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-   -   pic: 2996 Octocanum Prototype (http://www.chiefdelphi.com/forums/showthread.php?t=140982)

Liquid_Science 07-01-2016 01:36

pic: 2996 Octocanum Prototype
 

AdamHeard 07-01-2016 01:37

Re: pic: 2996 Octocanum Prototype
 
I'd be concerned about the slender shafts that front and rear of the cylinders attach to. They might not have enough stiffness.

thedude019 07-01-2016 07:55

Re: pic: 2996 Octocanum Prototype
 
This looks great! Is the weight an issue? Ive seen some really heavy octocanum drives before.

JoshWilson 07-01-2016 08:08

Re: pic: 2996 Octocanum Prototype
 
Quote:

Originally Posted by Liquid_Science (Post 1517448)

looks pretty cool, but I'm not exactly sure how that type of drive train is beneficial, could you explain? I've never seen or heard of it before, so I don't know anything about them.

Ari423 07-01-2016 08:32

Re: pic: 2996 Octocanum Prototype
 
Quote:

Originally Posted by JoshWilson (Post 1517477)
looks pretty cool, but I'm not exactly sure how that type of drive train is beneficial, could you explain? I've never seen or heard of it before, so I don't know anything about them.

The idea is that you get the best of both worlds: mecanum wheels for maneuverability and traction wheels for pushing. The main downsides are weight and complexity.

jnicho15 07-01-2016 08:48

Re: pic: 2996 Octocanum Prototype
 
What was your reason for putting the traction wheels on the pivot? In my team's design, we placed the mecanums on the pivot because then, when you retract the traction wheels, you don't need as much cylinder force to hold them off the ground. For traction mode, the mecanums barely need to be off the ground or can be slightly touching- the cylinders don't need to support nearly as much weight. In your design, the cylinders need to hold the whole weight of the robot up off the ground so only the mecanums are touching.

Liquid_Science 07-01-2016 08:54

Re: pic: 2996 Octocanum Prototype
 
Quote:

Originally Posted by thedude019 (Post 1517472)
This looks great! Is the weight an issue? Ive seen some really heavy octocanum drives before.

We managed to get the weight right around 54 pounds with everything needed to run the bot (electronics, pnematics, ect.)

Liquid_Science 07-01-2016 09:04

Re: pic: 2996 Octocanum Prototype
 
Quote:

Originally Posted by jnicho15 (Post 1517483)
What was your reason for putting the traction wheels on the pivot?

The biggest reason is we wanted to use 4in casters and 6in Mecanums. The cylinders we used should be plenty enough to lift even a fully weighted robot, since the boar on each is 1.5" with a 1" stroke, and there are 4 of them. Aslo, we wanted the casters to be the default wheel if something failed. The two wheels can easily be switched around, if we wanted to run 6in casters and 4in mecanums; depends on the game really.

JoshWilson 07-01-2016 09:06

Re: pic: 2996 Octocanum Prototype
 
Quote:

Originally Posted by Ari423 (Post 1517479)
The idea is that you get the best of both worlds: mecanum wheels for maneuverability and traction wheels for pushing. The main downsides are weight and complexity.

Ok, that makes a lot of sense. Thanks for the explanation!

aldaeron 07-01-2016 09:38

Re: pic: 2996 Octocanum Prototype
 
Have you thought of doing a single larger cylinder between the two modules a la Blue Cheese. Might be less parts and less weight.

What is your gearing for each wheel shaft in the pods from the CIM?

Are you concerned about deflection when the mecanums are down? Seems like a much longer moment arm around the rotation axle. I have wondered this for all the octocanum designs I have seen on CD. It seems like you would want to support the end of the axle that the pod rotates around with a bearing and have an external frame rail running the length. Perhaps the plate between the two pods is enough. Have you tried stacking weight on it to get the bot to 150 pounds?

Love the FIRST logo in the frame =)

-matto-

Chris is me 07-01-2016 09:41

Re: pic: 2996 Octocanum Prototype
 
Quote:

Originally Posted by jnicho15 (Post 1517483)
What was your reason for putting the traction wheels on the pivot? In my team's design, we placed the mecanums on the pivot because then, when you retract the traction wheels, you don't need as much cylinder force to hold them off the ground.

Two great reasons to pivot about the traction wheels. First is that traction wheels will see a lot more force in all directions than the mecanums will, especially when being pushed from the side. Pivoting about the traction wheels means these wheels are more rigidly supported by the whole frame. Additionally, mecanum wheels seem to behave better when on a suspension, and the cylinders will serve as a form of a suspension, helping to ensure all of the wheels are touching the ground. The amount of cylinder force for holding one wheel off of the ground instead of the other really shouldn't change in either case.

JesseK 07-01-2016 12:45

Re: pic: 2996 Octocanum Prototype
 
How does this drive train plan to handle bumpers?

T3_1565 07-01-2016 12:55

Re: pic: 2996 Octocanum Prototype
 
I really enjoy looking at these types of drive trains. Back in my days these types of drives were never heard of. I made something to try and accomplish what this does.

These are cooler to see people make for sure.

JesseK 07-01-2016 13:11

Re: pic: 2996 Octocanum Prototype
 
Quote:

Originally Posted by T3_1565 (Post 1517583)
I really enjoy looking at these types of drive trains. Back in my days these types of drives were never heard of. I made something to try and accomplish what this does.

These are cooler to see people make for sure.

You should provide a link. That type of drive train hasn't been seen since. It was really cool for its time, IMO.

nuclearnerd 07-01-2016 13:21

Re: pic: 2996 Octocanum Prototype
 
Wow, pretty!

I would really recommend extending the outer plates that join your pivot points all the way out to the front and back plates if you can. I'd be worried about cantilevering those huge assemblies off the side of a pair of bearings that are only < 1" apart! Doing so would also let you support your side bumpers for more of their length (the 2014 rules required support every 8").

T3_1565 07-01-2016 13:35

Re: pic: 2996 Octocanum Prototype
 
Quote:

Originally Posted by JesseK (Post 1517587)
You should provide a link. That type of drive train hasn't been seen since. It was really cool for its time, IMO.

I dont want to hijack the thread lol. Search 1565 Linkage if your interested.

I feel like these types of drives came from what that drive was. Opened up the door for pneumatics manipulating wheels. Before that it was only Swerve Drive.

T3_1565 07-01-2016 13:40

Re: pic: 2996 Octocanum Prototype
 
I am curious though. Is there a reason that you need 4 cylinders to move the wheels? Can you put a push bar from 1 pod to another and use a wider diameter piston in the middle of the bot? That way you only need 2 pistons and less chance of there being problems with switching wheels?

As I said I'm old and not up to date on these drives lol. There may be a really easy reason why you need them seperate that I'm missing

blazingbronco18 07-01-2016 14:59

Re: pic: 2996 Octocanum Prototype
 
Looks pretty cool. You guys got a video of it in action?

Max Boord 07-01-2016 17:12

Re: pic: 2996 Octocanum Prototype
 
What was the reasoning for having the mecanum wheels on the outside? If you get into a head on pushing match you are likely to be tipped off of the colson wheels and onto the mecanums. Also why 6 inch mecanums over 4 inch mecanums and a belt or chain reduction to the colson wheels? It seems like that is the more conventional configuration and would allow for smaller and lighter packaging.

Liquid_Science 07-01-2016 18:35

Re: pic: 2996 Octocanum Prototype
 
Quote:

Originally Posted by JesseK (Post 1517578)
How does this drive train plan to handle bumpers?

This is just a prototype to test the octocanum theory. Presumably, bumpers would mount to the outside c-channel, and be reinforced at the 2 axles and the piston mounts as well. Bumpers would need some more thought and experimentation though.

Liquid_Science 07-01-2016 18:37

Re: pic: 2996 Octocanum Prototype
 
Quote:

Originally Posted by blazingbronco18 (Post 1517660)
Looks pretty cool. You guys got a video of it in action?

Not yet. We still have to get code on the robot and do some testing. But hopefully we will have some video by the end of build season.

Liquid_Science 07-01-2016 18:39

Re: pic: 2996 Octocanum Prototype
 
Quote:

Originally Posted by Max Boord (Post 1517723)
What was the reasoning for having the mecanum wheels on the outside? If you get into a head on pushing match you are likely to be tipped off of the colson wheels and onto the mecanums. Also why 6 inch mecanums over 4 inch mecanums and a belt or chain reduction to the colson wheels? It seems like that is the more conventional configuration and would allow for smaller and lighter packaging.

Honesty, the main reason is we had 6in mecanums lying around, and this is our first prototype; we just wanted to see what building a more complex drive train was like. But there have been some good points mentioned in the thread, and mine was if something went wrong, we would be able to default to casters.

Liquid_Science 07-01-2016 18:42

Re: pic: 2996 Octocanum Prototype
 
Quote:

Originally Posted by T3_1565 (Post 1517610)
I am curious though. Is there a reason that you need 4 cylinders to move the wheels? Can you put a push bar from 1 pod to another and use a wider diameter piston in the middle of the bot? That way you only need 2 pistons and less chance of there being problems with switching wheels?

As I said I'm old and not up to date on these drives lol. There may be a really easy reason why you need them seperate that I'm missing

The biggest reason is it gives us some flexibility to try various other things later. This is just a prototype and will be our test bed for all things related to this drive. It isn't a huge difference to go with 2 or 4, and there are ups and downs for both.


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