd love to see a .pdf

>You've got it.  As soon as I have updated the dwg, I will make a PDF
>for you.  Give me a few weeks.

Much appreciated!

I'm designing and building a utility airplane--I guess it's a
Stik of sorts, although I'm trying tailfeathers with airfoils
made out of foam and balsa based roughly on the GP
Wagstaff Extra 300.

I'm only making show progress with it.  Maybe I'll get
it to fly next spring.

                Marty
mc_nospam_mike@insightbb.com - 22 Oct 2005 16:54 GMT
What size is the Giles?  Definately interested in getting a DWG file.

>Giles 202 follow up.
>Waiting for parts of engine before I can maiden :( , but after that,
[quoted text clipped - 7 lines]
>months for one plane.  I am not sure of the cost comparison, but I have
>a lot of wood and "stuff" laying around. :D
indoruwet - 23 Oct 2005 03:19 GMT
mc_nospam_mike@insightbb.com Wrote:
> What size is the Giles?

WS = 48 in.
Fuse = 50 in.(from end of rudder to tip of prop nut).
Weight = a bit less than 5 lbs with a 46 on it.

mc_nospam_mike@insightbb.com Wrote:
> Definately interested in getting a DWG file.

Can make a dwg of the preliminary file as I have now.  Finished plan
looks a bit different, like a tapered wing instead of a hershey ba
wing, and a full swinging rudder.  Like always, a lot of little moddin
here and there.

Send me a PM with your e-mail.  DWG format is ACAD 2000, or what ca
you work with

--
indoruwe
R.J. Roman - 21 Oct 2005 23:11 GMT
We kit and sell the "Nemesis 3D-II" which is a nice laser-cut balsa kit.
Check it out at
www.M-A-E.com
There is also a review article on it in the latest issue of 3D-Flyer
magazine.

Randy
Model Airplane Engineering

> Just decided to get back into r/c after a layoff of some time.  Wanted
> to build something, but the only thing out there anymore are ARF's!
> Whatever happened to the kit builders?
>
> Twangmaster
Paul McIntosh - 22 Oct 2005 00:24 GMT
Those are some pretty neat planes!

Signature

Paul McIntosh
RC-Bearings.com
"when steel just isn't enough"

> We kit and sell the "Nemesis 3D-II" which is a nice laser-cut balsa kit.
> Check it out at
[quoted text clipped - 10 lines]
>>
>> Twangmaster
Mike Norton - 22 Oct 2005 02:17 GMT
I am building one of the last Super Sportster .60 kits.  I guess I will have
to build from plans from now on.  The problem is that an ARF costs less than
a kit, when you include covering, glue, etc.  I am willing to pay extra to
build it myself, but this attitude is bound to be rare.

-- Mike Norton

> Just decided to get back into r/c after a layoff of some time.  Wanted
> to build something, but the only thing out there anymore are ARF's!
> Whatever happened to the kit builders?
>
> Twangmaster
R.J. Roman - 22 Oct 2005 13:23 GMT
Based on our ARF vs KIT sales, I can confirm that your attitude is extremely
rare :-)

Unfortunately, our government's policies that facilitate the cheap imported
ARFs are also exporting our decent jobs.  We're trying to compete by
manufacturing our own ARFs.  If "American Made" means anything to you, come
see us on the web...

Randy
Model Airplane Engineering
www.M-A-E.com

> I am building one of the last Super Sportster .60 kits.  I guess I will have
> to build from plans from now on.  The problem is that an ARF costs less than
> a kit, when you include covering, glue, etc.  I am willing to pay extra to
> build it myself, but this attitude is bound to be rare.
>
> -- Mike Norton
tailskid2 - 25 Oct 2005 06:06 GMT
"Importing Kits" from China......an interesting concept to say th
least!!!

Jerr

--
tailskid

Been modeling since '49 - which makes me an Old Fart
Ed Cregger - 25 Oct 2005 07:40 GMT
> "Importing Kits" from China......an interesting concept to say the
> least!!!
>
> Jerry

Why not? I know it sounds strange because of the current trends, but AK
Models said they had some kits for sale. I didn't look any further for them
once I saw the Christen Eagle ARF with a fiberglass fuselage. <G>

As we all know, the Chinese, like us, are in it for the money. If they
become convinced that there is a market, you can be sure that they will fill
the niche'.

Ed Cregger
R.J. Roman - 25 Oct 2005 23:21 GMT
How long do you think it will be before they own us??

Randy
Model Airplane Engineering
www.M-A-E.com

> > "Importing Kits" from China......an interesting concept to say the
> > least!!!
[quoted text clipped - 10 lines]
>
> Ed Cregger
Ed Cregger - 26 Oct 2005 00:31 GMT
What do you mean by "before"?

Ed Cregger

> How long do you think it will be before they own us??
>
[quoted text clipped - 18 lines]
>>
>> Ed Cregger
R.J. Roman - 26 Oct 2005 03:05 GMT
Oh, no... don't tell me!

> What do you mean by "before"?
>
[quoted text clipped - 22 lines]
> >>
> >> Ed Cregger
The Natural Philosopher - 29 Oct 2005 12:30 GMT
> How long do you think it will be before they own us??

Technically, they do already...in the sense of foreign equity invested
in the USA...
R.J. Roman - 31 Oct 2005 00:16 GMT
Are you saying that the Chinese have more invested in America than we
Americans do?

> > How long do you think it will be before they own us??
> >
> Technically, they do already...in the sense of foreign equity invested
> in the USA...
The Natural Philosopher - 01 Nov 2005 00:32 GMT
> Are you saying that the Chinese have more invested in America than we
> Americans do?

I think so..

It depends on what you class as investment...but in terms of actual wall
street funds in bonds stocks and shares..do some research,. and start to
worry...

>>>How long do you think it will be before they own us??
>>
>>Technically, they do already...in the sense of foreign equity invested
>>in the USA...
 
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