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Re: pic: Shaft Drive Bearing Blocks
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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 |
Re: pic: Shaft Drive Bearing Blocks
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.
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Re: pic: Shaft Drive Bearing Blocks
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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. |
Re: pic: Shaft Drive Bearing Blocks
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:eek:
Tim |
Re: pic: Shaft Drive Bearing Blocks
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. |
Re: pic: Shaft Drive Bearing Blocks
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? |
Re: pic: Shaft Drive Bearing Blocks
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.
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Re: pic: Shaft Drive Bearing Blocks
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... |
Re: pic: Shaft Drive Bearing Blocks
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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. |
Re: pic: Shaft Drive Bearing Blocks
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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 :) |
Re: pic: Shaft Drive Bearing Blocks
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