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Custom made center ball diff for Schumacher K1 aero

Custom made center ball diff for Schumacher K1 aero

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Old 03-20-2015, 08:30 AM
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Default Custom made center ball diff for Schumacher K1 aero

Hello.
Just wanted to showoff the center diff I made for my Schumacher K1 aero.
Me and a friend designed it in SW and then 3D printed the parts in a SLS machine, (you know those white parts you see on prototype cars? then my parts are made with the same 3D printer) and the metal parts were milled.





I also made a "limited slip" housing but it doesn't work too well:




And the parts themselves (will be dyed red):

48p VS 32P spur gear,




Diff housings (the holes for the balls have an internal shape so the balls would click in),





The metal parts,






And assembled,





Here's a vid showing it does work

https://www.youtube.com/watch?v=k39_wSeBA9U

It was really hard to make it all fit as there's very little room so I had to fight over tenths of mm to make it fit but everything sits very well as it should.


Today I ran it at the track and it certainly has potential!
I need to make the holes for the balls 0.1mm smaller so it would have more friction (it would be as if I used heavier oil).
Over all it held up great. The 32p spur and the pulleys show no signs of wear what so ever.
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Old 03-20-2015, 09:55 AM
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Nice work !
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Old 03-20-2015, 10:18 AM
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How durable are the SLS gears? I have found that SLS Shapeways Nylon parts is way more durable than FDM parts I make on my own printer, but not as durable as the standard FRP parts we are used to.

The parts look great and the design is really cool!
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Old 03-20-2015, 10:18 AM
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Awesome work! Interested in hearing the durability of the parts.
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Old 03-20-2015, 11:29 AM
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What is the part inside the outer pulley for? I'm not talking about the thrust bearing.
Reducing bushing?
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Old 03-20-2015, 01:42 PM
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I'm not familiar with that car... Does it not normally have a center diff? And what is the function of the balls in the tapered slots? Is it supposed to be limited slip?

Looks great, tho.
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Old 03-21-2015, 01:26 AM
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Originally Posted by orangutanracer View Post
What is the part inside the outer pulley for? I'm not talking about the thrust bearing.
Reducing bushing?
It's a sleeve that allows the load from the spring tension to go to thrust bearing as it can slide a little inside the pulley.

Originally Posted by kingofcool999 View Post
I'm not familiar with that car... Does it not normally have a center diff? And what is the function of the balls in the tapered slots? Is it supposed to be limited slip?

Looks great, tho.
No, it doesn't have a center diff and no one makes one for it. except me
The balls are part of the diff itself. do you know how a ball diff works? I'd explain but my English is not good enough.
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Old 03-21-2015, 03:57 AM
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Cool project. Please update us on how it drives, in and out of corners, any issues with the smaller front tires diffing out, or loss of braking, etc. And the durability as mentioned by several.
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Old 03-21-2015, 11:11 AM
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I am curious the thinking behind using a sleeve and not just putting a slot for the pin in the pulley itself?
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Old 03-22-2015, 05:29 AM
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1. The pulley has to sit at a precise spot or it will bind against the other pulley.
2. I wouldn't be able to hold the pin in the pulley.
3. I don't think the plastic would like the force of the spring pushing against it which might cause binding.
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Old 03-22-2015, 07:17 AM
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Very cool project! I'm always glad to see racers designing and implementing their own parts!

I have a feeling that before we know it, replacement parts will be a "click away" on personal 3d printers!
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Old 03-22-2015, 08:17 AM
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There is an aftermarket center diff for the TLR 22-4 that you may find interesting. It uses roll-pins instead of balls to limit action.
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Old 03-23-2015, 02:14 AM
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Wow! Great skills! Why the 32dp? Are you expecting durability issues with 48dp SLS gears?
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Old 03-23-2015, 03:56 AM
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As you can see in one of the pictures the 48p is really small and isn't "sharp" as molded spur gears teeth so I assumed it wouldn't hold to the abuse so used the 32p right from the start.
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Old 06-23-2015, 12:38 PM
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It's been a long time, but I have some updates:

The ball diff would diff out too easily (it's like having a really thin oil) so I decided to try a "roller diff".
Instead of using balls I'm using 3.5X5.5mm pins. My was is that it would increase the resistance and work smoother for a longer time.

Here are a few pics:





After assembling the diff with the rollers it really does have way more resistance so I'm optimistic

Hope to test it this Friday!
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