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Treadmill Dyno

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Over the last few weeks, I have been hard at work on my new supermileage car.  We have finished a new FUEL INJECTED Briggs and Stratton 3.5hp engine.  The problem is that our old dyno that is used to test these engines is really hard to use (it's a water brake, but controlling the resistance is super touchy).  So, the new plan is to use my treadmill motor and a large array of light bulbs to make a variable load.   This way we can effectively test the engine and fine tune it to be more efficient.  It should put out  about 120v, so we should be able to run light bulbs with no problem + keep the current down.

The motor is rated for 3960 rpm @ 150v and 16 amps continuous.  The engine red line is ~4,000 rpm.

The car we are building should weigh ~80-90 lbs empty and get 1500+ mpg on a stock engine.

In the end, this means that I may have to dismantle my windmill.

Here are a few pictures of the car and the engine so far.  Improvements include a brushless starter motor, throwing out the lead acid batteries, full ceramic bearings on all three wheels, a drag coefficient of ~0.11, a plate clutch that allows the rear wheel to spin freely, a higher gear ratio of 12:1, wheel skirts, a speedometer good for 0.1 mph increments, and a very ambitious computer that will automatically control the plate clutch using a 5th scale airplane servo, the starter motor, the fuel pump motor, calculate the grade of the road and figure out instantaneous acceleration, mpg, and efficiency, and it will control when the engine shuts off.

I can't wait until I get some wheels on it.  The rear one should be on by this Friday.  The fronts are waiting for their hubs, which have drum brakes made in England.


--- Quote from: taylorp035 on November 06, 2010, 05:34:23 PM ---In the end, this means that I may have to dismantle my windmill.

--- End quote ---

Whatever it takes, man!
Ceramic bearings are bloody expensive aren't they!
You can't start with a rip-cord?  Contest rules?
If this is a college team project for you, these can be very memorable.

I remember those engine/dynamometer tests in college, too.  LOTS of fun. 

I look forward to seeing the evolution.

Well, you could use a pull start, but we only run the engine for ~2 seconds and then coast for a minute.  Doing that 20-30 times would be annoying.  There was ONE team that had a pull start last year (out of 25 ) and they modified a cordless drill to start their engine before the 2 days were up.

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.

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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