pic: 6WD Sheetmetal Chassis

[O'Sancheski]

loading photo ...

[IanW]

It looks really good.
I'd say the lightening pattern is rather conservative, so if you're pressed for weight, you could probably take some more out.
Looks like you might have more rivets than you really need on the gearboxes, but better to have too many than too few I suppose.
This may be something you intentionally didn't add, but you may want to consider a bellypan for reasons ranging from enhanced rigidity to convenient location for electronics.
My only other thought was that you might want to add more overlapping/connecting material at the corners. I have modeled a couple drivetrains like this, but have never built one of them, so I will defer to someone with more experience on this aspect.

[2185Bilal]

That desgin, but i think chaining only the lower 4 wheels so the bot can turn better

[O'Sancheski]

Originally Posted by IanW

It looks really good.
I'd say the lightening pattern is rather conservative, so if you're pressed for weight, you could probably take some more out.
Looks like you might have more rivets than you really need on the gearboxes, but better to have too many than too few I suppose.
This may be something you intentionally didn't add, but you may want to consider a bellypan for reasons ranging from enhanced rigidity to convenient location for electronics.
My only other thought was that you might want to add more overlapping/connecting material at the corners. I have modeled a couple drivetrains like this, but have never built one of them, so I will defer to someone with more experience on this aspect.

I am planning on adding cross supports over and under the gearboxes for added rigidity.

Originally Posted by 2185Bilal

That desgin, but i think chaining only the lower 4 wheels so the bot can turn better

Ummm. I'm not quite sure what you are saying here. I stated that I dropped the center wheel 1/8"

[BJC]

Tip: If you dropped the center wheel 1/8" you will have 1/4" of rock in your chassis because it will not sit as it does in your CAD. If this is the case and you actually want 1/8" of rock I suggest either raising an outer wheel 1/8" or dropping the center only 1/16"

Regards, Bryan

[apalrd]

A few questions:
-What size rivets are they, and at what spacing?
-Why the 0.090" 5052? We looked at 5052 this year, but decided to go with 0.063" 6061 (and later decided we should have gone with 0.050" 6061). A thinner material would be lighter, and 6061 0.063" is strong enough for a FIRST robot with bumpers.
-Any details on the shifter, specifically the ratio and shaft design?

And finally, any plan to remove the transmission in vehicle if you ever have to? It looks like it would be very, very difficult to work on anything inside the transmissions as it is now. Even though it would possibly weigh slightly more, you could pocket out the space of the transmission side plate that is integrated into the frame, and put another plate over it. The transmission would then be a single assembly bolted into a hole on the frame.

[Ekcrbe]

Originally Posted by apalrd

And finally, any plan to remove the transmission in vehicle if you ever have to? It looks like it would be very, very difficult to work on anything inside the transmissions as it is now. Even though it would possibly weigh slightly more, you could pocket out the space of the transmission side plate that is integrated into the frame, and put another plate over it. The transmission would then be a single assembly bolted into a hole on the frame.

Seconded. We had a sticking transmission at Worlds, so we took the whole thing out and put in our spare in a few minutes. Definitely an important consideration.

[O'Sancheski]

Answers are in bold.

A few questions:
-What size rivets are they, and at what spacing?
3/16" at 1/2" spacing
-Why the 0.090" 5052? We looked at 5052 this year, but decided to go with 0.063" 6061 (and later decided we should have gone with 0.050" 6061). A thinner material would be lighter, and 6061 0.063" is strong enough for a FIRST robot with bumpers.
I decided on .09" 5052 because that's what I've seen many teams use and since it was my first sheetmetal chassis I thought that would be a good starting point.
-Any details on the shifter, specifically the ratio and shaft design?
The shaft is made custom on a lathe/mill. I will try to upload a pic of the actual shaft but it is not letting me put an attachment in this post.
And finally, any plan to remove the transmission in vehicle if you ever have to? It looks like it would be very, very difficult to work on anything inside the transmissions as it is now. Even though it would possibly weigh slightly more, you could pocket out the space of the transmission side plate that is integrated into the frame, and put another plate over it. The transmission would then be a single assembly bolted into a hole on the frame.
I am going to pocket out the flanges above the transmissions. I am also probably going to remove the rivets attaching the transmission to the chassis and replace them with bolts for easier removal.

[akoscielski3]

Over All GREAT Looking Chassis!
But I still have things that I would recommend you change to improve it

- I would change your lightening holes to Triangles rather than circles. It will help you lose more weight and can be stronger.
- I love the way you have the supports on the transmissions. But it will still torque your side plates. You will want to put some sort of cross braces of some sort. It could be just bottom braces though, just to pull in the bottom of the transmissions. TRUST ME! They will torque and your chassis WILL be warped. But Then again Bottom and Top braces will be better.
- Good job with the extended Top flanges. It will help keep your side plates in line properly.
- If I am looking at this correctly. Why are your axles live with that type of Chaining? you only need Live axles if they are passing threw plates (the wheel is on one side of the plate, and the sprocket is on the other). You will save weight if you change to Dead Axles. The only one that must be live is the middle wheel because it is direct driven.

Great job for your First Sheet-metal Chassis!

[O'Sancheski]

Originally Posted by akoscielski3

- If I am looking at this correctly. Why are your axles live with that type of Chaining? you only need Live axles if they are passing threw plates (the wheel is on one side of the plate, and the sprocket is on the other). You will save weight if you change to Dead Axles. The only one that must be live is the middle wheel because it is direct driven.

The only live axles are the center shafts which are direct driven off the transmission. The outer 4 wheels are dead axles with a 22T #35 chain sprocket.

[akoscielski3]

Originally Posted by O'Sancheski

The only live axles are the center shafts which are direct driven off the transmission. The outer 4 wheels are dead axles with a 22T #35 chain sprocket.

Okay I am looking at it wrong then. What are the circle on the outside wheels, that to me look like bearings?

[O'Sancheski]

Originally Posted by akoscielski3

Okay I am looking at it wrong then. What are the circle on the outside wheels, that to me look like bearings?

They are bearings inside a bearing block for support.

[akoscielski3]

Originally Posted by O'Sancheski

They are bearings inside a bearing block for support.

yea I would lose them. All you need for a Dead Axle is a threaded rod with two bolts to hold it in place. 1/4-20 bolts will work fine. That is what we use, and dont have a problem with them

Heres and example of what I have designed. As you can see you don't need bearings for those wheels

[Jeff Waegelin]

Originally Posted by apalrd

And finally, any plan to remove the transmission in vehicle if you ever have to? It looks like it would be very, very difficult to work on anything inside the transmissions as it is now. Even though it would possibly weigh slightly more, you could pocket out the space of the transmission side plate that is integrated into the frame, and put another plate over it. The transmission would then be a single assembly bolted into a hole on the frame.

This. I went back and forth over integrating the gearboxes in Scorpion this year, and eventually decided to make the gearbox have two independent plates, and a big pocket in the frame, like mentioned above. It was invaluable when we had to service one of the gearboxes at the Dallas regional. Because we built the gearboxes independently, we could bring a whole spare gearbox, and when a screw sheared on the dog shifter, we just pulled the broken one out and swapped in the spare. A 10 minute fix instead of possibly 30 minutes or more. And even if we hadn't had a spare, it's still much easier to work on a gearbox that's on a table than one buried inside a robot.

So, while integration looks nice and is a little lighter... design for maintenance is important! A little thought ahead of time can save valuable time in the heat of competition.

[Andrew Schreiber]

Where do the encoders go? Here is where keeping a live axle wheel might be useful as it would be a simple way to toss an encoder onto a shaft. Other options (if you wanted to go dead axle) would be to use follower wheels, I believe 148 has a great picture of one from 2009 on CDM here.