Years ago, I saw an article on how to build a chassis dyno at home. The
load cell was an interesting concept : it was basically just a 55 gallon
drum, laid on it's side, suspended by a fairly large shaft through the
center and 'pillow block' bearings in the center of the original lid and
bottom. The shaft had 'paddles' welded to it as did the inside of the
drum. The shaft was mounted in other bearings, and also carried the
traction drums for the car's rear wheels. The drum was partially filled
with water, and was arranged so the water level could be adjusted.
In operation, the car's rear wheels turned the shaft, which churned the
water inside the drum, and exerted rotational force against the drum.
The drum was kept from turning by a large 'calibrated' extension spring,
which had a ruler to measure the amount of extension. There was a
separate tachometer to read the speed of the shaft.
So, you adjust the amount of water in the drum to get the desired speed,
then measure the extension of the spring (which is pretty much directly
proportional to force) and compute the power from the force, the radius
from the center of the drum to the attachment point, and the speed of
the shaft.
The absolute accuracy is probably not the best, but relative readings
should be pretty good (and that's usually all you are really interested
in, anyway).
These days of course, the recording accelerometers are much more
practical <g>
Randall
Chris Crisenbery wrote:
>
> Thought I would start a new thread, looking at building (or buying) a
> flow bench for small bore cylinder heads and a dyno for 4 cylinder
> engines. I have collected a few articles on the flowbench but they tend
> to differ quite a bit on how they measure flow and what equipment I
> need. So I'm looking for input from my fellow shop-talkers.
>
> Thanks
>
> Chris, Rascal Racing
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