foodstick

I have a few of these expensive servos I was given by a guy.. I am sure he has moved away from the 4.8 older equipment. I typically use 4.8 volts on low tech scale planes,and I am a Futaba 7c user. Is there any reason I should not mix this servo with a Futaba FASST system? I know I can probably just swap the plugs and physically try them on the bench. But I was wondering if anyone knew if they have had a history of only working with the JR system ?

I would hate to find out they work for a short time and have an issue for the long haul.

Truckracer

My Feedback: (19)

These were designed as a first generation heli tail rotor servo. They are lightning fast but had very low torque plus they were rated for 4.8V. only which is an odd voltage these days with LiFe and LiPo batteries being almost standard. You could use a voltage drop diode(s) in line with the + lead to reduce the voltage if something other than 4.8V is used. Other than a smaller sport plane, I don't know where you would use them in most airplane applications. No need to rewire them, just plug them into the Futaba receiver and go as with all JR / Futaba servos.

If you would want a few more, I know where you can get them for hauling them off! I have a couple much better, higher torque Futaba tail rotor servos that could actually be used in an airplane. Might even be a few rate gyos in the box too that could be used on your WW1 planes.

foodstick

Ahh the Zen Master himself !
What have you been up to? you sure answered more than I even thought to ask...and the answers had nothing to do with my pre conceived worries.
I see the price marked on the box these come in and I feel like a high roller. Thanks for the info, as I figured they were slow and torquey, not fast and accurate.

rgburrill

This answer is wrong in so many ways. LiPo is way too high a voltage for most servos so a BEC is typically used.- a diode just won't cut it. Expensive LiFe's may be standard with those who like to spend a lot of money but most people still use NiMH or NiCd which are 4.8 volts. 8.7Kg is NOT low torque. Most standard servos don't have more than 5 Kg.
The JR connector may have a different shell than the Futaba but it could work without modification. The main thing to look for is the reversal of the power and ground leads. I recall when I used Futaba servos with Airtronics receivers I had to trim the tab on the connector shell and swap the power and ground leads but I've never used JR.

Truckracer

My Feedback: (19)

Bad info you say? Let me address that! First, the 8700 G is a fairly heavy, metal geared coreless servo that looks like it should have lots of torque, but it doesn't! at 49.9 oz in. That is low torque in my world for that servo configuration and it doesn't like to deliver that torque for any length of time or it may overheat and fail. Yes standard servos have somewhere between 30 and 45 oz. in of torque at 4.8V and I call that low also in the modern world for a standard sized servo.

Regarding the use of diodes for voltage reduction to the servo. This was a standard method of reduction in the heli world for quite some time when only the tail rotor servo required the low 4.8V supply. Align, Wrong Way RC and several other companies supplied servo extensions with one or two diodes in line with the + lead to reduce the voltage supplied to the servo. This worked extremely well. No I would not use this method to supply power to an entire radio system from a higher voltage battery as a voltage regulator would serve much better for that purpose but most modern servos are rated for higher voltages making a VR obsolete.

Expensive LIFe or LiPo batteries? Not sure where you live but I can buy quality LiFe or LiPo batteries at much lower costs than I can buy comparable rated Nixx batteries. And the Lixx batteries are far more reliable and long lived but that is food for another debate. I will say that since switching to Lixx batteries years ago, my total cost of ownership over time for airborne batteries is far less than it was for Nixx batteries and I bet I bought many $$$ worth of Nixx batteries over several decades.

The JR and Futaba connectors have always had the same wire configuration only differing in wire colors and housing configuration. Only old Airtronics was different but that brand was never mentioned in this thread until your response and even Airtronics switched to standard configuration for all their later connectors.

foodstick

Well I will keep it in mind that even though this servo looks and feels like a beast. It is not a high torque machine...

I know the WW1 guys here are still swimming against the stream by sticking with nicads, but we don't throw much load onto them and for the most part are really having good luck.. I am becoming addicted to powering those 1/4 WW1 planes with lipos though ! I have a N28 project underway and may get into an Albatros one of these days

I will tell you the best buy on running a big nicad receiver pack these days. On the WW1 type planes you always need that weight up there anyhow. We buy the $12.00 rc car nicad batteries. and split them up. If you buy two packs you get enough sub c's to make three nice receiver packs. Also if you carefully pull them apart you can get away with just removing two end batteries and soldering on new leads on both packs. Then you combine the two separate cells into the third pack...

Truckracer

My Feedback: (19)

I've used those car packs before. Good source for reliable, high capacity NiCd cells. I've pretty much eliminated Nixx batteries from my fleet these days though.

Regarding the 8700G, to its credit it was probably the first high speed tail servo available that was reliable. Cutting edge in its time ..... early 2000's. Dang they were expensive though!