Engine Dynamometer

[FPV_GTp]

has anyone made there own engine dynamometer or chassis(rollerroad) dynamometer ???

What electronics and hardware are you using to capture the data when running the dynamometer ? ie torque , speed to calculate the horse power.

Great tool for tuning the IC engine also , not just power figures . What datalogging do you use analog or digital system.



1. friction engine dynamometer
2. eddy current engine dynamometer
3. water brake engine dynamometer
4. inertia engine dynamometer
5. and many other different types of engine dynamometer


One of the www.cnczone.com forum members makes some nice electronics and hardware. His website is www.sportdevices.com.

Thats a free plug for there site , as i have no connection to this site . This is one of many on the world wide web listing.

If you have a website of your own just list it this thread. Or if you have a favourite website just list it in here.

A dynamometer, "dyno" or "dyn'r" for short, is a machine used to measure torque and rotational speed (rpm) from which power produced by an engine, motor or other rotating prime mover can be calculated. A dynamometer can also be used to determine the torque and power required to operate a driven machine such as a pump. In that case, a motoring or driving dynamometer is used. A dynamometer that is designed to be driven is called an absorption dynamometer. A dynamometer that can either drive or absorb is called a universal dynamometer. In the medical realm, hand dynamometers are used for routine screening of grip strength and initial and ongoing evaluation of patients with hand trauma and dysfunction. http://en.wikipedia.org/wiki/Dynamometer

[NC Cams]

There a quite a few DIY dynos that have been made for go-cart engines. SOme are simple hydraulic pumps based brakes and others are flywheel based intertia dynos.

A friend made an intertia dyno for testing go-kart engines and found suitable data acquisition equipment on the internet. I think some of the links are/were on/off the 1/4 midget association website.

Do a google for "go-kart dyno" and you should find a phethora of links.

Data acquisition for go-kart versus V-8 engined stuff is essentially the same. However, power absorbtion becomes the hard part.

Inertia dynos for engines that develop major amounts of power are very serious beasts. Not only is the speed of the flywheel an issue to deal with but mounting and containing it is NOT a task for hack and slash lightweights. The amount of power in even a 200hp engine's flywheel running at peak torque could put enough energy into the flywheel that would put it thru a wall and into the next county if it ever got loose.

We learned a very valuable lesson with 0.05hp R/C car motors and inertia dyno flywheels we were playing with at the time. The flywheel of the dyno came loose. The guy was using it in his den on a desk top.

It flew off the motor, danced across the desk, gained traction and ran across the room taking out the TV in the process. It then went on to climb up the wall paneling before it poked a hole in the ceiling. And that with only 0.05hp.

I think that Professor Blair has an SAE paper with a psuedo "how to" on a go-kart dyno. It might be scaleable to a V-8 if you can find suitable absorbtion hardware.

[FPV_GTp]

Originally Posted by NC Cams There a quite a few DIY dynos that have been made for go-cart engines. SOme are simple hydraulic pumps based brakes and others are flywheel based intertia dynos. A friend made an intertia dyno for testing go-kart engines and found suitable data acquisition equipment on the internet. I think some of the links are/were on/off the 1/4 midget association website. Do a google for "go-kart dyno" and you should find a phethora of links. Data acquisition for go-kart versus V-8 engined stuff is essentially the same. However, power absorbtion becomes the hard part. Inertia dynos for engines that develop major amounts of power are very serious beasts. Not only is the speed of the flywheel an issue to deal with but mounting and containing it is NOT a task for hack and slash lightweights. The amount of power in even a 200hp engine's flywheel running at peak torque could put enough energy into the flywheel that would put it thru a wall and into the next county if it ever got loose. We learned a very valuable lesson with 0.05hp R/C car motors and inertia dyno flywheels we were playing with at the time. The flywheel of the dyno came loose. The guy was using it in his den on a desk top. It flew off the motor, danced across the desk, gained traction and ran across the room taking out the TV in the process. It then went on to climb up the wall paneling before it poked a hole in the ceiling. And that with only 0.05hp. I think that Professor Blair has an SAE paper with a psuedo "how to" on a go-kart dyno. It might be scaleable to a V-8 if you can find suitable absorbtion hardware.

Hi NCcam

You mate was lucky he and anyone else wasn't hurt when the flywheel started to dance across the room

You hear of many people getting killed around engine dynos in the old days > As there wasn't enough safety features built into the dyno test cell.

Imagine some object weight spinning at 6000 to 20000 rpm and coming loose .

I have a few engine dynos at work , was just curious as to what guys from this forum use and have made themselves.

cheers

[M-man]

I did help a friend build one, just 6 months ago, works OK, on small engines anyway. It was the waterbreak model..

[WARIEL]

Isn't There A Drum Involved? If So About How Big Would You Need For Say 20 Hp Or For Go Kart ,lawn Mower . I Can Only Machine About 10 Inches Or 250 Mm. Always Wanted One Didn't Really Know Where To Start On One. How About Calibration?

[NC Cams]

The size (inertia) of the flywheel determines how fast the power input buy the DUT (device under test) can accelerate the wheel to a terminal velocity.

Inertia is a function of mass AND diameter. In an arbitrary case of a 12" dia flywheel and a 10" wheel, both with the same MASS, the 12" wheel would have MORE inertia and accelerate LESS quickly with the same power input. The RATE OF CHANGE of speed, integrated over the whole RPM trace, deterimes the power curve of the DUY.

To calculate the flywheel size needed, you firts need to understand inertia and how it is calculated. Once you do that, a flywheel diameter and mass can be calc'd for the particular engine.

One more thing, you can't just do a calc for "20hp". Why? because an engine that only runs at 2500 rpm (diesel) has a TOTALLY different power (torque at the instantaneous RPM) curve than one that runs 6000 rpm and both make the same rated power. Afterall, torque output is what is accelerating the load and torque is what you're measureing with a dyno.

Only when you then multiply the instantaneous torque but the RPM factor, do you derive HP. Torque is what your'e measuring/making/ultimately improviing when you "make more power".

[FPV_GTp]

Originally Posted by WARIEL Isn't There A Drum Involved? If So About How Big Would You Need For Say 20 Hp Or For Go Kart ,lawn Mower . I Can Only Machine About 10 Inches Or 250 Mm. Always Wanted One Didn't Really Know Where To Start On One. How About Calibration?

Hi

Do you have a RPM and torque figure for any of these engines you interested in testing ??????

Note that a dyno never measures horsepower; it can only measure torque and then use the formula ( horsepower = torque * rpm / 5252 ) to get horsepower.

Cute Land & Sea's DYNOmite Kart Chassis Dynamometer with a waterbrake



Cheers

[NC Cams]

You can and must calibrate a brake dyno, especially the load cell. This is usually done with dead weights.

An inertia dyno is pretty hard to "callibrate". Once you PROPERLY calc the inertia, the rate of change of RPM over time tells you how the engine's torque curve changes over the time/load interval.

NOTE however that BRAKE HP is not the same as HP measured via an inertia dyno. It corelates but it is NOT the same. In a water brake or electric dyno, you literally load the engine at WOT to stall it at an RPM and read the "brake torgue" at the RPM.

On a inertia dyno, you never totally brake the motor as it is accelerating a load. If you size the flywheel so that it allows the engine to accelrate at a comparable rate as seen on the track on a particular stretch, you can then see if the changes you made will translate directly to track performance improvments.

Otherwise, callibration of an inertia dyno is purely A vs B or back to back comparisons. Since inertia stays constant, it is a good repeatable test that is probably not going to be as stressful to the engine as a brake dyno test.

Reason: shorter test and less time under load.

[WARIEL]

My Family Runs Dirt Late Models My Brother,dad, And Myself, I Got The Chance To See My Brothers Motor On The Dyno. On This Dyno They Only Did Two Pulls And Then They Never Adjusted Anything To Improve The Torque Or Hp. They Ran The Engine Till Warm Reved It To Clean It Out Held It At Say 3500 Rpm Flipped A Switch Or Lever And The Motor Almost Died Then Revved It 8600 Rpm And Shut It Off. This Is The Kind Of Dyno I Want For My Go Kart Which After Running Late Models Even The Expensive Parts Are Cheap. I Dont Know How Much Torque Im Looking For I Just Want To See How Much " I " Can Get From A 5 Hp Brigg Flat Head. I Really Dont Need A Chassis Dyno But Rather An Engine Dyno. Thanks

[WARIEL]

According To Fpv Gtp's Formula @ 8000 Rpm I Need 13 Ft Lb.s Of Torque. How Hard Would It Be To Have Cosistant Results Or How Safe Are Tranmission Dynos. I Found One In My Machinist Hand Book. It Looks Like Its From The Stone Age . You Put A Band Around A Flywheel The Run An Arm Off Of That To A Set Amount Of Weight And I Assume Try To Lift It .

[M-man]

The wheel were about 160mm and power that have been messured are around 70 HK... I can get a sketch later on, and mabe get som pics/movie of the brake(ing) and on the parts involved..

[WARIEL]

Thank You 160 Mm I Can Do. 70 Hk Im Not Familiar With. I Dont Mean To Be Picky But If You Could Post Pictures In Bitmap Form .bmp .i Have Limited Internet Access At Work.