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  1. #1
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    Converting steering to one servo

    Have noticed a couple of posts/replies where this has been suggested, also can see where there potentially could be a problem with the dual servo's (getting out of sink)...Anywho who has done this and what servo did you use and what parts are needed. Would like to have this info just in case.

    Thanks Ed
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  2. #2
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    Quote Originally Posted by Edstoys View Post
    Have noticed a couple of posts/replies where this has been suggested, also can see where there potentially could be a problem with the dual servo's (getting out of sink)...Anywho who has done this and what servo did you use and what parts are needed. Would like to have this info just in case.

    Thanks Ed
    I hope people that respond give a bit more detail in the supporting parts required. There are a lot of servo choices, but then the conversations kinda dry up when it comes to what other parts they purchase.

    I am interested if anybody changes out the bell crank. I have seen several indicate they change to a much heavier servo arm, some going aluminum.

  3. #3
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    Check out this thread. There are several other threads linked in there all that deal with single servos. It really should answer all your questions just a bit of reading.
    http://traxxas.com/forums/showthread...t=single+servo

  4. #4
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    Digging through all of the single servo thread via the link b@3 provided, Pav (pavementsurfer) is the only one that gave enough description to parts.

    Not having torn apart the steering mechanism, I am not sure if this address all the necessary pieces.

    He mentioned a Racers Edge Aluminum Single Arm Futaba Servo Horn, I have found a regular and hard anodized version:


    However via another hop up website, I found this arm as well:


    And I found a bell crank replacement as well:

  5. #5
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    Most any standard size servo will fit. A little reading will get you 3-4 servos that work fine. Hitec and futaba are the most common. You do not need an alum arm but it is prefered. What arm you get depends on the spline of the servo. Stock belcranks are fine.

  6. #6
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    Quote Originally Posted by chapinb View Post
    Most any standard size servo will fit. A little reading will get you 3-4 servos that work fine. Hitec and futaba are the most common. You do not need an alum arm but it is prefered. What arm you get depends on the spline of the servo. Stock belcranks are fine.
    So short of servo choice, the only real upgrade needed is the servo arm to turnbuckle?

  7. #7
    RC Turnbuckle Jr. jamann's Avatar
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    And the horn, I would suggest
    a washer to stiffen the spring some more


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    they have tried

  8. #8
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    So for the image below as I have found through my job many people call things many different things meaning the same thing.

    Blue = servo (duh..lol)
    Red = Servo Horn
    Yellow = Turnbuckle
    Green = ???

    Need to replace the red and green parts and then throw a washer on the servo save to tight it up a tad?



    EDIT: Forgot to give source credit to Pavement Surfer for original picture I mocked up.

  9. #9
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    OK after spending the better part of the last 1.5 hrs reading links upon links about this upgrade, I am left with one big question.

    Is a MM BEC required or not? Or does that depend on the the voltage the servo you pick uses to reach the stall point.
    Endeavoring to persevere !

  10. #10
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    Quote Originally Posted by Edstoys View Post
    OK after spending the better part of the last 1.5 hrs reading links upon links about this upgrade, I am left with one big question.

    Is a MM BEC required or not? Or does that depend on the the voltage the servo you pick uses to reach the stall point.
    I think its the lower output voltage you receive through the receiver versus a constant unmolested higher source of voltage. I believe through the receiver you plan on the lower 6 volts. To get the maximum torque spec, you would need to run a BEC.

  11. #11
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    Anyone interested in this mod, Just got me a HS7950TH for $126.98 including shipping from Servo City. Limited time introductory sale. That's quite a price drop over TH.
    Last edited by Edstoys; 05-04-2012 at 04:05 PM.
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  12. #12
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    Quote Originally Posted by Bearcats View Post
    I think its the lower output voltage you receive through the receiver versus a constant unmolested higher source of voltage. I believe through the receiver you plan on the lower 6 volts. To get the maximum torque spec, you would need to run a BEC.
    Really did not get into the BEC stuff right away was more interested in the servo pick and fitment on first round, but did get the gest of what you just stated about the BEC just not sure if it is required or not.
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  13. #13
    RC Turnbuckle Jr. pavmentsurfer's Avatar
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    BEC is a big source for debate. some say you NEED it to reduce the chance of "brown outs" which occur when a servo draws too many amps from the stock radio system causing the entire system to loose power for a second. Some say you can generally get around this IF your having a problem by installing a capacitor on the BATT plug of the stock RX. I personally run a Futaba S9157 425oz servo with an Airtronics RX on the stock EVX2 ESC and have never had a brown out or any type of glitching and I don't have ANY extra electronics installed at all.

    You DO need to run an external BEC if you buy a high voltage servo. But keep in mind, if you DO run an external BEC you may need to install a separate battery for the BEC itself. I don't know much about this as I don't run one but there is LOTS of info out there including full wiring schematics. You just need to look around.

    As for the steering parts, I have been talking with bearcats recently and heres what we discussed. A Futaba servo requires NOTHING to install in a traxxas truck. The servo output spline is the same with the stock servo and the futaba so you can literally just install it with the stock parts (which is what you see in his picture above. But what you will find is that a super high torque servo stresses and flexes the stock plastic parts quite a bit. Failures on the servo horn are common, most often the splines will strip. So, at least get the aluminum servo horn for the particular brand servo you choose. The little link the middle is fine and as far as I know, there is no upgrade for that part. But you don't need an upgrade there so leave it alone.

    The single steering arm is something alot of people do simply because that plastic arm flexes ALOT with a single high torque servo. If you get into a situation where your wheels are wedged into something and your reefing on the steering that arm is flexing big time and CAN snap. I didnt ever snap mine but I can see how it could easily happen. For $12 you can get the GHracing aluminum arm which eliminates flex AND the chance that it could snap... for $12, its well worth it.

    I paid $80 for my S9157 new, but from a guy on another forum. It was open but unused. I just installed a Hitec 7955 in my E-Revo with the same aluminum parts and I paid $70 for that servo shipped. Its got 333oz of torque and has been fine in my E-Revo but I don't run it in the rocks like I do my summit so I didnt feel I needed a full 400oz of torque. the stock servos produce about 250oz total (both combined) and are "adequate" so anything 300oz or more in a single servo setup will really be enough. But, theres nothing like a bit of excess in the servo department IMO... thats why I went with the Futaba. I JUST got a JR with 4000oz in another truck that I parted out. Im going to put that in my ERBE for a while and see how I like it. But, for now, the Hitec is fine in the Revo and the Futaba is AWESOME in the Summit.

  14. #14
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    Pavment; do to your in put on some the links from above posts and then reference post off of them, etc. Any how do to your in put and other ordered me a HS7950TH which was referred to a couple of times as a direct fit. Oops might have read my notes wrong either or it should work just as well as the FutabaS9157. HS has 3 operating voltage levels.
    Endeavoring to persevere !

  15. #15
    RC Turnbuckle Jr. pavmentsurfer's Avatar
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    The 7950 will work fine. But you'll NEED a new servo arm as the spline is different than traxxas. The futaba will work with the traxxas servo arm if you didnt want to buy an aluminum one up front. BUT... the 7950 will be a great servo in the summit. Its got LOTS of power and everything WILL bolt right into the truck. You'll notice the servo is smaller than the 2075 you take out. The servo itself is a little small for the hole it fits into. This is normal as traxxas servos are all VERY big. If you centre it and do the bolts up even it wont be a problem.

  16. #16
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    Well after all this intellectual Q & A Have a stupid question which is also important.
    Never used Hitec always had Savox if not stock anyway need to know the tooth count on a Hitec HS-7950TH. Have looked all over the place and give every kind of spec on it but the spline info. Don't want to order the wrong Alum servo arm.
    Endeavoring to persevere !

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