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Weak servo? How to achieve perfect front wheel control? > Weak servo? How to achieve perfect front wheel control?

Weak servo? How to achieve perfect front wheel control?

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Old 09-17-2017, 11:19 PM
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Default Weak servo? How to achieve perfect front wheel control?

On the HPI Sprint 2 I'm finding it extremely hard to keep going on a straight line. It's very hard to follow tight streets.

I did a mod that keeps both front wheels more "together" but I steel have a weird turning on the left or right. For example it starts going a little to the right then I turn left and when I let go it still has a soft direction to the left.

I ordered better ball cups and still waiting for them but do you think this will fix it completely? The stock servo (SF-10W) is alright?
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Old 09-18-2017, 01:06 AM
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Servo centered when installed? Soft/loose servo saver? Just a weak servo to begin with?

Sounds, to me, like the servo isn't centering completely once power is released or isn't holding center when steering is neutral after a turn.

I'd check the servo saver first if you're running one.

Does it fully return to center when wheels are off the ground?

Just coming back after quite a few years away, might be completely off the mark, so take anything I suggest with a grain of salt, but that's where I'd start.
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Old 09-18-2017, 01:40 AM
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How free is your steering? Did you make sure there are nothing binding your steering linkages or steering hubs? If your steering binds this will result in the car not able to run straight. It will always veer left or right to the direction you just turned

Change out the ball cups first and see if that frees up your steering, if not, then I would take the front end completely apart and start cleaning everything making sure it turns smoothly
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Old 09-19-2017, 01:23 AM
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Servo is centered correctly saver is okay. I will do a precision test for the servo, if it returns exactly at the same point, will make it easier to find where the leakage comes from. My ballcups sure leave big spaces, I'm waiting for the new ball caps. So the more expensive servos are only for speed and water resistance?
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Old 09-19-2017, 01:41 AM
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More expensive servos are better built with metal gears, digital motors, cordless or brushless, and have better responds time and torque. They are some what water resistance since their case and output shaft are equipped with o-rings. But that being said, if your steering binds and doesnt run smoothly or your servo saver cocks either to the left or right after you engage it, it doesnt really matter how expensive your servo is, you will still have a centering issue where the car either veers to the left or right

I had this happen to me a few times. The springs in the Xray servo saver arent sliding smoothly and wouldnt fully return to center when you engage it. It will either point left or right depending on which side you engage the saver and my car never ran straight.

Another time on my TC, it was equipped with a steering rail and it wasnt fully broken in, so the steering was kind of stiff. The car would veer left or right and especially troublesome down the straight. The steering freed up after running a few packs through it.
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Old 09-19-2017, 06:19 AM
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Sounds like you have a serious problem (or a few) somewhere. Locate and fix that.

Beyond that, don't sweat it too much. Your car is built with a lot of slop. By the time you go around with a fine tooth comb and get rid of it you would have spent the money to buy a top end kit (which won't be slop free either, just sloppy in a more controlled way).

One thing that will always plague you is that ultimately wherever you have bearings, you will have slop (call it play if you will). That is due to the tolerance built in the bearings themselves as well as mating parts. Similarly for balljoints, shafts, etc.

If there was no slop, the car would probably not move.

The conclusion is, try to cure what you can, learn to live with the rest. The car should be easily driveable and controllable.

Spending millions on the best servo ever still won't take the slop out of it and it will bring minimal if any improvement.

But if you are still curious, I think there are a few high torque high speed servos on the market (check out what off road 1/8 nitro cars use). My guess is the price will be more than the whole car.
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Old 09-19-2017, 08:25 AM
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Your chassis may be tweaked. I would just get another servo also...if you're hard up on spending money get one of this solar servos, fairly cheap.
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Old 10-11-2017, 01:44 PM
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+1 on tweak
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Old 10-11-2017, 01:50 PM
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How smooth is the pavement? While there could be other issues, doesn’t take much to make a touring car struggle to drive in straight line.
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Old 10-11-2017, 03:09 PM
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Originally Posted by Bob Corey View Post
I did a mod that keeps both front wheels more "together" but I steel have a weird turning on the left or right. For example it starts going a little to the right then I turn left and when I let go it still has a soft direction to the left.
I would guess 1) sloppy/weak servo saver and 2) weak servo. Try turning the front wheels with your hand to the left/right while holding the steering wheel straight. If it vibrates (weak servo) or easy to turn (weak servo saver).

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Old 10-12-2017, 04:35 AM
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The specs for that servo do look a bit weak.
If you're running on medium to high grip, or high speed tracks you might want consider upgrading it to a Savox etc.
As others have mentioned I would also check for tweak and anything binding in the steering system.
Any binding will be made even worse by the weak servo.
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