Question for People who know about Dynos

[katou]

There has been a whole lot of guessing, conjecture and theory about which internal hubs have what strengths, but precious little data.

I was wondering, to objectively test these hubs, couldn't we just use a dyno?

I don't really know what a dyno can or can't do, so help me out here.

Couldn't we couple the motor to the hub with some sort of framework, then attach the output from the hub to the dyno?

Then, standardize the torque going into the hub, and test to destruction.

The info to come out the other end would be torque or power readings for each hub.

I know I'm missing a lot here, can anyone else fill in the blanks as to how this could be done?

Katou


ps. I can get a SA hub for $30, and I'd be happy to donate it for testing.

 

[Drunkskunk]

The idea of a Dyno has been tossed around here for as long as I have been a member.

Justin at Ebikes.ca uses one and posts the results in the simulator section of his website.

Building a dyno is easy. wrighting the software and calibrating it is that hard part.

The idea had been tossed around of us designing a dyno that could be built cheap and easy by anyone, so we all could use the same software and be able to compare results from one user to another with some hope of accuracy.

 

[Drunkskunk]

Essentualy you need a roller, and something to detect it's speed.
Thats easy. A cheap diskbrake front hub, with a cheap 160mm disk with lots of holes drilled in it. preferably from some online source so everyone can get the same thing easily.
Then use a $9 usb mouse from walmart for the electronics. use the laser emiter and detector shining through the holes of the disk brake rotor for your input, and the USB cable to conect to a computer.
(Realy just need an IR emitter and a detector, and a serial cable, but its cheaper to repurpose a mouse)

The frame only has to hold the roller and wheel, and have a hinged part to hold the wheel stable against it. It could be made of scrap wood, metal, plastic, stone, sticks, bone, glass, or used apple cores. they only thing that would matter is the geometery be the same for the wheel holder and the roller, with the pivot point the same distance for everyone.

The hard part is the software, something that can take the pulsed data from the USB source and translate that to a useable metric.

 

[John in CR]

Drunkskunk,

For detecting speed just use a bike speedometer...cheap and easy. Mount the magnet and input the roller size as the wheel size. If it won't accept that size, just scale it by a whole number to keep the conversion easy.

 

[Miles]

As torque is what we're interested in, why not just measure that directly, by measuring the reaction force?

 

[katou]

No no no.

I want to USE a Dyno, NOT build one.

There are dynos out there, lots of companies have one. I just want to see what would be involved in USING one.

That said, I do not know the protocols or setup for testing on a dyno. That's where I need help.

Katou

 

[Drunkskunk]

I don't know of any Dynos that would work for an ebike. Ones meant for cars, or even Motorbikes are calibrated with a margin of error greater than the total output of most ebikes. I've seen some high dollar ones for Olympic racers, but they cap out at like 5 horsepower, too low for an ebike

Other than Justin, I don't know of any Dynos build for Ebikes. Something would have to be built.

But you could play around like these goofs. No accuracy at all but good fun with beer. [youtube]v=5EExkzkZZ-A[/youtube]

As for the speedo idea, it wouldn't be as accurate since they sample once per passing of the magnate, were the beam would sample once per hole, 50 to 100 times per revolution depending on the disk. But your Speedo idea might be easier to reproduce for everyone.

 

[katou]

Why can't I use one designed for motorcycles or scooters?

They must exist, people do mods on scooters to improve them, and I'm sure that the more techy individuals doing so would dyno test their mods.

Who here has experience with dyno testing motorcycles?

Katou

 

[Doctorbass]

I bult my own dyno with the help of a friend.

2 roll of 8 inches weighting 30 pounds each.

it can be inertia or generator mode.

i'll finish that during the next months.

I want to measure and tune everything i would normally test on road.. but without the wind effect.

hee is the thread:

http://endless-sphere.com/forums/viewtopic.php?f=2&t=18858&p=275993&hilit=dyno#p275993

Doc

 

[John in CR]

Drunkskunk,
For greater precision of the bike speedo just add more magnets.

In place of a dyno could we get reasonably accurate using acceleration on the flat as well as up a known hill with a fixed weight and calculate the number?

John

 

[liveforphysics]

Did you guys not see this video I took at Justin's shop? He also has a wheel/tire e-bike dyno as well, but he said the rollers would eat the tire up after an hour or so, and he wanted to be able to be able to do endurance dyno testing as well as just measuring performance.

[youtube]epIz7P3viio[/youtube]

 

[katou]

This is really weird, but Luke, you sound EXACTLY how I thought you would. What are the odds? Thanks for the video Luke, I've never seen that one.

I'm all for cool engineering, but I want to find a way to get results, not build a dyno. I don't have anywhere near the talent or electrical background that Justin does, there's no way I could do something like that.

There must be a scooter size (ICE) dyno around. Am I going to have to actually make PHONE CALLS? Look at what I'm reduced to.

Ah well, back to looking. I'll start with scooter places, jump the pipe to mod places, and go from there.

Katou