pic: Modular Prototype Drive
 

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Is anything supporting the wheels beside the shifters?

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I contacted Andymark and they said that I would not have to support them, the 1/4 in aluminum and bearings would be enough.

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I'm not sure about this, but I don't think that the bearings in the supershifter gearbox are designed for the side loads that this setup would create. You'll also end up bending the axle if you aren't being careful when you drive!

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I'd tend to believe AM-- they tend to be rather conservative in their estimations of what something can or cannot handle.

That being said, I'm sure testing will bring about all sorts of new problems for you to solve. There's no substitute for driving the hell out of it and seeing where things go from there.

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We rebuilt our 2012 drivetrain before IRI and directly driving our middle wheel with a supershifter had no problem driving over the barrier with 6 in wheels. Although it is preferable to support the other side I'm not sure it is completely necessary.

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I'm sorry, you're right. If Andymark told you it doesn't need to be supported, they're right. I missed that part while I was reading.

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Interesting design! What is the lowest possible offset for the drop in it? Also, with using the one cylinder, how do you prevent the shifting of one gearbox before the other?

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We cut slots in the frame so the wheels line up with the center of the frame, we add as many washer as needed to get the correct drop. For the cylinder we went with a 3/4x 1 inch throw, each shifter has a 1/2 inch throw so as soon as one side bottoms out it will throw the other to the bottom. With 45 lbs of force I thick both will shift instantly.

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With what you have built are the wheels only connected to the gear boxes going to be powered?

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We have a sprocket between the wheels to drive the other wheels so we can have six wheel drive.

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Then that is a double-sided cylinder, both with spring returns?

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We attached a threaded rod to one end of the cylinder.
For competition I will have to attach it different. ( Can't drill and tap cylinders - modifying a cylinder is not allowed)

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Why wouldn't you use a COTS cylinder already end tapped, e.g., ?

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Would it be possible to have the cylinder trip a linkage system, not unlike a 4-arm servo arm actuated on one end of one arm, that would do the shifting? That would also negate the possibility of one side shifting before the other.

Or, you could build a custom sleeve to fit over the end of the cylinder that you can drill and tap (and then pin in place on the cylinder).