Hi everyone,
I'm new to robotics, and I have a rather mechanical question.
Gear 1 is at a fixed position but can turn on itself.
Gear 2 can both move horizontally between A and B, and rotate on itself if gear 2 rotates but its horizontal movement should not affect gear 1.
I thought of a timing belt but that only works with two fixed positions, whereas here gear 2 must be able to be turned by gear 1 at any point between A and B.
Any idea how do we solve this problem?
Thanks
You need to provide more information if you want a valid answer.
For example:
Also, gears are typically not used with timing belts. Those use pulleys. Or if you want to use a chain, you would use sprockets. Gears typically only interface with other gears.
In addition to that, you should tell us what you are trying to do. There may be a better solution out there that uses a completely different solution if we have an idea on what then end goal is.
You want Gear 1 to drive Gear 2, regardless of the distance between A and B, correct? And your intent is to use a belt drive?
This problem comes up in tanks and other vehicles using tread drives. The normal solution is to add a "tensioner" pulley as a "third wheel" inside the loop of the belt. The tensioner is usually free to move at an angle to the A-B axis, and is spring-loaded. So, as the A-B distance decreases, the tensioner pulley moves orthogonally to the A-B line, taking up the belt slack and making the belt path triangular. When the A-B distance is maximum, the tensioner may be almost on the A-B line. The tensioner is an "idle" pulley -- it spins freely, and it's only interaction with the drive belt between Gears 1&2 is to maintain a certain set tension on the belt at all times.
In some solutions, the tensioner's motion is mechanically linked to the A-B distance via a linkage or drive train, so that instead of being spring-driven, the tensioner's position is precisely controlled by the A-B distance in real time.
@SkyeFire i thing you got what i want.
So If i understood you mean something like this:
But wondering how to synchronize between Gear 2 and the tensioner mechanically. After reading your precision I'm able to visualize the idea with linkage (this seems to me to require high precision, how will I calculate its dimensions), but do not know what is "drive train".
I try to move a small plate on the X and/or Y coordinates thanks to two motors placed on the right and left of the device and fixed.
If the motor on the right was fixed on the plate supporting the tray it would be easier, but the 2 motors must not move.
So here my problem is Y.
have you seen "hinged cable carrier"? basically it is three hinges (A,B,C) with two solid links between A-C and B-C. A and B are attached to your structure while C (the elbow) is free to move.
length of links is fixed making it easy to have fixed length belt drive.
Note that if pulleys are directly coupled at C, changing distance between A and B, while A does not rotate, would still cause a bit of rotation at B. if this is the issue, it can be solved either in software (X axis position is known and can be used to compensate Y-axis position with simple trigonometry) or mechanically by connecting pulleys at C by gears for example.
one should evaluate how much of this makes sense (perhaps one wants to reduce weight of Y-axis and keep its motor stationary). normally it is much simpler to just put the motor onto Y-carriage
I try to move a small plate on the X and/or Y coordinates thanks to two motors placed on the right and left of the device and fixed.
If the motor on the right was fixed on the plate supporting the tray it would be easier, but the 2 motors must not move.
So here my problem is Y.
That sounds more like you need something like the CoreXY kinematics. This is designed to achieve X and Y motion with the interactions of two fixed-position motors.
There is endless number of solutions, as I see it.
First, make a long belt and put a weight on its lower side (so two gears and weight form a triangle). This is ugly.
Second (what people usually do if they have money) use two motors, one for each gear.
Third, replace your setup with sort of robotic arm - and put belts along it.
Fourth, use a solid rod along the A - B line and conic gears, so that rotation is passed. You will have to make second (B) set of gears slide along the rod, but it is doable.
Easiest approach would be to use flexible spring-like device to pass the rotating momento.
If you need specifics, look at OLD dental drills, they had couple of solutions for that task: google up "dental drill with belts" and click "images".
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