pic: Simple, Yet Effective Chassis

[Alex Cormier]

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[thefro526]

I like it. It looks very simple and very solid and like you've left more than enough space open to mount a manipulator or what ever is going on it. I have two questions though, what's the approximate outside dimensions, and what's the offset of the center wheel if at all?

I ask that because from the render makes the base look pretty square and if it is I was wondering if you even need to offset the center wheel because in my experimentation I've found that the shorter your wheel base is the less of an offset you need.

[dbell]

How do the six cross-members mount to the side plates?
Is the green plate on the bottom for electronics?
Did you lower the center wheel? If so, by how much?

[Alex Cormier]

The dimensions are 27.75" x 37.75". The middle wheels are lowered by 1/8". Those big black 'end caps' attach the side plates to the front rails and back rails. The mini support braces inside attach to the 1x1's and attach to the side plates too. I did not include all the 1/2" rod supports due to i did this on my laptop and inventor freaks out as is. I also left out the idlers. There is a lexan sheeting to add the electronics and transmissions and what else you want on there.

My next design will include a transmission within the side plates. I am trying to make these designs not fabulous looking, but able to be made by any team with out much resources.

This type of design has been proven since 2005. The axle system was something I picked up from 1930. It is very unique and a great idea. The axle has a hole for a pin to go through, so in the need of repair all you need to do is pull the pin and the axle will come out with ease. The wheels will be driven from sprockets attached to the wheels.

Any other questions?

[JesseK]

Historically, have there ever been any problems with the inside 1/4" side rails flexing where they're not supported? Under normal operating conditions I'm sure it's minimal to non-existent, but what about the shock of an impact?

This looks like the perfect setup for the Stackerbox mecanum setup I've been toying with, but I do have reservations.

[Alex Cormier]

Originally Posted by JesseK

Historically, have there ever been any problems with the inside 1/4" side rails flexing where they're not supported? Under normal operating conditions I'm sure it's minimal to non-existent, but what about the shock of an impact?

This looks like the perfect setup for the Stackerbox mecanum setup I've been toying with, but I do have reservations.

There are more little 1/2" rod supports spread out that I did not include. I am running inventor on my laptop, it's not the best, so I leave out the little things. There were no issues that I knew of from that.

[MrForbes]

Looks like a good basic design. I'd suggest that teams thinking of making it, use an outside dimension of 26" x 36" because we all know how much robots grow as you add stuff....

[AdamHeard]

Originally Posted by Alex Cormier

There are more little 1/2" rod supports spread out that I did not include. I am running inventor on my laptop, it's not the best, so I leave out the little things. There were no issues that I knew of from that.

Can you explain the rod supports and where they would go?

[Alex Cormier]

Originally Posted by AdamHeard

Can you explain the rod supports and where they would go?

They would go in between the side plates. for further support. If you have a chance take a look at the 03, 05-08 chassis from 1126.

[Jim E]

You mentioned lexan for the electronics, I prefer 1/4"oak plywood. It weighs less and is more resistant to flexing.

[Ian Curtis]

Originally Posted by Jim E

You mentioned lexan for the electronics, I prefer 1/4"oak plywood. It weighs less and is more resistant to flexing.

How much does it weigh? This year we tried to find a lighter plastic solution than our usual 1/8" lexan with holes cut through under the components and couldn't find one. Have you ever tried using a thinner board?

What are you trying to avoid with a stiffer material? We usually mount ours along the rails with it just resting on the frame cross braces and have never had any issue. One year we even mounted it vertically, and had no flexing problem.

[DGrohnke1023]

For our electronics the past 2 years we have used 1/4" corrugated plastic. I believe it weighs around .25 lbs/ft. The stuff is amazing, you can run wires through it, we even used it for our ramps in 07. I think it also costs less than Lexan as well. I highly recommend the material.

[JesseK]

We usually

Keep in mind that next year's electronics may almost weigh the same, but the weight distributions will be more concentrated due to a more compact design. What we "usually" do for mounting these systems will have to at least be reconsidered next year.

As for the above oak/lexan debate, here's some data. The other mentors and I have always asked ourselves what the real benefit of lexan over other materials was, so I just did some research.

According to matweb a typical lexan sheet has a density of ~0.041 lb/in^3 whereas most solid oak hardwoods have a density of ~0.021 lb/in^3. The flex testing of lexan was done with 1/4" sheets and yielded ~65% flex resistance over with-the-grain testing of oak, yet for almost twice the weight of oak. Hence, for the application of mounting electronics I think it's safe to say that typical 1/8" thick lexan and typical 1/4" thick oak are about equal when considering "will it work".

[Peter Matteson]

Originally Posted by JesseK

Historically, have there ever been any problems with the inside 1/4" side rails flexing where they're not supported? Under normal operating conditions I'm sure it's minimal to non-existent, but what about the shock of an impact?

That can easily be fixed with COTS spacers from McMaster tha can be added after the fact. Also the addition of bumpers reduces the required thickness of that out materiaal if you plan ahead.

Looks like a good first pass. The next step is to figure out the details which is the cross bace mounting and reinforcement. The devil is in those details and balancing ease of assembly/disassembly with robustness/rigidity.