pic: FRC488 - Fall Project, Rev. A

[AdamHeard]

Originally Posted by EricH

Not really. You need something there, unless you like frames being non-rectangular parallelograms or other interesting shapes. We're talking 0.090 sheet metal here, with a weight reduction pattern--can't get much thinner and lighter than that without needing some extra support. If that bellypan is more than 2 lb, I'd be shocked; I wouldn't be surprised if it was closer to 1 lb or under. Removing more weight won't exactly help in this situation.

You would have to remove 80% of the material in a 1/16" pan that is 28x28 to get it under a lb.

[JamesCH95]

Have you tested or analyzed that cantilevered gear design? Even small deflections could result in poor performance and/or damaged/destroyed gears.

[Madison]

Originally Posted by roystur44

The battery box can also hold the breaker and provide a base for easy access to the breaker. It can also hold a data access port for connection to the router. How many times have you seen teams struggled to gain access to the router data ports? Maybe even hold the sidecar for easy access.

I like the idea of adding a fixed data port somewhere along the outer frame. I think it'd get me a lot of brownie points with the electrical and programming teams.

Don't forget the mounting holes for the manipulator and the bumpers brackets.

Bumpers have been a weak point for us for the last two seasons, so I'm going to give them some real thought this time around. I haven't gotten to them yet, though.

Bring the gear closer to the transmission bearing keeping the distance to a minimum.

I'm looking at ways of managing this. Currently, the transmission is offset from the clamshell by 3/8" to allow access to the wheel mounting hardware on the inside face. I'm considering using captive nuts here instead (to accept the bolt inside the wheel axle spacer) and moving the transmission flush with the inside face. That'd put the gear 3/8" closer to the bearing.

Whats the drop on the wheels? Driving more than six wheels means you get a lot of wheel scrub. The outer wheels will scrub down to nothing if there is a lot of turning and the drop is minimal.

The outer two wheels on each side are 1/8" higher than the inner three.

Originally Posted by OWilliamson

I'm not sure if you had considered this, but cutting out part of the bellypan where the gearboxes will be above can make maintenance a lot easier. We didn't do that this year and it was a nightmare trying to repair our gearbox before eliminations.

As it stands now, the gearboxes are removed by lifting them upward. Since they're sealed, I'm not sure how having access to the bottom will be helpful.

Originally Posted by DampRobot

I have to say, this is a really beautiful design. It looks just like 971, but with gears instead of belts. I'm a huge fan.

Just a few questions, perhaps they've been addressed elsewhere. Any reason you've chose 10 wheels? I don't see any advantage for 10 over 6, and having more wheels carries cost and weight (not to mention potential turning) disadvantages. Also, I'd assume these parts are being laser cut? Waterjetting or turret punching those parts would take a lot of sponsor time.

Originally Posted by Billfred

If you're still going to power the corner wheels, a gear has to occupy that space anyway to act as an idler. Why not run 10 at that point?

Billfred's got it right. I could've designed this for 6 or 8WD as well and included more idler gears. Maybe in competition, that'd be a bit more likely, but for a fun project, why not go with 10WD?

And yes, the parts are being laser cut.

Originally Posted by EricH

If that bellypan is more than 2 lb, I'd be shocked; I wouldn't be surprised if it was closer to 1 lb or under. Removing more weight won't exactly help in this situation.

The middle chassis piece is 4.84 lbs and is made from .090" sheet. It's not just a belly pan; it integrates the front and rear cross rails.

Originally Posted by JamesCH95

Have you tested or analyzed that cantilevered gear design? Even small deflections could result in poor performance and/or damaged/destroyed gears.

We ran a similar arrangement in 2013 and it was the only thing that didn't fall apart after the frame got all wonky. I'm sure, by the end, it wasn't as efficient as it should've been, but it was working. I'm working on some alternatives, though, to see if we can't make it better.

[Andrew Schreiber]

Originally Posted by Madison

I like the idea of adding a fixed data port somewhere along the outer frame. I think it'd get me a lot of brownie points with the electrical and programming teams.
...
As it stands now, the gearboxes are removed by lifting them upward. Since they're sealed, I'm not sure how having access to the bottom will be helpful.

Yes, that would get you brownie points.

...

Perhaps consider removing from the bottom since there isn't anything that can go below the chassis yet you will (likely) have a superstructure and removing the transmissions through that tends to get hairy.

[Aren Siekmeier]

Originally Posted by Andrew Schreiber

Perhaps consider removing from the bottom since there isn't anything that can go below the chassis yet you will (likely) have a superstructure and removing the transmissions through that tends to get hairy.

It looks like the corner joints in this case wouldn't make this very easy, but you could also consider using a few bolts to attach each side rail assembly to the central frame, so that you can remove an entire drive side, without needing clearance out the top or bottom, by just removing those few bolts. Maneuvering the gearbox with its output shaft out the guts either upwards or downwards can be difficult, so it can be easier to leave everything intact until you have it in open air to work on.

Edit: I just noticed with the belly pan coming under this time around, this would be even less feasible But maybe if the side rail stands alone as its own rigid box...

[Nuttyman54]

Originally Posted by Madison

Bumpers have been a weak point for us for the last two seasons, so I'm going to give them some real thought this time around. I haven't gotten to them yet, though.

Since your frame style is already very similar to 971's, you might want to take a look at how they do the bumper mounts too. A sheet metal frame fits against the bumper backing with draw latches. The matching latch hook is riveted to the robot base. It's a pretty secure fit, and they're fairly easy to remove (just watch the clearances around the superstructure). We've done the bumpers as one piece like this for the past few seasons, but you could do them as halves, also. I'm not sure it would work well if you wanted each side to have its own bumper.

Originally Posted by Andrew Schreiber

Perhaps consider removing from the bottom since there isn't anything that can go below the chassis yet you will (likely) have a superstructure and removing the transmissions through that tends to get hairy.

Considering that it's a sealed, COTS transmission, I'm not sure how likely it is that you'll actually need to remove the transmission for repair, so unless it's easy to make it removable through the bottom and has no adverse effects on the overall strength/rigidity/manufacturability of the chassis, it might not be worth worrying about it, as long as there is a way to get them out. Since the transmission output is cantilevered over the top of the chassis rail, it has to rotate some to take it through the bottom without bringing it in towards the centerline.

[James Kuszmaul]

Originally Posted by Nuttyman54

Since your frame style is already very similar to 971's, you might want to take a look at how they do the bumper mounts too. A sheet metal frame fits against the bumper backing with draw latches. The matching latch hook is riveted to the robot base. It's a pretty secure fit, and they're fairly easy to remove (just watch the clearances around the superstructure). We've done the bumpers as one piece like this for the past few seasons, but you could do them as halves, also. I'm not sure it would work well if you wanted each side to have its own bumper.

One thing to watch out for with these is that, the first time we did this, we made our hooks too weak, such that they gradually got bent up over time by the force from the draw latches and the draw latches stopped latching.

[Billfred]

Originally Posted by Madison

Bumpers have been a weak point for us for the last two seasons, so I'm going to give them some real thought this time around. I haven't gotten to them yet, though.

If you have to punt on bumper mounting, 2809's reversible bumpers are a proven favorite among teams I've been on before. Even if your mounting inhales audibly, your teammates won't hate you too much if they only have to take them off once at inspection.

[BBray_T1296]

Question: are the front and rear most wheels raised any? If not, you will either have trouble turning, or very quickly ruin those 4 wheels

[Madison]

Originally Posted by BBray_T1296

Question: are the front and rear most wheels raised any? If not, you will either have trouble turning, or very quickly ruin those 4 wheels

The outermost wheels are raised by 1/8". This has a pretty short wheelbase and will have no trouble turning.

Even if all of the wheels were at the same level, the wheelbase remains very short. It's about 22".