To respond to your questions:
Quote:
Originally Posted by asid61
Interesting module you got there. I like the use of a lazy susan to take up thrust loads from the module; I don't think I've seen that on here before.
|
Thanks, I haven't seen it eather on here. I saw it on McMaster and thought "hmm...I wonder if I can make a swerve around this."
Quote:
Originally Posted by asid61
1. Why the use of #6 screws to retain your dead axle? That seems pretty weak compared to using a 1/4"-20 or a #10 screw, especially because you can use unmodified Vex tube axle for the former.
|
The wheel shaft is 3/8" round. I was hesitant to drill a large bore hole in it, but I could probably step it up to #8.
Quote:
Originally Posted by asid61
3. It looks like you have only a single gear reduction to the small gear of the module rotation. By my calculations, that means you can only have a maximum ratio of 42:1 to rotate the module, which is a little too low (~370rpm from an RS-550 motor). You may need to add another stage to your VP.
|
You're right on the 42:1. I think I could theoretically step it up to 60:1 by using a 14t 3/8" Hex gear instead of the 20t 1/2" Hex gear I'm using now. According to the JVN calc, an AM9015 through a 42:1 reduction pushing 1/4 of the robot weight at a radius of 1" results in 1140 deg/s at 23A. I thought that would be enough, but if you think it isn't I can look into increasing it.
Quote:
Originally Posted by asid61
4. The use of 1/8" plate to support your module is very thin, thinner than any other swerve I have seen. Consider upgrading to sticking it into a 2x1 or just 3/16" plate. You're lightening very aggressively for 1/8" plate.
As a general note, keep in mind that when losing weight, it's usually better to change your overall design rather than focus on lightening patterns. Patterns get it down maybe 1/4lb to 3/8lb on a 5.5lb swerve IME, and cannot lose significant amounts of weight.
|
I wasn't sure what was a good thickness plate to use. My next iteration (if I iterate again) will probably use a less-pocketed 3/16" plate.
Quote:
Originally Posted by asid61
6. I like the belted first stage. If you plan to make this IRL, I would add some kind of a tensioner just in case it doesn't turn out 100%.
|
Probably a good idea. I don't actually plan on building it because I aged out last year, but I will look into adding a tensioner to the next iteration.
Quote:
Originally Posted by asid61
7. Why do you have a bearing at the top of your module? It doesn't seem to do anything.
9. You shouldn't rely on the lazy susan to align your bevel gears. It will help a lot if you stick 1 or 2 bearings into the large turning gear to constrain that shaft. Right now, because the large turning gear is constrained only by the lazy susan, it can easily slosh around and screw up your bevel gear alignment.
|
Right now, the two bearings retaining the vertical shaft are on the bottom and top plate. If I move that top bearing to the 84t gear, I will have to shift the vertical miter gear down 1/2" (because right now the miter gear hub fits inside the 84t gear), thereby increasing the module height by 1/2". It might be worth it though to get rid of the top plate and to better define the cocentricity of the vertical shaft.
Quote:
Originally Posted by asid61
8. Why are you riveting the lazy susan on instead of using screws? Just curious, may or may not be an issue.
|
I chose to use rivets because it meant that I don't have to rely on tapping the plates or having nuts hidden inside the module that I would need to get to to take it apart. This way, all I need to take apart the module is a clear shot to drill out the rivet. If there is a good reason to use screws instead of rivets, I wouldn't be strictly opposed to it.
Quote:
Originally Posted by asid61
10. If you mount the S4 over your CIM via surgical tubing, how will you keep the hex adapter from sliding upwards?
|
I was planning on using CIM retaining rings above and below the hex adapter to keep it in place. The surgical tubing would just slide over it.
Thanks for all the comments and suggestions.
P.S. - I forgot to put the custom parts list in the original post:
- (6) waterjet cut sheet aluminum plates
- (1) waterjet cut gears
- (3) center bored shafts for retaining screws
- (1) bent piece of lexan - not modeled