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Old 11-07-2012, 07:58 AM   #151
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http://www.losi.com/Products/Default...rodID=LOSA3602

Someday when I get bored ill make something like this to fit in a spec r gear diff.
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Old 11-07-2012, 11:54 AM   #152
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Outrunners are fun to play with, Don.
That is one beautiful piece of engineering! Maybe you are the guy we need to prototype a car with one motor per wheel!
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Old 11-07-2012, 11:58 AM   #153
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Originally Posted by jsinclair View Post
http://www.losi.com/Products/Default...rodID=LOSA3602

Someday when I get bored ill make something like this to fit in a spec r gear diff.
I had not the slightest idea that Losi already made something like this! As I mentioned in a previous post, open diff on corner entry with progressive lock-up on acceleration out of the corner would be an immensive improvement over anything we have now in TC. The Losi design doesn't appear to be directional, though. It looks like it works identically for both acceleration and braking, so it would be less tunable than an electronically-controlled diff. Also, changing springs inside the diff is less appealing than just twisting a knob to make an adjustment.

Is this too big to fit into a TC?
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Old 11-07-2012, 04:00 PM   #154
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Thanks, still playing with it. Right now there may be something wrong with the sc, it appears to be not reaching top speed. Of course plugging it in backwards doesn't help!(duh) Don
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Old 11-07-2012, 07:14 PM   #155
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I'd think if you wanted to do motors in the wheel, the axle would become the rotor. The motor bearings and axle bearings would then be one and the same. Then you'd have the stator that goes around that, and have to find a way to wrap steering knuckles and rear hubs around that. I'm guessing the easiest solution would be to have a standardized outside dimension for the stator, with a locating tab of some sort, and then just have composite uprights that clamp onto the stator. If you hit things, you'd still be replacing composite parts and bearings, so durability shouldn't be too much of an issue. It's a fascinating idea. I really don't know how you'd replace the power of one of our current TC motors with even 4 smaller ones, and still have them fit inside a steering knuckle, though.

-Mike
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Old 11-07-2012, 10:03 PM   #156
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I had not the slightest idea that Losi already made something like this! As I mentioned in a previous post, open diff on corner entry with progressive lock-up on acceleration out of the corner would be an immensive improvement over anything we have now in TC. The Losi design doesn't appear to be directional, though. It looks like it works identically for both acceleration and braking, so it would be less tunable than an electronically-controlled diff. Also, changing springs inside the diff is less appealing than just twisting a knob to make an adjustment.

Is this too big to fit into a TC?
Its far to big for a tc.

A proper locking gear diff for a tc could be made far simpler. I am no good with solid works or any other 3d design program, so hopefully you can follow.

Instead of a mechanical "locker" or a "clutch pack" , why not allow the gears to bind?

So viewing the diff cup with the large end up, slots would be needed to allow the cross pins to rotate from 12'o clock to 1'o clock. Having four small "ramps" facing the inside of the cup, the "ramps" would be behind the bevel gears that ride on the cross pins. The theory behind this would be that when power is applied to the diff the gears would be forced "up" the ramp and towards the center. Thus binding the gears and "locking" the diff. Once the diff is off power or under braking the gears would "slide down" the ramp, unbind the gears and " unlock" the diff.

Hopefully you could follow, it makes perfect sense in my head .lol


Another locking diff idea would be something like a truetrack made by Detroit. http://www.eaton.com/Eaton/ProductsS...als/PCT_221471

I think something like this could also be tuned to work for us. I have one in my land rover discovery, it works but I wouldn't call it a locker.
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Old 11-08-2012, 04:32 AM   #157
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I'd think if you wanted to do motors in the wheel, the axle would become the rotor. The motor bearings and axle bearings would then be one and the same.
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All you need to do is encapsulate a magnet segment in the plastic of the rim and that's your rotor.
These are great ideas, guys!

One advantage of magnets in the rim is that it's easy to get the number of poles needed to come up with the correct kV rating to drive the wheel directly, with no gear reduction. The kV rating could be changed with a different rim. It would probably be best to use some sort of "sub-rim", so the tire and its rim would remain the same.
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Old 11-08-2012, 04:36 AM   #158
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Originally Posted by jsinclair View Post
A proper locking gear diff for a tc could be made far simpler. I am no good with solid works or any other 3d design program, so hopefully you can follow.

Instead of a mechanical "locker" or a "clutch pack" , why not allow the gears to bind?

So viewing the diff cup with the large end up, slots would be needed to allow the cross pins to rotate from 12'o clock to 1'o clock. Having four small "ramps" facing the inside of the cup, the "ramps" would be behind the bevel gears that ride on the cross pins. The theory behind this would be that when power is applied to the diff the gears would be forced "up" the ramp and towards the center. Thus binding the gears and "locking" the diff. Once the diff is off power or under braking the gears would "slide down" the ramp, unbind the gears and " unlock" the diff.

Another locking diff idea would be something like a truetrack made by Detroit. http://www.eaton.com/Eaton/ProductsS...als/PCT_221471
I can relate to your experience with 3D systems. I once fiddled with ProE for a few hours, but it became painfully obvious that I wasn't going to learn anything in such a short time.

Binding gears are used in the Torsen diff, also. The link you gave looks similar. Your idea has the advantage that it can use simple gears rather than the helical ones in the Torsen and others.

In your design, forcing the small gears towards the center (radially) would then wedge the large, driven gears out (axially) against the faces of the diff housing. Placing a friction (clutch) disk at the interface of the driven gears and the diff housing would then make sense. The relatively large area would give the friction disks relatively long life. I experimented with this on my BMT 1/8 scale car, but it only used the wedge action between the gear teeth as the actuating force, not separate ramps as you described. Your idea is much superior.

Would using an external actuator (servo) make the design simpler yet?

I think the ability to change settings on the fly using an external actuator would be a big advantage. For instance, one could use a third channel on the transmitter to change the diff setting for a particular corner (or group of corners) on the track. (I believe real F1 cars do this, via a control on the steering wheel.) There's no way to do that with only mechanical means.
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Old 11-08-2012, 06:00 AM   #159
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Traxxas of all companies makes a servo actuated locking diff for there summit.
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Old 11-08-2012, 06:33 AM   #160
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Traxxas of all companies makes a servo actuated locking diff for there summit.
Thanks for pointing this out, Josh. Unfortunately it uses dog rings for engagement, so it can't be actuated while torque is applied.
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Old 11-09-2012, 06:38 AM   #161
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Originally Posted by jsinclair View Post
Its far to big for a tc.

A proper locking gear diff for a tc could be made far simpler. I am no good with solid works or any other 3d design program, so hopefully you can follow.

Instead of a mechanical "locker" or a "clutch pack" , why not allow the gears to bind?

So viewing the diff cup with the large end up, slots would be needed to allow the cross pins to rotate from 12'o clock to 1'o clock. Having four small "ramps" facing the inside of the cup, the "ramps" would be behind the bevel gears that ride on the cross pins. The theory behind this would be that when power is applied to the diff the gears would be forced "up" the ramp and towards the center. Thus binding the gears and "locking" the diff. Once the diff is off power or under braking the gears would "slide down" the ramp, unbind the gears and " unlock" the diff.

Hopefully you could follow, it makes perfect sense in my head .lol


Another locking diff idea would be something like a truetrack made by Detroit. http://www.eaton.com/Eaton/ProductsS...als/PCT_221471

I think something like this could also be tuned to work for us. I have one in my land rover discovery, it works but I wouldn't call it a locker.

I think your idea is brilliant and uses a principle that is demonstrated to work for one way bearings (used in one-way diffs).

The "Detroit diff" is old hat (alongside other torque-biasing diffs). The one linked above uses a principle used by Quaife diffs actually. The angle of the spiral teeth decides the torque bias (i.e. the maximum torque transferred to a wheel that lost grip completely - say it was off the ground). Another version is a Torsen used in real cars as well and for a long time. I mentioned the torsen because an italian company already makes torsen diffs for R/C nitro cars. I have never bought one, but I have seen them. Look them up on the web.

I didn't manage to understand how the Losi diff linked above works. What makes the spring compress and extend? To me it looks like they would extend on power too and not so sure why they would relax off power in the first place.
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Old 11-09-2012, 06:46 AM   #162
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I didn't manage to understand how the Losi diff linked above works. What makes the spring compress and extend? To me it looks like they would extend on power too and not so sure why they would relax off power in the first place.
It's the same as a ramping clutch-pack diff used in real cars. Instead of the cross pins being held in the case itself, they are held in grooves in carriers on either side (split in half). Torque forces those split carriers to separate (move outward) and apply pressure to the clutches, progressively locking the diff. Lock up can be adjusted by either changing the angles of the grooves in the carriers or changing the amount of preload on the springs.

They are often called "Salisbury" or ZF diffs. Here is a link with diagrams:

http://www.intothered.dk/simracing/differential.html
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Old 11-10-2012, 04:45 AM   #163
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Thank you.

Perhaps a page translated from danish isn't the best idea when trying to explain something quite subtle. A few mistakes there that sent my mind into a spin but I got it (I think). Not sure if it works that well when a wheel is off the ground though. There's better alternatives but I suppose more difficult to re-create at 1/10 scale (read costly).
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Old 11-10-2012, 08:46 AM   #164
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To have turning (i.e. steering) wheels you need to have a steering servo.

The setup needn't be fragile. Real cars already have this setup and they're working fine. All you need to do is encapsulate a magnet segment in the plastic of the rim and that's your rotor.

Not that cheap right now, but it shows it can be done. Like I said. Create/find the market and it will happen.

Oh yeah, most deff. can be done, but it would not be so cost effective right now. My whole idea was not to do away with steering servos all together, but get a servo that will just point the wheels, the torque will be handled by the difference of speed in the turning wheels. Think tank tracks with just the front wheels varying in speed. 4 individual motors in the wheels will actually do away with diffs. Take it one step further and put a yaw sensor on it......the possibilities are endless, but then you are going to end up with a car that is pretty much a laptop. Drives itself pretty much.

I still think the biggest difference right now that can be made is shocks. I see the t shocks coming out and it's a step in the right direction as the piston stays centered and it won't be affected as much with side loads.

I have half a mind to drill and drain the fluid from a 1:1 clutch fan as it's sensitive to heat and see what affect it has when poured in a rc shock then heated.
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Old 11-10-2012, 09:31 AM   #165
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Oh yeah, most deff. can be done, but it would not be so cost effective right now. My whole idea was not to do away with steering servos all together, but get a servo that will just point the wheels, the torque will be handled by the difference of speed in the turning wheels. Think tank tracks with just the front wheels varying in speed. 4 individual motors in the wheels will actually do away with diffs. Take it one step further and put a yaw sensor on it......the possibilities are endless, but then you are going to end up with a car that is pretty much a laptop. Drives itself pretty much.

I still think the biggest difference right now that can be made is shocks. I see the t shocks coming out and it's a step in the right direction as the piston stays centered and it won't be affected as much with side loads.

I have half a mind to drill and drain the fluid from a 1:1 clutch fan as it's sensitive to heat and see what affect it has when poured in a rc shock then heated.

That's pretty much what I said a couple of pages back when I mentioned the Tamiya tanks with their one controller for two motors.

And no, the car won't drive itself any more than they do today with all these smart speedos we have and all their software adjustments. Talk about it no more than airplanes fly themselves (outside of cruising - keep in mind our racing is anything but cruising). Come to think of it, they could drive themselves after you drive them around the circuit once like that BMW on top gear but can you program a computer to push itself to get better and better?
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