Free - hi-tech 5-75 hp dyno

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Re: Free - hi-tech 5-75 hp dyno

Post by Tuner »

Eddy current brake on the inertia load flywheel.

https://www.physlink.com/education/askexperts/ae527.cfm
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Re: Free - hi-tech 5-75 hp dyno

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williamsmotowerx wrote: Wed Dec 04, 2019 3:26 pm Tried sending you an email. This is perfect for my size engines.
PM me
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Re: Free - hi-tech 5-75 hp dyno

Post by David Vizard »

Tuner wrote: Thu Dec 05, 2019 9:27 am Eddy current brake on the inertia load flywheel.

https://www.physlink.com/education/askexperts/ae527.cfm
Tuner - a good guess but my dyno is actually simpler than that.
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Re: Free - hi-tech 5-75 hp dyno

Post by mekilljoydammit »

Been a bit now... any more hints or answers on how that part of it works?
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Re: Free - hi-tech 5-75 hp dyno

Post by RCJ »

Have been wondering what happened on this myself. From the pixs the motor has a external coil and spark box.If you measure the voltage to the plug wouldn't that give a sense of the cylinder pressure.
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Re: Free - hi-tech 5-75 hp dyno

Post by Isaac91n »

I have a theory on this. I don't have the correct words to describe what I'm picturing in my head as I'm not a learned physics dude, just a diesel mechanic. Anyway with the gyroscope effect, I've noticed when I'm holding an angle grinder and try to turn it in my wrist in a certain direction (while it's turned on) it resists the motion. Is this the effect that is used to absorb the engine input? I'm curious as David stated it doesn't require any heat disapation which any type of brake would require. He also said it can give in cylinder pressure readings, again any type of fluid brake would tend to dampen any type of harmonic vibration that would in my view give that sort of ability to measure it. I've just PM'd David now, I really hope he has a chance to enlighten us all.

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Re: Free - hi-tech 5-75 hp dyno

Post by Isaac91n »

This thing has consumed me all evening, grief. If this gyroscopic procession thing is correct, I'm struggling with understanding the calculations from some Google searches, so I have no idea of the speeds and diameter and weight the flyweel needs to be, or the speed of the gyroscopic procession. but if I were to build one I'd do it like this:
I reckon I'd take a right angle drive with a 1 to 1 ratio and attach a flywheel to the output shaf. I would suspend the right angle drive so it was free to rotate full 360 degrees along the axis of the input shaft. I would attach a clogged drive belt to the 90 degree drive housing and have it attached to a hydraulic motor. The motor would need to have minimal leakage, so it can be hydraulically locked when in pure inertia mode. There would of course be a hydraulic pump driven off the input shaft and the fluid would go through some sort of valve to controll the speed of the hydraulic motor. I'm not sure if the 90 degree drive housing would need to rotate opposite the engine rotation or not. If it could go in the direction of engine rotation then simply a hydraulic pump driven off the 90 degree drives housing would be enough, and just restricting the pump rotation speed via a valve would be all that's required. My guess that the speed the that the gyroscopic progression would need to happen would only be 20 or 30 rpm, and the weight of the flywheel would probably influence that.

David vizard is an absolute genius for coming up with this.
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Re: Free - hi-tech 5-75 hp dyno

Post by RCJ »

I've built one myself. If you search performance trends small engine dyno you can see how they are built. They are measuring the time it takes to accelerate the mass. Water brake dynos have an arm 90 degrees with a load cell on it. I would like to build one for a sbc but finding a big enough flywheel is an issue.
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Re: Free - hi-tech 5-75 hp dyno

Post by Isaac91n »

He infers that this dyno has no brake absorber. He says to increase its capacity simply enlarging the flywheel would bring it up to 250hp. But if it has awater brake that is already maxed out at 75 hp, enlarging the flywheel will have nill effect to do steady state on a higher power engine. Also he says its sensitive enough to pick up individual power pulses. I don't know for sure but I would have thought that would not be possible with a water brake as it would kinda act like a harmonic dampener and smooth out the engine pulses transmitted to the weigh cell. I absolutely agree that your method works, but I think David has something a bit trickier than a water brake attached to a flywheel.
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Re: Free - hi-tech 5-75 hp dyno

Post by RCJ »

0pps double post
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Re: Free - hi-tech 5-75 hp dyno

Post by Dave Koehler »

Isaac91n wrote: Wed Aug 24, 2022 6:25 am He infers that this dyno has no brake absorber. He says to increase its capacity simply enlarging the flywheel would bring it up to 250hp. But if it has awater brake that is already maxed out at 75 hp, enlarging the flywheel will have nill effect to do steady state on a higher power engine. Also he says its sensitive enough to pick up individual power pulses. I don't know for sure but I would have thought that would not be possible with a water brake as it would kinda act like a harmonic dampener and smooth out the engine pulses transmitted to the weigh cell. I absolutely agree that your method works, but I think David has something a bit trickier than a water brake attached to a flywheel.
It's an inertia dyno. Just a big ole wheel. I call them mountain climbers. throw a brick on the pedal and see how far it can pull up the mountain."

http://www.performancetrends.com/CustomerDynos.htm

https://www.youtube.com/watch?v=PME1PvL_vkA

Punch in inertia dyno on YT. Bunch of stuff to look at that demonstrates the concept.
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Re: Free - hi-tech 5-75 hp dyno

Post by Isaac91n »

Dave Koehler wrote:
> [quote=Isaac91n post_id=923528 time=1661336755 user_id=35888]
> He infers that this dyno has no brake absorber. He says to increase its
> capacity simply enlarging the flywheel would bring it up to 250hp. But if
> it has awater brake that is already maxed out at 75 hp, enlarging the
> flywheel will have nill effect to do steady state on a higher power engine.
> Also he says its sensitive enough to pick up individual power pulses. I
> don't know for sure but I would have thought that would not be possible
> with a water brake as it would kinda act like a harmonic dampener and
> smooth out the engine pulses transmitted to the weigh cell. I absolutely
> agree that your method works, but I think David has something a bit
> trickier than a water brake attached to a flywheel.
> [/quote]
>
> It's an inertia dyno. Just a big ole wheel. I call them mountain climbers.
> throw a brick on the pedal and see how far it can pull up the
> mountain."
>
> http://www.performancetrends.com/CustomerDynos.htm
>
> https://www.youtube.com/watch?v=PME1PvL_vkA
>
> Punch in inertia dyno on YT. Bunch of stuff to look at that demonstrates
> the concept.


Morning all you magnificent gentleman
I totally understand how a simple inertia dyno works and what one is. It's about as simple as it gets. But what I am trying to say is that there is a way to build one that has no brake (eddy currant, water brake etc) and is able to hold an engine at a constant rpm, or have the ability to change the acceleration of a dyno pull to what ever you want it to be.

Look up gyroscopic torque and gyroscopic procession. If my understanding is correct, by turning the inertia flywheel into a gyroscope you can hold the engine back without any type of typical brake. The design begins with putting the inertia flywheel at 90 degrees to the input shat of the dyno.
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