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Deke 29-10-2014 00:20

pic: Concept 6W Drive Train
 

Christopher149 29-10-2014 00:21

Re: pic: Concept 6W Drive Train
 
Any particular reason for cutting off the corners? Does it help much in giving more area for a given perimeter?

Definitely have to concur that simple is good.

Munchskull 29-10-2014 00:23

Re: pic: Concept 6W Drive Train
 
Looks solid.

asid61 29-10-2014 00:51

Re: pic: Concept 6W Drive Train
 
Looks a little too solid IMO. There's a ton of 1x1 on there.
However, 34 lbs is still pretty light for six cims (actually that's very light) so adding in a shifting gearbox would make good use of that drivetrain I think. It's only a couple pounds more, and allows for safe top speeds of 18fps+ without worrying about main breaker trips.

mman1506 29-10-2014 01:00

Re: pic: Concept 6W Drive Train
 
What makes this drive train better than a kitbot with nitrile treads and 6 cim gearboxes? If you want to keep it simple why not go that route?

Andrew Lawrence 29-10-2014 01:04

Re: pic: Concept 6W Drive Train
 
How is that any simpler than this?


AdamHeard 29-10-2014 01:13

Re: pic: Concept 6W Drive Train
 
Quote:

Originally Posted by Andrew Lawrence (Post 1406258)
How is that any simpler than this?


It's not.

asid61 29-10-2014 01:21

Re: pic: Concept 6W Drive Train
 
Oh I just noticed:
Your main gearbox shaft is attached to the out frame member. If the outer frame becomes damaged in a collision and bends a little, it will damage the efficiency of the gearbox, and possibly render you immobile on one side.
Also, what's the reasoning behind cutting the corners? It seems like extra work to me.

EricH 29-10-2014 01:34

Re: pic: Concept 6W Drive Train
 
Quote:

Originally Posted by Andrew Lawrence (Post 1406258)
How is that any simpler than this?

Quote:

Originally Posted by AdamHeard (Post 1406259)
It's not.

They are trying to work within their existing resources, and this is a simple design that fits within those resources. I would probably find it reasonable to assume that they don't anticipate having the funding to buy Versa, or to buy Versa and still do X, Y, and Z that they want to or need to do. Or that they're one of the teams that prefers making over buying (there are a few out there).

Is a WCD simpler? Maybe. But if you're doing all the machining for it, there are some advantages to NOT doing a WCD (like having more time!). Even if you are thinking of buying one, there could still be advantages to not doing one (dead-axle setups tend to be a trifle easier than live-axle setups in terms of manufacturing, something about no keyway or hex).

Dunngeon 29-10-2014 01:42

Re: pic: Concept 6W Drive Train
 
Are the gussets at the corners supposed to be seperate strips or angle iron? If they are seperate strips, it looks like a hard hit to the upper member could severely bend it inwards.

Edit: The upper 1x1 above the wheels

Andrew Lawrence 29-10-2014 01:44

Re: pic: Concept 6W Drive Train
 
Quote:

Originally Posted by EricH (Post 1406262)
They are trying to work within their existing resources, and this is a simple design that fits within those resources. I would probably find it reasonable to assume that they don't anticipate having the funding to buy Versa, or to buy Versa and still do X, Y, and Z that they want to or need to do. Or that they're one of the teams that prefers making over buying (there are a few out there).

Is a WCD simpler? Maybe. But if you're doing all the machining for it, there are some advantages to NOT doing a WCD (like having more time!). Even if you are thinking of buying one, there could still be advantages to not doing one (dead-axle setups tend to be a trifle easier than live-axle setups in terms of manufacturing, something about no keyway or hex).

A full versachassis can get expensive, I'll admit that, but just using some of the parts can greatly simplify this design and make it not only more effective, but more reliable as well. You don't need to buy an entire drivetrain setup, but using what your resources will allow can greatly simplify things.

You don't need to break bank on COTS parts to make a great drivetrain, but ignoring the cost effective resources available to teams isn't the answer either.

T-Dawg 29-10-2014 02:02

Re: pic: Concept 6W Drive Train
 
Is there a particular reason why the corners of the chassis are cut off?
The only reason I can think of is if you're trying to make the chassis fit within the 112 inch frame perimeter.
Otherwise, I don't see a structural benefit of cutting the corners off.

Spoam 29-10-2014 02:14

Re: pic: Concept 6W Drive Train
 
Quote:

Originally Posted by T-Dawg (Post 1406265)
Is there a particular reason why the corners of the chassis are cut off?
The only reason I can think of is if you're trying to make the chassis fit within the 112 inch frame perimeter.
Otherwise, I don't see a structural benefit to cutting the corners off.

If I had to guess it would be that they're trying to keep all the 1x1s the same length for convenience? Then cut ends to keep it flush. Personally though if that's it then I might rather have the extra support from corners.

JesseK 29-10-2014 06:32

Re: pic: Concept 6W Drive Train
 
(nvm)

Deke 29-10-2014 12:45

Re: pic: Concept 6W Drive Train
 
Quote:

Originally Posted by Christopher149 (Post 1406253)
Any particular reason for cutting off the corners? Does it help much in giving more area for a given perimeter?

It gave about 4.5" inches in perimeter back, so the frame is at 28 x 30 with ~ .5" to spare. The small increase in bumper complexity seems worth the extra 4.5".

Quote:

Originally Posted by asid61 (Post 1406256)
However, 34 lbs is still pretty light for six cims (actually that's very light) so adding in a shifting gearbox would make good use of that drivetrain I think. It's only a couple pounds more, and allows for safe top speeds of 18fps+ without worrying about main breaker trips.

I think you are right depending on the game, but I would like to avoid the added complexity and cost if possible. Most games don't require 18 fps imo.

Quote:

Originally Posted by mman1506 (Post 1406257)
What makes this drive train better than a kitbot with nitrile treads and 6 cim gearboxes? If you want to keep it simple why not go that route?

Not much, it helps with bumper support and added area for mechanisms. I also like how the gear box gets packaged. We like to build as much as we can in house. The kitbot wouldn't have the students machining the components.

Quote:

Originally Posted by EricH (Post 1406262)
They are trying to work within their existing resources, and this is a simple design that fits within those resources. I would probably find it reasonable to assume that they don't anticipate having the funding to buy Versa, or to buy Versa and still do X, Y, and Z that they want to or need to do. Or that they're one of the teams that prefers making over buying (there are a few out there).

Is a WCD simpler? Maybe. But if you're doing all the machining for it, there are some advantages to NOT doing a WCD (like having more time!). Even if you are thinking of buying one, there could still be advantages to not doing one (dead-axle setups tend to be a trifle easier than live-axle setups in terms of manufacturing, something about no keyway or hex).

You are correct with how we are thinking. I would argue once you add bumper support and interfaces for mechanisms to a WCD, it is more complex. This structure immediately supports the bumpers and provides a little better locations for mechanisms imo. We also try to build as much as we can in house. We are fortunate enough to use the manual lathes and manual mills in the school to build.

Quote:

Originally Posted by asid61 (Post 1406260)
Oh I just noticed:
Your main gearbox shaft is attached to the out frame member. If the outer frame becomes damaged in a collision and bends a little, it will damage the efficiency of the gearbox, and possibly render you immobile on one side.
Also, what's the reasoning behind cutting the corners? It seems like extra work to me.

With the bumper outside of the frames protecting them, I am not to worried about it. The dead axles also act as cross members supporting the outside lower beam. If the upper beam needs more support, cross members could be easily added. The corners being removed reduces the frame perimeter, allowing more length or width to be added.

Quote:

Originally Posted by T-Dawg (Post 1406265)
Is there a particular reason why the corners of the chassis are cut off?
The only reason I can think of is if you're trying to make the chassis fit within the 112 inch frame perimeter.
Otherwise, I don't see a structural benefit of cutting the corners off.

Using angle pieces to connect the beams, the corners have no structural benefit as they carry no load. Now if top and bottom gussets were used, then additional structural support would be provided. The statics and solid mechanics of the structure make the corners the strongest part. Angle pieces are susceptible to torsional loads, but the internal beams stiffen any torsional loading the structure would take. If you draw up a free body diagram it becomes clearer.



I can't take much credit for this, I just copied it from 469 with a few tweaks. I would say it worked pretty well for them, world championship and such things. Not sure any one was questioning the reliability of their drive train, hats off to them, they are an inspiration to all teams.

AdamHeard 29-10-2014 13:42

Re: pic: Concept 6W Drive Train
 
Quote:

Originally Posted by Infinity2718 (Post 1406297)
You are correct with how we are thinking. I would argue once you add bumper support and interfaces for mechanisms to a WCD, it is more complex. This structure immediately supports the bumpers and provides a little better locations for mechanisms imo. We also try to build as much as we can in house. We are fortunate enough to use the manual lathes and manual mills in the school to build.

We mill our WCD siderails on a manual mill for reference.

Also, bumper support on a WCD doesn't need to be complicated.

As for interfacing to mechanisms, how is it more difficult with a WCD?

Oblarg 29-10-2014 13:57

Re: pic: Concept 6W Drive Train
 
Quote:

Originally Posted by AdamHeard (Post 1406303)
Also, bumper support on a WCD doesn't need to be complicated.

Are there really no problems with only having a bumper support that low off the ground? As far as I can tell, that's going to be contacting the bumper well below-center.

AdamHeard 29-10-2014 14:00

Re: pic: Concept 6W Drive Train
 
Quote:

Originally Posted by Oblarg (Post 1406306)
Are there really no problems with only having a bumper support that low off the ground? As far as I can tell, that's going to be contacting the bumper well below-center.

No problems at all.

We make one piece bumpers with strong corners. Any moment trying to bend the bumper over is reacted by the adjacent section.

AdamHeard 29-10-2014 14:12

Re: pic: Concept 6W Drive Train
 
Here is a good exercise...

Design a few drivetrains, give them all a good honest effort (otherwise you're just wasting your own time and lying to yourself).

While designing, do your best to optimize all the variants for your resources. Publicly post them for review. Invite BRUTAL commentary, take this in stride and incorporate the feedback that makes sense. If you have enough experienced students, mentors and possible sponsors that can offer review, the public part could be skipped.

At the end do a fair comparison of the different options on the criteria that matter to you; fab time, difficulty, cost, etc...

Going into nearly every season we have designed a swerve, west coast, plate sandwich drive and the last few years butterfly/octonum. We constantly reassess them to better suit our ever changing resources, and compare them on the merits we care about.

It's unreasonable to anecdotally link it to a drive a good team ran. Using that logic ANY drive can be proven to be the best.

Oblarg 29-10-2014 14:20

Re: pic: Concept 6W Drive Train
 
Quote:

Originally Posted by AdamHeard (Post 1406307)
No problems at all.

We make one piece bumpers with strong corners. Any moment trying to bend the bumper over is reacted by the adjacent section.

Ah. We've never done one-piece bumpers. We probably should try it out, it seems. Thanks.

Edit: Out of curiosity, how do you do the corners on your bumpers?

Deke 29-10-2014 15:53

Re: pic: Concept 6W Drive Train
 
Quote:

Originally Posted by AdamHeard (Post 1406303)
We mill our WCD siderails on a manual mill for reference.

Also, bumper support on a WCD doesn't need to be complicated.

As for interfacing to mechanisms, how is it more difficult with a WCD?

We ran bumper supports similar to that and milled the rails manually. Our wc drive performed awesome last year, no issues. By the end of the season the bumpers were all smashed in at the top from no framing support and became more difficult to install, that's my beef with it. It also took a bit to get framing supported for mechanisms, there just isn't alot of framing on a wcd. Most of the framing required alot of attention throughout competitions. It's all fairly minor complaints, i don't have an issue doing a wcd again but i think a different approach could free up resources for us.

Quote:

Originally Posted by AdamHeard (Post 1406309)
Here is a good exercise...

Design a few drivetrains, give them all a good honest effort (otherwise you're just wasting your own time and lying to yourself).

While designing, do your best to optimize all the variants for your resources. Publicly post them for review. Invite BRUTAL commentary, take this in stride and incorporate the feedback that makes sense. If you have enough experienced students, mentors and possible sponsors that can offer review, the public part could be skipped.

At the end do a fair comparison of the different options on the criteria that matter to you; fab time, difficulty, cost, etc...

Going into nearly every season we have designed a swerve, west coast, plate sandwich drive and the last few years butterfly/octonum. We constantly reassess them to better suit our ever changing resources, and compare them on the merits we care about.

It's unreasonable to anecdotally link it to a drive a good team ran. Using that logic ANY drive can be proven to be the best.

I'm confused who this information is for, isn't this the exercise we are going through? I enjoy the commentary and feedback, I am hoping it helps. I'd prefer feedback on pros and cons/strengths and weaknesses, versus design process rhetoric.

AdamHeard 29-10-2014 16:02

Re: pic: Concept 6W Drive Train
 
Quote:

Originally Posted by Infinity2718 (Post 1406322)
We ran bumper supports similar to that and milled the rails manually. Our wc drive performed awesome last year, no issues. By the end of the season the bumpers were all smashed in at the top from no framing support and became more difficult to install, that's my beef with it. It also took a bit to get framing supported for mechanisms, there just isn't alot of framing on a wcd. Most of the framing required alot of attention throughout competitions. It's all fairly minor complaints, i don't have an issue doing a wcd again but i think a different approach could free up resources for us.

Can you post your frame and bumper setup from season?


Quote:

Originally Posted by Infinity2718 (Post 1406322)
I'm confused who this information is for, isn't this the exercise we are going through? I enjoy the commentary and feedback, I am hoping it helps. I'd prefer feedback on pros and cons/strengths and weaknesses, versus design process rhetoric.

It's for anyone willing to read it. Is this the only drive you are developing this fall, or are you also re-designing your WCD to have something to compare to?

Maybe look at vexpro drive in a day, and modifications (or stock) you could do there. I know 558 was really happy with, and just posted about it.

Deke 29-10-2014 17:42

Re: pic: Concept 6W Drive Train
 
Quote:

Originally Posted by AdamHeard (Post 1406324)
Can you post your frame and bumper setup from season?




Quote:

Originally Posted by AdamHeard (Post 1406324)
It's for anyone willing to read it. Is this the only drive you are developing this fall, or are you also re-designing your WCD to have something to compare to?

Maybe look at vexpro drive in a day, and modifications (or stock) you could do there. I know 558 was really happy with, and just posted about it.

Not really redesigning last year, just adding it to the considerations.

I do like the layout of the day in a drive, and actually all of the cots drives are pretty good. Our team prefers to build as much as we can, and would like some flexibility for perimeter changes.

I did read the 558 beyond the inspection when it came out, and they did say they wished they had more bracing to make the chassis more rigid.

BrendanB 29-10-2014 17:52

Re: pic: Concept 6W Drive Train
 
Quote:

Originally Posted by Andrew Lawrence (Post 1406264)
A full versachassis can get expensive, I'll admit that, but just using some of the parts can greatly simplify this design and make it not only more effective, but more reliable as well. You don't need to buy an entire drivetrain setup, but using what your resources will allow can greatly simplify things.

You don't need to break bank on COTS parts to make a great drivetrain, but ignoring the cost effective resources available to teams isn't the answer either.

I smell no bias here. Nope.

WCD and even the Versachassis is not the answer for every team.

AdamHeard 29-10-2014 18:18

Re: pic: Concept 6W Drive Train
 
Quote:

Originally Posted by Infinity2718 (Post 1406336)


Not really redesigning last year, just adding it to the considerations.

What didn't work out well on the framing for bumpers on this?

Hard to tell from just a top down picture, but assuming the supports between the wheels were at the correct height to support the bottom of the bumpers this should've worked out decent.

Was it a mounting issue? Did they have too much slop/play? Was it a once piece bumper?

Were you happy with the drive otherwise, and are just trying to solve the bumper issue?

z_beeblebrox 29-10-2014 18:39

Re: pic: Concept 6W Drive Train
 
AdamHeard, where can I find good pictures or descriptions of the bumper and bumper mount design that you guys use?

Deke 29-10-2014 18:46

Re: pic: Concept 6W Drive Train
 
Quote:

Originally Posted by AdamHeard (Post 1406342)
What didn't work out well on the framing for bumpers on this?

Quote:

Originally Posted by Infinity2718 (Post 1406322)
By the end of the season the bumpers were all smashed in at the top from no framing support and became more difficult to install, that's my beef with it.

Quote:

Originally Posted by AdamHeard (Post 1406342)
Hard to tell from just a top down picture, but assuming the supports between the wheels were at the correct height to support the bottom of the bumpers this should've worked out decent.

Was it a mounting issue? Did they have too much slop/play? Was it a once piece bumper?

Were you happy with the drive otherwise, and are just trying to solve the bumper issue?

The mounting could have been better, we used wing nuts with bolts through the bumper. It was a one piece bumper.

I have a handful of minor complaints: center live axle getting bent and wobbly a few times (took a while to replace, the dead axles performed better imo), bearing block plates hard to get at to loosen, gear box cantilevering off a few bolts seemed sloppy (, tensioners added construction and wheel maintenance time, if we got tipped the drive would sit on its frame edge and lose traction. Other than that and other things noted in this thread, it was pretty sexy.

asid61 29-10-2014 22:25

Re: pic: Concept 6W Drive Train
 
In recenty memory, there have been:
2010: Giant bumps made moving fast only possible in the individual sections
2011: Open space for driving. Very fast driving was useful.
2012: Open space for driving, except when passing over the low barrier.
2013: Open space barring the pyramids.
2014: Totally open space. 1678 was geared for 22fps according to their website.
If you feel that the cost/complexity is beyond the team's scope, sigle speed is more than fine. But when running 6 cims, be prepared to add in some kind of anti-breaker tripping code anyway just in case.

Brandon_L 29-10-2014 23:53

Re: pic: Concept 6W Drive Train
 
Quote:

Originally Posted by Infinity2718 (Post 1406347)
Center live axle getting bent and wobbly a few times (took a while to replace, the dead axles performed better imo)

Usually you'd use a high strength aluminum alloy here or even steel, what did your team use?

Quote:

Originally Posted by Infinity2718 (Post 1406347)
bearing block plates hard to get at to loosen

This seems to be a result of where you're running your chains from. On most of the WCDs I've seen the chain runs are actually on the inside of the robot with the chains coming off a sprocket inside of the gearbox itself. Of course you can really do it any way you want, but as a result of sprockets on the outside yes your plates will be more difficult to get to.

Quote:

Originally Posted by Infinity2718 (Post 1406347)
gear box cantilevering off a few bolts seemed sloppy

What about it seemed sloppy?

With all that being said, 1x1 drives are perfectly valid. The only thing I would comment on is that some of your upper structure seems unnecessary. Maybe you're using the outer upper level for bumper supports, which is fine, but the inner upper level that holds up the gearbox could probably be replaced with something like this. Depends on what you were trying to achieve with it.

Also, I'm not sure if I would trust those vertical gussets you have going on with impacts. But I could be wrong. Who knows.

philso 30-10-2014 01:17

Re: pic: Concept 6W Drive Train
 
You may want to consider what would happen if this chassis is used in a game that allowed high speed and hard hitting, like this years. There is the possibility that the vertical angle pieces in the corners deform when hit on that corner causing the two outermost side tubes to move backward. Since it looks like your axles are supported by the lower side tube, they may bind in the bearing blocks and/or cause the robot to not drive straight.

Deke 30-10-2014 07:14

Re: pic: Concept 6W Drive Train
 
Shafts were 7075 1/2 hex.

Sloppy is probably the wrong description, more flexible than anything. The top of the side plates had some decent flex in direction changes.

I like the suggestion for removing the upper inner support, ithink that could easily change depending on the game and mechanisms required.

Quote:

Originally Posted by philso (Post 1406397)
You may want to consider what would happen if this chassis is used in a game that allowed high speed and hard hitting, like this years. There is the possibility that the vertical angle pieces in the corners deform when hit on that corner causing the two outermost side tubes to move backward. Since it looks like your axles are supported by the lower side tube, they may bind in the bearing blocks and/or cause the robot to not drive straight.

That's a good point, it would help to add some reinforcement to support the lower beam alignment.


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