pic: Another concept study

Originally Posted by Tom Ore

I did the concept study this way because it made sense for last year's game. We wanted maximum stability on the Mecanum wheels. You would have to decide what made sense based on the game. It could be wide or long - again depending on the game.

That makes a lot more sense. What are the speeds for each wheel? How much does it weigh?

[Tom Ore]

Originally Posted by SuperNerd256

That makes a lot more sense. What are the speeds for each wheel? How much does it weigh?

I believe I have the Mecanums at around 13 fps and the (3.25") traction wheels at around 7 fps.

The module we competed with last season weighed 23 lbs for each side so 46 lbs total - very heavy. This one is 18 lbs for each side for 36 lbs total. We sure could have used that 10 lbs last year. For example, we only had 1 motor driving our shooting wheel because we just didn't have the weight allowance to add a second motor.

Also, last year's version would have been nearly impossible to maintain if anything had failed. This one is very easy to maintain. The Mecanum wheel can be removed by just removing the one screw. The gear boxes have just 4 screws and the clevis pin. The CIMS stay with the frame rail when you drop the gearbox.

[JesseK]

Is there any concern that the shaft on the reduction just prior to the 3.25" traction wheel won't hold up to the stresses of having 1/4 the robot's weight on it while transferring higher torque through it?

The shaft looks like it's 0.375" even though the wheels themselves are on a 0.5" shaft (based upon bearing holes, so it's just a guess), which is the only reason I bring it up. Seems to me that if the wheels need to be on a 0.5" shaft, then that particular reduction shaft needs to also be 0.5" since it will hold the weight of the robot when the traction wheel is down. Or maybe the wheel shafts are 0.5" since the 1/8" keyway is more preferred for the wheel?

Love the render.

[Akash Rastogi]

I really like the compact packaging of your design. Do you think, just for kicks, you'd try out a vertically oriented CIM + bevel gears to have all the space in the center free? Might be fun, although not necessary.

What are the distances between mec to mec and traction to traction?

[akoscielski3]

Originally Posted by Tom Ore

I believe I have the Mecanums at around 13 fps and the (3.25") traction wheels at around 7 fps.

The module we competed with last season weighed 23 lbs for each side so 46 lbs total - very heavy. This one is 18 lbs for each side for 36 lbs total. We sure could have used that 10 lbs last year. For example, we only had 1 motor driving our shooting wheel because we just didn't have the weight allowance to add a second motor.

Also, last year's version would have been nearly impossible to maintain if anything had failed. This one is very easy to maintain. The Mecanum wheel can be removed by just removing the one screw. The gear boxes have just 4 screws and the clevis pin. The CIMS stay with the frame rail when you drop the gearbox.

You may want to consider making the macanum's slower. 13 FPS will not give you a lot of torque on the wheels that is needed to make your roboto strafe. In 2011 we used CIMple boxes on our 6inch mecanum's and we were unable to strafe. I may be wrong because I am not a Mecanum master or anything, but this is just from my experience.

Originally Posted by akoscielski3

You may want to consider making the macanum's slower. 13 FPS will not give you a lot of torque on the wheels that is needed to make your roboto strafe. In 2011 we used CIMple boxes on our 6inch mecanum's and we were unable to strafe. I may be wrong because I am not a Mecanum master or anything, but this is just from my experience.

Yeah, but you forget to mention only 3 of your wheels were on the ground at once. Aaron =/= trusted source on mecanums.

[Tom Ore]

Originally Posted by akoscielski3

You may want to consider making the macanum's slower. 13 FPS will not give you a lot of torque on the wheels that is needed to make your roboto strafe. In 2011 we used CIMple boxes on our 6inch mecanum's and we were unable to strafe. I may be wrong because I am not a Mecanum master or anything, but this is just from my experience.

When we run a simple Mecanum drivetrain we run at around 9 fps. This seems to be about as fast as you can go and still get maximum pushing force from the Mecanums.

Last year we ran at about 10.7 fps and had no trouble. With the traction wheels we don't need to worry about the Mecanum's lower pushing force so we can run faster.

This concept is at 13 fps but that doesn't mean we would ever build it that way. Our driver said he didn't go to full speed at 10.7 fps very often so faster than that would have be a need driven by the game.

[Garret]

I love this design (and the detail in the model), but I cannot see how are you going to make the hollow round housing like that for the traction wheels? I am sure I am missing something but it looks like it is just machined from one solid block of aluminum.

[Tom Ore]

Originally Posted by Garret

I love this design (and the detail in the model), but I cannot see how are you going to make the hollow round housing like that for the traction wheels? I am sure I am missing something but it looks like it is just machined from one solid block of aluminum.

Yeah - that one is a bit messy. I have it designed as a tube with end plates welded on and then machined.

[Greg Needel]

I would recommend changing the setup so that the pivot is on the traction wheel and not the mechanum. The reason is that you will see a large bending force on your pivot if you are in traction mode and you get pushed from the side. The distance from your traction wheel to the pivot will act as a moment arm and can reek havoc. Now you are using box tubing which has a great bending strength, but you are also using that same box tubing to house a gearbox, so even a slight bend can really foul up the works.

This is a lesson learned from experience on 148. Take a look at the differences in the drive train between 2010 and 2011.

[Nemo]

I've been studying the details of this render in several sittings, and I'm still in the process of absorbing some of them. This is really neat stuff. Thanks for posting!

It looks to me like the speed on the traction wheels would be something like 3.5 times slower than the mecanums, based on wheel size difference and a guess that the traction wheel's gearing is about 2:1.

[Tom Ore]

Originally Posted by Nemo

I've been studying the details of this render in several sittings, and I'm still in the process of absorbing some of them. This is really neat stuff. Thanks for posting!

It looks to me like the speed on the traction wheels would be something like 3.5 times slower than the mecanums, based on wheel size difference and a guess that the traction wheel's gearing is about 2:1.

The speed difference is mostly due to the size difference of the wheels. The CIM drives the center gear. The Mecanum wheel is driven off a second reduction going one way and the traction wheel is driven off the #25 chain and a second reduction going the other way. (I don't have the exact gear ratios handy - must have overwritten the spreadsheet.)

[Nemo]

Ah, yes. I missed the fact that the traction wheel doesn't get the second stage reduction that the mecanum wheel gets.