pic: Prototype Drivetrain
 

Re: pic: Prototype Drivetrain
 

It looks like you only have 2 CIMS powering your drivetrain. Did you do this to save weight, or do you have another purpose for them? I'm of the belief that there are enough motors available in the KOP that 4 CIMs (or at least a CIM and a FP) should be used on any drive train (with 2K9 being an anomaly).

Re: pic: Prototype Drivetrain
 

Replace all the 1/16th wall aluminum with 0.035" wall 4130 steel square tubing. You'll improve chassis strength, stiffness, maintain the same weight, and your welder will have an easier time.

With a steel frame you could also use weld-in nuts which could save you weight and make it easier to wrench on the robot :cool:

Re: pic: Prototype Drivetrain
 

Are you using Riv-nuts to hold on the axle pillow blocks?

Re: pic: Prototype Drivetrain
 

Instead of using washers to lower your middle wheels, try drilling the holes in all 16 pillow blocks off center by 1/16", and flip the middle ones over so the axel ends up being 1/8" lower than the outside axels. Adding washers isn't as clean/sturdy.

Also, to lower your CG (which is ALWAYS important), you might want to mount the pillow blocks on the top side of your lower frame members, that way the whole frame is lowered a total of 2 inches. And try mounting your electronics (Battery/CRio/etc) on the lower frame level, not the upper one. This will lower your CG and give the manipulator teams more area to work with. Win Win. :D

Re: pic: Prototype Drivetrain
 

Instead of welding the pieces together, I would recommend using these Brunner Connectors. We've been using these for quite a while. Just make some 1/8" thickness aluminum gussets and some self-tapers in order to secure the pieces together.

Re: pic: Prototype Drivetrain
 

Self tapping screws?

Re: pic: Prototype Drivetrain
 

Just how would this maintain the weight? 4130 Steel is about 2.83 times as dense as 6000 series aluminum. You're not even halving the wall thickness in your recommendation. This change would add a significant amount of weight. I would not recommend it.

Re: pic: Prototype Drivetrain
 

I'm sorry, I should have been more explicit, my brain is not 100% in this caffeine-free day :(

3/4"x0.35" square 4130 steel tubing would roughly maintain the weight of a 1"x0.065" aluminum square tube. The benefit is that 4130 steel still has a YS of around 70-80KSI when welded, whereas welded 6061 aluminum will be total garbage, around 8-10KSI. With further optimization a far more efficient chassis is possible if you use welded 4130 vs welded 6061 because the yield-strength:density ratio is roughly five times higher with welded 4130 compared to welded 6061.

Re: pic: Prototype Drivetrain
 

Excellent suggestion. Simple and if a jig is used, very repeatable.


From my many years in the Medical Imaging field performing maintenance on very heavy mobile systems, I have to disagree here, to a point.

With the pillow blocks on the bottom of the main rails, the axles put the pillow blocks and their mounting hardware in compression. The weight of the robot is transfered to the wheels without being suspended by mounting bolts.
Now, if the pillow blocks were moved to the top of the rails, then the mounting hardware would carry the load to the wheels, thus creating an additional point of failure, unless designed properly, which would add weight.

Now to take this a step further, why use pillow blocks at all?
The OP said these were dead axles. If that is the case, then just mount them directly through the frame. Granted, you will not lower the CG quite as far, but I believe, based on the picture and description, it would be more than sufficient.

Re: pic: Prototype Drivetrain
 

Along the same lines, we've used 80/20 quickframe which is nearly identical to the Brunner stuff but the pricing is lower. We normally rivet 1/16" lexan to tie the frame together. We've had good luck with this method the last couple years.

Re: pic: Prototype Drivetrain
 

I'm not sure if I just missed, but what's the total weight?

Have you considered using sheet metal/lexan for your outermost part?

What about tensioners for your chain/belt?

Re: pic: Prototype Drivetrain
 

My team uses only two CIMs on our drive train in general so that we free up the rest to use on manipulators. depending on what we plan to do with the robot I may or may not add the additional CIMs.
.
The reason I used the materials I did is because my team has a very, very, very low off season budget and all the materials are scrap from this year's robot.
In terms of welding we have a sponsor who will weld our aluminum for us and they really do not have a problem welding it.

We are using 1/4-20 bolts and nylock nuts. I just didn't drill the holes because Inventor crashed.

I would not have thought of drilling holes off center. In general we have used washers and other spacers because we really don't have access to precision machine tools due to the fact we build out of one of the team members garages.
The battery, compressor, and speed controllers are all below the top of the frame, I put the CRIO on top for easier access. There will be a cover over it. I left the front Area pretty open and thought that that was enough space for the manipulators.

I have never had an aluminum weld break on me. We also use a professional welder on our frame.

How strong are the brunner connectors and 80/20 quickframe system. How much do they cost?

I appreciate the suggestions greatly and will try to implement them where possible.

Re: pic: Prototype Drivetrain
 

I did not notice this post while I writing my response.

What is shown wieghs about 48 lbs.
What do you mean by using sheet metal and lexan for the outermost part.
I wanted to put tensioners in but my 5 year old DELL laptop could barely run inventor long enough to make this render.
I would like suggestions on how to implement tensioners though.

Re: pic: Prototype Drivetrain
 

What gear ratio are you running in the Toughbox, and what's your chain reduction?