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Treadmill Dyno
SparWeb:
--- Quote from: taylorp035 on November 08, 2010, 04:36:56 PM ---As for the ceramic bearing, yes they are very expensive. The ones we have ran $60 a piece x 6 ..... and we are not exactly sure what the advantages are. A big difference will come from the fact that last year's bearings had seals and the ceramics don't. I did some very rough calculations and came they to a 2-10% increase in mileage.
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Once was looking into ceramic bearings as a replacement for steel ones. As I remember it wasn't the seals that robbed as much energy as pre-loading forces... The problem at the time was heat build-up not auto mileage so nothing I can remember related to that.
--- Quote from: taylorp035 on November 08, 2010, 04:36:56 PM ---
Right now I am looking into exhaust and intake tuning, which could prove beneficial. I am also looking into heating the engine up with resistors since the engine is almost always cold and engines don't like to run when they are cold. I am looking at about 30,000 J, which should be enough to heat a small briggs block by 50-80 F.
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Maybe you could direct the exhaust gas back directly over the head's cooling fins? Suicidal for an engine that runs continuously, of course, but if your bursts of engine use are short enough... Box up the engine so that the vehicle's airflow doesn't also cool it... Hmm Can't do the first suggestion and the second at the same time.
A good source of ideas, at least as far as the chassis is concerned, could be the international solar car race websites and blogs etc.
Google "North American solar Challenge". Hints about how to handle the "panic" and "mad scrambles" on race-day may also help.
taylorp035:
We were thinking of routing the exhaust so it would go through the fins and then out the exhaust pipe. As for airflow, there is none. The engine bay is pretty well protected. There might be a little air going through the rear wheel, but I doubt very much.
As for the chassis, we don't have a frame made of metal. It is really just the body with some carbon fiber ribs inside. All we did was wrap pink house foam with carbon fiber and it is super strong.
Today I just spray painted a test piece of carbon fiber with white Krylon paint meant for plastic. I will then spray it with clear coat and then wet sand it with some 1000 grit sandpaper.
I also saw for the first time our rear hub, made out of a solid chunk of aluminum. It is extra special since it is narrower than a standard bike hub, it will accept the new ceramic bearings, the one side will have the interrupter disk for the speedometer (120 tooth), and the other side will accept one half of a hydraulically operated plate clutch. The rear wheel should spin for ever. I saw a video on line where a guy spun a wheel with almost no effort and it spun for 8 minutes with the ceramic bearings, compared to 1 minute for the hybrid ceramic and 30 seconds for the steel bearings.
SparWeb:
--- Quote from: taylorp035 on November 09, 2010, 03:46:39 PM ---We were thinking of routing the exhaust so it would go through the fins and then out the exhaust pipe. As for airflow, there is none. The engine bay is pretty well protected. There might be a little air going through the rear wheel, but I doubt very much.
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Then watch out that exhaust can't accumulate in the cabin, if it gets out of the many joints and bends in the tubes. You will need a firewall of course, so maybe sealing that up is not going to be difficult.
taylorp035:
We will have a firewall, as it is a requirement in the rules. I'm not sure that it will be 100% air tight, but it should be pretty close. It will not matter anyways, as the exhaust pipe must stick out side of the car.
--- Quote ---Google "North American solar Challenge". Hints about how to handle the "panic" and "mad scrambles" on race-day may also help.
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I did this competition last year too, and it was a blast. Our car worked for the most part last year, minus the brakes and the starter motor wanting to fall off. Luckily, you rarely need brakes and the starter came unbolted at the very end of a run (9.6 miles), so it didn't hurt our mpg. One of the difficult requirements to meet is the braking test, which we must show a 0.25g's worth of deceleration, which is really hard to do on super thin tires and a weird weight distribution. Last year it took me 7 attempts to pass the test, mainly b/c only one front brake was working. The year before, they had the brake on the rear wheel, which made it almost impossible to stop the car. If you lock up the tire, it instantly blows, so there is no room for error. This year, we are using dual drum brakes up front. These brakes are only found in trikes and wheel chairs and they are only sold by a shop in England.
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.
Last night, we got our new budget passed, so we now have another $900 to spend. The car will probably end up costing in the ball park of $7-8k, which is a lot of money. Some teams spent $40k + last year.
ghurd:
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?
Maybe even use it as the drive wheel, retractable drive wheel, since the vast majority of the time the car will be coasting (????).
G-
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