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  #16 (permalink)  
Old 06-03-2008, 07:19 PM
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homemade dyno

i am researching to build a dyno for bikes
some math here
i havnt tried it yet but a place to start

http://wotid.com/dyno/content/view/16/35/

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  #17 (permalink)  
Old 06-03-2008, 08:00 PM
How fast is fast enough?
 
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how about instead of using a fan or a "freaken huge wheel" you use a large parachute hooked to a scale then to a spool on the engine. You could change the size of the chute to get more drag (essentailly what the fan is) as well as the speed of the engine, using different spool sizes, chute sizes, and speeds you could probably create a "dyno" that is even more accurate than the ones designed around water brakes. Also if something fails guess what it doesn't crash anywhere, it just falls to the ground. Don't use cable though, use nylon rope, its not quite as strong for a given thickness but it won't carry much inertia if it snaps. A broken cable can kill a person- one did kill my great grandfather.
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Old 06-03-2008, 08:30 PM
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Danger Will Robinson

I think the other post should've read
DANGEROUS MINDS THINK ALIKE
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Old 06-03-2008, 08:55 PM
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dyno

The engine could be hooked up to a large electric motor (or two) and an electrical guy can make it (them) generate power to put back in the grid or to charge a whole bunch of batteries. An electric motor is similair to a generator. Lots of money in making electricity. The reason I say motors is that there are a lot of 50 hp motors out there but we are talking about dynoing a lot more horses than that.
Clint
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Old 06-04-2008, 06:56 AM
How fast is fast enough?
 
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A large elctric motor would probably be the best idea. really, with the right equipment it could be perfect.... now you just have to find the right equipment.
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Old 07-25-2011, 03:03 PM
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I realize this an old tread, but are there any new ideas 3 years later?

here's a thread on HAMB: http://www.jalopyjournal.com/forum/s...d.php?t=187126


I was thinking maybe a big torque wrench(I've used ones with 1000+ ft.lbs capacity) on a torque converter? I think it'd work until the tq converter locked up, but if someone used one with a higher stall than the engine's redline(or higher than you'd be testing it at) would it work?

I've only messed with manual trannys, so my knowledge on converters is limited, but as far as I can see it should work? the tq wrench would have to be the lever type, not the click type

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Old 07-27-2011, 02:06 AM
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Any ideas? Techinspector?
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Old 07-27-2011, 04:35 AM
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If the dyno only needs to handle relatively small loads, I have seen it done. My son built an engine dyno to use when tuning a college Formula SAE race car, and I think they used an electrical load. The car uses a 600 cc Honda motorcycle engine, and when I saw them run it on a chassis dyno during competition I think it ran about 80 horsepower (intake restricted) to the ground. I'm not sure how much horsepower their home-built dyno could take.

Bruce
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Old 07-30-2011, 02:56 PM
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Water brake

Back in Hot rod mag. in 50 or 60 there were plans for a home made water brake made form welded up metal.
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Old 07-30-2011, 06:15 PM
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I am in the process of building my own home built chassis dyno.

To build an engine (or chassis) dyno you need three things.

1/ A power absorber, usually a water brake or an eddy current retarder.
Easiest is to make your own water brake, or buy an eddy current brake off a bus or truck (fairly common on some Scania trucks)

2/ A system for measuring rpm and torque at the dyno load, and some software to display or print out the results.
This is the easiest part of the lot, because there are now quite a few commercial software packages available to do this at very reasonable prices.

3/ The most difficult part to put together is the dyno CONTROL SYSTEM.
This needs to adjust the dyno load up or down to hold the engine at the desired speed.
In other words it must read engine speed, compare it to what it should be, and adjust the dyno load to hold that desired speed.
The target speed can be either fixed, or a moving target speed to do sweep testing and plot power and torque curves.
Although fixed speed operation is all you really need for practical engine tuning and measuring power. Fixed speed control is far easier to get going.

A home built dyno can be just as accurate, or even more accurate than a high dollar commercial dyno.
It only needs to measure two things.
RPM of the rollers (or engine), and torque reaction at the power absorber.

Electronic speed measurement can very easily be done to better than 1rpm accuracy by electronic means.
Torque accuracy can easily be checked and calibrated with a lever and an accurate known weight to as close an accuracy as you are prepared to go to the trouble of achieving.
Software just multiplies one by the other and divides by 5,252 a straight software mathematical operation with zero error.

So it is not too difficult to build a very accurate home dyno, just a lot of work and some money.

I bought a 500Hp roller chassis dyno that had been through a fire for $1,000.
The in ground part of it was perfect, but everything above ground was a total ruin.
I had to build my own closed loop speed control system, and write some software to monitor the dyno and spit out some numbers for rpm, torque, and Hp on digital readouts.
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Old 07-30-2011, 08:23 PM
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How about building a dyno trailer ?

Hook it up to your tow bar and set the rpm/speed you wish to measure the power at.
Floor the throttle, and measure the pull on the trailer draw bar.
It is then simple to work out horsepower.
For instance if your trailer wheels are 12 inch radius, Lbs pull on the trailer = Ft/Lb directly.
Multiply that by trailer wheel rpm, divide by 5,252 = Hp

This isn't just a crazy idea, these towed dyno trailers are commercially built.
http://www.westest.ca/towdyno.html
http://www.land-and-sea.com/towing-d...ynamometer.htm
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  #27 (permalink)  
Old 07-30-2011, 09:36 PM
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This looks like a cool site. Might want to look around and learn a little somethin'. I'm going to

http://www.land-and-sea.com/dyno/dyno.htm
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Old 01-05-2013, 05:19 AM
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in a magazine i read a contributor called charlie broomfield has built his own engine dyno using 2 electric retarders from a coach he said
" im building a frame with a gimbal to house 2 of them. the outside housings will be able to rotate and ill measure the force on them with some electric scales. from that i can work out the engines torque and hence the horsepower (BHP=torquexrpm/5252)"
i dont know much about it but he may be willing to give some info you can contact him through Practical Performance Car (PPC) magazine, a monthly publication aimed at real car enthusiasts | Charlie Broomfield
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  #29 (permalink)  
Old 01-05-2013, 02:44 PM
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Those electric retarders are often used on large trucks and buses, and you can buy them from a truck graveyard if you hunt around. Many Scania trucks have them.
They even sometimes turn up at scrap metal dealers !!

They fit into the tailshaft between gearbox and diff, and if you are going down a very long steep hill in your fully loaded truck, you can use it to slow the vehicle without touching the normal brakes.



The clever thing about it, is that there are no rubbing parts or wear as you have with normal vehicle friction brakes. The truckies love them ...
The exact same type of eddy current retarder is what most commercial chassis dynos use. Even the smallest ones are rated for 400Hp, larger up to around 800 Hp or more.



Google "Telma Retarder" for more info.....

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