Homebuilt Motorcycle Dynamometer

Homebuilt motorcycle dynamometer

How many projects begin this way? You see something that looks cool and think, "I bet I could build one of those" and next thing you know you're making sketches. Steve, a motorcyclist from Melbourne, Australia, watched a motorcycle dyno shootout and figured he could build his own dynamometer, how hard could it be? Well, it took him 3 years but he did it, he finally had his own homebuilt motorcycle dyno.

When I say he built his dyno, I really mean that. He wrote the software in Visual Basic, used a Basic Stamp microcontroller so the software could communicate with the hardware creating the data acquisition unit, had the drum built to his specs, put together a trailer to hold the whole setup and learned enough rotational physics to make the whole thing work.

The dyno he built is an intertia dynamometer, which means it's the more common type where a drum is accelerated by the motorcycle's rear wheel. When you record how fast the drum is accelerated through the rpm range, a measure of torque, you now have both torque and rpm throughout the range. With those two numbers you can calculate the horsepower at each point.

A very cool project overall, I like it.

Thanks for the tip, Andy!

Link: Steves DIY Dyno via Hackaday

Comments

  1. motoxyogi says

    I’m curious but how do they get the rpm info off the bike to the computer. Do they take it directly off the ecu or what?

  2. Nicolas says

    Don’t want to be painful, but how did he calibrate the equipment ? It works, fine, but is it giving the precise and accurate measurement ?

    Then, who really cares how much HP goes to the backwheel ?

    Sorry, I appreciate the good work done by this guy, it shows that what the average Joe (like me) belive to be complicated and out of reach, is actually accessible to everyone with a little bit of research, work and commitment.

    Keep on keeping on !

  3. garrett says

    ‘Then, who really cares how much HP goes to the backwheel ?’

    millions worldwide
    thats what people care about whp/wtq

    very cool!

  4. todd says

    Motoxyogi; you can hook up an inductive transformer around a plu wire (assuming you have plug wires). This is the same way a timing light works. Another method is to use a computer mouse scroll wheel sensor to pick up readings off the crank. You would plug this in your side cover and get it to read your timing marks – somehow-. I’m not sure how Steve did it.

    -todd

  5. Sean says

    It’s easier to do it the timing light way, but another way is to record the drum speed at a certain RPM. Take it up to 5000RPM, calibrate the computer, and then accelerate.

  6. Leland says

    Nicolas, the inertia of the wheel of the dyno is related to its weight, which can be measured relatively easily with quite high accuracy. Only bearing friction would cause error but I think it would be small. The RPM can be measured by using an optical tachometer which uses a small piece of reflective tape to bounce a light beam each time the tire rotates. I can see a white square spot on the rear wheel of the bike at about the 4:30 position in the picture.
    I admire the guy, the system looks very professional. I guess we shouldn’t be afraid to build what we want.

  7. JC says

    If one was only concerned with tuning and performance increases (and avoiding decreases by bad tuning/mods) the calibration wouldn’t be much of an issue if it was consistent with the results.

  8. Nicolas says

    I need to apologize for my approximate wording : What I meant is that the HP is given on the bikes specs, and imho it’s not really important to know if the bikes really delivers what’s printed on the brochure or +/- 2%, the real test bench is basically the rider’s arse and how he feels his bike.

    Sorry for providing a negative comment, I really appreciate the quality of the work from this guy. I’m just one of this retard who still thinks it’s not necessary to have 120+ HP at the rear wheel to have fun on a motorcycle. ;-)

    Thanks for the explanations, Leland. Now how do you measure the torque ?

  9. Sean says

    Personally, I’m with Nicolas on this. My bike gets 26 horsepower at the rear wheel, but it still gets me enough kicks in the real world. For tuning, a dyno is great, but other than that it’s just the wank factor of having a 140HP bike over your mates 135HP bike.

  10. Uglyduc says

    Dyno’s aren’t just for max hp readings but a power commander or knowledgeable carb tuner can improve the motorcycle’s entire power band. Dangerously lean fuel conditions can be spotted and corrected and with motorcycle manufactures barely passing new emission regulations some bikes leave the factory with dismal fuel injection settings.

  11. todd says

    I’m with you Nicolas. I’ve dyno’d an old 90cc Yamaha I have at 7.1HP. I figure there’s another 3 or 4HP to gain somewhere but the bike already breaks all speed limits.

    -todd

  12. Richard says

    “the real test bench is basically the rider’s arse and how he feels his bike.” – Nicolas

    That’s true if you’re just interested in enjoying the ride. But if you want to tune the bike to match aftermarket pipes or to work better at the track, then a dyno is indispensible.

  13. says

    Very cool! Congratulations. I’ve thought about what would be involved in building something like this and wondered if it was within reach for a homebuilder… Now I know it can be done. I love this project.

    Mike