Thread: Hydraulics a solution to The 3 Phase Problem?

I'll bet the cost of the a hydraulic motor costs way more than a single to 3 phase VFD.

how about this - http://www.ebay.com.au/itm/Hydraulic...item3a98475207 14kw, $300. There are heaps on ebay for about this price. I was thinking of second hand though.

How much would a VFD be to convert power for say an 8HP 3ph motor?

Originally Posted by harrygrey382

how about this - http://www.ebay.com.au/itm/Hydraulic...item3a98475207 14kw, $300. There are heaps on ebay for about this price. I was thinking of second hand though.
How much would a VFD be to convert power for say an 8HP 3ph motor?

OK it looks like my definition of a "well equipped woodshop" is not the same as yours. >5HP is an industrial workshop in my book.

Have you done a running cost analysis. Remember your truck has to run all the time you are in your workshop otherwise you're going have to start and stop it every time you want to use a machine.
I'd find that a right PITA.

Originally Posted by BobL

OK it looks like my definition of a "well equipped woodshop" is not the same as yours. >5HP is an industrial workshop in my book.

Have you done a running cost analysis. Remember your truck has to run all the time you are in your workshop otherwise you're going have to start and stop it every time you want to use a machine.
I'd find that a right PITA.

I only said 8HP because that seems about what most 24" thicknessers have, so 36" is going to go a fair bit more. Yeah 5HP is getting easier to convert. But I'd say I'm more in the dreaming stage at the moment. Although if I saw one for a really really good price, even if it needed a total rebuild I'd pick something up. I reckon I'd use them so little running the truck for however long it took to do a batch of boards would be ok. I guess I'm narrowing it down to the thicknessing/planing - starting it up for a single cross cut sure would be a PITA.

I haven't done a cost analysis but I don't think set up costs would be that high, considering I'll already have the pump on the motor. I'll have an hour meter on it and run it up to 1200rpm or so and load will be variable so shouldn't have any negative affects on the truck.

But like I said it's only a thought right now...

I suspect that there are some issues hidden there that you haven't factored in.

The 14KW unit that you linked has a max speed of 375RPM, an electric induction motor for a thicky, jointer sander etc has a speed of approx 1450 or 2850 RPM. It could be made up to equivalent by using a step up belt drive, at the expense of a commensurate drop in torque. In many of the woodwork applications in this power range, an induction motor would already be using a step up drive system.

The motor uses up to 60L/m at max speed/torque, I suspect that that will require a fairly significant sized hose if you need to run moderate distances.

The truck may have a hydraulic pump installed for a crane, but what flow rates can it handle and how much power does it need to provide the flow rate. Since it is only operating a group of rams, I suspect that it probably won't have the capacities that you need, or would need to run the motor at fairly high rather than idle speeds to move the volume of fluid required to operate the machinery. How big is the fluid reservoir for the truck, if you are having to pump 60L/min, you need to carry a lot of fluid. My neighbours 12t excavator has a 55l/min pump and a 12l/min auxilliary, it uses an 85HP turbo diesel engine running at 2500RPM for peak flow and has a 300L reservoir and 50mm plumbing for the high flow circuits that are typically 7m OA (total of pressure and return runs).

I think I would be talking to a fluid power engineer before committing money.

Yours is exactly the post I needed - some good hydraulic pointers. I'm a way off buying anything for it, apart from the crane stuff. You raise very good points about the whole set up. I'll check the specs of my powauto pump out. 60L/m is some high flow rate, I wasn't thinking of having a 300L tank either...

Thanks a lot for the down to earth reply

Maybe the cost of a 3 ph installation is expensive; but it's a one-off. Unless of course you're likely to move soon.

I've seen many instances in Tas. of clients wishing to have their homes rewired, and installing a whole plethora of new power hungry appliances at the same time. Commercial, even industrial ovens, reverse air con systems & the like.

What they haven't factored in is that in many instances this increased peak demand requires new supply mains to the switchboard. It's expensive, yes, but when amortised over the expected life of the installation it becomes if not reasonable then at least less unreasonable.

If the client replaced, (as some of them actually are required to) the old 10mm sq. twin mains for 3 phase in greater cross sectional area, then the whole installation is made future-safe should new appliances with high peak demand be later required.

Consider it an asset. It's going to add utility and value to your home. As you've already stated, it's something many of us would wish to have, meaning it will add value to your home in a similar fashion to a kitchen or bathroom upgrade.

Plus you will have access to the very machine many of us would wish to have. As many (most) of us don't have 3ph. juice available, the demand for second hand machines is also proportionally less, and they can often be had for a song. There's serious quality 3 ph. gear out there. Single ph. gear sells for more, and often needs to be purchased new. I don't need to tell you I'm sure, that old cast iron gear beats new fabricated steel each & every time.

Then there's the power characteristics of 3ph. I'm sure you know already, but the additional "power strokes" of 3 ph. makes them the definitive choice for driving high torque loads. A 1hp 3ph motor will utterly eat for breakfast a 1hp. single. The power inputs are the same, but the output is smoother, torquier and less stressed, which actually equates to less load and current demand (saving power utility costs).

I admire the engineering behind your proposed solution, but I wonder if it's going to be a bit of a minefield. With quality electric gear you just hit the star/delta starter and away you go.

A few years ago there was an article in an American woodworking magazine about an American woodworker who is (I think) Amish and therefore he couldn't use electricity. However it was apparently OK for him to use hydraulics!!
The article was about his considerable woodworking skills but there was also a lot about the conversion of ALL of his equipment from electric to hydraulic power. My memory is that everything was bought electric but all electrical drives and controls were replaced by hydraulics before use. I gather there was a petrol/diesel/biomass powered pump outside and all control was via valves. This gave him speed control, safety, lower noise (in the shop) and the great but little realised benefit that a stalled machine didn't burn out any electrics! This would be a great benefit to our bush mates who frequently suffer very low voltages and hence low power and stalled motors.
Before anyone asks about electric light, as an Amish he can't work after sunset ....I think I might tell my boss I'm Amish too?
my memory of the article was that the author's attitude changed from bemusement to surprise at the benefit of hydraulics.
fletty

As Fletty points out, the only way I would consider going hydraulic was if I was amish or way out bush with no other power supply, I think you would rack up considerable initial cost and ongoing costs with hydraulic, I'd suggest spend the money on 3ph and be done with it.


Pete