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Best Way To Design Reverse Torque/Braking System

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Helixx

Computer
May 19, 2009
2
Hello,

I'm trying to design a system that can apply varying amounts of torque to a rotating shaft for variable amounts of time.

This torque may be applied in the direction of rotation or in the opposite direction of rotation.

So my setup would have an engine attached to a transmission which is then attached to a rotating shaft all mounted in a fixed position in the "lab". This engine has its own independent acceleration and braking mechanism as well. Braking is accomplished by restricting the shaft rotation. Let's call this "System A".

At the end of the shaft is a hub to which I can connect my "reverse torque" system to. Let's call this "System B".

So "System A" will be run independently accelerating and braking through a separate control mechanism/user. Then at various times, essentially random times, I want "System B" to apply a variable torque value to this hub in either the same direction of rotation or opposite direction of rotation for a specific duration of time. This time duration may have a maximum of about 10-15 seconds or so but most often less.

System B needs to be quite responsive and must be able to provide say about 80% (still to be evaluated) of the engine torque for system runs of about 10-15 mins before "recharging" etc...if required.

I've been looking into various technologies to use to provide the "reverse torque" such as an electric motor, electro-mechanical, electro-hydraulic, hydraulic etc... but I'm not sure which would be best in terms of cost, size, maintenance etc...as I don't have much experience/knowledge in those areas.

On average engines in System A will have a range up to about 300HP but I would like the system to accomodate higher power engines as well, say to about 600HP. I can attach 2 "reverse torque" devices to the shaft acting synchronously in order to reduce the power/torque requirements for an individual device if need be.

So I'm not sure if an electric motor of sufficient power is available to provide enough "reverse torque" and be able to switch direction of rotation relatively easily. Any thoughts on this?

From my basic research perhaps an electro-hydraulic or hydraulic system using hydraulic motors & pumps would have enough power. Ideally I would like System B to be as small as possible with enough power to do the job and easily attachable to the hub while hopefully not costing an enormous amount.

I think it would be preferable to use an electric motor as I'm assuming it would be simpler to implement/setup and have lower maintenance/safety requirements etc...

I really would appreciate some help in getting this design started.

Thanks.
 
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Reverse torque = brake. Forward torque = motoring the engine = not a good thing. Probably best to red flag this thread for deletion and start over in a mechanical forum.
 
The solution would depend a lot on whether the rotation is always in the same direction. Yes, I understand that the torque can be in reverse but is the rotation always forward.

Assuming that it is, the reverse torque would probably be best applied with a standard induction motor using DC injection to vary the braking torque. This same motor could, with the addition of a VFD, provide positive torque which, as I see it, would be torque trying to overdrive the test engine.

It is certainly true that hydraulics could be used to do the same thing but the motor system is probably easier to control, certainly easier to collect data from, and if the parts are chosen wisely, the braking energy could even be saved and regenerated back into the AC supply for reuse elsewhere.

If I'm on the right track here, let us know and we can flesh out the details somewhat more for you.
 
Sounds like an engine test stand. They make those things you know.


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@davidbeach:
I actually had a posting in the Mechanical Engineering:Other forum and someone suggested that I post here as well.

@DickDV
Yes you are on the right track!

In terms of direction System A will run in the "forward" direction from a standstill up to full torque 99% of the time for long durations. In this case System A may apply full/extreme power right from the start.

It will run in the "reverse" direction from a standstill 1% of the time but only at a very small speed and small torque for a very short duration. It may even be where we decide not to apply any counter torque using System B if this proves too difficult.

@jraef
Yes this is quite similar to other dyno's, test systems etc...however we have certain requirements that these other systems cannot meet or else they come with other options/features which we do not necessarily need but add significantly to the price.

So we are interested to see if we can develop our own cost effective version based on our particular requirements.

@starkopete
We estimate the upper speed range to ideally be around 2500-3000 rpm. A little more would be nice say to 3500 or 4000 rpm.
 
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