pic: FRC488 - 80/20 Drive Train

[Zflash]

Looks solid. Do you have an estimate of what it wieghs in it's current design state? Also the question I really have is are you using two servos to shift the dewalts, if so have you done any testing with it?

[Madison]

Originally Posted by Zflash

Looks solid. Do you have an estimate of what it wieghs in it's current design state? Also the question I really have is are you using two servos to shift the dewalts, if so have you done any testing with it?

It's 22.25 lbs. as shown. It's missing chains, obviously, and some brackets and fasteners required for mounting the gearboxes. It'll probably hit 28-30 lbs. with those things and with an ABS base for control system components.

We had some trouble shifting the DeWalt gearboxes with a single servo last season, so we've been thinking about adding the second to each. We haven't tried it yet.

[sdcantrell56]

How are the bearing blocks held in place on the 80-20? Other then that it looks like s very good simple drivetrain. I guess you didn't see a need for the second set of cims last season?

[Madison]

Originally Posted by sdcantrell56

How are the bearing blocks held in place on the 80-20? Other then that it looks like s very good simple drivetrain. I guess you didn't see a need for the second set of cims last season?

The bearing blocks are 80/20 pivot pieces. We're going to open the pivot hole from 1/4" to 1/2". They tie in to the 80/20 from the top using their existing mounting holes. They're part no. 4181.

We had some trouble shifting the Dewalts and made no use of 3rd gear last year, so we were a bit slower than I'd hoped. As always, the game may change what we put into the drive, but if we can avoid pushing matches again, we'll probably stick with 1 CIM per side. Similarly, it's shown with four traction wheels, but we may again use just two and put omniwheels back onto the corners.

We expect to have our hands full with the new cRio system, so anywhere else that we can remove complexity, we'll do it.

[Lowfategg]

Originally Posted by Madison

The bearing blocks are 80/20 pivot pieces. We're going to open the pivot hole from 1/4" to 1/2". They tie in to the 80/20 from the top using their existing mounting holes. They're part no. 4181.

We had some trouble shifting the Dewalts and made no use of 3rd gear last year, so we were a bit slower than I'd hoped. As always, the game may change what we put into the drive, but if we can avoid pushing matches again, we'll probably stick with 1 CIM per side. Similarly, it's shown with four traction wheels, but we may again use just two and put omniwheels back onto the corners.

We expect to have our hands full with the new cRio system, so anywhere else that we can remove complexity, we'll do it.

I would never mount bearing blocks to 80/20 using the T-slots. They slip way to easy under the strain that is being placed on them. Drill through the 80/20 and bolt them right into it.

Thats just my opinion.

[Madison]

Originally Posted by Lowfategg

I would never mount bearing blocks to 80/20 using the T-slots. They slip way to easy under the strain that is being placed on them. Drill through the 80/20 and bolt them right into it.

Thats just my opinion.

Well, the simplicity of this design is that 80/20's slot system substitutes for chain tensioning mechanisms. If we were to eliminate that advantage, we'd change the design entirely.

We haven't used 80/20 much, but have had success with it staying where we put it as long as the bolts are properly tightened.

[Lowfategg]

Originally Posted by Madison

Well, the simplicity of this design is that 80/20's slot system substitutes for chain tensioning mechanisms. If we were to eliminate that advantage, we'd change the design entirely.

We haven't used 80/20 much, but have had success with it staying where we put it as long as the bolts are properly tightened.

Well I guess then the T-slots are nice to have for that, but make sure to keep up with those screws. My experiences with 80/20 last year were not that great, but some people like it.

[AndyB]

Madison, this looks like a very simple, easy to put together design.

The only weaknesses are, in my eyes, angular clearance for ramps.

Assuming the wheels are centered at 3/4" above the 8020, and positioned about 3.5" back from the inside of the front rail, that only gives you about 17 degrees of angular clearance. But for a flat-field application, this looks like a very nice drive that you could easily modify at any point.

[qwertyuiop[]\]

Why do you need a six wheel robot if you are using omni's? also watch out, 8020 bots get heavy, fast. on our 2006 robot we essentially built our entire robot out of 8020. There is alot of un necessary weight in 8020. Do you really need all for slots in the metal? it is very strong and is very fast, so if your going for a fast build this is what you want. Also, what size 8020 are you using, the inch or half inch?

[Cory]

Originally Posted by qwertyuiop[]\

Why do you need a six wheel robot if you are using omni's? also watch out, 8020 bots get heavy, fast. on our 2006 robot we essentially built our entire robot out of 8020. There is alot of un necessary weight in 8020. Do you really need all for slots in the metal? it is very strong and is very fast, so if your going for a fast build this is what you want. Also, what size 8020 are you using, the inch or half inch?

8020 itself is not actually particularly heavy. A very long time ago I did the math to see for myself and the 1010 series is almost exactly the same weight as 1x1x0.125" Al tube. The weight difference comes from all the connectors, t-nuts, and fasteners.

[Madison]

Originally Posted by AndyB

Madison, this looks like a very simple, easy to put together design.

The only weaknesses are, in my eyes, angular clearance for ramps.

Assuming the wheels are centered at 3/4" above the 8020, and positioned about 3.5" back from the inside of the front rail, that only gives you about 17 degrees of angular clearance. But for a flat-field application, this looks like a very nice drive that you could easily modify at any point.

Yeah, this can clear a 17* angle, but nothing greater. If there's anything steeper, we'll figure out how to deal with it as a special circumstance -- or we'll turn the chassis upside down.

Originally Posted by qwertyuiop[]\

Why do you need a six wheel robot if you are using omni's? also watch out, 8020 bots get heavy, fast. on our 2006 robot we essentially built our entire robot out of 8020. There is alot of un necessary weight in 8020. Do you really need all for slots in the metal? it is very strong and is very fast, so if your going for a fast build this is what you want. Also, what size 8020 are you using, the inch or half inch?

6WD does a bit better at getting over obstacles -- whether those be field elements or game pieces. Again, the simplicity here is that we can swap in any sort of wheels we'd like easily -- and we can add or remove "drop" as necessary.

The profile shown is 1010 -- 1" square.

We have a good history of building reliable drive trains that are also very light. We've been working lately on minimizing manufacturing time, so we're conceding some of the features that make things light in favor of those that make them quick to build.

Originally Posted by Andy Baker

You are right, as the t-slots do allow for the t-slot nuts to slip. However, another thing to do besides drilling a hole is to just add another t-slot nut to back up the initial nut. If there are 2 in a row, and both are tightened well (and checked routinely), then the slippage does not happen.

Andy

That'll be Fred's job. Fred is the advocate for 80/20 on our team and even then we use it sparingly. If it breaks, it's his fault.

[Andy L]

Our base was almost exactly like this last year and we had a few problems because the middle wheel was more dragging than helping

We removed it for Cal Games this year and it made a noticeable change when driving, but other changes we made to the robot made it hard to actually compare.

[s_forbes]

Great design, you could build that whole thing in a day! Well, except for the transmissions... I like how you completely eliminated the need for any tensioning device with the use of 80/20, very clever. The only "problem" I can see with it is the lack of any diagonal bracing, but I suspect the electronics board or the top half of the robot will account for that. I doubt that you'd let anything like that slip by.

[Rich Kressly]

Originally Posted by Cory

8020 itself is not actually particularly heavy. A very long time ago I did the math to see for myself and the 1010 series is almost exactly the same weight as 1x1x0.125" Al tube. The weight difference comes from all the connectors, t-nuts, and fasteners.

Yep, no doubt about that one. We spend a little extra to save some fastener weight by using drop ins and the hidden corner connectors, but overall we choose the convenience that 80/20 brings and deal with the "extra" weight.

[dtengineering]

I'm not entirely convinced that this is either stronger or lighter than basing a drivetrain on the KOP frame from IFI, but I do appreciate its simplicity.

Mind you, I'm not counting on having that in the kit this year, and have come to expect something innovative each year from the Xbots in the way of an off-season drive system prototype/model. I also base my KoP drivetrain comments on our experiences with it, and our team has in-house access to mills and a TIG welder that allows us to do a fair bit of "hot-rodding" to it.

I do like how this simplifies the chain/belt tensioning. I would suggest adding a second block, inboard of the two outboard axle mounts that has a bolt hole drilled and tapped parallel to the frame rail and is mounted to the frame rail in a similar way to the axle mounts. This way a bolt run through the tapped hole could be used to press on the axle mount and tension the chain very carefully, then the axle mounts could be tightened. Once the appropriate location for the second block was determined, then it could be welded in place, and the tensioning bolt could be secured with a lock nut. This way even if the axle mounts' bolts were to come a little bit loose the chain would not come loose.

See you in Portland and (yes!) Seattle!

Jason