mr_matt

My Feedback: (10)

Hello,

Does anyone know of a source for hydraulically actuated brakes, either drum or o-ring type?

Thanks in advance,

Gordon Mc

My Feedback: (11)

The brakes on the new PST Panther are hydraulic ... dunno if you could use or adapt those. See the guys at Great Northern Models for details if you wish.

Gordon

Terry Holston

My Feedback: (1)

And................they DO work............No air needed or wanted in the system!

hmjets

Eurokit?

Terry Holston

My Feedback: (1)

NO.....PST!

747drvr

My Feedback: (5)

Hi Terry,

How do they work ? I was thinking of using a strong servo and a door cylinder to provide the hydraulic pressure . Since fluid is not compressible and there would be very little movement of the plunger , I would use a spring between the servo and the cylinder so the servo would be able to move its full range . Hopefully this would allow smooth proportional control . I was wondering what to use for hydraulic fluid since regular brake fluid would not be needed or desired.

Marc

Gordon Mc

My Feedback: (11)

The PST instructions suggest using either jack oil or regular household 3-in-1 oil.

hmjets

HI matt , eurokit north america sells hyidraulic brakes.more details- http://www.eurokit.us

747drvr

My Feedback: (5)

My thoughts as well . I was even thinking water... So how do the PST brakes work ?

c/f

My Feedback: (1)

FWIW,

If I used a hydraulic system I would be using Automatic transmission fluid.

Gordon Mc

My Feedback: (11)

Terry or David Gladwin, could probably answer this best since they already have the gear in hand. I have so far only read the instrcutions that Terry kindly emailed me. The hydraulics in this case are not using any fancy electric pump & ECU etc as per the much more complicated hydraulics of a rather famous / infamous Mig 29 kit - instead it's a much simpler mechanism that just relies on a servo activating a plunger in a master cylinder - similar to what you seem to be suggesting in converting an air cylinder. On the wheel side, a pair of fairly wide "pistons" push sideways against the inside if the wheel. It's not clear to me whether this is a purely metal on metal contact, or if there rubber or some other lining (like helicopter clutch material) at the points where friction is applied.

Sounds kinda interesting. One slight concern that I have with something like this is that if there is any leak you could have a real mess to clean out of the guts of the aircraft.

EASYTIGER

My Feedback: (119)

Totally fascinating. Has anybody tried converting conventional o-ring brakes to hydraulic operation using an air cylinder?

Miniflyer

Hy ET.
We are running O-ring types on hydraulic and it works fine...for a while. The O-rings do not seal 100% when they are extending/retracting, so over longer cycle times they bleed oil and fill with air. If you do not mind venting them every few weeks then its a perfect and cheap hydraulic setup. My friend is working on an automatic filler....
We do not use air cylinders as masters, but insuline styringes from the doctors office. They seal great and cost next to nothing....plus you can mount Festo fittings in their tips without much effort.
We are working on hydraulic disc brakes similar to those on motorcycles, but our to-do list is long and the project has not gotten beyond having discs laser-cut....

Bestt regards
Hank

EASYTIGER

My Feedback: (119)

Fantastico!
What kind of oil is safe with the O-rings?
What kind of servo and throw do you need to drive the insulin syringe?

Kelly W

My Feedback: (2)

Here's a photo of the brake hub in my Panther kit. Its an early prototype, but I don't think the design changes for the production version. The only difference I've seen from mine vs that of the ones handed out to customers is the machining finish looks better on the new ones. I have not used them yet...

The brakes are really pretty simple... The 3 pistons push against the adjacent block, which has an over sized hole in it to allow relative movement between it and the main hub piece. There's a small chunk of brake pad material on each end. The 1st thing I noticed was a lack of a return spring but according to PST and the few guys that have used them its not a concern. Minor contact doesn't seem to cause much rotational drag.

I don't know that I would ever trust a hydraulic drive on conventional o-ring brakes, since the o-ring in a groove won't give you anywhere near the reliable seal that a set of machined pistons would. (particularly once it gets dirty) If anything it may work, but your contact point would probably change over time.

Kelly

DocYates

My Feedback: (102)

I have these brakes from PST and they work great. I have never had a leak in the system, and they never need air. After I bled the lines and hooked them up, they have worked fine every time. They are extremely smooth and you do not get jerky movement. Like previously stated they are a simple cylinder (syringe type with plunger) which is actuated by a strong servo. Therefore they are proportional, the harder you mask it, the more pressure to the drum.
TOmmy

Miniflyer

The o-rings will live up to most oils...if you are not sure, use Viton rings (they survive anything), or do a test by dumping them in a small can of oil for a few days. Weapons oil works very good and is not so agressive. We have also run it with water and a touch of household cleaners with great success. Do a little experimenting to find what works for you.

As to throws: inside the 4mm styringe we need a bit less than 1" of travel. Servo can be anything starting at 50Ncm force. We like to use Hitec digitals, because there is one brake circuit per wing, and the Hitecs can easily be programmed.
Best regards
Hank

747drvr

My Feedback: (5)

I thought my idea could work ! I'm glad to see that someone has proven me correct .

Hank, how can the plunger move 1 inch if the fluid can not compress ? I thought that there would be almost no movement at the syringe but more just a pressure that can ramp up with the spring between the servo and the plunger .

Marc

747drvr

My Feedback: (5)

I would love to see what the actuater looks like . Is there a resevoir ? I wonder what can be used as pad material ? I've just been playing with my CNC mill today and see that this would be a cool project !

Marc

Kelly W

My Feedback: (2)

Marc, You have a CNC MILL NOW???!!!!?? You've been busy!

I might have some diffuser stuff for you tot work on if you’re interested.

I'll see if I can dig out the actuator later tonight. Its all packed away with the rest of the kit. Many project on the go, the most important of which is my 2nd kid due in January!

Kelly

Miniflyer

Marc, the 1" movement results from the o-ring expanding outward, thus making more "room" to be filled with liquid. When pressure is released, the o-ring contracts and pushes all the liquid back into the styringe. Advantage is that it is a lot less sensible than the other types....you are pumping a lot of volume for only a small change in braking power, thus are very very precice controlling it (in fact my friend has his F-4 set up so he can steer only with differential braking).
As i said, they do ingest a lot of air over time. So i guess for every up there is a down :-). That is also why we are working on disc brakes....they should be absolutely sealed

Best regards
Hank

747drvr

My Feedback: (5)

Hey Kelly,

Congrats on the impending bambino ! Regarding the mill . Don't get too excited ! It's only a very small Taig unit I converted a while back . I'm not very good at the programming aspect and haven't done too much with it . I DID make a cool little CF motor mount for a foamy today

Hank,

Thanks for the input . I guess the O rings must be fairly big and the syringes small . Any chance of a photo of your set up if you have time ?

Marc

DocYates

My Feedback: (102)

Sort of looks like this. Cylinder is only about 1.5 inches long, and about 1/2 to 3/4 inch in diameter....
Tommy

Miniflyer

Sure marc, i'll get on it this weekend when i get back home. The o-rings have an outside diameter of 26-30mm, and a tubing diameter of 2,5-3mm depending on wheels/hubs. The styringe has a 4mm inside diameter...to give you a rough idea of dimensions.

Best regards
Hank

747drvr

My Feedback: (5)

Thanks Guys !

I was wondering if the PST system has a special way of bleeding the air ?

Marc