Hi @johnohorse,

Did you ever find out? Interested myself.

Cheers

Posted by: @johnohorse

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hi does anyone here know what sort/brand of hydraulic pump a dyna pack uses cheers

 

Hi there, before I go further into development of this system I am interested on more information on Hydraulic controlled dynos. The Dynapak mentioned above appears to use a fairly large hydraulic digger pump and it looks like it measures pressure, instead of using a load cell to perform its calculations. 

The basic "standard your dyno" controller, which I have cannot control 2 x Servo/Stepper, meaning for a hydraulic hub dyno I would be limited to use PWM and control pressure though a 2 or 3 hydraulic way valve. The more I look the more I don't see this being a common control method. Is this because PWM or a solenoid simply will not work and better regulation of flow from a servo/stepper is needed? Can the PWM be trended to simulate better flow characteristics within the linearization tab?

The pumps I have in mind are 4535VQ versions. These actually have two pumps within one pump unit. They would need a solenoid that is PWM suitable on each pump for one axle which I assume can be paralleled from one output. 

If anyone could share some information on this, it would be appreciated. As an FYI, I'm familiar with the yourdyno software having built an eddy current version a few years ago. The hydraulic pump idea comes about since I know it's been commercialized though Dynapak in NZ and there is a cost saving to this set up in terms of power requirements to the unit, but also the pumps appear to be cheaper than the similar sized eddy current units.  

Any help appreciated. Specifically, around PWM control of a hydraulic valve. 

Thanks 

Tom 

You can use PWM to control a servo, which then controls the valve. You need a powerful servo, but there are very powerful ones out there now. Something like this might work: https://www.aliexpress.com/item/1005006832626630.html

Thanks for the reply. I had not realized you could get RC servos in that sort of size. This is probably the best solution. 

For packaging a solenoid valve would fit nicer. Similar to this user set up: New Brake Control for Hydraulic Dyno – Questions, answers and shared experiences – YourDyno.com Forum

What are your thoughts on the pros and cons for both applications? The solenoid option will probably not smooth out as nicely as a proportional valve? 

For reference, this is for a hub dyno with the intention for most use between 200-600 WHP 

Thanks 

Tom 

@tom-hulbert If the solenoid could open and close very fast, then at some point it will work as a regulated load, but I am pretty sure a solenoid valve will pulsate a lot and control will not be as good. A proportional valve is the way to go. Even then you are in much more unknown territory than if you go for Eddy brakes. Although Dynapak successfully uses hydraulics, almost all other hub dynos are using Eddy brakes.