pic: Madtown Marauders DT of DOOM-2

[R.C.]

loading photo ...

Looks like a fun 0.1 design. Keep tweaking it, and you could have something there...

Suggestions:

-Change your CIM weight. They're around 2.5lbs (someone else probably has a more accurate weight)
-You don't need a motor to pull up the front. Spend some time with cardboard and straws, you can find some much lower profile frames that can make this happen.
-If you make the "bending" point centered on your middle wheel's axle, you won't need crazy shenanigans for tensioning.
-Keep playing with this!

[Cory]

Originally Posted by CraigHickman

Suggestions:

-Change your CIM weight. They're around 2.5lbs (someone else probably has a more accurate weight)

2.75 lbs ea.

[JVN]

Originally Posted by Cory

2.75 lbs ea.

Some of us use 3 lbs for our estimates, so we're pleasantly surprised when we weigh the thing.

[R.C.]

Originally Posted by Cory

2.75 lbs ea.

Yeah, scratch the weight. Finals did fry my brains. Grrr. Maybe the motors aren't needed? Umm.

[roboticWanderor]

Sweet!, nice to see another flex chassis out there...
I would say to put another support onto your super structure there. Maybe about where your gearboxes are now. Then you can support the upper part of your gearboxes better too! Be careful with the center of gravity here. If your springs are pushing up on the front of your chassis, and most of the weight is in the back, your gonna have some difficult tipping problems. Consider making triangular support for the springs near to the front of the chassis, instead of all the way in the back.
I <3 the idea! keep it coming!

[Akash Rastogi]

Originally Posted by roboticWanderor

Sweet!, nice to see another flex chassis out there...
I would say to put another support onto your super structure there. Maybe about where your gearboxes are now. Then you can support the upper part of your gearboxes better too! Be careful with the center of gravity here. If your springs are pushing up on the front of your chassis, and most of the weight is in the back, your gonna have some difficult tipping problems. Consider making triangular support for the springs near to the front of the chassis, instead of all the way in the back.
I <3 the idea! keep it coming!

Thanks a lot for the support guys.

Also some reference should be made to 418 for this simple design that we hope to tweak.

http://www.chiefdelphi.com/media/photos/32055
Keep the comments coming guys. Much appreciated.

*goes and tags pic with frc418*

[FourPenguins]

Interesting idea. I'd love to see models of it (I can't make out some finer details in that render). I like the idea, but I'm seeing a few issues:
-See if you can figure out how to do this without motorizing the joint. This might be a case for pneumatics, but the ideal solution would be to design it in such a way that the natural action of the joint is to flex upward if you hit an obstacle. I'm not sure I can explain it better than that.
-Gear ratios. What's the ratio and, what kind of gears (material, pitch, etc).
-How long is this DT? Are you accounting for the scrub on the outer wheels? Seems like a good place for omnis.
-What's holding this thing together? Rivets? Screws? Welds?

I'll have more questions, but I'm afraid I'll start getting into minutia. Good Rev0. I can't wait to see Rev1.

[Akash Rastogi]

Originally Posted by FourPenguins

Interesting idea. I'd love to see models of it (I can't make out some finer details in that render). I like the idea, but I'm seeing a few issues:
-See if you can figure out how to do this without motorizing the joint. This might be a case for pneumatics, but the ideal solution would be to design it in such a way that the natural action of the joint is to flex upward if you hit an obstacle. I'm not sure I can explain it better than that.
-Gear ratios. What's the ratio and, what kind of gears (material, pitch, etc).
-How long is this DT? Are you accounting for the scrub on the outer wheels? Seems like a good place for omnis.
-What's holding this thing together? Rivets? Screws? Welds?

I'll have more questions, but I'm afraid I'll start getting into minutia. Good Rev0. I can't wait to see Rev1.

Some things that we considered:

We wanted to keep weight down in case we actually decided to use this frame and considered the weight of the new control system (btw Ed, Mr. Marvin is not too happy about it). Pneumatics would have to include the compressor and tanks. Not knowing what restrictions in terms of size and weight will be placed this year, we wanted to stay conservative with the weight, thus the pneumatics were opted out for now. We figure that if we really want to add pneumatics then we can shave weight by lightening the frame and shaving off weight in other areas. As Craig helped us out in the design process, we learned to keep weight in mind as we designed and not at the end. In the end, the structural integrity won't be compromised for weight. Lightening and pneumatics can come later is what my main point is.

This frame is fully welded. Yes we need supports for the upper tier of the frame.

Btw one thing we're considering is hidden ball-casters. Not sure how to explain it right now but we'll have some more pics up later in the week.

For now...RC has finals, and I have NHS application =P Stupid school...

[Vikesrock]

Originally Posted by rc_cola1323

Due to the game clues and previous years, we wanted to make a DT that could climb ramps with ease and not tip while going up & down the ramps.

Perhaps I'm missing something, but how does this design help prevent tipping when going UP a ramp? If anything this seems like it would be worse for going up a ramp than a typical 6 wheel. As I understand it when the full length of the robot is on the incline the chassis would lie in a single plane. This means your gas struts are attempting to tip you over backwards right?

[Akash Rastogi]

Originally Posted by Vikesrock

Perhaps I'm missing something, but how does this design help prevent tipping when going UP a ramp? If anything this seems like it would be worse for going up a ramp than a typical 6 wheel. As I understand it when the full length of the robot is on the incline the chassis would lie in a single plane. This means your gas struts are attempting to tip you over backwards right?

This is where the locked motor in the front comes in. Maaaan, we need to finish that CAD...=P

Can't explain it verbally that well at the moment, need the picture in front of me.

[artdutra04]

Unless you are using two sets of chains, as the front module goes up and down, the center to center distance between the center wheel axle and the front axle will change. If a single section of chain is used, then this will create tensioning nightmares (sans dynamic tensioning system), as well as issues with clearance heights (if the front dips down, the chain will probably hit the corner of the ramp).

A much simpler solution would be to make the pivot axle concentric with the center axle of the drive train and use a single loop of roller chain.

Also, by using an active system to adjust the angle of the front pivot module, this adds a lot of complexity, and slows down the response time of the system (as it has to sense->think->respond). The robot must get to the ramp, "know" the ramp exists, change the front pivot angle, and then proceed up the ramp.

Compared to a well designed rigid frame robot (with a low and centered center of gravity), which can just gun it up the ramp without any necessary change in the state of the machine, an active flexible frame might actually slow down the performance of the system.

[Akash Rastogi]

Sorry folks, pictures got posted twice for some reason. Could a mod please delete the 3 extras that don't have writing? Thanks.

[R.C.]

Originally Posted by artdutra04

Unless you are using two sets of chains, as the front module goes up and down, the center to center distance between the center wheel axle and the front axle will change. If a single section of chain is used, then this will create tensioning nightmares (sans dynamic tensioning system), as well as issues with clearance heights (if the front dips down, the chain will probably hit the corner of the ramp).

A much simpler solution would be to make the pivot axle concentric with the center axle of the drive train and use a single loop of roller chain.

Also, by using an active system to adjust the angle of the front pivot module, this adds a lot of complexity, and slows down the response time of the system (as it has to sense->think->respond). The robot must get to the ramp, "know" the ramp exists, change the front pivot angle, and then proceed up the ramp.

Compared to a well designed rigid frame robot (with a low and centered center of gravity), which can just gun it up the ramp without any necessary change in the state of the machine, an active flexible frame might actually slow down the performance of the system.

Art, great comments. What we were thinking: since the new camera came out and if there is a light above the ramp. That we could have the robot sense on its own and start lifting before it hits the ramp or it could be driver activated and then the encoders could tell whether it is up or down the ramp.

BTW, we as a team are going to be heavily depending on sensors this year. A lot of our crazy offseason ideas depend on them. The reason for not making it coecentric with the middle is because it has an adjustable drop. There will be two sets of chain running to the front.

As for a rigid frame, the reason we did this was because we had a solid DT at nationals for the past few years. We could previously climb ramps easily. The problem we noticed was that while climbing the ramp was that on four of our wheels were in contact. The front and the back and noticed that a couple of our regional matches, we tipped right there. With this DT, at any point we will have all 6 wheels in contact with the ramp and our cg will be closer to the front. The next point where a rigid drive can tip is when you are climbing and the middle wheel hits the top of the ramp. Through some of the older vids, I saw this was also a point in which bots tipped. So this is why this DT flexes both ways. Hope that answeres a lot of questions.

[R.C.]

http://video.google.com/videoplay?do...49860332436870

Vid shows what I mean! Pretty funny vid!