hanzo

WR-02CB straight steering

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I am trying to get my WR-02CB to drive in a straight line.

Well…as much as possible with this chassis.:unsure:

The trim/servo saver has been centered and both tie rods set to 35mm (slightly toe out) as per manual.

In addition, for the front the following hop-ups have been installed:

  • Tamiya 50473 - Hi-Torque Servo Saver
  • Tamiya 54587 - Aluminum Servo Stay (WR-02,GF-01)
  • Tamiya 54661 - Aluminum Hub Carrier (8 Degree) (GF-01, WR-02)

I’m looking to adjust the tie rods so the front wheels either be straight or even slightly toe in.

Been reading various threads on TamiyaClub and there was mention the following might help:

  • Tamiya 54610 - OP.1610 Clamp Type Aluminum Wheel Hub

Will this take the slight wobble out of the front wheels?

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Hi there. I have a Comical Hornet and i know where you are coming from. It important to have the servo saver dead centre so you get even steering left to right, but that means as you rightly say, you need to even out any tolerances in the kit with different length steering arms. The car is quite wandery because the round front tyre profile makes it prone to moving around. Toe in is definitely the way forward. I took the wobble out of the wheels using 5x7 schumacher speed pack shims. They are 0.4mm thick and i ended up using 2 or 3 per wheel mounted behind the pin on the axle to get the hex to tighten down nicely whilst still running freely on the bearings. Another little trick is getting an angle measuring app on you phone and usibg that on a flat surface to measure the toe in on each wheel. Try getting it to 1 deg on both sides. If you want to make this adjustmemt super easy try getting some turnbuckles the same length as the steering rods. Another extension of this same issue is that i found the steering really touchy and over responsive just off centre. Again those rounded tyres just make it dive into turns super sharp. I have my dual rate on my transmitter at 100% non-linear and my end points dialed back to around 70%. Its worth playing with. 

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Thank you for the response and tip regarding using the 5x7 Schumacher Speed pack (0.4mm) shims.

I had a look on the Tamiya Japan website under WR-02CB chassis and they list Tamiya 54573 0.75mm Wheel Spacer (Blue/8 Pcs.) which is probably very similar.  I might give that a go.

The item I suggested Tamiya 54610 OP.1610 Clamp Type Aluminium Wheel Hub is not listed as compatible with WR-02CB (only WR-02).

I’ll definitely adjust toe in first and will hunt for an app (good idea!) to measure the toe in angle.

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17 minutes ago, hanzo said:

Thank you for the response and tip regarding using the 5x7 Schumacher Speed pack (0.4mm) shims.

I had a look on the Tamiya Japan website under WR-02CB chassis and they list Tamiya 54573 0.75mm Wheel Spacer (Blue/8 Pcs.) which is probably very similar.  I might give that a go.

The item I suggested Tamiya 54610 OP.1610 Clamp Type Aluminium Wheel Hub is not listed as compatible with WR-02CB (only WR-02).

I’ll definitely adjust toe in first and will hunt for an app (good idea!) to measure the toe in angle.

No sure those wheel shims will work as they are 4mm internal so they won't fit the pin section of the axle. You need 5mm shims to fit behind the pin. 

Those 10mm wide hexes don't fit the CB because the axles are too short. However, if you want wider track to use those 10mm wide hexes then you can get the 50808 TG10 Long axles to swap with your standard axles. That would make it work. 

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The manual says toe-out? Really? That's weird... toe-out on the front wheels of a short RWD vehicle will definitely be twitchy and unstable. Before you start swapping parts around, try adjusting it to about 2 degrees of toe-in in the front, and see where that gets you.

Also, those hub carriers... Is that 8 degrees of caster? That should help stability, as long as you have them installed in the right direction... negative caster is always a no-no.

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14 hours ago, ThunderDragonCy said:

No sure those wheel shims will work as they are 4mm internal so they won't fit the pin section of the axle. You need 5mm shims to fit behind the pin. 

Those 10mm wide hexes don't fit the CB because the axles are too short. However, if you want wider track to use those 10mm wide hexes then you can get the 50808 TG10 Long axles to swap with your standard axles. That would make it work. 

I'll give the 4mm a shot (Tamiya 54573 0.75mm Wheel Spacer) and report back later.  

It will work out cheaper than purchasing the 10mm hexes (Tamiya 5461) and the Tamiya 50808 TG10 Long Axles (good tip BTW!).

3 hours ago, markbt73 said:

The manual says toe-out? Really? That's weird... toe-out on the front wheels of a short RWD vehicle will definitely be twitchy and unstable. Before you start swapping parts around, try adjusting it to about 2 degrees of toe-in in the front, and see where that gets you.

Also, those hub carriers... Is that 8 degrees of caster? That should help stability, as long as you have them installed in the right direction... negative caster is always a no-no.

The manual did state toe-out but it looked toe out to me after I assembled everything.  Will definitely change to toe-in this weekend and take the car for a run. 

Come to think of it - I did install the Tamiya 50473 - Hi-Torque Servo Saver and the length was slightly shorter than the once included in the kit.  Maybe the stock tie-rod lengths of 35mm needed to be adjusted because of this.

Yes, the hub carriers have 8 degrees of caster and are installed correctly - they lean forward slightly (will double check - but the way it was designed it was hard to install incorrectly).

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6 minutes ago, hanzo said:

The manual did state toe-out but it looked toe out to me after I assembled everything.

Typo: The manual did not state toe-out but it looked toe-out to me after I assembled everything.

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Setting up to remove slop is most ideal of course in getting the car to track straight. Any additional tracking problems from play in the front end should even out with toe in. The wheel will naturally try to track straight, this means that any shimmy that is left in the steering would hopefully be taken out as you are essentially preloading the linkage when you add toe.

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2 hours ago, hanzo said:

I'll give the 4mm a shot (Tamiya 54573 0.75mm Wheel Spacer) and report back later.  

It will work out cheaper than purchasing the 10mm hexes (Tamiya 5461) and the Tamiya 50808 TG10 Long Axles (good tip BTW!).

The manual did state toe-out but it looked toe out to me after I assembled everything.  Will definitely change to toe-in this weekend and take the car for a run. 

Come to think of it - I did install the Tamiya 50473 - Hi-Torque Servo Saver and the length was slightly shorter than the once included in the kit.  Maybe the stock tie-rod lengths of 35mm needed to be adjusted because of this.

Yes, the hub carriers have 8 degrees of caster and are installed correctly - they lean forward slightly (will double check - but the way it was designed it was hard to install incorrectly).

Positive caster should have the  kingpins leaning back at the top - not forward. Having the kingpins lean forward will make it very unstable. Can you post some photos, and maybe I can help?

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3 hours ago, hanzo said:

Come to think of it - I did install the Tamiya 50473 - Hi-Torque Servo Saver and the length was slightly shorter than the once included in the kit.  Maybe the stock tie-rod lengths of 35mm needed to be adjusted because of this.

Yes, the hub carriers have 8 degrees of caster and are installed correctly - they lean forward slightly (will double check - but the way it was designed it was hard to install incorrectly).

Using the Hi-Torque Servo Saver indeed slightly changes the geometry of the tie-rods, so it's not unlikely that the tie-rod length needs to be adjusted.

Also, using the 8° hub carriers influences the tie-rod geometry aswell.  If mounted correctly (positive caster as described by Mark above), they will position the ballends of the uprights slightly lower than stock (and thus further away from the ballend on the servo saver), necessitating increasing the length of the tie-rods slightly.

Also, as the WR-02 chassis isn't totally free of bumpsteer, ride height also influences toe-angles, so you will need to adjust the tie-rods to the best compromise based on ride height too.

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6 hours ago, geniusanthony said:

Setting up to remove slop is most ideal of course in getting the car to track straight. Any additional tracking problems from play in the front end should even out with toe in. The wheel will naturally try to track straight, this means that any shimmy that is left in the steering would hopefully be taken out as you are essentially preloading the linkage when you add toe.

Good point as in 1:1 scale.  Cars naturally track straight in real life. I will tighten the wobbly front wheels more with spacers as ThunderDragonCy suggested.

4 hours ago, markbt73 said:

Positive caster should have the  kingpins leaning back at the top - not forward. Having the kingpins lean forward will make it very unstable. Can you post some photos, and maybe I can help?

I re-checked and indeed it does lean back slightly.

IMG_8423.thumb.jpg.0f273b4caec5be9bfcc7de160c790515.jpg

2 hours ago, Mokei Kagaku said:

Using the Hi-Torque Servo Saver indeed slightly changes the geometry of the tie-rods, so it's not unlikely that the tie-rod length needs to be adjusted.

Also, using the 8° hub carriers influences the tie-rod geometry aswell.  If mounted correctly (positive caster as described by Mark above), they will position the ballends of the uprights slightly lower than stock (and thus further away from the ballend on the servo saver), necessitating increasing the length of the tie-rods slightly.

Also, as the WR-02 chassis isn't totally free of bumpsteer, ride height also influences toe-angles, so you will need to adjust the tie-rods to the best compromise based on ride height too.

Thank you for confirming what I was suspecting.  I have extended the tie rods to 40mm.

Initial testing in the house driving down the corridor, straight line seems to have improved a bit...

I will take the car out this weekend for a run on the tarmac.  Also order some spacers and continue tweaking. 

Really appreciate all the input fellas! :-)

 

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I actually find that some amount of slop/flex in the steering is required to track perfectly straight without having to constantly re-trim the steering servo. This is because no matter how good your steering servo and servo saver are, they will never return to exactly perfectly centred after performing a turn. The trick seems to be to make sure that the slop is only in the steering axis (toe). Slop that can cause significant changes to caster, camber, offset, or shift the entire wheel forwards and backwards in the chassis, seems to hurt stability. The rear wheels obviously should not have any slop in the toe axis. A little slop/flex in the steering, when combined with positive caster will allow the wheels to self centre even if the servo/servo-saver are doing their best to steer slightly off centre. More caster = more straight line stability. After removing unwanted slop from all four wheels, it's the single most important thing to tweak for straight line stability on a flat road. Note that increasing positive caster increases oversteer when turning due to jacking forces which unload one of the rear wheels - when you turn the wheels with a lot of caster one wheel literally gets lifted up and the other forced into the road, which changes the weight distribution across all four wheels.

I'm not familiar with the WR chassis but on the other tamiya chassis I've used the bump steer was far from optimised. As far as I know, in a double wish bone suspension you want the the tie rod to be as close as possible to the geometry of either the upper or lower arm to minimise bump steer. Looks like they are drooping down on an angle with respect to the wishbones in the above picture - that will probably give more bump steer than if they are parallel with the wishbones. Are the tie rod ball ends supposed to be on the top side of your knuckles? You can space the ball joints up/down as required to improve the bump steer with washers, or if they need to be spaced a lot I use brass standoffs (below photo). If you increase caster, you will need to space the ball higher off the knuckle end to correct bump steer.

ejrCWgg.jpg

Note the tie rod and upper wishbone/arm being parallel. 

Personally I've never noticed any improvement in straight line stability by toeing in the front. Slight toe out produces sharper corner turn in so I usually adjust the front to either 0 toe or slightly toe out. Toeing in the rear wheels produces a noticeable improvement in straight line stability on my cars - just don't go too crazy (>3deg) with it or you'll scrub speed and wear out tyres.

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8 hours ago, nbTMM said:

 Are the tie rod ball ends supposed to be on the top side of your knuckles? You can space the ball joints up/down as required to improve the bump steer with washers, or if they need to be spaced a lot I use brass standoffs (below photo). If you increase caster, you will need to space the ball higher off the knuckle end to correct bump steer.

Thank you for pointing out the toe rod ball ends. Indeed they should be on the top side. 

Also the additional information which I think is valuable when setting up any car no matter what chassis. 🙏

Below is a pic before I installed the the Aluminium Hub Carrier.

screenshot_441.png.cb0fbf0fcd23dd612ff711051e79875d.png

I must have installed them incorrectly after I installed the Aluminum Hub Carrier Hop-up.  I have no idea why I didnt pick this up earlier!

As wolfdogstinkus mentioned in another thread could be my ageing. :-)

I'm going to correct this first, check rod-tie lengths before taking the car out for a run later.

btw I also have Tamiya 53345 - Toe-In Rear Upright installed at the rear.

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