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18 AWG extensions

Old 03-04-2004, 10:06 PM
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woodscra
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Default 18 AWG extensions

Does anyone sell them pre-made, ready-to-go? Really only interested in 36". I am not interested in making my own.

Thanks in advance for any information.
Old 03-04-2004, 11:27 PM
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jschenck
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Default RE: 18 AWG extensions

[link=http://servocity.com/html/36__servo_extensions.html]Servo City extentions[/link]

These are 20 Gauge - I bought some and really like their product/price and service. Might give them a call if you need/want 18 gauge.
If you are pushing that much power, be carefull about not drawing too much through the receiver(s) !
Old 03-05-2004, 12:23 AM
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mglavin
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Default RE: 18 AWG extensions

I don't think anyone offers servo extensions larger than 20 awg and that’s pushing it. The OEM connectors will not work with the large gauge wires.

I'm using twisted wire 22 gauge/19 strand servo extensions on my models with long extension and single high power servos. I just completed rolling my own last night for a refit of one of my Carden 40% Caps with the Emcotec RV servo interface. Four 54” extensions to the rear for the elevator servos, worked out real nice.

Airwild Hobbies offers some nice HD 22 gauge twisted wire extensions.

I recall hearing Powerflite offered HD extensions as well.
Old 03-05-2004, 06:52 PM
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Lynx
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Default RE: 18 AWG extensions

Power isn't the only reason to use lower gage wire. Efficiancy is. You could gain as much as 5-10+% flight time by using higher gage wire, because the wire resistance is lower it wastes less power, and therefore there's more power at the source. These aren't numbers most people deal with, but as long as weight isn't becoming a problem, higher gage wire is always better.
Old 03-05-2004, 10:55 PM
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mglavin
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Default RE: 18 AWG extensions

Lynx

I'd like to see the numbers that support 5-10% increased flight time assertion... I understand the wire resistance thing and voltge drop across long wires. But 5-10% increased flight time seems like a strech.
Old 03-06-2004, 01:23 AM
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Lynx
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Default RE: 18 AWG extensions

It depends on the battery pack you're using. Essentially, when a battery has a lot of power drained from it all at once the amount of 'charge' you get out of the pack in total is less than if there is a lower level current drain that is constant, the same overall power is recieved at the source, but the pack is under less stress, the chemical reaction takes place at a more natural pace so less is wasted in the form of heat due to internal resistance's in the batteries, so they last a little bit longer. Large value caps allow you to do this, because they can deliver virtually their entire charge instantaniously with very very low loss and charge gradually back up from the battery. the 5-10% increased flight times are off the hip numbers and I doubt I'd ever get to the point of being able to prove that. The bigger the battery pack the less advantage would be gained. Lipoly systems would have the most benefit because they suffer most from peak drains. Their actual charge can be as much as 60% less than the packs rated capacty if you discharge them too fast. That's also why pack's 'recover' if you let them sit for a bit after heavy use, because the chemistry has time to re-ballance and some of the power is recovered from the nooks and crannies (chemically speaking) The trick is to properly ballance a resistor and a capacitor array to let the capactors charge as fast as possible without stressing the pack, without cutting voltage if the capacitors are drained, using a bypass circuit might very well waste the extra energy gained though. It's just an idea, nothing that'd every be truly practical, and entirley too complex to put in the air for most modellers. Just something fun to play with.
Old 03-06-2004, 08:43 AM
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bob_nj
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Default 18 AWG extensions

Mike, is that 54" after twisting?
Reason I ask is that the Powerbox manual says not to exceed 6 feet in extension wire.
Is there a similar situation with the Emcotec?
Tried my first Powerbox Competition last weekend and its sweet
Old 03-07-2004, 03:37 AM
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mglavin
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Default RE: 18 AWG extensions

Bob


Can't say what the wire length was prior to twisting, as I purchased the wire from Competition Products already twisted in 12' increments a while back.

I don't recall reading anything about maximum wire lengths. I'll check the manual.

Obviously shorter extensions are better. Makes sense Modelbau suggesting 72" max length.
Old 03-07-2004, 05:24 AM
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jbflier
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Default RE: 18 AWG extensions

You can get 22ga pre assembled wire from any hobby shop that deals with Horizon. Length is up to 44"................[8D]
Old 03-07-2004, 06:53 AM
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bob_nj
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Default Wire Strand Count ?

Mike mentioned that he uses 22awg 19 strand hookup wire which got me to thinking[:-]
I have several brands and types of 22awg wire accumulated in the shop. Wonder what the skinny is on that stuff.
I'ts always a chore to look at some of the wire and wonder if it's heavy duty or not etc.
I use the Custom Electronics wire the most so I decided to cut and count. It is in fact a silver colored 19 strand wire @ .005 in thick.
Cut one of my Expert wires and it is gold in color with lots more than 19 strands, but it is .002in thick.
Without getting anal about it, what is better in a purist sense for our needs, thicker low count, or higher count thinner wire?
Maybe it doesn't make a hoot, but it's interesting to note the differences in what we buy as "heavy duty" wire.
Thanks and take care_bob
Old 03-07-2004, 04:02 PM
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Lynx
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Default RE: 18 AWG extensions

Thicker wire is better electrically, more wires just make it easier to bend. As long as you can deal with the stiffness of the thicker wire, use it.
Old 03-31-2004, 04:01 PM
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blkbird68
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Default RE: 18 AWG extensions

I don't think anyone offers servo extensions larger than 20 awg and that’s pushing it. The OEM connectors will not work with the large gauge wires.

Actually, 18awg will "work" in a standard connector.....but the connector has so much resistance compared to the wire that there is no real advantage to any wire over 22awg on a standard connector..
Old 03-31-2004, 05:00 PM
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Lynx
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Default RE: 18 AWG extensions

The voltage drop will still be lower, the connector loss is nothing compared to the loss in the cable itself.
Old 03-31-2004, 05:10 PM
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Default RE: 18 AWG extensions

ORIGINAL: Lynx

The voltage drop will still be lower, the connector loss is nothing compared to the loss in the cable itself.

I have done alot of testing on this and the connectors show over one volt drop at 2 amps but replace the connectors with 3 pin deans and over a 60" long extension of 22awg the total recorded voltage loss at 4 amps was 0.06V. the losses in the wire are nothing compared to the losses across the "stock" connector.

How is your servo booster project going Lynx???
Old 03-31-2004, 11:30 PM
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Default RE: 18 AWG extensions

Who makes the best connectors to use? OEM?
Old 03-31-2004, 11:35 PM
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Default RE: 18 AWG extensions

Actually, RC Accessory just started selling Heavy Duty 18 gauge servo extensions, check their website now
Old 04-01-2004, 12:44 AM
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blkbird68
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Default RE: 18 AWG extensions

ORIGINAL: shortman

Actually, RC Accessory just started selling Heavy Duty 18 gauge servo extensions, check their website now
My question would be why??? I have made 20 and 18awg extensions for testing and as I stated before...with stock style connectors there was absolutely no performance gain over an equivalent 22awg extension. All you will get in that case is more weight for no apparent reason. The only servo I know of (excluding the Tonegawa-Seiko servos) that draws enough current at full load to need more than the capabilities off 22awg wire is the Volz 300oz-in model digital. It draws 4.5 amps max. and for that servo 20awg would do. Although I haven't tested servos like the 8611 or its hitec or futaba counterparts. I would expect that they would be about the same or a little less current hungry than the Volz, therefore, 22 or 20awg would be plenty. As long as better connectors are used 22awg will be plenty for most of the servos any of us use. Although, obviously you can fly just fine without making the changes to the connectors, it will make a significant difference in performance if you do change them out. One of the best examples I ran across when testing to convince someone of the benefits of ditching the stock connectors where possible, was the fact that when loaded, the servos that were being fed through stock equipment got very hot. However, the same servo, holding and moving the same load but with deans 3pin connectors and using an external buss, barely got warm. How many of us use extensions as long or longer than the 60" extension that I tested?? I tested the 22awg at that length for one reason. I had several people that made the claims about long extensions being the main source of voltage loss. I had people telling me that anything over 24" needed to be heavier to keep losses due to the wire down. Plain and simple I proved this to be totally false. Yes, wire resistance is dependent upon length, but my point is we don't use long enough wires for that to be of more than minor relevance.
Old 04-01-2004, 11:57 AM
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Rodney
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Default RE: 18 AWG extensions

I have to dissagree with Lynx on a couple of things. 1) you will most often get most losses in the connectors, not the wire, unless you are using very small gauge wire. and 2) many strands of small wire are better than fewer thicker wires for a number of reasons, the two most important is that it is more flexable and less subject to failure due to vibration or flexing and second, especially at the higher frequencies, more current flows on the surface area than in the internal area of a conductor and many small wire have more surface area than the larger wires if the total cross sectional area is the same in the two different wire bundles. In our usage this is rather inconsequential so has little bearing in real life.
Old 04-01-2004, 04:10 PM
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Default RE: 18 AWG extensions

Rodney,
I totally agree with you. If you are using 18 guage wire and standard connectors I'd be more worried about the connectors failing from the strain imposed upon the connectors from the stiffness of the wire and vibration. I could see using 18 guage as a trunck line with smaller 22 guage wires tapped off it but because the loss is mainly in the connectors I don't see any real value being added.

Just my 2 cents worth and no my experience isn't from large model airplanes but from wiring electronic devices on vibrating industrial machines.

John
Old 04-01-2004, 06:09 PM
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blkbird68
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Default RE: 18 AWG extensions

more current flows on the surface area than in the internal area of a conductor
this is only true at high frequencies. If you work out the equations to figure resistance increase due to skin effect you will find that you have to get to around 20KHz frequency to get even a 3% increase in resistance. And the equations used are conservative so the actual increase in resistance is even less than that. Since skin depth is inversely proportional to frequency, the fact that our power only gets pulsed at 50Hz with non-digital servos and in the 250Hz neighborhood for digital servos you will find that the increase in resistance at those frequencies due to skin effect are practically zero. Skin depth is the distance below the surface of a conductor at which the current density has drop to only 37% of the value at the surface and at our power system frequencies you would have to have one heck of a big conductor before you reached that point.
Old 04-02-2004, 12:23 PM
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Rodney
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Default RE: 18 AWG extensions

Blkbird68, if you read the last line of my above post, I said the same thing--not pertinent in normal RC usage.
Old 04-02-2004, 12:32 PM
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Default RE: 18 AWG extensions

I did read your statement..
Old 04-02-2004, 05:14 PM
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Lynx
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Default RE: 18 AWG extensions

I stand corrected on the connector issue, didn't relize stock connectors were that bad, I've never done any tests. <inserts foot in mouth> As far as the booster goes it's going along well, at least that was till I had to put it on hold => Split up with my girlfriend whom I was living with, and it's taken quiet a while to get that whole mess put aside, rough time for me lately, but I'm in my own place now and all the messy details were worked out without anyone drawing blood <G> Need to pick up a new programmer as I killed the last two because I misread something in a manual and fried them both in one weekend =\ The code was coming along nicely. After I get back to work on it within the next month I'm going to use a much more capable chip to do some of the testing and then work that into the smaller one's.

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