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A decent cheap shaft drive car touring car. Where did they all go?

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A decent cheap shaft drive car touring car. Where did they all go?

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Old 09-04-2019, 05:09 AM
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Hi.

A link to Awesomatrix website:

Awesomatix USA: A700 Evo

I see that the front differential is placed on a floating support, and this support is fixed to the bulkhead just with 2 screws at the inner side of the car. Right?. Pretty interesting.

I have to check my design to see if I can fit something similar. My idea is to use the same bulkheads front and rear, but problably I will change it.

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Old 09-04-2019, 06:01 AM
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It's not visible in those cad, but differential is not fixed to bulkheads at all. That support is mounted to "top deck" tube, which is mounted only to motor mount (with floating support in the middle of chassis). It's easier to see here:

https://www.thercracer.com/2014/02/awesomatix-evo-aluminium-chassis-build.html?m=0

​​​
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Old 09-04-2019, 06:57 AM
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Originally Posted by Papi View Post
It's not visible in those cad, but differential is not fixed to bulkheads at all. That support is mounted to "top deck" tube, which is mounted only to motor mount (with floating support in the middle of chassis). It's easier to see here:

https://www.thercracer.com/2014/02/awesomatix-evo-aluminium-chassis-build.html?m=0

​​​
For a better understanding, I have just download the cars manual.
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Old 09-06-2019, 01:40 AM
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Letīs assume that the transmission shaft turn is along the X axle and the differential turn is along the Y axle. When the differential gear receive the rotating movement of the shaft gear (turning in X), we can consider that the torque steer moment, is transmitted to the front differential making the Y axle of the differential to turn around the X axle. In other words, the differential Y axle turns on the YZ plane. Right? Or the movement of the front differential have more components?

See the sketch below:


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Old 09-06-2019, 06:17 AM
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Originally Posted by Eotz View Post
Letīs assume that the transmission shaft turn is along the X axle and the differential turn is along the Y axle. When the differential gear receive the rotating movement of the shaft gear (turning in X), we can consider that the torque steer moment, is transmitted to the front differential making the Y axle of the differential to turn around the X axle. In other words, the differential Y axle turns on the YZ plane. Right? Or the movement of the front differential have more components?

See the sketch below:


The differentials aren't involved in the torque steer problem. The main cause is uneven contact pressure on the tyres due to the moment of inertia of the drivetrain and rotor applying an equal and opposite moment on the chassis. The problem was far worse in the brushed motor days as the armature has a much higher moment of inertia than brushless rotors. Tamiya attempted to address it with some of their transverse motor layouts, at the cost of complexity and drivetrain efficiency.
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Old 09-06-2019, 07:00 AM
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Originally Posted by Eotz View Post
Letīs assume that the transmission shaft turn is along the X axle and the differential turn is along the Y axle. When the differential gear receive the rotating movement of the shaft gear (turning in X), we can consider that the torque steer moment, is transmitted to the front differential making the Y axle of the differential to turn around the X axle. In other words, the differential Y axle turns on the YZ plane. Right? Or the movement of the front differential have more components?

See the sketch below:


The "torque steer" is not correct term here. "Torque twist of chassis" is more correct.
FFG eliminates the torque twisting of chassis.


Please check these videos:



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Old 09-06-2019, 08:14 AM
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Originally Posted by gigaplex View Post
The differentials aren't involved in the torque steer problem. The main cause is uneven contact pressure on the tyres due to the moment of inertia of the drivetrain and rotor applying an equal and opposite moment on the chassis. The problem was far worse in the brushed motor days as the armature has a much higher moment of inertia than brushless rotors. Tamiya attempted to address it with some of their transverse motor layouts, at the cost of complexity and drivetrain efficiency.
The problem is the torque of the motor is transmited to the chassis causing torque twisting of chassis. Right?. Awesomatix created this floating system, but as I see at the videos from Oleg (thanks mate), the floating system absorbs all the chassis tweek in general, not only the motors torque twisting. I think that if we manage to dampen the torque in the differential movement, it will not be transmitted to the chassis. At least it will be reduced.
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Old 09-06-2019, 08:50 AM
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Originally Posted by Eotz View Post
The problem is the torque of the motor is transmited to the chassis causing torque twisting of chassis. Right?. Awesomatix created this floating system, but as I see at the videos from Oleg (thanks mate), the floating system absorbs all the chassis tweek in general, not only the motors torque twisting. I think that if we manage to dampen the torque in the differential movement, it will not be transmitted to the chassis. At least it will be reduced.
You are over-thinking it. The Awesomatix system just isolates the twist of the chassis and front gearbox from each other, its actually pretty simple in concept.
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Old 09-06-2019, 09:27 AM
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Originally Posted by DesertRat View Post
You are over-thinking it. The Awesomatix system just isolates the twist of the chassis and front gearbox from each other, its actually pretty simple in concept.
Awesomatix system is great, no doubt about it. What I'm trying to understand is how works exactly the torque chassis twist in order to eliminate or reduce it in the car I'm designing. I don't want simply to copy their system.
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Old 09-06-2019, 10:00 AM
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Originally Posted by Eotz View Post
Awesomatix system is great, no doubt about it. What I'm trying to understand is how works exactly the torque chassis twist in order to eliminate or reduce it in the car I'm designing. I don't want simply to copy their system.

Its quite simple, when the pinion gear in the front gearbox applies a torque to the ring gear, that torque is felt by the chassis. Because the chassis isn't flat anymore, it twists the front suspension relative to the rear, this puts crossweight in the car where the right front and left rear tire have more weight on them than the other two. Add in a little tire slip that we always have, and even when holding the front wheels absolutely straight the car will pull to the side under power.

Last edited by DesertRat; 09-06-2019 at 10:11 AM.
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Old 09-06-2019, 11:41 AM
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Originally Posted by DesertRat View Post
Its quite simple, when the pinion gear in the front gearbox applies a torque to the ring gear, that torque is felt by the chassis. Because the chassis isn't flat anymore, it twists the front suspension relative to the rear, this puts crossweight in the car where the right front and left rear tire have more weight on them than the other two. Add in a little tire slip that we always have, and even when holding the front wheels absolutely straight the car will pull to the side under power.
Exactly. The question I made myself, is how the torque arrive from the shaft to the chassis? As you say, when the pinion of the shaft, gear in the front gearbox, the differential, applies the torque to the ring gear, making the differential turn because the teeths, but also making the differential roll along the X axle (See the sketch I made). That is how the torque is transmitted to the chassis, causing all the negative effects that you describe. From the pinion gear to the differential ring gear, the differential to the bulkhead, and the bulkhead to he chassis. So theoreticalli, damping this X roll at the differential, at least, we can reduce the impact of the torque on the chassis.
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Old 09-06-2019, 04:57 PM
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Originally Posted by Eotz View Post
Exactly. The question I made myself, is how the torque arrive from the shaft to the chassis? As you say, when the pinion of the shaft, gear in the front gearbox, the differential, applies the torque to the ring gear, making the differential turn because the teeths, but also making the differential roll along the X axle (See the sketch I made). That is how the torque is transmitted to the chassis, causing all the negative effects that you describe. From the pinion gear to the differential ring gear, the differential to the bulkhead, and the bulkhead to he chassis. So theoreticalli, damping this X roll at the differential, at least, we can reduce the impact of the torque on the chassis.
The shaft pinion only puts an upwards or downwards force on the diff gear (z axis), it doesn't directly apply a moment to the diff. Since the diff gear is off center, that's what's producing a net moment on the diff. There's also some minimal torque applied to the gearbox via the friction in the bearing holding the pinion shaft.
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Old 09-07-2019, 11:27 AM
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Look up "torque tube" - it's solution of this issue in real cars. It'd be interesting to see that in RC
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Old 09-08-2019, 10:59 AM
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Originally Posted by Papi View Post
Look up "torque tube" - it's solution of this issue in real cars. It'd be interesting to see that in RC
Good idea. I will do.

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