12/7/2016

For this week, most of my time was spent cading new mounts for both the motor and the brake. the brake is now facing between the two bogie, where the most mounting space is available. The motor mount takes advantage of the pre existing bolt between the two bogies which are already used for the wheel bearings. The mount itself bolts together using 1/4-20 bolts and I am currently working to see the tear out failure for these bolts. Also, I 3d printed these mounts so they can be fixed to the pre-existing model that Michael had cut out.

I should also mention that the mount for the brake with going to be made out of 1inch tubing, using the same material as the bogie cross-members

11/30/16

I cannot say that I have been doing much for the project over the past few weeks. What I have been doing is thinking about how to mount a caliper large enough to clamp down on the rail from the bogie to act as a brake. Knowing that we are limited on fund, I ask some family about any parts that were available for making the braking system. As luck may have it, they can provide us with some calipers and master cylinders from older cars that can be used on the bogie. The downside is that there is no way to tell how large they are or what process will need to take place to make them work for the system. For that reason, only rough estimates can be made about the size and the orientation of these caliper parts until they can be acquired. Otherwise, the mounting of the motor need some reworking to be more effective given the limited space.

 3d printed models of the motor and the bevel gear have been made in order to have an object to compare with the bogie team’s rapid prototype. Providing a better idea of where the motor will ultimately be placed as well as where a caliper can be mounted without being in the way of other crucial components.

Although this is not easy to say. I am not sure what I can do about braking at the moment. I can pick up any parts that my dad can provide and use them in the system accordingly. Yet, the first chance that I will get to acquire those part will be over winter break, so the design for that may be held off until then. 

11/16/2016

For this week, not much can be said, I met with randy to further discuss braking options, and it is becoming increasingly clear that we are going to be limited on size. For the motor that I recently got a bid for, I am still working to figure out if it is capable of handling the back emf needed for engine braking as well as determining where it will become to hot from the process. In addition, I am working to fit a band brake to work with the motor in the bogie assembly, but tolerance is still an issue.
 In addition, I have rework the motor cad model to better resemble the new motor that I have chosen, I am still getting a few of the detail modeled and will apply it to the master cad model later this week. With the reworking of the motor, the mount, shaft, and gear will have to be alter to handle the different size for the output shaft of the motor,. The gears for replacement have already been selected of the McMaster Carr website and will be added to the bill of materials.

11/9/2016

This past week I have contacted a few companies with regards to acquiring a motor with the specifications that we need to move a 600lb pod-car assembly. Out of these companies, I got a response back from one, giving me a quote for the prices of two motors with the specifications that we need. Due to the change in motor, I am still working on updating a few things for the bogie design, placing that motor and gears along with it. Looking at the current design, it might be a more viable option to use motor braking compared to using a physical brake just to save space. We are still looking at brake designs and seeing if we can fit it in the main bogie, but not much can be said until then.

10/26/16

This week was spent more on cad than anything else, with the motor already selected, it was relatively easy to model the motor as well as a mounting bracket to attach it to attach it to the bogie as seen in the images below. In addition, a bevel gear, which was taken from a part supplier site, was mounted to the drive shaft of the motor and bogie, rotating the motion by 90 degrees. As fair as the brakes are concerned, we would have to go with something more compact than a disk brake to fit it onto the main axel. Even the smallest disk brake, which can be seen in the images below cannot fit into the tight space where the gears and motor are located. For this reason, we are looking at using a belt brake, which are typically used on pocket bikes due to their small form factor

10/19/2016

After weeks of calculations and determining various frictions, we have finally decided on a motor to use in the bogies as seen in the link below. Due to the lower power and high torque requirements needed for the bogie to move under solar power, the bogie itself will move quite slowly with the use of these motors. Although as we process further into the semester, the gearing can be altered to make the machine go faster than previously calculated due to having a lighter load than originally estimated (600lbs).

Motor
It should be noted that this motor will be geared to run at 45Nm at about 8rpm, running at 4 amps and 24 volts per motor. These motors already have gear boxes attached, in this case planetary which allows for the greatest gear reduction given the size. Due to the length of the motor, a few beveled gears will be needed to change the direction of the rotation, allowing for a chain to drive the wheels of the bogie. The brake will also be mounted to the shaft driving the chain and the caliper in a similar way. I am still working on the cad models for everything and those should be done over the weekend.

Further research is needed for finding a master cylinder for the brake caliper as well as a reservoir for the brake fluid.

10/12/16

This week, I spent time looking at gearing as well as the motor in general. The original idea for the motor was to use one that was 24volts and  200watts. Under the assumptions that the amount of power that could be delivered to the motor was 75 watts, divided up as 24 volts and 3.3amps. The motor could produce a torque of .275Nm. Considering the assumption that the bogies and pod weights 600lbs, the amount of torque needed to turn the 6 inch wheels would have been 35Nm. Meaning that the motor would have to be gear 1:125 just to turn the wheels. The 35Nm doesn't even include the gearing losses, rolling resistance, and bearing frictions, which would bump up the 35Nm to 42Nm.
At this point, there were only two options that could be taken, try and gear down the motor to the point it could turn, or use a larger motor with more power applied. Looking at gearing, there were a few different possibilities, worm gears, planetary gears, and simple gear chains. Worm gears were considered for a time considering the amount of torque they can convert given a limited space. Yet, the problem was that once the motor stopped turning, the wheels would completely lock in place due to the nature of worm gears, which would make braking difficult to do slowly. Using planetary gears would have the benefits of efficient motion conversion. Yet, due to the complex design, and need for specialty gears, it was not an option worth seeking. Finally, with conventional gears, the design is easy enough to create, but using this method to gear down a ratio of over 100:1 wound result in a large gear chain with similarly large gears.
Due to gearing being a rather difficult to produce, I started to look at using a different motor, possibly one that is 48 Volts instead of 24 volts and at a higher amperage, say 9 amps. Under those conditions a 400 watt motor can increase the stall torque to something more reasonable for this project.