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-   -   pic: WCD off season chassis from 2471 (http://www.chiefdelphi.com/forums/showthread.php?t=139926)

Bryce2471 01-12-2015 16:42

pic: WCD off season chassis from 2471
 

Harman341 01-12-2015 16:46

Re: pic: WCD off season chassis from 2471
 
I don't see any chain. Is that chain-in-tube or are you just powering the middle wheels?

KrazyCarl92 01-12-2015 16:47

Re: pic: WCD off season chassis from 2471
 
Are you going chain-in-tube to power the corner wheels?

Are the two vertical 2" x 1" tubing pieces on the left side (as pictured) corner wheels encoder mounts? Why do they stick up above the height of the frame?

Zebra_Fact_Man 01-12-2015 17:12

Re: pic: WCD off season chassis from 2471
 
Quote:

Originally Posted by Harman341 (Post 1509126)
I don't see any chain. Is that chain-in-tube or are you just powering the middle wheels?

Quote:

Originally Posted by KrazyCarl92 (Post 1509127)
Are you going chain-in-tube to power the corner wheels?

Is see the question I was going to post has already been asked...

OP please to tell.

Bryce2471 01-12-2015 17:25

Re: pic: WCD off season chassis from 2471
 
Quote:

Originally Posted by Harman341 (Post 1509126)
I don't see any chain. Is that chain-in-tube or are you just powering the middle wheels?

It's a chain in tube design
Quote:

Originally Posted by KrazyCarl92 (Post 1509127)
Are the two vertical 2" x 1" tubing pieces on the left side (as pictured) corner wheels encoder mounts? Why do they stick up above the height of the frame?

They are encoder mounts. They stick up to accommodate the gears that run the encoders. I'm not sure why they were done that way, as I was not involved in their design.

Ty Tremblay 01-12-2015 17:50

Re: pic: WCD off season chassis from 2471
 
What lead you to choose to use tensioners with your design?

One of the major benefits of the in-tube design is that it's practically impossible for a chain to jump the sprocket, especially if the center-to-center distance between the sprockets is correct.

Bryce2471 01-12-2015 18:24

Re: pic: WCD off season chassis from 2471
 
Quote:

Originally Posted by Ty Tremblay (Post 1509144)
What lead you to choose to use tensioners with your design?

I was not involved in that decision, so I can't say for sure. However, I do know that bearing blocks were used so that the the frame could use .0625in wall tubing.

JesseK 01-12-2015 18:46

Re: pic: WCD off season chassis from 2471
 
Do I spy shock absorbers? Or is that black ABS for spacing?

RobotsThatWork 01-12-2015 21:44

Re: pic: WCD off season chassis from 2471
 
for your chain in tube design, are you using 2"x1" tubing? if so, are you using COTS sprockets? I haven't been able to fit 2 COTS sprockets into the tube. It would be great if anyone could tell me how everything was packaged together.

Greg Woelki 01-12-2015 22:00

Re: pic: WCD off season chassis from 2471
 
Quote:

Originally Posted by RobotsThatWork (Post 1509179)
for your chain in tube design, are you using 2"x1" tubing? if so, are you using COTS sprockets? I haven't been able to fit 2 COTS sprockets into the tube. It would be great if anyone could tell me how everything was packaged together.

I can't speak for team 2471, but these fit. A version broached for 1/2" hex is available in the drop down selection box.

R.C. 01-12-2015 22:12

Re: pic: WCD off season chassis from 2471
 
Quote:

Originally Posted by RobotsThatWork (Post 1509179)
for your chain in tube design, are you using 2"x1" tubing? if so, are you using COTS sprockets? I haven't been able to fit 2 COTS sprockets into the tube. It would be great if anyone could tell me how everything was packaged together.

I'm not sure how cots sprocket don't fit? Do they not fit due to the diameter or the width of the sprocket or both?

Bryce2471 01-12-2015 22:15

Re: pic: WCD off season chassis from 2471
 
Quote:

Originally Posted by JesseK (Post 1509151)
Do I spy shock absorbers? Or is that black ABS for spacing?

Yes, and yes. They are plastic spacers. We designed the bumper mounts that way to help insulate the frame from impact. This year's BunnyBots competition has no rule against high speed ramming, and looks to be highly violent.
Quote:

Originally Posted by RobotsThatWork (Post 1509179)
for your chain in tube design, are you using 2"x1" tubing? if so, are you using COTS sprockets? I haven't been able to fit 2 COTS sprockets into the tube. It would be great if anyone could tell me how everything was packaged together.

It was designed to use standard vex spockets, but because they were out of stock, we ended up using steel sprockets with shortened hubs. I don't know the exact layout.
Quote:

Originally Posted by Greg Woelki (Post 1509182)
I can't speak for team 2471, but these fit. A version broached for 1/2" hex is available in the drop down selection box.

Very nice, I was unaware that they were availible in hex.

RobotsThatWork 01-12-2015 23:06

Re: pic: WCD off season chassis from 2471
 
Quote:

Originally Posted by R.C. (Post 1509187)
I'm not sure how cots sprocket don't fit? Do they not fit due to the diameter or the width of the sprocket or both?

Two 16 tooth vexpro sprockets do not sit next to each other inside the 2x1x1/8 (so width). This is true for both when bearings are press-fitted, and when I use a versa bearing block. The Sprocket with Chain attached to it has a total diameter of 0.491 inches. When I put 2 back to back it would be too wide to fit inside the boxtubing. Any solutions?

I haven't looked into the 17 tooth double sprocket, but can you create a dropcenter with the larger diameter? I know the clearance is pretty slim already for 16t, but I don't know for sure with 17t.

pribusin 02-12-2015 07:59

Re: pic: WCD off season chassis from 2471
 
Very nice and clean drive base. I want our team to look into a chain-in-tube design this year but I've always wondered how you assemble the chain and sprockets in the tube :confused: Care to give me some insight on the procedure? Are there access hole on the underside? Has anyone ever done this with belts?

notmattlythgoe 02-12-2015 08:09

Re: pic: WCD off season chassis from 2471
 
Quote:

Originally Posted by pribusin (Post 1509249)
Very nice and clean drive base. I want our team to look into a chain-in-tube design this year but I've always wondered how you assemble the chain and sprockets in the tube :confused: Care to give me some insight on the procedure? Are there access hole on the underside? Has anyone ever done this with belts?

What we've done is loop the chains around the sprockets and then drop the entire thing down into the tube. Then slide the axles through the sprockets and the bearings over the axles. This is of course 100x easier if the tubes are not attached to the robot already.

If you are using 2 sprockets in the middle like we do we have a small piece of axle that we'll put through the two sprockets to hold them together during the drop and push that piece out with the final axle.

pribusin 02-12-2015 08:52

Re: pic: WCD off season chassis from 2471
 
Got it - thanks.

Are those 3" x 0.875" wheels? How are they kept from slipping off the hex shaft?

Nate Laverdure 02-12-2015 10:23

Re: pic: WCD off season chassis from 2471
 
Quote:

Originally Posted by RobotsThatWork (Post 1509206)
Two 16 tooth vexpro sprockets do not sit next to each other inside the 2x1x1/8 (so width). This is true for both when bearings are press-fitted, and when I use a versa bearing block. The Sprocket with Chain attached to it has a total diameter of 0.491 inches. When I put 2 back to back it would be too wide to fit inside the boxtubing. Any solutions?

We chose to avoid this problem by using 2 x 1.5 x 1/8 tube.

The 17t sprocket works in the 2 x 1 x 1/8 because it has a large enough pitch diameter that the chain clears the 1.125 bearing OD.

jman4747 02-12-2015 12:37

Re: pic: WCD off season chassis from 2471
 
Quote:

Originally Posted by pribusin (Post 1509254)
Got it - thanks.

Are those 3" x 0.875" wheels? How are they kept from slipping off the hex shaft?

External retaining rings: http://www.mcmaster.com/#97633a200/=102dny4

Nebster 02-12-2015 12:48

Re: pic: WCD off season chassis from 2471
 
What are you using to hold the corners of the frame together? It's not clear to me

notmattlythgoe 02-12-2015 12:52

Re: pic: WCD off season chassis from 2471
 
Quote:

Originally Posted by Nebster (Post 1509306)
What are you using to hold the corners of the frame together? It's not clear to me

There are blocks in the ladders with through bolts going through the rails.

Ty Tremblay 02-12-2015 13:00

Re: pic: WCD off season chassis from 2471
 
Quote:

Originally Posted by Nebster (Post 1509306)
What are you using to hold the corners of the frame together? It's not clear to me

http://www.team221.com/order.php?cat=15

See "Chassis Tube Connector"

Bryce2471 02-12-2015 14:46

Re: pic: WCD off season chassis from 2471
 
Quote:

Originally Posted by Nebster (Post 1509306)
What are you using to hold the corners of the frame together? It's not clear to me

This was a point of much discussion while in the design phase. We thought gussets would be stronger, but using blocks would fit with the chain in tube solution better.
Quote:

Originally Posted by notmattlythgoe (Post 1509308)
There are blocks in the ladders with through bolts going through the rails.

This is what we ended up going with, partly because the belly pan is adding a lot of corner to corner strength already.
Quote:

Originally Posted by Ty Tremblay (Post 1509309)
http://www.team221.com/order.php?cat=15

See "Chassis Tube Connector"

We did not use these, but they look to be functionally equivalent. The plastic blocks ended up being a good project for younger students to get some training and experience in.

cxcad 02-12-2015 16:01

Re: pic: WCD off season chassis from 2471
 
It would be interesting to see the FEA for the block vs gusset design. On my team the thought was that blocks were stronger because the blocks were pulling the frame members toward each other.

zinthorne 02-12-2015 21:48

Re: pic: WCD off season chassis from 2471
 
Does anyone know where to find a cad file for this?
The half inch hex

asid61 02-12-2015 23:24

Re: pic: WCD off season chassis from 2471
 
Quote:

Originally Posted by zinthorne (Post 1509427)
Does anyone know where to find a cad file for this?
The half inch hex

Because I couldn't find it, I just downloaded the round version, put a hex bore in it, re-saved it as a STEP file, and reopened it. That gave me the 1/2" hex 17t double sprocket.

zinthorne 03-12-2015 19:20

Re: pic: WCD off season chassis from 2471
 
Quote:

Originally Posted by asid61 (Post 1509452)
Because I couldn't find it, I just downloaded the round version, put a hex bore in it, re-saved it as a STEP file, and reopened it. That gave me the 1/2" hex 17t double sprocket.

I can not find the round version. Am I missing something on the website?

Greg Woelki 03-12-2015 19:42

Re: pic: WCD off season chassis from 2471
 
Quote:

Originally Posted by zinthorne (Post 1509585)
I can not find the round version. Am I missing something on the website?

I emailed them about it last year. The file can be found here.

Jacob Bendicksen 03-12-2015 22:42

Re: pic: WCD off season chassis from 2471
 
Wait, Mean Machine's not doing swerve? :D

Glad to see you're having fun and building robustly for BunnyBots -- should be a fun event.

Nebster 04-12-2015 17:43

Re: pic: WCD off season chassis from 2471
 
What are you doing for center drop? Do the sprockets you're using inside the tube have enough clearance with the walls of the tubing for a center drop? I haven't seen that done before but since you're using 1/16" tubing it could be possible.

Do you feel 1/16" walled tubing is strong enough for a traditional drive train?

Bryce2471 04-12-2015 18:06

Re: pic: WCD off season chassis from 2471
 
Quote:

Originally Posted by Jacob Bendicksen (Post 1509661)
Wait, Mean Machine's not doing swerve? :D

Glad to see you're having fun and building robustly for BunnyBots -- should be a fun event.

Yep, I'm looking forward to it! ;)
Quote:

Originally Posted by Nebster (Post 1509771)
What are you doing for center drop? Do the sprockets you're using inside the tube have enough clearance with the walls of the tubing for a center drop? I haven't seen that done before but since you're using 1/16" tubing it could be possible.

The bearing blocks we are using have their bearing holes drilled 1/16" off center. The center wheel has its block upside down compared to the outer wheels, so that gives us 0.125" drop. If it tips around too much or is too squirrely, we will flip one of the outside wheels for effectivly a 0.0625" drop. We are using 16t #25 chain sprockets.
Quote:

Do you feel 1/16" walled tubing is strong enough for a traditional drive train?
I think so, but we'll know for sure by the end of the month.
Anything that survives this BunnBot game will certainly be "strong enough for a traditional drive train"

Dunngeon 04-12-2015 18:14

Re: pic: WCD off season chassis from 2471
 
Quote:

Originally Posted by Nebster (Post 1509771)
Do you feel 1/16" walled tubing is strong enough for a traditional drive train?

Yes, 1/16 wall tubing is easily strong enough for a drivetrain.

Chris is me 07-12-2015 10:45

Re: pic: WCD off season chassis from 2471
 
Quote:

Originally Posted by Dunngeon (Post 1509778)
Yes, 1/16 wall tubing is easily strong enough for a drivetrain.

This is not a safe general statement to make at all. There are multiple loading conditions to consider, and it entirely depends on how you build your frame, what loads it is exposed to, etc.

Generally, 1/8" wall (or .1" wall) tubing is used on the driveline in order to support the bearings or internal bearing blocks better. 1/16" is too thin for a drivetrain bearing fit not supported by anything else. So regardless of strength many teams run 1/8" wall on the driveline. This could be different for systems like the VersaBlock which don't rely on the internal walls of the tube for support.

As for your cross members, I have heard in the past that teams have dealt with buckling cross members under very heavy defense when they used 1/16" 2x1 tubing. This obviously depends on the number of crossmembers used, any other cross-structural support from other mechanisms, etc. but I wouldn't just say "1/16th is easily strong enough" as a general statement.


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