pic: Shaft Drive Bearing Blocks

[Jeremiah H]

Originally Posted by MAteo9944

I went with the solid shafts so that I could use shaft keys instead of set screws. I do like the idea of quill shafts. I will have to look into them.
Hopefully one day soon I can get hold of an ME for long enough to go over all of the calculations for the strength of the system. As of now the design is still without the support of the calculations, so the sizes and types of components are subject to change.

Cool idea. I like it.
On the keys/set screw thing, I suggest looking into using hex stock rather than round. I know that it will make the build phase harder, but I believe that the advantages gained will be well worth it. The hex gives you six corners to bear the load, and I would think that you could drill quite a bit out of the center without losing much strength. I know hex is used in John Deere hay balers for the main driving shaft, and I have never heard of there being problems with them (not there, at least). JH

[amos229]

Great design. but if the frame flexes chances are something is gonna skip or break. plus under the tremendous forces on that shaft i doubt the bearing blocks will stay in place. If its a flat game this year then it might work but even then the robots still take alot of beating.

[Dan Richardson]

Originally Posted by MAteo9944

I went with the solid shafts so that I could use shaft keys instead of set screws. I do like the idea of quill shafts. I will have to look into them.
Hopefully one day soon I can get hold of an ME for long enough to go over all of the calculations for the strength of the system. As of now the design is still without the support of the calculations, so the sizes and types of components are subject to change.

Yeah this is a neat design something you don't see very often, and there may be some good reasons, the efficieny is one thing, another is what you've addressed above.

It will be significantly important for you to go over the stress strain differentials with an ME. There will be many things you'll have to worry about, one is axial and torsional stresses, make sure the shaft is strong enough so that it can handled the axial stresses over the distance and that your degree of rotation is not very significant, as to where it could cause failure.

Make sure the shock, or impulse, of the robot flying full speed into a wall, or another robot is not transfered through the shaft. And if it is at all transfered make sure that the shaft is robust enough so that absorb the impact plastically without significant deflection and no deformation.

Also important, and quite possibly the easiest thing to overlook. is the frame. Frames over the course of competition have a tendancy to get all bent out of shape, it is often minute, but It does happen. In a system where allignment is paramount for optimum effciency its important that frame flexure is limited. A rigid frame will be important make sure that frame is designed in such a way that deflection is minimum and even slight deformation is avoided.

Looks good tho, I'm excited to see the newer drive style, will love to see how it works out.

[TVan]

Looks great, I would consider a flexible shaft coupling on each side. If it looks like your frame will flex, you would not like teeth on the field

Tim

[Al Skierkiewicz]

Matt,
I know that the drawing may not show the components in correct scale but with this kind of drive there are some significant forces that need to be addressed. The rotational forces on each shaft when pushing or in stall will produce a side force if you think about it. Because of those forces, larger bearings and stiffer blocks are needed relative to other types of drive. Without the extra beef, misalignment and high frictional forces will occur in the bearings and shafts. Think of the construction of a car differential and you will get an idea of the kind of strength you will need.

[Not2B]

There's been alot of good engineering concerns (side forces, stress on the shaft, etc...)

Here's one more.

Imagine hitting it with a sledge hammer. Can you get it working again in 5 minutes? Can you get a chain drive working again in 5 minutes?

[MrForbes]

How about mounting both bearings on either side of one support, and get rid of the othe support? it would save some weight, and should give adequate strength to hold the gear in alignment.

[RyanN]

Great work on your drive train system! One thing to think about that I thought of... How about making a worm gear system. I think this would be more reliable than the one that you currently have, and you will have much greater control of your robot. The only thing is that you probably would want a fairly small gear on the axle that goes to the wheel.

Just my $0.02...

[MAteo9944]

Originally Posted by RyanN

Great work on your drive train system! One thing to think about that I thought of... How about making a worm gear system. I think this would be more reliable than the one that you currently have, and you will have much greater control of your robot. The only thing is that you probably would want a fairly small gear on the axle that goes to the wheel.

Just my $0.02...

The problem with worm gears is in the efficiency. They are usually about 60-70% efficient as opposed to the 95% efficiency of a miter gear. Some worm gears are even as low as 20% though I have also seen 98% reported.

[Jeff Pahl]

Originally Posted by MAteo9944

The problem with worm gears is in the efficiency. They are usually about 60-70% efficient as opposed to the 95% efficiency of a miter gear. Some worm gears are even as low as 20% though I have also seen 98% reported.

Depending on the game and strategy, the resistance of worm gears to being back driven may be advantageous, or a significant disadvantage. However, I think it would take a lot of strategy advantage to make up for the loss in efficiency.

And it would make it about impossible to push the robot around without turning it on and having the controls. Since it usually has to go in the back of my truck to go to demos, etc. I would really hate that

[RyanN]

Originally Posted by Jeff Pahl

Depending on the game and strategy, the resistance of worm gears to being back driven may be advantageous, or a significant disadvantage. However, I think it would take a lot of strategy advantage to make up for the loss in efficiency.

And it would make it about impossible to push the robot around without turning it on and having the controls. Since it usually has to go in the back of my truck to go to demos, etc. I would really hate that

I was not sure of the efficiency of a worm gear system. I did not analyze how a worm gear system would be disadvantageous to a team and only looked at the advantages. I saw that the robot would be very responsive (Like when the driver would let go of the joysticks, it would immediately stop) and that other robots could not push my team's robot around, but then you said that it would be a "significant disadvantage," which I can see happening very easily. It would be almost impossible to push a locked robot across the field in the time frame that FIRST gives us during a match. Another disadvantage I found, and I'm not sure if you guys said or not, is that when pushing a robot, the efficiency of the system decreases as friction between the gears increases... I remember this now from my Erector Set when I was a kid. Brings back some memories... Now back to reality; now that I see the disadvantages, I would not use a worm gear system. I guess another advantage that I thought of is that this system would probably be more reliable than our traditional chain method.