DIY Dyno

[Jeremy Harris]

Thanks.

It's nice to know that someone else had a very similar problem with the disc brake idea. I guess I could have tried dual callipers, but I only had one spare brake in my junk pile..............

I'm hoping the eddy current brake will turn out to be smooth and easy to control. I've done a fair bit of reading up on eddy current brakes, both from web searches and from some helpful papers that Bigmoose sent me.

The motor mount has very little friction and, as you've spotted, the bearing area is pretty large. There are stops that restrict the torque arm to about 80 degrees of movement, albeit accidental ones (the securing screw interfere with each other and limit the angle the arm will turn). I powered it up this evening, with no load, and it spins OK. I just need to remember to check the motor direction carefully before applying any load.

Those home-made big dynos look seriously scary. Years ago I was asked to take a look at a problematic fault in the new engine control system for our Challenger main battle tank engine. This meant working inside an engine test cell with the engine running at full power about 2ft from my head. If you've ever been close to a 1200hp, 12 cylinder, twin turbocharged, 26 litre diesel engine going full chat you'll know all about the noise.............

Jeremy

 

[texaspyro]

If only it was scaled up about 4x I would make you an offer on it you would like.

Betcha he can improve it with funding...

 

[liveforphysics]

The Prony brake guy actually mentioned in the video's comments that he took the RPM under load for the actual calculations.

Oops! I missed that part in the video comments.

I like those DIY dynos.

If you've ever been close to a 1200hp, 12 cylinder, twin turbocharged, 26 litre diesel engine going full chat you'll know all about the noise.............

How about rooms with 16x 60L quad turbo 3,100bhp V16's at full tilt? That's perhaps the only thing I miss about MS...

 

[jonescg]

^^

And we think the internet is an environmentally friendly way of doing business :lol:

 

[Doctorbass]

Jeremy, any new developpment about that dyno?

On my side i found a great soltware that work with the microphone input with a coil and magnet.. very simple and the software is freeware and the source code is also shared:

http://sites.google.com/site/simpledyno/the-dyno

Doc

 

[AussieJester]

How about rooms with 16x 60L quad turbo 3,100bhp V16's at full tilt? That's perhaps the only thing I miss about MS...

Curious what these are used for Luke? Running gensets?

As usual Mr Harris excellent work 'ol boy if i had half your knowledge i would
be dangerous hehee...

KiM

 

[Arlo1]

Im marking this thread so I can come back later and make a plan how to upgread my dyno for scooters and ebikes!

 

[Doctorbass]

I plan on using both mode on my dyno: Inertia.. for lower power and eddy brake for higher power.

I found that the eddy brake part from exercisers are the best option!!! cheap.. availlable on ebay for around 100$ and.. .they include the flywheel and the pulley for a belt!!

The good new is that i found in Quebec a really big shop where they keep all kind of exercisers and they refurb them and have ALOT of used parts... including eddy brakes!!!

ex:

Doc

 

[Arlo1]

I got mine working a bit but the readings are way off I am not sure if the software is set up right [youtube]KYS1MXFFVTA[/youtube]

 

[Doctorbass]

nice!

ON my side, My dyno roller are still nt perfectly weight balanced and at 100kmg, the 100 pounds dyno material vibrate so much than it move by itself on the ground!

Now at 160kmh it's unsustainable.. so i need to correct this weight balance on one of the roller.

My E-trike have so much force than the 20" tire just slip on the rollers... I wonder if it is better to apply more weight or tension to the wheel against the rollers... or just to deflate a bit the tire to make them have more surface on the roller?...

It look like the friction added will not help measuring the real force...

Doc

 

[Arlo1]

nice!

ON my side, My dyno roller are still nt perfectly weight balanced and at 100kmg, the 100 pounds dyno material vibrate so much than it move by itself on the ground!

Now at 160kmh it's unsustainable.. so i need to correct this weight balance on one of the roller.

My E-trike have so much force than the 20" tire just slip on the rollers... I wonder if it is better to apply more weight or tension to the wheel against the rollers... or just to deflate a bit the tire to make them have more surface on the roller?...

It look like the friction added will not help measuring the real force...

Doc

You are suposed to tie the bike down tight and have the tire at max recomended pressure. You can have the rollers knurled it will help!

 

[Tiverion]

Jeremy, any new developpment about that dyno?

On my side i found a great soltware that work with the microphone input with a coil and magnet.. very simple and the software is freeware and the source code is also shared:

http://sites.google.com/site/simpledyno/the-dyno

Doc

Doc,

I really don't think that guy knows what he is talking about. The first sentence on the page describes his idea of a dyno.

"Building your dyno is simply a matter of making some rollers that your car can run on and adding some way of measuring how fast the rollers are turning."

No load? I don't think so.

--
Bill

 

[Jeremy Harris]

Jeremy, any new developpment about that dyno?

On my side i found a great soltware that work with the microphone input with a coil and magnet.. very simple and the software is freeware and the source code is also shared:

http://sites.google.com/site/simpledyno/the-dyno

Doc

Doc,

I really don't think that guy knows what he is talking about. The first sentence on the page describes his idea of a dyno.

"Building your dyno is simply a matter of making some rollers that your car can run on and adding some way of measuring how fast the rollers are turning."

No load? I don't think so.

--
Bill

You don't need a brake/load for an inertial dyno, which is what the plain roller dynos are. They work by measuring the rate of change of roller rpm with time and rely on knowing the rotational inertia in the rollers. With just a series of instantaneous roller rpm measurements you can calculate the power that the motor has delivered to the roller. The system works fairly well and tends to be very repeatable, as nothing gets hot to skew readings. The downside is that you can't run at a continuous rpm as the system relies on the rollers accelerating all the time.

My dyno is on the back burner while I deal with all the stuff surrounding the new house build, but will get resurrected once that's complete (especially as I'm designing a purpose-built EV workshop as part of the new house).

Jeremy

 

[Doctorbass]

(especially as I'm designing a purpose-built EV workshop as part of the new house).

Jeremy

That's excellent new Jeremy!

We hope you enjoy your new house :wink:

Doc

 

[Tiverion]

Jeremy

I'd believe it if the rollers were 30mm steel bars but "I used some plastic pipe with plastic end caps for mine, some 5 mm bolts for the axles and some bearings to help the rollers turn smoothly. The whole lot is held together in a wooden frame." I'm afraid I do not.

If anything, he is measuring the mechanical time constant of the motor which may be relevant given the very high power to weight ratio of the vehicle.

--
Bill

 

[Jeremy Harris]

Jeremy

I'd believe it if the rollers were 30mm steel bars but "I used some plastic pipe with plastic end caps for mine, some 5 mm bolts for the axles and some bearings to help the rollers turn smoothly. The whole lot is held together in a wooden frame." I'm afraid I do not.

If anything, he is measuring the mechanical time constant of the motor which may be relevant given the very high power to weight ratio of the vehicle.

--
Bill

There's enough rotational inertia in that set up for what it's used for, a model car. Heavier rollers would provide a better low rpm power point, but as these things really travel at pretty high speeds you don't need a lot of roller inertia to get power readings over the usable rpm range of the motors they are fitted with. There will be some impact from the ratio of model car component rotational inertia to the roller inertia, but I suspect the thing is still perfectly adequate for the designed purpose, comparative testing of different set-ups on a model.

For more powerful motors/bikes a heavier or bigger diameter roller is better, but that link is about a popular DIY dyno set up for model cars, one that seems to have proven to work OK for that purpose as far as I can tell.

Jeremy

 

[Doctorbass]

i'm using twin roller of near 7 inch diameter and weight each 30 pounds. most of the mass is on the large diameter.

This is not enough to get a ramp that last 10 sec( like it is recommanded) with 5kW power. but it work anyway... but if i want to put 20kW.. Houston.. we could have a problem :lol:

I planned on using the eddy flywheel i shown above. The exercisers mecanic and flywheel and eddy brake are perfect for our application. I have acces to a surplus part for that.

Problem is that i still did not found a good way to balance my rollers... at 100kmh+ one of those vibrate ALOT !! and i dopnt want to damage the pilow block mounted bearing...

Doc

 

[Tiverion]

...snip...

Problem is that i still did not found a good way to balance my rollers... at 100kmh+ one of those vibrate ALOT !! and i dopnt want to damage the pilow block mounted bearing...

Doc

Any heavy plant reconditioners in your area? They would have facilities for large crankshafts, flywheels and the like. Should be able to balance a couple of rollers.

--
Bill

 

[Arlo1]

I did some more testing tonight with no luck. So about my dyno, I just upgraded to the simple dyno software I used a VR sensor and fed the signal into the mic port on my laptop.
I can not for the life of me get it to work smoothly. I get to many spikes. I tried a 37 tooth wheel a 12 tooth wheel 1 bolt head so one spike/rev and 2 bolt heads (2 spikes/rev and it always gets some nasty spikes it seams to be in the laptop or the software from simple dyno. I tested with my oscilloscope and it looks smooth with it.... Here is a video

PS doc I used one of my pillow block bearings in one hand and a motorcycle wheel static balancing stand to balance my rollers today and man what a difference!
[youtube]2lhsCR2XEnM[/youtube]

 

[Arlo1]

Shit..... After reading the software updates I realized I was trying to dyno with the signal logger hack file...... I now downloaded the proper file and I will try it later!

 

[Doctorbass]

Shit..... After reading the software updates I realized I was trying to dyno with the signal logger hack file...... I now downloaded the proper file and I will try it later!

yeah.. give us some updates of your interesting test :wink:

Doc

 

[Arlo1]

It works.... I am not to sure about how light my rollers are... I meen I have all the proper weights but they spin to fast for the e-bike.... I think I will get a better reading if I had more weight... It seems 4.8hp was a pretty consistant reading for my bmx But at the peak hp of 4.8 at ~450rpm of the wheel/motor it says its only 12nm torque.... I think the simple dyno calculates torque based on the roller rpm and not engine rpm which is wrong... Remeber torque=hpx5252/rpm So 4.8x5252/450=56ft/lbs Thats not the peak torque but the number the torque should be at the peak hp and 10nm=7.2ft/lbs so...... Anyways here is two videos and yes I almost have 5 times the HP of a stock 50cc scooter..... [youtube]epGmoqLwZHE[/youtube]

[youtube]USsyKhrvsvM[/youtube]