A Nitro Engine Dyno

Discussion in 'RC General & Getting Started' started by rockn82, Mar 4, 2004.

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  1. rockn82

    rockn82 Marx Brother

    I have now been toying with the idea of making a nitro engine dyno. But I am having some trouble in just a few areas... Right now it is set up so that the nitro engine sits on a stand and has a gear mounted to the crank in front of the flywheel. The gear meshes with two electric motors. One motor has a 7.2V battery hooked up to it for the purposes of putting a load on the engine. The other motor is "SUPPOSED" to measure the RPM of the engine. The whole point is to have the engine being dyno'd stall when a specified load is place on the engine. The rpm of the engine at the point where it died would be the torque @ rpm point. Now do the test at every 5000 Rpm and you have a nice bell curve graph to display everything you need to know. As we all know already you can figure out horsepower from that. Ok, back to the problem, I am using a multi-meter to measure the amount of voltage comming from the "RPM motor" and converting it into the RPM reading. And the same is applying to the amount of torque the "Stop motor" is putting out. I just need some help determining how much voltage is what RPM and What torque. Now I know that there are many of you out there that deal with electric and do some serious modding. Is there a different way to measure the amount of torque or rpm coming from the Motors. Is there a better way. Any Ideas would be greatly apreciated. Since the Ultimate task at hand is to build an OS .15 CV-R that puts out 2.5 HP. Or at least that is the challenge. LOL. Input would be greatly appreciated.
  2. mastmec

    mastmec Member

    The only way I know to get an acruate RPM reading is with a mechanical tach or a sensored tach. Machanical tack would run on the motor shaft or other gear then you would figure the RPM by the ratio. Sensored, you need a metal tag on the gear(plastic) like foil tape or similar and have a sensor read it. Just about any magnet coil with two wires will work, as the tag passes the sensor it puts off a pulse, which you can read by hertz on a DVOM or scope if you have one. Using a motor will give you a reading, but sence there are three segments on the com. that would be fun to figure out, but it would give you a reference RPM but not actuall.
    Torque, I know you can use airplane props at different pitches to get a load calculation on electric motors by the amp draw( I don't know how that helps you) well I lost my train of thought, I'll be back.
  3. rockn82

    rockn82 Marx Brother

    lol. I had the idea of a magneto like system. And tried it once already. The problem was at 30000-35000 RPM the metal flew off...still havent found it LMAO...But now you have just given me a good idea. two screws, spaced evenly. Then all you would have to do is divide the readings by two. And I suppose I can commendeer and ociliscope. That mechanical tach sounds promising though is there one already out there? Are they spendy? I'll have to do some checking... Once I get the RPM down pat then all that's left is the torque. I was thinking of maybe a Spring pulling a guage across a scale that represents pounds. Kinda like a Fish Scale. But I cant figure out how to attach the spring to the crank or flywheel so that it doesnt just destroy the spring by turning too far. So I would need some sort of slipper effect. Ultimately canceling out the engine dying at a certain load. Yep needing lots of ideas here. LOL.
    Holy I just found the perfect one....for $249.00. LOL heres a link:
    http://www.checkline2.com/product.php/id/125806/lang/en/buy/yes
    Time to start checkin EBAY. :) Now for that load.
  4. mastmec

    mastmec Member

    Here's the one I designed.
    [file]engine_dyno.jpg,4517,,0[/file]

    Just kidding, but if you want one, it's only $6,500.00
    Pocket change right?
  5. mastmec

    mastmec Member

    Hey, train pulled back in..OK, if your building one from scratch, I think you would have to build one for an electric motor, and find the load calculations from it, then addapt it so you can run nitro engines on it. Use your load motor and configure a dial for load like a potinchiometer (spelled wrong) to have variable load. Or you could just get an old Tekin motor dyno and mod. for a enigne to fit, but still be able to test electrics too.
  6. mastmec

    mastmec Member

    One other option for getting the correct RPM is to buy the new Venom Speedometer, has the sensor and a tiny magnet.
    As for load, I thought of hooking up a small alternator, and small lawn mower battery.
  7. bandit1

    bandit1 Member

    engine dyno is cool, but how about a chassis dyno? i think that you would be able to get just as much good information out of that. Ive seen good 1/1 scale chassis dyno's that measure not only HP to rear wheel, and other things, but also HP of the engine too.
  8. mastmec

    mastmec Member

    Hows this one?

    [file]car_dyno.jpg,4517,,0[/file]
  9. rockn82

    rockn82 Marx Brother

    Uh oh now you really got me thinkin... Ya never shoulda shown me that pic. Is that a stepper motor on the end of that with load coils?
  10. mastmec

    mastmec Member

    I think it's just load coils w/ an arm. I trying to find some specs on it or one like it.
  11. rockn82

    rockn82 Marx Brother

    the only thing I would have to adapt on that is getting rid of that clutch bell. LOL. Or just deal with the slippage. But the numbers would look better without it. :)
  12. bandit1

    bandit1 Member

    mastmec, thats exackly wat i was thinking of when i was thinking baout a chassis dyno. Where'd you get that pic from?? I wanna check out more about it. thanks, very cool pic
  13. mastmec

    mastmec Member

  14. rockn82

    rockn82 Marx Brother

    Well I did some calling around and asked Land and Sea about getting just the load coils (eddy current unit) and the software. I guess the price aint too bad if you own Microsoft. $8000.00 LOL I guess I am just gonna have to do it the old fashioned way.
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