Time for an Open Bike-Dyno

[TylerDurden]

Posting here rather than in testing, because it ain't built yet.

In fact, it ain't even planned yet. But it should be. There are enough questions and pissing-contests here to justify a discussion on how to design a bike-dyno that anyone can build.

If we can come up with a design that allows heavy loading, we can drop all the hoo-haw about finding a suitable hill and all the other similar crud.

Besides, wouldn't it be cool to have one?



SO:

We might want a...

100A alternator
Stand to prop up the driven wheel
Ammeter
Battery load tester

and...

 

[Miles]

Yes, this is a great idea.

I was considering getting a PowerTap, but they're rather expensive..

 

[TylerDurden]

We only need a few of these things, and we can ship em around to whoever needs to test... it ain't like ya gotta have one every day.

:lol:


Oh yeah, I still have a treadmill I can cannabalize.

 

[knightmb]

Well it doesn't have to be perfect, just consistent for comparison. There was an old treadmill down at the good will for only $10 I thought about buying. It still worked, oddly enough, but I was thinking more along the lines of a good way to tie up an e-bike and have work the thread motor as a dyno to test motors, batteries, etc.

 

[Matt Gruber]

knight
sounds good! will prove to be way too complicated for some reason

 

[TylerDurden]

knight
sounds good! will prove to be way too complicated for some reason

"Cmon Matt... if you can't do it with a 2.99 DVM, it can't be done!

:lol:

 

[TylerDurden]

Searching around on "bike generator"...

http://www.kbt-dc-supplies.com/bike.php

 

[Matt Gruber]

not so hard!
i'd just run the bike
hook the gen to my 1-53a halogen tester
add load untl it slows down
measure v, amps, and calculate watts

 

[TylerDurden]

Sound good MG...

Here's a good rigging concept:

http://www.freerepublic.com/forum/a3ab928b76932.htm

"I had to make a new axle which is locked to the roller and move the bearings to machined aluminum plates outboard of the steel frame. The plates are made to a standard NEMA 42 size and provide the mounting surface for a permanent magnet DC motor that is driven as a generator through a flexible coupling. The other end of the axle exits from the bearing through an identical plate and is available for PTO use. You can see a black sprocket on that end of the axle in the pictures. I also had to weld in a brace to stiffen up the frame to allow carrying the extra weight of the generator. I'm pleased with the result. Even under heavy load it runs cool and relatively friction free. The part of the frame that clamps to the rear axle of the bike pivots with respect to the ground so that the rider's entire weight forces the tire into contact with the roller reducing slippage to a minimum. The black object under the front wheel is a contoured plastic block that levels the bike to avoid the feeling of riding downhill."

 

[fechter]

I built one a long time ago for Mr. Electric. It looks much like the one in the first picture, with large rollers for the wheel to rest on. There were a few problems. It was difficult to keep enough down force on the rear wheel to prevent slippage. Tire spinning melted sort of a track in one of the rollers. I figured out that it needed to use a single roller, rather than two, and I had to mount the roller to the rear of the bike axle so that increasing torque resulted in increased down force. Sort of like an EV Warrior friction drive.

The other problem was what to do with all those watts. We got a bank of huge load resistors from a surplus place and made a switching arrangement to change the resistance. I used an old Vego brushed motor as a generator. A permanent magnet treadmill motor should work well, but at a higher voltage.

With my scooter on there, those resistors got really hot.

One other problem was the load increased with speed for a given resistance. Not really bad, but it would be better if the load could be made constant. Using something like a DrainBrain on the load side would be cool. I just had a pair of analog meters, so measuring Watt-hours was difficult. If the efficiency of the generator side is known, then the efficiency of the bike motor could be determined at many different load and throttle condions.

I'm not sure what ever happened to it. It might be sitting in his garage.

 

[TylerDurden]

Thinking a bit more...

Standardizing the system will require a calibration routine or a specific motor for all the builds.

We might consider a cheap PM from a known vendor that anyone can use.

Suggestions?

 

[roller]

I'd recommend all those burned up Currie motors out there. knock the blown controller off the back and use BLDC motor. couple of diodes later and you've got DC. good for about 2HP anyway.

otherwise, the brush vego or rad2go scooter motors tend to be plentiful.

you can avoid the load resistors and diodes by just shorting the windings. makes for a pretty heavy load, though. but it's easy to get a system going with.

------------

the motor dyno I use is a series wound ADC, which we made into a sepex motor. we power the sep ex field with a regular variable power supply to control the load. then wire the armature to load resistors (or, now we actually short the armature and dissipate all the heat in the motor structure -- needed the load resistors for a generator test).

I guess this makes reading electrical power out a bit difficult. we read mechanical torque and speed out (optical tach, bearing mounted motor with lever arm on strain guage).

 

[Lowell]

There's a couple Dyno Dynamics setups local to me...I'm planning to run my bike on one.

http://www.dyno.com.au/dyno/controller

 

[silentflight]

One of the moderators on the Tidal Force forum has started a similar thread regrding testing of real world watts put into the road with a communal dynamometer.

I would very much like to see electrical watts in matched to mechanical watts out for Bionx bikes in particular.

Would it work to buy a PowerTap hub and wheel on ebay and then create a roller and chain to drive it from the hub motor wheel under test?

Perhaps it is not necessary to have the PowerTap laced into a full wheel so it could be shipped around in a relatively small and lightweight box. I suppose it needs some source of load and resistance to spinning in order to measure the torque placed on it though.