Water Brake

[Nick]

Does anyone have pictures of the inside of a Stuska water brake. I would like to build my own, but need more info. Heres what I'm thinking: And 11in impeller (rotor), 18 vanes on both sides, about 3/4in tall x 1/4 wide extending from the center out in a strait line (unlike a water pump that curve) The out side cases would have the same size and amount of vanes, with about 1/4in clearance from the impeller vanes. Two water inlets, one on each side of the unit. Two air in lets 180 degrees from the water inlets, water pump seals, double row roller bearings, and to be mounted like a Stuska in Pillow block bearings. also a valve to control the outlet, for water outlet temp control. The case would be made strong enough to control an explosion, in case the rotor failed. From what I have read it does not seem like theses thing are real high tech. Perhaps the torrid flow units are more advanced, but a Stuska, paddle wheel type seems easier to build. Any info would help.

Thanks Nick

[86rocco]

A friend of mine has a Stuska dyno, I'll see if he has any literature or pictures that might help you. Anyways, that sounds like an interesting project, I hope you'll document your progress so we can all follow along.

[RRBD]

I've built a few of these and will give you the quick low down:

The segments on the rotor will all be pie shaped, having the depth of each pocket tapered toward the outside diameter these segments should have radius'd corners, the fins are fine at 1/4" wide considering your are using 6061, if you are using cast alum. plate make them 3/8" wide. The back side of the rotor is exactly the same as the front. Have the rotor balanced professionally. The outside cases will have same basic segment profile. This shoud get you started. whatever you do, dont copy a stuska verbatim, as their single rotor design cannot grab a big inch motor in the lower rpm. A properly designed 11" absorber should be capable of grabbing 650 ft/lb at 2000 rpm.
Start out with 2" plate for the rotor, and 1/4" clearance is too much(this depends on rpm and required torque absorbtion

You are getting involved in a long and expensive journey, even if you own a machine shop. I have been using a modified 9" stuska for my small engines (Briggs) using a manual load control repeatability is hard to control as well as being hard on engines, especially if they get away from you on the dyno. An automated load control recieving Rpm feedback is almost a must to do any real testing. I'm working on a low buck set up as we speak, but am along way from having it "functional". I am not one to give away the farm, you'll need to do a little learning on your own so you know how to "tune your absorber" for your application. Don't worry about containing the rotor in event of failure; number one you wouldnt be able to and number two an absorber failure is an extremely rare ioccurance. The thing to worry about is the cv joint(s) you will use between the absorber and the engine, when these break there is no place to hide, so size them adequately and pony up the money to buy what you need instead of buying what you can afford.

Scott

[Nick]

Thanks for the reply. I have a few quick questions. Should the rotor be splined to fit the shaft, or can it be pressed fit and keyed? Why should the pie shaped cavities taper to the outside edge? Is 18 fins on each side correct? I have a small lathe and mill. I don't expect instant results from this project, it's more for fun just to see if I can.

I have done a lot of research on the net about dyno's, and it does seam they can be a pain to make work correctly, and good data accusition can easily cost 10 grand. That's not to mention the all the other issues that go along too, like sound control, water tanks, pumps, ventilation, temperature control, and load valves. Yet I still would like the challange. I don't want to run NASCAR, I just want something to play with in the winter when I can't race.

Maybe I should try to find some inexpensive plastic to practice on, just to see if I have the skills necessary to machine a rotor like this.

Thanks Nick

[RRBD]

Nick,

The best method of attaching the rotor to the shaft is by having a shaft with a flange and bolting the rotor directly to it. Broached keyways invite cracks.

Twelve pockets is very common.

You can make the pockets with no taper on the floor, I have made them both ways, but a tapered floor will offer increased torque absorbtion at a lower rpm.

I machined my first brake on a manual machine, here is a time saver for you: if your rotor is to be 11" in diameter use a plate that is 2" thick and 14-1/4" square. First cut the outside to 14" diameter and then cut the outside of your 11" dia. rotor and you will be left with a nice outer ring for your absorber(use a 1/2" endmill)

If I were you, I would go to a salvage yard that deals in large trucks and buy a torque converter from, say a 2 ton truck, the ones I am talking about are a bolt together design, which can easily be modified to suit your needs. Get the input shaft for the same converter. get rid of all the bearings inside and mount the rotor to a shaft and you will be in business. Just food for thought, works as well as any single rotor Stuska and is cheap.

For mufflers, you can use 55 gallon drums welded together with junk tires stacked inside, works very well and is cheap.

For rigorous testing you'll need atleast a 700 gallon water tank to keep everthing cool.(farm supply store)

It looks like I'm giving away the farm again.

Scott

[Nick]

Thanks for the info. I'll look into finding a torque converter. If that does not pan out maybe I'll try making a rotor. I looks like that aluminum 6061 plate would cost me $300 or more. I am getting a little ahead of myself with this project, I still have not finished my flow bench. I do have most of the parts now. The motors came Friday, one was a little dinged on the bottom, but it looks ok. ($10 Not worth sending back) I read all the posts, I think. Hopefully it will turn out good. It will be a Mercdog, with rubber stoppers instead of a rotating disc, removable back, portholes instead of sliding doors, a defector plate to keep from blasting the orifices, and I would like to find a way to bleed of air rather than closing the flow control to set the depression. Anyway thanks.

Nick

[jet]

A FEW YEARS AGO I REPAIRED A 2 ROTOR 516 GO POWER DYNO FOR A SPEED SHOP. I MADE A PATTERN FOR THE ROTORS AND HAD THEM CAST AND HEAT TREATED. THE ROTORS ARE FIXED TO THE MAINSHAFT WITH A WOODRUFF KEY PLUS THE SHAFT HAS A STRAIGHT KNURL/SPLINE. THE ROTORS ARE HEATED AND PRESSED ON WITH ABOUT 002''INTERFERENCE FIT.THE ROTOR HAS 12 FINS AS COMPARED TO THE STATOR WHICH HAS 11. I THOUGHT THAT WAS INTERESTING. CLEARENCE BETWEEN ROTOR AND STATOR WAS 060''. THE ROTOR DIAMETER WAS ABOUT 11'' BY APPROX 1 1/4'' WIDE AND HAS 12 APPROX 3/8 HOLES DRILLED THRU TO EQUALISE PRESSURE. [ I THINK] THE SHAFT WAS 431 STAINLESS STEEL.
HIGH SPEED 4 CYLINDER ENGINES WERE BLAMED FOR CAUSING THE INITIAL FAILURE OF THIS DYNO.
THE REPAIR WAS A SUCCESS