pic: Team 3266 CAD project

[BurkeHalderman]

loading photo ...

[O'Sancheski]

Great job.

Just a few questions.
-Is there any reason you don't have any axles?
-I don't see any sprockets. How do you plan on driving the wheels?
-Is there a specific reason you chose the toughboxes over the supershifters? (My guess is cost)
-Is the center wheel dropped? If not, you might want to change the front or rear wheels to omnis because it will be a nightmare to turn.

[Akash Rastogi]

Originally Posted by O'Sancheski

Great job.

Just a few questions.
-Is there any reason you don't have any axles?
-I don't see any sprockets. How do you plan on driving the wheels?
-Is there a specific reason you chose the toughboxes over the supershifters? (My guess is cost)
-Is the center wheel dropped? If not, you might want to change the front or rear wheels to omnis because it will be a nightmare to turn.

Joe, the OP seems to be a beginner, cut him some slack on missing parts. He probably knows they need to be there. Its just unfinished CAD.

[Aren Siekmeier]

Excellent start!

Essentially what Joe is getting at is to continue adding detail. You will find that the biggest benefit of CAD is having everything planned out before hand so that when construction rolls around there are no questions and it just flies together. You can make sure everything fits exactly how you need it to before cutting anything. So you're off to a great start, just make sure to pay attention to all the detail. Since this is just practice it's not as crucial but when build season rolls around it will be.

One suggestion: I assume you are using dead axles, given the bearing blocks you have chosen. In that case, you might want to consider putting the wheel axles straight through the lower frame rails. This will give you some freedom in the vertical direction to get a drop on the center wheel, which you will need if you want to turn, and cuts out extra components.

[BurkeHalderman]

Originally Posted by O'Sancheski

Great job.

Just a few questions.
-Is there any reason you don't have any axles?
-I don't see any sprockets. How do you plan on driving the wheels?
-Is there a specific reason you chose the toughboxes over the supershifters? (My guess is cost)
-Is the center wheel dropped? If not, you might want to change the front or rear wheels to omnis because it will be a nightmare to turn.

For axles I was planning on using 1/2" bolts so I didn't bother to CAD them, and there's no sprockets yet because I don't have any #25 sprocket CAD files.

I chose the toughboxes over supershifters for cost and the simplicity.

The center wheel is dropped 1/8"

[O'Sancheski]

Originally Posted by BurkeHalderman

For axles I was planning on using 1/2" bolts so I didn't bother to CAD them, and there's no sprockets yet because I don't have any #25 sprocket CAD files.

Here are some #25 sprocket files. http://team1323.com/cad/pages/sprockets.html RC has done some great CAD and has put most of his stuff online for download.

I chose the toughboxes over supershifters for cost and the simplicity.

Thats the exact reason that I thought. Whats the reduction that you are running?

The center wheel is dropped 1/8"

Perfect. You might be able to go a little less but 1/8" is perfectl.

Great start on CADDING. I hope to see some of your work in the future.

[JamesCH95]

Just a tip:

McMaster has CAD models of many of the products they sell, including bolts and sprockets. It's great to help build up a BOM when you eventually build the robot. There's hardly an excuse to not have those bits modeled because it's a simple download if they have the parts you want.

[BurkeHalderman]

Originally Posted by O'Sancheski

Thats the exact reason that I thought. Whats the reduction that you are running?

It is a 12.7:1 reduction, just the standard reduction they come with. I'll update the CAD tonight or tomorrow and repost it.

[BurkeHalderman]

Update! I've added axles from Mcmaster carr and sprockets from team 1323's cad library. Right now I have a 22 tooth sprocket on the toughbox and a 36 tooth sprocket on the wheels. Also the top support for the toughbox I changed from 1/8" wall to 1/16". Thanks everyone for your help so far!

[Ninja_Bait]

How are the chains for the two back wheels set up? Specifically, are the wheels lined up (with the sprockets spaced out to line up with the drive sprocket) or are the wheels out of line (with both sprockets mounted flush with the wheel)?

[akoscielski3]

Great Job! My First CADed Chassis didn't look this nice. (i have now made 7 chassis). Make a couple more chassis and you will then definitely have a feel for the CAD you are using. This will also give you a chance to choose a basic chassis design when designing this season. Try making a sheet Metal one, mucanum/omni, West Coast Drive, Swerve (maybe). Experiment a little with wheels and gear boxes.

I have to say that I do not like how the bearing block's are set up though. Because they are sitting on the top of the lower Brace all your wight from your robot will be on two bolts. If you had them on top then the weight would be on the brace. Another option is to make plates to put on either side of the wheel. Bolt the plates to the top and bottom braces and the axles bolted to the plates.

Good Luck!!

Edit: Here is a pic of what i was talking about before.

http://s1220.photobucket.com/albums/...WheelMount.png

[Ninja_Bait]

Originally Posted by akoscielski3

I have to say that I do not like how the bearing block's are set up though. Because they are sitting on the top of the lower Brace all your wight from your robot will be on two bolts. If you had them on top then the weight would be on the brace. Another option is to make plates to put on either side of the wheel. Bolt the plates to the top and bottom braces and the axles bolted to the plates.

Good Luck!!

It'd be more like ten bolts, each of which could easily hold the ~15 pounds of force on them (based on a 150lb robot with even weight distribution).

[BurkeHalderman]

Originally Posted by Ninja_Bait

How are the chains for the two back wheels set up?

The sprockets are mounted flush to the wheels and the wheels are out of line. The back wheels have a slightly shorter base, but the middle and front wheels are in the center of the axle.

There's 24 bolts total that hold the axle mounts in place. If the robot is 150lbs that's 6.25lbs per bolt. Right now the axle mounts are designed to use 1/4"-20 bolts, but I might change that to 10-32 to save weight.

[akoscielski3]

Originally Posted by BurkeHalderman

The sprockets are mounted flush to the wheels and the wheels are out of line. The back wheels have a slightly shorter base, but the middle and front wheels are in the center of the axle.

When designing a chassis i've always tried to line the wheels up. I dont know if it makes a difference at all though. Im not saying you should line them up, but does anybody know if lining the wheels up vs letting them be off make a difference in performance, or efficiency?? Thanks

[JamesCH95]

Originally Posted by akoscielski3

I have to say that I do not like how the bearing block's are set up though. Because they are sitting on the top of the lower Brace all your wight from your robot will be on two bolts. If you had them on top then the weight would be on the brace. Another option is to make plates to put on either side of the wheel. Bolt the plates to the top and bottom braces and the axles bolted to the plates.

Consider that the working tensile load of a Grade 2 1/4-20 bolt is around 1,700lbf. That is to say you could hang 10-11 robots from a single Grade 2 1/4-20. I do not think the four bolts on what I assume is a dropped-center 6wd middle axle will have any issues at all.

Your design is structurally superior, and your suggestions to improve strength is sound, but I believe the design is already strong enough. More reinforcement will only add weight.