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Old 12-08-2007, 11:37 AM   #46
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So read through this thread, followed the links and read through that stuff as well and it got me thinking - how hard would it be to make a break-in stand into a dyno as well?

I can plot out most of it in my head - just not the PC interface and software component portion.

In theory you can take any of the stands and do it from a physical standpoint. A dyno really is nothing more than a known, constant load and power is calculated based on how quickly the engine can spin that load up.

SO take it a step further - if you calculate (or know) the load one of the break-in fans creates you are halfway there. Add in some method of measuring RPMs (probably as simple as making a hall effect or optical) and you have the dyno.

The catch is how the hell do you take that RPM reading and get it into a program that takes it along with the known load, calculates the HP curve and then plots it?

The only other issue I see is that the fans may not produce enough load to accurately measure HP.

Hell there is enough stuff out there that realistically, the software component IS the only real stumbling block, unless you are a programmer. All the telemetry you can shake a stick at is readily available, weather stations for SAE-correction are a dime a dozen and there is enough creativity out there that building an RPM reading component is as simple as tearing a mouse apart and strapping a CD to the fan.
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Old 12-08-2007, 12:55 PM   #47
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Quote:
Originally Posted by Drew Manzella View Post
So read through this thread, followed the links and read through that stuff as well and it got me thinking - how hard would it be to make a break-in stand into a dyno as well?

I can plot out most of it in my head - just not the PC interface and software component portion.

In theory you can take any of the stands and do it from a physical standpoint. A dyno really is nothing more than a known, constant load and power is calculated based on how quickly the engine can spin that load up.

SO take it a step further - if you calculate (or know) the load one of the break-in fans creates you are halfway there. Add in some method of measuring RPMs (probably as simple as making a hall effect or optical) and you have the dyno.

The catch is how the hell do you take that RPM reading and get it into a program that takes it along with the known load, calculates the HP curve and then plots it?

The only other issue I see is that the fans may not produce enough load to accurately measure HP.

Hell there is enough stuff out there that realistically, the software component IS the only real stumbling block, unless you are a programmer. All the telemetry you can shake a stick at is readily available, weather stations for SAE-correction are a dime a dozen and there is enough creativity out there that building an RPM reading component is as simple as tearing a mouse apart and strapping a CD to the fan.

the props used on the breakin bench's actualy produce too much load... most motors cannot spin them much past 30 000 RPM...plus it seems the rapid air passing over the carb causes weird tuning issues... it seems to create a negative venturi effect..adding a offset airfilter helps, but still isnt a perfect solution... a person is much better using a machined wheel geared down.... i beleive a 12lb mass would be about right..
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Old 12-09-2007, 07:12 AM   #48
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Well I see a huge problem with trying to do what your pondering.
1: the engine needs to "free rev" to get up to its intended power range and then you "pull the load" This will show max HP
2: then you need to "pull a load through the rpm range" to see what sort of power curve you have.
This is why dyno's are so expensive ,you need a counter force and program to run and adapt this counter force. The formula for calculating HP is pretty easy with a propeller if you can find the correct diameter and pitch , BUT and this is a huge BUT , after a certain rpm things start to get pretty hairy and things can come apart! Those model engine props are not rated to turn much over 25K RPM'S , and most car engines are just coming into it at that speed.
So beware. I have seen blades shed and the out come is catastophic!
(used to build F1 pylon engines)
And as for dyno data, It's fine for an idea as to what your looking for ,but I definately would not base an engine choice solely on this info!
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Old 12-09-2007, 03:18 PM   #49
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I can see where the propeller force and air drag will be different at different RPMs. That would make it more difficult to see reliable data. I wonder how much you could determine by simply measuring RPM at WOT from one engine to another. I would think it would say something about max power, but not necessarily throttle curve or max torque.
Perhaps if you measured WOT from one engine to another with different angled props. With a sharp angled prop, I would think would tell you more about torque vs a narrow angle would tell you more about max power.

Am I way off or would this allow some comparisons?

I started a new thread specifically for dynos since we got off original topic.
Please respond in new thread. I will copy this to that thread also.
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Old 12-10-2007, 05:03 PM   #50
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sorry... didnt see that the thread was renamed
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Old 12-20-2007, 06:21 PM   #51
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Who carries the nanda?
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