Power Wheels Racer Part 12: Updates and fixes

Part 12:

After the old brake handle broke off and the weld attaching the steering column came undone, we had to makes some updates to the car. First we decided to design and print a new brake handle. The two main properties we wanted the new one to have was an ergonomic grip and durability. The grip has four slots to fit the drivers fingers for a comfortable grip. To achieve the durability desired the grip was printed out of ABS instead of PLA and was given a 50% infill on the print. Once I put the handle I pulled back on it as hard as I possibly could and it didn't budge. I was even able to lift the front of the car off the ground by pulling back on the handle. Here is a couple images of the handle on the hydraulic break.
                            
However as I designed it the first time the handle did have a couple of flaws. The front end needed to be have a chamfer to clear the hydraulic break when it was resting. Also a small slot needed to be cut out of the inside also. The spacer that goes on the inside of the handle also needed to be shaved down a bit because I forgot to add tolerances to the width of it. I was able to do these with a dremel and angle grinder but since have went back and edited the solidworks file so that the next print will have all the features.

                           

The other thing that is different about this handle is the method in which it fastens to the break. I used 1/4 - 20 low profile screws and heat inserted nuts. The heat inserted nuts can be found on Mcmaster Carr and are inserted into pre-made holes by using a soldering iron. the plastic melts and hardens around the insert so it will stay in place. This is really nice for 3D printed parts because the nut is permanently fixed inside the part. The soldering iron wasn't quite long enough to insert the first heat insert through the hole and I melted a little bit of plastic around the outside. Next time I will have to use a longer skinnier iron. The inserts are pictured below.

                                       
Another change that was made was the throttle set up. Instead of twisting your hand around the handle now the throttle is activated by the driver's thumb. This allows the driver steer a little more comfortably while engaging the throttle. Bryan is also going to use two more 90 degree PVC joints and another shaft to make the steering wheel a rectangle rather than a U shape soon.

In order to fix the weld that broke on the steering column. We are going to fabricate a small 90 degree aluminium bracket to hold in place I also had to angle grind the frame so that it sits flat.