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7955 with a Y-Harness?

Old 02-14-2010, 05:42 PM
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T Erickson
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Default RE: 7955 with a Y-Harness?

I absolutely agree with you about wanting all the throw and power I can get when setting up a plane. It's a nice option to be able to back off the throws as needed. I notice a lot of guys are going to 2 servos per wing on 40% planes, with good results, so perhaps we overpower our ailerons. Just saying that for those of us with limited budgets and 9 channel radios, Ys are a reasonable option. Thor.
Old 02-14-2010, 05:58 PM
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Default RE: 7955 with a Y-Harness?

Yup, I just finished assembling a 40%er with 2 aileron servos per wing, and that's a good example of when you're going to want all the torque you can get out of your servos.

Jim
Old 02-14-2010, 08:20 PM
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Default RE: 7955 with a Y-Harness?


ORIGINAL: Hammbone


ORIGINAL: nonstoprc


ORIGINAL: Hammbone

ORIGINAL: nonstoprc


ORIGINAL: Hammbone

A standard connector is only rated at 3 amps. If you try to push 6 amps through a standard connector you will get a huge voltage drop.

Jim
what standard connector? Even if it is rated at 3A, can one use a better one?

My point is Y-harness can be chosen so it is not a bottle-neck. The same argument goes to other components.

The other point is of course the chance that the 6A load can happen.
A standard connector is what comes on a servo when you buy it. A standard connector is what you plug into the output ports on a rx. We can not upgrade them because the upgraded plug can not be plugged into the rx. This is why many people use Power Expanders. A Power Expander allows you to plug each servo into it's own port. Each servo now has it's own dedicated current flow. You don't use ''Y''s which cut the supplied current flow in half.

Jim
The servo connector is designed to handle the stall current. It should not present a problem.
It doesn't present a problem if you are only powering ONE servo through it, but if you are powering TWO servos through it (like when using a ''Y''), then it IS a problem.

Jim
No. The connector (with the servo) is for one servo only.

If the Y-harness is designed to handle the 6A load, the two servos will get its 3A capacity.

The load on the receiver is something one need to look into as well.

This URL http://www.rcuniverse.com/forum/m_93...tm.htm#9344418 has the info on the load that futaba 2.4 608 receiver can handle.






Old 02-14-2010, 10:17 PM
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Default RE: 7955 with a Y-Harness?

You just don't get it.
There is no "Y" harness that is rated at 6 amps, not if it has standard connectors on it. Even if you had no connectors and solder all the wires together, you still are feeding 2 servos through one standard connector coming out of one port on the rx. A standard connector is only rated at 3 amps.

The input of a "Y" harness is a standard connector that is rated at only 3 amps. You have just limited the current flow going through that one standard connector.
Now when the "Y" splits off to 2 separate servos, you have divided that current flow in half and you are down to 1.5 amps per servo. You have limited your current flow.
It is possible to push more current through a standard connector, but not without getting excessive voltage drops.
Limited current flow and voltage drops = diminished servo torque.

I don't know how to explain it any simpler than that.

Jim
Old 02-14-2010, 10:35 PM
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jsenicka
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Default RE: 7955 with a Y-Harness?

same essential issue on a 33% SD yak I am completing. I need channels for choke and cutoff.
I will run a power expander and program 7955 to match throws.
So only use 2 channels for ailerons, but get full power to servos.
Old 02-14-2010, 11:18 PM
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Default RE: 7955 with a Y-Harness?


ORIGINAL: Hammbone

You just don't get it.
There is no ''Y'' harness that is rated at 6 amps, not if it has standard connectors on it. Even if you had no connectors and solder all the wires together, you still are feeding 2 servos through one standard connector coming out of one port on the rx. A standard connector is only rated at 3 amps.

The input of a ''Y'' harness is a standard connector that is rated at only 3 amps. You have just limited the current flow going through that one standard connector.
Now when the ''Y'' splits off to 2 separate servos, you have divided that current flow in half and you are down to 1.5 amps per servo. You have limited your current flow.
It is possible to push more current through a standard connector, but not without getting excessive voltage drops.
Limited current flow and voltage drops = diminished servo torque.

I don't know how to explain it any simpler than that.

Jim
No, u did not get it.

A 22 AWG wire can carry max 7A current. THis is the HD type of Y-harness you need. For the Y harness.

The current draw at the receiver ports is limited by the design of the receiver. One can technically connect the battery to the servos to get more current (and thus bypass the receiver limits).

Should this address your concern at the 3A connector?









Old 02-14-2010, 11:20 PM
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IFlyEm35
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Default RE: 7955 with a Y-Harness?


ORIGINAL: nonstoprc


ORIGINAL: Hammbone

You just don't get it.
There is no ''Y'' harness that is rated at 6 amps, not if it has standard connectors on it. Even if you had no connectors and solder all the wires together, you still are feeding 2 servos through one standard connector coming out of one port on the rx. A standard connector is only rated at 3 amps.

The input of a ''Y'' harness is a standard connector that is rated at only 3 amps. You have just limited the current flow going through that one standard connector.
Now when the ''Y'' splits off to 2 separate servos, you have divided that current flow in half and you are down to 1.5 amps per servo. You have limited your current flow.
It is possible to push more current through a standard connector, but not without getting excessive voltage drops.
Limited current flow and voltage drops = diminished servo torque.

I don't know how to explain it any simpler than that.

Jim
No, u did not get it.

A 22 AWG wire can carry max 7A current. THis is the HD type of Y-harness you need. For the Y harness.

The current draw at the receiver ports is limited by the design of the receiver. One can technically connect the battery to the servos to get more current (and thus bypass the receiver limits).

Should this address your concern at the 3A connector?

Can a standard JR connector pass more than 3 amps?
Old 02-14-2010, 11:49 PM
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Default RE: 7955 with a Y-Harness?

remember that you can use the battery slot for one servo...and you save one. You can use a Y to connect one servo and battery too.

regards,
Old 02-14-2010, 11:51 PM
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Default RE: 7955 with a Y-Harness?

I'm using the 922 powersafe rx.
Old 02-15-2010, 09:21 AM
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Default RE: 7955 with a Y-Harness?

I know you don't want to hear this, but your best solution is a 12X tx and a 1222 rx. That's what I use. It costs some money, but in the long run, it doesn't cost more if you think about the money you save on a Power Expander and HD switches for each plane that you get. It also saves weight.
The next best thing would be a Power Expander with a 921 rx.
Your other choice is to use "Y"s and understand that you will have a loss of servo torque. At least you're using a Powersafe rx, so you're not getting any losses on the input side of the rx. Many guys use poor components throughout and they get losses throughout their entire system. By the time the current gets to the servo, the amps and voltage is very low after dropping several times.

It's your plane and your choice.

Jim
Old 02-15-2010, 09:58 AM
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Default RE: 7955 with a Y-Harness?

Check this out http://www.flying000giants.com/forum...ad.php?t=50865 (remove 000).

You can use extra ports from R922 to power the y-harnessed servos.
Old 02-16-2010, 12:27 AM
  #37  
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Default RE: 7955 with a Y-Harness?

I've been running this EXACT setup in my 110 for a year with no problems.

Is it ideal, no, does it work with no problems, YES.

Build it, fly it, and move on.

geeze
Old 02-16-2010, 01:12 AM
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Default RE: 7955 with a Y-Harness?

I still do it the old school method,as I fly at a very remote field with no frequency issues. I run 2 receivers,2 separate batteries and switches. I then set the plane up to fly on ether system if one fails ,half the digitals go into fail-safe,the other side controls the remaining surfaces.The other benifit is that I have full amperage at all times to the High-draw digitals,as the load is spread between the 2 batteries and HD switches.The weight penalty on a 15lb plane is maybe 5oz and the servo wire routing looks very sanitary.Now this is only possible on 72mhz systems I don't think you can do it on 2.4 gig.By the way I have seen planes lost to the 2.4 systems and if you talk to a top electrical engineer or tech,the 2.4 Radios have yet to reveal there weakness'and they will not cover up a bad install or the lock-up that happens when the receiver is temporally unable to provide enough current flow causing a voltage drop below 4vts causing the receiver to "Grey-out"and reboot while in safe mode not cool hovering 3feet off the deck!! I can post photos of my dual receiver set up if anybody wants ,You can also pair your 9 channel with a 6 channel if needed,Brian
Old 02-16-2010, 10:55 AM
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Jake Ruddy
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Default RE: 7955 with a Y-Harness?

Reality is, can it be done? Yes it can and many do it and many have been doing it for years.

Will you get the full torque out of the servo this way? No, there will be some voltage loss due to the connections used on servos and receivers. That being said today's servos have more than enough torque to exceed the demands we put on them.

There are those who live and die by power supply and weight savings and there are those who don't and both still fly the heck out of their planes. I personally have Y on my 4 8611s in my H9 35% 260 in the wings and can 3D it with the best of them. It snaps crisp and stops when I want. Would be it even better with a power expander? Yes the extra voltage would help a bit but it flies just fine the way it is.

You need to take all the input on this topic with a grain of salt. Many have been flying Li-ons packs for years with limited burst availablity without any issues and the sky wasn't falling before A123s came out
Old 02-16-2010, 11:06 AM
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Default RE: 7955 with a Y-Harness?

ORIGINAL: Jake Ruddy

Reality is, can it be done? Yes it can and many do it and many have been doing it for years.

Will you get the full torque out of the servo this way? No, there will be some voltage loss due to the connections used on servos and receivers. That being said today's servos have more than enough torque to exceed the demands we put on them.

There are those who live and die by power supply and weight savings and there are those who don't and both still fly the heck out of their planes. I personally have Y on my 4 8611s in my H9 35% 260 in the wings and can 3D it with the best of them. It snaps crisp and stops when I want. Would be it even better with a power expander? Yes the extra voltage would help a bit but it flies just fine the way it is.

You need to take all the input on this topic with a grain of salt. Many have been flying Li-ons packs for years with limited burst availablity without any issues and the sky wasn't falling before A123s came out
I agree with this post, but remember the low voltage rx brown out issue with Spektrum rx's before they were fixed to have a quicker reboot time?
Lots of guys were crashing planes because of rx brown out due to poor power distribution systems.
I'd say that would qualify as the "sky falling".
Some people still have problems with rx brown outs due to poor power distribution.

There's really no good reason not to set up your plane with good power distribution, especially now that we have all these new devices which maker it easy for us to do so. It can be done inexpensively too, with JR Powersafe rx's, so cost is not even an excuse any more.


Jim
Old 02-16-2010, 12:27 PM
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Default RE: 7955 with a Y-Harness?

We need an upgraded JR/Futaba connector for the receivers. Maybe something like the Deans brand? Something that can handle maybe 10 amps to remove the connector bottle neck. Then it would be up to the wire gauge. This would help those who can't use JR power safes or don't want power distribution systems. Does such an animal exist that fits the Futaba/JR port on the receivers? Is it possible?
Old 02-16-2010, 01:42 PM
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Default RE: 7955 with a Y-Harness?

I use them most of the time on ailerons, and have used them once or twice on Rudder..


but what do I know, I'm just an unfrozen caveman sport flyer.
Old 02-16-2010, 05:33 PM
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Default RE: 7955 with a Y-Harness?

The solution is to power all servos from the battery/ batteries through your own buss system EG wire or Pc board then run redundant supplys to the reciever. Then all you have to do is run the signal wire to the reciever then the only worry is the the signal being split by the y-harness the only servos that I am aware of that may have issues is the Futaba.

This is the same a Power expander except that they amplify the signals on some of them. So if you are fairly good at solidering you will have all the amperage the servos want the week link then will be the batteries and the signals to the servos.
Old 02-16-2010, 07:59 PM
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Default RE: 7955 with a Y-Harness?


That is the way to do it. Simple, reliable and effective. Somebody could even come out with a product like that.
Old 02-16-2010, 09:05 PM
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Default RE: 7955 with a Y-Harness?

Jr is on the right track with their Powersafe rx's. Now if they would just modify the Powersafe rx's a little so that they have more than one output port available for certain channels (like the ailerons, elevators, rudders, flaps, and a couple of auxiliary channels to cover anything else), then we would be all set. All they have to do is make the bus a little bigger to accommodate more ports. It shouldn't be that hard to do. Hopefully they are working on doing so right now. :-) Are you listening, Horizon?

This is what I would like to see.

Jim
Old 02-17-2010, 09:00 PM
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Jake Ruddy
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Default RE: 7955 with a Y-Harness?


ORIGINAL: Hammbone

ORIGINAL: Jake Ruddy

Reality is, can it be done? Yes it can and many do it and many have been doing it for years.

Will you get the full torque out of the servo this way? No, there will be some voltage loss due to the connections used on servos and receivers. That being said today's servos have more than enough torque to exceed the demands we put on them.

There are those who live and die by power supply and weight savings and there are those who don't and both still fly the heck out of their planes. I personally have Y on my 4 8611s in my H9 35% 260 in the wings and can 3D it with the best of them. It snaps crisp and stops when I want. Would be it even better with a power expander? Yes the extra voltage would help a bit but it flies just fine the way it is.

You need to take all the input on this topic with a grain of salt. Many have been flying Li-ons packs for years with limited burst availablity without any issues and the sky wasn't falling before A123s came out
I agree with this post, but remember the low voltage rx brown out issue with Spektrum rx's before they were fixed to have a quicker reboot time?
Lots of guys were crashing planes because of rx brown out due to poor power distribution systems.
I'd say that would qualify as the ''sky falling''.
Some people still have problems with rx brown outs due to poor power distribution.

There's really no good reason not to set up your plane with good power distribution, especially now that we have all these new devices which maker it easy for us to do so. It can be done inexpensively too, with JR Powersafe rx's, so cost is not even an excuse any more.


Jim
Let's be honest that the reason this was happening was because people were using poor choices in batteries. How many used a 4 cell pack like they did for their FM receiver. When people use good batteries the brown out issues isn't really there.

I personally have had 2 H9 260 35% planes.. the first one I had a smartfly unit in with seperate ailerions running to it. I lost it due to a wing failure. The 2nd one I decided to get a Powersafe receiver instead because I used the smart-fly elsewhere. I am still flying that plane using Y's on the ailerions and I can't feel the difference between the 2. I flew Intermediate last year which has some snaps and lots of 3D.

I am not saying there isn't a difference but I used heavy duty 20 guage wires with 2 x A123 packs and couldn't really tell a difference between the 2 planes.

Ultimately I am getting rid of my 9303 and getting a 12x anyhow so it won't really be an issue for me in the future, but I am doing that for the modes and rates functionality alone.
Old 02-17-2010, 09:13 PM
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Default RE: 7955 with a Y-Harness?

Poor battery choice was not the only reason for the brown outs. Limited current flow is caused by many different things.

Plug an A123 battery into a rx with a standard plug and it just doesn't matter if the battery is rated at 69 amps when the plug is only rated at 3 amps.
It also doesn't matter that the battery is rated at 69 amps if you run it through a switch that's only rated at 5 amps with standard connectors only rated at 3 amps.
It also doesn't matter if the battery is rated at 69 amps if you run it through undersized wire, or a reg with a low amp rating.
Every single component used must be up to the task. All it takes is one weak link, but many guys still put together set ups with several weak links.

Jim
Old 02-18-2010, 11:47 AM
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Default RE: 7955 with a Y-Harness?

ORIGINAL: nonstoprc

Check this out http://www.flying000giants.com/forum...ad.php?t=50865 (remove 000).

You can use extra ports from R922 to power the y-harnessed servos.
This "X harness" is an interesting idea, and sounds like a great solution for you guys with 9 channel tx's.

You should just use the 1222 rx with a 9303/9503 tx, and then use the extra rx ports for your power (not signal) to the extra servos. You'd have 2 extra ports for ailerons, and one extra port for rudder.

This could work real good, and if retailers were smart, they could even start selling these "X harnesses".

The 1222 rx is only about $60 more than a 922 rx.

Now here's a simple and inexpensive way for you to get good current flow without forking out the extra money for the high dollar 12X tx. (Although I think the 12X is worth every penny)


Jim
Old 02-19-2010, 08:09 AM
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Jake Ruddy
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Default RE: 7955 with a Y-Harness?


ORIGINAL: Hammbone

Poor battery choice was not the only reason for the brown outs. Limited current flow is caused by many different things.

Plug an A123 battery into a rx with a standard plug and it just doesn't matter if the battery is rated at 69 amps when the plug is only rated at 3 amps.
It also doesn't matter that the battery is rated at 69 amps if you run it through a switch that's only rated at 5 amps with standard connectors only rated at 3 amps.
It also doesn't matter if the battery is rated at 69 amps if you run it through undersized wire, or a reg with a low amp rating.
Every single component used must be up to the task. All it takes is one weak link, but many guys still put together set ups with several weak links.

Jim
That 3amp number comes from what they can handle constantly. Peak wise they can handle more.

Besides.. since every servo uses 22guage wire and the same connector you can spend all you want on everything before the servo but you still end up with that same weak link in there.

At any rate, this is an endless debate... it happens everytime a thread like this comes up. We will agree to disagree, I see and understand your points but a plane will fly just fine either way.
Old 02-19-2010, 09:04 AM
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Default RE: 7955 with a Y-Harness?

That's why I said that the servo manufacturers should come up with a 5-10 amp servo connector. Then that bottle neck would be gone (or reduced).

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