Jgwright

I have just completed installation of the hydraulic retracts in my Boulton Paul P111. I always had problems in getting the wheels to go up and rolling inverted to get the retracts to go up always looks a bit lame.

I have installed the Magom (Magomhrc.com) combined pump and tank as well as their rotary valve. Their products seem very good so far. The pump uses a brushless outrunner motor. I have a 20 amp Hobbywing ESC which happens to have a BEC. I have disabled this by removing the red power line to the receiver. I am running a 3 cell A123 battery 1100 MAh. The ESC needs to be armed and set to a speed. I have a 3 position switch on one channel that has 0, 50% and 100% When the battery is connected the switch is toggled to arm the ESC. I have tried running at the 50% speed but that i9s a little low power. The 3 cell A123 pack at full power seems fine.

The other items are a Festo non return valve and a compressor pressure switch that I bought on Ebay. The tubing is high pressure nylon not normal Polyurethane which cannot take the pressure. I selected a valve that works between 170 and 200 psi. The control panel is as small as I could conveniently make it and fitted space I had available. (150mm X80mm). The panel including the battery weighs just 500 grams or about 1 lb. The model is over the Large Model Weight limits so the weight is really not a concern. The fluid is LHM + which is used for car suspension systems.

I used Festo connectors throughout. It must be a cost effective solution now that these parts are available at modest cost.

For those worried about bleeding the system, I ran the system with a loop first until it was free of air as in the photos. I then fitted the lines and joined the ends at each retract in turn. This enabled me to fill the lines with fluid. I then manually operated one leg at a time filling the cylinder that was opening as the leg was lifted. the 2 lines were connected and the system run a few times. I then checked at all the retracts and released the feast fittings if air was present in the line and ran the pump until they were clear. Eventually all lines were completely free of air.

I chose to run at between 170 and 200 psi. This means that the system is pressurised to 200 and as the pressure falls below 170 the pump is activated and pumps it back up to 200. You do have to make sure that fingers are out of the way as there is quite a lot of force!




https://www.youtube.com/watch?v=4tkiZljrP3E&feature=youtu.be

jofunk

Hi John,

I couldn't view the video. It says it is private......... Could you put the pressure switch between the battery and the pump and eliminate the ESC? I am looking to eventually build a hydraulic system for a set of gear my friend made. Im just not sure about the best way to go about it.


Thanks,
Joe

roydefiant

looks like magomhrc.com ?
Curious what was all up cost for this system?

Jgwright

Joe

The video is not private I just checked again. You must have a problem with your computer settings.

The pump is brushless motor so you cannot run it without an Electronic speed controller. If you had a brushed pump then you could switch the motor on and off via the pressure switch. However, you would need an electronic switch, like a Battle switch, capable of about 10 - 15 amps. The pressure switch would not handle the current. The cost of the Battle switch is the same as the speed controller so overall costs are much the same for either system.

I have made up several hydraulic systems to check on how they work and the current one is easily the simplest and most compact. If you are to make one up best just to copy what I have done using the same components and configuration and try it. It will work as several of my friends can confirm.

Roy

Yes sorry the Magom site is Magomhrc.com. The cost of the main components (pump/tank valve pressure switch and ESC) is 170 dollars. You really need to price up all the parts you need as the Festo fittings can quickly add up. I reckon if you allow say 200 dollars you will not be far off. You may have import duties to pay.

HarryC

My Feedback: (1)

It says "private" for me too John, and won't play.
This video is private.

Jgwright

Harry and Joe. I think I found the problem I didn't click on the publish button. It works ok on my wife's computer without a membership so I guess should be working for you now. Please let me know if it is still a problem.

John

HarryC

My Feedback: (1)

That fixed it John, thanks

olnico

Thanks for sharing this, mate.

I see one possible risk of failure with your setup. The hydraulic lines are close to the engine. 170-200 PSI is a lot of pressure. The best lines made of PU ( freelin Wade ) would actually blow out at 250 PSI at 72F and 200 PSI at 100F.

I am not sure what lines you use right now as the pictures/ video are not very clear, but I would go with teflon lines under these conditions.
Cheers.
Oli.

Jgwright

Oli

Yes I was going to put a baffle between the engine and the hydraulics, just in case. The lines are nylon. It was the only spare room I had available. With the plane actually flying in the air it will be cool as the air is brought into the exhaust it is just the period before takeoff or taxiing that might have a problem. The retracts have locks on them so if there was a failure the retracts would just stay down. The tank is a small size which I initially thought would be a disadvantage but now I see it as a benefit as it would not discharge much fluid into the fuselage.

John

jofunk

The video works for me now..........It looks like you did your homework and designed a nice system. The gear I am trying to operate work up and down on 50 psi of air. Are there switches available with lower cut in and cut out pressures?

sidgates

My Feedback: (2)

John,
Very interesting project. Thanks for sharing.
SidGates

mick15

Your system could be configured to work in a different way John particularly in the light of jo's question.

Because the pump has an adjustable pressure reliefe valve the pressure switch can be eliminated and the pump delivery can be timed in the transmitter. You would obviously have to assign the speed controller to another channel.

m

Jgwright

Yes you can use a compressor switch with a lower value I also have one which operates between 80 and 120 psi.

John

Jgwright

Mick

yes I am using a separate channel to arm the ESC. I can turn it down to 0% after the retracts operate using servo slow but I preferred to have the system fully pressurised through the flight. The pressure relief valve is a simple non adjustable one that is much cheaper than to one I was using some time ago, they only cost about 4 pounds.

John

olnico

I have aero certified high pressure grade Teflon lines good to go up to 450 PSI at 72F and 300 PSI at 100F.
it's not too expensive at 4 USD per meter.
We use these on UAV hydraulic gear. 200-250 PSI.