electric clutches

WHY

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Was just curious, for those using or thinking of using an electric clutch on a pre-rotor setup, has anyone done any research on these electric clutches that are use on the mower blades of large lawn mowers ???

Tony
 

Brent Drake

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The clutch would need to engage very slow for the first 80-90 RPM or it would be a catastrophe.
 

WHY

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Hi Brent

I think one of the PWM units like I am looking at for the starter could also be used to engage the clutch "lightly" and then bring it into full closeure after inertia was over come on the blades. That unit that I got from Kelly Controls was around $119, rated at 200 amps, so you could go a lot less power than that and less money !!

Tony
 

Vance

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My observations about electric clutches.

My observations about electric clutches.

We looked at the lawn mower electric clutches and they have more capacity than the air-conditioner electric clutches.

I feel the air conditioner electric clutch would manage enough torque to work.

We have a pressure blow off valve to prevent rough engagement of the prerotator.

This limits the amount of torque the hydraulic motor can produce.

If we find we need more torque we can modify the blow off valve to allow higher pressure and still limit the pressure on initial engagement.

We have not tested anything yet so this is all just presumption.

Thank you, Vance
 

Brent Drake

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A Twinstar had the soft start go bad. They took the blades and hooked them up direct to the starter with no soft start. When the start button was pushed, the entire gyro spun 180 degrees and the blade never turned. It's a wonder the mast never twisted. My soft start pulls over 700 amps for the first few seconds.
 

WHY

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Hi Vance

Your quite right about the "blow off?by-pass" valve as being adjustable, I was thinking along the lines of someone using a clutch on a flex cable or a telescoping splined shaft.

On the big machines I just think hydrualic is the prime option.

Tony
 

WHY

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Brent

THAT'S A BUNCH OF POWER !!!!!! did not think it could do that. What kind of soft start do you use and what motor ???

Tony
 

cbonnerup

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WHY not lawnmower clutch?

WHY not lawnmower clutch?

...has anyone done any research on these electric clutches that are use on the mower blades of large lawn mowers ???

Tony

Hi Tony,
FWIW, I am designing my pre-rotor based upon a traditional hyd system driven with a 'clutch-pump' as used on vehicle-equipped front loaders etc. I based my decision for using this clutch is that it is 'rated' at 90 ft-lbs which is a big safety margin. Preliminary numbers indicate I will need at least 10HP pump output to get a 'typical??' rotor up to 250 RPM in two minutes max. I assume a somewhat lossy system so will need at least 16 HP input from the soob. I also assumed that a lawn mower type clutch would be input power limited to ~15-30 HP...perhaps wrongly?? I can always downsize!

Hydraulic by-pass valve is a MUST and rated at max system pressure. Return to reservoir is possible.

I'm using the CA-320 here:
http://www.sunairusa.com/news/2012YorkCompressorClutches.pdf

These appear to be equivalent (bearings, dims, weight, coil) to the similar Warner $$ clutches with ratings available. Remember, this is my experiment; results may vary:)

And Brent, WOW 8400 Watts!! Glad that all that power was going somewhere! Would probably pay to see that on YouTube.
Chris
 

Brent Drake

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Brent

THAT'S A BUNCH OF POWER !!!!!! did not think it could do that. What kind of soft start do you use and what motor ???

Tony

The soft start came with Twinstar. The Stater is off a 1984 Cadillac it's used because of it's unique solenoid start plunger. It's used Here is how it works.
Starts off at 2 volts for approximately 10 seconds.
Jumps to 4 volts for about 6 seconds
Jumps to 6 volts for about 4 seconds
Then as it kicks out, at the same time a solenoid brings in the full battery voltage. Within another 10 seconds the battery is fully discharged. Approximately show around 10 volts. At this time your up to about 110 RPM.
 

RotoPlane

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The electric clutches that I've used didn't allow slipping….I don't believe any clutch will last long if they are used as the means for soft-start by ramping up their voltage.

I've decided to use a clutch on a hydraulic pressure compensated pump with two ramp-up pressure stages (perhaps three later on) for the soft start.
 

WHY

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Hi Ed and Chris

Sounds like you guys are on the same path, this will be very interesting to watch for comparisons of performance, costs, and design, good show :) :) .

Brent, did not know of such a starter design, very interesting..

Tony
 

cbonnerup

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Ed and Tony,
Just to be clear, I am not advocating energizing an electric clutch with anything else than the coil spec (12V in my case). Electric clutches can slip, but better have some ice handy. Fortunately they fail disengaged in case the pump seizes, but then you have other problems.

I like the idea of a two (or more) stage pressure relief.

Best,
Chris
 

WHY

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Brent

Can you tell me the brand of soft start that you are using. a Curtiss perhaps ?? Do you control the soft start with some form of electrical control potentiometer ??

Tony
 

RotoPlane

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.....I like the idea of a two (or more) stage pressure relief.

Just so I'm not being misunderstood Chris, I'm not using relief valves for the two stages. I'm using a variable displacement open circuit piston pump where its flow rate is controlled by the swashplate angle. The pressure compensator piston has the two (or three) stages that position the swashplate displacement for the needed oil flow.

Relief valves could be used as stages but they would require more HP usage and the relief oil flow would create a lot of extra heat.
 

WHY

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Ed

That pump you are using sound very very interesting, could be the start of something big. Is this unit very large, what might be the down side of using this pump (besides the costs :) )

Tony
 

WHY

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Ed

I had no idea such a pump design like this even existed. This is what I love about this forum, ideas can be hatched and developed at speeds and cost that large corporations can not even imagine in their wildest dreams, once a basic concept is developed THEN the corporations can grab the ball and run with it.

Tony
 

RotoPlane

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Ed

That pump you are using sound very very interesting, could be the start of something big. Is this unit very large, what might be the down side of using this pump (besides the costs :) )

Tony

I was into hydraulic equipment some 25 years ago. A bunch of companies I worked with back then are now out of business and I was shocked to find American components I use to purchase have now increased in price by almost 400%. Needless to say….I'm still reviewing suppliers for the best component value….but "cheaper" doesn't usually equate with best value, at least in hydraulics.

Eaton and others don't seem to make the "light" duty pumps now….so I'm still looking….
To answer your pump "down side" question Tony….cost has become a factor ~$1000 and so is weight with the Eaton MD PFC Series medium duty pumps…18 lb. The costs and weight will probably be acceptable for what I want my pre-rotator to do…but I doubt it will be able to compete with the standard ones used now.

These are some of the main components I have looked at:

Eaton hydraulic pressure compensated pump #70122 (medium duty - larger than I need).

http://www.eaton.com/Eaton/Products...ps/PistonOpenCircuit-Mobile/PCT_262172#tabs-1
Eaton-pressure-compensated-70122-piston-pumps.pdf (file too large for forum).

Ogura electric clutch
http://www.ogura-clutch.com/products/mobile/

White roller-stator motor (used these on my 4-wheel drive lawn tractor I made - still working find after ~25 years)
http://www.whitedriveproducts.com/WR.html
 

WHY

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Hi Ed

The only hydrualic pump company I ever had any knowledge of was the Vickers Company, I did a lot of two-way radio service for them, they used two-way radios on the fork trucks in the plant.

Tony
 

WHY

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Ed

I see it is now Eaton/Vickers :) Does the pump have to be new?? I read where a lot of the tech came from Cessna pumps ????? Are the PVE and PVH to expensive or to big ??

Tony
 

RotoPlane

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The MD PFC Series (70122) is Eaton….the PV Series is Vickers. The Vickers PV is about $400 more expensive and yet its max rpm is 1800….where the Eaton is 2500 rpm. The $1000 Eaton price is retail by the way. I am still hoping to find a smaller displacement one….

If one keeps a good oil clean, the hydraulic components will last a long time, so if you know what you're getting, used should work fine.
 
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