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AE B6.2D / B6.2 Thread

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Old 10-30-2020, 02:57 PM   -   Wikipost
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Reference Guides (courtesy of Ray Munday and Roger M.): What is the difference between 2 gears and 4 gears in the gear diff?
Please read these posts by Roger M. Maybe this has been answered but what are the little orings in diff do for tuning?
Please read these posts by Roger M.
Information on the rear axles and the different length dog bones from Roger M.

The 0 (option) and +2 (kit) axles are for using different length driveshafts with the different arm lengths

Kit +2 axles

73mm arms wih 67mm driveshafts
75mm arms with 69mm driveshafts

Option 0 axles

73mm arms with 65mm driveshafts
75mm arms with 67mm driveshafts

Why would you want to change the driveshaft length?
It is essentially to do with the fact that a drive joint will want to run straight under power and the position of that joint (the pin through the CVA joint into the axle).
The further that CVA joint pin is inboard of the lower hub hingepin (assuming you're running fairly typical outer link positions) the more bind you will generate in the suspension as the drive joint tried to straighten under power, this extra binding will 'stiffen' the suspension as it adds load on top of that from the weight transfer on the car.
Conversely the the nearer the CVA joint pin is to lower hub hinge pin the less bind and thus freer suspension movement.

When would you want to change this?

Basically on bumpy tracks, tracks with inconsistent grip or lower grip you want the suspension to be as free to move as possible so that you get the full benefit from the shock and roll centre tuning, also the car feels like it has more grip in the areas where you go on/off/on the gas.
To this end you will be running the longest possible dog bone you can for the arm length, hence why the +2 axles are in the kit.

On smooth super high grip tracks (EOS / CRC carpet for example) running a shorter dogbone will feel like it takes grip away from the rear as you get on power, aiding late corner rotation and reducing the on-power understeer that often plagues tight carpet tracks.
The only time I would run the 0 axles is with 67mm dogbones on 75mm arms and only then when I wish I could get let rear toe than the 1deg minimum we can get from the pills we have (actually I had custom pill made so I can get 0deg rear toe for those types of tracks but ...)

What are the handling differences between the 73 and 75mm arms.
Brief explanation from RogerM (thanks!)

The arm length effects the roll centre and more significantly the roll centre migration as the car rolls in the corners.

Shorter rear arms will encourage more tire loading so more grip as the car rolls, great for lower grip surfaces but on high grip surfaces they can stall the rotation mid corner costing corner speed. They can also make the car feel more reactive which is good when a low grip level makes the car feel less reactive so making it harder to place in technical sections.

Long rear arms the opposite, car will rotate more freely for more corner speed but won't generate as much side-bite so mid/late corner will be reduced. Make the car feel naturally lazier which is great on high grip surfaces as it makes the car easier to drive overall.

So the long Vs short rear arm is just like the flat Vs gullwing front arm, all about the grip level from the surface and how technical the track layout is.




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Old 01-13-2021, 02:17 AM
  #1756  
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Originally Posted by Braxamus View Post
Our track is what I would consider small to med. compared to the Ohio RC Factory, and it's grey carpet, traction is not an issue in any class, and with the build calling for the steel chassis weights, is it actually still an advantage to go with the larger spur to move the motor forward? I race several other faster oval classes and understand the importance of the finial gear ratio and roll out and motor temps. Just trying to get close on the offroad side of it.
Originally Posted by Silverbullet555 View Post
That's a good point about motor location and weight bias. I had not considered that which is not surprising due to my lack of time spent on carpet off-road. When I last raced electric, spur was 100% dictated by final drive ratio.
ah gotcha. Now weíre talking about driver preference and feel. I run on high-bite clay, so take this info for what itís worth. When I ran the motor Ďbackí with the 72 spur, my car pushed more than I liked on quick chicanes or hard 180s. My driving style, and especially in 17.5, Iím not on the brakes much when the wheels are on the ground, so I ran about 15-18% of drag brake to help load the front and get some steering...when I ran a 72. Since moving to 75t spur, Iím running at most 7% drake brake. The car feels more balance on/off throttle, and Iím able to carry more corner speed. I also feel I can slide the rear easier if I need to tighten up my line with a blip of the throttle. Is this feel ALLLLL from motor position? Probably not. Spring weight, shock oil weight and all that affects that too. Motor position was just an easier path for me.

again there is no right or wrong. By no means married to that setup. I could still make my car work with a 72. The recent layouts at OCRC trend to taller gearing for me. If I kept with the 72, I probably be running a 30 or 31t pinion, which I didnít feel like buying.
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Old 01-13-2021, 06:25 AM
  #1757  
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Originally Posted by rendizzle View Post
ah gotcha. Now weíre talking about driver preference and feel. I run on high-bite clay, so take this info for what itís worth. When I ran the motor Ďbackí with the 72 spur, my car pushed more than I liked on quick chicanes or hard 180s. My driving style, and especially in 17.5, Iím not on the brakes much when the wheels are on the ground, so I ran about 15-18% of drag brake to help load the front and get some steering...when I ran a 72. Since moving to 75t spur, Iím running at most 7% drake brake. The car feels more balance on/off throttle, and Iím able to carry more corner speed. I also feel I can slide the rear easier if I need to tighten up my line with a blip of the throttle. Is this feel ALLLLL from motor position? Probably not. Spring weight, shock oil weight and all that affects that too. Motor position was just an easier path for me.

again there is no right or wrong. By no means married to that setup. I could still make my car work with a 72. The recent layouts at OCRC trend to taller gearing for me. If I kept with the 72, I probably be running a 30 or 31t pinion, which I didnít feel like buying.
This is something overlooked by many and I regularly switch between pinion/spur combinations to move the motor around. My standard gearing is 25/78 with a HobbyWing 7.5, I can achieve the same ratio with 23/69 , 24/72 , 26/78 and 27/81. Each of those steps is gives 2mm between the centre of the motor shaft and layshaft, obviously this isn't directly 2mm difference in horizontal motor placement as the layshaft is higher than the motor shaft, in reality it is around 1.6mm.

Consider that moving the battery around is a noticeable change (my LCG CENTRO 3200mAh packs are 152g) and the steps with the standard mount are 4mm, 2mm if you rotate the mount every other adjustment .... you did know the lipo mount was offset didn't you?
Now my HobbyWing V10 G3 motor is about 160g so similar to the LiPo, now those 1.6mm steps actually sound like they could be quite useful for weight distribution.

Also ...

In addition to simply moving the weight around the torque reaction between the motor's rotor mass and the axle mass (wheels, shafts, diff) changes proportionally to the distance between those two masses and also between the rotor and the centre of mass of the off the whole car, this is somewhere in the battery tray / electronics area on a B6 based car depending on the installation used.
When you consider that moving the motor around looks like it might be similar or slightly more significant than moving the battery .... well it is, give it a try.
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Old 01-13-2021, 06:26 AM
  #1758  
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Originally Posted by NitroXray View Post
Anyone running the hard side rails for carpet
I found that it made the car harder to drive, more initial steering and less mid to exit, exactly what you don't want on a smallish tight & technical high grip track with a turbo'd and boosted 6.5. I now always use the standard side rails.
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Old 01-13-2021, 07:24 AM
  #1759  
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I've tried a 81t spur on my mod 2w a few months ago. Its a subtle change and I and a few locals ran it but haven't run it since. I went from 22/78 to 23/81 with a 7.0.

Whats interesting is the Xray 2w (2020 I guess not sure about the rest) uses what I call a super laydown. Its a longer laydown that puts the motor further forward from the diff outdrives, but also it uses a longer chassis than even the +3 chassis.

I think I'm going to try that again next week.

I also run a 75t spur with a larger pinion vs the standard 72t in stock the majority of the time for the same reason.
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Old 01-13-2021, 07:37 AM
  #1760  
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Anyone know the threads, measurements for the battery thumbscrews that hold the battery strap down?

Associated #91729

Would like to pick a standard pack of them from the hardware store as the blue bling isn't a big deal to me.
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Old 01-13-2021, 07:52 AM
  #1761  
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Originally Posted by purplegrape View Post
Anyone know the threads, measurements for the battery thumbscrews that hold the battery strap down?

Associated #91729

Would like to pick a standard pack of them from the hardware store as the blue bling isn't a big deal to me.
They are the same as the other 3mm screws. Take a screw with you and thread it on. I want to say its m3 .5pitch.I bought some set screws at a local ace hardware out of the screw bins but I can't remember what the pitch was of the threads.
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Old 01-13-2021, 09:03 AM
  #1762  
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Originally Posted by RogerM View Post
This is something overlooked by many and I regularly switch between pinion/spur combinations to move the motor around. My standard gearing is 25/78 with a HobbyWing 7.5, I can achieve the same ratio with 23/69 , 24/72 , 26/78 and 27/81. Each of those steps is gives 2mm between the centre of the motor shaft and layshaft, obviously this isn't directly 2mm difference in horizontal motor placement as the layshaft is higher than the motor shaft, in reality it is around 1.6mm.

Consider that moving the battery around is a noticeable change (my LCG CENTRO 3200mAh packs are 152g) and the steps with the standard mount are 4mm, 2mm if you rotate the mount every other adjustment .... you did know the lipo mount was offset didn't you?
Now my HobbyWing V10 G3 motor is about 160g so similar to the LiPo, now those 1.6mm steps actually sound like they could be quite useful for weight distribution.

Also ...

In addition to simply moving the weight around the torque reaction between the motor's rotor mass and the axle mass (wheels, shafts, diff) changes proportionally to the distance between those two masses and also between the rotor and the centre of mass of the off the whole car, this is somewhere in the battery tray / electronics area on a B6 based car depending on the installation used.
When you consider that moving the motor around looks like it might be similar or slightly more significant than moving the battery .... well it is, give it a try.
Great information.

I was not aware the battery strap was offset. I looked at it one day and wondered if it was, but never broke out the ruler to check. Great to know.
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Old 01-13-2021, 11:18 AM
  #1763  
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Originally Posted by Silverbullet555 View Post
Great information.

I was not aware the battery strap was offset. I looked at it one day and wondered if it was, but never broke out the ruler to check. Great to know.
Is this true? How did I never realize this?
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Old 01-13-2021, 11:21 AM
  #1764  
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So Matthew Gonzales ran a 4-gear gear diff with 30k on clay this weekend. His explanation is below:

ďso as I see it, the ball diff was sensitive through the bumps and wasnít rotating smoothly through the turns, instead of changing something like pills or a ball stud washer I thought to myself and thought about the torque a ball diff has when going into a turn, it locks up, which isnít a bad thing, but it means it has direct rear grip, instant traction, which is good for most of the races we attend but this one was higher bite and lots of grip, so I decided to go down the route of running a gear diff as I believes it doesnít catch the bumps, itís constantly spinning so thereís not direct lock or it jerking one way or the other, the gear diff sorta lets you walk your own path on the track giving you free range to drive around the track smooth, or balls to the wall driving on these higher bite bumpy tracks.Ē

Anyone else ever try this? Not only am I surprised he ran a gear diff, but Iím shocked at the weight of oil he ran!
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Old 01-13-2021, 12:02 PM
  #1765  
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Originally Posted by purplegrape View Post
Anyone know the threads, measurements for the battery thumbscrews that hold the battery strap down?

Associated #91729

Would like to pick a standard pack of them from the hardware store as the blue bling isn't a big deal to me.
The threads are M3.
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Old 01-13-2021, 01:26 PM
  #1766  
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Originally Posted by MrLean View Post
Is this true? How did I never realize this?
Glad I wasn't alone.
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Old 01-13-2021, 03:17 PM
  #1767  
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Originally Posted by MrLean View Post
So Matthew Gonzales ran a 4-gear gear diff with 30k on clay this weekend. His explanation is below:

ďso as I see it, the ball diff was sensitive through the bumps and wasnít rotating smoothly through the turns, instead of changing something like pills or a ball stud washer I thought to myself and thought about the torque a ball diff has when going into a turn, it locks up, which isnít a bad thing, but it means it has direct rear grip, instant traction, which is good for most of the races we attend but this one was higher bite and lots of grip, so I decided to go down the route of running a gear diff as I believes it doesnít catch the bumps, itís constantly spinning so thereís not direct lock or it jerking one way or the other, the gear diff sorta lets you walk your own path on the track giving you free range to drive around the track smooth, or balls to the wall driving on these higher bite bumpy tracks.Ē

Anyone else ever try this? Not only am I surprised he ran a gear diff, but Iím shocked at the weight of oil he ran!
Yeah I would have thought of trying it at that weight. I was too busy trying to get my wheeler to feel like not a POS. My B6.2 and T6.2s were money though.
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Old Yesterday, 06:04 AM
  #1768  
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Originally Posted by MrLean View Post
Is this true? How did I never realize this?
Try it, it is most forward with the screw on stops facing forward
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Old Yesterday, 06:36 AM
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Originally Posted by RogerM View Post
Try it, it is most forward with the screw on stops facing forward

I have wondered if this was the case with the battery strap. I tried flipping the strap last night on a carpet track that is starting to fade to get more rear grip. Being able to adjust the battery in small increments like that worked very well. Thanks for the tip Roger
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Old Yesterday, 06:47 AM
  #1770  
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Originally Posted by MrLean View Post
So Matthew Gonzales ran a 4-gear gear diff with 30k on clay this weekend. His explanation is below:

ďso as I see it, the ball diff was sensitive through the bumps and wasnít rotating smoothly through the turns, instead of changing something like pills or a ball stud washer I thought to myself and thought about the torque a ball diff has when going into a turn, it locks up, which isnít a bad thing, but it means it has direct rear grip, instant traction, which is good for most of the races we attend but this one was higher bite and lots of grip, so I decided to go down the route of running a gear diff as I believes it doesnít catch the bumps, itís constantly spinning so thereís not direct lock or it jerking one way or the other, the gear diff sorta lets you walk your own path on the track giving you free range to drive around the track smooth, or balls to the wall driving on these higher bite bumpy tracks.Ē

Anyone else ever try this? Not only am I surprised he ran a gear diff, but Iím shocked at the weight of oil he ran!
To me that makes absolutely no sense at all, my go to on bumpy 'high grip' is a ball diff. Only go to a gear diff if I find that the ball diff is struggling at the tightness I want to run.
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