andrewturner
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| posted on 15/4/07 at 01:06 AM |
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Home built Dyno
Is it possible to build a dyno from scratch.
Could I use a reduction box on the flywheel to get an increased moment of inertia for the torque requirements.
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turbodisplay
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| posted on 15/4/07 at 07:40 AM |
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Most dynos use a motor used in reverse, ie alternator, to could get a cheap surplus motor, connect it to some sort of heater to dispate heat. (prob a
large water heater, that way you can run water to get rid of heat into the drain. (would only neeed a fairly modest flow.
Measure voltage, current and phase angle of current and amps (phase angle may not be important as it is a resistive heater).
Darren
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oadamo
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| posted on 15/4/07 at 09:01 AM |
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i looked into about 2 year ago i built one at work but i went for the box on each wheel with a basic chip and magnectic sensor for just power runs. if
your brave to spin it up with cheap rhp bearing to 7000rpm (i s**t myself the first time i went for it) i did look at the rollers in the floor idea
but the size of the rollers and where to keep them was a prob but you could use a trailer. in the end i used a g-tec meter of ebay cheaper and
safe.
adam
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cossey
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| posted on 15/4/07 at 09:03 AM |
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what are you planning to use it for?
for power curves a inertia setup is fine but for mapping you need a braked dyno.
i wouldnt have though finding a motor/alternator that can absorb potentially 100kw+ is going to be easy or cheap.
the other two options are eddy current and water brakes. eddy current uses a flywheel with magnectic coils. when the coils are energised the flywheel
moving through the magnetic field cause currents to flow in the wheel generating heat and slowing the flywheel down. you vary the current in the coils
to vary the torque.
the main problems with running a dyno is heat and fumes. having run our formula student dyno for a year i wouldnt try building a dyno at home. the
hassle and money required for it to be of any real use is big, far bigger than you would expect.
if you look at how much dyno time costs to hire it isnt really worth it.
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gingerprince
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| posted on 15/4/07 at 10:54 AM |
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If you just want power plots you can use something like this: -
http://www.charm.net/~mchaney/homedyno/homedyno.htm
Basically you accelerate through your rpm range in a specific gear and record from an induction pickup to a wav file. Software takes ths to figure
out rpm over time, give it weight, gear ratio etc and gives you a plot.
Not accurate enough to say "my car has xxx bhp" but handy for comparison purposes if you want to "tune" something and have a
before/after plot.
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turbodisplay
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| posted on 15/4/07 at 11:10 AM |
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Re motor, i was thinking that surplus suppliers would be a good bet, or some closed factory being demolished?
If you made a dyno you could run a few in parrallel.
I recon 4-5 10-20 kw motors will take 300hp for les than 5 minutes due to thermal mass.
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oadamo
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| posted on 15/4/07 at 11:18 AM |
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just put load the shaft with a brake disc but you will need a load cell and you will need the no the mass of the rollers size/weight i bet your
looking at £500
to get the rollers made
adam
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turbodisplay
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| posted on 15/4/07 at 11:25 AM |
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What about a dyno bolted to the hub directly.
Using that it would not require rollers, each hub would be measured seperately.
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oadamo
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| posted on 15/4/07 at 11:46 AM |
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thats how i made them in the end with a sensor but you can only do max power runs with it. i didnt even try to load them lol bad idea with such a
small box on the end. would of been a cheap arch rolling device lol. i welded a bar across the boxes and put the forks off the fork lift on it to hold
it down scrary s**t lol. i only done a few runs then i got a g-tec meter you just put in the weight of the car and cain it up and down the road it
gives you 0-60 braking times g force
adam
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smart51
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| posted on 15/4/07 at 04:27 PM |
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I used to work for a company that made rolling roads. We used to demonstrate them to customers on the shop floor, i.e. not in a pit. The car's
wheels would therefore be at head height.
We sold one to Dodge to test their Viper in the factory. As I got up to 90 MPH, the assembled crowd backed away quite a lot. You don't see
whats going on in normal use.
So I'd say no. You can't build one at home. If you do though, the best way to lose the power is through heating water. 150 BHP is 112
kW. You'll need a big generator fixed to the rollers, the heating elements of 56 kettles. At 150 BHP, you'll boil a 100 litre tank of
cold water in 5 or 6 minutes.
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iank
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| posted on 15/4/07 at 07:08 PM |
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quote:
Originally posted by turbodisplay
What about a dyno bolted to the hub directly.
Using that it would not require rollers, each hub would be measured seperately.
Like these ones:
http://www.parr-uk.co.uk/porsche-performance/dyno/dyno.html
--
Never argue with an idiot. They drag you down to their level, then beat you with experience.
Anonymous
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blueshift
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| posted on 15/4/07 at 11:46 PM |
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I work with a dyno. I have considered homebrew ones.
In short my opinion is - don't do it. You will either spend a lot of money or hurt yourself or both.
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