Difference between revisions of "Talk:DEWBOT VI PARC XIII"

Revision as of 11:45, 12 May 2010

Repairs & Modifications Following PARC XIII

10-May-2010

The Pivots received a thorough overhaul last night and should be good for Monty Madness this Saturday. We replaced a blown bearing (a spacer had been mis-installed), realigned Transfer Axles and Wheels and tightened all set screws on the Transfer Axles (replacing a couple set screws which went missing). Out of the two swapped-out Pivots, we assembled one working spare Pivot in good condition and ready for use.

The left side Ball Dam Gussett was badly bent in at the bottom. This would have required a considerable impact. Our PARC Pivot failure was on Pivot #3, also in the front left corner, so one hypothesis for the failure is a greater than normal impact to this corner of the robot during PARC Q1. A second hypothesis is that the Pivot which failed was the one with the loosest fit between the Pivot Tube and Pivot Plate (this loose fit was noted during assembly). The bent Ball Dam Gussett was straightened.

A weld inspection revealed no new broken welds. The known broken weld was not repaired.

The 1" Angle frame top elements are all noticeably bent inwards due to competition impacts. Square tubes would have been a better choice (angles were used for weight & Center-of-Mass management).

Latch wire ties were gone. Replaced.

Agreed on IR sensor (2Y0A21 F) mounting position (for sensing that the ball is in kicking position). We'll mount this on Wednesday.

Added side-ramps onto the goal ramp to better match the field geometry (and reduce wear and tear on the robot drive-train).

On Wednesday, we will mount the IR sensor and wire the Accelerometer.

Time permitting, we'll switch more wheel tread mounts over to the Deaver system.

Gary Deaver adds:

After inspecting the robot Monday night, it is apparent that PARC was a bash fest for us. The pivot top plate tube joint has been a design concern from the beginning. The Pivot tube- top plate joints have held up until last weekend. The joint is loose in only 1 direction. This indicates that the wheel suffered a intense impact. The only way I can see this type off force would be to hit the ramp at just the right angle. This is a driver issue. The drivers need to be careful around the humps and take care with the approach angle. The joint failure is consistent with the simulation that was run in January. The other failure mode was stress cracking at the inner web of the top plate. I have not noticed any fatigue in the top plates. This failure is related to the hardness of the AL. We could go to a 7000 series AL and almost double the hardness of the plates. The problem with this is cost and machinability. I'm satisfied with the current material. Also the box construction of the lower pivot has proven to be more than strong enough. I have seen many other teams with the skinny side plates fail. Ours is robust. Considering the total hours of drive time and the aggressive play I think the pivots have held up well. On a flat field we're good. Any raised field pieces will always be a concern. The window motors are not the proper motor for the job but, it's what we have. The top 1/8" AL angle frame is bent. 8020 quick frame tubing would be a good option. It's 1/6 wall and has a flange for recess mounting the poly covers. 104 built the whole robot frame quick frame and it was durable. Also 1" box pultrusions can be a good choice were impact and durability are a factor. Our pre kick off frame plan had many advantages. Leave it to the GDC to destroy the best laid plans. Last weekend mat have been physical but, next weekend could prove to be the hardest test yet. Some real good teams. As far as the wheel cover attachment, drive and auto take precedent now. Is there time?

11-May-2010

Received the 4-wire Accelerometer Cable from Scott Featherman.