So I have been working on a way to make a very light drivetrain that is durable. I want to know what thoughts you guys have on this idea for a gearbox inside the tube. My main worries are structural integrity and maintenance.
I left the wheel off of the direct drive output shaft so the gears could be seen. This features a chain in tube design coupled with a direct drive wheel. JVN calculator has the free speed at 15.54 fps and adjusted speed at 15.01 fps. The sprockets are 16t and I believe will not interfere with the bearings, because they are not doubled up.
There would have to be 4 sets of these gearboxes to make a full 8 wheel WCD. I think that it would work very well, because a lot of weight and space is saved from a traditional WCD in that there are no heavy plates for a gearbox, and the chain is in the tube saving space too.
It appears impossible to actually put the white gear into the tube during assembly. Is it just the perspective or is the OD of the gear too big to slide through the tube to its place in that cutaway?
I may have to cut the tube hole on the top slightly bigger. When i looked at the dimensions in solidworks, the gear is 1.8 inches in diameter, and the space in the tube is 1.8. So theoretically the gear can be slid down inside the tube, but it depends on the tolerances of the tube and gear when they are actually made.
I would suggest using more than one decimal place. 1.8" on the gear could cause trouble if the tube is 1.75" like I think it is. (Unless you’re using thinwall tube, but I highly doubt that based on the dimensions you’ve given.)
I suspect that you’re looking at–at best–an interference fit, which means you’ll be forcing the gear a bit–not fun. It might even be a press fit, which would make life really miserable.
Yeah, I’d cut that tube hole bigger, at least on one side.
I would suggest slotting the top of the tube where the gears are. This would make maintenance easier. If you want the gears to be covered, just put a piece of polycarbonate/wood/sheet metal on a hinge of some sort.
Would the front and rear set of wheels on each side be linked together or would they turn independently?
Would the overall volume be very different if the motor is relocated so that the motor pinion meshed directly with the large gear? This would eliminate two stages of gearing.
The answer is yes that a much larger gear could be put directly to the pinion gear, I wanted the chain in the tube though to save more space. And the other thing is that I think that the sprocket would then maybe hit the cim when it is chained to the other wheel. I would have to check and see, it depends on what speed is desired which would dictate the gear size. The two stage system allows for chain inside of the tube as well as making it easier to change the gear ratio, because you do not have to worry about the sprocket hitting the cim.
It is not seen well, but half of the shaft on the gear next to the cim pinion gear is covered by the cim. So the gear would have to be very large to make space for the sprocket and I don’t think the sprocket would fit.
If you will have four of these gearboxes, you might not save any weight. In a “normal” WCD, you have one gearbox on each side. With the scheme show, there will be two extra large gears plus the other small gears.
If you do not link the two gearboxes on each side, you will get the power of only one of the two CIM motors on each side for much of the time since only two wheels on each side will contact the carpet at any one time.
