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Old 09-23-2011, 06:40 PM   #3931
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Im wondering what the physics are behind a gear diff being faster in blinky 17.5?

As long as the ball diff isnt slipping and if you are setting up the gear diff so that it has similar differential action to the ball diff, why would the gear diff allow you to get on the throttle harder/sooner?

I thought the main benefits of the gear diff were ease of maintenance? And lack thereof, compared to a ball differential? And perhaps robustness compared to a ball diff when used in conjunction with mod motors?

I mean, a differential is a pretty simple device all things considered... so where does the difference come from? Not doubting, just wondering...
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Old 09-23-2011, 06:41 PM   #3932
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I"m trying to duplicate a setup posted on the RSD thread and it calls for the steering Bellcrank to be set at 7C and the link to be set to 1B, however when I try to do this the top of the servo saver hits the bulkhead and top deck. So am I missing something or is this not possible. It is not listed in the manual but with the problems that book has, it's possible something was left out. Thanks for the help in advance.
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Old 09-23-2011, 10:38 PM   #3933
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I"m trying to duplicate a setup posted on the RSD thread and it calls for the steering Bellcrank to be set at 7C and the link to be set to 1B, however when I try to do this the top of the servo saver hits the bulkhead and top deck. So am I missing something or is this not possible. It is not listed in the manual but with the problems that book has, it's possible something was left out. Thanks for the help in advance.
When using the forward bellcrank position you need to clearance the top deck and the boss on the bellcrank to attain full throw. Unfortunately it's just a matter of trial and error using something like an xacto or a fine cutting bit with a dremel to remove as little material as possible.

I would recommend on focusing on the bellcrank boss and once you've taken that down then make any remaining clearances on the underside of the top deck right next to the bulkhead.

Hope this helps!
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Old 09-23-2011, 11:27 PM   #3934
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Originally Posted by JamesL_71 View Post
Im wondering what the physics are behind a gear diff being faster in blinky 17.5?

As long as the ball diff isnt slipping and if you are setting up the gear diff so that it has similar differential action to the ball diff, why would the gear diff allow you to get on the throttle harder/sooner?

I thought the main benefits of the gear diff were ease of maintenance? And lack thereof, compared to a ball differential? And perhaps robustness compared to a ball diff when used in conjunction with mod motors?

I mean, a differential is a pretty simple device all things considered... so where does the difference come from? Not doubting, just wondering...
Even if the ball diff is set-up tight, there will be a bit of slippage under acceleration, given that the track has sufficient traction. A gear diff is fully locked under acceleration, which a ball diff is not. If you were to lock it enough to not really slip, the differential action would not be as smooth causing an on power push, or even erratic behavior. This is where the gear differential is beneficial, you can adjust your diff characteristics by changing fluid, and still having locked, on-power drive.

For example, if you wanted more turn in, you run lighter rear diff fluid. In a straight line your diff still is locked. If you were to set your ball diff looser to get this turn in, under acceleration, you would induce slippage. Does it make sense?
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Old 09-24-2011, 01:31 AM   #3935
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hi olly but i already have 3 mm shims on the rear mount on the rear of the car when i put the car together by the setup sheets so how do i get the 2.5 toe total i hope u understand this
Put a 0.5 shim behind front block of rear arms or remove 3mm and use 0.5 and 2 shim instead
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Old 09-24-2011, 02:31 AM   #3936
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When I once did a test day on my home medium-high grip indoor track comparing the AE ball diff and the Spec-R gear diff with 17,5t blinky it just brought 0,02s. I ran it with 1000cst and AE 60wt. There was nothing with 1-2 tenth gain. The AE ball diff is very good and a 17,5t cannot slip it much. At least when using SPXzero, X12 and VTEC CPX tires. That is my experience. Maybe you loose the benefit because of the extra rotational weight. The Spec-R feels pretty heavy.
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Old 09-24-2011, 09:16 AM   #3937
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Even if the ball diff is set-up tight, there will be a bit of slippage under acceleration, given that the track has sufficient traction. A gear diff is fully locked under acceleration, which a ball diff is not. If you were to lock it enough to not really slip, the differential action would not be as smooth causing an on power push, or even erratic behavior. This is where the gear differential is beneficial, you can adjust your diff characteristics by changing fluid, and still having locked, on-power drive.

For example, if you wanted more turn in, you run lighter rear diff fluid. In a straight line your diff still is locked. If you were to set your ball diff looser to get this turn in, under acceleration, you would induce slippage. Does it make sense?
It makes perfect sense if the AE ball diff is indeed slipping... Is this a known problem/issue? Or is it just a consequence of the design of this type of ball differential(ie: diff with a single adjustment for action and slip)?

Back 10-15 yrs ago, I used to race 1/10th 235mm gas on-road(BMT, Serpent Impact, Picco Integra, etc). The ball diffs we used had adjustments for both the slip and actual differential action. So you could adjust the diff quite loose without inducing any slip. Granted, the diffs were rather large and heavy.... but they were works of art when you assembled and set them correctly.
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Old 09-24-2011, 09:23 AM   #3938
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It makes perfect sense if the AE ball diff is indeed slipping... Is this a known problem/issue? Or is it just a consequence of the design of this type of ball differential(ie: diff with a single adjustment for action and slip)?

Back 10-15 yrs ago, I used to race 1/10th 235mm gas on-road(BMT, Serpent Impact, Picco Integra, etc). The ball diffs we used had adjustments for both the slip and actual differential action. So you could adjust the diff quite loose without inducing any slip. Granted, the diffs were rather large and heavy.... but they were works of art when you assembled and set them correctly.
All ball diffs are the same, not an AE problem, but nothing wrong with the original diff, except more maintenance and wear of pads and balls.
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Old 09-24-2011, 09:49 AM   #3939
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Put a 0.5 shim behind front block of rear arms or remove 3mm and use 0.5 and 2 shim instead
thanks olly i got what u mean but when i set my car by the setup sheet and put my rear a=arm mounts on i put the the setting and the setup sheet says and now wont it change the setting of the a-arm is ment to be on the settings.
plus i dont have 0.5 shims what do i use
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Old 09-24-2011, 10:08 AM   #3940
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thanks olly i got what u mean but when i set my car by the setup sheet and put my rear a=arm mounts on i put the the setting and the setup sheet says and now wont it change the setting of the a-arm is ment to be on the settings.
plus i dont have 0.5 shims what do i use
Sorry mate, lost in translation here!

Sorry, there is No: 1, 1.5 and 2 in spacers, so fit a 1+1.5 to get to 2.5
You can also change the outer hubs to get out toe setting, but I have never use them.

You should have shims on front too No2 on 4 mounts.
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Old 09-24-2011, 10:25 AM   #3941
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Originally Posted by JamesL_71 View Post
Im wondering what the physics are behind a gear diff being faster in blinky 17.5?

As long as the ball diff isnt slipping and if you are setting up the gear diff so that it has similar differential action to the ball diff, why would the gear diff allow you to get on the throttle harder/sooner?

I thought the main benefits of the gear diff were ease of maintenance? And lack thereof, compared to a ball differential? And perhaps robustness compared to a ball diff when used in conjunction with mod motors?

I mean, a differential is a pretty simple device all things considered... so where does the difference come from? Not doubting, just wondering...
On-throttle I can dial as much steering as I want playing with different fluids. Also, when I was lifting or letting the throttle back to neutral the car would nearly 180, so when I got the setup right I could out-rotate any other car without sliding. It took me a few heats to get used to, but I don't plan on going back.

I don't remember using brakes at all last night, either, even in the very tight turns.
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Old 09-24-2011, 10:29 AM   #3942
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Sorry mate, lost in translation here!

Sorry, there is No: 1, 1.5 and 2 in spacers, so fit a 1+1.5 to get to 2.5
You can also change the outer hubs to get out toe setting, but I have never use them.

You should have shims on front too No2 on 4 mounts.
ok i will do that but on the rear a-arm at the front a-arm i have a 2mm anda 3mm on the rear so do i put no shims on the front a-arm on the rear a-arm and a 2.5 on the rear to give it 2.5 toe.

what do u mean on the front i should have no2 on 4 mounts sorry olly for making u go crazy
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Old 09-24-2011, 10:56 AM   #3943
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ok i will do that but on the rear a-arm at the front a-arm i have a 2mm anda 3mm on the rear so do i put no shims on the front a-arm on the rear a-arm and a 2.5 on the rear to give it 2.5 toe.

what do u mean on the front i should have no2 on 4 mounts sorry olly for making u go crazy
I am talking about the front suspension setup

For the rear, use 2.5 at rear and zero on front of A arms.

Do you have the manual for this car?
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Old 09-24-2011, 11:07 AM   #3944
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I am talking about the front suspension setup

For the rear, use 2.5 at rear and zero on front of A arms.

Do you have the manual for this car?
ok yes i have the manual for the car but i working off one of the setup sheets i have so im setting the car like that and it says for the rear a-arm to use a 2mm on the front and a 3mm shim on the rear a-arm but i was thinking how do they get a 2.5 toe on the rear ifthere setting r wrong.
olly thanks for u help mate
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Old 09-24-2011, 11:08 AM   #3945
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I am talking about the front suspension setup

For the rear, use 2.5 at rear and zero on front of A arms.

Do you have the manual for this car?
ok yes i have the manual for the car but i working off one of the setup sheets i have so im setting the car like that and it says for the rear a-arm to use a 2mm on the front and a 3mm shim on the rear a-arm but i was thinking how do they get a 2.5 toe on the rear if there setting r wrong.
olly thanks for u help mate
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