electric clutches

WHY

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Ed

Bosch makes a world of pumps ??

Tony
 

Brent Drake

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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

Not sure of the brand. I know it was made in Tenn. It's done with transistors. All Twinstars have it. Never seen one fail. Built like a tank.
 

500e

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a lot more now
http://www.pfp1.com/c/Sauer-Sundstrand/Sauer+Sundstrand.html.
What is the efficiency lose in modern hydraulics? 10% ?
Higher pressures less lose or lower pressure more volume pumped schools of thought Vary
Alloy parts usually have cost premium.
Used a swash-plate pump on a boat out-drive ran diesel at max TQ & used pump to vary speed could also set diesel rpm to most fuel efficient RPM & adjust pump for max Knots
 

WHY

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Ed

Sure nice to have someone with an extensive back ground in hydrualics here on the forum. This way from time to time I can ask some dumb questions and know I will get a an informed answer :)

Tony
 

Vance

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My opinion.

My opinion.

I am not a hydraulics expert and have not yet demonstrated my pre-rotator fantasy.

In my opinion a pump/motor that weighs less than four pounds, can pump 10 horsepower and costs less than $200 would be a good choice for a hydraulic prerotator.

http://www.surpluscenter.com/item.asp?item=9-4769&catname=hydraulic

This particular pump can spin up to 3,000 rpm as a pump and 5,000 as a motor. There are several different displacement pumps with the same body so in case the mechanical ratios aren’t correct they can be substituted without a lot of work.

I am a satisfied customer of the Surplus Center.

Thank you, Vance
 

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RotoPlane

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Ed

Sure nice to have someone with an extensive back ground in hydrualics here on the forum. This way from time to time I can ask some dumb questions and know I will get a an informed answer :)

Tony

I wish you good luck on that one Tony ;).

If a 200 pre-rotator rpm is acceptable, then I agree with Vance above. With the blades lifting at 200 rpm, a 22' rotors drag may require about 4.4 hp max. I don't know if this will help anyone but this is how I would figure the required pump and motor for this job, as an example.

Using those noted gerotor Parker pump and motors, I would use the largest 2000 psi motor (.58 cu.in./rev) and set the system relief valve to 2000 psi, to allow the highest continuous torque available.

Using the standard rotorhead gear set; say the P.D. (pitch diameter) is 12" and 1.5", so the motor must rotate at (200 x 12) / 1.5 = 1600 rpm.

The motor torque is (.58 x 2000) / 6.2832 = 184.62 in.lb. and the hp is (184.62 x 1600) / 63025 = 4.69 HP….so this motor should drive the rotor at 200 rpm.

If this gerotor motor efficiency is 90% then it will require a pump oil flow of (1600 x .58 x 1.10) / 231 = 4.42 gpm. The pump efficiency would be the same, so the pump rpm must give a flow of 4.42 x 1.10 = 4.86 gpm or 4.86 x 231 = 1122.66 cu.in.

Using the same motor as a pump, the needed pump rpm would be 1122.66 / .58 = 1935.62 rpm.
The next smaller pump (.45 cu.in./rev) would need 1122.66 / .45 = 2494.80 rpm.

I would choose the .58 cu.in./rev pump with 1 to 1 pulleys from the prop shaft to the pump clutch or belt tightener unit and increase engine rpm from idle up to 2000 rpm. One could use a smaller displacement pump if using a step-up pulley drive, but I don't like them ;).

This hydraulic circuit may need a dump valve or an accumulator for a soft start. It also should have an oil tank, an oil filter and possibly an oil cooler if the system will run long enough to heat up. And a good grade of anti-wear "hydraulic" oil.
 

WHY

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Ok Ed, ---- get ready, here comes one of my "dumb" questions. Now to start with I know there has to be a good reason this is not done, but being ignorant on hydrualics, it looks like a possiblility to me :)

What would be the problem in putting a manually controled bypass valve in the pump output that would start out at say 80% by-pass on engagement and then you would slowly move it to 0 % by-pass as inertia is overcome. Would it be foaming of the oil, heat, or just not to bright ?? :)

Tony
 

Vance

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Just wondering.

Just wondering.

Hello Ed,

Why would you use the .58 cubic inch motor/pump instead of the .7 cubic inch pump that weighs the same as the .58 cubic inch pump?

Why would you limit the motor speed to 2,000 rpm?


Hello Tony,

Why would you use a manual bypass instead of a pressure blow off bypass?

Thank you, Vance
 

WHY

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Hi Vance

Just an idea at a form of "soft start", but there has got to be a reason it is not done.

Tony
 

Vance

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Just wondering.

Just wondering.

Hello Tony,

What would the advantage of a manual bypass soft start compared to a pressure blow off bypass soft start?

In my opinion the pressure blow off bypass soft start would be simpler, lighter and require less pilot input.

Thank you, Vance
 

bosca

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Hi Tony,
As per our recent conversation I also have been wondering why the manual bipass has not been used.
In the agricultural sector we use hydralics to power the fan to sow our crops.We use the manual control (as you touched upon) to set the fan speed.However if the control is set on 0 or 1 for example the fan does not move.If we progress up the scale the fan speed increases to max speed.It is a simple set up without too much weight increase.
Cheers Kym.
 
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L_Butler

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Manual bypass

Manual bypass

Tony,
I use a manual bypass on my hydraulic prerotator and am very happy with it. It allows me to adjust the acceleration rate of the blades based on conditions and to hold at any setting if something distracting comes up. There have been several instances where I have been waiting 2nd or 3rd in line to take off and I don't want to stop rotation completely, but I don't want to run at high speed either. The throttling ability of the manual control fits my needs better than a fixed speed unit.

The only drawback is that holding at a constant speed for an extended period builds up heat quickly and a cooler is required. I use a simple oil cooler from J. C Whitney and it works fine. Model 1JA502360, its about 6"x11".

I also am a fan of Surplus Center. They have a great selection and very good prices for hydraulic equipment.

I use an electric clutch from a Ford A/C compressor to shut off the hydraulic pump once underway. It involved making an adapter coupling to match the shafts, but that was straightforward. It's been 4 years and is still running.

Larry
 
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RotoPlane

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Tony….nothing wrong with using a high pressure ball valve, gate valve, etc. for the soft start…full open, start pump and then gradually close it and bring up the engine rpm. I called it a dump valve.

Vance….the .7 cu.in. pump/motor is only rated for 1500 psi continuous and the relief is set to 2000 psi.
You would reach 200 rotor rpm at just under 2000 engine rpm so there is no reason to run the engine higher until the pre-rotator is shutdown.
You could use another relief valve set for a pressure low enough to get a soft start, but you would still need to add a shut off valve (manual or solenoid) to close that relief line so you could finish the pre-rotation.
 

Jason O

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vairable displacement (swash plate) pump

vairable displacement (swash plate) pump

Hello All,
I dont know much about hydraulics, but I always dreamed of making a pre rotator with a vairable displacement (swash plate) pump. These pumps can be running and not pump any oil, it is not being bypassed, it is just not displacing any oil. With a pump like this I would envision controlling it with a pressure sensor controlling the swash plate not a bypass and you would control the amount of pressure in the system by electronicly telling the pressure sensor what pressure you want the system at. It seems to me that with this kind of system you could leave the pre rotator engaged for take off. When you went to full throttle, the pump would not be working super hard to pump and bypass all that oil, the pump would just lower its displacement to keep the system at a constant pressure. In my uneducated brain, a system like this seems better and more self regulating than haveing a pump that vaires flow with rpm and having to bypass all that oil when you go to high engine RPM.

FWIW
Jason
 

RotoPlane

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In my opinion you've got the right idea Jason….it is the Cadillac way to go.

We started talking about pressure compensated pumps back in post 14. The main problem with what is available now is cost, larger than needed displacement and weight….other than that….Cadillac ;).
 

Vance

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Goals for prerotator.

Goals for prerotator.

Vance….the .7 cu.in. pump/motor is only rated for 1500 psi continuous and the relief is set to 2000 psi.
You would reach 200 rotor rpm at just under 2000 engine rpm so there is no reason to run the engine higher until the pre-rotator is shutdown.
You could use another relief valve set for a pressure low enough to get a soft start, but you would still need to add a shut off valve (manual or solenoid) to close that relief line so you could finish the pre-rotation.

Hello Ed,

In my limited experience with hydraulic motors and pumps we have used a low pressure bypass that is staged so that it closes when it is no longer needed without any additional valves or control input.

What is your reason for preferring the higher pressure of the small pump?

I feel my focus on prerotator design is about weight, cost and simplicity.

My compromises are centered on the obtaining the maximum prerotation rotor speed with the minimum weight and cost.

I will be starting a set of 30 foot 8.5 inch chord or larger Sport Copter Blades.

I typically roll out past the hold short line with 1,500 engine rpm and do not advance the throttle until I see 185 rotor rpm. I would prefer that I could reach that 185 rotor rpm with the engine at 1,500 rpm so I am not riding the brakes to keep from using up runway or flapping the blades. This seems like a reasonable goal to me.

I am still not able to imagine the allure of a speed control for the prerotator.

I am sure I have a lot to learn and may speak with more authority when my ideas for a prerotator have been tested.

I find the electric pre-rotator of The Predator leaves a lot to be desired and I have enjoyed the hydraulic prerotator of the Dominator.

When I was training in a modified RAF and a SparrowHawk the most likely challenge to gyroplane operation was the prerotator. They both used a cable engaged clutch and a flexible shaft. The clutch gave us a lot of trouble. I suspect the abuse from the students exacerbated any weakness in the design.

Thank you, Vance
 

StanFoster

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Vance- I have mentioned several times that on each of my 4 gyros that I have flown.....there has been much more of my time working on just their pre-rotators than my whole Helicycle to date.

If I were to ever have another gyro....I would definitely try some kind of hydraulic like Ernies.


Stan
 

RotoPlane

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Vance….All I did was take the pump/motor that you referenced and used them as an example for use with a 22' rotor. They will work fine for 200 rrpm as stated.

They will not work well with your 30' rotor so you will indeed need a larger pump and motor combination to deal with the greater torque requirement.

I mentioned the pressure compensated pump system for my pre-rotator zero rotor thrust requirements….three stages for 150, 350 and occasionally 450 rotor rpm. This is not something that is needed for the normal gyroplane pre-rotations.
 

Vance

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Our Goals defined.

Our Goals defined.

Our experience suggests we should be able to get 10 horsepower transferred to the rotor using the .7 cubic inch pump and motor.

We feel 10 horsepower will accelerate the30 foot 8.5 inch chord rotor to 150 rpm.

We don’t have a desire for more than that.

We would like the system to weigh less than 19 pounds including the lines, fluid, electric clutch, bendix and soft start.

We expect to learn more when we try it.

We are also looking a brushless electric motor to save weight or a more traditional flexible shaft and clutch.

We also like a clutch, right angle gearbox and sliding shaft.

Each system has its pluses and minuses.

We have the parts to make the hydraulic system so that is probably what we will try first.

We will overdrive the pump and drive the clutch with a V belt.

Mariah Gale is currently experiencing a funding interruption so there is no telling when we will test.

Thank you, Vance
 
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