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TT02 steering issues

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Having run the Yaris a few times I've noticed the steering doesn't centre very well and sometimes not at all, I've loosened everything up today as much as possible but still showing the same issue, I can hear the servo running trying to centre it.

It's the standard servo that came with the controller a Carson CS3 which looks to be around 3 - 5kg/cm, I'm wondering if it's worth upgrading it or looking further into the steering linkages, I can't feel anything binding when I remove the servo, any suggestions for something around the £15 point! 

In theory should this be powerful enough to centre it?

 This was supposed to be a cheapish hobby for my son and I to have some fun together and turning out anything but!

Thanks

Nick

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Hearing the servo trying to center it?  That does not sound good.  When it is resting, it shouldn't be making noises.  It could be bad actuator.  But first things first...

[1]  Toed out properly?  

[2]  I assume servo horn is mounted near the center? 

[3]  Is the servo smooth?  

[4]  Is there any slop?  

Toe-out helps with going straight. You can do toe-in also. (Depending on whether or not you drive straight more or steer more)  This can be done by lengthening or shortening the tie rods that's connected to the wheels.  

I would assume that the servo horn is mounted at the center?  It's something experienced builders do all the time, but I'd throw this in.  Just trim the steering servo to the center, at the transmitter.  Unscrew the servo horn, and then attach the servo horn at near the center.  It's usually not dead center, but one spline difference can be easily remedied with trim.   

3kg should be plenty for on-road chassis.  But there are servos that's not entirely smooth. Instead of moving smoothly in 60 degree arc, it would move in jerky steps.  It's rare to find bad servos like that, but it's possible.  At least it's easy enough to check.  Just power up and move the servo to see if it moves smoothly. 

As mentioned, a servo at rest shouldn't be making noises.  If it does, the thing that's limiting the movement (I think it's called actuator?) is not working properly.  If that's the case, the servo should be replaced.  Good thing is servos are cheap these days, like $10 USD.  

If all above checks out but the linkages have a lot of slop, you might want to spend some money to upgrade steering linkages.  There are several companies making aluminum linkage sets for $20-$30.  They are not entirely slop-free either, but at least they should be better.  Qualities vary.  

 

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@Juggular Thanks for the top tips, I'm going to have the servo out Sunday and check it's centred properly, I think there is a small amount of binding from one of tie rods as well, so will have a check over on them.

I've also ordered a 20kg servo from Banggood, not sure how good it will be but it's worth a try to see how it works and gives me a spare as well for the next kit we get, I'll also look at upgrading the steering to an aluminium set at some point as it seems pretty sloppy as well.

Many thanks

Nick

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On 10/29/2020 at 8:39 PM, Juggular said:

Toe-out helps with going straight. 

I'm pretty sure it's toe-in that helps with going straight. This is why many touring cars come with some toe-in at the rear for straight-line stability.

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5 hours ago, DeadMeat666 said:

I'm pretty sure it's toe-in that helps with going straight. This is why many touring cars come with some toe-in at the rear for straight-line stability.

That is 100% true.  Toe-in is best for going straight. Better than toe-out.  So if the car is used for straight-line speed records, I would definitely go with toe-in.  For real 1:1 cars too, highway safety is the most important aspect, because most people drive fastest on straight lines, not when they are cornering. So they are toed in.  

But toe-in tends to be terrible at turning. That's not good for on-road cars, so Tamiya instructions mostly ask for toe-out or at least start out from toe-out.  It's not as good as toe-in when it comes to straight running.  But still, toe-out (Ackerman steering?) is a lot better than complete parallel. It is a good compromise between straight running and turning. For racing, backyard bashing, etc.   

Either could be used depending on one's driving style.  If you do good on a straight line, but always react slower or understeer at corners, toe-out would help you.  If you could turn fine, but have trouble at a straight section, toe-in could help.  

mCPi4oW.jpg

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I had a similar problem in the FF04, assumed it was the cheapie servo. Turns out it was user error - I must've fitted the servo loosely when setting it up and never tightened it...different servo arrangement to the TT02, but a loose servo or servo horn could do it.

Isn't it toe in on the rear and toe out in front? Thats how all my cars are set up, and thats what most kit setups will start with. 

 

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9 hours ago, Jonathon Gillham said:

Isn't it toe in on the rear and toe out in front? Thats how all my cars are set up, and thats what most kit setups will start with. 

Exactly as Jonathon says.  

O1u6ND4.jpg

If you cut out the diagram, the front is flared out for toe-out.  The rear end also flares out like an hour-glass (for toe-in because the car is going forward---it would be toe-out too, if it were going backwards)  

 MqreiQE.jpg

 

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Toe-Out in front is for AWD and FWD Cars only... 

Reason being that with the natural play that's in a front Suspension (even in 1:1 Cars), when you're DRIVING the Front Axle, Torque Forces tend to pull the Tires Forward - TOWARDS a Toe-In configuration.... 

Setting a small amount of Toe-Out in a Quality Kit (or fitted with Premium Aluminum Steering Components), will pull the Front Wheels towards a Neutral to slight Toe-In. Optimal for good Handling. 

"Less quality" Kits need more Toe-Out to achieve the same effect.

NON DRIVEN AXLES (RWD mainly), need a degree of Toe-IN set in the Alignment. This is because Drag and natural Friction Forces tend to want to pull the Wheels BACK - towards a Neutral to slight Toe-Out...  Again, Optimal for good Handling! 😉

Nothing in any Assembly Manuals seem to explain this, so I thought I would. I Raced RC in the 80's and 90's, and also Built and Raced 1:1 Cars. I've talked to several People who know way more than I ever will over the years! 😊

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On 11/1/2020 at 9:31 PM, DeadMeat666 said:

I'm pretty sure it's toe-in that helps with going straight. This is why many touring cars come with some toe-in at the rear for straight-line stability.

It's definitely toe in that helps straight line driving.  Toe out helps cornering but makes it more difficult to drive straight

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Camber also makes a difference.  Grasshopper/hornet has very positive camber.  Positive camber and toe-in seem to exaggerate each other.  Long ago, I tried toe-out on my Grasshopper, but it turned camber into severe negative.  It was not drivable.  So for Grassho  

I'm thinking slight negative camber preferred by racers would also make the difference, along with FWD, AWD, and RWD.  But it seems more complicated than my brain could handle.  Give me a decade, I'm sure I'll learn enough eventually... 

But as for Tamiya instructions, M05 asks for toe-out.  

KwKwwfk.jpg

M06 didn't specify, but I built it exactly as the instruction asks for, I think it was slight toe-out.  

Below is for M-07.  As Jonathon said, front is toe-out, the rear is toed-in between 2 to 3.2 degrees.  

JuSyzqC.jpg

Stiff diff grease could also make the car go oversteer/understeer.  Accelerating/decelerating could change over/understeer.

Generally, though, if the car understeers, toe-out could help.  If the car oversteers, toe-in could dull the response.  

Toe-in is definitely superior in straight running. But it's rare that any vehicle would only run straight.  

 

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