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Drivetrain 2015

Attendance

Note Info

Students
Mentors
Date & Time
Location & Author
  • 1/27/2015

  • 3 hours

  • Shapland Shop

  • Mikhail S.

Guests

Jay


Notes

We need to get a willing group of newbies together to have them help drill out all the holes on the drivetrain once it arrives. 

In addition, we need to assemble a gearbox assembly team, mostly of newbies to the team, but also possibly of other more experienced members since these gearboxes are key to our robot and everyone should understand how they work.

Mikhail found that some parts that mount to the drivetrain hang over the lightning holes Lyle made, and this may or may not be of any significance.

Work Completed

For the first part of the meeting, Lyle and Jay worked to finish the engineering drawings and triple-check that all the files are correct so that we aren't screwed by the time we get the parts back from Wagner. They found a discrepancy in the files where the vertical mounts were misaligned with the holes in the drivetrain. They realized that this was because of incorrect constraints and improper hole placement on the top plate(the very top plate, not the drivetrain top plate). They proceeded to fix this hole placement, fixing the last known issue on our robot.

Mikhail finalized the BOM and had Lyle double check everything against his will. We ensured we were buying the right stuff since we already blew $200 on rivets we cant use beacuse they're steel and we dont have the strength to cut the mandrel. We noticed that while we were planning to buy 18 1/2" hex VersaHubs, we only bought 10 due to the wrong number being filled in the BOM (thanks Joaquin for asking for spares, allowing us to see we bought the wrong number). Since the Versahubs are out of stock until May, we found a 3rd party reseller that has them in stock for the same price as VexPro. We also decided to only get 17, leaving drivetrain one spare because we started taking money into account. After purchasing everything we should have about $500 left within our budget for two machined drivetrains, which means that we will be going over budget.  

Then a CAD guy showed up from Wagner (I don't know his name though) and spent a while with us explaining the mistakes we made this year.

First off, turns out we could have made the entire robot as a part and then converted it to a sheetmetal part.

Secondly, our entire issue with the holes not lining up turns out to be because Creo takes into account the loss of material due to the compressive force of a bend. It was recommended that instead of creating a flat part and then bending it, we should have instead used flanges. Flanges are an additive process instead of a modifying process, which allows us to directly define the size of the flange and then unbend to create an accurate flat part. In addition, flanges also make more sense for Creo, which would remove all the problems we had with bending rounded parts because Creo was thinking about how it would actually work out.

Lastly, we were informed that we should always send off our files with a couple main questions so that Wagner is able to help us resolve any issues we might have.

The CAD guy said that the easiest fix for our plate misalignment issue was to add the missing amount to the plate, but that due to our time constraint we can go through with our current plan of having smaller holes and drilling them all out. He noted that due to the thinness of the sheetmetal, it is possible to ruin it by drilling out the hole as the part gets thinner and thinner. He said that a possible fix for this is to support the inside of the hole with a block of wood that would limit the plates ability to bend out and rip.

Challenges

We are behind schedule in shipping out our parts because of the amount of issue we discovered in out parts.

The plates are still and will be misaligned due to the bend errors we made when making this drivetrain. 

We are running out of money fast. We currently have used $2960 out of $3500 on parts, $2050 of it on gearboxes, $460 on wheels, hubs, and Mini-CIMs, $260 on rivets, $80 on standoffs, $40 for bearings, $40 for screws and nuts, and $30 on grease and a grease gun. 

 

Work for Next Meeting

We need to convert all the engineering drawing constraints from fraction form to decimal form.

We need to send out the files to Wagner with some of our main issues and be ready to fix them if our files don't suit Kurt Wagner.

We still need to figure out a way to stop the tower from wobbling along the front-back axis. Since we have decided on having a square channel support for the top plate, we need to decide on the optimal placement of those bars and then add some crossbracing between the back 80/20 posts and the square channel. This should reduce a lot of the concerns with the stability of the tower as we move around the field. 

On Schedule?

We are behind schedule, but should ship out the robot very soon and start assembling gearboxes to be ready to quickly assemble the drivetrain and the robot. We are currently hoping to have the machined parts back to us by Friday the 30th, which the Wagner guy said is the equivalent of magic happening since even a 2 week turnaround is fast and rare. We reasoned that Wagner really really likes us and what we do.