pic: FRC488 - 80/20 Drive Train



Everyone else is doing it. We’re getting really lazy and have been moving toward drives that are fast to build and maintain. This will be a bit heavier than our drive from last season because of the 80/20 and larger diameter wheels, but should cut our 20 hour assembly time in half.

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.

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.

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. :stuck_out_tongue:

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.

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.

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

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.

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. :slight_smile:

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.

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. :slight_smile:

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.

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.

I almost slapped an “FRC100” tag on it… :smiley: But I’ll resist…

Kinda reminds me of some of our drive ideas.

Our team doesn’t actually ues 80/20 connectors, we use bolts with filled off heads, or toilet bolts. This spares us the aggravation of dealing with sliding, twisting, falling-out 80/20 biscuits.

That’s very clever.

But how will you reache the bolt if the axle is in it? And how will you tension your chains if the wheel isn’t in there? :confused:

We usually buy a kind of extrusion that 80/20 sells that already has the flat groove, and then we put the holes in it ourselves.

Instead of the pivot blocks, you might look at the 10 s 2497 parts. They may handle the shock loads better and the 2 " and 2 T nuts grip better. The raw stock can also be purchased if you want to cut your own. Watch the 8020 garage on e-bay. Any reason for the 1/2" shaft? For a dead axle a 3/8" grade 8 bolt is enough and lighter.

Team 980 has used the 1010 size 80/20 extrusion in our robot chassis for years now. Our six-wheel drive with Andy Mark SuperShifters goes together very quickly and getting proper tension on the chains is easy. We use simply-machined phenolic bar stock as pillow blocks for the axles with fastener through-holes spaced at 2". Instead of the more expensive drop-in T-nuts, we use economy triple T-nuts. We haven’t had problems with slippage of the fasteners, we put a bit of Lock-tite on the threads and torque them down.

I don’t see us changing this approach for sometime to come.

Oh yeah, you can save some $$ if you buy from 8020 Inc Garage Sale on E-bay.

M-
We use the t-slots until we have chain cut and drill through and bolt once everything is in a final position. The bearing blocks we have are slotted and allow for minor adjustments if necessary. Our t-slots always wound up sliding in the 80:20 and wound up being more maintenance that it was worth without bolting through. After 4 years of this, my advice would be to go ahead with the t-slots and if they never slip, great - but leave yourself space to drill and bolt through just in case. It’s a quick enough move with a hand drill and some 1/4-20 bolts.

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.