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**lenb** · 10-26-2017, 10:55 AM

Hi Tom,
Congratulations on the arrival of the Bidule. It's always exciting to get the new ARF smell in the shop.
Nosewheel MUST have a servo saver system. There is no way you can operate the plane long term without it. It will fail.
The servo for that is the Spectrum S9020 or Savox servo listed somewhere. After more than 250 hours of operating time on Bidules, I can tell you the sterring system Scot developed is bulletproof. There are a couple different ways you can arrange the parts, it doesn't have to be the one piece unit shown on the website. Jim D used a creative approach to install the system parts into his latest Bidule and it works quite well.

As for the rest of the system, its up to you what flavor servos you use. You want high torque metal gear quality servos.
Spektrums new 6300 servo is the hottest one out there now, SPMSA6300 , but they're also expensive. JR has the awesome DS8931 which I have in mine right now, super tight and power to spare.
On the budget side, Hitec has decent servos in the 7955 or 5585 range, The downside is small amplifiers, so don't stall the servos or they cook.

Another popular choice is the Spektrum 6265 which I flew in mine for 170 hrs before building the second bidule

Throttle and choke can be standard servos, but good quality. Rudders can also be standard ( 150 oz +-) servos, I use spektrum 6150's for throttle, choke and rudders
Tow release should be super strong, same as the elevators, ail and flaps,

Len

**Stew2** · 10-26-2017, 10:57 AM

Hi Tom,

When I originally put my Bidule 170 together I went with JR DS8411 HV on everything except throttle, choke and steering. Throttle and choke were JR DS821HV servos and steering was a Savox 0236MG servo. Through time, this is what I found out. The JR DS8411HV servos did not like the hammering environment on the rudder and flap surfaces. Mind you, I don't think they are a bad servo, but with a ZDZ 180 up front shaking the crap out of the airframe, the surfaces hammered the servos hard at center point and though the 8411's never failed, they just jittered at center with no load. This is a known condition for the 8411's and it even says right on the package that this can occur, and will stop once flight loads are placed on the surface. I just didn't like the jittering and chose to change the servos on the rudders and flaps. The ailerons and elevators have not shown this condition in over 150 hours of flight time and I have not changed those servos since the initial build. The Savox steering servo definitely faded through its life and was changed to a Spektrum 9020 after 120 hours. The Spektrum 9020 is definitely stronger than the Savox servo and I can't imagine it not outlasting the Savox servo. I would not install any other servo for the nose gear steering. Following the center point jittering, I changed the flap servos to Spektrum A6265 servos and the rudder servos to Spektrum A6150 servos. I use all high voltage servos in my Bidule and they all receive power through a Competition Powerbox. I like the Powerbox units so I have regulated voltage to my servos, which eliminates any high voltages from batteries fresh off charge and I have real time mAh consumption data for my batteries so I know when I have to change them out. So the summary is, my current servo selections are:

Throttle and Choke - JR DS821HV
Rudders - Spektrum A6150
Elevators, Ailerons and Tow Release - JR DS8411HV
Flaps - Spektrum A6265
Steering - Spektrum 9020

Classically, I am a dyed in the wool JR guy, but the Spektrum servos have really measured up here when combining application and cost. That being said, I would seriously consider a servo line up as follows on a Bidule 170 build: (No real logic here other than being anal retentive around a single brand name when you look inside the airplane..)

Throttle, Choke and Rudders - Spektrum A6150
Elevators, Ailerons, Flaps and Tow Release - Spektrum A6265
Steering - Spektrum 9020

Just opinion, no authority. Let us know what you end up with, it is always great to get the data on experience.

Careful with the Bidule, it is very, very addictive!! Enjoy!

**JimD** · 10-26-2017, 11:15 AM

Hi Tom,

Servo selection has two main considerations, power needed to drive a given function and battery type (voltage) being used.

Actually, the decision making process starts with the batteries. Are you going to use NiCd, NiMH, LiFe, or LiPo. Higher voltage enables higher torque ratings.

Both of my Bidule 170's are setup the same way and have proven performance over 150+ hours of flight time towing, so here are my choices and reasons for those choices.

First, my batteries of choice are 2-cell 2,500mAh 6.6v A123 packs from NoBS Batteries. Planes carry three of these, one for ignition and two for the radio gear.

Desert Aircraft ignition module can operate from this pack without the need for a step down voltage regulator. Ignition uses about 500mAh per hour.

Hitec HS-5645MG servos drive each rudder plus throttle and choke. These servos can operate directly from the 6.6v, but not rated for higher than that. They are digital servos with good torque (165oz-in) and retail for around $40 each.

Hitec HS-7955TG servos drive the ailerons, elevators, flaps, tow release, and brakes. Again, these can operate directly from the 6.6v, but are not rated for higher than that. The HS-7954SH servo is the same size, power and price, but is rated for high voltage up to 7.4v. Both are digital servos rated at 333oz-in of torque @ 6.0v and retail for around $100 each.

Spektrum S-9020 servo drives the nose gear steering and, because of its physical size and power, is the best choice for this function no matter what other servos and/battery combination is used. This massive servo can handle the pounding it gets and can operate on a wide range of voltage (up to 8.4v). The retail price has recently dropped from $200 to $170 each.

This servo combination uses about 1700mAh per hour of operation. A typical tow session runs about 50 minutes, so two sessions use about 2,800mAh (just over 50% of battery capacity). At this point, I either recharge or replace with fresh packs.

A123 batteries are not for everyone. For one thing, there is no good way to accurately judge the amount of charge remaining in a pack. Secondly, maximum pack size is limited to 2,500mAh. On the plus side, they are very durable, charge up fast, last through many, many charge cycles, are not near as much of a fire hazard as LiPo batteries, and are not extremely temperature sensitive like LiPo batteries.

Hope this helps,
Jim

**Stew2** · 10-26-2017, 12:07 PM

Not to diverge, but..... Jim, do you think that the mAh "counters" via Spektrum telemetry, Powerbox or the new Spektrum receivers which include it, are valid for monitoring A123 applications? I would think so, as the classical method for this has been collecting data of how much you put in at charge and deciding on your choice of "refill" level. Fully understand that there is no good way to determine what is left by a voltage reading, but mAh put in or monitored going out I would think are good ways to know A123 status.

**JimD** · 10-26-2017, 12:30 PM

Hi Scot, the telemetry data may be the answer for this. My strategy is to run a timer on the transmitter that keeps a log of run time. When it reaches 100 minutes I either charge the batteries in the plane or replace the packs with freshly charged packs. I then monitor the amount of mAh put back into the packs. If something seems amiss, then need to look for a problem like a binding function or questionable battery pack. So far, neither of these things have happened, charge mAh have been right in line with run time.

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Bidule 170 Servo Recommendations

Bidule 170 Servo Recommendations

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