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Old 11-28-2005, 01:42 PM   #1
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Default RC Dyno

Hi everyone,

I'm new here and new into RC. I'm interested in finding more about the technical side of of the sport and am considering building myself a small dyno (dynamometer) to collect some simple data (speed, acceleration, voltages, temperatures etc. Does anyone have any experience of this field or have any ideas as to the route this project should take.

In my Job, I have access to high speed temperature and voltage measurement equipment. Really, I just need a simple and inexpensive method of getting the car running. I need it to be on a dyno so that I can collect the data in close proximity to the equipment.So far, I've decided to make a simple roller design (with an optical encoder), but I'm unsure if there are any issues i'm missing. So please, pass any advice you have my way and I'll have a think.

With any luck, this can turn out to be a useful project for us all. I hope to document the whole process online as I go along, so plans will be freely available. You're input would be very much appreciated.

Best regards,

Colin Brown
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Old 11-28-2005, 01:49 PM   #2
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Chassis dyno's were popular in the mid 90"s.. they have since been obsolete.. they were not as accurate as people thought.. currently we only use dynos for the motors them selfs.. the most popular are CE turbo dyno, Fantom facts dyno, and a robi..it hooks to a lap top and give rpm's. power numbers ect..
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Old 11-28-2005, 02:36 PM   #3
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Does anyone know of anyone that has attempted to build something like a chassis or motor dyno?
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Old 11-28-2005, 02:40 PM   #4
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I'm pretty sure Parma PSE had a chassis dyno a long time ago.

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-Rich
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Old 11-28-2005, 02:43 PM   #5
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Parma and thor had chassis dyno's.. i think parma bought the right to the thor after they went out.. They were not very accurate as stated above.. thats why guys stopped using them and stick to ust a motor dyno.. you can occasionally find them chassis ones used for around 100 bucks..
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Old 11-28-2005, 02:43 PM   #6
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Brown,

You may want to contact Isaac over on the Axxis thread I think he is currently working on a dyno himself.
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Old 11-28-2005, 02:44 PM   #7
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It is actually very easy to build a dyno.

If you are using rollers, figure the mass and moment of inertia of the rollers. Based on that, as they accelerate (ds/dt) you want to record the data at no less than 100 samples per second. If you know your physics or mechanical design it is very easy to achieve and build. Once you collect the acceleration of the rollers (mass) you can use general physics to calculate torque, horsepower, acceleration, current draw, and voltage...You want to measure most factors against time..

I have designed chassis dynos but as burbs said, they are not used in R/C.

If you want to proceed with the design I will be more than glad to guide you in theright direction...but I am not sure you will gain much from it.

We measure the performance of R/C cars on the track....YOu have to remember that with a static dyno there is no drag and drag plays a huge role in electriccars. The data that you wil get from thedyno wil only be empirical, not real track data...

Isaac K
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Old 11-28-2005, 02:54 PM   #8
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Any pictures that you might have would be great.
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Old 11-28-2005, 03:10 PM   #9
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here is a pic of the fantom and the competition electronics..

robotronics makes one
Cs makes one
integy make a cheap dyno.. not as good as the others.
there is prolly 10 or so companies that make some sort of one..
Attached Thumbnails
RC Dyno-dyno.jpg   RC Dyno-tdyno%2520lrg.gif  
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Old 11-28-2005, 03:15 PM   #10
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Thanks everyone, this forum is so helpful. Isaac, do you have any photos of the dyno you designed? I am a mechanical engineer, so I know my way around mechanics.
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Old 11-28-2005, 03:20 PM   #11
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Quote:
Any pictures that you might have would be great.
Are you talking about commercialy availabledynos or to design your own dyno?

Look into any mechanical engineering and instrumentation design book.

Are you talking about a block diagram of thedyno or what? A picture will not show much...

If you want to build a good dyno, why don't you use a load cell like a magnetic particle load, that way you can measure torque directly at the load...after all, the most important data a dyno gives you is torque. Once yo know the torque and the Kv of any motor you can reverse engineer and get all the performance data... that will also help you tune the motors...
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Old 11-28-2005, 06:52 PM   #12
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Quote:
Thanks everyone, this forum is so helpful. Isaac, do you have any photos of the dyno you designed? I am a mechanical engineer, so I know my way around mechanics.
I will be glad to pass along al lthe formulas needed to figure out torque from a known rotational mass. YOu still have to design all the electronics to perform the tests.
It is very simple in principle, however, it gets a bit complicated once you start the design and implementation process. Everything has to be in balance (the closed loop circuitry)

There is a huge misconception that measuring current and rpms under no load condition is a dyno...That is NOT a dyno...Several companies offer products under the DYNO name but they are not dynos...they are simple measuring instruments (and most persons can do that with a DVM and a simple tach)
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Old 11-29-2005, 03:39 AM   #13
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Yeah, that would be great, thanks. I'm now considering making a simple motor dyno. I will gear the motor down and use it to turn a flywheel. Using an optical encoder and equipment that I have available at work, I should be able to easily calculate the torque of my motor.
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Old 11-29-2005, 03:56 AM   #14
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It's not a chassi dyno but at least it's something

http://uk.geocities.com/dave_pickett...ew_page_17.htm
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