14-05-2012 20:40

IanW

Re: pic: 6WD Sheetmetal Chassis

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.

14-05-2012 20:43

2185Bilal

Re: pic: 6WD Sheetmetal Chassis

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

14-05-2012 20:46

O'Sancheski

Re: pic: 6WD Sheetmetal Chassis

Quote:

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.

Quote:

Originally Posted by 2185Bilal That desgin, but i think chaining only the lower 4 wheels so the bot can turn better

14-05-2012 20:59

BJC

Re: pic: 6WD Sheetmetal Chassis

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

14-05-2012 21:03

apalrd

Re: pic: 6WD Sheetmetal Chassis

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.

14-05-2012 21:16

Ekcrbe

Re: pic: 6WD Sheetmetal Chassis

Quote:

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.

14-05-2012 21:23

O'Sancheski

Re: pic: 6WD Sheetmetal Chassis

Answers are in bold.

14-05-2012 21:37

akoscielski3

Re: pic: 6WD Sheetmetal Chassis

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!

14-05-2012 21:52

2185Bilal

Re: pic: 6WD Sheetmetal Chassis

Quote:

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

14-05-2012 21:56

smistthegreat

Re: pic: 6WD Sheetmetal Chassis

Quote:

Originally Posted by 2185Bilal ohh im sorry, i was saying that i really like the design but i would only chain four wheels, and in the front put like omni-wheels so the turn ability is increased. Like the way the u have it now, it will turn but not as fast as it could

14-05-2012 21:58

Gregor

Re: pic: 6WD Sheetmetal Chassis

Quote:

Originally Posted by smistthegreat As has already been stated, the center wheels are dropped to ensure smooth turning. Generally, to improve turning performance, you can either drop the center wheels or add omnis at one or both ends. Doing both is not necessary.

14-05-2012 22:02

MichaelBick

Re: pic: 6WD Sheetmetal Chassis

Quote:

Originally Posted by 2185Bilal ohh im sorry, i was saying that i really like the design but i would only chain four wheels, and in the front put like omni-wheels so the turn ability is increased. Like the way the u have it now, it will turn but not as fast as it could

14-05-2012 22:24

O'Sancheski

Re: pic: 6WD Sheetmetal Chassis

Quote:

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.

14-05-2012 22:26

akoscielski3

Re: pic: 6WD Sheetmetal Chassis

Quote:

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.

14-05-2012 22:34

O'Sancheski

Re: pic: 6WD Sheetmetal Chassis

Quote:

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?

14-05-2012 22:42

akoscielski3

Re: pic: 6WD Sheetmetal Chassis

Quote:

Originally Posted by O'Sancheski They are bearings inside a bearing block for support.

14-05-2012 23:08

JVN

Re: pic: 6WD Sheetmetal Chassis

Looking very good, especially if this is your first!
(Love the general configuration -- very 'wrangler. )

A few comments:
1. Is there any reason the front/back wheels need to be live axle? You're not tensioning them. My suggestion is to make them dead-axles, and make them structural. I love something called a "tube axle" here -- 1/2" OD, 1/4" ID tube, with a 1/4-20" bolt running through it. It'll stiffen things right up around the wheels (where it really matters!).

2. I don't like using sheet-metal as standoffs for gearbox plates. I recommend you use standoffs there, though other (equally as experienced) mentors would disagree with me, and have, loudly. YMMV.

3. You've got loooooots of rivets in places where it doesn't matter. That vertical row of rivets in the front bumper? Yeah... you need less than half of that. Hit the top and bottom hole, then space a few out in between. Then again, it doesn't matter -- rivets are almost "free."

4. Your lightening pattern can be a LOT more aggressive if you want. Even if you decide to stick with rounds, you can add additional smaller holes around your big holes. Remember the bumpers will add a lot of strength if done correctly.

5. Since you've adopted a "no belly pan" design -- make sure whatever upper structure you add provides torsional rigidity (helps prevent cross-corner flex). You can test this by holding three corners down, and lifting the fourth.

If you have the opportunity, build it, test it, and tweak it.
This is a low risk design which you should feel comfortable going into a season "cold" with, but another revision of lessons learned is worth its weight in gold.

Kudos again for a great first design!

-John

PS - Just noticed you're Potsdam bound -- enjoy Clarkson!

14-05-2012 23:12

tim-tim

Re: pic: 6WD Sheetmetal Chassis

He is ALIVE!!!!

Quote:

Originally Posted by JVN Looking very good, especially if this is your first! (Love the general configuration -- very 'wrangler. ) A few comments: 1. Is there any reason the front/back wheels need to be live axle? You're not tensioning them. My suggestion is to make them dead-axles, and make them structural. I love something called a "tube axle" here -- 1/2" OD, 1/4" ID tube, with a 1/4-20" bolt running through it. It'll stiffen things right up around the wheels (where it really matters!). 2. I don't like using sheet-metal as standoffs for gearbox plates. I recommend you use standoffs there, though other (equally as experienced) mentors would disagree with me, and have, loudly. YMMV. 3. You've got loooooots of rivets in places where it doesn't matter. That vertical row of rivets in the front bumper? Yeah... you need less than half of that. Hit the top and bottom hole, then space a few out in between. Then again, it doesn't matter -- rivets are almost "free." 4. Your lightening pattern can be a LOT more aggressive if you want. Even if you decide to stick with rounds, you can add additional smaller holes around your big holes. Remember the bumpers will add a lot of strength if done correctly. 5. Since you've adopted a "no belly pan" design -- make sure whatever upper structure you add provides torsional rigidity (helps prevent cross-corner flex). You can test this by holding three corners down, and lifting the fourth. If you have the opportunity, build it, test it, and tweak it. This is a low risk design which you should feel comfortable going into a season "cold" with, but another revision of lessons learned is worth its weight in gold. Kudos again for a great first design! -John

15-05-2012 14:45

Jeff Waegelin

Re: pic: 6WD Sheetmetal Chassis

Quote:

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.

15-05-2012 14:55

Andrew Schreiber

Re: pic: 6WD Sheetmetal Chassis

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.

15-05-2012 15:28

Brandon Holley

Re: pic: 6WD Sheetmetal Chassis

Quote:

Originally Posted by apalrd A few questions: -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.

15-05-2012 15:31

Jeff Waegelin

Re: pic: 6WD Sheetmetal Chassis

Quote:

Originally Posted by Brandon Holley Sorry I'm a bit late to the party on this, but one huge advantage to 5052 Al over 6061 Al is formability. 5052 is much more conducive to sheet forming than 6061 is (bending, rolling, etc). It is also easier to weld if you plan on implementing welds in your design. I'd stick with 5052 for a sheet metal design like this, but thats just me. I'm sure 6061 can be made to work as well. -Brando

15-05-2012 19:42

apalrd

Re: pic: 6WD Sheetmetal Chassis

For gearboxes, we actually used AM shifters with a final drive chain to a live axle. The gearboxes used 0.090" aluminum plates, and there were four slots in the frame where the gearboxes would bolt, and we could slide the entire gearbox up/down up to 3/4" or so to tension the final drive chain. The encoder was integrated into the AM shifter output. We really liked this design, and would do something similar again. The ability to change the final drive ratio was very nice, we changed it three times during the season.


On sheet metal alloy, we've had no trouble bending 6061 0.050" and 0.063" in our shop on a manual finger brake, but 5052 is easier to bend, especially thicker sheets. Using 6061 allows us to use thinner sheets.

15-05-2012 20:54

BrendanB

Re: pic: 6WD Sheetmetal Chassis

Quote:

Originally Posted by apalrd For gearboxes, we actually used AM shifters with a final drive chain to a live axle. The gearboxes used 0.090" aluminum plates, and there were four slots in the frame where the gearboxes would bolt, and we could slide the entire gearbox up/down up to 3/4" or so to tension the final drive chain. The encoder was integrated into the AM shifter output. We really liked this design, and would do something similar again. The ability to change the final drive ratio was very nice, we changed it three times during the season. On sheet metal alloy, we've had no trouble bending 6061 0.050" and 0.063" in our shop on a manual finger brake, but 5052 is easier to bend, especially thicker sheets. Using 6061 allows us to use thinner sheets.

15-05-2012 22:20

apalrd

Re: pic: 6WD Sheetmetal Chassis

I don't have any pictures of the gearboxes. I'll see if I can take some soon.

16-05-2012 15:59

apalrd

Re: pic: 6WD Sheetmetal Chassis

I took some pictures. Here are two.



The case bolts go all the way through both gearbox plates, the spacers, and the frame. There is a nut on the outer gearbox plate, then some washers, the frame panel, more washers and another nut. The frame panels have slots to move the gearbox up/down to adjust the chain tension of the final drive chain. The final drive ratio is 12:22, the final drive sprocket is an AM 22T with AM 500 hex hub. The CAD model will be released in the next week or so.