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Treadmill Dyno
SparWeb:
--- Quote from: taylorp035 on November 11, 2010, 09:45:48 AM ---A major issue that we haven't solved yet is whether or not we can actually put all of the power on the ground. The reason I say this is that we will probably have about ~60 ft*lbs of torque on the rear wheel, which is way too much. Last year's car accelerated at about 2 m/s^2 and this year's car will be a minimum of 3 m/s^2, which is like a rocket. Most of the car's there probably accelerated at about 0.5 m/s^2 or less.
--- End quote ---
Ah, engines aren't they grand? 80% of the time you only need 20% of their power and the other 20% time you need at least 80% power. And yet you have to carry around the full weight of the thing 100% of the time!
Okay you obviously don't need me distracting you with jealous vicarious commentary so get back to work!
taylorp035:
--- Quote ---Goofy thought...
Add another wheel?
One with brakes that would drop down to the ground when the brakes are applied?
8" plastic kids scooter wheel with tube tires kind of wheel?
--- End quote ---
The thought had crossed my mind and several of my teammate's minds before. We were seriously thinking of going Fred Flintstones style with the brakes, maybe having a handle that would drag on the ground. I think this year's design is much better when it comes to stopping, so we shouldn't have any issues.
--- Quote ---Okay you obviously don't need me distracting you with jealous vicarious commentary so get back to work!
--- End quote ---
:) We usually have our meetings every Friday night, from 6:30 til midnight or later. Last time we stayed until 1:30. I am almost done with my second paint test, where I sanded a test piece of carbon fiber (6x8") and I painted it with white and blue Krylon spray paint. Today I put on 4 layers of clear coat and tomorrow I will wet sand it with some 1000 grit sandpaper. I think I put too much paint on it because some of it is crackling. The first layer was good, but I think I put too much of the second layer on (roughly 24 hr's later).
dnix71:
Are pneumatic tyres a requirement? If not then why not use a solid wheel with a rubber tread. If not that, the fancy cars have had wheel speed sensors that make it impossible to "spin ze tires" on your BMW or Mercedes unless you mod chip them first. Maybe a throttle feedback control with optical sensors aimed at the ground and the back tire. If the slip exceeds a certain level, have a solenoid pull back on the throttle.
taylorp035:
--- Quote ---Maybe a throttle feedback control with optical sensors aimed at the ground and the back tire. If the slip exceeds a certain level, have a solenoid pull back on the throttle.
--- End quote ---
We should have enough sensors on this car to determine that ;D
For this project, I have spent ~100 hours on an Excel based MPG calculator. I can enter all of the variables known to man (engine efficiency, rolling drag coefficient, max engine rpm, air density, ....) There are 16 variables that you can change. On the output side, it gives you a mpg number based on your max and min velocities, and a mpg number that is the maximum possible + the speeds that you can achieve that number. More or less, the excel spreadsheet helps me get around some really nasty integrals and thinking that I don't want to do. It takes 45 seconds for the new answer to come up after you enter in the number. My last change to it was adding the kinetic energy of the flywheel into the equation.
The results says that we should go from 10 to 21 mpg and start the engine 16 times. It comes out to 4200 Joules per coast, so about 5.6 hp * seconds.
--- Quote ---Are pneumatic tyres a requirement?
--- End quote ---
No, but the improvements would be only better if the road was perfectly smooth. The track that we race on is meant for dump trucks, so there are some decent cracks in the pavement. Putting solid tires on a car with no suspension would be crazy. You are right that it could be better, but it would make for a very heavy tire and the tires that we use are already really good. Rolling resistance of a steel wheel would be ~0.001. Our tires are about 0.002. We own a tire that can go as low as 0.0008, but it's $200 a tire.
taylorp035:
The windmill is officially no more. I pulled the motor like I said I would. I then neatly stacked the wood components and all of the corresponding bolts in my basement, right next to an older windmill and my pile of VAWT blades.
I then took the motor to school, which I hope in 2-3 months we will have a running electrical dyno.
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