Chief Delphi

Chief Delphi (http://www.chiefdelphi.com/forums/index.php)
-   Extra Discussion (http://www.chiefdelphi.com/forums/forumdisplay.php?f=68)
-   -   pic: Plywood Butterfly Drive Render (http://www.chiefdelphi.com/forums/showthread.php?t=129813)

z_beeblebrox 18-06-2014 12:18

Re: pic: Plywood Butterfly Drive Render
 
Quote:

Originally Posted by AllenGregoryIV (Post 1390345)
The biggest issue with this is it makes it harder to do your reductions.

It's not too hard with the central gearbox design since you can do a second reduction with the belts to the modules. From JVN's calculator, a 12:60 reduction in the gearbox and a 24:42 reduction with the belts gives adjusted speeds of 6.4fps on the Colson wheels and 12.9 fps on the omni wheels.

Quote:

Originally Posted by Joe G. (Post 1390315)
Have you considered using pancake cylinders for module actuation to save some space and weight?

I'll look into doing that.

I noticed a few problems with my design that I also need to fix in the next iteration: the belts to the modules run into the bellypan, the bolt that serves as an axle for the gearbox is not adequately supported and the bottom two CIMs in each gearbox can't be installed or removed once the chassis is assembled.

AllenGregoryIV 18-06-2014 13:10

Re: pic: Plywood Butterfly Drive Render
 
Quote:

Originally Posted by z_beeblebrox (Post 1390348)
It's not too hard with the central gearbox design since you can do a second reduction with the belts to the modules. From JVN's calculator, a 12:60 reduction in the gearbox and a 24:42 reduction with the belts gives adjusted speeds of 6.4fps on the Colson wheels and 12.9 fps on the omni wheels.

The other reason we prefer to float the traction wheels is that if we lose air, or if we lose a belt in a module we default to the omni wheels which is where we spend around 90% of our time anyway.

Chris is me 18-06-2014 13:40

Re: pic: Plywood Butterfly Drive Render
 
If it simplifies the design, you could consider the option of using shifters for the central gearboxes rather than a pulley reduction between the traction and omni wheel. That way, you can shift from high speed to high torque independently of which wheels are on the ground and pivoting about the traction wheel isn't a big hassle. However, this is added complexity.

fb39ca4 20-06-2014 00:14

Re: pic: Plywood Butterfly Drive Render
 
It's great to see another team going with this method of construction. Mine has been doing laser cut plywood chassis in the past two years, and we love it.

z_beeblebrox 20-06-2014 00:21

Re: pic: Plywood Butterfly Drive Render
 
Quote:

Originally Posted by fb39ca4 (Post 1390532)
It's great to see another team going with this method of construction. Mine has been doing laser cut plywood chassis in the past two years, and we love it.

Is there anywhere I could find more information on your designs and construction method? What thickness and type of wood did you use? How did it hold up in competition?

It's hard to find high-quality information about wood chassis in FRC since so few teams have used them.

RKIyer 20-06-2014 02:27

Re: pic: Plywood Butterfly Drive Render
 
How are the cut plywood pieces of your frame and wheel assemblies attached together? Are you using a glue? Or are there tiny screws?

Electronica1 20-06-2014 08:45

Re: pic: Plywood Butterfly Drive Render
 
Quote:

Originally Posted by z_beeblebrox (Post 1390535)
Is there anywhere I could find more information on your designs and construction method? What thickness and type of wood did you use? How did it hold up in competition?

It's hard to find high-quality information about wood chassis in FRC since so few teams have used them.

You can go on http://frcdesigns.com/ and look at 1771's cad from 2011 and 2012. They had some very good wood robots.

z_beeblebrox 20-06-2014 11:13

Re: pic: Plywood Butterfly Drive Render
 
Quote:

Originally Posted by RKIyer (Post 1390544)
How are the cut plywood pieces of your frame and wheel assemblies attached together? Are you using a glue? Or are there tiny screws?

It's designed to be assembled using wood glue.

z_beeblebrox 27-06-2014 07:47

Re: pic: Plywood Butterfly Drive Render
 

Here's my progress on the next iteration of the drivetrain. The chassis will be sturdier when complete, but the module and powertrain are just about done. Currently, it weighs 30.5 lbs (the same as the original 4-CIM version).

Improvements in this version include:
-Simpler and lighter powertrain due to direct-drive gearbox
-Stiffer module with less wasted space
-Smaller, lighter pancake cylinders for switching between wheels
-Narrower side rails and more open bellypan

The outside plates will be attached with T-nuts (http://goo.gl/XBWxdN) so they are removable for easy maintenance.

z_beeblebrox 27-06-2014 17:57

Re: pic: Plywood Butterfly Drive Render
 
Here's the more-or-less complete version of the drivetrain, except for the finger joints, which are time-consuming and no fun to draw. Sturdier structure, lightening holes and encoder mounts are added. The pneumatic cylinder mounting is improved.

The two aluminum tubes on top are an example of how a hinged superstructure can be mounted, similar to our 2014 robot (http://www.chiefdelphi.com/media/photos/39338).

I'd like to integrate bumper mounts into the wood frame, but am uncertain of how best to do so in a way that is simple, robust and allows for quick swaps. Anyone have ideas?



Unless anyone has ideas for improvement, next steps are probably cutting some test pieces on the laser to learn about best practices for finger joints, large parts and bearing fits before manufacturing a full drivetrain.


All times are GMT -5. The time now is 17:11.

Powered by vBulletin® Version 3.6.4
Copyright ©2000 - 2017, Jelsoft Enterprises Ltd.
Copyright © Chief Delphi