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Old 12-25-2015, 07:44 PM
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Originally Posted by BobW View Post
When you change the upper shock position the change to droop should be very small. Moving the lower shock mount inward or outward will certainly have more of an effect.

I'm working on shock modelling now which will require more details of the shock geometry and stroke to be included. Shouldn't be to much problem to include something to calculate the shim thickness required to maintain consistent droop. I'll add it to the list.
cool that would be awesome
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Old 12-31-2015, 06:43 AM
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Just uploaded some new models

Touring Cars
Durango DETC410
Sukura XI
Xray T4 '15
Xray T4 '16

Motors & Dyno Runs
Reedy Sonic M3 17.5
TrackStar 17.5

Hope everyone has a safe and Happy New Year.

Last edited by BobW; 01-09-2016 at 05:24 PM.
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Old 01-08-2016, 06:12 AM
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Bob,

Happy New Year to you as well! Thanks for Xray T4 '16 car files, very timely.

T4 has this option to move any of diffs slightly up or down. Housing is slightly eccentric I assume and you can rotate it to either tighten belt or move diff itself up or down. Is there a way to simulate this in your software? And do you know what it does? In handbook it says how it affects handling, but I am wandering - is it just because it shifts weight up or down or it's something more. I can't imagine what else it could affect rather than just weight center.
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Old 01-08-2016, 07:58 AM
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Thanks for the update Bob.
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Old 01-09-2016, 05:23 PM
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Originally Posted by maris View Post
Bob,

Happy New Year to you as well! Thanks for Xray T4 '16 car files, very timely.

T4 has this option to move any of diffs slightly up or down. Housing is slightly eccentric I assume and you can rotate it to either tighten belt or move diff itself up or down. Is there a way to simulate this in your software? And do you know what it does? In handbook it says how it affects handling, but I am wandering - is it just because it shifts weight up or down or it's something more. I can't imagine what else it could affect rather than just weight center.
I have wondered as well how raising/lowering the diffs would affect handling. There would be a slight change in CG height but it would be very small. Could possibly be some gyroscopic effect as the diffs are spinning at high RPM. I'll do some research.

Anyone have an explanation?
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Old 01-09-2016, 05:36 PM
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Originally Posted by BobW View Post
I have wondered as well how raising/lowering the diffs would affect handling. There would be a slight change in CG height but it would be very small. Could possibly be some gyroscopic effect as the diffs are spinning at high RPM. I'll do some research.

Anyone have an explanation?
I know a partial explanation, lol, can't remember all the physics that were explained to me by a mech. engineer and setup guru. It has to do with the angle of the dogbones going into the diff outdrives. Which affects the 'dogbone plunge', or how much the drive pins move in/out as the suspension travels. The more the pins move, the more they 'bind up' when getting on power. This gives more traction and plants that end of the car more. I think that was how it was explained to me, lol.
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Old 01-09-2016, 06:16 PM
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Originally Posted by Stealth_RT View Post
I know a partial explanation, lol, can't remember all the physics that were explained to me by a mech. engineer and setup guru. It has to do with the angle of the dogbones going into the diff outdrives. Which affects the 'dogbone plunge', or how much the drive pins move in/out as the suspension travels. The more the pins move, the more they 'bind up' when getting on power. This gives more traction and plants that end of the car more. I think that was how it was explained to me, lol.
That's my understanding as well, it creates bind and wants to straighten out, causing the rear end to squat naturally, when there is a downward angle to the bones.
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Old 01-10-2016, 03:05 PM
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Interesting explanation.

If there is a big difference in the vertical axle angle I can see the argument for binding. I remember in my NTC3 there was an offset in the fore aft direction between the centreline of the diff and wheel axles. The misalignment was bad enough that the dog bone pin working back and forth would wear a notch in the diff outdrives. When the notch got big enough you got some real binding.

I'll have to try this out sometime. Won't be something I'll be able to quantify in RC3 though.
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Old 01-10-2016, 07:45 PM
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Originally Posted by BobW View Post
Interesting explanation.

If there is a big difference in the vertical axle angle I can see the argument for binding. I remember in my NTC3 there was an offset in the fore aft direction between the centreline of the diff and wheel axles. The misalignment was bad enough that the dog bone pin working back and forth would wear a notch in the diff outdrives. When the notch got big enough you got some real binding.

I'll have to try this out sometime. Won't be something I'll be able to quantify in RC3 though.
Check the angle difference between this and last years BD.
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Old 01-13-2016, 01:22 PM
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This is what Yokomos designer said about the lowering of the Diffs

The front and rear drive pulley was reduced 6 mm and the drive axel was lowered 3mm. This reduces the gyro effect caused by rotating parts when racing (the effect will be less changes direction of the rotation axis), especially due to better movement of the roll direction, sharp crosscutting and cornering become possible. The throttle response is also improved by the weight of the pulley. Acceleration and electric efficiency has also improved during escape at the corner.
So it is gyroscopic effects they are trying to reduce. To reduce the gryo they reduce the diameter of the diff pulleys this also allowed the diffs to be lowered 3mm which helps lower the CG. Yes that changes the angle of the axles but I don't believe it has anything to do with binding. They are doing everything possible to lower the CG, reduce the rotating mass, and minimize gyroscopic effects. That all makes sense to me.

Here is the page link
https://www.teamyokomo.com/product/o...rtc_bd716.html
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Old 01-13-2016, 04:03 PM
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Thanks, Bob. I've heard from others that they are running the differentials up high. Would this generate or reduce chassis roll?
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Old 01-20-2016, 08:46 PM
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Originally Posted by EDWARD2003 View Post
Thanks, Bob. I've heard from others that they are running the differentials up high. Would this generate or reduce chassis roll?
That would increase chassis roll.
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Old 01-21-2016, 11:46 AM
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Originally Posted by BobW View Post
This is what Yokomos designer said about the lowering of the Diffs



So it is gyroscopic effects they are trying to reduce. To reduce the gryo they reduce the diameter of the diff pulleys this also allowed the diffs to be lowered 3mm which helps lower the CG. Yes that changes the angle of the axles but I don't believe it has anything to do with binding. They are doing everything possible to lower the CG, reduce the rotating mass, and minimize gyroscopic effects. That all makes sense to me.

Here is the page link
https://www.teamyokomo.com/product/o...rtc_bd716.html
This is what I have heard as well. The gyroscopic effect has a tendency to bias or load the suspension arms which effects roll center and weight transfer front to rear under acceleration. I also heard that the effects are fairly minimal but it does have an effect. If the Diff is low, it will tend to push the arms downward under rotational load because theoretically, the drive shafts want to straighten. It's like a dynamic spring that lifts the car as RPM increases. This will prove to be difficult to model as the mass, length and diameter of the drive shafts all play a part in it's effect.
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Old 01-21-2016, 11:50 AM
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Originally Posted by BobW View Post
That would increase chassis roll.
Absolutely correct!
If the diffs are high, the driveshafts will tend to bias the arms up or lower the chassis height.
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Old 01-21-2016, 02:12 PM
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In a completely anecdotal way, I have found moving the diffs up or down to be a lot like changing the roll center. Lowering the diffs got the car more "into" the track, raising them freed the car up. This was with the TC5 that had different cams for this purpose.

I may be totally wrong
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