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Old 02-13-2017, 07:35 PM   #1
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Default Servo Horn Offset, Does it Matter?

Did a search here but couldnt really find any discussion on this topic, but does the offset of the servo horn have any effect on handling?

I use servo horns that sticks out from the servo a lot (offset)


and ones thats almost flush with the servo body (no offset)


and I dont feel like theres significant effect on handling. But I just wanna see if you guys have any insight on different types of servo horns
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Old 02-14-2017, 08:43 AM   #2
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You should always refer to the user manual of your vehicle to determine the best way to install/adjust the servo so that it has the proper relation/linkage angles to the steering mechanism. Failure to do so could result in the following issues...
- More mechanical steering to one side vs the other
- Unwanted bump steer (on vehicles where the servo horn connects directly to the steering knuckles)
- Too much or too little ackerman (on vehicles where the servo horn connects directly to the steering knuckles)
- Binding on the servo horn, which can affect servo performance

Some manufacturers give basic instructions on where exactly a servo needs to be mounted, the angle of degrees the servo horn should be installed when the servo is centered, and how far away the servo horn ball stud(s) should be off the chassis. Unfortunately with so many choices of servos, it is up to the individual to make sure they mount their servo in the correct location.

Sometimes you have to shim a servo forward or back on the chassis to achieve the proper angle between the horn and the steering mechanism/knuckles. In some cases it may not be possible to shim the servo enough, so you can use different servo horns (see post above). You can also use longer/shorter balls studs as well as using shims on the ball studs to get the proper steering geometry.

One more quick thought...

If the servo horn arm is very close to the servo, then it can be possible in some circumstances for threaded part of the ball stud to come into contact with the servo case. This is more of an issue when a person might use a nut secure the ball stud to the back of the servo arm. It is something to consider when selecting a servo horn.
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Personally I like to take the extra time to make sure the servo is mounted as optimally as possible so the mechanical steering is equal side to side. Some people will just use their radio to adjust the mechanical throw, but I don't like "the feel" of my cars when I adjust them this way.
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Last edited by IndyRC_Racer; 02-14-2017 at 10:43 AM. Reason: clarity/grammar
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Old 02-14-2017, 09:20 AM   #3
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Here is a good example from the XRAY T3 '12 manual that shows the proper angles for setting up the servo on that car. From looking at the illustrations, you should be able to determine the steering link turnbuckle angle from the servo to the steering mechanism. Note that XRAY included shims with their kit to adjust the servo.

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Old 02-15-2017, 07:22 PM   #4
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Yeah, some cars require a certain distance, my car's manual did not specify the exact location of where the servo should be mounted. It just said "add shims to move servo back IN CASE YOU WANT TO MOVE IT BACK" so I guess it really depends how the driver and how they setup the car then...

I switched out the servo and needed a different servo horn cuz of the different splines and I didnt have the same offset servo horn so I just grabbed whatever I have available at the track. I did not feel any difference between having an offset servo horn and no offset. I just adjusted the steering throw on the radio the car drove the same as before
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